1. |
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2. |
- Lind, Lars, et al.
(författare)
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Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)
- 2021
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Ingår i: eLife. - : eLife Sciences Publications Ltd. - 2050-084X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions.
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3. |
- Mishra, A, et al.
(författare)
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Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
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Tidskriftsartikel (refereegranskat)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
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4. |
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5. |
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6. |
- Acharya, B. S., et al.
(författare)
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Introducing the CTA concept
- 2013
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Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
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7. |
- Mishra, A., et al.
(författare)
-
Stroke genetics informs drug discovery and risk prediction across ancestries
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 611, s. 115-123
-
Tidskriftsartikel (refereegranskat)abstract
- Previous genome-wide association studies (GWASs) of stroke - the second leading cause of death worldwide - were conducted predominantly in populations of European ancestry(1,2). Here, in cross-ancestry GWAS meta-analyses of 110,182 patients who have had a stroke (five ancestries, 33% non-European) and 1,503,898 control individuals, we identify association signals for stroke and its subtypes at 89 (61 new) independent loci: 60 in primary inverse-variance-weighted analyses and 29 in secondary meta-regression and multitrait analyses. On the basis of internal cross-ancestry validation and an independent follow-up in 89,084 additional cases of stroke (30% non-European) and 1,013,843 control individuals, 87% of the primary stroke risk loci and 60% of the secondary stroke risk loci were replicated (P < 0.05). Effect sizes were highly correlated across ancestries. Cross-ancestry fine-mapping, in silico mutagenesis analysis(3), and transcriptome-wide and proteome-wide association analyses revealed putative causal genes (such as SH3PXD2A and FURIN) and variants (such as at GRK5 and NOS3). Using a three-pronged approach(4), we provide genetic evidence for putative drug effects, highlighting F11, KLKB1, PROC, GP1BA, LAMC2 and VCAM1 as possible targets, with drugs already under investigation for stroke for F11 and PROC. A polygenic score integrating cross-ancestry and ancestry-specific stroke GWASs with vascular-risk factor GWASs (integrative polygenic scores) strongly predicted ischaemic stroke in populations of European, East Asian and African ancestry(5). Stroke genetic risk scores were predictive of ischaemic stroke independent of clinical risk factors in 52,600 clinical-trial participants with cardiometabolic disease. Our results provide insights to inform biology, reveal potential drug targets and derive genetic risk prediction tools across ancestries.
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8. |
- Taddei, C, et al.
(författare)
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Repositioning of the global epicentre of non-optimal cholesterol
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 582:7810, s. 73-
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Tidskriftsartikel (refereegranskat)abstract
- High blood cholesterol is typically considered a feature of wealthy western countries1,2. However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world3 and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health4,5. However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol—which is a marker of cardiovascular risk—changed from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95% credible interval 3.7 million–4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world.
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9. |
- Adare, A., et al.
(författare)
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Measurement of K-S(0) and K*(0) in p plus p, d plus Au, and Cu plus Cu collisions at root s(NN)=200 GeV
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:5
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Tidskriftsartikel (refereegranskat)abstract
- The PHENIX experiment at the Relativistic Heavy Ion Collider has performed a systematic study of K-S(0) and K*(0) meson production at midrapidity in p + p, d + Au, and Cu + Cu collisions at root s(NN) = 200 GeV. The K-S(0) and K*(0) mesons are reconstructed via their K-S(0) -> pi(0)(-> gamma gamma) pi(0)(-> gamma gamma) and K*(0) -> K-+/-pi(-/+) decay modes, respectively. The measured transverse-momentum spectra are used to determine the nuclear modification factor of K-S(0) and K*(0) mesons in d + Au and Cu + Cu collisions at different centralities. In the d + Au collisions, the nuclear modification factor of K-S(0) and K*(0) mesons is almost constant as a function of transverse momentum and is consistent with unity, showing that cold-nuclear-matter effects do not play a significant role in the measured kinematic range. In Cu + Cu collisions, within the uncertainties no nuclear modification is registered in peripheral collisions. In central collisions, both mesons show suppression relative to the expectations from the p + p yield scaled by the number of binary nucleon-nucleon collisions in the Cu + Cu system. In the p(T) range 2-5 GeV/c, the strange mesons (K-S(0), K*(0)) similarly to the phi meson with hidden strangeness, showan intermediate suppression between the more suppressed light quark mesons (pi(0)) and the nonsuppressed baryons (p, (p) over bar). At higher transverse momentum, p(T) > 5 GeV/c, production of all particles is similarly suppressed by a factor of approximate to 2.
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10. |
- Adare, A., et al.
(författare)
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Measurements of Elliptic and Triangular Flow in High-Multiplicity He-3 + Au Collisions at root s(NN)=200 GeV
- 2015
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Ingår i: Physical Review Letters. - 1079-7114. ; 115:14
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Tidskriftsartikel (refereegranskat)abstract
- We present the first measurement of elliptic (v(2)) and triangular (v(3)) flow in high-multiplicity He-3 + Au collisions at root s(NN) = 200 GeV. Two-particle correlations, where the particles have a large separation in pseudorapidity, are compared in He-3 + Au and in p + p collisions and indicate that collective effects dominate the second and third Fourier components for the correlations observed in the He-3 + Au system. The collective behavior is quantified in terms of elliptic v(2) and triangular v(3) anisotropy coefficients measured with respect to their corresponding event planes. The v(2) values are comparable to those previously measured in d + Au collisions at the same nucleon-nucleon center-of-mass energy. Comparisons with various theoretical predictions are made, including to models where the hot spots created by the impact of the three He-3 nucleons on the Au nucleus expand hydrodynamically to generate the triangular flow. The agreement of these models with data may indicate the formation of low-viscosity quark-gluon plasma even in these small collision systems.
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11. |
- Adare, A., et al.
(författare)
-
Nuclear modification factors of phi mesons in d plus Au, Cu plus Cu, and Au plus Au collisions at root s(NN)=200 GeV
- 2011
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 83:2
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Tidskriftsartikel (refereegranskat)abstract
- The PHENIX experiment at the Relativistic Heavy Ion Collider has performed systematic measurements of phi meson production in the K+K- decay channel at midrapidity in p + p, d + Au, Cu + Cu, and Au + Au collisions at root s(NN) = 200 GeV. Results are presented on the phi invariant yield and the nuclear modification factor R-AA for Au + Au and Cu + Cu, and R-dA for d + Au collisions, studied as a function of transverse momentum (1 < p(T) < 7 GeV/c) and centrality. In central and midcentral Au + Au collisions, the R-AA of phi exhibits a suppression relative to expectations from binary scaled p + p results. The amount of suppression is smaller than that of the pi(0) and the. in the intermediate p(T) range (2-5 GeV/c), whereas, at higher p(T), the phi, pi(0), and. show similar suppression. The baryon (proton and antiproton) excess observed in central Au + Au collisions at intermediate p(T) is not observed for the phi meson despite the similar masses of the proton and the phi. This suggests that the excess is linked to the number of valence quarks in the hadron rather than its mass. The difference gradually disappears with decreasing centrality, and, for peripheral collisions, the R-AA values for both particle species are consistent with binary scaling. Cu + Cu collisions show the same yield and suppression as Au + Au collisions for the same number of N-part. The R-dA of phi shows no evidence for cold nuclear effects within uncertainties.
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12. |
- Adare, A., et al.
(författare)
-
Production of omega mesons in p plus p, d plus Au, Cu plus Cu, and Au plus Au collisions at root s(NN)=200 GeV
- 2011
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 84:4
-
Tidskriftsartikel (refereegranskat)abstract
- The PHENIX experiment at the Relativistic Heavy Ion Collider has measured omega meson production via leptonic and hadronic decay channels in p + p, d + Au, Cu+ Cu, and Au + Au collisions at root s(NN) = 200 GeV. The invariant transverse momentum spectra measured in different decay modes give consistent results. Measurements in the hadronic decay channel in Cu Cu and Au + Au collisions show that. production has a suppression pattern at high transverse momentum, similar to that of pi(0) and eta in central collisions, but no suppression is observed in peripheral collisions. The nuclear modification factors, R-AA, are consistent in Cu + Cu and Au + Au collisions at similar numbers of participant nucleons.
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13. |
- Adare, A., et al.
(författare)
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Search for dark photons from neutral meson decays in p plus p and d plus Au collisions at root s(NN)=200 GeV
- 2015
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:3
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Tidskriftsartikel (refereegranskat)abstract
- The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment (g - 2)mu deviates from SM calculations by 3.6 sigma. Several theoretical models attribute this to the existence of a "dark photon," an additional U(1) gauge boson, which is weakly coupled to ordinary photons. The PHENIX experiment at the Relativistic Heavy Ion Collider has searched for a dark photon, U, in pi(0), eta -> gamma e(+)e(-) decays and obtained upper limits of O(2 x 10(-6)) on U-gamma mixing at 90% C.L. for the mass range 30 < m(U) < 90 MeV/c(2). Combined with other experimental limits, the remaining region in the U-gamma mixing parameter space that can explain the (g - 2)(mu) deviation from its SM value is nearly completely excluded at the 90% confidence level, with only a small region of 29 < m(U) < 32 MeV/c(2) remaining.
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14. |
- Adare, A., et al.
(författare)
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Systematic study of charged-pion and kaon femtoscopy in Au plus Au collisions at root s(NN)=200 GeV
- 2015
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:3
-
Tidskriftsartikel (refereegranskat)abstract
- We present a systematic study of charged-pion and kaon interferometry in Au + Au collisions at root s(NN) = 200 GeV. The kaon mean source radii are found to be larger than pion radii in the outward and longitudinal directions for the same transverse mass; this difference increases for more central collisions. The azimuthal-angle dependence of the radii was measured with respect to the second-order event plane and similar oscillations of the source radii were found for pions and kaons. Hydrodynamic models qualitatively describe the similar oscillations of the mean source radii for pions and kaons, but they do not fully describe the transverse-mass dependence of the oscillations.
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15. |
- Adare, A., et al.
(författare)
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Inclusive cross section and double-helicity asymmetry for pi(0) production at midrapidity in p plus p collisions at root s=510 GeV
- 2016
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Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 93:1
-
Tidskriftsartikel (refereegranskat)abstract
- PHENIX measurements are presented for the cross section and double-helicity asymmetry (A(LL)) in inclusive pi(0) production at midrapidity from p + p collisions at root s = 510 GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantum-chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The pi(0)A(LL) results follow an increasingly positive asymmetry trend with p(T) and root s with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on pi(0) and jet A(LL) and suggested a positive contribution of gluon polarization to the spin of the proton Delta G for the gluon momentum fraction range x > 0.05. The data presented here extend to a currently unexplored region, down to x similar to 0.01, and thus provide additional constraints on the value of Delta G.
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16. |
- Adare, A., et al.
(författare)
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Measurement of higher cumulants of net-charge multiplicity distributions in Au plus Au collisions at root s(NN)=7.7-200 GeV
- 2016
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 93:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report the measurement of cumulants (C-n,n = 1, ..., 4) of the net-charge distributions measured within pseudorapidity (vertical bar eta vertical bar < 0.35) in Au + Au collisions at root s(NN) = 7.7-200 GeV with the PHENIX experiment at the Relativistic Heavy Ion Collider. The ratios of cumulants (e.g., C-1/C-2, C-3/C-1) of the net-charge distributions, which can be related to volume independent susceptibility ratios, are studied as a function of centrality and energy. These quantities are important to understand the quantum-chromodynamics phase diagram and possible existence of a critical end point. The measured values are very well described by expectation from negative binomial distributions. We do not observe any nonmonotonic behavior in the ratios of the cumulants as a function of collision energy. The measured values of C-1/C-2 and C-3/C-1 can be directly compared to lattice quantum-chromodynamics calculations and thus allow extraction of both the chemical freeze-out temperature and the baryon chemical potential at each center-of-mass energy. The extracted baryon chemical potentials are in excellent agreement with a thermal-statistical analysis model.
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17. |
- Adare, A., et al.
(författare)
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Charged hadron multiplicity fluctuations in Au plus Au and Cu plus Cu collisions from s(NN)=22.5 to 200 GeV
- 2008
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 78:4
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive survey of event-by-event fluctuations of charged hadron multiplicity in relativistic heavy ions is presented. The survey covers Au+Au collisions at s(NN)=62.4 and 200 GeV, and Cu+Cu collisions at s(NN)=22.5,62.4, and 200 GeV. Fluctuations are measured as a function of collision centrality, transverse momentum range, and charge sign. After correcting for nondynamical fluctuations due to fluctuations in the collision geometry within a centrality bin, the remaining dynamical fluctuations expressed as the variance normalized by the mean tend to decrease with increasing centrality. The dynamical fluctuations are consistent with or below the expectation from a superposition of participant nucleon-nucleon collisions based upon p+p data, indicating that this dataset does not exhibit evidence of critical behavior in terms of the compressibility of the system. A comparison of the data with a model where hadrons are independently emitted from a number of hadron clusters suggests that the mean number of hadrons per cluster is small in heavy ion collisions.
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18. |
- Adare, A., et al.
(författare)
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Cross section and transverse single-spin asymmetry of eta mesons in p up arrow plus p collisions at root s=200 GeV at forward rapidity
- 2014
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Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 90:7
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the cross section and transverse single-spin asymmetry (AN) for. mesons at large pseudorapidity from root s = 200 GeV p up arrow + p collisions. The measured cross section for 0.5 < p(T) < 5.0 GeV/c and 3.0 < vertical bar eta vertical bar < 3.8 is well described by a next-to-leading-order perturbative-quantum-chromodynamics calculation. The asymmetries A(N) have been measured as a function of Feynman-x (x(F)) from 0.2 < vertical bar x(F)vertical bar < 0.7, as well as transverse momentum (p(T)) from 1.0 < p(T) < 4.5 GeV/c. The asymmetry averaged over positive x(F) is < A(N)> = 0.061 +/- 0.014. The results are consistent with prior transverse single-spin measurements of forward eta and pi(0) mesons at various energies in overlapping x(F) ranges. Comparison of different particle species can help to determine the origin of the large observed asymmetries in p up arrow + p collisions.
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19. |
- Adare, A., et al.
(författare)
-
Direct photon production in d+Au collisions at root s(NN)=200 GeV
- 2013
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 87:5
-
Tidskriftsartikel (refereegranskat)abstract
- Direct photons have been measured in root s(NN) = 200 GeV d + Au collisions at midrapidity. A wide p(T) range is covered by measurements of nearly real virtual photons (1 < p(T) < 6 GeV/c) and real photons (5 < p(T) < 16 GeV/c). The invariant yield of the direct photons in d + Au collisions over the scaled p + p cross section is consistent with unity. Theoretical calculations assuming standard cold-nuclear-matter effects describe the data well for the entire p(T) range. This indicates that the large enhancement of direct photons observed in Au + Au collisions for 1.0 < p(T) < 2.5 GeV/c is attributable to a source other than the initial-state nuclear effects.
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20. |
- Adare, A., et al.
(författare)
-
Low-mass vector-meson production at forward rapidity in p plus p collisions at root s=200 GeV
- 2014
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 90:5
-
Tidskriftsartikel (refereegranskat)abstract
- The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low-mass vector-meson ,omega, rho, and phi, production through the dimuon decay channel at forward rapidity (1.2 < vertical bar y vertical bar < 2.2) in p + p collisions at root s = 200 GeV. The differential cross sections for these mesons are measured as a function of both p(T) and rapidity. We also report the integrated differential cross sections over 1 < p(T) < 7 GeV/c and 1.2 < vertical bar y vertical bar < 2.2: d sigma/dy(omega + rho rho -> mu mu) = 80 +/- 6(stat) +/- 12(syst)nb and d sigma/dy(phi -> mu mu) = 27 +/- 3(stat) +/- 4(syst)nb. These results are compared with midrapidity measurements and calculations.
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21. |
- Adare, A., et al.
(författare)
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Medium Modification of Jet Fragmentation in Au plus Au Collisions at root S-NN=200 GeV Measured in Direct Photon-Hadron Correlations
- 2013
-
Ingår i: Physical Review Letters. - 1079-7114. ; 111:3
-
Tidskriftsartikel (refereegranskat)abstract
- The jet fragmentation function is measured with direct photon-hadron correlations in p + p and Au + Au collisions at root S-NN = 200 GeV. The P-T of the photon is an excellent approximation to the initial P-T of the jet and the ratio Z(T) = P-T(h)/P-T(gamma) is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in Au + Au collisions while a photon isolation cut is applied in p + p. I-AA, the ratio of hadron yield opposite the photon in Au + Au to that in p + p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high Z(T). The associated hadron yield at low Z(T) is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.
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22. |
- Adare, A., et al.
(författare)
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Nuclear matter effects on J/psi production in asymmetric Cu plus Au collisions at root S-NN=200 GeV
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:6
-
Tidskriftsartikel (refereegranskat)abstract
- We report on J/psi production from asymmetric Cu + Au heavy-ion collisions at root S-NN = 200 GeV at the Relativistic Heavy Ion Collider at both forward (Cu-going direction) and backward (Au-going direction) rapidities. The nuclear modification of J/psi yields in Cu + Au collisions in the Au-going direction is found to be comparable to that inAu + Au collisions when plotted as a function of the number of participating nucleons. In the Cu-going direction, J/psi production shows a stronger suppression. This difference is comparable in magnitude and has the same sign as the difference expected from shadowing effects due to stronger low-x gluon suppression in the larger Au nucleus.
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23. |
- Adare, A., et al.
(författare)
-
phi meson production in d plus Au collisions at root s(NN)=200 GeV
- 2015
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:4
-
Tidskriftsartikel (refereegranskat)abstract
- The PHENIX Collaboration has measured phi meson production in d + Au collisions at root s(NN) = 200 GeV using the dimuon and dielectron decay channels. The phi meson is measured in the forward (backward) d-going (Au-going) direction, 1.2 < y < 2.2 (-2.2 < y < -1.2) in the transverse-momentum (pT) range from 1-7 GeV/c and at midrapidity vertical bar y vertical bar < 0.35 in the p(T) range below 7 GeV/c. The phi meson invariant yields and nuclear-modification factors as a function of p(T), rapidity, and centrality are reported. An enhancement of phi meson production is observed in the Au-going direction, while suppression is seen in the d-going direction, and no modification is observed at midrapidity relative to the yield in p + p collisions scaled by the number of binary collisions. Similar behavior was previously observed for inclusive charged hadrons and open heavy flavor, indicating similar cold-nuclear-matter effects.
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24. |
- Adare, A., et al.
(författare)
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Photon-hadron jet correlations in p plus p and Au plus Au collisions at s(NN)=200 GeV
- 2009
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:2
-
Tidskriftsartikel (refereegranskat)abstract
- We report the observation at the Relativistic Heavy Ion Collider of suppression of back-to-back correlations in the direct photon+jet channel in Au+Au relative to p+p collisions. Two-particle correlations of direct photon triggers with associated hadrons are obtained by statistical subtraction of the decay photon-hadron (gamma-h) background. The initial momentum of the away-side parton is tightly constrained, because the parton-photon pair exactly balance in momentum at leading order in perturbative quantum chromodynamics, making such correlations a powerful probe of the in-medium parton energy loss. The away-side nuclear suppression factor, I-AA, in central Au+Au collisions, is 0.32 +/- 0.12(stat)+/- 0.09(syst) for hadrons of 3 < p(T)(h)< 5 in coincidence with photons of 5 < p(T)(gamma)< 15 GeV/c. The suppression is comparable to that observed for high-p(T) single hadrons and dihadrons. The direct photon associated yields in p+p collisions scale approximately with the momentum balance, z(T)equivalent to p(T)(h)/p(T)(gamma), as expected for a measurement of the away-side parton fragmentation function. We compare to Au+Au collisions for which the momentum balance dependence of the nuclear modification should be sensitive to the path-length dependence of parton energy loss.
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25. |
- Adare, A., et al.
(författare)
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System size and energy dependence of jet-induced hadron pair correlation shapes in Cu+Cu and Au+Au collisions at root S-NN 200 and 62.4 GeV
- 2007
-
Ingår i: Physical Review Letters. - 1079-7114. ; 98:23
-
Tidskriftsartikel (refereegranskat)abstract
- We present azimuthal angle correlations of intermediate transverse momentum (1-4 GeV/c) hadrons from dijets in Cu+Cu and Au+Au collisions at root s(NN)=62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is broadened, non-Gaussian, and peaked away from Delta phi=pi in central and semicentral collisions in all the systems. The broadening and peak location are found to depend upon the number of participants in the collision, but not on the collision energy or beam nuclei. These results are consistent with sound or shock wave models, but pose challenges to Cherenkov gluon radiation models.
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26. |
- Adler, S. S., et al.
(författare)
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Transverse-energy distributions at midrapidity in p plus p, d plus Au, and Au plus Au collisions at root s(NN)=62.4-200 GeV and implications for particle-production models
- 2014
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:4
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of the midrapidity transverse-energy distribution, dE(T)/d eta, are presented for p + p, d+Au, and Au+Au collisions atv root s(NN) = 200 GeV and additionally for Au+Au collisions atv root s(NN) = 62.4 and 130 GeV. The dE(T)/d eta distributions are first compared with the number of nucleon participants N-part, number of binary collisions N-coll, and number of constituent-quark participants N-qp calculated from a Glauber model based on the nuclear geometry. For Au+Au, < dE(T)/d eta >/N-part increases with N-part, while < dE(T)/d eta >/N-qp is approximately constant for all three energies. This indicates that the two-component ansatz, dE(T)/d eta alpha (1 - x)N-part/2 + xN(coll), which was used to represent E-T distributions, is simply a proxy for N-qp, and that the N-coll term does not represent a hard-scattering component in E-T distributions. The dE(T)/d eta distributions of Au+Au and d+Au are then calculated from the measured p + p E-T distribution using two models that both reproduce the Au+Au data. However, while the number-of-constituent-quark-participant model agrees well with the d+Au data, the additive-quark model does not.
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27. |
- Adare, A., et al.
(författare)
-
Centrality dependence of low-momentum direct-photon production in Au plus Au collisions at root s(NN)=200 GeV
- 2015
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:6
-
Tidskriftsartikel (refereegranskat)abstract
- The PHENIX experiment at RHIC has measured the centrality dependence of the direct photon yield from Au + Au collisions at root s(NN) = 200 GeV down to pT = 0.4 GeV/c. Photons are detected via photon conversions to e(+)e(-) pairs and an improved technique is applied that minimizes the systematic uncertainties that usually limit direct photon measurements, in particular at low pT. We find an excess of direct photons above the N-coll-scaled yield measured in p + p collisions. This excess yield is well described by an exponential distribution with an inverse slope of about 240 MeV/c in the pT range 0.6-2.0 GeV/c. While the shape of the pT distribution is independent of centrality within the experimental uncertainties, the yield increases rapidly with increasing centrality, scaling approximately with N-part(alpha), where alpha = 1.38 +/- 0.03(stat) +/- 0.07(syst).
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28. |
- Adare, A., et al.
(författare)
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Cold nuclear matter effects on J/psi production as constrained by deuteron-gold measurements at root S-NN=200 GeV
- 2008
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 77:2, s. 15-024912
-
Tidskriftsartikel (refereegranskat)abstract
- We present a new analysis of J/psi production yields in deuteron-gold collisions at root s(NN) =200 GeV using data taken from the PHENIX experiment in 2003 and previously published in S. S. Adler [Phys. Rev. Lett 96, 012304 (2006)]. The high statistics proton-proton J/psi data taken in 2005 are used to improve the baseline measurement and thus construct updated cold nuclear matter modification factors (R-dAu). A suppression of J/psi in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a region more sensitive to initial-state low-x gluons in the gold nucleus. The measured nuclear modification factors are compared to theoretical calculations of nuclear shadowing to which a J/psi (or precursor) breakup cross section is added. Breakup cross sections of sigma(breakup)=2.8(-1.4)(+1.7) (2.2(-1.5)(+1.6)) mb are obtained by fitting these calculations to the data using two different models of nuclear shadowing. These breakup cross-section values are consistent within large uncertainties with the 4.2 +/- 0.5 mb determined at lower collision energies. Projecting this range of cold nuclear matter effects to copper-copper and gold-gold collisions reveals that the current constraints are not sufficient to firmly quantify the additional hot nuclear matter effect.
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29. |
- Adare, A., et al.
(författare)
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Correlated production of p and (p)over-bar in Au+Au collisions at root s(NN)=200 GeV
- 2007
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 649:5-6, s. 359-369
-
Tidskriftsartikel (refereegranskat)abstract
- Correlations between p and (p) over bar at transverse momenta typical of enhanced baryon production in Au + Au collisions are reported. The PHENIX experiment has measured same and opposite sign baryon pairs in Au + Au collisions at root s(NN) = 200 GeV. Correlated production of p and p with the trigger particle from the range 2.5 < p(T) < 4.0 GeV/c and the associated particle with 1.8 < p(T) < 2.5 GeV/c is observed to be nearly independent of the centrality of the collisions. Same sign pairs show no correlation at any centrality. The conditional yield of mesons triggered by baryons (and anti-baryons) and mesons in the same p(T) range rises with increasing centrality, except for the most central collisions, where baryons show a significantly smaller number of associated mesons. These data are consistent with a picture in which hard scattered partons produce correlated p and (p) over bar in the p(T) region of the baryon excess. (c) 2007 Elsevier B.V. All rights reserved.
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30. |
- Adare, A., et al.
(författare)
-
Detailed measurement of the e(+)e(-) pair continuum in p plus p and Au plus Au collisions at root s(NN)=200 GeV and implications for direct photon production
- 2010
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 81:3
-
Tidskriftsartikel (refereegranskat)abstract
- PHENIX has measured the e(+)e(-) pair continuum in root s(NN) = 200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e(+)e(-) yield is compared to the expectations from hadronic sources, based on PHENIX measurements. In the intermediate-mass region, between the masses of the phi and the J/psi meson, the yield is consistent with expectations from correlated c (c) over bar production, although other mechanisms are not ruled out. In the low-mass region, below the phi, the p+p inclusive mass spectrum is well described by known contributions from light meson decays. In contrast, the Au+Au minimum bias inclusive mass spectrum in this region shows an enhancement by a factor of 4.7 +/- 0.4(stat) +/- 1.5(syst) +/- 0.9(model). At low mass (m(ee) < 0.3 GeV/c(2)) and high p(T) (1 < p(T) < 5 GeV/c) an enhanced e(+)e(-) pair yield is observed that is consistent with production of virtual direct photons. This excess is used to infer the yield of real direct photons. In central Au+Au collisions, the excess of the direct photon yield over the p+p is exponential in p(T), with inverse slope T = 221 +/- 19(stat) +/- 19(syst) MeV. Hydrodynamical models with initial temperatures ranging from T-init similar or equal to 300-600 MeV at times of 0.6-0.15 fm/c after the collision are in qualitative agreement with the direct photon data in Au+Au. For low p(T) < 1 GeV/c the low-mass region shows a further significant enhancement that increases with centrality and has an inverse slope of T similar or equal to 100 MeV. Theoretical models underpredict the low-mass, low-p(T) enhancement.
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31. |
- Adare, A., et al.
(författare)
-
Dihadron azimuthal correlations in Au+Au collisions at root s(NN)=200 GeV
- 2008
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 78:1
-
Tidskriftsartikel (refereegranskat)abstract
- Azimuthal angle (Delta phi) correlations are presented for a broad range of transverse momentum (0.4 < p(T) < 10 GeV/c) and centrality (0-92%) selections for charged hadrons from dijets in Au+Au collisions at root s(NN) = 200 GeV. With increasing p(T), the away-side Delta phi distribution evolves from a broad and relatively flat shape to a concave shape, then to a convex shape. Comparisons with p + p data suggest that the away-side distribution can be divided into a partially suppressed "head" region centered at Delta phi similar to pi, and an enhanced "shoulder" region centered at Delta phi similar to pi +/- 1.1. The p(T) spectrum for the associated hadrons in the head region softens toward central collisions. The spectral slope for the shoulder region is independent of centrality and trigger p(T). The properties of the near-side distributions are also modified relative to those in p + p collisions, reflected by the broadening of the jet shape in Delta phi and Delta eta, and an enhancement of the per-trigger yield. However, these modifications seem to be limited to p(T)less than or similar to 4 GeV/c, above which both the hadron pair shape and per-trigger yield become similar to p + p collisions. These observations suggest that both the away- and near-side distributions contain a jet fragmentation component which dominates for p(T) greater than or similar to 5 GeV/c and a medium-induced component which is important for p(T) less than or similar to 4 GeV/c. We also quantify the role of jets at intermediate and low p(T) through the yield of jet-induced pairs in comparison with binary scaled p + p pair yield. The yield of jet-induced pairs is suppressed at high pair proxy energy (sum of the p(T) magnitudes of the two hadrons) and is enhanced at low pair proxy energy. The former is consistent with jet quenching; the latter is consistent with the enhancement of soft hadron pairs due to transport of lost energy to lower p(T).
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32. |
- Adare, A., et al.
(författare)
-
Energy loss and flow of heavy quarks in Au+Au collisions at root s(NN) = 200 GeV
- 2007
-
Ingår i: Physical Review Letters. - 1079-7114. ; 98:17
-
Tidskriftsartikel (refereegranskat)abstract
- The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3 < p(T) < 9 GeV/c at midrapidity (y < 0.35) from heavy-flavor (charm and bottom) decays in Au + Au collisions at root s(NN) = 200 GeV. The nuclear modification factor R-AA relative to p + p collisions shows a strong suppression in central Au + Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy v(2) with respect to the reaction plane is observed for 0.5 < p(T) < 5 GeV/c indicating substantial heavy-flavor elliptic flow. Both R-AA and v(2) show a p(T) dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R-AA(p(T)) and v(2)(p(T)) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.
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33. |
- Adare, A., et al.
(författare)
-
Enhanced Production of Direct Photons in Au plus Au Collisions at root s(NN)=200 GeV and Implications for the Initial Temperature
- 2010
-
Ingår i: Physical Review Letters. - 1079-7114. ; 104:13
-
Tidskriftsartikel (refereegranskat)abstract
- The production of e(+)e(-) pairs for m(e+e-) < 0.3 GeV/c(2) and 1< p(T) < 5 GeV/c is measured in p + p and Au + Au collisions at root s(NN) = 200 GeV. An enhanced yield above hadronic sources is observed. Treating the excess as photon internal conversions, the invariant yield of direct photons is deduced. In central Au + Au collisions, the excess of the direct photon yield over p + p is exponential in transverse momentum, with an inverse slope T = 221 +/- 19(stat) +/- 19(syst) MeV. Hydrodynamical models with initial temperatures ranging from T-init similar to 300-600 MeV at times of similar to 0.6-0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at similar to 170 MeV.
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34. |
- Adare, A., et al.
(författare)
-
Heavy-quark production in p plus p and energy loss and flow of heavy quarks in Au plus Au collisions at root s(NN)=200 GeV
- 2011
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 84:4
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Tidskriftsartikel (refereegranskat)abstract
- Transverse momentum spectra of electrons (p(T)(e)) from semileptonic weak decays of heavy-flavor mesons in the range of 0.3 < p(T)(e) < 9.0 GeV/c have been measured at midrapidity (|y| < 0.35) by the PHENIX experiment at the Relativistic Heavy Ion Collider in p + p and Au + Au collisions at root s(NN) = 200 GeV. In addition, the azimuthal anisotropy parameter v(2) has been measured for 0.3 < p(T)(e) < 5.0 GeV/c in Au + Au collisions. The substantial modification in the p(T)(e) spectra in Au + Au compared with p + p collisions as well as the nonzero v(2) indicate substantial interactions and flow of heavy quarks in traversing the produced medium. Comparisons of these observables with detailed theoretical calculations can be used to identify the nature of these interactions and to quantify their extent.
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35. |
- Adare, A., et al.
(författare)
-
Measurement of gamma(1S+2S+3S) production in p plus p and Au plus Au collisions at root sNN=200 GeV
- 2015
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:2
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of bottomonium production in heavy-ion and p + p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three states, (1S + 2S + 3S), was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au + Au and p + p collisions at root sNN = 200 GeV. The (1S + 2S + 3S) -> e(+)e(-) differential cross section at midrapidity was found to be B(ee)d sigma/dy = 108 +/- 38 (stat) +/- 15 (syst) +/- 11 (luminosity) pb in p + p collisions. The nuclear modification factor in the 30% most central Au + Au collisions indicates a suppression of the total. state yield relative to the extrapolation from p + p collision data. The suppression is consistent with measurements made by STAR at RHIC and at higher energies by the CMS experiment at the Large Hadron Collider.
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36. |
- Adare, A., et al.
(författare)
-
Quantitative constraints on the transport properties of hot partonic matter from semi-inclusive single high transverse momentum pion suppression in Au plus Au collisions at root S-NN=200 GeV
- 2008
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 77:6
-
Tidskriftsartikel (refereegranskat)abstract
- The PHENIX experiment has measured the suppression of semi-inclusive single high-transverse-momentum pi(0)'s in Au+Au collisions at root s(NN) = 200 GeV. The present understanding of this suppression is in terms of energy loss of the parent (fragmenting) parton in a dense color-charge medium. We have performed a quantitative comparison between various parton energy-loss models and our experimental data. The statistical point-to-point uncorrelated as well as correlated systematic uncertainties are taken into account in the comparison. We detail this methodology and the resulting constraint on the model parameters, such as the initial color-charge density dN(g)/dy, the medium transport coefficient <(q) over cap >, or the initial energy-loss parameter epsilon(0). We find that high-transverse-momentum pi(0) suppression in Au+Au collisions has sufficient precision to constrain these model-dependent parameters at the +/- 20-25% (one standard deviation) level. These constraints include only the experimental uncertainties, and further studies are needed to compute the corresponding theoretical uncertainties.
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37. |
- Adare, A., et al.
(författare)
-
Scaling properties of azimuthal anisotropy in Au plus Au and Cu plus Cu collisions at root s(NN)=200 GeV
- 2007
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Ingår i: Physical Review Letters. - 1079-7114. ; 98:16
-
Tidskriftsartikel (refereegranskat)abstract
- Differential measurements of elliptic flow (v(2)) for Au+Au and Cu+Cu collisions at root s(NN)=200 GeV are used to test and validate predictions from perfect fluid hydrodynamics for scaling of v(2) with eccentricity, system size, and transverse kinetic energy (KET). For KET equivalent to m(T)-m up to similar to 1 GeV the scaling is compatible with hydrodynamic expansion of a thermalized fluid. For large values of KET mesons and baryons scale separately. Quark number scaling reveals a universal scaling of v(2) for both mesons and baryons over the full KET range for Au+Au. For Au+Au and Cu+Cu the scaling is more pronounced in terms of KET, rather than transverse momentum.
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38. |
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39. |
- Adare, A., et al.
(författare)
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Systematic study of azimuthal anisotropy in Cu plus Cu and Au plus Au collisions at root s(NN)=62.4 and 200 GeV
- 2015
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:3
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the dependence of azimuthal anisotropy nu(2) for inclusive and identified charged hadrons in Au + Au and Cu + Cu collisions on collision energy, species, and centrality. The values of nu(2) as a function of transverse momentum pT and centrality in Au + Au collisions at root s(NN) = 200 and 62.4 GeV are the same within uncertainties. However, in Cu + Cu collisions we observe a decrease in nu(2) values as the collision energy is reduced from 200 to 62.4 GeV. The decrease is larger in the more peripheral collisions. By examining both Au + Au and Cu + Cu collisions we find that nu(2) depends both on eccentricity and the number of participants, N-part. We observe that nu(2) divided by eccentricity (epsilon) monotonically increases with N-part and scales as N-part(1/3). The Cu + Cu data at 62.4 GeV falls below the other scaled nu(2) data. For identified hadrons, nu(2) divided by the number of constituent quarks n(q) is independent of hadron species as a function of transverse kinetic energy K E-T = m(T) - m between 0.1 < K E-T / n(q) < 1 GeV. Combining all of the above scaling and normalizations, we observe a near-universal scaling, with the exception of the Cu + Cu data at 62.4 GeV, of nu(2)/(nq center dot e center dot N-part(1/3)) vs K E-T / n(q) for all measured particles.
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40. |
- Adare, A., et al.
(författare)
-
Transverse momentum and centrality dependence of dihadron correlations in Au plus Au collisions at root s(NN)=200 GeV: Jet quenching and the response of partonic matter
- 2008
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 77:1, s. 6-011901
-
Tidskriftsartikel (refereegranskat)abstract
- Azimuthal angle (Delta phi) correlations are presented for charged hadrons from dijets for 0.4 < p(T)< 10 GeV/c in Au+Au collisions at root s(NN)=200 GeV. With increasing p(T), the away-side distribution evolves from a broad and relatively flat shape to a concave shape, then to a convex shape. Comparisons to p+p data suggest that the away-side can be divided into a partially suppressed "head" region centered at Delta phi similar to pi and an enhanced "shoulder" region centered at Delta phi similar to pi +/- 1.1. The p(T) spectrum for the head region softens toward central collisions, consistent with the onset of jet quenching. The spectral slope for the shoulder region is independent of centrality and trigger p(T), which offers constraints on energy transport mechanisms and suggests that it contains the medium response to energetic jets.
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41. |
- Adler, S. S., et al.
(författare)
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High transverse momentum eta meson production in p+p, d+Au, and Au+Au collisions at root s(NN)=200 GeV
- 2007
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 75:2
-
Forskningsöversikt (refereegranskat)abstract
- Inclusive transverse momentum spectra of eta mesons in the range p(T)approximate to 2-12 GeV/c have been measured at midrapidity (vertical bar eta vertical bar < 0.35) by the PHENIX experiment at RHIC in p+p,d+Au, and Au+Au collisions at root s(NN)=200 GeV. The eta mesons are reconstructed through their eta ->gamma gamma channel for the three colliding systems as well as through the eta ->pi(0)pi(+)pi(-) decay mode in p+p and d+Au collisions. The nuclear modification factor in d+Au collisions, R-dAu(p(T))approximate to 1.0-1.1, suggests at most only modest p(T) broadening ("Cronin enhancement"). In central Au+Au reactions, the eta yields are significantly suppressed, with R-AuAu(p(T))approximate to 0.2. The ratio of eta to pi(0) yields is approximately constant as a function of p(T) for the three colliding systems in agreement with the high-p(T) world average of R-eta/pi(0)approximate to 0.5 in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range of center-of-mass energies (root sNN approximate to 3-1800 GeV) as well as, for high scaled momentum x(p), in e(+)e(-) annihilations at root s=91.2 GeV. These results are consistent with a scenario where high-p(T) eta production in nuclear collisions at the Relativistic Heavy Ion Collider is largely unaffected by initial-state effects but where light-quark mesons (pi(0),eta) are equally suppressed due to final-state interactions of the parent partons in the dense medium produced in Au+Au reactions.
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42. |
- Adolph, C., et al.
(författare)
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Azimuthal asymmetries of charged hadrons produced in high-energy muon scattering off longitudinally polarised deuterons
- 2018
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Ingår i: European Physical Journal C. - : SPRINGER. - 1434-6044 .- 1434-6052. ; 78:11
-
Tidskriftsartikel (refereegranskat)abstract
- Single hadron azimuthal asymmetries of positive and negative hadrons produced in muon semi-inclusive deep inelastic scattering off longitudinally polarised deuterons are determined using the 2006 COMPASS data and also combined all deuteron COMPASS data. For each hadron charge, the dependence of the azimuthal asymmetry on the hadron azimuthal angle f is obtained by means of a fiveparameter fitting function that besides a f-independent term includes four modulations predicted by theory: sin f, sin 2f, sin 3f and cos f. The amplitudes of the five terms have been extracted, first, for the hadrons in the whole available kinematic region. In further fits, performed for hadrons from a restricted kinematic region, the f-dependence is determined as a function of one of three variables (Bjorken-x, fractional energy of virtual photon taken by the outgoing hadron and hadron transverse momentum), while disregarding the others. Except thef-independent term, all themodulation amplitudes are very small, and no clear kinematic dependence could be observed within experimental uncertainties.
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43. |
- Adolph, C., et al.
(författare)
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Final COMPASS results on the deuteron spin-dependent structure function g(1)(d) and the Bjorken sum rule
- 2017
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 769, s. 34-41
-
Tidskriftsartikel (refereegranskat)abstract
- Final results are presented from the inclusive measurement of deep-inelastic polarised-muon scattering on longitudinally polarised deuterons using a 6LiD target. The data were taken at 160 GeV beam energy and the results are shown for the kinematic range 1 (GeV/c)2 < Q2 < 100 (GeV/c)2 in photon virtuality, 0.004 < x < 0.7 in the Bjorken scaling variable and W > 4GeV/c2 in the mass of the hadronic final state. The deuteron double-spin asymmetry A(1)(d) and the deuteron longitudinal-spin structure function g(1)(d) are presented in bins of x and Q2. Towards lowest accessible values of x, g(1)(d) decreases and becomes consistent with zero within uncertainties. The presented final g(1)(p) values together with the recently published final g(1)(p) values of COMPASS are used to again evaluate the Bjorken sum rule and perform the QCD fit to the g1 world data at next-to-leading order of the strong coupling constant. In both cases, changes in central values of the resulting numbers are well within statistical uncertainties. The flavour singlet axial charge a0, which is identified in the MS renormalisation scheme with the total contribution of quark helicities to the nucleon spin, is extracted at next-to-leading order accuracy from only the COMPASS deuteron data: a0(Q2 = 3 (GeV/c)2) = 0.32 +/- 0.02stat +/- 0.04syst +/- 0.05evol. Together with the recent results on the proton spin structure function g(1)(p), the results on g(1)(d) constitute the COMPASS legacy on the measurements of g1 through inclusive spin-dependent deep inelastic scattering.
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44. |
- Adolph, C., et al.
(författare)
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First measurement of the Sivers asymmetry for gluons using SIDIS data
- 2017
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 772, s. 854-864
-
Tidskriftsartikel (refereegranskat)abstract
- The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. For quarks, it was studied in previous measurements of the azimuthal asymmetry of hadrons produced in semi-inclusive deep inelastic scattering of leptons off transversely polarised nucleon targets, and it was found to be non-zero. In this letter the evaluation of the Sivers asymmetry for gluons is presented. The contribution of the photon-gluon fusion subprocess is enhanced by requiring two high transverse-momentum hadrons. The analysis method is based on a Monte Carlo simulation that includes three hard processes: photon-gluon fusion, QCD Compton scattering and the leading-order virtual-photon absorption process. The Sivers asymmetries of the three processes are simultaneously extracted using the LEPTO event generator and a neural network approach. The method is applied to samples of events containing at least two hadrons with large transverse momentum from the COMPASS data taken with a 160 GeV/c muon beam scattered off transversely polarised deuterons and protons. With a significance of about two standard deviations, a negative value is obtained for the gluon Sivers asymmetry. The result of a similar analysis for a Collins-like asymmetry for gluons is consistent with zero. (C) 2017 The Author(s). Published by Elsevier B.V.
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45. |
- Adolph, C., et al.
(författare)
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Multiplicities of charged kaons from deep-inelastic muon scattering off an isoscalar target
- 2017
-
Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 767, s. 133-141
-
Tidskriftsartikel (refereegranskat)abstract
- Precise measurements of charged-kaon multiplicities in deep inelastic scattering were performed. The results are presented in three-dimensional bins of the Bjorken scaling variable x, the relative virtual-photon energy y, and the fraction z of the virtual-photon energy carried by the produced hadron. The data were obtained by the COMPASS Collaboration by scattering 160 GeV muons off an isoscalar (LiD)-Li-6 target. They cover the kinematic domain 1 (GeV/c)(2) < Q(2) < 60 (GeV/c)(2) in the photon virtuality, 0.004 < x < 0.4, 0.1 < y < 0.7, 0.20 < z < 0.85, and W > 5 GeV/c(2) in the invariant mass of the hadronic system. The results from the sum of the z-integrated K+ and K- multiplicities at high x point to a value of the non-strange quark fragmentation function larger than obtained by the earlier DSS fit.
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46. |
- Adolph, C., et al.
(författare)
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Multiplicities of charged pions and charged hadrons from deep-inelastic scattering of muons off an isoscalar target
- 2017
-
Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 764, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- Multiplicities of charged pions and charged hadrons produced in deep-inelastic scattering were measured in three-dimensional bins of the Bjorken scaling variable x, the relative virtual-photon energy y and the relative hadron energy z. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam and an isoscalar target ((LiD)-Li-6). They cover the kinematic domain in the photon virtuality Q(2) > 1 (GeV/c) 2, 0.004 < x < 0.4, 0.2 < z < 0.85 and 0.1 < y < 0.7. In addition, a leading-order pQCD analysis was performed using the pion multiplicity results to extract quark fragmentation functions.
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47. |
- Adolph, C., et al.
(författare)
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Sivers asymmetry extracted in SIDIS at the hard scales of the Drell-Yan process at COMPASS
- 2017
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 770, s. 138-145
-
Tidskriftsartikel (refereegranskat)abstract
- Eight proton transverse-spin-dependent azimuthal asymmetries are extracted in four regions of the photon virtuality Q(2) from the COMPASS 2010 semi-inclusive hadron measurements in deep inelastic muon nucleon scattering. These Q(2) regions correspond to the four regions of the di-muon mass root Q(2) used in the ongoing analyses of the COMPASS Drell-Yan measurements, which allows for a future direct comparison of the nucleon transverse-momentum-dependent parton distribution functions extracted from these two alternative measurements. In addition, for the azimuthal asymmetries induced by the Sivers transverse-momentum-dependent parton distribution function various two-dimensional kinematic dependences are presented. The integrated Sivers asymmetries are found to be positive with an accutacy that appears to be sufficient to test the sign change of the Sivers function predicted by Quantum Chromodynamics.
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48. |
- Afanasiev, S., et al.
(författare)
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Charged Kaon Interferometric Probes of Space-Time Evolution in Au plus Au Collisions at s(NN)=200 GeV
- 2009
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Ingår i: Physical Review Letters. - 1079-7114. ; 103:14
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Tidskriftsartikel (refereegranskat)abstract
- Bose-Einstein correlations of charged kaons are used to probe Au+Au collisions at s(NN)=200 GeV and are compared to charged pion probes, which have a larger hadronic scattering cross section. Three-dimensional Gaussian source radii are extracted, along with a one-dimensional kaon emission source function. The centrality dependences of the three Gaussian radii are well described by a single linear function of N-part(1/3) with a zero intercept. Imaging analysis shows a deviation from a Gaussian tail at r greater than or similar to 10 fm, although the bulk emission at lower radius is well described by a Gaussian. The presence of a non-Gaussian tail in the kaon source reaffirms that the particle emission region in a heavy-ion collision is extended, and that similar measurements with pions are not solely due to the decay of long-lived resonances.
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49. |
- Afanasiev, S., et al.
(författare)
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Elliptic flow for phi mesons and (Anti)deuterons in Au+Au collisions at root s(NN)=200 GeV
- 2007
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Ingår i: Physical Review Letters. - 1079-7114. ; 99:5
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Tidskriftsartikel (refereegranskat)abstract
- Differential elliptic flow (v(2)) for phi mesons and (anti)deuterons ((d) over bar )d is measured for Au + Au collisions at root s(NN) = 200 GeV. The v(2) for phi mesons follows the trend of lighter pi(+/-) and K-+/- mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not the primary driver for elliptic flow development. The v(2) values for ((d) over bar )d suggest that elliptic flow is additive for composite particles. This further validation of the universal scaling of v(2) per constituent quark for baryons and mesons suggests that partonic collectivity dominates the transverse expansion dynamics.
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50. |
- Afanasiev, S., et al.
(författare)
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High-p(T) pi(0) production with respect to the reaction plane in Au plus Au collisions at s(NN)=200 GeV
- 2009
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:5
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the azimuthal anisotropy of high-p(T) neutral pion (pi(0)) production in Au+Au collisions at s(NN)=200 GeV by the PHENIX experiment are presented. The data included in this article were collected during the 2004 Relativistic Heavy Ion Collider running period and represent approximately an order of magnitude increase in the number of analyzed events relative to previously published results. Azimuthal angle distributions of pi(0) mesons detected in the PHENIX electromagnetic calorimeters are measured relative to the reaction plane determined event-by-event using the forward and backward beam-beam counters. Amplitudes of the second Fourier component (v(2)) of the angular distributions are presented as a function of pi(0) transverse momentum (p(T)) for different bins in collision centrality. Measured reaction plane dependent pi(0) yields are used to determine the azimuthal dependence of the pi(0) suppression as a function of p(T), R-AA(Delta phi,p(T)). A jet-quenching motivated geometric analysis is presented that attempts to simultaneously describe the centrality dependence and reaction plane angle dependence of the pi(0) suppression in terms of the path lengths of hypothetical parent partons in the medium. This set of results allows for a detailed examination of the influence of geometry in the collision region and of the interplay between collective flow and jet-quenching effects along the azimuthal axis.
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