| 1. |
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| 2. |
- Namkoong, H, et al.
(författare)
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DOCK2 is involved in the host genetics and biology of severe COVID-19
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 609:7928, s. 754-
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Tidskriftsartikel (refereegranskat)abstract
- Identifying the host genetic factors underlying severe COVID-19 is an emerging challenge1–5. Here we conducted a genome-wide association study (GWAS) involving 2,393 cases of COVID-19 in a cohort of Japanese individuals collected during the initial waves of the pandemic, with 3,289 unaffected controls. We identified a variant on chromosome 5 at 5q35 (rs60200309-A), close to the dedicator of cytokinesis 2 gene (DOCK2), which was associated with severe COVID-19 in patients less than 65 years of age. This risk allele was prevalent in East Asian individuals but rare in Europeans, highlighting the value of genome-wide association studies in non-European populations. RNA-sequencing analysis of 473 bulk peripheral blood samples identified decreased expression of DOCK2 associated with the risk allele in these younger patients. DOCK2 expression was suppressed in patients with severe cases of COVID-19. Single-cell RNA-sequencing analysis (n = 61 individuals) identified cell-type-specific downregulation of DOCK2 and a COVID-19-specific decreasing effect of the risk allele on DOCK2 expression in non-classical monocytes. Immunohistochemistry of lung specimens from patients with severe COVID-19 pneumonia showed suppressed DOCK2 expression. Moreover, inhibition of DOCK2 function with CPYPP increased the severity of pneumonia in a Syrian hamster model of SARS-CoV-2 infection, characterized by weight loss, lung oedema, enhanced viral loads, impaired macrophage recruitment and dysregulated type I interferon responses. We conclude that DOCK2 has an important role in the host immune response to SARS-CoV-2 infection and the development of severe COVID-19, and could be further explored as a potential biomarker and/or therapeutic target.
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| 3. |
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| 4. |
- Wang, QBS, et al.
(författare)
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The whole blood transcriptional regulation landscape in 465 COVID-19 infected samples from Japan COVID-19 Task Force
- 2022
-
Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1, s. 4830-
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Tidskriftsartikel (refereegranskat)abstract
- Coronavirus disease 2019 (COVID-19) is a recently-emerged infectious disease that has caused millions of deaths, where comprehensive understanding of disease mechanisms is still unestablished. In particular, studies of gene expression dynamics and regulation landscape in COVID-19 infected individuals are limited. Here, we report on a thorough analysis of whole blood RNA-seq data from 465 genotyped samples from the Japan COVID-19 Task Force, including 359 severe and 106 non-severe COVID-19 cases. We discover 1169 putative causal expression quantitative trait loci (eQTLs) including 34 possible colocalizations with biobank fine-mapping results of hematopoietic traits in a Japanese population, 1549 putative causal splice QTLs (sQTLs; e.g. two independent sQTLs at TOR1AIP1), as well as biologically interpretable trans-eQTL examples (e.g., REST and STING1), all fine-mapped at single variant resolution. We perform differential gene expression analysis to elucidate 198 genes with increased expression in severe COVID-19 cases and enriched for innate immune-related functions. Finally, we evaluate the limited but non-zero effect of COVID-19 phenotype on eQTL discovery, and highlight the presence of COVID-19 severity-interaction eQTLs (ieQTLs; e.g., CLEC4C and MYBL2). Our study provides a comprehensive catalog of whole blood regulatory variants in Japanese, as well as a reference for transcriptional landscapes in response to COVID-19 infection.
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| 5. |
- Adare, A., et al.
(författare)
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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
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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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| 6. |
- Abelev, B., et al.
(författare)
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Measurement of electrons from semileptonic heavy-flavor hadron decays in pp collisions at root s=7 TeV
- 2012
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Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 86:11
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Tidskriftsartikel (refereegranskat)abstract
- The differential production cross section of electrons from semileptonic heavy-flavor hadron decays has been measured at midrapidity (\y\ < 0.5) in proton-proton collisions at root s = 7 TeV with ALICE at the LHC. Electrons were measured in the transverse momentum range 0.5 < p(t) < 8 GeV/c. Predictions from a fixed-order perturbative QCD calculation with next-to-leading-log resummation agree with the data within the theoretical and experimental uncertainties. DOI: 10.1103/PhysRevD.86.112007
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| 7. |
- Abelev, B., et al.
(författare)
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Net-Charge Fluctuations in Pb-Pb Collisions at root s(NN)=2.76 TeV
- 2013
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Ingår i: Physical Review Letters. - 1079-7114. ; 110:15
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Tidskriftsartikel (refereegranskat)abstract
- We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at root s(NN) = 2.76 TeV, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudorapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the fluctuations at the LHC are smaller compared to the measurements at the BNL Relativistic Heavy Ion Collider, and as such, closer to what has been theoretically predicted for the formation of a quark-gluon plasma. DOI: 10.1103/PhysRevLett.110.152301
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| 8. |
- Aamodt, K., et al.
(författare)
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Alignment of the ALICE Inner Tracking System with cosmic-ray tracks
- 2010
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 5
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Konferensbidrag (refereegranskat)abstract
- ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 mu m in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10(5) charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.
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| 9. |
- Aamodt, K., et al.
(författare)
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Charged-particle multiplicity measurement in proton-proton collisions at root s=0.9 and 2.36 TeV with ALICE at LHC
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 68:1-2, s. 89-108
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Tidskriftsartikel (refereegranskat)abstract
- Charged-particle production was studied in proton-proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36 TeV in the pseudorapidity range vertical bar eta vertical bar < 1.4. In the central region (vertical bar eta vertical bar < 0.5), at 0.9 TeV, we measure charged-particle pseudo-rapidity density dN(ch)/d eta = 3.02 +/- 0.01(stat.)(-0.05)(+0.08)(syst.) for inelastic interactions, and dN(ch)/d eta = 3.58 +/- 0.01 (stat.)(-0.12)(+0.12)(syst.) for non-single-diffractive interactions. At 2.36 TeV, we find dN(ch)/d eta = 3.77 +/- 0.01(stat.)(-0.12)(+0.25)(syst.) for inelastic, and dN(ch)/d eta = 4.43 +/- 0.01(stat.)(-0.12)(+0.17)(syst.) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7% +/- 0.5%(stat.)(-2.8)(+5.7)%(syst.) for inelastic and 23.7% +/- 0.5%(stat.)(-1.1)(+4.6)%(syst.) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton-antiproton data and to model predictions.
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| 10. |
- Aamodt, K., et al.
(författare)
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Charged-particle multiplicity measurement in proton-proton collisions at root s=7 TeV with ALICE at LHC
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 68:3-4, s. 345-354
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Tidskriftsartikel (refereegranskat)abstract
- The pseudorapidity density and multiplicity distribution of charged particles produced in proton-proton collisions at the LHC, at a centre-of-mass energy root s = 7 TeV, were measured in the central pseudorapidity region vertical bar eta vertical bar < 1. Comparisons are made with previous measurements at root s = 0.9 TeV and 2.36 TeV. At root s = 7 TeV, for events with at least one charged particle in |eta vertical bar| < 1, we obtain dN(ch)/d eta = 6.01 +/- 0.01(stat.)(-0.12)(+0.20) (syst.). This corresponds to an increase of 57.6%+/-0.4%(stat.)(-1.8%)(+3.6) (syst.) relative to collisions at 0.9 TeV, significantly higher than calculations from commonly used models. The multiplicity distribution at 7 TeV is described fairly well by the negative binomial distribution.
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| 11. |
- Aamodt, K., et al.
(författare)
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First proton-proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at root s=900 GeV
- 2010
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 65:1-2, s. 111-125
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Tidskriftsartikel (refereegranskat)abstract
- On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range vertical bar eta vertical bar < 0.5, we obtain dN(ch)/d eta = 3.10 +/- 0.13(stat.) +/- 0.22(syst.) for all inelastic interactions, and dN(ch)/d eta = 3.51 +/- 0.15(stat.) +/- 0.25(syst.) for nonsingle diffractive interactions. These results are consistent with previous measurements in proton-antiproton interactions at the same centre-of-mass energy at the CERN Sp<(p)over bar>S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.
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| 12. |
- Aamodt, K., et al.
(författare)
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Midrapidity Antiproton-to-Proton Ratio in pp Collisons root s=0.9 and 7 TeV Measured by the ALICE Experiment
- 2010
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Ingår i: Physical Review Letters. - 1079-7114. ; 105:7
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Tidskriftsartikel (refereegranskat)abstract
- The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at root s = 0.9 and 7 TeV during the initial running periods of the Large Hadron Collider. The measurement covers the transverse momentum interval 0.45 < p(t) < 1.05 GeV/c and rapidity vertical bar y vertical bar < 0.5. The ratio is measured to be R-vertical bar y vertical bar<0.5 = 0.957 +/- 0.006(stat) +/- 0.0014(syst) at 0.9 Tev and R-vertical bar y vertical bar<0.5 = 0.991 +/- 0.005 +/- 0.014(syst) at 7 TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on any additional contributions to baryon-number transfer over very large rapidity intervals in pp collisions.
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| 13. |
- Aamodt, K., et al.
(författare)
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Production of pions, kaons and protons in pp collisions at root s=900 GeV with ALICE at the LHC
- 2011
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:6
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Tidskriftsartikel (refereegranskat)abstract
- The production of pi(+), pi(-), K+, K-, p, and (p) over bar at mid-rapidity has been measured in proton-proton collisions at root s = 900 GeV with the ALICE detector. Particle identification is performed using the specific energy loss in the inner tracking silicon detector and the time projection chamber. In addition, time-of-flight information is used to identify hadrons at higher momenta. Finally, the distinctive kink topology of the weak decay of charged kaons is used for an alternative measurement of the kaon transverse momentum (p(t)) spectra. Since these various particle identification tools give the best separation capabilities over different momentum ranges, the results are combined to extract spectra from p(t) = 100 MeV/c to 2.5 GeV/c. The measured spectra are further compared with QCD-inspired models which yield a poor description. The total yields and the mean pt are compared with previous measurements, and the trends as a function of collision energy are discussed.
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| 14. |
- Aamodt, K., et al.
(författare)
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Transverse momentum spectra of charged particles in proton-proton collisions at root s=900 GeV with ALICE at the LHC
- 2010
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 693:2, s. 53-68
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Tidskriftsartikel (refereegranskat)abstract
- The inclusive charged particle transverse momentum distribution is measured in proton-proton collisions at root s = 900 GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region (vertical bar eta vertical bar < 0.8) over the transverse momentum range 0.15 < p(T) < 10 GeV/c. The correlation between transverse momentum and particle multiplicity is also studied. Results are presented for inelastic (INEL) and non-single-diffractive (NSD) events. The average transverse momentum for vertical bar eta vertical bar < 0.8 is < p(T)>(INEL) = 0.483 +/- 0.001 (stat.) +/- 0.007 (syst.) GeV/c and < p(T)>(NSD) = 0.489 +/- 0.001 (stat.) +/- 0.007 (syst.) GeV/c, respectively. The data exhibit a slightly larger < p(T)> than measurements in wider pseudorapidity intervals. The results are compared to simulations with the Monte Carlo event generators PYTHIA and PHOJET. (C) 2010 Published by Elsevier B.V.
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| 15. |
- Aamodt, K., et al.
(författare)
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Two-pion Bose-Einstein correlations in pp collisions at root s=900 GeV
- 2010
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Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 82:5
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Tidskriftsartikel (refereegranskat)abstract
- We report on the measurement of two-pion correlation functions from pp collisions at root s = 900 GeV performed by the ALICE experiment at the Large Hadron Collider. Our analysis shows an increase of the Hanbury Brown-Twiss radius with increasing event multiplicity, in line with other measurements done in particle- and nuclear collisions. Conversely, the strong decrease of the radius with increasing transverse momentum, as observed at the Relativistic Heavy Ion Collider and at Tevatron, is not manifest in our data.
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| 16. |
- Abelev, B., et al.
(författare)
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Heavy flavour decay muon production at forward rapidity in proton-proton collisions at root s=7 TeV
- 2012
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 708:3-5, s. 265-275
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Tidskriftsartikel (refereegranskat)abstract
- The production of muons from heavy flavour decays is measured at forward rapidity in proton-proton collisions at root s = 7 TeV collected with the ALICE experiment at the LHC. The analysis is carried out on a data sample corresponding to an integrated luminosity L-int = 16.5 nb(-1). The transverse momentum and rapidity differential production cross sections of muons from heavy flavour decays are measured in the rapidity range 2.5 < y <4, over the transverse momentum range 2 < p(t) < 12 GeV/c. The results are compared to predictions based on perturbative QCD calculations. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 17. |
- Abelev, B., et al.
(författare)
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Inclusive J/psi production in pp collisions at root s=2.76 TeV
- 2012
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 718:2, s. 295-306
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center-of-mass energy root s = 2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges vertical bar y vertical bar < 0.9 and 2.5 < y <4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L-int(e) = 1.1 nb(-1) and L-int(mu) = 19.9 nb(-1), and the corresponding signal statistics are N-J/psi(e+e-) = 59 +/- 14 and N-J/psi(mu+mu-) = 1364 +/- 53. We present d sigma(J/psi)/dy for the two rapidity regions under study and, for the forward-y range, d(2)sigma(J/psi)/dydp(t) in the transverse momentum domain 0 < p(t) < 8 GeV/c. The results are compared with previously published results at root s = 7 TeV and with theoretical calculations. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 18. |
- Abelev, B., et al.
(författare)
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J/psi production as a function of charged particle multiplicity in pp collisions at root s=7 TeV
- 2012
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 712:3, s. 165-175
-
Tidskriftsartikel (refereegranskat)abstract
- The ALICE Collaboration reports the measurement of the relative J/psi yield as a function of charged particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 7 TeV at the LHC. J/psi particles are detected for p(t) > 0, in the rapidity interval vertical bar y vertical bar < 0.9 via decay into e(+)e(-), and in the interval 2.5 < y < 4.0 via decay into mu(+)/mu(-) pairs. An approximately linear increase of the J/psi yields normalized to their event average (dN(J/psi)/dy)/(dN(J/psi)/dy) with (dN(ch)/c eta)/(dN(ch)/d eta) is observed in both rapidity ranges, where dN(ch)/d eta is measured within vertical bar eta vertical bar < 1 and p(t) > 0. In the highest multiplicity interval with (dN(ch)/d eta)(bin)) = 24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/psi yield by a factor of about 5 at 2.5 < y <4 (8 at vertical bar y vertical bar < 0.9) is observed. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 19. |
- Abelev, B., et al.
(författare)
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J/psi Suppression at Forward Rapidity in Pb-Pb Collisions at root s(NN)=2.76 TeV
- 2012
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Ingår i: Physical Review Letters. - 1079-7114. ; 109:7
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE experiment has measured the inclusive J/psi production in Pb-Pb collisions at root s(NN) = 2.76 TeV down to zero transverse momentum in the rapidity range 2.5 < y < 4. A suppression of the inclusive J/psi yield in Pb-Pb is observed with respect to the one measured in pp collisions scaled by the number of binary nucleon-nucleon collisions. The nuclear modification factor, integrated over the 0%-80% most central collisions, is 0.545 +/- 0.032(stat) +/- 0.083dsyst_ and does not exhibit a significant dependence on the collision centrality. These features appear significantly different from measurements at lower collision energies. Models including J/psi production from charm quarks in a deconfined partonic phase can describe our data.
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| 20. |
- Abelev, B., et al.
(författare)
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(KsKs0)-K-0 correlations in pp collisions at root s=7 TeV from the LHC ALICE experiment
- 2012
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 717:1-3, s. 151-161
-
Tidskriftsartikel (refereegranskat)abstract
- Identical neutral kaon pair correlations are measured in root s = 7 TeV pp collisions in the ALICE experiment. One-dimensional (KsKs0)-K-0 correlation functions in terms of the invariant momentum difference of kaon pairs are formed in two multiplicity and two transverse momentum ranges. The femtoscopic parameters for the radius and correlation strength of the kaon source are extracted. The fit includes quantum statistics and final-state interactions of the a(0)/f(0) resonance. (KsKs0)-K-0 correlations show an increase in radius for increasing multiplicity and a slight decrease in radius for increasing transverse mass, mT, as seen in pi pi correlations in pp collisions and in heavy-ion collisions. Transverse mass scaling is observed between the (KsKs0)-K-0 and pi pi radii. Also, the first observation is made of the decay of the f(2)'(1525) meson into the (KsKs0)-K-0 channel in pp collisions. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 21. |
- Abelev, B., et al.
(författare)
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Measurement of event background fluctuations for charged particle jet reconstruction in Pb-Pb collisions at root s(NN)=2.76 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :3
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Tidskriftsartikel (refereegranskat)abstract
- The effect of event background fluctuations on charged particle jet reconstruction in Pb-Pb collisions at root s(NN) = 2.76 TeV has been measured with the ALICE experiment. The main sources of non-statistical fluctuations are characterized based purely on experimental data with an unbiased method, as well as by using single high p(t) particles and simulated jets embedded into real Pb-Pb events and reconstructed with the anti-k(t) jet finder. The influence of a low transverse momentum cut-off on particles used in the jet reconstruction is quantified by varying the minimum track p(t) between 0.15 GeV/c and 2 GeV/c. For embedded jets reconstructed from charged particles with p(t) > 0.15 GeV/c, the uncertainty in the reconstructed jet transverse momentum due to the heavy-ion background is measured to be 11.3 GeV/c (standard deviation) for the 10% most central Pb-Pb collisions, slightly larger than the value of 11.0 GeV/c measured using the unbiased method. For a higher particle transverse momentum threshold of 2 GeV/c, which will generate a stronger bias towards hard fragmentation in the jet finding process, the standard deviation of the fluctuations in the reconstructed jet transverse momentum is reduced to 4.8-5.0 GeV/c for the 10% most central events. A non-Gaussian tail of the momentum uncertainty is observed and its impact on the reconstructed jet spectrum is evaluated for varying particle momentum thresholds, by folding the measured fluctuations with steeply falling spectra.
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| 22. |
- Abelev, B., et al.
(författare)
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Multi-strange baryon production in pp collisions at root s=7 TeV with ALICE
- 2012
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 712:4-5, s. 309-318
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Tidskriftsartikel (refereegranskat)abstract
- A measurement of the multi-strange Xi(-) and Omega(-) baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic proton-proton collisions at a centre-of-mass energy of 7 TeV. The transverse momentum (p(T)) distributions were studied at mid-rapidity (vertical bar y vertical bar < 0.5) in the range of 0.6 < p(T) < 8.5 GeV/c Xi(-) for and Xi(+) baryons, and in the range of 0.8 < P-T < 5 GeV/c for Omega(-) and<(Omega)over bar>(+). Baryons and antibaryons were measured as separate particles and we find that the baryon to antibaryon ratio of both particle species is consistent with unity over the entire range of the measurement. The statistical precision of the current data has allowed us to measure a difference between the mean p(T) of Xi(-) ((Xi) over bar)(+) and Omega(-) ((Omega) over bar (+)). Particle yields, mean pi, and the spectra in the intermediate pi range are not well described by the PYTHIA Perugia 2011 tune Monte Carlo event generator, which has been tuned to reproduce the early LHC data. The discrepancy is largest for Omega(-)((Omega) over bar (+)). This PYTHIA tune approaches the pi spectra of Xi(-) and Xi(+) baryons below p(T) <0.85 GeV/c and describes the Xi(-) and Xi(+) spectra above p(T) > 6.0 GeV/c. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Omega(-) +(Omega) over bar (+))/(Xi(-) + Xi(+)) as a function of transverse mass. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 23. |
- Abelev, B., et al.
(författare)
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Production of Muons from Heavy Flavor Decays at Forward Rapidity in pp and Pb-Pb Collisions at root s(NN)=2.76 TeV
- 2012
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Ingår i: Physical Review Letters. - 1079-7114. ; 109:11
-
Tidskriftsartikel (refereegranskat)abstract
- The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, 2.5 < y < 4, in pp and Pb-Pb collisions at root s(NN) = 2.76 TeV. The p(t)-differential inclusive cross section of muons from heavy-flavor decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of p(t) and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3-4 is observed in 6 < p(t) < 10 GeV/c. The suppression shows no significant p(t) dependence.
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| 24. |
- Abelev, B., et al.
(författare)
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Suppression of high transverse momentum D mesons in central Pb-Pb collisions at root s(NN)=2.76 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :9
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Tidskriftsartikel (refereegranskat)abstract
- The production of the prompt charm mesons D-0, D+, D*(+), and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the LHC, at a centre-of-mass energy root s(NN) = 2.76 TeV per nucleon-nucleon collision. The p(t)-differential production yields in the range 2 < p(t) < 16 GeV/c at central rapidity, vertical bar y vertical bar < 0.5, were used to calculate the nuclear modification factor R-AA with respect to a proton-proton reference obtained from the cross section measured at root s = 7 TeV and scaled to root s = 2.76 TeV. For the three meson species, R-AA shows a suppression by a factor 3-4, for transverse momenta larger than 5 GeV/c in the 20% most central collisions. The suppression is reduced for peripheral collisions.
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| 25. |
- Abelev, B., et al.
(författare)
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Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at root s=0.9, 2.76 and 7 TeV
- 2012
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:9
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the sphericity of primary charged particles in minimum bias proton-proton collisions at root s = 0.9, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is measured in the plane perpendicular to the beam direction using primary charged tracks with p(T) > 0.5 GeV/c in vertical bar eta vertical bar < 0.8. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity (N-ch) is reported for events with different p(T) scales ("soft" and "hard") defined by the transverse momentum of the leading particle. In addition, the mean charged particle transverse momentum versus multiplicity is presented for the different event classes, and the sphericity distributions in bins of multiplicity are presented. The data are compared with calculations of standard Monte Carlo event generators. The transverse sphericity is found to grow with multiplicity at all collision energies, with a steeper rise at low N-ch, whereas the event generators show an opposite tendency. The combined study of the sphericity and the mean p(T) with multiplicity indicates that most of the tested event generators produce events with higher multiplicity by generating more back-to-back jets resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with tune PERUGIA-2011 exhibits a noticeable improvement in describing the data, compared to the other tested generators.
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