| 41. |
- Adolfsson, J., et al.
(författare)
-
SAMPA Chip : The New 32 Channels ASIC for the ALICE TPC and MCH Upgrades
- 2017
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 12:4
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the test results of the second prototype of SAMPA, the ASIC designed for the upgrade of read-out front end electronics of the ALICE Time Projection Chamber (TPC) and Muon Chamber (MCH). SAMPA is made in a 130 nm CMOS technology with 1.25 V nominal voltage supply and provides 32 channels, with selectable input polarity, and three possible combinations of shaping time and sensitivity. Each channel consists of a Charge Sensitive Amplifier, a semi-Gaussian shaper and a 10-bit ADC; a Digital Signal Processor provides digital filtering and compression capability. In the second prototype run both full chip and single test blocks were fabricated, allowing block characterization and full system behaviour studies. Experimental results are here presented showing agreement with requirements for both the blocks and the full chip.
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| 42. |
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| 43. |
- Adare, A., et al.
(författare)
-
Measurement of parity-violating spin asymmetries in W ± production at midrapidity in longitudinally polarized p +p collisions
- 2016
-
Ingår i: Physical Review D. - 2470-0010. ; 93:5
-
Tidskriftsartikel (refereegranskat)abstract
- We present midrapidity measurements from the PHENIX experiment of large parity-violating single-spin asymmetries of high transverse momentum electrons and positrons from W±/Z decays, produced in longitudinally polarized p+p collisions at center of mass energies of s=500 and 510 GeV. These asymmetries allow direct access to the antiquark polarized parton distribution functions due to the parity-violating nature of the W-boson coupling to quarks and antiquarks. The results presented are based on data collected in 2011, 2012, and 2013 with an integrated luminosity of 240 pb-1, which exceeds previous PHENIX published results by a factor of more than 27. These high Q2 data probe the parton structure of the proton at W mass scale and provide an important addition to our understanding of the antiquark parton helicity distribution functions at an intermediate Bjorken x value of roughly MW/s=0.16.
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| 44. |
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| 45. |
- Aidala, C., et al.
(författare)
-
Measurement of long-range angular correlations and azimuthal anisotropies in high-multiplicity p+Au collisions at s NN =200 GeV
- 2017
-
Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 95:3
-
Tidskriftsartikel (refereegranskat)abstract
- We present measurements of long-range angular correlations and the transverse momentum dependence of elliptic flow v2 in high-multiplicity p+Au collisions at sNN=200 GeV. A comparison of these results to previous measurements in high-multiplicity d+Au and He3+Au collisions demonstrates a relation between v2 and the initial collision eccentricity 2, suggesting that the observed momentum-space azimuthal anisotropies in these small systems have a collective origin and reflect the initial geometry. Good agreement is observed between the measured v2 and hydrodynamic calculations for all systems, and an argument disfavoring theoretical explanations based on initial momentum-space domain correlations is presented. The set of measurements presented here allows us to leverage the distinct intrinsic geometry of each of these systems to distinguish between different theoretical descriptions of the long-range correlations observed in small collision systems.
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| 46. |
- Aidala, C., et al.
(författare)
-
Measurements of B →j /ψ at forward rapidity in p+p collisions at s =510 GeV
- 2017
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 2470-0010. ; 95:9
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first measurement of the fraction of J/ψ mesons coming from B-meson decay (FB→J/ψ) in p+p collisions at s=510 GeV. The measurement is performed using the forward silicon vertex detector and central vertex detector at PHENIX, which provide precise tracking and distance-of-closest-approach determinations, enabling the statistical separation of J/ψ due to B-meson decays from prompt J/ψ. The measured value of FB→J/ψ is 8.1%±2.3%(stat)±1.9%(syst) for J/ψ with transverse momenta 0
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| 47. |
- Adare, A, et al.
(författare)
-
Dielectron production in Au plus Au collisions at root s(NN)=200 GeV
- 2016
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 93:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present measurements of e+e- production at midrapidity in Au+Au collisions at sNN=200 GeV. The invariant yield is studied within the PHENIX detector acceptance over a wide range of mass (mee<5 GeV/c2) and pair transverse momentum (pT<5 GeV/c) for minimum bias and for five centrality classes. The e+e- yield is compared to the expectations from known sources. In the low-mass region (mee=0.30-0.76 GeV/c2) there is an enhancement that increases with centrality and is distributed over the entire pair pT range measured. It is significantly smaller than previously reported by the PHENIX experiment and amounts to 2.3±0.4(stat)±0.4(syst)±0.2(model) or to 1.7±0.3(stat)±0.3(syst)±0.2(model) for minimum bias collisions when the open heavy-flavor contribution is calculated with pythia or mc@nlo, respectively. The inclusive mass and pT distributions, as well as the centrality dependence, are well reproduced by model calculations where the enhancement mainly originates from the melting of the ρ meson resonance as the system approaches chiral symmetry restoration. In the intermediate-mass region (mee=1.2-2.8 GeV/c2), the data hint at a significant contribution in addition to the yield from the semileptonic decays of heavy-flavor mesons.
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| 48. |
- Adare, A, et al.
(författare)
-
Measurement of the relative yields of ψ(2S) to ψ(1S) mesons produced at forward and backward rapidity in p+p, p+Al, p+Au, and He 3 +Au collisions at s NN =200 GeV
- 2017
-
Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 95:3
-
Tidskriftsartikel (refereegranskat)abstract
- The PHENIX Collaboration has measured the ratio of the yields of ψ(2S) to ψ(1S) mesons produced in p+p, p+Al, p+Au, and He3+Au collisions at sNN=200 GeV over the forward and backward rapidity intervals 1.2<|y|<2.2. We find that the ratio in p+p collisions is consistent with measurements at other collision energies. In collisions with nuclei, we find that in the forward (p-going or He3-going) direction, the relative yield of ψ(2S) mesons to ψ(1S) mesons is consistent with the value measured in p+p collisions. However, in the backward (nucleus-going) direction, the ψ(2S) meson is preferentially suppressed by a factor of ∼2. This suppression is attributed in some models to the breakup of the weakly bound ψ(2S) meson through final-state interactions with comoving particles, which have a higher density in the nucleus-going direction. These breakup effects may compete with color screening in a deconfined quark-gluon plasma to produce sequential suppression of excited quarkonia states.
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| 49. |
- Adare, A., et al.
(författare)
-
Measurements of mass-dependent azimuthal anisotropy in central p + Au, d + Au, and He 3 + Au collisions at sNN =200 GeV
- 2018
-
Ingår i: Physical Review C. - 2469-9985. ; 97:6
-
Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the transverse-momentum dependence of elliptic flow v2 for identified pions and (anti)protons at midrapidity (|η|<0.35), in 0%-5% central p+Au and He3+Au collisions at sNN=200 GeV. When taken together with previously published measurements in d+Au collisions at sNN=200 GeV, the results cover a broad range of small-collision-system multiplicities and intrinsic initial geometries. We observe a clear mass-dependent splitting of v2(pT) in d+Au and He3+Au collisions, just as in large nucleus-nucleus (A+A) collisions, and a smaller splitting in p+Au collisions. Both hydrodynamic and transport model calculations successfully describe the data at low pT (<1.5GeV/c), but fail to describe various features at higher pT. In all systems, the v2 values follow an approximate quark-number scaling as a function of the hadron transverse kinetic energy per constituent quark (KET/nq), which was also seen previously in A+A collisions.
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| 50. |
- D., Adamová, et al.
(författare)
-
Production of Σ (1385) ± and Ξ (1530) 0 in p–Pb collisions at √sNN=5.02 TeV
- 2017
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:6
-
Tidskriftsartikel (refereegranskat)abstract
- The transverse momentum distributions of the strange and double-strange hyperon resonances (Σ (1385) ±, Ξ (1530) 0) produced in p–Pb collisions at sNN=5.02 TeV were measured in the rapidity range - 0.5 < yCMS< 0 for event classes corresponding to different charged-particle multiplicity densities, ⟨ dNch/dηlab⟩. The mean transverse momentum values are presented as a function of ⟨ dNch/dηlab⟩ , as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of ⟨ dNch/dηlab⟩. The equivalent ratios to pions exhibit an increase with ⟨ dNch/dηlab⟩ , depending on their strangeness content.
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