· Web view2018/08/13 · 序号 代表团 领队 教练 运动员 照片 1 下城区 高嫄 范金宝 胡松松 杨晟 周石 周洋 侯苏霞 黄阳艳 钱程 张洁 周苏艳
施梳苏 华中师范大学
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Transcript of 施梳苏 华中师范大学
1 中国物理学会高能物理分会第九届全国会员代表大会暨学术年会
Observation of an Energy Dependent Difference in Elliptic Flow between Particle and Antiparticles in RHIC
施梳苏华中师范大学
晨光杯
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Introduction and Motivation
STAR detector and Data analysis
Results and Discussions v2 method comparison Energy dependence v2 of particles and anti-particles NCQ scaling test
Summary
Outline
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BES Motivations • Search for critical point• Search for phase boundary Number of Constituent Quark scaling on v2
partonic vs. hadronic degree of freedom (dof)
IntroductionThe RHIC Beam Energy Scan (BES)
STAR: PRL99, 112301 (2007) NPA830:187c-190c(2009) PHENIX: PRL98, 162301 (2007)
Data Collected in 2010:7.7 GeV11.5 GeV39 GeV
Data Collected in 2011:19.6 GeV27 GeV
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Energy Dependence of NCQ ScalingAMPT model results:Scaling in v2: partonic dof dominant; No scaling in v2 : hadronic dof dominant=>A tool to search for the possible phase boundary!
The beam energydependence of the partonic cross sections will not affect the v2 scaling argument.=>Important for Beam Energy Scan program.
F. Liu, K.J. Wu, and N. Xu: J. Phys. G 37 094029(2010)
Partonic Hadronic
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Large acceptanceTPC: Full azimuthal coverage, (|η|<1.0)
dE/dx PID: pion/kaon: pT ~ 0.6 GeV/c; proton pT ~ 1.0 GeV/cWith full TOF system since 2010pion/kaon: pT ~ 1.6 GeV/c; proton pT ~ 3.0 GeV/cStrange hadrons (KS
0, Λ, ϕ, Ξ, Ω) reconstructed by the decay topology
STAR Detectors
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Particle Identification
Energy loss (dE/dx) + TOF: charged pion, kaon and proton Decay topology: KS
0, Λ, ϕ, Ξ, Ω
Au+Au@39
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Method Comparison
v2 method• Event Plane method TPC EP (|η|<1.0) FTPC EP (2.5<|η|<4.0) BBC EP (3.8<|η|<5.2)
• Cumulant method v2{2}, v2{4}
• Different methods show different sensitivity to non-flow and fluctuations The difference between v2{2} and v2{4} decreases with decrease in beam energy • non-flow and fluctuations
20-30% Au+Au
STAR: Phys. Rev. C 86, 054908 (2012)
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v2{4} results• Three centrality bins Consistent v2(pT) from 7.7 GeV to 2.76 TeV for pT > 2 GeV/c pT< 2GeV/c• The v2 values
rise with increasing collision energy -> Large collectivity? Particle composition?
ALICE data: Phys. Rev. Lett. 105, 252302 (2010)STAR: Phys. Rev. C 86, 054908 (2012)
Energy Dependence
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π+ (K+) vs. π- (K-)
v2(π-) > v2(π+) and v2(K+)>v2(K-) in Au + Au collisions at 7.7 and 11.5 GeV Almost same magnitude of v2 at 19.6, 27, 39 and 62.4 GeV
STAR: Phys. Rev. Lett. 110, 142301(2013)Phys. Rev. C 88, 014902 (2013)
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p (Λ) vs. Anti-p (Λ)
v2(p) > v2(anti-p) at all energies, The difference is increasing as beam energydecreasing
Similar trend observed for Λ and anti-Λ
STAR: Phys. Rev. Lett. 110, 142301(2013)Phys. Rev. C 88, 014902 (2013)
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Particles vs. Anti-particles
Beam energy ≥ 39 GeV• Δv2 for baryon and anti-baryon within 10%• Almost no difference for meson Beam energy < 39 GeV• The difference of baryon and
anti-baryon v2
→ Increasing with decrease of beam energy
• v2(K+)>v2(K-) at 7.7-19.6 GeV• v2(π-) >v2(π+) at 7.7-19.6 GeV Δv2 is linearly increasing with
μB Possible explanation• Baryon transport to mid-rapidity?
ref: J. Dunlop et al., PRC 84, 044914 (2011)
• Hadronic potential? ref: J. Xu et al., PRC 85, 041901 (2012)The difference between particles and anti-particles is observed
STAR: Phys. Rev. Lett. 110, 142301(2013)Phys. Rev. C 88, 014902 (2013)
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NCQ Scaling Test: mT - m
Ref: B. Mohanty and N. Xu: J. Phys. G 36, 064022(2009)
Universal trend for most of particles and the corresponding anti-particles φ meson v2 deviates from other particles ~ 2σ at the highest pT data in
7.7 and 11.5 GeV collisions Small or zero v2 for ϕ meson -> without formation of partonic matterHadronic interactions might be dominant when √sNN ≤ 11.5 GeV
STAR: Phys. Rev. Lett. 110, 142301(2013)Phys. Rev. C 88, 014902 (2013)
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Charged hadrons The v2{4} values for fixed pT rise with increasing collision energy for pT< 2 GeV/c
-> Larger collectivity? Particle composition? Consistent v2{4}(pT) from 7.7 GeV to 2.76 TeV for pT > 2 GeV/c
The difference between particles and anti-particles increases with decrease of beam energy NCQ scaling broken between particles and anti-particles ϕ meson deviates the trend of other particles ~2σ at the
highest pT data in 7.7 and 11.5 GeV collisions
Hadronic interactions is dominant at lower energies
Summary