arXivDaily arXiv每日学术速递 周一至周五更新
北美退伍军人节(Veterans Day),12 日无更新
arXiv 1208.1874nucl-exhep-phnucl-th
收藏

用ATLAS探测器测量Pb-Pb碰撞中的快偶极流

Measurement of the rapidity-even dipolar flow in Pb-Pb collisions with the ATLAS detector

Jiangyong Jia

摘要:

在横向动量0.5 GeV<pT<9 GeV的宽范围内测量了与初始几何中偶极不对称性相关的快偶极流v1,并在sqrt(s_NN)=2.76 TeV的Pb-Pb碰撞中测量了中心度(0-50)%,这是由ATLAS实验在LHC记录的。v1系数通过两个分量拟合一阶傅里叶系数确定,v_{1,1} = cos Δ Δ τ,两个粒子在方位角Δ τ = π_a-π_b中的相关性是pT^a和pT^b的函数。这种拟合的动机是发现v_{1,1}(pT^a,pT^b)数据的pT依赖性与速度偶v1和整体动量守恒的组合贡献一致。提取的动量守恒分量的大小表明,动量守恒系统只涉及事件的一个子集(在中心碰撞中跨越约3个η单位)。在pT~1.0 GeV时,v1过零,在4-5 GeV时达到最大值,其值与v3相当,在pT较高时,v1减小。有趣的是,在高pT时v1的大小超过了所有中心性区间中v3的值,并且超过了中心碰撞中v2的值。这种行为表明,从波动的能量损失和初始偶极不对称的路径长度的依赖性证实产生一个大的偶极各向异性的高pT强子,使V1的一个有价值的探针研究喷流淬灭现象。

英文摘要:

The rapidity-even dipolar flow v1 associated with dipole asymmetry in the initial geometry is measured over a broad range in transverse momentum 0.5 GeV<pT<9 GeV, and centrality (0-50)% in Pb-Pb collisions at sqrt(s_NN)=2.76 TeV, recorded by the ATLAS experiment at the LHC. The v1 coefficient is determined via a two-component fit of the first order Fourier coefficient, v_{1,1}= cos Δϕ, of two-particle correlations in azimuthal angle Δϕ=ϕ_a-ϕ_b as a function of pT^a and pT^b. This fit is motivated by the finding that the pT dependence of v_{1,1}(pT^a,pT^b) data are consistent with the combined contributions from a rapidity-even v1 and global momentum conservation. The magnitude of the extracted momentum conservation component suggests that the system conserving momentum involves only a subset of the event (spanning about 3 units in ηin central collisions). The extracted v1 is observed to cross zero at pT~1.0 GeV, reaches a maximum at 4-5 GeV with a value comparable to that for v3, and decreases at higher pT. Interestingly, the magnitude of v1 at high pT exceeds the value of the v3 in all centrality interval and exceeds the value of v2 in central collisions. This behavior suggests that the path-length dependence of energy loss and initial dipole asymmetry from fluctuations corroborate to produce a large dipolar anisotropy for high pT hadrons, making the v1 a valuable probe for studying the jet quenching phenomena.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑