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arXiv 1012.1004nucl-ex
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$\sqrt{s_{\rm NN}} = 2.76$ TeV中心碰撞中大横动量带电粒子产生的抑制

Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV

ALICE Collaboration

摘要:

在LHC的ALICE合作组中,测量了$\sqrt{s_{_{\rm NN}}}$ = 2.76TeV的Pb-Pb碰撞中初级带电粒子的包含横动量谱。给出了中心碰撞和外围碰撞的数据,分别占强子Pb-Pb碰撞截面的0-5%和70-80%。在$|η|<0.8$和$0.3 < p_T < 20$ GeV/ $c$中测量的带电粒子谱与在相同$\sqrt{s_{\rm NN}}$的pp碰撞中的预期进行比较,由基础核子-核子碰撞的数量缩放。比较用核修饰因子$R_{\rm AA}$表示。结果表明,在外围碰撞中,只有弱的介质效应($R_{\rm AA} \approx $ 0.7).在中心碰撞中,$R_{\rm AA}$在$p_{\rm T}=6$-7 GeV/ $c$处达到约0.14的最小值,并且在较大的$p_{\rm T}$处显著增加。高$p_{\rm T}$粒子的测量抑制比在较低的碰撞能量下观察到的更强,表明在LHC中心Pb-Pb碰撞中形成了非常致密的介质。

英文摘要:

Inclusive transverse momentum spectra of primary charged particles in Pb-Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV have been measured by the ALICE Collaboration at the LHC. The data are presented for central and peripheral collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross section. The measured charged particle spectra in $|η|<0.8$ and $0.3 < p_T < 20$ GeV/$c$ are compared to the expectation in pp collisions at the same $\sqrt{s_{\rm NN}}$, scaled by the number of underlying nucleon-nucleon collisions. The comparison is expressed in terms of the nuclear modification factor $R_{\rm AA}$. The result indicates only weak medium effects ($R_{\rm AA} \approx $ 0.7) in peripheral collisions. In central collisions, $R_{\rm AA}$ reaches a minimum of about 0.14 at $p_{\rm T}=6$-7GeV/$c$ and increases significantly at larger $p_{\rm T}$. The measured suppression of high-$p_{\rm T}$ particles is stronger than that observed at lower collision energies, indicating that a very dense medium is formed in central Pb-Pb collisions at the LHC.

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