Measurement of hadron suppression and study of its connection with vanishing v₃ at low in Au + Au collisions with STAR

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• 作者：Stephen. Horvat ; for the STAR Collaboration¹
• 关键词：Hadron suppression ; nuclear modification factor ; flow ; ridge ; QGP signatures ; BES ; Beam Energy Scan ; STAR
• 刊名：Nuclear Physics A
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：956
• 期：Complete
• 页码：838-841
• 全文大小：512 K

文摘

At top RHIC and LHC energies the suppression of high transverse momentum (p_T) hadrons provides evidence for partonic energy loss in QGP. We study partonic energy loss in the RHIC Beam Energy Scan (BES) by investigating the centrality dependence of the binary-collision-scaled high-p_T yields. Observing a decrease of the scaled yield in more central collisions is proposed as a possible signature for jet quenching. Even at energies and centralities where this signature is lost a QGP may still be formed since competing phenomena responsible for enhancements may overwhelm the suppression from energy loss. Measurements in several ranges of p_T from the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0375947416300379&_mathId=si2.gif&_user=111111111&_pii=S0375947416300379&_rdoc=1&_issn=03759474&md5=8b071bd0a3e6d34a3bc55b12f67fa125">the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0375947416300379-si2.gif">$\sqrt{s_{\mathrm{NN}}}=7.7,11.5,14.5,19.6,27,39,62.4$, and 200 GeV data show that relative hadron suppression persists at least down to 14.5 GeV.

To further investigate both the possible formation of a QGP at these lower energies and whether the observed hadron suppression coincides with the onset of other QGP signatures, we examine the energy and centrality dependence of v₃. Models have shown that the development of v₃ requires the presence of a low viscosity phase early in the collision. We find that for collisions with formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0375947416300379&_mathId=si3.gif&_user=111111111&_pii=S0375947416300379&_rdoc=1&_issn=03759474&md5=d51aeacccbe6640eaa7cf6cdd3b17395" title="Click to view the MathML source">N_part<50$N_{part}<50$, v₃ disappears for energies below 14.5 GeV, suggestive of a turn-off of the QGP. But for formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0375947416300379&_mathId=si3.gif&_user=111111111&_pii=S0375947416300379&_rdoc=1&_issn=03759474&md5=d51aeacccbe6640eaa7cf6cdd3b17395" title="Click to view the MathML source">N_part<50$N_{part}<50$, v₃ persists down to the lowest energies. Together, these signatures provide possible evidence for the formation of a QGP in the lowest energy collisions at RHIC.