η meson production of high-energy nuclear collisions at NLO

Abstract

The transverse momentum spectrum of η meson in relativistic heavy-ion collisions is studied at the Next-to-Leading Order (NLO) within the perturbative QCD, where the jet quenching effect in the QGP is incorporated with the effectively medium-modified η fragmentation functions using the higher-twist approach. We show that the theoretical simulations could give nice descriptions of PHENIX data on η meson in both p+p and central Au+Au collisions at the RHIC, and also provide numerical predictions of η spectra in central Pb + Pb collisions with √ sNN = 2.76 TeV at the LHC.The ratios of η/π 0 in p + p and in central Au + Au collisions at 200 GeV are found to overlap in a wide pT region, which matches well the measured ratio η/π 0 by PHENIX. We demonstrate that, at the asymptotic region when pT → ∞ the ratios of η/π 0 in both Au + Au and p + p are almost determined only by quark jets fragmentation and thus approach to the one in e + e − scattering; in addition, the almost identical gluon (quark) contribution fractions to η and to π result in a rather moderate variation of η/π 0 distribution at intermediate and high pT region in A + A relative to that in p+p; while a slightly higher η/π 0 at small pT in Au+Au can be observed due to larger suppression of gluon contribution fraction to π 0 as compared to the one to η. The theoretical prediction for η/π 0 at the LHC has also been presented. PACS numbers: 12.38.Mh; 25.75.-q; 13.85.NiThe strong suppression of single hadron production at large transverse momentum [1,2] has provided the convincing evidence of the jet quenching phenomena discovered in relativistic heavy-ion collisions (HIC) [3]. Extensive phenomenological investigations [4-9] and experimental measurements [10-16] on the suppression of single hadron spectra at high p T have been carried out at both the RHIC and the LHC. As the first observable of jet quenching phenomena, the yield suppression of inclusive hadrons is arguably the most thoroughly studied quantity of jet quenching, and provides an indispensible tool to extract the properties of the hot medium created in nucleus-nucleus collisions by comparing theoretical calculations with experimental measurements, such as the jet transport coefficientq [17]. The interplay between theory and experiment on the single hadron production will help constraining the longitudinal distribution of parton energy loss in hot/dense QCD medium, and better understanding the jet-medium interactions after being combined with studies of full jets which also shed light on the angular distribution of the medium-induced gluon radiation and thus constrain the transverse distribution of parton energy loss as well [18][19][20][21][22][23].So far, most of the theoretical calculations on single hadron productions in HIC focus on π meson or charged hadrons (where π also giving a predominant contribu- * tion), and there are very few studies on other identified hadrons [24][25][26][27]. We note that η meson is the second important source of decay electrons and photons just after the π 0 , and...

Neutral meson production measurements with the ALICE at the LHC

“…9, the η/π 0 ratio is compared to the corresponding measurement in pp collisions at √ s = 7 TeV (left panel), to the pQCD predictions (middle panel, [2]) and to the ratio K ± /π ± at the same centre-of-mass energy (right panel, [14]). A similar magnitude for the ratio is observed in both pp and Pb−Pb collisions, consistent with pQCD within the current experimental uncertainties [11].…”

“…Due to the different color factor, gluons suffer a larger energy loss in the medium than quarks. This effect together with the different relative contribution of quarks and gluons to the π 0 and η production, lead to differences in the suppression pattern of the two particles [2,3]. On the other hand, at p T 5 GeV/c hadron production results from the hadronization of partons created in the initial hard scattering.…”

Measurement of neutral mesons in pp and Pb–Pb collisions at mid-rapidity with ALICE

“…Due to the different color factors of quark-gluon vertex and gluon-gluon vertex it is predicted that gluons will suffer a larger arXiv:1512.05250v1 [nucl-ex] 16 Dec 2015 energy loss in the medium than quarks. This difference in parton energy loss, together with their relative contribution to π 0 and η production may give rise to differences in suppression patterns between π 0 and η [2,3]. At high p T (p T 5 GeV/c), hadron production results from the hadronization of partons created in initial hard scattering.…”

Direct Photon and Neutral Mesons Measurements with the ALICE Detector

“…The measured η/π 0 production ratios in Pb-Pb collisions for two centrality classes shown in Fig. 5 are compared to the pp result at √ s = 7 TeV [8], a theory prediction based on NLO and jet quenching [2] and K ± /π ± result [17] at the same collision energy and centrality. The η/π 0 ratio is flat above p T = 4 GeV/c.…”

“…Gluons will suffer a larger energy loss in the medium than quarks due to the different color factor in a gluon-gluon and a quark-gluon vertex. This fact together with a different relative contribution of quarks and gluons to the light meson production may lead to differences in the suppression pattern of π 0 and η mesons [2,3]. The light meson production at high p T (p T > 5 GeV/c) results from hadronization of partons produced in the hard scattering.…”