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![Nuclear modification factors RCP for π + + π − and p + ¯ p in 200 GeV Au+Au collisions. The point-to-point systematic uncertainties are shown as the shaded boxes around the data points. The dark shaded bands show the normalization systematic uncertainty in the number of binary collisions. The solid lines show jet quenching predictions for pions [27].](profile/Lee-Barnby/publication/6644615/figure/fig2/AS:669272565096470@1536578422521/Nuclear-modification-factors-RCP-for-p-p-and-p-p-in-200-GeV-Au-Au-collisions.png)
Nuclear modification factors RCP for π + + π − and p + ¯ p in 200 GeV Au+Au collisions. The point-to-point systematic uncertainties are shown as the shaded boxes around the data points. The dark shaded bands show the normalization systematic uncertainty in the number of binary collisions. The solid lines show jet quenching predictions for pions [27].
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![FIG. 4: The p/π + and ¯ p/π − ratios from d+Au [21, 22] and Au+Au...](profile/Lee-Barnby/publication/6644615/figure/fig4/AS:669272565088269@1536578422553/The-p-p-and-p-p-ratios-from-d-Au-21-22-and-Au-Au-collisions-at-sNN-200-GeV_Q320.jpg)
Transverse momentum spectra of pi+/-, p, and p up to 12 GeV/c at midrapidity in centrality selected Au + Au collisions at square root sNN=200 GeV are presented. In central Au + Au collisions, both pi +/- and p(p) show significant suppression with respect to binary scaling at pT approximately >4 GeV/c. Protons and antiprotons are less suppressed tha...
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... to momentum resolution (0-5%) and half of the difference between the two methods to extract the proton yields (3-6%). The systematic errors are added in quadrature. The spectra from the TOFr and TPC mea- surements agree within systematic errors in the overlap- ping p T region. The correlations of the systematic errors on the particle ratios in Fig. 2, 3 and 4 are properly taken into ...
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... Fig. 2 shows pion (π + + π − ) and proton (p + ¯ p) R CP for Au+Au collisions. In 0-12% central Au+Au colli- sions, the pion yield shows strong suppression with R CP between 0.2 and 0.4 at p T > ∼ 3 GeV/c. This is consis- tent with the jet quenching calculation shown in Fig. 2 (a) [27]. For each centrality, the R CP values for protons peak at ...
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... Fig. 2 shows pion (π + + π − ) and proton (p + ¯ p) R CP for Au+Au collisions. In 0-12% central Au+Au colli- sions, the pion yield shows strong suppression with R CP between 0.2 and 0.4 at p T > ∼ 3 GeV/c. This is consis- tent with the jet quenching calculation shown in Fig. 2 (a) [27]. For each centrality, the R CP values for protons peak at p T ∼ 2-3 GeV/c. At intermediate p T , p and ¯ p are less suppressed, with respect to binary scaling, than π ± , but a significant suppression is still observed in central Au+Au collisions. This is in contrast to nuclear mod- ification factors in d+Au collisions, where ...
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... results in Fig. 2 clearly show different R CP for pro- tons and pions at intermediate p T . A similar effect has been observed for K 0 S and Λ [9], with K 0 S (Λ) R CP simi- lar to pion (proton) R CP . The grouping of particle pro- duction according to the number of constituent quarks has been attributed to quark coalescence at hadroniza- tion from a ...
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... This is in agreement with AKK fragmentation functions [15] which describe the STAR data in p+p col- lisions [22], showing that gluon fragmentation contributes to 40% of pion production at p T ≃ 10 GeV/c while more than 80% of p + ¯ p are from gluon fragmentation. At high p T , the nuclear modification factor of protons is similar to that of pions (Fig. 2) and the p/π + , ¯ p/π − , and ¯ p/p ratios in central Au+Au collisions are similar to those in p+p and d+Au collisions [22]. These observa- tions indicate that at sufficiently high p T , fragmentation in central Au+Au and p+p events is similar and that there is no evidence of different energy loss for quarks and gluons in the medium. ...
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Citations
... In this paper, to extract kinetic freeze-out temperature and radial flow velocity, we use blast-wave model with Tsallis statistics [21][22][23] and compare to Boltzmann-Gibbs statistics one [1,24,25] to simultaneously fit all the transverse momentum spectra of hadrons produced at mid-(pseudo)rapidity in √ s NN = 7.7, 11.5, 14. 5, 19.6, 27, 39, 62. 4 and 200 GeV Au + Au collisions at RHIC [17,24,[26][27][28][29][38][39][40][41][42][43][44] and in √ s NN = 2.76 TeV [30] and 5.02 TeV [31] Pb + Pb collisions at the LHC. Such a systematic study on collision energy and centrality dependence of radial flow velocity, kinetic freeze-out temperature and the degree of non-equilibrium from RHIC to the LHC energy range may shed light on the underlying physics in these collisions. ...
... The difference between our results at 200 GeV from previous ones is because that more data points at 2 GeV/c pT 3 GeV/c are available now and are thus used in fitting, mainly K ± from PHENIX [42] which provides better constraint on q, while data for K ± used in Ref. [21] is only at pT 0.8 GeV/c and data for K ± used in Ref. [22] is only at pT 2 GeV/c. a The measurements of π ± , p andp for centrality 0-12% [29] are used as 0-10%. Λ,Λ, Ξ + , Ξ − and Ω for centrality 0-5% [43] are used as 0-10%. ...
In this paper, we investigate the kinetic freeze-out properties in relativistic heavy ion collisions at different collision energies. We present a study of standard Boltzmann-Gibbs Blast-Wave (BGBW) fits and Tsallis Blast-Wave (TBW) fits performed on the transverse momentum spectra of identified hadrons produced in Au + Au collisions at collision energies of 7.7 - 200 GeV at Relativistic Heavy Ion Collider (RHIC), and in Pb + Pb collisions at collision energies of 2.76 and 5.02 TeV at the Large Hadron Collider (LHC). The behavior of strange and multi-strange particles is also investigated. We found that the TBW model describes data better than the BGBW one overall, and the contrast is more prominent as the collision energy increases as the degree of non-equilibrium of the produced system is found to increase. From TBW fits, the kinetic freeze-out temperature at the same centrality shows a weak dependence of collision energy between 7.7 and 39 GeV, while it decreases as collision energy continues to increase up to 5.02 TeV. The radial flow is found to be consistent with zero in peripheral collisions at RHIC energies but sizable at LHC energies and central collisions at all RHIC energies. We also observed that the strange hadrons, with higher temperature and similar radial flow, approach equilibrium more quickly from peripheral to central collisions than light hadrons. The dependence of temperature and flow velocity on non-equilibrium parameter () is characterized by two second-order polynomials. Both a and from the polynomials fit, related to the influence of the system bulk viscosity, increases toward lower RHIC energies.
... The fits of the p T spectra of π − distributions have turned out to be of similar quality as of the π + distributions. and 200 GeV from STAR [41,42] experiment with the available p T ranges up to 10 GeV/c and 12 GeV/c, respectively. The left panels of the figure show the fits of the p T range up to 2 GeV/c and the right panels provide the Tsallis fitting of the entire p T spectrum. ...
... - Fig. 4 Tsallis parameters, q, T , and the normalization factor, V as a function of number of participants, N part , obtained by fitting the p T spectra up to 2 GeV/c for π + at RHIC energies from STAR [15,16,41,42], and PHENIX [37], and all charged pions at LHC energies from ALICE [19,38]. ...
... (GeV) s different centralities obtained by fitting the p T spectra up to 2 GeV/c for π + at RHIC energies from STAR [15,16,41,42], and PHENIX [37], and all charged pions at LHC energies from ALICE [19,38]. PHENIX results are shifted to right for clarity. ...
The thermodynamical properties of matter created in high-energy heavy-ion collisions have been studied in the framework of the non-extensive Tsallis statistics by fitting the transverse momentum spectra (pT) of produced particles. The pT distributions of charged particles and identified pions from the available experimental data of Au-Au collisions at the Relativistic Heavy Ion Collider (RHIC) energies and Pb-Pb collisions at the Large Hadron Collider (LHC) energies are fitted by Tsallis distribution. The fit parameter q measures the degree of deviation of the system from an equilibrium state and T is the kinetic freeze-out temperature. It is observed that, in general, q increases with the increase of collision energy and the variation with respect to centrality is collision energy dependent, whereas, T decreases with collision energy, and increases with collision centrality. A reversal of the centrality dependency has been observed for collision energies below 27 GeV. The correlation between the Tsallis parameters with centrality and collision energy are presented along with a comparison to the corresponding results from the fits of the blast-wave model.
... The single particle spectra, d 2 N/dydp T , carry equivalent information, enabling a cross check between experiments. We use a method similar to the calculation of E T from spectra in [6] to calculate E T from previously published STAR spectra [7][8][9][10][11][12][13]. We define E T to be what would be measured in a calorimeter ...
... The STAR (anti)proton spectra do not include corrections for feeddown from the (anti)lambda decay Λ → pπ − . To avoid double counting, we estimate feeddown using the proton spectra with and without feeddown corrections reported in [12] for Au+Au collisions at √ s NN = 200 GeV. We calculate the fraction of E T carried by protons from Λ decays as ...
In high energy heavy ion collisions, measurements of transverse energy ( E T ) can constrain the initial energy density and therefore provide insight into the formation of the Quark Gluon Plasma (QGP). This is particularly interesting in regions where it is unclear if the QGP is formed. The E T in a collision can be measured either from a calorimeter or calculated from the single particle momentum spectra. We use spectra measured by the STAR collaboration to calculate the transverse energy in heavy ion collisions in Au+Au collisions at S NN = 7.7 − 200 GeV . These calculations are compared to PHENIX measurements using a calorimeter.
... The exploration of the QCD phase diagram, in the plane of temperature (T ) and the baryon chemical potential (µ B ), is one of the primary objectives of high-energy heavy-ion collision experiments [1][2][3][4][5][6][7]. During the initial stages of Au+Au collisions at top RHIC energies, there is evidence of a phase with partonic degrees of freedom [1][2][3][4][8][9][10][11][12][13], which later transits into one with hadronic degrees of freedom [14][15][16][17]. Relevant evidence includes strong suppression of high transverse momentum (p T ) hadron production in Au+Au collisions relative to p + p collisions [1][2][3][4][8][9][10][11], large elliptic flow (v 2 ) for hadrons containing light as well as strange and charm valence quarks, and the difference between baryon and meson v 2 at intermediate p T [18]. ...
... During the initial stages of Au+Au collisions at top RHIC energies, there is evidence of a phase with partonic degrees of freedom [1][2][3][4][8][9][10][11][12][13], which later transits into one with hadronic degrees of freedom [14][15][16][17]. Relevant evidence includes strong suppression of high transverse momentum (p T ) hadron production in Au+Au collisions relative to p + p collisions [1][2][3][4][8][9][10][11], large elliptic flow (v 2 ) for hadrons containing light as well as strange and charm valence quarks, and the difference between baryon and meson v 2 at intermediate p T [18]. ...
We report systematic measurements of bulk properties of the system created in Au+Au collisions at = 14.5 GeV recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC).The transverse momentum spectra of , and are studied at mid-rapidity () for nine centrality intervals. The centrality, transverse momentum (),and pseudorapidity () dependence of inclusive charged particle elliptic flow (), and rapidity-odd charged particles directed flow () results near mid-rapidity are also presented. These measurements are compared with the published results from Au+Au collisions at other energies, and from Pb+Pb collisions at = 2.76 TeV. The results at = 14.5 GeV show similar behavior as established at other energies and fit well in the energy dependence trend. These results are important as the 14.5 GeV energy fills the gap in , which is of the order of 100 MeV,between =11.5 and 19.6 GeV. Comparisons of the data with UrQMD and AMPT models show poor agreement in general.
... R CP of strange hadrons in the BES, together with other non-strange hadron suppression results, can potentially pin down the beam energy at which energy loss to the medium begins to dominate hard parton interactions [3]. At intermediate p T (2)(3)(4)(5) GeV/c), as first discovered in central Au+Au events at RHIC [37,[47][48][49] and later observed at the Large Hadron Collider [39,50], the p/π and Λ/K 0 S ratios are larger than unity and much higher than those observed in peripheral A+A and in p+p collisions. These results may indicate different hadronization mechanisms in this p T range in A+A collisions. ...
We present STAR measurements of strange hadron (, , , , , , , and ) production at mid-rapidity () in Au+Au collisions at = 7.7 - 39 GeV from the Beam Energy Scan Program at the Relativistic Heavy Ion Collider (RHIC). Transverse momentum spectra, averaged transverse mass, and the overall integrated yields of these strange hadrons are presented versus the centrality and collision energy. Antibaryon-to-baryon ratios (/, /, /) are presented as well, and used to test a thermal statistical model and to extract the temperature normalized strangeness and baryon chemical potentials at hadronic freeze-out ( and ) in central collisions. Strange baryon-to-pion ratios are compared to various model predictions in central collisions for all energies. The nuclear modification factors () and antibaryon-to-meson ratios as a function of transverse momentum are presented for all collision energies. The shows no suppression for up to 3.5 at energies of 7.7 and 11.5 GeV. The / ratio also shows baryon-to-meson enhancement at intermediate (2.5 ) in central collisions at energies above 19.6 GeV. Both observations suggest that there is likely a change of the underlying strange quark dynamics at collision energies below 19.6 GeV.
... Meanwhile, the R AA for different final-state identified hadrons have been measured, and their production suppressions as well as patterns of their yield ratios have been observed [4,5,[11][12][13][14][15][16]. It is of interest and it is a challenge to describe the cross sections of leading hadrons of different types and their yield ratios with each other in heavy-ion collisions (HIC) both at RHIC and LHC with a unified model of jet quenching, which should shed light on the flavor dependence of the parton energy loss and the intrinsic properties of the identified hadron productions in p+p and A+A reactions [17][18][19][20][21][22][23][24]. ...
In this work, we pave the way to calculate the productions of and mesons with large in p+p and A+A collisions both at RHIC and LHC. The fragmentation functions (FFs) of the meson in vacuum at next-to-leading order (NLO) are obtained by evolving the NLO DGLAP evolution equations with rescaled FFs at initial scale from a broken SU(3) model, and the FFs of in vacuum are taken from AKK08 parametrization directly. Within the framework of the NLO pQCD improved parton model, we arrive at good descriptions of the experimental data on and in p+p both at RHIC and LHC. With the higher-twist approach, to take into account jet quenching effect by medium-modified FFs, nuclear modification factors for meson and meson both at RHIC and LHC are presented with different sets of jet transport coefficients . Then we make a global extraction of both at RHIC and LHC by confronting our model calculations with all available data on six identified mesons: , , , , , and . The minimum value of total for productions of these mesons gives the best value of for Au+Au collisions with GeV at RHIC, and for Pb+Pb collisions with TeV at LHC, respectively, with the QGP spacetime evolution given by the event-by-event viscous hydrodynamics model IEBE-VISHNU. With these global extracted values of , nuclear modification factors of , , , , , and in A+A collisions are presented, and predictions of yield ratios such as and at the high- regime in heavy-ion collisions both at RHIC and LHC are provided.
... An accurate calculation of the contribution of this mechanism to the baryon production in AA collisions is impossible. But qualitative analysis performed in [24] indicates that this mechanism may give a considerable contribution to the anomalous baryon production at intermediate p T observed in AA collisions at RHIC and LHC [30][31][32]. The calculations of [24] have been performed under assumption of a fast randomization of the two-parton states in the QGP. ...
... the dipole cross section for the color singlet state reads (28) where m D is the Debye mass, C T and C R are the color Casimir operators for the QGP constituent and the multiplet R. The SU (3) Casimir operators that we need read: C 1 = 0, C 8 = N c , C 10 = 2N c , C 27 = 2(N c + 1). The six eigenstates of the diffraction operator in the schannel basis can be obtained by acting with the crossing matrix U st on the t-channel states (29) For each eigenstate the medium effect is reduced to trivial multiplication by the Glauber attenuation factor (30) where z s is the longitudinal coordinate of the g → gg splitting, R is the multiplet entering the t-channel state. The eigenstate corresponding to the state |(8 A 8 S ) + t in terms of the s-channel basis is (|10 -| 10)/ , i.e., it describes the difference between the probabilities for the decuplet P 10 and the antidecuplet states . ...
... In our calculations the properties of the QGP enter only through the product of the number density of the QGP and the dipole cross section in the formula for the Glauber attenuation factors (30). Since the dipole cross section is proportional to the Casimir operator of the scattering center, in this product one can avoid summing over the species of the QGP constituents by using the dipole cross section for scattering on a quark and using, at the same time, for the number density of the color centers the sum n = n q + n g C A /C F (here n q is the number density of quarks and antiquarks, and n g is the number density of gluons, C A and C F are the gluon and quark Casimir operators). ...
We study the color randomization of two-gluon states produced after splitting of a primary fast gluon in the quark-gluon plasma. We find that for the LHC conditions the color randomization of the gg pairs is rather slow. At jet energies E = 100 and 500 GeV, for typical jet path length in the plasma in central Pb+Pb collisions, the SU(3)-multiplet averaged color Casimir operator of the gg pair differs considerably from its value 2Nc for a fully randomized gg state. Our calculations of the energy dependence for generation of the nearly collinear decuplet gg states, that can lead to the baryon jet fragmentation, show that the contribution of the anomalous decuplet color states to the baryon production should become small at pT ≳ 10 GeV.
... Meanwhile, the R AA for different final state identified hadrons have been measured, and their production suppressions as well as patterns of their yield ratios have been observed [4,5,10,11,12,13,14,15]. It is of interest and challenge to describe the cross sections of leading hadron of different types and their yield ratios with each other in heavy-ion collisions (HIC) at the RHIC and the LHC with a unified model of jet quenching, which should shed light on flavor dependence of parton energy loss and the intrinsic properties of identified hadron productions in p+p and A+A reactions [16,17,18,19,20,21,22,23]. ...
In this work, we pave the way to calculate the productions of and mesons at large in p+p and A+A collisions at the RHIC and the LHC. The meson fragmentation functions (FFs) in vacuum at next-to-leading order (NLO) are obtained by evolving NLO DGLAP evolution equations with rescaled FFs at initial scale GeV from a broken SU(3) model, and the FFs in vacuum are taken from AKK08 parametrization directly. Within the framework of the NLO pQCD improved parton model, we make good descriptions of the experimental data on and in p+p both at the RHIC and the LHC. With the higher-twist approach to take into account the jet quenching effect by medium modified FFs, the nuclear modification factors for meson and meson at the RHIC and the LHC are presented with different sets of jet transport coefficient . Then we make a global extraction of at the RHIC and the LHC by confronting our model calculations with all available data on 6 identified mesons: , , , , , and . The minimum value of the total for productions of these mesons gives the best value of for Au+Au collisions with GeV at the RHIC, and for Pb+Pb collisions with TeV at the LHC respectively, with the QGP spacetime evolution given by an event-by-event viscous hydrodynamics model IEBE-VISHNU. With these global extracted values of , the nuclear modification factors of , , , , , and in A+A collisions are presented, and predictions of yield ratios such as and at large in heavy-ion collisions at the RHIC and the LHC are provided.
... Among many properties of the dense matter created in the heavy ion collisions at BNL Relativistic Heavy-Ion Collider (RHIC) and CERN Large Hadron Collider (LHC), the particle production is evolving into a mature field and always the subject of particular interest. The final particle production has been studied at RHIC and LHC for different systems, such as Au+Au, Cu+Cu, Pb+Pb and Xe+Xe, at different colliding energies from √ s N N = 7.7 GeV to 5.44 TeV [1][2][3][4][5][6]. In the past decades, the theoretical investigation of particle production in relativistic heavy ion collisions have been performed extensively with hydrodynamic model [7][8][9], statistical model [10], transport model [11,12] and coalescence model [13][14][15]. ...
In this paper, we study and predict the charged-particle pseudorapidity multiplicity density (), transverse momentum spectra of identified particles and their ratios in relativistic heavy ion collisions at the Large Hadron Collider (LHC), using the string-melting version of a multi-phase transport (AMPT) model with improved quark coalescence method. Results of the charged-particle pseudorapidity multiplicity density from AMPT model calculations for Pb+Pb collisions at TeV are compared with the experimental data. Good agreements are generally found between theoretical calculations and experimental data. We predict for Xe+Xe collisions at TeV at different centralities, and spectra of charged pions, kaons and protons, and their ratios and in Pb+Pb collisions at TeV and Xe+Xe collisions at TeV that are being studied at LHC. The spectra of identified particles in Pb+Pb collisions from the improved AMPT model are compared and found to be consistent with results from the iEBE-VISHNU hybrid model with TRENTo initial condition.
... nuclear shadowing effect in gluon parton distributions, may also play an important role. In 0−10% collisions, the suppression level is around 0.5 for p T > 3 GeV/c, which is comparable to both the measurements of electrons from heavy flavor hadron decays [8,9] and the light hadrons [10]. ...
In this erratum we report changes on the spectra and nuclear modification factor () in Au+Au collisions at = 200 GeV by fixing the errors in the efficiency and selection criteria that affected the Au+Au results. The p+p reference spectrum has changed as well and is updated with new fragmentation parameters.
