198138925
Oscillations of moments in high-energy nucleus-nucleus collisions
The definitions of density function and moment of multiplicity distribution are introduced, and the method of moment analysis in e+e- and proton-proton (pp) interactions is extended into nucleus-nucleus (AA) interactions. We analyze the data for relativistic nucleus-nucleus collisions and calculate the values of Hq for charged particle multiplicity distributions, by which we study systematically the dependences of Hqon incident energy, mass of colliding system, pseudorapidity interval, centrality and truncation of multiplicity. We compare the oscillation structures induced by e+ e-, pp and AA interactions, and the comparison and analysis are carried out between experimental data and QCD prediction. The latest results are given in this paper.
122178976
Fluctuations of K/π Ratios in Pb-Pb Collisions at Super Proton Synchrotron Energies
The Monte Carlo generator (LUCIAE) is used to investigate the fluctuations of K/π ratios at super proton synchrotron energies. The distribution of K/π ratios seems to be Gaussian from the simulation and the distribution width, and the relative variances are larger than those from the Poissonian-type pure-statistical fluctuations. This discrepancy might be attributed to the dynamical fluctuations involved in the LUCIAE model.
119042314
CHARM PRODUCTION AT LARGE RAPIDITIES IN p+p AND d+Au COLLISIONS AT PHENIX AT RHIC
We study charm production through dimuon and single muon measurements at forward and backward rapidities in p+p and d+Au collisions with the PHENIX muon detectors. We also compare open charm to $J/\psi$ yields in the forward and backward rapidities in d+Au collisions and study the origin of the large forward and backward asymmetry in open charm production observed by the PHENIX experiment.
119949182
Systematic study for grey particles in relativistic nucleus + emulsion (Ag) interactions
The hadronic and string cascade model and the corresponding event generator LUCIAE are used to study systematically the production of the grey particles in (14.6, 60 and 200A GeV)0 + Em, (2004 GeV)Si + Em, (200A GeV)S + Em and (11.6A GeV)Au + Em reactions. The dependences of the mean multiplicity, the multiplicity distributions and the polar angular distributions of the grey particles on the incident energy, the projectile mass and the collision centrality observed in emulsion experiments, respectively, are all reproduced by LUCIAE calculations. In addition the effects of the rescattering on the grey particle production are also investigated.
120471376
QGP phase transition and multiplicity fluctuations
The scaled factorial moments in QGP phase transitions are studied analytically by the extended Ginzburg-Landau model. The dependence of lnFq on phase space interval is different for the first- and second-order QGP phase transitions. When lnFq, are fitted to polynomials ofX≡δ1/3, the relative sign between the fitted coefficients ofX andbq,1 calculated theoretically can be used to judge the order of phase transitions. Two sets of experimental data are reanalysed and the phase transitions are the first order for one set of data but the second order for another.
124686282
A Rigidity Measurement of Pseudo-Rapidity Spectrum of Produced Particles in High Energy Nucleus-Nucleus Collisions
A new concept, rigidity of pseudo-rapidity spectrum, is extended into the study of the multiplicity fluctuations in high energy nucleus-nucleus interactions. In using the novel method to analyze the data of 16O-Em at 14.6, 60, and 200 A GeV, and 32S-Em at 200 A GeV, it is found that the rigidity of pseudo-rapidity spectrum in the central domain of pseudo-rapidity might be a mixture of Poisson type and Wigner one.
119341455
Dihadron Tomography of High-Energy Nuclear Collisions in NLO pQCD
Back-to-back dihadron spectra in high-energy heavy-ion collisions are studied within the next-to-leading order (NLO) perturbative QCD parton model with jet quenching incorporated via modified jet fragmentation functions due to radiative parton energy loss in dense medium. The experimentally observed appearance of back-to-back dihadrons at high $p_T$ is found to originate mainly from jet pairs produced close and tangential to the surface of the dense matter. However, a substantial fraction of observed high $p_T$ dihadrons also comes from jets produced at the center of the medium after losing finite amount of energy. Consequently, the suppression factor of such high-$p_T$ hadron pairs is found to be more sensitive to the initial gluon density than the single hadron spectra that are dominated by surface emission. A simultaneous $\chi^2$-fit to both the single and dihadron spectra can be achieved within a narrow range of the energy loss parameters $\epsilon_0=1.6-2.1$ GeV/fm. Because of the flattening of the initial jet production spectra, high $p_T$ dihadrons at the LHC energy are found to be more robust as probes of the dense medium.
2598386
Particle Production in High-energy Heavy-ion Collisions
Particle production mechanisms in high-energy heavy-ion collisions are reviewed in connection with recent experimental data from RHIC. Implications on mini-jet production, parton saturation and jet quenching are discussed.
119230540
Quantitative extraction of the jet transport parameter from combined data at RHIC and LHC
Abstract Using theoretical tools developed by the JET Collaboration in which one employs ( 2 + 1 ) D or ( 3 + 1 ) D hydrodynamic models for the bulk medium evolution and jet quenching models, the combined data on suppression of single inclusive hadron spectra at both RHIC and LHC are systematically analyzed with five different approaches to the parton energy loss. The jet transport parameter is extracted from the best fits to the data with values of q ˆ ≈ 1.2 ± 0.3 and 1.9 ± 0.7 GeV 2 / fm in the center of the most central Au + Au collisions at s = 200 GeV and Pb + Pb collisions at s = 2.67 TeV , respectively, at an initial time τ 0 = 0.6 fm / c for a quark jet with an initial energy of 10 GeV/c.
8631710
Heavy quark production in pp collisions
A systematic study of the inclusive single heavy quark and heavy-quark pair production cross sections in pp collisions is presented for RHIC and LHC energies. We compare with existing data when possible. The dependence of the rates on the renormalization and factorization scales is discussed. Predictions of the cross sections are given for two different sets of parton distribution functions.
15239653
Probing the topcolor-assisted technicolor model via the single t-quark production at the CERN LHC
The single t-quark production in proton-proton collisions can proceed through three distinct processes: tq, tb, tW productions. With the running of the Large Hadron Collider (LHC) at CERN, it has good potential to measure each single t-quark production mode. The topcolor-assisted technicolor (TC2) model, one of the promising dynamical theories, predicts some new particles at the several hundred GeV scale: three top-pion bosons ({pi}{sub t}{sup {+-}}, {pi}{sub t}{sup 0}) and one top-Higgs boson (h{sub t}). These particles are regarded as the typical feature of the TC2 model and can contribute to some processes. In this paper, we systematically study the contribution of the TC2 model to the single t-quark production at the Hadron colliders, especially at the LHC. The TC2 model can contribute to the cross section of the single t-quark production in two different ways. First, the existence of the top pions and top Higgs can modify the Wtb coupling via their loop contributions, and such modification can cause the correction to the cross sections of all three production modes. Our study shows that this kind of correction is negative and very small in all cases. Thus it is difficult to observe such a correction even at the LHC.more » On the other hand, there exist the tree-level flavor-changing (FC) couplings in the TC2 model which can also contribute to the cross sections of the tq and tb production processes. The resonant effect can greatly enhance the cross sections of the tq and tb productions. The first evidence of the single t-quark production has been reported by the D0 collaboration and the measured cross section for the single t-quark production of {sigma}(pp{yields}tb+X,tqb+X) is compatible at the 10% level with the standard model prediction. Because the light top pion can make a great contribution to the tb production, the top-pion mass should be very large in order to make the predicted cross section in the TC2 model be consistent with the Tevatron experiments. More detailed information about the top-pion mass and the FC couplings in the TC2 model should be obtained with the running of the LHC.« less