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Register a new userAn alternative way of plotting the data and results of models of J/psi suppression
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We propose an alternative way of looking at data on anomalous J/psi suppression. The proposed method is in principle equivalent to the one used by the NA50 Collaboration, but it permits to visualize separate contributions of individual processes responsible for the disintegration of J/psis produced by a hard process in nuclear collisions. The method can be used provided that the time sequence of contributing mechanisms is known or assumed. It offers an alternative graphical presentation of the onset of anomalous J/psi suppression in Pb-Pb interactions observed by the NA50 Collaboration at the CERN SPS and might contribute to explain why different mechanisms, such as J/psi suppression by the Quark-Gluon Plasma and by co-movers in the Dual Parton Model or in Monte Carlo microscopic approaches, all lead to an approximate description of anomalous J/psi suppression.
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The enhanced suppression of $J/psi$ production at large $x_F$ in $pA$ collisions is studied in the framework of gluon depletion at large $x_1$. The nonperturbative process that modifies the gluon distribution as the gluons propagate in nuclear matter is described by an evolution equation with a kernal to be determined by phenomenology. With nuclear shadowing and anti-shadowing taken into account, the effect on the gluon distribution is shown to be a depletion in excess of 40% at $x_1 approx 0.8$ for $A > 100$. There is a small amount of enhancement of the gluon distribution at small $x_1$, but it does not lead to any contradiction with the existing data on $J/psi$ suppression in the central region. Extentions to $psi^{prime}$ suppression and $AB$ collisions are also investigated in the framework of gluon redistribution.
We point out that data on the onset of anomalous J/psi suppression as a function of nucleon numbers A and B could provide information on the dynamics of nuclear interactions. In particular the models of anomalous J/psi suppression by Blaizot and Ollitrault (BO) and by Kharzeev, Lourenco, Nardi and Satz (KLNS) are based on different assumptions on the dynamics of nuclear collisions and lead to different predictions of the dependence of the onset of anomalous J/psi suppression on nucleon numbers of colliding nuclei. The data on this onset as function of A and B could become a tool for the study of the dynamics of nuclear collisions and bring further evidence on J/psi suppression by new form of hadronic matter, possibly Quark-Gluon Plasma. In particular we propose to study J/psi suppression in A+Pb interaction with nucleon number of A between 58 and 73 or a bit higher.
We propose a simple Glauber-type mechanism for suppression of jet production up to transverse momenta of about 10 GeV/c at RHIC. For processes in this kinematic region, the formation time is smaller than the interval between two successive hard partonic collisions and the subsequent collision influences the jet production. Number of jets then roughly scales with the number of participants. Proportionality to the number of binary collisions is recovered for very high transverse momenta. The model predicts suppression of jet production in d+Au collisions at RHIC.
Measurements of the suppression of the yield per nucleon of J/Psi and Psi production for 800 GeV/c protons incident on heavy relative to light nuclear targets have been made with very broad coverage in xF and pT. The observed suppression is smallest at xF values of 0.25 and below and increases at larger values of xF. It is also strongest at small pT. Substantial differences between the Psi and J/Psi are observed for the first time in p-A collisions. The suppression for the Psi is stronger than that for the J/Psi for xF near zero, but becomes comparable to that for the J/Psi for xF > 0.6.
We calculate the mass shift and thermal decay width of the $J/psi$ near the QCD transition temperature $T_c$ by imposing two independent constraints on these variables that can be obtained first by solving the Schrodinger equation and second from the QCD sum rule approach. While the real part of the potential is determined by comparing the QCD sum rule result for charmonium and the D meson to that from the potential model result, the imaginary potential is taken to be proportional to the perturbative form multiplied by a constant factor, which in turn can be determined by applying the two independent constraints. The result shows that the binding energy and the thermal width becomes similar in magnitude at around $T=1.09T_c$, above which the sum rule analysis also becomes unstable, strongly suggesting that the $J/psi$ will melt slightly above $T_c$.
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