Cold nuclear matter effects on J/ψ production in d-Au collisions

The medium modifications of J/ψ production in d-Au collisions at √SNN= 200 GeV are studied in the Glauber model. By means of the c.m. energy loss parameter per collision studied in Drell-Yan process,taking account of the inhomogeneous shadowing effect, we find that the initial-state energy loss effect can be ignored in d-Au collisions at mid-rapidity. Then, the final-state J/ψ absorption effect is also considered and the theoretical results are in good agreement with the recent experimental data given by PHENIX. Finally,the experimental results of J/ψ production in d-Pb collisions are also predicted at RHIC and LHC energies respectively.     

Cold nuclear matter effects on J/ψ production in d-Au collisions

The medium modifications of J/ψ production in d-Au collisions at √s_NN=200 GeV are studied in the Glauber model. By means of the c.m. energy loss parameter per collision studied in Drell-Yan process, taking account of the inhomogeneous shadowing effect, we find that the initial-state energy loss effect can be ignored in d-Au collisions at mid-rapidity. Then, the final-state J/ψ absorption effect is also considered and the theoretical results are in good agreement with the recent experimental data given by PHENIX. Finally, the experimental results of J/ψ production in d-Pb collisions are also predicted at RHIC and LHC energies respectively.     

Energy loss of charm quarks from J/ψ production in cold nuclear matter

J/ψ suppression in p-A collisions is studied by considering the nuclear effects on parton distribution,energy loss of beam proton and the finial state energy loss of color octet cc. The leading-order computations for J/ψproduction cross-section ratios RW/Be(x F) are presented and compared with the selected E866 experimental data with the cc remaining colored on its entire path in the medium. It is shown that the combination of the different nuclear effects accounts quite well for the observed J/ψ suppression in the experimental data. It is found that the J/ψ suppression on RW/Be(x F) from the initial state nuclear effects is more important than that induced by the energy loss of color octet cc in the large x F region. Whether the cc pair energy loss is linear or quadratic with the path length is not determined. The obtained cc pair energy loss per unit path length α = 2.78±0.81 Ge V/fm, which indicates that the heavy quark in cold nuclear matter can lose more energy compared to the outgoing light quark.     

The study of gluon energy loss in cold nuclear matter from J/ψ production

The energy loss effects of the incident quark, gluon, and the color octet ccˉ on J/ψ suppression in p-A collisions are studied by means of the experimental data at E866, RHIC, and LHC energy. We extracted the transport coefficient for gluon energy loss from the E866 experimental data in the middle x F region(0.20 x F 0.65) based on the Salgado-Wiedemann(SW) quenching weights and the recent EPPS16 nuclear parton distribution functions together with nCTEQ15. It was determined that the difference between the values of the transport coefficient for light quark, gluon, and heavy quark in cold nuclear matter is very small. The theoretical results modified by the parton energy loss effects are consistent with the experimental data for E866 and RHIC energy, and the gluon energy loss plays a remarkable role on J/ψ suppression in a broad variable range. Because the corrections of the nuclear parton distribution functions in the J/ψ channel are significant at LHC energy level, the nuclear modification due to the parton energy loss is minimal. It is worth noting that we use the color evaporation model(CEM) at leading order to compute the p-p baseline, and the conclusion in this paper is CEM model dependent.     

Nuclear effects on J/ψ production in proton–nucleus collisions

The study of nuclear effects for J/ψ production in proton–nucleus collisions is crucial for a correct interpretation of the J/ψ suppression patterns experimentally observed in heavy-ion collisions. By means of three representative sets of nuclear parton distribution, the energy loss effect in the initial state and the nuclear absorption effect in the final state are taken into account in the uniform framework of the Glauber model. A leading order phenomenological analysis is performed on J/ψ production cross-section ratios R _W/Be (x _F) for the E866 experimental data. The J/ψ suppression is investigated quantitatively due to the different nuclear effects. It is shown that the energy loss effect with resulting in the suppression on R _W/Be (x _F) is more important than the nuclear effects on parton distributions in high x _F region. The E866 data in the small x _F keep out the nuclear gluon distribution with a large anti-shadowing effect. However, the new HERA-B measurement is not in support of the anti-shadowing effect in the nuclear gluon distribution. It is found that the J/ψ–nucleon inelastic cross section $\sigma^{J/\psi}_{\mathrm{abs}}$ depends on the kinematical variable x _F, and increases as x _F in the region x _F>0.2.     

Photoproduction of J/ψ in non-single-diffractive p+p collisions

Significant enhancements of J/ψ production at very low transverse momenta were recently observed by the ALICE and STAR collaborations in peripheral hadronic A+A collisions. The anomalous excess points to coherent photon-nucleus interactions in violent hadronic heavy-ion collisions, which were conventionally studied only in ultra-peripheral collisions. Assuming that the coherent photoproduction is the underlying mechanism responsible for the excess observed in peripheral A+A collisions, its contribution in p+p collisions with nuclear overlap, i.e. nonsingle-diffractive collisions, is of particular interest. In this paper, we perform a calculation of exclusive J/ψ photoproduction in non-single-diffractive p+p collisions at the RHIC and LHC energies based on the pQCD motivated parametrization using the world-wide experimental data, which could be further employed to improve the precision of the phenomenological calculations for photoproduction in A+A collisions. The differential rapidity and transverse momentum distributions of J/ψ from photoproduction are presented. In comparison with the J/ψ production from hadronic interactions, we find that the contribution of photoproduction is negligible.     

Transverse-momentum dependence of J/Ψ production in nuclear collisions

The suppression of J/Ψ production at transverse moment p_⊥ < 2 GeV/c in central ¹⁶O+²³⁸U→Ψ+X at 200 A GeV has been interpreted as a possible signature of quark-gluon plasma formation. We show, however, that the observed p_⊥ dependence is consistent with extrapolations from p+A→Ψ+X data, and that quasielastic initial-state parton scattering together with final-state inelastic hadronic reactions may explain the preliminary data.     

Energy loss of charm quarks from J/ψ production incold nuclear matter

J/ψ suppression in p-A collisions is studied by considering the nuclear effects on parton distribution, energy loss of beam proton and the finial state energy loss of color octet cc. The leading-order computations for J/ψ production cross-section ratios R_W/Be(x_F) are presented and compared with the selected E866 experimental data with the cc remaining colored on its entire path in the medium. It is shown that the combination of the different nuclear effects accounts quite well for the observed J/ψ suppression in the experimental data. It is found that the J/ψ suppression on R_W/Be(x_F) from the initial state nuclear effects is more important than that induced by the energy loss of color octet cc in the large x_F region. Whether the cc pair energy loss is linear or quadratic with the path length is not determined. The obtained cc pair energy loss per unit path length α=2.78±0.81 GeV/fm, which indicates that the heavy quark in cold nuclear matter can lose more energy compared to the outgoing light quark.     

Cold nuclear matter effects on J/ψ yields as a function of rapidity and nuclear geometry in d+A collisions at sqrt[s(NN)]=200 GeV

We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200 GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2相似文献   

J/ψ and Drell-Yan pair production on nuclear targets

We estimate energy losses in the cases of J/ψ and l -pair production on nuclear targets in terms of the effective change of the initial beam energy. Our phenomenological results are in reasonable agreement with theoretical calculations. The text was submitted by the authors in English.     

A-dependence of φ-meson production in p + A collisions

A systematic analysis of the A-dependence of φ-meson production in proton-nucleus collisions is presented. We apply different formalisms for the evaluation of the φ-meson distortion in nuclei and discuss the theoretical uncertainties of the data analysis. The corresponding results are compared to theoretical predictions. We also discuss the interpretation of the extracted results with respect to different observables and provide relations between frequently used definitions. The perspectives of future experiments are evaluated and estimates based on our systematical study are given.     

J/ψ production and absorption in high energy proton-nucleus collisions

Measured J/ψ production cross sections for 200 and 450 GeV/c protons incident on a variety of nuclear targets are analyzed within a Glauber framework which takes into account energy loss of the beam proton, the time delay of particle production due to quantum coherence, and absorption of the J/ψ on nucleons. The best representation is obtained for a coherence time of 0.5 fm/c, previously determined by Drell–Yan production in proton-nucleus collisions, and an absorption cross section of 3.6 mb, which is consistent with the value deduced from photoproduction of the J/ψ on nuclear targets.     

Nuclear modification factor for J/ψ production in nucleus-nucleus collisions

The STAR Collaboration has offered an eminent nuclear modification factor of J/ψ at high p_T and midrapidity produced in Cu-Cu collisions at √s_NN=200 GeV. Recalling a prediction, we can understand that the feature of high-p_T nuclear modification factor is related to cc produced by 2 → 1 and 2 → 2 partonic processes in deconfined matter, particularly in the prethermal stage and to the recombination of c and c. The nuclear modification factor at high p_T is sensitive to the earliest form of deconfined matter that does not have a temperature.     

J/ψ and γ production in high energy electron-proton collisions

Differential cross sections for electroproduction of J/ψ and γ are predicted for HERA and LHC energies.     

J/ψ production in PHENIX

Heavy quarkonia production is expected to be sensitive to the formation of a quark gluon plasma (QGP). The PHENIX experiment has measured J/ψ production at  =200 GeV in Au+Au and Cu+Cu collisions, as well as in reference p+p and d+Au runs. J/ψ’s were measured both at mid (|y|<0.35) and forward (1.2<|y|<2.2) rapidity. In this letter, we present the A+A preliminary results and compare them to normal cold nuclear matter expectations derived from PHENIX d+Au and p+p measurements as well as to theoretical models including various effects (color screening, recombination, sequential melting...).     

Energy loss effect of incoming gluons from J/ψ production in p-A collisions

The energy loss effect of incoming gluons from J/ψ production in p-A(or d-A) collisions is investigated by means of the E866, RHIC and LHC experimental data. The gluon mean energy loss per unit path length d E/d L = 2.18 ± 0.14 Ge V/fm is extracted by fitting the E866 experimental data for J/ψ production cross section ratios R W(Fe)/Be(x F). The obtained result indicates that the incoming gluons lose more energy than the incident quarks. By comparing the theoretical results with E866, RHIC, and LHC experimental data, it is found that the nuclear suppression due to the incident gluon(quark) energy loss reduces(increases) with the increase of the kinematic variable x F(or y). The energy loss effect of incoming gluons plays an important role in the suppression of J/ψ production in a wide energy range from√s = 38.7 Ge V to√s = 5.0 Te V, and the influence of incident quark energy loss can be ignored for high energies(such as at RHIC and LHC energy).     

J/ψ-N center of mass energy dependence of nuclear absorption effect on J/ψ production

In this paper, the J/ψ nuclear absorption effect is studied at RHIC and LHC energies with the EKS98 shadowing parameterizations. By assuming that the J/ψ absorption cross section, σ abs , increases with the charmonium-nucleon （J/ψ-N） center of mass energy, s J/ψN , it is found that σ abs should depend on x F （or y） at a certain center of mass energy per nucleon pair,s , especially at LHC energies. The theoretical results with the x F （or y）-dependence of the absorption effect are in good agreement with the experiment data from PHENIX in d-Au collisions and the predicted results will be examined by the forthcoming experimental data from LHC in d-Pb collisions. Finally, we also present baseline calculations of cold nuclear matter effects on J/ψ production in nucleus-nucleus （A-A） collisions and find that the x F （or y）-dependence of absorption effect is very small at both RHIC and LHC energies in A-A collisions.     

J/ψ-N center of mass energy dependence of nuclear absorption effect on J/ψ production

In this paper, the J/ψ nuclear absorption effect is studied at RHIC and LHC energies with the EKS98 shadowing parameterizations. By assuming that the J/ψ absorption cross section, σ abs , increases with the charmonium-nucleon (J/ψ-N) center of mass energy, s J/ψN , it is found that σ abs should depend on x F (or y) at a certain center of mass energy per nucleon pair,s , especially at LHC energies. The theoretical results with the x F (or y)-dependence of the absorption effect are in good agreement with the experiment data from PHENIX in d-Au collisions and the predicted results will be examined by the forthcoming experimental data from LHC in d-Pb collisions. Finally, we also present baseline calculations of cold nuclear matter effects on J/ψ production in nucleus-nucleus (A-A) collisions and find that the x F (or y)-dependence of absorption effect is very small at both RHIC and LHC energies in A-A collisions.     

Excitation of color degrees of freedom of nuclear matter and J/ψ suppression

In high-energy nuclear collisions, the conventional Glauber model is commonly used to evaluate the contribution to J/ψ suppression originating from the inelastic interaction with colorless bound nucleons. This requires an effective value for the J/ψ-nucleon absorption cross-section which is larger than theoretically expected. On the other hand, multiple nucleon-nucleon collisions, mediated by color exchange interactions, excite their color degrees of freedom. We investigate the importance of this effect and find that these excited states provide a larger cross-section for J/ψ absorption. We conclude that the related corrections are important to explain the effective value extrapolated from experiment. Received: 6 November 2000 / Accepted: 5 June 2001