Prompt neutrinos due to the decay of charmed mesons produced in the atmosphere from cosmic-ray and atmospheric nuclei interactions may be a significant source of background to ultra-high energy neutrino searches above 10 TeV. We re-evaluate this flux using updated charm production cross-sections based on QCD parameters, the charm quark mass, and the range for the factorization and renormalization scales that provide the best description of this data at fixed target experiments, at RHIC, and at LHC. We find that the prompt neutrino flux is reduced from previous results in the literature by a factor between two and eight, depending on the energy. We discuss the implications of our results for current IceCube data.
The production of charmonia in relativistic heavy-ion collisions is formulated within the framework of a quantum kinetic theory simultaneously accounting for breakup and recombination processes. The survival probability of J/Psi mesons is evaluated for a Mott-Hagedorn resonance gas, whereby the pattern of anomalous J/Psi suppression at CERN-SPS can be explained by a strong coupling to open-charm states and their in-medium modification. Recent data for charmonium suppression from Au-Au collisions at RHIC are discussed.
We discuss charmonium production in proton-nucleus collisions at RHIC energies under the assumption of xF and x2 scaling. We find that all the ambiguities due to energy loss are gone at this energy and therefore data will reveal the scaling law, if any. These p-A data will also be crucial to interpret nucleus-nucleus data with respect to a possible formation of a quark gluon plasma because the extrapolations for charmonium production from the present p-A data to RHIC energies, based on the two scaling laws, differ by a factor of four.
To extract information about polarized gluon distribution in the proton, charmed hadron, actually Λ_c^+, productions at RHIC experiment are studied. We found that the spin correlation asymmetry between the initial proton and the produced Λ_c^+ is enable us to distinguish parameterization models of polarized gluons.
We discuss aspects of open and hidden charm production in deuterium-nucleus collisions at RHIC and LHC energies. We describe calculations of the total $c \bar c$ cross section and the charm quark transverse momentum distributions. We next explain how shadowing and moderate nuclear absorption can explain the PHENIX $J/ψ$ dAu/$pp$ ratios and predict the combined effect of shadowing and absorption in 6.2 TeV d+Pb collisions.
We present results on rapidity and transverse momentum distributions of inclusive charm quark production in hadronic and heavy-ion collisions at RHIC and LHC energies, including the next-to-leading order, $O(α_s^3)$, radiative corrections and the nuclear shadowing effect. We determine the hadronic and the {\it effective} (in-medium) K-factor for the differential and total inclusive charm cross sections. We show that these K-factors have strong $p_T$ dependence. We discuss how measurements of charm production at RHIC and LHC can provide valuable information about the gluon density in a nucleus.
We present up-to-date QCD predictions for open charm and bottom production at RHIC in nucleon-nucleon collisions at \sqrt{S} = 200 GeV. The electron spectrum resulting from heavy flavor decays is also evaluated for direct comparison to the PHENIX and STAR data. These predictions seek to establish a rigorous benchmark, including the theoretical uncertainties, against which nuclear collision data can be compared to obtain evidence for nuclear effects.
We discuss aspects of open and hidden charm production in hadron-nucleus collisions at RHIC and LHC energies. We first discuss the extraction of the total charm cross section in lower energy collisions and how it compares to next-to-leading order quantum chromodynamics calculations. We then describe calculations of the transverse momentum distributions and their agreement with the shape of the measured STAR transverse momentum distributions. We next explain how shadowing and moderate nuclear absorption can explain the PHENIX $J/ψ$ dAu/$pp$ ratios.
We present results on rapidity and transverse momentum distributions of inclusive charm quark production in hadronic and heavy-ion collisions at RHIC and LHC energies, including the next-to-leading order, $O(α_s^3)$, radiative corrections and the nuclear shadowing effect. We determine hadronic and nuclear K-factor for the differential and total inclusive cross sections for the charm production. We discuss theoretical uncertainties inherent in our calculation. In particular, we find that different extrapolations of gluon density to low-$x$ region introduce large theoretical uncertainty in the c…
Electrons from semileptonic decays of heavy-flavor mesons (D and B) allow to study the energy loss of heavy-quarks in nuclear collisions at sqrt(s) = 200 GeV at RHIC. Since pQCD calculations have shown that the crossing point where bottom decay electrons start to dominate over charm decay electrons is largely unknown, an urgent need arises to access the relative contributions independently. A correlation method is proposed to identify and separate charm and bottom production processes on a statistical basis through tagging of their decay electrons and open charmed mesons. The feasibility for t…
We discuss features of charmonium suppression at $\sqtr{s} = 200$ GeV within the framework of the Glauber-Gribov theory and the comovers interaction model. The latter approach has been extended by allowing for secondary charmonium production due to recombination of $c\bar{c}$ pairs in the medium, estimated from pp data at the same bombarding energy. Centrality and rapidity dependence of the nuclear modification factor for J/psi in d+Au, Cu+Cu and Au+Au collisions at RHIC are reproduced without fitting a single model parameter. A strong suppression of J/psi is predicted for LHC energies.
Recent experimental and theoretical studies suggest that the quarkonia suppression in a thermal QCD medium created at heavy ion collisions is a complex interplay of various physical processes. In this article we put together most of these processes in a unified way to calculate the charmonium survival probability (nuclear modification factor) at energies available at relativistic heavy ion collider (RHIC) and large hadron collider (LHC) experiments. We have included shadowing as the dominant cold nuclear matter (CNM) effect. Further, gluo-dissociation and collision damping has been included wh…
Production of open and hidden charm hadrons in heavy ion collisions is considered within the statistical coalescence model. The charmed quark-antiquark pairs are assumed to be created at the initial stage of the reaction in hard parton collisions. The number of these pairs is conserved during the evolution of the system. At the hadronization stage, the charmed (anti)quarks are distributed among open and hidden charm hadrons in accordance with the laws of statistical mechanics. The model is in agreement with the experimental data on J/psi to Drell-Yan ratio in Pb+Pb collisions at SPS. This agre…
In order to extract information about behavior of polarized gluons in the nucleon, charmed hadron productions, i.e. D* meson and Lambda_c baryon productions, are studied in polarized pp reactions at BNL-RHIC energy. For these processes, the spin correlation asymmetry D_{LL} between the target proton and the produced charmed hadron, and its statistical sensitivity delta D_{LL} are calculated. From analyses on these processes, we found that the pseudo-rapidity distribution of D_{LL} in the limited transverse momentum region is quite effective for distinguishing the model of polarized gluons as w…
We study the correlation between the trigger $π$ and the associated $J/ψ$ on near and away sides in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. In the region of trigger momentum $p_t>4$ GeV/$c$, the $π$ spectrum is composed of thermal-shower and shower-shower recombinations in the frame work of the recombination model. We consider the azimuthal anisotropy in the quenched hard parton distribution and then calculate the elliptic flow parameter $v_2$ of charmed mesons ($J/ψ$, $D^0$ and $D_s$) for different centralities.
Measurements of dilepton production from charm decay and Drell-Yan processes respectively probe the gluon and sea quark distributions in hadronic collisions. In nucleus-nucleus collisions, these hard scattering processes constitute a `background' to thermal contributions from the hot matter produced by the collision. To determine the magnitude and behavior of this background, we calculate the hard scattering contribution to dilepton production in nuclear collisions at RHIC and LHC at next to leading order in perturbative QCD. Invariant mass, rapidity and transverse momentum distributions are p…
We study the production of charmonia and charmed hadrons in nucleus-nucleus collisions at SPS, RHIC, and LHC energies within the framework of the statistical hadronization model. Results from this model are compared to the measured yields and centrality dependence of J/psi production at SPS and RHIC energies. We explore and contrast the centrality dependence of the production of mesons with open and hidden charm at SPS, RHIC, and LHC. The sensitivity of the results to various input parameters is analyzed in detail for RHIC energy.
Physics of charmonium suppression in nuclear collisions drastically changes between the energies of SPS and RHIC. Mechanisms suppressing charmonia at SPS are reviewed, neither of which is important at RHIC. On the other hand, coherence, or shadowing of c-quarks and gluons barely seen at SPS, become a dominant effect at RHIC providing a much stronger suppression. A onset of coherence at Fermilab energies explains the observed cross section ratio steeply falling at large Feynman x_F. In nuclear collisions variation of charmonium suppression with x_F suggests a sensitive probe for QGP.
We present a detailed discussion on the doubly charmed baryon $Ξ_{cc}$ production at the RHIC and LHC via the proton-nucleus ($p$-N) and nucleus-nucleus (N-N) collision modes. The extrinsic charm mechanism via the subprocesses $g+c\to (cc)[n]+\bar{c}$ and $c+c\to (cc)[n]+g$ together with the gluon-gluon fusion mechanism via the subprocess $g+g\to(cc)[n]+\bar{c}+\bar{c}$ have been taken into consideration, where the intermediate diquark is in $[n]=[^1S_0]_{\bf 6}$-state or $[^3S_1]_{\bar{\bf 3}}$-state, respectively. Total and differential cross sections have been discussed under various collis…
We study $b\bar{b}$ and $c\bar{c}$ production and the influence of nuclear shadowing at LHC and RHIC energies. We find a significant reduction in the production cross section of both charm and bottom at RHIC and LHC. Bound states such as $Υ$ and $J/Ψ$ are suppressed by this reduction in the charm production cross sections. Therefore, $J/Ψ$ suppression may not be useful as a signature for the quark gluon plasma.
We consider the production of the open charm and J/psi mesons in heavy ion collisions at BNL RHIC. We discuss several recently developed pictures for J/psi production and argue that a measurement at RHIC energies is crucial for disentangling these different descriptions.
I review the color dipole formulation of heavy quark production in the light of recent RHIC data. Since charm and bottom production directly probe the gluon density, these processes allow one to study shadowing and parton saturation at RHIC and LHC. The dipole approach provides a convenient framework to calculate these nuclear effects. I present numerical results for open charm and bottom production in proton-proton and proton-nucleus collisions and discuss transverse momentum broadening of heavy quarkonia.
Integrated and differential $J/ψ R_{AA}$ are systematically studied in Au-Au collisions at RHIC-BES energies in a transport approach, including cold and hot nuclear effects respectively in the initial condition and the collision terms. With decreasing energy, while the temperature, life time and size of the QGP fireball decrease, the nuclear absorption of the initially produced charmonia is more and more strong, and the nuclear shadowing effect on charmonium regeneration goes to anti-shadowing first and then to shadowing again. As a competition between the cold and hot nuclear effects, the QGP…
We reexamine the charm contribution to atmospheric lepton fluxes in the context of perturbative QCD. We include next-to-leading order corrections and discuss theoretical uncertainties due to the extrapolations of the gluon distributions at small-x. We show that the charm contribution to the atmospheric muon flux becomes dominant over the conventional contribution from pion and kaon decays at energies of about 10^5 GeV. We compare our fluxes with previous calculations.
A kinetic equation approach is applied to model anomalous J/psi suppression at RHIC and SPS by absorption in a hadron resonance gas which successfully describes statistical hadron production in both experiments. The puzzling rapidity dependence of the PHENIX data is reproduced as a geometric effect due to a longer absorption path for J/psi production at forward rapidity.
We present results on rapidity and transverse momentum distributions of inclusive charm quark production in hadronic and heavy-ion collisions at RHIC and LHC energies, including the next-to-leading order, $O(α_s^3)$, radiative corrections and the nuclear shadowing effect. We determine the hadronic and the {\it effective} (in-medium) K-factor for the differential and total inclusive charm cross sections. We find the fraction of central and inelastic events that contain at least one charm quark pair at LHC energies and obtain the effective $A$-dependence of the inclusive charm production in prot…
In this paper we propose the study of the photoproduction of charmoniumlike states in $pp$ collisions at RHIC and LHC energies and estimate the rapidity distribution and total cross sections for the production of the exotic hadrons $Y(3940)$, $X(3915)$, $Z(4430)$ and $Z_c(3900)$. We demonstrate that the experimental analysis of this process can provide complementary and independent checks on these states, and help to understand their underlying nature.
We present results on rapidity and transverse momentum distributions of inclusive charm quark production in heavy-ion collisions at RHIC, including the next-to-leading order, $O(α_s^3)$, radiative corrections and the nuclear shadowing effect. We find the effective, nuclear K-factor to be $K(y)\approx 1.4$ for $\mid y\mid \leq 3$ in the rapidity distribution, while $1\leq K(p_{T}) \leq 3$ for $1GeV\leq p_T \leq 6GeV$ in the $p_T$ distribution. We incorporate multiple parton scatterings in our calculation of the fraction of all central events that contain at least one charm quark pair. We obtain…
We present a study on the spectra for heavy flavor (charm and bottom) decayed electrons in 200 GeV $p+p$ collisions and provide the relative contributions of charm and bottom hadrons from the PYTHIA calculations. The results suggest that the crossing point of the electron spectra from charm and bottom decays is above 7 GeV/$c$ and bottom contribution is not dominant for electron $p_{T}<3$ GeV/$c$. The upper limit of the relative cross section ratio is reported as $σ_{b\bar{b}}/σ_{c\bar{c}}\leq(0.49\pm0.09\pm0.09)%$. We also compare the $v_2$ distribution from simulation to the experimental dat…
In a coalescence plus fragmentation approach we calculate the heavy baryon/meson ratio and the $p_T$ spectra of charmed hadrons $D^{0}$, $D_{s}$ and $Λ_{c}^{+}$ in a wide range of transverse momentum from low $p_T$ up to about 10 GeV and discuss their ratios from RHIC to LHC energies without any change of the coalescence parameters. We have included the contribution from decays of heavy hadron resonances and also the one due to fragmentation of heavy quarks which do not undergo the coalescence process. The coalescence process is tuned to have all charm quarks hadronizing in the $p_T\rightarrow…
We make up-to-date QCD predictions for open charm and bottom production at RHIC in nucleon-nucleon collisions at \sqrt{S} = 200 GeV. We also calculate the electron spectrum resulting from heavy flavor decays to allow direct comparison to the data. A rigorous benchmark, including the theoretical uncertainties, is established against which nuclear collision data can be compared to obtain evidence for nuclear effects.
We estimate the energy of the lowest Charmonium and Upsilon states with hybrid admixtures using the method of QCD Sum Rules. Our results show that the $Ψ'(2S)$ and $Υ(3S)$ states both have about a 50% admixture of hybrid and meson components. From this we find explanations of both the famous $ρ-π$ puzzle for Charmonium, and the unusual pattern of $σ$ decays that have been found in $Υ$ decays. Moreover, this picture can be used for predictions of heavy quark production with the octet model for RHIC.
We present an evaluation of the atmospheric tau neutrino flux in the energy range between $10^2$ and $10^6$ GeV. The main source of tau neutrinos is from charmed particle production and decay. The $ν_τN\to τX$ event rate for a detector with a water equivalent volume of 1 km$^3$ is on the order of 60-100 events per year for $E_τ>100$ GeV, reducing to 18 events above 1 TeV. Event rates for atmospheric muon neutrino oscillations to tau neutrinos are also evaluated.
We evaluate the fluxes of neutrinos and muons from charmed particles produced by cosmic ray interactions with air nuclei. Using next-to-leading order perturbative QCD, we compare our results with calculations based on a PYTHIA Monte Carlo evaluation of charm production. We investigate the sensitivity of our results to the choice of parton distribution functions and the cosmic ray spectrum. Perturbative QCD yields larger lepton fluxes than the PYTHIA evaluation. The flux of muons from charm dominates the muon flux from pion and kaon decays for energies above $\sim 10^5$ GeV.
Charmonium production at heavy-ion colliders is considered within the comovers interaction model. The formalism is extended by including possible secondary J/psi production through recombination and an estimate of recombination effects is made with no free parameters involved. The comovers interaction model also includes a comprehensive treatment of initial-state nuclear effects, which are discussed in the context of such high energies. With these tools, the model properly describes the centrality and the rapidity dependence of experimental data at RHIC energy, $\sqrt{s}$ = 200 GeV, for both A…
We consider the production of the J/psi mesons in heavy ion collisions at RHIC energies in the statistical coalescence model with an exact (canonical ensemble) charm conservation. The c\bar{c} quark pairs are assumed to be created in the primary hard parton collisions, but the formation of the open and hidden charm particles takes place at the hadronization stage and follows the prescription of statistical mechanics. The dependence of the J/psi production on both the number of nucleon participants and the collision energy is studied. The model predicts the J/psi suppression for low energies, w…
We re-evaluate the prompt atmospheric neutrino flux, using the measured charm cross sections at RHIC and the Large Hadron Collider to constrain perturbative QCD parameters such as the factorization and renormalization scales, as well as modern parton distribution functions and recent estimates of the cosmic-ray spectra. We find that our result for the prompt neutrino flux is lower than previous perturbative QCD estimates and, consequently, alters the signal-to-background statistics of the recent IceCube measurements at high energies.
Production of muons and neutrinos in cosmic ray interactions with the atmosphere has been investigated with Monte Carlo models for hadronic interactions. The resulting conventional muon and neutrino fluxes (from $π$ and $K$ decays) agree well with earlier calculations, whereas our prompt fluxes from charm decays are significantly lower than earlier estimates. Charm production is mainly considered as a well defined perturbative QCD process, but we also investigate a hypothetical non-perturbative intrinsic charm component in the proton. The lower charm rate implies better prospects for detecting…
Production and elliptic flow of heavy quarks are investigated in nucleus-nucleus collisions at RHIC and LHC within the Boltzmann Approach of MultiParton Scatterings (BAMPS). The initial heavy quark yield is estimated with the leading order mini-jet model and compared to PYTHIA for several parton distribution functions. Secondary production of heavy quarks in the quark-gluon plasma is examined within the full 3+1 dimensional BAMPS simulation of heavy ion collisions. At RHIC this yield is negligible, but for LHC charm production in the QGP plays a significant role. In addition, we study the elli…
We present a study on the spectra and elliptic flow v2 for heavy flavor (charm and bottom) decayed electrons provided the relative contributions of charm and bottom hadrons from the PYTHIA calculations. We made a simultaneous fit to both measured non-photonic electron spectra and v2 distributions. The results suggest that the bottom contribution is not dominant for electron pt<5 GeV/c in the 200 GeV Au+Au collisions.
We update predictions for lepton fluxes from the hadroproduction of charm quarks in the scattering of primary cosmic rays with the Earth's atmosphere. The calculation of charm-pair hadroproduction applies the latest results from perturbative QCD through next-to-next-to-leading order and modern parton distributions, together with estimates on various sources of uncertainties. Our predictions for the lepton fluxes turn out to be compatible, within the uncertainty band, with recent results in the literature. However, by taking into account contributions neglected in previous works, our total unce…
Quantum Chromodynamics (QCD) is a basic gauge field theory to describe strong interactions. Lattice QCD calculations predict a phase transition from hadronic matter to a deconfined, locally thermalized Quark-Gluon Plasma (QGP) state at high temperature and small baryon density. Plenty of exciting results from RHIC experiments in the first three years have demonstrated that a hot dense matter with strong collective motion which cannot be described with hadronic degrees of freedom was created at RHIC. Charm quarks are believed to be mostly created from initial gluon fusion in heavy ion collision…
We consider the production of open charm in heavy ion collisions in the framework of the Color Glass Condensate. In the central rapidity region at RHIC, for the charm quark yield we expect N(coll) (number of collisions) scaling in the absence of final-state effects. At higher energies, or forward rapidities at RHIC, the saturation scale exceeds the charm quark mass; we find that this results in the approximate N(part) (number of participants) scaling of charm production in AA collisions and N(part)^A scaling in p(d)A collisions, similarly to the production of high pT gluons discussed earlier. …
In the energy range of RHIC and LHC the mechanisms of nuclear suppression of charmonia are expected to be strikingly different from what is known for the energy of the SPS. One cannot think any more of charmonium produced on a bound nucleon which then attenuates as it passes through the rest of the nucleus. The coherence length of charmonium production substantially exceeds the nuclear radius in the new energy range. Therefore the production amplitudes on different nucleons, rather than the cross sections, add up and interfere, i.e. shadowing is at work. So far no theoretical tool has been ava…
The production of charmonia is investigated for heavy-ion collisions from SPS to RHIC energies. Our approach incorporates two sources of $J/Ψ$ yield: (i) a direct contribution arising from early (hard) parton-parton collisions, subject to subsequent nuclear absorption, quark-gluon plasma and hadronic dissociation, and (ii) statistical production at the hadronization transition by coalescence of $c$ and $\bar{c}$ quarks. Within an expanding thermal fireball framework, the model reproduces $J/Ψ$ centrality dependencies observed at the SPS in Pb-Pb and S-U collisions reasonably well. The study of…
We investigate charm production in an equilibrated quark-gluon plasma produced in heavy-ion collisions at RHIC and LHC. Effective quark and gluon masses are introduced from thermal QCD calculations. Assuming a Bjorken-type longitudinal expansion and including the influence of temperature dependent masses on the expansion, we determine the total number of c\bar{c} pairs produced in the quark-gluon plasma phase. We calculate the charm production rate at leading order with massive gluons and quarks and compare our result to charm production by massless partons. We consider two different scenarios…
The RHIC experiments have measured the nuclear modification factor R_AA of non-photonic electrons in Au+Au collisions at sqrt(s) = 200 GeV. This R_AA exhibits a large suppression for pt > 2 GeV/c which is commonly attributed to heavy-quark energy loss. It is expected that the heavy-quark radiative energy loss is smaller than the light quark one because of the so-called dead-cone effect. An enhancement of the charm baryon yield with respect to the charm meson yield, as it is observed for light and strange hadrons, can explain part of the suppression. This phenomenon has been put forward in a pr…
We calculate the single transverse-spin asymmetry for open charm production in $pp$ collisions within the QCD collinear factorization approach. We include contributions from both twist-three quark-gluon and tri-gluon correlation functions. We find that the quark-gluon correlation functions alone generate only a very small asymmetry for open charm production in the kinematic region of current interest at RHIC, so that the observation of any significant single-spin asymmetry would be a clear indication of the presence of tri-gluon correlations inside a polarized proton. We furthermore demonstrat…
Heavy quark and charmonium production as well as their space-time evolution are studied in transport simulations of heavy-ion collisions at RHIC and LHC. In the partonic transport model Boltzmann Approach of MultiParton Scatterings (BAMPS) heavy quarks can be produced in initial hard parton scatterings or during the evolution of the quark-gluon plasma. Subsequently, they interact with the medium via binary scatterings with a running coupling and a more precise Debye screening which is derived from hard thermal loop calculations, participate in the flow and lose energy. We present results of th…
The production and space-time evolution of charm and bottom quarks in nucleus-nucleus collisions at RHIC and LHC are investigated with the partonic transport model BAMPS (Boltzmann Approach of MultiParton Scatterings). Heavy quarks, produced in primary hard parton scatterings during nucleon-nucleon collisions, are sampled using the Monte Carlo event generator PYTHIA or the leading order mini-jet model in conjunction with the Glauber model, revealing a strong sensitivity on the parton distribution functions, scales, and heavy quark mass. In a comprehensive study exploring different charm masses…
We have updated our previous investigation of the production of muons and neutrinos in cosmic ray interactions with the atmosphere, taking account of recent results from the $ep$ collider HERA in our QCD-based model for hadronic interactions. Qualitatively, our previous results remain unmodified: our predictions for the conventional muon and neutrino fluxes agree with earlier calculations, whereas the charm particle treatment we use gives significantly lower prompt fluxes compared to earlier estimates. This implies better prospects for detecting very high energy neutrinos from cosmic sources.
A study of elliptic flow of open charm mesons, $D^0$ and $D_S ^\pm$ using quark coalescence as a mechanism of hadronization of heavy quarks implemented in conjunction with A Multi Phase Transport (AMPT) model has been presented. We have studied the transverse momentum dependence of the elliptic flow parameter at mid-rapidity ($|y|$ $<$ 1.0) for Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV (RHIC) and Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV (LHC) for different values of partonic interaction cross-section and QCD coupling constant. We have compared our calculations with the experimentally…
The prompt contribution to the atmospheric neutrino flux is analyzed. It is demonstrated that the corresponding theoretical uncertainties related to perturbative treatment of charm production, notably, the ones stemming from the low and high $x$ behavior of parton distribution functions, can be conveniently studied at the level of charm quark production. Additionally, we discuss the non-perturbative contribution to the prompt neutrino flux, related to the intrinsic charm content of the proton, and analyze its main features.
We present a study of charmed hadron transverse momentum distribution from p+p collisions at $\sqrt{s_{NN}}=200$ GeV using the PYTHIA Monte Carlo event generator. The PHENIX tuned PYTHIA parameter set based on electron measurements alone yields a $D$ meson $p_{T}$ distribution softer than the preliminary STAR experimental data from d+Au collisions scaled by the number of binary collisions. In order to match the STAR $p_{T}$ spectrum, the higher order QCD effects in PYTHIA have to be taken into account, and a fragmentation function of charm quarks much harder than the default Peterson function …
Hadroproductions of charmonium and bottomonium $χ_J$ in polarized $pp$ collisions at RHIC energies are studied. Two--spin asymmetries $A_{LL}^{χ_J}(pp)$ for these reactions are very good parameters for examining the polarized gluon distributions in a proton.
We consider exclusive double diffractive production of scalar χ_c(0^+), axial-vector χ_c(1^+) and tensor χ_c(2^+) charmonia in proton-(anti)proton collisions at different energies. The corresponding amplitudes for these processes are derived within the k_t-factorisation approach and the corresponding cross section is calculated with different unintegrated gluon distribution functions (UGDFs) known from the literature. We compare exclusive production of all charmonium states χ_c(0^+), χ_c(1^+) and χ_c(2^+) including branching fraction for radiative J/Ψ+ γdecay channel. Corresponding experimenta…
The complete understanding of the basic constituents of hadrons and the hadronic dynamics at high energies are two of the main challenges for the theory of strong interactions. In particular, the existence of intrinsic heavy quark components in the hadron wave function must be confirmed (or disproved). In this paper we propose a new mechanism for the production of $D$-mesons at forward rapidities based on the Color Glass Condensate (CGC) formalism and demonstrate that the resulting transverse momentum spectra are strongly dependent on the behavior of the charm distribution at large Bjorken $x$…
Important goals of RHIC and LHC experiments with ion beams include the creation and study of new forms of matter, such as the Quark Gluon Plasma. Heavy quark production and attenuation will provide unique tomographic probes of that matter. We predict the suppression pattern of open charm and beauty in $Au+Au$ collisions at RHIC and LHC energies based on the DGLV formalism of radiative energy loss. A cancelation between effects due to the $\sqrt{s}$ energy dependence of the high $p_T$ slope and heavy quark energy loss is predicted to lead to surprising similarity of heavy quark suppression at R…
The RHIC data on charm production are compared with the kT-factorization approach predictions, both standard NLO QCD and FONLL. The calculated results underestimate the STAR Collaboration data. The role of possible nuclear effects is discussed.
