The drag and diffusion coefficients are studied within the framework of Fokker-Planck dynamics for the case of a charm quark propagating in an expanding quark-gluon plasma. The space-time evolution of the nuclear matter created in the relativistic heavy-ion collision is modelled using MUSIC, a 3+1 D relativistic viscous hydrodynamic approach. The effect of viscous corrections to the heavy quark transport coefficients is explored by considering scattering processes with thermal quarks and gluons in the medium. It is observed that the momentum diffusion of the heavy quarks is sensitive to the shear and bulk viscosity to entropy ratios. The collisional energy loss of the charm quark in the viscous quark-gluon plasma is analyzed.
In the first part of the talk, we briefly review the problem of parton-energy loss and thermalization at the Relativistic Heavy-Ion Collider and discuss how heavy quarks (charm and bottom) can help to resolve the existing experimental and theoretical puzzles. The second part of the talk is devoted to the properties of heavy quarkonia in the (strongly interacting) Quark-Gluon Plasma (sQGP) and their consequences for observables in heavy-ion collisions.
Using the color evaporation model, the cross section for charmonium production in p+p collision is calculated in quark-gluon plasma. The threshold energy for open charms is given by the free energy potential from lattice calculations, the initial charm quark pairs by the Pythia simulations, and their time evolution by solving the Langevin equation. It is found that the threshold energy which decreases with temperature reduces the cross section while the invariant mass of charm pair which decreases by collisions enhances it. As a result, charmonia production is suppressed by $30$\sim$50\%$ whil…
We study the effect of thermal charm production on charmonium regeneration in high energy nuclear collisions. By solving the kinetic equations for charm quark and charmonium distributions in Pb+Pb collisions, we calculate the global and differential nuclear modification factors $R_{AA}(N_{part})$ and $R{AA}(p_t)$ for $J/Ψ$s. Due to the thermal charm production in hot medium, the charmonium production source changes from the initially created charm quarks at SPS, RHIC and LHC to the thermally produced charm quarks at Future Circular Collider (FCC), and the $J/Ψ$ suppression ($R_{AA}<1$) observe…
A selfconsistent calculation of heavy-quark (HQ) and quarkonium properties in the Quark-Gluon Plasma (QGP) is conducted to quantify flavor transport and color screening in the medium. The main tool is a thermodynamic $T$-matrix approach to compute HQ and quarkonium spectral functions in both scattering and bound-state regimes. The $T$-matrix, in turn, is employed to calculate HQ selfenergies which are implemented into spectral functions beyond the quasiparticle approximation. Charmonium spectral functions are used to evaluate eulcidean-time correlation functions which are compared to results f…
Photons radiated in heavy-ion collisions are a penetrating probe, and as such can play an important role in the determination of the quark-gluon plasma (QGP) transport coefficients. In this work we calculate the bulk viscous correction to photon production in two-to-two scattering reactions. Phase-space integrals describing the bulk viscous correction are evaluated explicitly in order to avoid the forward scattering approximation which is shown to be poor for photons at lower energies. We furthermore present hydrodynamical simulations of AA collisions focusing on the effect of this calculation…
Under the framework of the viscous chromohydrodynamics, the gluon self-energy is derived for the quark-gluon plasma with shear viscosity. The viscous electric permittivity and magnetic permeability are evaluated from the gluon self-energy, through which the refraction index %in the %viscous quark-gluon plasma is investigated. The numerical analysis indicates that the refractive index becomes negative in some frequency range. The start point for that frequency range is around the electric permittivity pole, and the magnetic permeability pole determines the end point. As the increase of $η/s$, t…
A Lagrangian density for viscous quark-gluon plasma has been constructed within the fluid-like QCD framework. Gauge symmetry is preserved for all terms inside the Lagrangian, except for the viscous term. The transition mechanism from point particle field to fluid field, and vice versa, is discussed. The energy momentum tensor that is relevant for the gluonic plasma having the nature of fluid bulk of gluon sea is derived within the model. By imposing conservation law in the energy momentum tensor, shear viscosity appears as extractable from the equation.
Charm production from the quark-gluon plasma created in the midrapidity of central heavy ion collisions at the Large Hadron Collider (LHC) is studied in the next-to-leading order in QCD. Using a schematic longitudinally boost-invariant and transversally expanding fire-cylinder model, we find that charm production could be appreciably enhanced at LHC as a result of the high temperature that is expected to be reached in the produced quark-gluon plasma. Sensitivities of our results to the number of charm quark pairs produced from initial hard scattering, the initial thermalization time and temper…
We study electromagnetic field effect on charmonium gluon-dissociation in quark-gluon plasma. With the effective Hamiltonian derived from QCD multipole expansion under an external electromagnetic field, we first solve the two-body Schrödinger equation for a pair of charm quarks with mean field potentials for color and electromagnetic interactions and obtain the charmonium binding energies and wave functions, and then calculate the gluon-dissociation cross-section and decay width by taking the color electric and magnetic dipole interactions as perturbations above the mean field and employing Fe…
We study vacuum masses of charmonia and the charm-quark diffusion coefficient in the quark-gluon plasma based on the spectral representation for meson correlators. To calculate the correlators, we solve the quark gap equation and the inhomogeneous Bethe-Salpeter equation in the rainbow-ladder approximation. It is found that the ground-state masses of charmonia in the pseudoscalar, scalar, and vector channels can be well described. For $1.5\,T_c<T<3.0\,T_c$, the value of the diffusion coefficient $D$ is comparable with that obtained by lattice QCD and experiments: $3.4<2πTD<5.9$. Relating the d…
We solve the relativistic Riemann problem in viscous gluon matter employing a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio $η/s$ from zero to infinity. We show that an $η/s$ ratio larger than 0.2 prevents the development of well-defined shock waves on timescales typical for ultrarelativistic heavy-ion collisions. Comparisons with viscous hydrodynamic calculations confirm our findings.
In relativistic heavy ion collisions, also the bremsstrahlung of gluons in the fragmentation regions of the nuclei suppresses the produced charmonium states. In the energy range of the SPS, the radiation of semi-hard gluons occurs in the Bethe-Heitler regime and the density of gluons and therefore the suppression goes like $(AB)^{1\over3}$, where $A$ and $B$ are the nucleon numbers of the projectile and target nuclei. In contrast, the suppression via collisions with nucleons is proportional to $(A^{1\over3} + B^{1\over3})$. Parameter free perturbative QCD calculations are in a good agreement w…
We evaluate the frame-independent gluon and charm parton-distribution functions (PDFs) of the deuteron utilizing light-front quantization and the impulse approximation. We use a nuclear wave function obtained from solving the nonrelativistic Schroedinger equation with the realistic Argonne v18 nuclear force, which we fold with the proton PDF. The predicted gluon distribution in the deuteron (per nucleon) is a few percent smaller than that of the proton in the domain x_{bj} = Q^2 / (2 p_N \cdot q) \sim 0.4, whereas it is strongly enhanced for x_{bj} larger than 0.6. We discuss the applicability…
We calculate rapidity and transverse momentum distributions of charmonium formed in high energy heavy ion collsions from incoherent recombination of charm quarks. The results are very sensitive to the corresponding distributions of the charm quarks, and thus can serve as a probe of the state of matter produced in the heavy ion collision. At one extreme we generate a set of charm pair momenta directly from pQCD amplitudes, which are appropriate if one can neglect interaction of the quarks with the medium. At the other extreme we generate momenta of charm quarks in thermal equilibrium with the e…
We demonstrate that a Quark-Gluon Plasma (QGP) with a dilute admixture of heavy quarks has, in general, a lower speed of sound than a "pure" QGP without effects from heavy flavors. The change in the speed of sound is sensitive to the details of the theory, making the hydrodynamic response to "flavoring" a sensitive probe of the underlying microscopic dynamics. We suggest that this effect may be measured in ultrarelativistic heavy ion collisions by relating the event-by-event number of charm quarks to flow observables such as the average transverse momentum.
Strangeness, charmonium and open charm yields in relativistic nucleus-nucleus collisions are considered within statistical model approach as potential signals of the quark-gluon plasma.
We have investigated the charmonium survival probability, in a high baryon density parton plasma, expected to be produced in nuclear collisions at FAIR. Charmonia are assumed to undergo complete dissociation by color screening, if the in-medium Debye radius becomes comparable to the spatial size of the corresponding bound state. Results indicate a non-trivial dependence of the suppression pattern on the plasma evolution dynamics. A much larger magnitude of suppression is foreseen induced by cold nuclear matter compared to that due to plasma screening.
We calculate at the leading order in $α_s$ the QCD amplitude for exclusive neutrino production of a $D^*$ or $D_s^*$ charmed vector meson on a nucleon. We work in the framework of the collinear QCD approach where generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions. We include $O(m_c)$ terms in the coefficient functions and $O(m_D)$ term in the definition of heavy meson distribution amplitudes. The show that the analysis of the angular distribution of the decay $D_{(s)}^*\to D_{(s)} π$ allows to access the transversity gluon GPDs.
The gluon polarization tensor for the quark-gluon plasma with shear viscosity is derived with the viscous chromohydrodynamics. The longitudinal and transverse dielectric functions are evaluated from the gluon polarization tensor, through which the polarization energy loss suffered by a fast quark traveling through the viscous quark-gluon plasma is investigated. The numerical analysis indicates that shear viscosity significantly reduces the polarization energy loss.
We consider heavy mesons with charm and bottom in nuclear medium. We construct the effective Lagrangian with axial-vector coupling including 1/M-corrections for the heavy meson mass $M$ by following the velocity-rearrangement invariance. As an application, we consider heavy mesons, $\bar{\mathrm{D}}$ and $\bar{\mathrm{D}}^{\ast}$ mesons for charm and $\mathrm{B}$ and $\mathrm{B}^{\ast}$ mesons for bottom, bound in nuclear matter, and we discuss their in-medium masses modified by the interaction with nucleons via pion exchanges including the 1/M-corrections. The mass modifications are affected …
After a few microseconds of the creation of our Universe through the Big Bang, the primordial matter was believed to be a soup of the fundamental constituents of matter -- quarks and gluons. This is expected to be created in the laboratory by colliding heavy nuclei at ultra-relativistic speeds. A plasma of quarks and gluons, called Quark-Gluon Plasma (QGP) can be created at the energy and luminosity frontiers in the Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory, New York, USA, and the Large Hadron Collider (LHC) at CERN, Geneva, Switzerland. Heavy quarks, namely the…
We determine viscosity corrections to the retarded, advanced and symmetric gluon self energies and to the static propagator in the weak-coupling "hard loop" approximation to high-temperature QCD. We apply these results to calculate the imaginary part of the heavy-quark potential which is found to be smaller (in magnitude) than at vanishing viscosity. This implies a smaller decay width of quarkonium bound states in an anisotropic plasma.
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…
We consider the possibility of a direct determination of the polarized gluon density in the proton using charm production with polarized beams at HERA. We study total cross sections and distributions at leading order using different parametrizations of the polarized gluon density. We conclude that charm photoproduction data can be used to constrain the polarized gluon density in the proton if an integrated luminosity of 100~pb$^{-1}$ will be achieved at HERA.
Charmonium directed flows are studied based on transport model coupled with the realistic three dimensional expansions of the bulk medium. The non-central symmetric nucleus-nucleus collisions can generate the rotating quark-gluon plasma (QGP) with symmetry-breaking longitudinal distributions. In $\sqrt{s_{NN}}=200$ GeV Au-Au semi-central collisions, charmonium are primordially produced in the initial hard process, they are mainly dissociated by the initial tilted source with high temperatures and then move out of the bulk medium to keep the early information of the medium. Charmonia are less a…
Lattice QCD studies on fluctuations and correlations of charm quantum number have established that deconfinement of charm degrees of freedom sets in around the chiral crossover temperature, $T_c$, i.e. charm degrees of freedom carrying fractional baryonic charge start to appear. By reexamining those same lattice QCD data we show that, in addition to the contributions from quark-like excitations, the partial pressure of charm degrees of freedom may still contain significant contributions from open-charm meson and baryon-like excitations associated with integral baryonic charges for temperatures…
The evaluation of quarkonium regeneration in ultrarelativistic heavy-ion collisions (URHICs) requires the knowledge of the heavy-quark phase space distributions in the expanding quark-gluon plasma (QGP) fireball. We employ a semi-classical charmonium transport approach where regeneration processes explicitly account for the time-dependent spectra of charm quarks via Langevin simulations of their diffusion. The inelastic charmonium rates and charm-quark transport coefficients are computed from the same charm-medium interaction. The latter is modeled by perturbative rates, augmented with a $K$-f…
Photons are a penetrating probe of the hot and dense medium created in heavy-ion collisions. We present state-of-the-art calculations of viscous photon emission from nuclear collisions at RHIC and LHC. Thermal photons anisotropic flow coefficients v_n are computed, both with and without accounting for viscous corrections to the standard thermal emission rates. These corrections are found to have a larger effect on the v_n coefficients than the viscous suppression of hydrodynamic flow anisotropies. For thermal photons, the ratio v_2{SP}/v_3{SP} shows stronger sensitivity to the quark-gluon plas…
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…
We present state-of-the-art calculations of viscous photon emission from nuclear collisions at RHIC and LHC. Fluctuating initial density profiles are evolved with event-by-event viscous hydrodynamics. Momentum spectra of thermal photons radiated by these explosively expanding fireballs and their $p_T$-differential anisotropic flow coefficients $v_n(p_T)$ are computed, both with and without accounting for viscous corrections to the standard thermal emission rates. Viscous corrections to the rates are found to have a larger effect on the $v_n$ coefficients than the viscous suppression of hydrody…
We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the Pythia event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM) which reproduces the lattice QCD equation-of-state in thermal equili…
In ultra-relativistic heavy-ion collisions, the strong electric field can be produced by the colliding nuclei. The magnitude of the electric field $E$ is on the order of $eE\sim m_π^2$ at the early stage of the collision. In quark gluon plasma (QGP), such a strong electric field can have a significant impact on the evolution of charmonia. We employ the time-dependent Schrödinger equation to study the evolution of charmonium states in the strong electric field generated by the moving charges. The electric field can result in transitions between charmonium states with different angular momenta. …
We study the properties of quarkonia inside a bulk-viscous quark gluon plasma. The non-equilibrium nature of the medium is encoded in the deformed distribution functions of thermal quarks and gluons, with which we compute the dielectric permittivity within the hard thermal loop approximation at one-loop. The modified dielectric permittivity is used to calculate the in-medium heavy quark potential, and using the potential we compute spectral functions, which reflect the physical properties of heavy quarkonia. We discuss how the bulk viscous effect influences quantities such as binding energies …
Recent theoretical explanations for how hydrodynamic-like flow can build up quickly in small collision systems (hydrodynamization) has led to a microscopic picture of flow building up in a gluon-dominated phase before chemical equilibrium between quarks and gluons has been attained. The goal of this contribution to Offshell-2021 is to explore consequence of assuming a long-lived gluon-dominated phase, which we shall denote a gluon plasma (GP). As these consequences are naturally enhanced in a large systems, we assume and explore the extreme scenario in which a GP would be created in AA collisi…
We study systematically the sensitivity of the photon structure function data on the gluon contents of the photon, by using the leading order Altarelli--Parisi (AP) equations. Charm quark contribution is studied in the quark parton model and by using the massive quark AP equations of Glück, Hoffmann and Reya. The present photon structure function data are found to allow wide range of gluon distributions in the photon. We give a set of six scale-dependent parton distributions in the photon (WHIT1 to WHIT6), which have systematically different gluon contents. Sensitivity of the structure functio…
We discuss leading charm production in connection with energy deposition in the central rapidity region. Special attention is given to the correlation between production in central and fragmentation regions. If the fraction of the reaction energy released in the central region increases the asymmetry in the $x_F$ distributions of charmed mesons will become smaller. We illustrate this quantitatively with simple calculations performed using the Interacting Gluon Model. Leading beauty production is also considered.
The Electron-Ion Collider (EIC) at Brookhaven National Laboratory will be a precision Quantum Chromodynamics machine that will enable a vast physics program with electron+proton/ion collisions across a broad center-of-mass range. Measurements of hard probes such as heavy flavor in deep inelastic scatterings will be an essential component to the EIC physics program and are one of the detector R\&D driving aspects. In this paper we study the projected statistical precision of open charm hadron production through exclusive hadronic channel reconstruction with a silicon detector concept currently …
Quarks produced in the early stage of non-central heavy-ion collisions could develop a global spin polarization along the opposite direction of the reaction plane due to the spin-orbital coupling via parton interaction in a medium that has finite longitudinal flow shear along the direction of the impact parameter. We study how such polarization evolves via multiple scattering in a viscous quark-gluon plasma with an initial laminar flow. The final polarization is found to be sensitive to the viscosity and the initial shear of local longitudinal flow.
We present a model of charmonium as two heavy quarks propagating classically in a weakly coupled quark-gluon plasma. The quarks interact via a static, color-dependent potential and also suffer collisions with the plasma particles. We calculate the radiation width of the color octet state (for fixed, classical $q\bar q$ separation) and find that it is long-lived provided a finite gluon mass is used to provide a threshold energy.
The hadroproduction of charmed mesons is discussed within the framework of the modified Quark-Gluon String model (QGSM) taking into account the decays of corresponding $S$--wave resonances like $D^*$. It is shown that the estimate of the $c\bar{c}$--pair contribution to the quark sea of colliding hadrons strongly depends on the parametrization of the function of the leading light quark fragmentation into charmed mesons. A description of the existing experimental data on inclusive spectra and asymmetries of leading and nonleading $D$ - and $D^*$ - meson production in $ πp$ -, $p p$ - and $Σp$ -…
By solving the rate equation in an expanding quark-gluon plasma, we study thermal production of charm quarks in central Pb+Pb collisions at the Future Circular Collider. With the charm quark production cross section taken from the perturbative QCD at the next-to-leading order, we find that charm quark production from the quark-gluon plasma can be appreciable compared to that due to initial hard scattering between colliding nucleons.
We analyze the capability of charm production in deep-inelastic ep scattering at HERA to constrain the gluon distribution g(y,μ^2) of the proton. The dependence of the theoretical predictions for the charm structure function F_2^c on the mass factorization scale μand the charm mass is investigated. F_2^c seems to be well suited for a rather clean and local gluon measurement at small momentum fractions y.
Leading charm production in reaction $π^- N \rightarrow DX$ is discussed.Three experiments at Fermilab and CERN have measured a rather large enhancement in production rate of leading $D^-$-mesons over nonleading $D^+$.A good description of these results is obtained in Quark Gluon String Model (QGSM) if the idea of 'intrinsic charm' is involved. The weight of the $c\bar{c}$ pairs in the quark sea of colliding hadrons is estimated from the experimental data. The comparison with other theoretical models is also carried out.
The bottom quark transport coefficients, i.e., drag and diffusion coefficients, have been studied for the collisional and soft gluon radiative processes within the viscous QCD medium. The thermal medium effects are incorporated using the effective fugacity quasiparticle model (EQPM). Both the shear and bulk viscous effects at leading order are embedded through the near-equilibrium distribution functions of the quark-gluon plasma (QGP) constituent quasiparticles. The transport coefficients' dependence on the bottom quark's initial momentum and QGP temperature has been investigated. The relative…
The heavy-quark (HQ) transport coefficients have been estimated for a viscous quark-gluon plasma medium, utilizing a recently proposed quasi-particle description based on realistic QGP equation of state (EoS). Interactions entering through the equation of state significantly suppress the temperature dependence of the drag coefficient of QGP as compared to that of an ideal system of quarks and gluons. Inclusion of shear and bulk viscosities through the corrections to the thermal phase space factors of the bath particles alters the magnitude of the drag coefficient and the enhancement is signifi…
Charmonium sum rules are analyzed with the primary goal to obtain the restrictions on the value of dimension 4 gluon condensate. The moments M_n(Q^2) of the polarization operator of vector charm currents are calculated and compared with experimental data. The 3-loop (alpha_s^2) perturbative corrections, the gluon condensate contribution with alpha_s corrections and dimension 6 operator G^3 contribution are accounted. It is shown that the sum rules for the moments do not work at Q^2=0, where the perturbation series diverges and G^3 contribution is large. The domain in the plane (n, Q^2), where …
To investigate the formation and the propagation of relativistic shock waves in viscous gluon matter we solve the relativistic Riemann problem using a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio $η/s$. We show that an $η/s$ ratio larger than 0.2 prevents the development of well-defined shock waves on time scales typical for ultrarelativistic heavy-ion collisions. These findings are confirmed by viscous hydrodynamic calculations.
In the framework of semi-hard QCD approach, we present a consistent analysis of D^* meson production at HERA energies. The consideration is based on universal unintegrated gluon densities, which have BFKL behavior in the small x region. Predictions of the CCFM evolution equation for D^* production are obtained and show a good description of D^* data at HERA.
To investigate the formation and the propagation of relativistic shock waves in viscous gluon matter we solve the relativistic Riemann problem using a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio $η/s$. Furthermore we compare our results with those obtained by solving the relativistic causal dissipative fluid equations of Israel and Stewart (IS), in order to show the validity of the IS hydrodynamics. Employing the parton cascade we also investigate the formation of Mach shocks induced by a hi…
Considering the collisional energy loss rates of heavy quarks from hard light parton interactions the total energy loss of a charm quark for a static medium has been computed. For the energy range $E\sim (5-10)$ GeV of charm quark, it is found to be almost same order as that of radiative ones estimated to a first order opacity expansion. The collisional energy loss will become much more important for lower energy charm quarks and this feature could be very interesting for phenomenology of hadrons spectra. Using such collisional energy loss rates we estimate the momentum loss distribution emplo…
Motivated by recent CLEO measurements of the B-->η' K decay, we evaluate gluon/charm content of the eta' meson using the interacting instanton liquid model of the QCD vacuum. Our result is very large due to the strong field of small-size instantons. We show that it provides quantitative explanations of the CLEO data on the B-->η' K decay rate (as well as inclusive process B-->η' X), via a virtual Cabbibo-unsuppressed decay into \bar c c pair which then becomes eta'. If so, a significant charm component should be present in other hadrons also. In particular, we found a large contribution of the…
We present a dynamical model of heavy quark evolution in the quark-gluon plasma (QGP) based on the Fokker-Planck equation. We then apply this model to the case of central ultra-relativistic nucleus-nucleus collisions performed at RHIC and estimate the component of $J/ψ$ production (integrated and differential) stemming from c-$\bar{c}$ pairs that are initially uncorrelated.
We have investigated the effect of viscosity on the gluonic dissociation of $J/ψ$ in an equilibrating plasma. Suppression of $J/ψ$ due to gluonic dissociation depend on the temperature and also on the chemical equilibration rate. In an equilibrating plasma, viscosity affects the temperature evolution and also the chemical equilibration rate, requiring both of them to evolve slowly compared to their ideal counter part. For Au+Au collisions at RHIC and LHC energies, gluonic dissociation of $J/ψ$ increases for a viscous plasma. Low $P_T$ $J/ψ$'s are found to be more suppressed due to viscosity th…
We calculate the cross section of charm photoproduction at HERA collider in the framework of the kt-factorization QCD approach. Our analysis cover the inclusive charm production as well as charm and associated jet production processes. Both photon-gluon and gluon-gluon fusion mechanisms are taken into account. The unintegrated gluon densities in a proton and in a photon obtained from the full CCFM, from unified BFKL-DGLAP evolution equations as well as from the Kimber-Martin-Ryskin prescription are used. Our theoretical results are compared with the recent experimental data taken by the H1 and…
This dissertation presents a theoretical study of soft hadron production in relativistic heavy-ion collisions. We explore the principles governing the hadronization of the expanding QGP fireball, and to understand its properties. Much of the ongoing effort is to demonstrate the validity of a QGP hadronization model which describes the particle production data accurately. We begin with a centrality study of multistrange hadrons from Au-Au collisions at 62.4 GeV at RHIC. We show that the statistical hadronization model (SHM) well describes particle production in QGP hadronization. For all centra…
In the framework of semihard (k$_T$ factorization) QCD approach, we consider the differential cross sections of $D^{*\pm}$ meson production at HERA. The consideration is based on BFKL and CCFM gluon distributions. We find that in the case of BFKL LO gluon distribution the theoretical results are sensitive to the Pomeron intercept parameter $Δ$. We present a comparison of the theoretical results with available ZEUS experimental data.
