Within the framework of the dynamical recombination approach implemented in the partonic/hadronic quark Molecular Dynamics (qMD) model, we investigate numerous QGP signals constructed from the correlations and fluctuations of conserved charges, namely charged particle ratio fluctuations, charge transfer fluctuations as well as various ratios of susceptibilities. We argue that more generally, the covariances and the variances of the conserved charges divided by the number of charged particles are a measure of the quark number susceptibilities and are thus sensitive to the phase of the system. Computations carried within samples of central qMD events from low AGS energies on ($E_{lab}=2$ AGeV) up to the highest RHIC energies available ($\sqrt{s_{NN}}=200$ GeV) show that the final state calculations are always compatible with the hadronic result. From analyses performed as a function of time with our sample of events at $\sqrt{s_{NN}}=200$ GeV, we find the recombination-like hadronization process the qMD system undergoes to be responsible for the vanishing of the early stage QGP correlations and fluctuations. These results might explain the compatibility of the measurements on charged particle ratio fluctuations with the hadronic expectations and leave no room for the experimental observation of any QGP fluctuation/correlation signals based upon the susceptibilities of the conserved charges.
We develop a three-point formalism to treat vacuum susceptibilities used for the coupling of currents to hadrons within the method of QCD Sum Rules. By introducing nonlocal condensates, with the space-time structure taken from fits to experimental parton distrbutions, we show that one can treat hadronic coupling at zero or low momentum transfer as well as medium and asmptotic momentum transfers and obtain a general expression for the vacuum susceptibilities of the two-point formalism. The pion susceptibility, for which there has been a major uncertainty, is evaluated successfully with no new p…
In a hadronic gas with three conserved charges (electric charge, baryon number, and strangeness) we employ the hadron resonance gas model to compute both diagonal and off-diagonal susceptibilities. We model the effect of chemical freeze-out in two ways: one in which all particle numbers are conserved below the chemical freeze-out temperature and one which takes into account resonance decays. We then briefly discuss possible implications these results may have on two active areas of research, hydrodynamic fluctuations and the search for the QCD critical point.
We present and test a new method to compute the hadronic vacuum polarization function in lattice simulations. This can then be used, e.g., to determine the leading hadronic contribution to the anomalous magnetic moment of the muon. The method is based on computing susceptibilities with respect to external electromagnetic plane wave fields and allows for a precision determination of both the connected and the disconnected contributions to the vacuum polarization. We demonstrate that the statistical errors obtained with our method are much smaller than those quoted in previous lattice studies, p…
We study $Λ_c^\pm$ production in $pN$ and $π^-N$ interactions. Recent experimental data from the SELEX and E791 Collaborations at FNAL provide important information on the production mechanism of charm hadrons. In particular, the production of the $Λ_c$ baryon provides a good test of the intrinsic charm and the recombination mechanisms, which have been proposed to explain the so called leading particle effects.
The triple gluon-ladder vertex is shown to project the outgoing gluon in either polarization state with equal probability up to the leading double-ln(x)ln($Q^2$) approximation. This implies that the $Q^2$-evolution of $ΔG (x, Q^2)$ is free from recombination effects to this level of approximation.
The ratios of off-diagonal and diagonal susceptibilities of conserved charges are studied using a hadron resonance gas (HRG) model with an emphasis towards providing a proper baseline for comparison to the corresponding future experimental measurements. We have studied the effect of kinematic acceptances, transverse momentum ($p_T$) and pseudorapidity ($η$), and different charged states on the ratios of the calculated susceptibilities. We find that the effect of $p_T$ and $η$ acceptance on the ratio of the susceptibilities are small relative to their dependence on the beam energy or the charge…
Inclusive distributions of soft production of mesons in hadronic collisions are calculated in the valon-recombination model. The new determination of the valon distributions from hard scattering data makes possible a tightly interrelated treatment of pion and kaon production in the fragmentation regions of proton, pion and kaon. Only one free parameter is used in the determination of the valon distribution in the kaon. No other adjustable parameter is needed to fit the $x$-distributions of the data on inclusive cross sections, except for the normalizations since the data are at fixed $p_T$. Th…
Transverse polarization of $Λ^0$ hyperons in inclusive photoproduction at x_F>0 is tackled within the framework of the quark recombination model, which has been successfully applied to the polarization of different hyperons in a variety of unpolarized hadron-hadron reactions. The results are compared with recent experimental data of HERMES.
We investigate the transverse polarization of hyperons produced by the photon induced reactions using the quark recombination model. This model reproduces polarizations of hadrons produced by the hadron-hadron collisions and accounts for the origin of the empirical rule by DeGrand and Miettinen. We find significant polarizations in the hyperon photoproduction by applying this model to the $γN \ra \Lam $ $(Σ^{0}) + X$ reaction.
We investigate extensions of the Hadron Resonance Gas (HRG) Model beyond the ideal case by incorporating both attractive and repulsive interactions into the model. When considering additional states exceeding those measured with high confidence by the Particle Data Group, attractive corrections to the overall pressure in the HRG model are imposed. On the other hand, we also apply excluded-volume corrections, which ensure there is no overlap of baryons by turning on repulsive (anti)baryon-(anti)baryon interactions. We emphasize the complementary nature of these two extensions and identify combi…
Within a dynamical quark recombination model we explore various proposed event-by-event observables sensitive to the microscopic structure of the QCD-matter created at RHIC energies. Charge fluctuations, charge transfer fluctuations and baryon-strangeness correlations are computed from a sample of central Au+Au events at the highest RHIC energy available ($\sqrt{s_{NN}}$=200 GeV). We find that for all explored observables, the calculations yield the values predicted for a quark-gluon plasma only at early times of the evolution, whereas the final state approaches the values expected for a hadro…
We study charm particle production in hadron-hadron collisions. After calculating perturbatively the charm quark differential cross section, we study the hadronization mechanisms. It is shown that recombination is the key to understand the so called Leading Particle Effect in charm meson production. For charm baryon production, however, leading particle effects are due to a combination of contributions coming from both, the recombination and the fragmentation mechanisms. We compare our calculations to experimental data on charm hadron production in $π^- N$ and $p N$ interactions from several e…
Hadronization of $Λ_c^+$ baryons from recombination model in Pb+Pb collisions at the Large Hadron Collider
College of Physics, Sichuan University（四川大学物理学院）；Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Fudan University（复旦大学现代物理研究所核物理与离子束应用教育部重点实验室）；Shanghai Research Center for Theoretical Nuclear Physics, NSFC and Fudan University（NSFC与复旦大学理论物理上海研究中心）；School of Physics and Information Technology, Shaanxi Normal University（陕西师范大学物理与信息工程学院）
利用夸克复合模型，结合轻夸克和粲夸克在热密介质中的能量损失，研究了LHC上5.02 TeV Pb+Pb碰撞中$Λ_c^+$重子的产生，成功描述了产额、$Λ_c^+/D^0$比值和方位角各向异性。
The sign structure of correlations of conserved charges are investigated in a QCD like model: the (2+1) flavor Polyakov Quark Meson model. We compute all susceptibilities of the conserved charges on the $(μ_{B}-T)$ plane up to fourth order and a few at higher order as well. By varying the mass of the sigma meson, we are able to study and compare scenarios with as well as without a critical point. In the hadron-quark transition regime we identify certain correlations that turn negative unlike expectation from ideal hadron resonance gas calculations. The striking feature being that these remain …
We construct a simple model for describing the hadron-quark crossover transition by using lattice QCD (LQCD) data in the 2+1 flavor system, and draw the phase diagram in the 2+1 and 2+1+1 flavor systems through analyses of the equation of state (EoS) and the susceptibilities. In the present hadron-quark crossover (HQC) model is successful in reproducing LQCD data on the EoS and the flavor susceptibilities.We define the hadron-quark transition temperature. For the 2+1 flavor system, the transition line thus obtained is almost identical in planes that are created by temperature and the chemical …
Fluctuations of conserved charges such as baryon number, electric charge and strangeness may provide a test for completeness of states in lattice QCD for three light flavors. We elaborate on the idea that the corresponding susceptibilities can be saturated with excited baryonic states with an underlying quark-diquark structure with a linearly confining interaction. Using Polyakov-loop correlators we show that in the static limit, the quark-diquark potential coincides with the quark-antiquark potential in marked agreement with recent lattice studies. We thus study in a quark-diquark model the b…
We calculate the 2nd and 4th order quark number susceptibilities at zero baryochemical potential, using a PNJL approach and an approach which includes, in a single model, quark and hadronic degrees of freedom. We observe that the susceptibilities are very sensitive to possible quark-quark vector interactions. Compared to lattice data our results suggest that above $T_c$ any mean field type of repulsive vector interaction can be excluded from model calculations. Below $T_c$ our results show only very weak sensitivity on the strength of the quark and hadronic vector interaction. The best descrip…
The Wroblewski parameter is a convenient indicator of strangeness production and can be employed to monitor a signal of quark-gluon plasma production : enhancement of strangeness production. It has been shown to be about a factor two higher in heavy ion collisions than in hadronic collisions. Using a method proposed by us earlier, we obtained lattice QCD results for the Wroblewski parameter from our simulations of QCD with two light quarks both below and above the chiral transition. Our first principles based and parameter free result compare well with the A-A data from SPS and RHIC.
Susceptibilities of conserved quantities, such as baryon number, strangeness and electric charge are sensitive to the onset of quantum chromodynamics (QCD) phase transition and are expected to provide information on the matter produced in heavy-ion collision experiments. A comprehensive study of the second-order diagonal susceptibilities and cross correlations has been made within a thermal model approach of the hadron resonance gas (HRG) model as well as with a hadronic transport model, UrQMD. We perform a detailed analysis of the effect of detector acceptances and choice of particle species …
The leading particle effect in charm hadroproduction is an enhancement of the cross section for a charmed hadron D in the forward direction of the beam when the beam hadron has a valence parton in common with the D. The large D+/D- asymmetry observed by the E791 experiment is an example of this phenomenon. We show that the heavy-quark recombination mechanism provides an economical explanation for this effect. In particular, the D+/D- asymmetry can be fit reasonably well using a single parameter whose value is consistent with a recent determination from charm photoproduction.
The scaling properties of elliptic flow of hadrons produced in ultrarelativistic heavy-ion collisions are investigated at low transverse momenta, $p_T\lsim 2$\,GeV. Utilizing empirical parameterizations of a thermalized fireball with collective-flow fields, Resonance Recombination Model (RRM) is employed to describe hadronization via quark coalescence at the hadronization transition. We reconfirm that RRM converts equilibrium quark distribution functions into equilibrated hadron spectra including the effects of space-momentum correlations on elliptic flow. This provides the basis for a control…
The effect of finite hadronization time is considered in the recombination model, and it is shown that the hadron multiplicity turns out to be proportional to the initial quark density and unitarity is conserved in the model. The baryon to meson ratio increases rapidly with the initial quark density due to competition among different channels.
We discuss different sources of hadron correlations in relativistic heavy ion collisions. We show that correlations among partons in a quasi-thermal medium can lead to the correlated emission of hadrons by quark recombination and argue that this mechanism offers a plausible explanation for the dihadron correlations in the few GeV/c momentum range observed in Au+Au collisions at RHIC.
We simultaneously incorporate two common extensions of the hadron resonance gas model, namely the addition of extra, unconfirmed resonances to the particle list and the excluded volume repulsive interactions. We emphasize the complementary nature of these two extensions and identify combinations of conserved charge susceptibilities that allow to constrain them separately. In particular, ratios of second-order susceptibilities like $χ_{11}^{BQ}/χ_2^B$ and $χ_{11}^{BS}/χ_2^B$ are sensitive only to the baryon spectrum, while fourth-to-second order ratios like $χ_4^B/χ_2^B$, $χ_{31}^{BS}/χ_{11}^{B…
We argue that the collinear factorization of the fragmentation functions in high energy hadron and nuclei collisions breaks down at transverse momenta kT < Qs/g due to high parton densities in the colliding hadrons and/or nuclei. We calculate, at next-to-leading order in projectile parton density and to all orders in target parton density, the double-inclusive cross section for production of a pair of gluons in the scalar J^(PC)=0^(++) channel. Using the low energy theorems of QCD we find the inclusive cross section for pi-meson production.
Second-order susceptibilities $χ^{11}_{ij}$ of baryon, electric, and strangeness, $B$, $Q$, and $S$, charges, are calculated in the Chiral Mean Field (CMF) model and compared to available lattice QCD data. The susceptibilities are sensitive to the short range repulsive interactions between different hadron species, especially to the hardcore repulsion of hyperons. Decreasing the hyperons size, as compared to the size of the non-strange baryons, does improve significantly the agreement of the CMF model results with the Lattice QCD data. The electric charge-dependent susceptibilities are sensiti…
We propose to model hadronization of parton showers in QCD jets through a hybrid approach involving quark recombination and string fragmentation. This is achieved by allowing gluons at the end of the perturbative shower evolution to undergo a non-perturbative splitting into quark and antiquark pairs, then applying a Monte-Carlo version of instantaneous quark recombination, and finally subjecting remnant quarks (those which have not found a recombination partner) to Lund string fragmentation. When applied to parton showers from the PYTHIA Monte Carlo event generator, the final hadron spectra fr…
$SU(N_c)$ colour-singlet restriction, along with flavour and spin symmetry, on thermal partonic ensemble is shown to recombine the partons with internal colour structure into colour-singlet multi-quark clusters which can be identified with various hadronic modes at a given temperature. This provides a possible basis for recombination model for hadronization of quark-gluon plasma. This also leads to a natural explanation for the ratio of (anti)protons to pions and the quark number scaling of the elliptic flow coefficient in relativistic heavy-ion collisions.
In this work the susceptibility coefficients of the strange and non-strange quark number of second and fourth order are presented. The results at zero baryonchemical potential are obtained using a well tested chiral effective model including all known hadron degrees of freedom and additionally incorporating quarks and gluons in a PNJL model approach. Quark number susceptibilities are sensitive to the fundamental degrees of freedom in the model and signal the shift from massive hadrons to light quarks at the deconfinement transition by a sharp rise at the critical temperature. Furthermore, all …
We discuss hadron production in heavy ion collisions at RHIC. We argue that hadrons at transverse momenta P_T < 5 GeV are formed by recombination of partons from the dense parton phase created in central collisions at RHIC. We provide a theoretical description of the recombination process for P_T > 2 GeV. Below P_T = 2 GeV our results smoothly match a purely statistical description. At high transverse momentum hadron production is well described in the language of perturbative QCD by the fragmentation of partons. We give numerical results for a variety of hadron spectra, ratios and nuclear sup…
Within the framework of the constituent quark model, it is shown that the single hadron fragmentation function of a parton can be expressed as a convolution of shower diquark or triquark distribution function and quark recombination probability, if the interference between amplitudes of quark recombination with different momenta is neglected. The recombination probability is determined by the hadron's wavefunction in the constituent quark model. The shower diquark or triquark distribution functions of a fragmenting jet are defined in terms of overlapping matrices of constituent quarks and part…
We study the production of multi-charmed hadrons by recombination in heavy ion collisions by focusing on the production of $Ξ_{cc}$, $Ξ_{cc}^*$, $Ω_{scc}$, $Ω_{scc}^*$, $Ω_{ccc}$ baryons and X(3872) mesons. Starting from the estimation of yields for those hadrons at chemical freeze-out in both the statistical and coalescence model, we evaluate their transverse momentum distributions at mid-rapidity in the coalescence model. We show that yields of multi-charmed hadrons in heavy ion collisions at RHIC and LHC are large enough, and thereby not only multi-charmed hadrons observed so far, e.g., the…
When quarks hadronize, they accelerate. Because they carry electric charge, they must radiate light as they accelerate and hadronize. This is true not only in jets but also in heavy ion collisions, where a thermalized plasma of quarks and gluons cools into a gas of hadrons. First, direct emission of photons from two quarks coalescing into pions is calculated using the quark-meson model. The yield of final-state photons to pions is found to be about $e^2/g^2_{πqq}$, which is on the order of a percent. Second, the yield of photons from the decay of highly excited color singlets, which may exist …
Nonperturbative effects in $D$-meson production in pion-nucleon and proton-nucleon collisions are investigated within the recombination model. The coalescence of perturbatively created charm quarks with sea- and valence-quarks from projectile and target fragments is shown to be competitive in magnitude with standard fragmentation calculations at both central (small $x_F$) and forward rapidities. Corresponding flavor asymmetries for inclusive $D$-meson production are thus mostly generated on the (light-) parton distribution level, and turn out to be in reasonable overall agreement with availabl…
Based on the proper-time renormalization group approach, the scalar and the quark number susceptibilities in the vicinity of possible critical end points of the hadronic phase diagram are investigated in the two-flavor quark-meson model. After discussing the quark-mass dependence of the location of such points, the critical behavior of the in-medium meson masses and quark number density are calculated. The universality classes of the end points are determined by calculating the critical exponents of the susceptibilities. In order to numerically estimate the influence of fluctuations we compare…
We present the calculation of the inclusive x_F-distributions of charmed hadrons, produced in high-energy $Σ^-$-beam. Our calculation is based on the modified mechanism of charmed quarks fragmentation as well as on the mechanism of c-quark recombination with the valence quarks from initial hadrons.
The quark recombination mechanism is proposed to explain the asymmetry between production rates of $D^+$ and of $D^-$ in their inclusive productions, and also asymmetries for other charmed hadrons. These asymmetries are observed in experiment and are called as leading particle effects. In this work we give a general analysis for contributions of quark recombination to these asymmetries. The contributions consist of a perturbative- and nonperturbative part. We perform two types of factorization by considering the produced hadron with large transverse momentum and by taking charm quark as a heav…
We present an extension of the recombination formalism to analyze the effects from the variation of the hadron wavefunctions. The hadron spectra are sensitive to the shape of the wavefunctions. However, when we fit the wavefunction parameters to the physical observables, such as the average charge radius, the final spectra are very similar each other. We discuss our numerical results in comparison with the published PHENIX and STAR data at RHIC. In the hadron spectra, the recombination of thermal partons dominates at intermediate transverse momentum ($P_{T}$ = 2 $\sim$ 5 GeV), and the fragment…
The quantum van der Waals (QvdW) extension of the ideal hadron resonance gas (HRG) model which includes the attractive and repulsive interactions between baryons -- the QvdW-HRG model -- is applied to study the behavior of the baryon number related susceptibilities in the crossover temperature region. Inclusion of the QvdW interactions leads to a qualitatively different behavior of susceptibilities, in many cases resembling lattice QCD simulations. It is shown that for some observables, in particular for $χ_{11}^{BQ} / χ_2^B$, effects of the QvdW interactions essentially cancel out. It is foun…
We briefly review the recent advances of heavy-quark recombination mechanism. This mechanism predicts a class of power-suppressed 3-jet events in $Z^0$ decay, such as $b\bar{b}q$ and $b\bar{b}\bar{q}$. Furthermore, heavy quark fragmentation function also receives a contribution from this mechanism. Some light can be shed on the scaling of the maximum of the fragmentation function for S-wave heavy hadrons. We finally comment on a new variant of this mechanism which has important impact on the precision electroweak physics.
We analyze the applicability of perturbative QCD (pQCD) approach to the issue of $J/ψ$ recombination at the Large Hadron Collider (LHC), and calculate the recombination cross section for $c\bar{c}$ recombination to form $J/ψ$ as a function of temperature. The charmonium wavefunction is obtained by employing a temperature dependent phenomenological potential between the $c\bar{c}$ pair. The temperature dependent formation time of charmonium is also employed in the current work. A set of coupled rate equations is established which incorporates color screening, gluonic dissociation, collisional d…
We study the elliptic flow $v_2$ of multi-strange hadrons such as the $ϕ$, $Ξ$ and $Ω$ as a function of transverse momentum in the recombination and fragmentation model and compare to a standard hydrodynamic calculation. We find that the measurement of $v_2$ for the $ϕ$ and $Ω$ will allow for the unambiguous distinction between parton recombination and statistical hadro-chemistry to be the dominant process in hadronization at intermediate transverse momenta.
We investigate photon emission at the hadronization stage from a quark-gluon plasma created in relativistic heavy-ion collisions. A recombination-model picture suggests that a quark and an antiquark bind into a meson state in hadronization, which would apparently violate the energy conservation if there is nothing else involved. We consider here a hadronization process where the recombination accompanies a photon emission. This is an analog of the "{\it radiative recombination}" known in plasma physics, such as $e^- + p^+ \to {\rm H}^0 +γ$, which occurs when an electromagnetic plasma goes back…
We have estimated the susceptibilities of conserved charges for 2-flavor strongly interacting matter with varying system sizes, using the Polyakov loop enhanced Nambu Jona-Lasinio model. The susceptibilities for vanishing baryon densities are found to show a scaling with the system volume in the hadronic as well as partonic phase. This scaling breaks down for a temperature range of about 30-50 MeV around the cross-over region. Simultaneous measurements of the various susceptibilities may thus indicate how close to the cross-over region the freeze-out occurs for the fireball created in heavy-io…
Quark number susceptibilities as computed in lattice QCD are commonly believed to provide insights into the microscopic structure of QCD matter, in particular its degrees of freedom. We generalize a previously constructed partonic $T$-matrix approach to finite chemical potential to calculate various susceptibilities, in particular for configurations containing a heavy charm quark. At vanishing chemical potential and moderate temperatures, this approach predicts large collisional widths of partons generated by dynamically formed hadronic resonance states which lead to transport parameters chara…
We calculate diffusion and hadronization of heavy quarks in high-energy heavy-ion collisions implementing the notion of a strongly coupled quark-gluon plasma in both micro- and macroscopic components. The diffusion process is simulated using relativistic Fokker-Planck dynamics for elastic scattering in a hydrodynamic background. The heavy-quark transport coefficients in the medium are obtained from non-perturbative $T$-matrix interactions which build up resonant correlations close to the transition temperature. The latter also form the basis for hadronization of heavy quarks into heavy-flavor …
We present a study of the contribution of antishadowing effects on the gluon distribution functions $G(x,Q^2)$ in light of the Gribov-Levin-Ryskin-Mueller-Qiu, Zhu-Ruan-Shen (GLR-MQ-ZRS) nonlinear equation at small-$x$, where $x$ is the momentum fraction or Bjorken variable and $Q^2$ is the four momentum transfer squared or photon virtuality. In this work, we have solved the GLR-MQ-ZRS nonlinear equation using Regge like the behavior of gluons in the kinematic range of $10^{-2}\leq x \leq 10^{-6}$ and $5\,GeV^2\, \leq Q^2\leq 100\, GeV^2$ respectively. We have obtained the solution of $G(x,Q^2…
Understanding the hadronization of the quark-gluon plasma (QGP) remains a challenging problem in the study of strong-interaction matter as produced in ultrarelativistic heavy-ion collisions (URHICs). The large mass of heavy quarks renders them excellent tracers of the color neutralization process of the QGP when they convert into various heavy-flavor (HF) hadrons. We develop a 4-momentum conserving recombination model for HF mesons and baryons that recovers the thermal and chemical equilibrium limits and accounts for space-momentum correlations (SMCs) of heavy quarks with partons of the hydrod…
We consider the $(2+1)$ flavor Polyakov Quark Meson Model and study the fluctuations (correlations) of conserved charges upto sixth (fourth) order. Comparison is made with lattice data wherever available and overall good qualitative agreement is found, more so for the case of the normalised susceptibilities. The model predictions for the ratio of susceptibilities go to that of an ideal gas of hadrons as in Hadron Resonance Gas Model at low temperatures while at high temperature the values are close to that of an ideal gas of massless quarks. Our study provides a strong basis for the use of PQM…
Quark Number Susceptibilities and Conserved Charge Fluctuations in $(2+1)$-flavor QCD with Möbius domain-wall fermions (MDWF)
Universität Bielefeld（比勒费尔德大学）；RIKEN Center for Computational Science (R-CCS)（理化学研究所计算科学中心）；Osaka University（大阪大学）；High Energy Accelerator Research Organization (KEK)（高能加速器研究机构）；Graduate University for Advanced Studies (SOKENDAI)（综合研究大学院大学）
We present a new model for the description of heavy-quark hadronization in relativistic heavy-ion collisions in the presence of a reservoir of lighter thermal particles with which recombination can occur leading to the formation of color-singlet clusters. Color neutralization is assumed to occur locally, within the same fluid cell occupied by the heavy quark and it proceeds via the recombination of the latter with light antiquarks (quarks) or diquarks (anti-diquarks), which are assumed to be present in the medium with thermal abundance as effective degrees of freedom around the QCD crossover t…
We study QCD thermodynamics in presence of two independent imaginary chemical potentials coupled to two degenerate flavors of staggered quarks. Analytic continuation is used to determine non-linear susceptibilities, to test the Hadron Resonance Gas (HRG) model below the zero density critical temperature, Tc, and to determine the average phase factor of the fermion determinant. Deviations from HRG predictions, of the order of a few percent, are clearly visible for temperatures T > 0.95 Tc. The determination of non-linear susceptibilities, using different interpolating functions for analytic con…
Asymmetries in the hadroproduction of charm particles directly probe power corrections to the QCD factorization theorems. In this paper, the heavy-quark recombination mechanism, a power correction that explains charm meson asymmetries, is extended to charm baryons. In this mechanism, a light quark participates in the hard scattering that creates a charm quark and they hadronize together into a charm baryon. This provides a natural and economical explanation for the Λ_c^+/Λ_c^- asymmetries measured in πN and p N collisions.
We discuss two-photon and hadronic production of $B_c$ mesons in nonrelativistic bound state approximation and to lowest order in the coupling constants $α$ and $α_s$. It is shown that in photon-photon collisions, heavy quark fragmentation is dominated by recombination of $\bar b$ and $c$ quarks up to the highest accessible transverse momenta. In contrast, in hadroproduction, which at high energies mainly involves gluon--gluon collisions, the fragmentation mechanism dominates at transverse momenta $p_T > m_{B_c}$, providing a simple and satisfactory approximation of the complete $O(α_s^4)$ res…
