Search

We calculate the O(αs³) short-distance, QCD collinear-factorized coefficient functions for all partonic channels that include the production of a heavy quark pair at short distances. This provides the first power correction to the collinear-factorized inclusive hadronic production of heavy quarkonia at large transverse momentum, pT, including the full leading-order perturbative contributions to the production of heavy quark pairs in all color and spin states employed in NRQCD treatments of this process. We discuss the role of the first power correction in the production rates and the polarizations of heavy quarkonia in high-energy hadronic collisions. The consistency of QCD collinear factorization and nonrelativistic QCD factorization applied to heavy quarkonium production is also discussed. [ABSTRACT FROM AUTHOR]

We present a perturbative QCD factorization formalism for inclusive production of heavy quarkonia of large transverse momentum, pT at collider energies, including both leading power (LP) and next-to-leading power (NLP) behavior in pT. We demonstrate that both LP and NLP contributions can be factorized in terms of perturbatively calculable short-distance partonic coefficient functions and universal nonperturbative fragmentation functions, and derive the evolution equations that are implied by the factorization. We identify projection operators for all channels of the factorized LP and NLP infrared safe short-distance partonic hard parts, and corresponding operator definitions of fragmentation functions. For the NLP, we focus on the contributions involving the production of a heavy quark pair, a necessary condition for producing a heavy quarkonium. We evaluate the first nontrivial order of evolution kernels for all relevant fragmentation functions, and discuss the role of NLP contributions. [ABSTRACT FROM AUTHOR]

Induced by three gluons symmetry, Mandelstam variables s, t, u symmetric expressions are widely involved in collider physics, especially in heavy quarkonium physics. In this work we study the general form of s, t, u symmetric polynomials, and find that they can be expressed as polynomials where the symmetry is manifest. The general form is then used to simplify expressions which asymptotically reduces the length of original expression to one-sixth. Based on the general form, we reproduce the exact differential cross section of J/? hadron production at leading order in ν2 up to four unknown constant numbers by simple analysis. Furthermore, we prove that differential cross section at higher order in ν2 is proportional to that at leading order. This proof explains the proportion relation at next-to-leading order in ν2 found in previous work and generalizes it to all order. [ABSTRACT FROM AUTHOR]

We study O(αsv2) corrections to decays of 1S0 heavy quarkonium into light hadrons and two photons within the framework of nonrelativistic QCD and find these O(αsv2) corrections to have significant contributions especially for the decay into light hadrons. With these new results, experimental measurements of the hadronic width and the γγ width of ηc can be described more consistently. By fitting experimental data, we find the long-distance matrix elements of ηc to be ∣Rηc(0)∣2=0.834-0.197+0.281??GeV3 and «v2»ηc=0.232-0.098+0.121. Moreover, ηc(2S) is also discussed and the γγ decay width is predicted to be 3.34-2.10+2.06??KeV. [ABSTRACT FROM AUTHOR]

The widely used nonrelativistic QCD (NRQCD) factorization theory now encounters some notable difficulties in describing quarkonium production. This may be due to the inadequate treatment of soft hadrons emitted in the hadronization process, which causes bad convergence of velocity expansion in NRQCD. In this paper, starting from QCD we propose a rigorously defined factorization approach, soft gluon factorization (SGF), to better deal with the effects of soft hadrons. After a careful velocity expansion, the SGF can be as simple as the NRQCD factorization in phenomenological studies, but has a much better convergence. The SGF may provide a new insight to understand the mechanisms of quarkonium production and decay. [ABSTRACT FROM AUTHOR]

Fragmentation is the dominant mechanism for hadron production with high transverse momentum. For spin-triplet S-wave heavy quarkonium production, contribution of gluon fragmenting to color-singlet channel has been numerically calculated since 1993. However, there is still no analytic expression available up to now because of its complexity. In this paper, we calculate both polarization-summed and polarized fragmentation functions of gluon fragmenting to a heavy quark-antiquark pair with quantum number ³S1[1]. Our calculations are performed in two different frameworks. One is the widely used nonrelativistic QCD factorization, and the other is the newly proposed soft gluon factorization. In either case, we calculate at both leading order and next-to-leading order in velocity expansion. All of our final results are presented in terms of compact analytic expressions. [ABSTRACT FROM AUTHOR]

We propose an improved version of the color evaporation model to describe heavy quarkonium production. In contrast to the traditional color evaporation model, we impose the constraint that the invariant mass of the intermediate heavy quark-antiquark pair be larger than the mass of produced quarkonium. We also introduce a momentum shift between the heavy quark-antiquark pair and the quarkonium. Numerical calculations show that our model can describe the charmonium yields as well as the ratio of ψ ′ over J / ψ better than the traditional color evaporation model. [ABSTRACT FROM AUTHOR]

Using the guage/gravity correspondence, we study the free energy, entropy, binding energy, and internal energy of a heavy quarkonium in the rotating quark-gluon plasma (QGP). First, we extend the static black hole with planar horizon to the spinning case, which is dual to the rotating matter. Subsequently, we use the Wilson loop to get the free energy of heavy quarkonium. Entropy, binding energy, and internal energy are naturally given by the thermodynamic relationship. It is found that angular velocity will suppress the dissociation temperature of heavy quarkonium and change the system from confined to deconfined phase with the increase of angular velocity. Thus, the heavy quarkonium will dissolve at a certain separating distance in the deconfined phase. We also compare these thermodynamic quantities of the quark-antiquark pair in the direction parallel and transverse to the rotation direction. At last, the free energy, entropy, and internal energy of a single quark are discussed. It is found that these quantities are decreasing functions of temperature. [ABSTRACT FROM AUTHOR]

We study the effect of magnetic field on heavy quark-antiquark pair in both Einstein-Maxwell (EM) and Einstein-Maxwell-dilaton (EMD) model. The interquark distance, free energy, entropy, binding energy, and internal energy of the heavy quarkonium are calculated. It is found that the free energy suppresses and the entropy increases quickly with the increase of the magnetic field B. The binding energy vanishes at smaller distance when increasing the magnetic field, which indicates the quark-antiquark pair dissociates at smaller distance. The internal energy which consists of free energy and entropy will increase at large separating distance for a nonvanishing magnetic field. These conclusions are consistent both in the EM and EMD model. Moreover, we also find that the quarkonium will dissociate easier in the parallel direction than that in the transverse direction for EMD model, but the conclusion is opposite in EM model. Lattice results are in favor of EMD model. Besides, a Coulomb-plus-linear potential (Cornell potential) can be realized only in EMD model. Thus, a dilaton field is proved to be important in holographic model. Finally, we also show that the free energy, entropy, and internal energy of a single quark in EMD model with the presence of magnetic field. [ABSTRACT FROM AUTHOR]