8213519
EFFECTS OF DENSE MATTER ON HADRON PRODUCTION IN HEAVY-ION COLLISIONS ‡
The intrinsic transverse momentum distribution of partons in the nucleon can be used to explain a large amount of high-pT hadron and photon production data in high-energy nucleon-nucleon collisions at energies √ s ≈ 20 to 1800 GeV. However, proton-nucleus experiments at energies ≈ 30 GeV show an extra enhancement (Cronin effect) in the yield of photons and mesons compared to a simple extrapolation of the proton-proton data. This enhancement is due to the effect of the dense hadronic matter encountered by the projectile proton in the nuclear environment. We discuss the origin and the properties of the nuclear enhancement.
17260983
Differences in high $p_t$ meson production between CERN SPS and RHIC heavy ion collisions
In this talk we present a perturbative QCD improved parton model calculation for light meson production in high energy heavy ion collisions. In order to describe the experimental data properly, one needs to augment the standard pQCD model by the transverse momentum distribution of partons ("intrinsic k_T"). Proton-nucleus data indicate the presence of nuclear shadowing and multiscattering effects. Further corrections are needed in nucleus-nucleus collisions to explain the observed reduction of the cross section. We introduce the idea of proton dissociation and compare our calculations with the SPS and RHIC experimental data.
119470349
Kaon Fragmentation Function and $K/\pi$ Ratios in Nuclear Collisions
An improved leading order fragmentation functions set of kaon is proposed based on the experimental data. We compare it with currently available sets, and use it to calculate high-$p_T$ $K/\pi$ ratios in relativistic proton-proton collisions. A prediction of $K/\pi$ ratios in relativistic nucleus-nucleus collisions ($d + Au$ and $Au + Au$) at RHIC $\sqrt{s} = 200$ GeV is given.
117218759
Particle production in relativistic heavy-ion collisions with perturbative QCD
14368189
ON TYPE I QUANTUM AFFINE SUPERALGEBRAS
The type I simple Lie superalgebras are sl(m|n) and osp(2|2n). We study the quantum deformations of their untwisted affine extensions Uq[sl(m|n)(1)] and Uq[osp(2|2n)(1)]. We identify additional relations between the simple generators (“extra q Serre relations”) which need to be imposed in order to properly define Uq[sl(m|n)(1)] and Uq[osp(2|2n)(1)]. We present a general technique for deriving the spectral-parameter-dependent R matrices from quantum affine superalgebras. We determine the R matrices for the type I affine superalgebra Uq[sl(m|n)(1)] in various representations, thereby deriving new solutions of the spectral-parameter-dependent Yang-Baxter equation. In particular, because this algebra possesses one-parameter families of finite-dimensional irreps, we are able to construct R matrices depending on two additional spectral-parameter-like parameters, providing generalizations of the free fermion model.
5210708
Bethe ansatz solutions to quasi exactly solvable difference equations
Bethe ansatz formulation is presented for several explicit examples of quasi exactly solvable difference equations of one degree of freedom which are introduced recently by one of the present authors. These equations are deformation of the well-known exactly solvable difference equations of the Meixner-Pollaczek, continuous Hahn, continuous dual Hahn, Wilson and Askey-Wilson polynomials. Up to an overall factor of the so-called pseudo ground state wavefunction, the eigenfunctions within the exactly solvable subspace are given by polynomials whose roots are solutions of the associated Bethe ansatz equations. The corresponding eigenvalues are expressed in terms of these roots.
15601411
Quasi-Hopf superalgebras and elliptic quantum supergroups
We introduce the quasi-Hopf superalgebras which are Z(2)-graded versions of Drinfeld's quasi-Hopf algebras. We describe the realization of elliptic quantum supergroups as quasi-triangular quasi-Hopf superalgebras obtained from twisting the normal quantum supergroups by twistors which satisfy the graded shifted cocycle condition, thus generalizing the quasi-Hopf twisting procedure to the supersymmetric case. Two types of elliptic quantum supergroups are defined, that is, the face type B-q,B-lambda(G) and the vertex type A(q,p)[sl(((n\) over cap\n)] (and A(q,p)[gl ((n\) over cap n)], where G is any Kac-Moody superalgebra with symmetrizable generalized Cartan matrix. It appears that the vertex type twistor can be constructed only for U-q[sl ((n\) over cap n) in a nonstandard system of simple roots, all of which are fermionic. (C) 1999 American Institute of Physics. [S0022-2488(99)00210-8].
124303693
Effective Masses of Mesons and Nucleon in Hot Medium for the Walecka Model
Based on the thermo-field dynamics, the temperature and density dependencies of the effective masses of σ, ω mesons and nucleon in the walecka model have been calculated. The vacuum fluctuation effect is examined. It is found that the vacuum fluctuation is very important and leads to a reduction of ω-meson mass and an enhancement of σ-meson mass in hot and dense medium.
119177672
Pair production of heavy quarkonium and B(*)c mesons at hadron colliders
We investigate the pair production of S-wave heavy quarkonium at the LHC in the color-singlet mechanism (CSM) and estimate the contribution from the gluon fragmentation process in the color-octet mechanism (COM) for comparison. With the matrix elements extracted previously in the leading-order calculations, the numerical results show that the production rates are quite large for the pair production processes at the LHC. The p t distribution of double J/ψ production in the CSM is dominant over that in the COM when p t is smaller than about 10 GeV. For the production of double Y, the contribution of the COM is always larger than that in the CSM. The large differences in the theoretical predictions between the CSM and COM for the p t distributions in the large p t region are useful in clarifying the effects of COM on the quarkonium production. We also investigate the pair production of S-wave B c and B* c mesons, and the measurement of these processes is useful to test the CSM and extract the long-distance matrix elements for the B c and B* c mesons. Aside from numerical calculations, analytical expressions for the production differential cross sections of all these processes are also given.