Flavor ordering of elliptic flows at high transverse momentum

Based on the quark coalescence model for the parton-to-hadron phase transition in relativistic heavy ion collisions, we relate the elliptic flow (upsilon(2)) of high p(T) hadrons to that of high p(T) quarks. For high p(T) hadrons produced from an isospin-symmetric and quark-antiquark-symmetric partonic matter, magnitudes of their elliptic flows follow a flavor ordering as (upsilon(2,pi)=upsilon(2,N))>(upsilon(2,Lambda)=upsilon(2,Sigma))>upsilon(2,K)>upsilon(2,Xi)>(upsilon(2,phi)=upsilon(2,Omega)) if strange quarks have a smaller elliptic flow than light quarks. The elliptic flows of high p(T) hadrons further follow a simple quark counting rule if strange quarks and light quarks have the same high p(T) spectrum and coalescence probability.     

Azimuthal dependence of two-particle transverse momentum current correlations

The European Physical Journal C - We present a study on inclusive emissions of a double $$\Lambda _c$$ or of a $$\Lambda _c$$ plus a light-flavored jet system as probe channels in the semi-hard...     

Influence of the momentum dependence of nuclear interactions on heavy-ion potentials

We analyse the momentum dependence of nucleus-nucleus interactions and compare the predictions for this dependence obtained from nonrelativistic Skyrme forces, from relativistic mean field models and from phenomenological ansätze used in data analyses. In all cases the momentum dependence is determined by the effective mass alone and is therefore the same for relativistic and nonrelativistic models.     

The transverse momentum dependence of quark fragmentation functions from cascade models

A covariant generalization of the one-dimensional cascade model for quark fragmentation functions is presented, so as to include the transverse momentum behaviour and the possibility to produce different particles at different vertices along the chain. In the scaling limit the exact solution is given, if the primordial function is of the type αz ^α?1·T(p _T ). For the more general case of factorizing primordial functions an analytic expression for the seagull effect is derived, which turns out to be independent of the functionT(p _T ).     

Cold nuclear matter effects on production: Intrinsic and extrinsic transverse momentum effects

Cold nuclear matter effects on J/ψ production in proton–nucleus and nucleus–nucleus collisions are evaluated taking into account the specific J/ψ-production kinematics at the partonic level, the shadowing of the initial parton distributions and the absorption in the nuclear matter. We consider two different parton processes for the -pair production: one with collinear gluons and a recoiling gluon in the final state and the other with initial gluons carrying intrinsic transverse momentum. Our results are compared to RHIC observables. The smaller values of the nuclear modification factor R_AA in the forward rapidity region (with respect to the mid rapidity region) are partially explained, therefore potentially reducing the need for recombination effects.     

Measuring shear viscosity using transverse momentum correlations in relativistic nuclear collisions

Elliptic flow measurements at the Brookhaven National Laboratory Relativistic Heavy Ion Collider suggest that quark-gluon fluid flows with very little viscosity compared to weak-coupling expectations, challenging theorists to explain why this fluid is so nearly "perfect." It is therefore vital to find quantitative experimental information on the viscosity of the fluid. We propose that measurements of transverse momentum fluctuations can be used to determine the shear viscosity. We use current data to estimate the viscosity-to-entropy ratio in the range from 0.08 to 0.3 and discuss how future measurements can reduce this uncertainty.     

Process dependence of the target jet remnants in the photoproduction of large transverse momentum jets

We use the quark recombination model of Das and Hwa to predict the inclusive meson spectra (π⁺, π^?,K ⁺,K ^?) in the target fragmentation region for processes in which a large transverse momentum jet is produced by a nearly real photon. We find that the antiparticle ratios of such target jet mesons are sensitive to the type of process which has produced the largep _t jet. By comparing the ratios found in photoproduction to those in deep inelastic scattering we point out that it is in principle possible to identify the presence of the Bethe-Heitler photoproduction subprocess. We conclude that the target jet remnants can contribute to separating the subprocesses responsible for the photoproduction of largep _t jets.     

Transverse radius dependence for transverse velocity and elliptic flow in intermediate energy HIC

The mean transverse velocity and elliptic flow of light fragments (A≤2) as a function of transverse radius are studied for 25 MeV/nucleon <'64>Cu+<'64>Cu collisions with impact parameters 3-5 fm by the isospin- dependent quantum molecular dynamics model. By comparison between the in-plane and the out-of-plane transverse velocities, the elliptic flow dependence on the transverse radius can be understood qualitatively, and variation of the direction of the resultant force on the fragments can be investigated qualitatively.     

Transverse radius dependence for transverse velocity and elliptic flow in intermediate energy HIC

The mean transverse velocity and elliptic flow of light fragments (A ≤ 2) as a function of transverse radius are studied for 25 MeV/nucleon ⁶⁴Cu+⁶⁴Cu collisions with impact parameters 3--5 fm by the isospin-dependent quantum molecular dynamics model. By comparison between the in-plane and the out-of-plane transverse velocities, the elliptic flow dependence on the transverse radius can be understood qualitatively, and variation of the direction of the resultant force on the fragments can be investigated qualitatively.     

Evidence for explicit angular momentum dependence of the proton optical model potential

Proton elastic scattering and polarization data, unfittable with a local OM potential, can be fitted very well if explicitly l-dependent real and imaginary components are introduced. The improvement, like that obtained by including pickup channel coupling, suggests that pickup channels generate a component with no l-independent local equivalent.     

Shadowing effects and transverse momentum dependence of particle emission in intermediate energy heavy ion collisions

Light particle emission was studied at Ganil for ³⁶ Ar +²⁷ Al between 55 and 95 MeV/u and for ⁶⁴ Zn+⁵⁸ Ni between 35 and 79 MeV/u. The correlation of these particles with the reaction plane was analyzed. In intermediate impact parameter events, the transverse momentum dependence of this correlation changes drastically with the energy for midrapidity particles. For both systems, at the upper incident energies, particles with highest transverse momenta are preferentially emitted perpendicular to the reaction plane. This can be qualitatively reproduced by simulations taking into account shadowing effects.     

Density dependence of the single-particle potential in nuclear matter

The single-particle potential in infinite nuclear matter is computed as a function of density and energy in a variety of relativistic mean-field models of nuclear matter. A comparison of this potential is made with that computed by Friedman and Pandharipande using the variational method. We also show that the self-consistent mean-field Hartree approximation satisfies the Hugenholtz-van Hove theorem. High-density behavior of the single-particle potential is considered.     

The nuclear size dependence of large momentum transfer scattering and quark interaction dynamics

A simple dynamical picture for hadron interactions is used to discuss the A dependence of large p_⊥ scattering and dilepton production. Observations in large p_⊥ experiments are explained. Important corrections to dilepton production cross sections are found, leading to acceptable agreement between colored-quark theory and experiment.     

The transverse momentum of partons

It is shown that when the parton model is formulated in proper, covariant fashion the average transverse momentum of the partons in a hadron varies with their fractional longitudinal momentum x. It is small near x = 0, but could rise to a large as x → 1.     

Implication of the EMC-effect on high transverse momentum jets

We show that the extension of nuclear structure functions to the regionx>1 can give rise to an enhancement of high-p _T jet cross sections in hadron nucleus collisions. Such extensions are expected in a class of models proposed to explain the EMC-effect. Since these models are completely parametrized by the deep inelastic scattering data, the jet cross section emerge as parameter free predictions.     

On the intrinsic transverse momentum of partons

Using simple assumptions it is shown that the average transverse momentum of partons is determined by their structure functions. The x-dependence obtained this way agrees well with the experimental data. The size is controlled by the invariant mass of the nucleon core and the behaviour of the structure functions near x = 1. We obtain a lower limit for the intrinsic contribution to 〈k_⊥〉_μμ of ～ 400 MeV.     

Large transverse momentum and jet studies

Particle production at large transverse momentum is found to exceed by a large amount what is expected from the collision of two extended objects about 1 fermi across. The pertinent effects are associated with collisions among hadron constituents which materialized as jets of particles. Experimental evidence for a jet configuration is reviewed. A phenomenological analysis of the key features of jet fragmentation is then presented. It is based on the scaling properties of hadronic interactions. Theoretical models are reviewed and in particular the relevance of quantum chromodynamics is assessed. The paper ends with a discussion of future prospects at present machines and also considers the use of present synchrotrons in their collider version.     

Collective flow model for the pion transverse momentum spectra from relativistic nuclear collisions at CERN

The transverse momentum spectra for pions observed by WA80 and NA35 collaborations are analysed within a fireball model with collective isentropic expansion and a realistic freeze-out criterion. By varing the initial state of the fireball, an excellent fit to the data is achieved for the whole measured range ofP _T . Slight differences in the data for the spectral slopes from central and pheripheral collisions originate in our model from the difference in the size of the fireball and in the number of participating nucleons in central and peripheral collisions. Using additional information from two-pion correlations, we can extrapolate our model back from the freeze-out point (determined from the spectra) to the initial state; we find that an initial energy density of 1.5–2GGeV/fm³ is sufficient to explain the data from central O+Au collisions at 200A GeV.