We analyze a generic model where wounded quarks are amended with strings in which both endpoint positions fluctuate in spatial rapidity. With the assumption that the strings emit particles independently of one another and with a uniform distribution in rapidity, we are able to analyze the model semi-analytically, which allows for its detailed understanding. Using as a constraint the one-body string emission functions obtained from the experimental data for collisions at √ sNN = 200 GeV, we explore the two-body correlations for various scenarios of string fluctuations. We find that the popular measures used to quantify the longitudinal fluctuations (anm coefficients) are limited with upper and lower bounds. These measures can be significantly larger in the model where both end-point are allowed to fluctuate, compared to the model with single end-point fluctuations.

We study evolution equations describing jet propagation through quark-gluon plasma (QGP). In particular we investigate the contribution of momentum transfer during branching and find that such a contribution is sizeable. Furthermore, we study various approximations, such as the Gaussian approximation and the diffusive approximation to the jet-broadening term. We notice that in order to reproduce the BDIM equation (without the momentum transfer in the branching) the diffusive approximation requires a very large value of the jet-quenching parameter $$ \hat{q} $$ q ̂ .

We study, at a qualitative level, production of jet pairs in ultrarelativistic nuclear collisions. We propose a new framework for combining k T factorization and a formalism for in-medium propagation of jet particles that takes into account stochastic transverse forces as well as medium-induced radiation. This approach allows to address dijet observables accounting for exact kinematics of the initial state. Using our framework, we provide a description of R AA data and study azimuthal decorrelations of the produced dijets. In particular, we find that the resulting dijet observables feature behavior deviating from that of jet pairs which undergo transverse-momentum broadening following the Gaussian distribution. We interpret this behavior as a consequence of dynamics encoded in the Blaizot-Dominguez-Mehtar-Tani-Iancu equation.

Energy-loss studies of hard particle probes produced in heavy ion collisions have often been used to get information on the interactions within the medium of a quark-gluon plasma (QGP). However, with the study of inmedium energy-loss of individual particles alone, it remains still ambiguous, whether the occured decrease in particle energy is caused by predominantly radiative or collisional energy-loss mechanisms. Focusing on the in-medium energy-loss of hard jet-partons, we propose additional studies of the angular jet-structure as a means to further constrain the energy-loss mechanisms.

By the analysis of the world data base of elastic electron scattering on the proton and the neutron (for the latter, in fact, on 2 H and 3 He) important experimental insights have recently been gained into the flavor compositions of nucleon electromagnetic form factors. We report on testing the Graz Goldstone-bosonexchange relativistic constituent-quark model in comparison to the flavor contents in low-energy nucleons, as revealed from electron-scattering phenomenology. It is found that a satisfactory agreement is achieved between theory and experiment for momentum transfers up to Q 2 ∼ 4 GeV 2 , relying on three-quark configurations only. Analogous studies have been extended to the and the hyperon electromagnetic form factors. For them we here show only some sample results in comparison to data from lattice quantum chromodynamics.Evidently, electromagnetic (e.m.) form factors provide stringent tests on any model for hadrons. The Goldstoneboson-exchange (GBE) relativistic constituent-quark model (RCQM) for baryons constructed by the Graz group [1] had been tested with respect to covariant predictions for the elastic e.m. N form factors long ago [2,3]. An unprecedented overall agreement with experimental data up to momentum transfers of Q 2 ∼ 4 GeV 2 had then been achieved in a calculation along point-form relativistic quantum mechanics. After the appearance of phenomenological flavor analyses of elastic e.m. N form factors [4][5][6] it appeared more than interesting to check the performance of the GBE RCQM also in these respects. Recently we have performed such studies. Below we show pertinent results of selective quantities for the N and from extensions of this kind of investigations to the and to the hyperons with various u, d, and s quark contents.The theory and the calculations are exactly the same as explained for the point-form approach in our previous papers [2,3,7,8]. The predictions for the elastic e.m. form factors fulfill Poincaré invariance as well as time-reversal invariance and current conservation [7,8]. Accurate three-quark baryon wave functions were obtained solving a relativistically invariant mass operator along the stochastic variational method exploiting all possible symmetries in configuration, spin, and flavor spaces. For the rest frames they are depicted in Ref. [9] for singlet, octet and decuplet baryon states. In the calculation of the e.m. form factors the necessary Lorentz boosts can be executed rigorously when evaluating the matrix elements of the e.m. current operator in the framework of the point form.