Wojciech Broniowski

Correlations from hydrodynamic flow in pPb collisions

Abstract Two-particle correlations in relative rapidity and azimuth are studied for the pPb collisions at the LHC energy of s NN = 5.02 TeV in the framework of event-by-event ( 3 + 1 ) -dimensional viscous hydrodynamics. It is found that for the highest-multiplicity events the observed ridge structures appear in a natural way, suggesting that collective flow may be an important element in the evolution of the system. We also discuss the role of the charge balancing and the transverse-momentum conservation.

Size of the emission source and collectivity in ultra-relativistic p-Pb collisions

Abstract The interferometric radii in the system formed in ultra-relativistic proton–lead collisions are investigated in a framework based on event-by-event ( 3 + 1 )-dimensional viscous hydrodynamics. We argue that the most central p–Pb collisions undergoing collective expansion behave similarly to the peripheral nucleus–nucleus collisions. The interferometric observables can serve as signatures of the formation of an extended fireball.

Pion transition form factor in the Regge approach and incomplete vector-meson dominance

The concept of incomplete vector-meson dominance and Regge models is applied to the transition form factor of the pion. First, we argue that variants of the chiral quark model fulfilling the chiral anomaly may violate the Terazawa-West unitarity bounds, as these bounds are based on unverified assumptions for the real parts of the amplitudes, precluding a possible presence of polynomial terms. A direct consequence is that the transition form factor need not necessarily vanish at large values of the photon virtuality. Moreover, in the range of the BABAR experiment, the Terazawa-West bound is an order of magnitude above the data, thus is of formal rather than practical interest. Then we demonstrate how the experimental data may be properly explained with incomplete vector-meson dominance in a simple model with one state, as well as in more sophisticated Regge models. Generalizations of the simple Regge model along the lines of Dominguez result in a proper description of the data, where one may adjust the parameters in such a way that the Terazawa-West bound is satisfied or violated. We also impose the experimental constraint from the

Collective flow in ultrarelativistic

Z\ensuremath{\rightarrow}{\ensuremath{\pi}}_{0}\ensuremath{\gamma}

^3

decay. Finally, we point out that the photon momentum asymmetry parameter may noticeably influence the precision analysis.

He-Au collisions

a b s t r a c t The triangular flow in ultrarelativistic 3 He-Au collisions at RHIC energies is enhanced due to the triangu- lar arrangement of the nucleon configurations in 3 He. We study the fireball eccentricities in the Glauber Monte Carlo model and find that since the configurations of the projectile 3 He are elongated triangles, the created fireball has not only a significant triangularity but also a large ellipticity. The dependence of the triangularity on centrality is weak, so it cannot be extracted from the centrality dependence of the triangular flow v 3, as it is dominated by the centrality dependence of the hydrodynamic response. We propose to look at the centrality dependence of the ratio vn{4}/vn{2}, where the uncertainties from the hydrodynamic response cancel, and show that the basic signature of the geometry-driven collective flow is the rise of the ratio v 3{4}/v 3{2} with the number of participant nucleons for centralities less than 10%.

Hydrodynamic approach to p–Pb

Abstract The formation and collective expansion of the fireball formed in ultrarelativistic p–A and d–A collisions is discussed. Predictions of the hydrodynamic model are compared to recent experimental results. The presence of strong final state interaction effects in the small dense systems is consistent with the observed azimuthal anisotropy of the flow and with the mass dependence of the average transverse momentum and of the elliptic flow. This raises the question of the mechanism explaining such a rapid build-up of the collective flow and the large degree of local equilibration needed to justify this scenario.

Generalized parton distributions of the pion

Generalized Parton Distributions of the pion are evaluated in chiral quark models with the help of double distributions. As a result the polynomiality conditions are automatically satisfied. In addition, positivity constraints, proper normalization and support, sum rules, and soft pion theorems are fulfilled. We obtain explicit expressions holding at the low‐energy quark‐model scale, which exhibit no factorization in the t‐dependence. The crucial QCD evolution of the quark‐model distributions is carried out up to experimental or lattice scales. The obtained results for the Parton Distribution Function and the Parton Distribution Amplitude describe the available experimental and lattice data, confirming that the quark‐model scale is low, around 320 MeV.

Low Energy Nuclear Structure from Ultrarelativistic Heavy-Light Ion collisions

The search for specific signals in ultrarelativistic heavy-light ion collisions addressing intrinsic geometric features of nuclei may open a new window to low energy nuclear structure. We discuss specifically the phenomenon of α-clustering in 12C when colliding with 208Pb at almost the speed of light.

Hadron form factors and large-Nc phenomenology

The half width rule provides a way to consider 1/Nc corrections to hadronic models containing resonances. Consequences of such ideas for hadron form factors and Regge trajectories are explored, with special emphasis on the possibility to describe the spectrum of light and heavy unflavored vector mesons in a universal way.