Iu. Karpenko

EPOS LHC: Test of collective hadronization with data measured at the CERN Large Hadron Collider

EPOS is a Monte-Carlo event generator for minimum bias hadronic interactions, used for both heavy ion interactions and cosmic ray air shower simulations. Since the last public release in 2009, the LHC experiments have provided a number of very interesting data sets comprising minimum bias p-p, p-Pb and Pb-Pb interactions. We describe the changes required to the model to reproduce in detail the new data available from LHC and the consequences in the interpretation of these data. In particular we discuss the effect of the collective hadronization in p-p scattering. A different parametrization of flow has been introduced in the case of a small volume with high density of thermalized matter (core) reached in p-p compared to large volume produced in heavy ion collisions. Both parametrizations depend only on the geometry and the amount of secondary particles entering in the core and not on the beam mass or energy. The transition between the two flow regimes can be tested with p-Pb data. EPOS LHC is able to reproduce all minimum bias results for all particles with transverse momentum from pt = 0 to a few GeV/c.

Event-by-event simulation of the three-dimensional hydrodynamic evolution from flux tube initial conditions in ultrarelativistic heavy ion collisions

We present a sophisticated treatment of the hydrodynamic evolution of ultrarelativistic heavy ion collisions, based on the following features: initial conditions obtained from a flux tube approach, compatible with the string model and the color glass condensate picture; an event-by-event procedure, taking into the account the highly irregular space structure of single events, being experimentally visible via so-called ridge structures in two-particle correlations; the use of an efficient code for solving the hydrodynamic equations in 3 + 1 dimensions, including the conservation of baryon number, strangeness, and electric charge; the employment of a realistic equation of state, compatible with lattice gauge results; the use of a complete hadron resonance table, making our calculations compatible with the results from statistical models; and a hadronic cascade procedure after hadronization from the thermal matter at an early time.

Jets, bulk matter, and their interaction in heavy ion collisions at several TeV

We discuss a theoretical scheme that accounts for bulk matter, jets, and the interaction between the two. The aim is a complete description of particle production at all transverse momentum (

Uniform description of bulk observables in the hydrokinetic model ofA+Acollisions at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider

p_{t}

Estimation of the shear viscosity at finite net-baryon density from

) scales. In this picture, the hard initial scatterings result in mainly longitudinal flux tubes, with transversely moving pieces carrying the

A+A

p_{t}

collision data at

of the partons from hard scatterings. These flux tubes constitute eventually both bulk matter (which thermalizes and flows) and jets. We introduce a criterion based on parton energy loss to decide whether a given string segment contributes to the bulk or leaves the matter to end up as a jet of hadrons. Essentially low

\sqrt{s_\mathrm{NN}} = 7.7-200

p_{t}

GeV

segments from inside the volume will constitute the bulk, high

Evidence for hydrodynamic evolution in proton-proton scattering at 900 GeV

p_{t}