HYDRO + JETS (HYDJET++) event generator for Pb+Pb collisions at LHC

The Monte Carlo event generator HYDJET++ is one of the few generators, designed for the calculations of heavy-ion collisions at ultrarelativistic energies, which combine treatment of soft hydro-like processes with the description of jets traversing the hot and dense partonic medium. The model is employed to study the azimuthal anisotropy phenomena, dihadron angular correlations and event-by-event (EbyE) fluctuations of the anisotropic flow in Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV. The interplay of soft and hard processes describes the violation of the mass hierarchy of meson and baryon elliptic and triangular flows at p_T > 2 GeV/c, the fall-off of the flow harmonics at intermediate transverse momenta, and the worsening of the number-of-constituent-quark (NCQ) scaling of elliptic/triangular flow at LHC compared to RHIC energies. The cross-talk of v_2 and v_3 leads to emergence of higher order harmonics in the model and to appearance of the ridge structure in dihadron angular correlations in a broad pseudorapidity range. HYDJET++ possesses also the dynamical EbyE fluctuations of the anisotropic flow. The model results agree well with the experimental data.Comment: 8 pages, 6 figures, contribution to Proceedings of the Winter Workshop on Nuclear Dynamics 201

Higher harmonics of azimuthal anisotropy in relativistic heavy ion collisions in HYDJET++ model

The LHC data on azimuthal anisotropy harmonics from PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted in the framework of the HYDJET++ model. The cross-talk of elliptic $v_2$ and triangular $v_3$ flow in the model generates both even and odd harmonics of higher order. Comparison with the experimental data shows that this mechanism is able to reproduce the $p_{\rm T}$ and centrality dependencies of quadrangular flow $v_4$, and also the basic trends for pentagonal $v_5$ and hexagonal $v_6$ flows.Comment: 12 pages including 13 figures as EPS-files; prepared using LaTeX package for publication in the European Physical Journal

Generation of higher flow harmonics in Pb+Pb collisions at LHC in HYDJET++ model

The influence of elliptic and triangular flow on higher flow harmonics is studied within the HYDJET++ model, which merges parametrized hydro with jet quenching. Even harmonics can be generated by elliptic flow only, while odd harmonics need nonzero triangular component. A hydrodynamical model predicts a scaling of υ4/υ22 ratio with pT, while jets force a rise of the high pT tail of the ratio. Hexagonal flow appears to be an interesting interplay between υ2 and υ3. It shows a dominant contribution of υ3 in central events and υ2 at more peripheral collisions. Comparison with ALICE, ATLAS and CMS experimental data is presented

Generation of higher flow harmonics in Pb+Pb collisions at LHC in HYDJET++ model

The influence of elliptic and triangular flow on higher flow harmonics is studied within the HYDJET++ model, which merges parametrized hydro with jet quenching. Even harmonics can be generated by elliptic flow only, while odd harmonics need nonzero triangular component. A hydrodynamical model predicts a scaling of υ4/υ22 ratio with pT, while jets force a rise of the high pT tail of the ratio. Hexagonal flow appears to be an interesting interplay between υ2 and υ3. It shows a dominant contribution of υ3 in central events and υ2 at more peripheral collisions. Comparison with ALICE, ATLAS and CMS experimental data is presented

Influence of jets and decays of resonances on the triangular flow in ultrarelativistic heavy-ion collisions

revised versionInternational audienceTriangular flow $v_3$ of identified and inclusive particles in Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV is studied as a function of centrality and transverse momentum within the \textsc{hydjet++} model. The model enables one to investigate the influence of both hard processes and final-state interactions on the harmonics of particle anisotropic flow. Decays of resonances are found to increase the magnitude of the $v_3(p_{\rm T})$ distributions at $p_{\rm T} \geq 2$ GeV/$c$ and shift their maxima to higher transverse momenta. The $p_{\rm T}$-integrated triangular flow, however, becomes slightly weakened for all centralities studied. The resonance decays also modify the spectra towards the number-of-constituent-quark scaling fulfillment for the triangular flow, whereas jets are the main source of the scaling violation at the energies available at the CERN Large Hadron Collider (LHC). Comparison with the corresponding spectra of elliptic flow reveals that resonance decays and jets act in a similar manner on both $v_3(p_{\rm T})$ and $v_2(p_{\rm T})$ behavior. Obtained results are also confronted with the experimental data on differential triangular flow of identified hadrons, ratio $v_3^{1/3}(p_{\rm T}) / v_2^{1/2}(p_{\rm T})$ and $p_{\rm T}$-integrated triangular flow of charged hadrons