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Prithwish Tribedy

Publications and source records attributed to Prithwish Tribedy.

46 records · Page 3Linked to original sources
arXiv2012

QCD saturation at the LHC: comparisons of models to p+p and A+A data and predictions for p+Pb collisions

In a previous paper (arXiv:1011.1895), we showed that saturation models, constrained by e+p HERA data on inclusive and diffractive cross-sections, are in good agreement with p+p data at LHC in the soft sector. Particularly impressive was the agreement of saturation models with the multiplicity distribution as a function of $n_{\rm ch.}$. In this paper, we extend these studies further and consider the agreement of these models with data on bulk distributions in A+A collisions. We compare our results to data on central and forward particle production in d+Au collisions at RHIC and make predictions for inclusive distributions in p+Pb collisions at the LHC.

hep-ph↗
arXiv2012

Search for QCD Phase Transitions and the Critical Point utilizing Particle Ratio Fluctuations and Transverse Momentum Correlations from the STAR Experiment

Dynamical fluctuations of the globally conserved quantities in heavy ion collision such as baryon number, strangeness, charge, and isospin are suggested to carry information about the deconfinement and chiral phase transitions. The STAR experiment has performed a comprehensive study of the collision energy and charge dependence of dynamical particle ratio ($K/π$, $p/π$, and $K/p$) fluctuations, net-charge fluctuations, and transverse momentum correlations at mid-rapidity, as well as neutral-charge pion fluctuations at forward rapidity. The centrality, charge, and collision energy dependence from new measurements of the fluctuation observables $ν_{dyn}$ and $r_{m,1}$ and the energy dependence of transverse momentum correlations from $\sqrt{s_{NN}}$ = 7.7-200 GeV Au+Au collisions are presented. These results are also compared to predictions from hadronic models.

nucl-ex↗
arXiv2012

Initial state fluctuations and higher harmonic flow in heavy-ion collisions

A framework combining Yang-Mills dynamics of the pre-equilibrium glasma with relativistic viscous hydrodynamic evolution of the quark-gluon plasma and hadron gas phases is presented. Event-by-event fluctuations of nucleon positions and color charges are taken into account, leading to negative binomial fluctuations of gluon multiplicities. Experimental anisotropic flow coefficients v2-v5 of charged hadron distributions in heavy-ion collisions at the Large Hadron Collider are well described. Furthermore, event-by-event distributions of v2, v3 and v4 measured by the ATLAS collaboration are reproduced.

hep-ph↗
arXiv2012

Event-by-event anisotropic flow in heavy-ion collisions from combined Yang-Mills and viscous fluid dynamics

Anisotropic flow coefficients v_1-v_5 in heavy ion collisions are computed by combining a classical Yang-Mills description of the early time glasma flow with the subsequent relativistic viscous hydrodynamic evolution of matter through the quark-gluon plasma and hadron gas phases. The glasma dynamics, as realized in the IP-Glasma model, takes into account event-by-event geometric fluctuations in nucleon positions and intrinsic sub-nucleon scale color charge fluctuations; the pre-equilibrium flow of matter is then matched to the MUSIC algorithm describing viscous hydrodynamic flow and particle production at freeze-out. The IP-Glasma+MUSIC model describes well both transverse momentum dependent and integrated v_n data measured at the Large Hadron Collider (LHC) and the Relativistic Heavy Ion Collider (RHIC). The model also reproduces the event-by-event distributions of v_2, v_3 and v_4 measured by the ATLAS collaboration. The implications of our results for better understanding of the dynamics of the glasma as well as for the extraction of transport properties of the quark-gluon plasma are outlined.

nucl-th↗
arXiv2012

Event-by-event gluon multiplicity, energy density and eccentricities at RHIC and LHC

The event-by-event multiplicity distribution, the energy densities and energy density weighted eccentricity moments epsilon_n (up to n=6) at early times in heavy-ion collisions at both RHIC (root-s=200 GeV) and LHC (root-s=2.76 TeV) are computed in the IP-Glasma model. This framework combines the impact parameter dependent saturation model (IP-Sat) for nucleon parton distributions (constrained by HERA deeply inelastic scattering data) with an event-by-event classical Yang-Mills description of early-time gluon fields in heavy-ion collisions. The model produces multiplicity distributions that are convolutions of negative binomial distributions without further assumptions or parameters. The eccentricity moments are compared to the MC-KLN model; a noteworthy feature is that fluctuation dominated odd moments are consistently larger than in the MC-KLN model.

hep-ph↗
arXiv2012

Fluctuating Glasma initial conditions and flow in heavy ion collisions

We compute initial conditions in heavy-ion collisions within the Color Glass Condensate (CGC) framework by combining the impact parameter dependent saturation model (IP-Sat) with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this IP-Glasma description includes quantum fluctuations of color charges on the length-scale determined by the inverse nuclear saturation scale Q_s. The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity is close to that in a model tuned to reproduce experimental flow data. We compare transverse momentum spectra and v_(2,3,4)(p_T) of pions from different models of initial conditions using relativistic viscous hydrodynamic evolution.

nucl-th↗
arXiv2011

Study of γ-charge correlation in heavy ion collisions, various approaches

Event-by-event γ-charge correlation is used in studying systems going through QCD chiral phase transition. In this paper various methods for measuring γ-charge correlation in heavy ion collisions have been discussed. Dynamical fluctuation due to formation of domains of DCC that can affect γ-charge correlation has been discussed. We study known detector and statistical effects involved in these measurements and suggest suitable robust observables Δν_{dyn} and r_{m,1} sensitive to small γ-charge correlation signal. These variables are constructed based on moments of multiplicity distributions of photon and charged particles. Estimations of expected measurable signals of γ-charge correlation from various available models such as for ideal Boltzmann gas of pions, monte-carlo models based on transport and mini-jets have been discussed. Collision centrality dependence of the observables have been estimated from Central Limit Theorem and found to be consistent with the model predictions. We find that observables show high sensitivity to fraction of DCC events and have nonlinear dependence on fraction of pions carrying DCC signals. Variation of r_{m,1} with orders of its higher moments m is an observable to extract the nature and strength of γ-charge correlation.

nucl-ex↗
arXiv2011

Saturation models of HERA DIS data and inclusive hadron distributions in p+p collisions at the LHC

Unintegrated gluon distributions sensitive to the transverse spatial distribution of gluons in the proton are extracted from data on exclusive and diffractive final states at HERA in the dipole approach. These unintegrated gluon distributions can be used to compute inclusive hadron production in p+p collisions at the LHC. In this paper, we consider a number of saturation models with differering dynamical assumptions that give good fits to the available HERA data. We apply these models to study the rapidity and transverse momentum dependence of the LHC data up to $\sqrt{s} = 7$ TeV. We examine the sensitivity of these results to parameters that are not constrained by the HERA data and comment on similarities and differences with previous work. We compute the n-particle inclusive multiplicity distribution and show that the LHC p+p results are in agreement with predictions for multi-particle production in the Color Glass Condensate approach. This result has significant ramifications for the interpretation of multi-particle correlations in high multiplicity events at the LHC.

hep-ph↗
arXiv2011

Inclusive hadron distributions in p+p collisions from saturation models of HERA DIS data

Dipole models based on various saturation scenarios provide reasonable fits to small-x DIS inclusive, diffractive and exclusive data from HERA. Proton un-integrated gluon distributions extracted from such fits are employed in a $k_\bot$-factorization framework to calculate inclusive gluon distributions at various energies. The n-particle multiplicity distribution predicted in the Glasma flux tube approach shows good agreement with data over a wide range of energies. Hadron inclusive transverse momentum distributions expressed in terms of the saturation scale demonstrate universal behavior over a wider kinematic range systematically with increasing center of mass energies.

hep-ph↗