Multiplicity, average transverse momentum and azimuthal anisotropy in U+U collisions at s NN − − − − √ = 200 GeV using AMPT model
aa r X i v : . [ nu c l - e x ] M a r Multiplicity, average transverse momentum and azimuthal anisotropy in U+Ucollisions at √ s N N = 200 GeV using AMPT model Md. Rihan Haque , Zi-Wei Lin , and Bedangadas Mohanty Variable Energy Cyclotron Centre, Kolkata 700064, India and Department of Physics,East Carolina University, Greenville, NC 27858-4353, USA (Dated: October 1, 2018)Using a multi-phase transport (AMPT) model that includes the implementation of deformedUranium nuclei, we have studied the centrality dependence of the charged particle multiplicity( N ch , dN ch /dη ), average transverse momentum ( h p T i ), eccentricity ( ε ), triangularity ( ε ), theirfluctuations, elliptic flow ( v ) and triangular flow ( v ) for different configurations of U+U collisionsat midrapidity for √ s NN = 200 GeV. The calculations have been done for both the default and stringmelting versions of the AMPT model. The results are compared to the corresponding observationsfrom Au+Au collisions. We find that for the U+U collisions the dN ch /dη at midrapidity is enhancedby about 15-40% depending on the collision and model configuration chosen, compared to Au+Aucollisions. Within the several configurations studied, the tip-to-tip collisions leads to the largestvalues of N ch , transverse energy ( E T ) and h p T i . The h ε i and its fluctuation shows a rich centralitydependence, whereas not much variations are observed for h ε i and its fluctuations. The U+U side-on-side collision configuration provides maximum values of h ε i and minimum values of eccentricityfluctuations, whereas for peripheral collisions and mid-central collisions minimum values of h ε i andmaximum value of eccentricity fluctuations are observed for body-to-body configuration and thetip-to-tip configuration has minimum value of h ε i and maximum value of eccentricity fluctuationsfor central collisions. The calculated v closely correlates with the eccentricity in the model. Itis smallest for the body-to-body configuration in peripheral and mid-central collisions while it isminimum for tip-to-tip configuration in central collisions. For peripheral collisions the v in U+Ucan be about 40% larger than in Au+Au whereas for central collisions it can be a factor 2 higherdepending on the collision configuration. It is also observed that the v ( p T ) is higher for tip-to-tipand body-to-body configurations compared to other systems for the collision centrality studied. PACS numbers: 25.75.Ld
I. INTRODUCTION
In Au+Au collisions at the Relativistic Heavy IonCollider facility, large values of elliptic flow and largesuppression in high transverse momentum hadronproduction relative to the p + p collisions have beenreported [1]. The dominant interpretation of thesemeasurements have indicated that the relevant de-grees of freedom in these collisions are quarks andgluons. Deformed nuclei collisions such as U+U willallows us to investigate the initial conditions, hydro-dynamic behavior, path length dependence of par-tonic energy loss [2–4], possible local parity viola-tion [5] and other physics topics beyond what wehave learned from Au+Au collisions. The commis-sioning of the Electron Beam Ion Sources [6] willenable RHIC to collide Uranium ions. U+U colli-sions are being planned for 2012 with center of massenergy around 200 GeV [7].In contrast to central Au+Au collisions, becauseof the prolate shape of Uranium, there are config-urations (e.g body-to-body, defined later) in whichcentral U+U collisions are not spherical in the trans-verse plane, but has an elliptic shape. At RHIC wehave observed an increase in v / ε with increase intransverse particle density [1]. This corresponds tothe dilute regime predictions in kinetic theory [8]. For the hydrodynamic regime, one expects v / ε to saturate with increase in transverse particle den-sity [8]. One way to extend the transverse parti-cle density beyond what has been achieved at RHICis by performing U+U collisions or going to higherbeam energies as at LHC. Studies suggest that themaximum transverse particle density attended inU+U collisions could be about 6%-35% higher thanAu+Au collisions depending on the colliding con-figuration [2, 3, 9]. Furthermore, several possibleconfigurations of U+U collisions can occur, depend-ing on the angles of the two incoming Uranium nu-clei relative to the reaction plane. This will help inconstraining the initial condition models by the mea-surement of v , v and their fluctuations in U+U andcomparing the same to the corresponding results inAu+Au collisions. Galuber-based model simulationssuggest an increased value of h ε i (up to 30%) andeccentricity fluctuations in deformed U+U collisionsrelative to Au+Au collisions [4, 10].Furthermore it has been shown from the space-time evolution of high energy non-central symmetricheavy ion collisions using relativistic hydrodynamicsthat the matter expands preferentially in the impactparameter direction and the expanding shells leave ararefaction behind. As a consequence of early pres-sure gradient this could at freeze-out lead to threedistinct fireballs being produced. This was referredto as the nutcracker scenario [11]. Subsequently ithas been pointed out that such a phenomena is miss-ing for U+U collisions due to the time evolution ofthe initial transverse energy density profile within ahydrodynamical frame work [12].The energy loss of partons in a hot and dense col-ored QCD matter depends not only on the mediumdensity and color factor but also on the path lengthtraversed by the parton. Theories of energy lossfor fast partons support a non-linear dependenceof parton energy loss on the path-length, but thishas not yet been fully tested in experiment, due tothe small difference in path lengths for the partontraversing in-plane and out-of-plane for Au+Au col-lisions. Body-to-body U+U collisions are expectedto provide almost twice as much difference betweenthe in-plane and out-of-plane path lengths for thesame eccentricity as semi-peripheral Au+Au colli-sions. This in turn is expected to increase by 100%the absolute value of radiative energy loss and itsdifference between in-plane and out-of-plane direc-tions [2].Parity is conserved globally in the strong interac-tion, but local parity violation is possible because ofthe topological structure of QCD [13]. It has beenproposed that heavy-ion collisions at high energies,provide an unique opportunity to observe local par-ity violation [14]. The magnetic field required for theparity violating signal exists in non-central heavy-ion collisions and is produced due to the spectators.In central U+U body-to-body collisions, there areno spectators (small or zero magnetic field), whilein certain configurations the geometry of the colli-sion zone induces finite v . Background process tolocal parity violation are expected to be related to v , while the signal is expected to be related to themagnetic field strength [5]. One can then use a com-parative study of local parity violation observablesfor Au+Au and U+U collisions at similar energiesto interpretate the measurements [15].Most of the previous model based study of U+Ucollisions have made use of Monte Carlo Galubersimulation [4, 10] or it is coupled to a hydrodynamicevolution [2, 3]. Some investigations exists for select-ing special orientations of U+U collisions using eventgenerators [9]. In this work, we mainly focus on cen-trality dependence of dN ch /dη , h p T i , ε , ε , theirfluctuations, v and v for several configurations ofU+U collisions. The results are also compared tocorresponding observations in Au+Au collisions.The paper is organized as follows. In the next sec-tion we discuss the implementation of U+U collisionin the AMPT model [16]. We also discuss the spe-cific configurations of U+U collisions that we studyin this paper. Section III presents the results, whichincludes the N ch , dN ch /dη , E T and h p T i . This is fol- (b) (cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) (cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) YY XY (a) Side−Side
ZZZ X (b) Body−Body(c) Tip−Tip X (b)(b) (cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) FIG. 1: (Color online) Different configurations of U+Ucollisions studied in the present work. The Z-axis is thebeam direction. X( b ) represents that the impact param-eter direction is along the X-axis. For more details referto text and Table I. lowed by discussion on several geometrical variableslike ε , eccentricity fluctuations, ε and its fluctua-tions. Finally we present results on centrality andtransverse momentum dependence of v and v . Allresults are obtained using both the default and stringmelting versions of the AMPT model [16] and theU+U results are compared to corresponding resultsfrom Au+Au collisions. Finally in section IV wepresent a summary of our findings. II. IMPLEMENTING URANIUMCOLLISIONS IN AMPT
In the current work, U+U collision is implementedin the AMPT model as follows. The nucleon densitydistribution is parameterized as a deformed Woods-Saxon profile [17] ρ = ρ r − R ′ ] /a ) , (1) R ′ = R (cid:2) β Y ( θ ) + β Y ( θ ) (cid:3) , (2)where ρ is the normal nuclear density, R is the ra-dius of the nucleus and a denotes the surface dif-fuseness parameter. We have used R = 6 .
81 fm and a = 0 .
55 fm for
U nucleus. The Y ml ( θ ) denotesthe spherical harmonics and θ is the polar angle withthe symmetry axis of the nucleus. Deformation pa-rameters are β = 0 .
28 [2] and β = 0 .
093 [18] for
TABLE I: The details of the angular configuration ofU+U collisions used in this study. The subscript p and t denotes the projectile and target respectively. In thesimulations, for tip-to-tip configuration the θ is variedas 0 ± θ is varied as π /2 ± φ as 0 ± θ and φ are varied as π /2 ± π /2 ± θ p θ t φ p φ t Impact parametergeneral 0– π π π π randomtip-to-tip 0 0 0–2 π π minor axisbody-to-body π /2 π /2 0 0 major axisside-on-side π /2 π /2 π /2 π /2 minor axis Uranium. The presence of β modifies the shape ofUranium compared to that only with β [2, 9]. Theradius increases ∼
6% (3%) at θ = 0 ( θ = π/ ∼
3% around θ = π/ πr sin ( θ ) ρ ( r ) dθdφ ,where the absolute normalization of ρ ( r ) is irrele-vant. Both projectile and target U nuclei are ran-domly rotated along the polar and azimuthal direc-tions event-by-event with the probability distribu-tion sin Θ and uniform distribution for Θ and Φ,respectively. The sin Θ weight needs to be imple-mented to simulate unpolarized nucleus-nucleus col-lisions.In this work primarily three types of configura-tion of U+U collisions are studied and compared toU+U collisions without any specific choice of orien-tation and Au+Au collisions. These specific configu-rations will be termed as body-to-body, side-on-sideand tip-to-tip in the rest of the paper and are shownin Fig. 1. The details in terms of θ and φ angles ofthe orientation of the nuclei for these configurationsstudied in this paper are given in Table I.The AMPT model takes initial conditions fromHIJING [19]. However the mini-jet partons are madeto undergo scattering before they are allowed to frag-ment or recombine into hadrons. The string meltingversion of the AMPT model (labeled here as SM) isbased on the idea that for energy densities beyonda critical value of ∼ f m , it is difficult tovisualize the coexistence of strings (or hadrons) andpartons. Hence the need to melt the strings to par-tons. This is done by converting the mesons to aquark and anti-quark pair, baryons to three quarksetc. The scattering of the quarks are based on par-ton cascade ZPC [16]. Once the interactions stop,the partons then hadronizes through the mechanismof parton coalescence. The interactions between themini-jet partons in default AMPT model and thosebetween partons in the AMPT-SM model could giverise to substantial h v i . The parton-parton interac-tion cross section is taken as 10 mb. The results ch N ) c h P r obab ili t y P ( N -4 -3 -2 U+U bodyU+U tipU+U sideU+UAu+Au
AMPT-Default |<0.5 η | (a) (GeV) T E ) T P r obab ili t y P ( E -4 -3 -2 -1 U+U bodyU+U tipU+U sideU+UAu+Au
AMPT-Default |<0.5 η | (b) FIG. 2: (Color online) (a) Probability distribution of to-tal charged particle multiplicity ( N ch ) and (b) chargedparticle transverse energy ( E T ). Both results are atmidrapidity ( | η | < √ s NN = 200 GeV from default AMPT model.The different colored lines corresponds to different con-figurations of U+U collisions. Also shown for compari-son are the results from Au+Au collisions at √ s NN = 200GeV from default AMPT model as short dashed lines. presented below uses both the default and SM ver-sion of the AMPT model. III. RESULTSA. Multiplicity, transverse energy and averagetransverse momentum
Figure 2 shows default AMPT model simulatedminimum bias charged particle multiplicity ( N ch )and charged particle transverse energy ( E T ) distri-butions at midrapidity ( | η | < √ s NN = 200GeV. For comparison also shown in Fig. 2 are the re-sults from Au+Au (symmetric nuclei) collisions forthe same kinematic conditions. The shapes of thedistributions are very similar for different configu-rations of U+U collisions and those from Au+Aucollisions. However the maximum values of N ch and E T attained for U+U collisions in various configura-tions is found to be about 15%-35% higher than thecorresponding values from Au+Au collisions. The ch N ) c h P r obab ili t y P ( N -4 -3 -2 U+U bodyU+U tipU+U sideU+UAu+Au
AMPT-SM |<0.5 η | (a)
900 950 1000 1050 11000.10.20.30.4 -3 × (GeV) T E ) T P r obab ili t y P ( E -4 -3 -2 -1 U+U bodyU+U tipU+U sideU+UAu+Au
AMPT-SM |<0.5 η | (b)
460 480 500 520 540 56000.10.20.30.40.5 -3 × FIG. 3: (Color online) Same as Fig. 2 for AMPT stringmelting version. The inset shows the distributions forcentral collisions in an expanded scale. tip-to-tip configuration in U+U collisions allows toattain the maximum N ch and E T values among thevarious cases studied. The rest of the configurationsfor U+U seems to give similar values.Figure 3 shows the corresponding results using thestring melting version of the AMPT model. Theinset of the figure shows the distributions for cen-tral collisions in an expanded scale. In generalthe charged particle multiplicity is about 8% highercompared to the default case. However the trans-verse energy of charged particles at midrapidity isabout 10% lower for string melting case comparedto default version of AMPT. The rest of the trendsfor different configurations for U+U collisions rela-tive to each other and to the Au+Au collisions aresimilar in the both versions of the model.Figure 4(a) shows dN ch /dη for central collisions(impact parameter b < η , Fig. 4(b)( dN ch /dη ) / ( N part /
2) vs. N part and Fig. 4c chargedparticle average transverse momentum h p T i vs. N part for different collision configuration of U+U col-lisions and Au+Au collisions at √ s NN = 200 fromdefault AMPT model, where N part is the number ofparticipating nucleons. The shape of the dN ch /dη are similar for all collision configuration studied andin terms of multiplicity the conclusions are same asseen in Fig. 2(a). The ( dN ch /dη ) / ( N part /
2) at atmidrapidity ( | η | < η -10 -8 -6 -4 -2 0 2 4 6 8 10 η d ⁄ c h d N AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au (a) part N ) ⁄ > pa r t ( < N ⁄ ) η d ⁄ c h ( d N AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au
Au+Au(PHOBOS) |<0.5 η | (b) part N c ) ⁄ > ( G e V T < p AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au |<0.5 η | (c) FIG. 4: (Color online) (a) Charged particle pseudorapid-ity ( dN ch /dη ) distribution for central collisions (impactparameter = 3.65 fm) as a function of pseudorapidity ( η )for U+U collisions with different configurations of colli-sion and Au+Au collisions at √ s NN = 200 GeV usingdefault AMPT model. (b) dN ch /dη per participating nu-cleon ( N part ) pair versus N part at midrapidity ( | η | < . h p T i )of charged particles as a function of N part at midrapidity( | η | < .
5) for above collision configurations. higher N part values compared to Au+Au collisions.As expected it increases with increase in N part . Thecharged particle multiplicity in most central colli-sions studied shows a trend of body-to-body andside-on-side values being similar and lower than thevalues for tip-to-tip case with ( dN ch /dη ) / ( N part / η -10 -8 -6 -4 -2 0 2 4 6 8 10 η d ⁄ c h d N AMPT-SM
U+U bodyU+U tipU+U sideU+UAu+Au (a) part N ) ⁄ > pa r t ( < N ⁄ ) η d ⁄ c h ( d N AMPT-SM
U+U bodyU+U tipU+U sideU+UAu+Au
Au+Au(PHOBOS) |<0.5 η | (b) part N c ) ⁄ > ( G e V T < p AMPT-SM
U+U bodyU+U tipU+U sideU+UAu+Au |<0.5 η | (c) FIG. 5: (Color online) Same as Fig. 4 for AMPT stringmelting version. lisions are similar to those from the general U+Uconfiguration case for similar N part . The chargedparticle h p T i at midrapidity increases with increasein N part . For central collisions the h p T i for tip-to-tip is about 30 MeV higher than the body-to-bodycase with general U+U configuration h p T i values ly-ing in between. The increase in h p T i at midrapidity( | η | < .
5) for U+U tip-to-tip collisions relative toAu+Au collisions is small and is about 10 MeV.Figure 5 shows the same results as in Fig. 4 usingthe string melting version of the AMPT model. Theconclusions from dN ch /dη are similar as for the de-fault case, except that the dN ch /dη values are higherin the string melting version. The charged particle h p T i trends with respect to N part is however differ-ent. The h p T i values are lower for the string meltingversion compared to default case and it saturates or slightly decreases as one goes to central collisions.The saturation of h p T i values for central collisionsin the string melting version could be due to ad-ditional partonic interactions and the quark coales-cence process in the model relative to that for thedefault case. B. Geometrical variables
We have followed the notations for the participanteccentricity ( ε ) and triangularity ( ε ) as studied inRef [21]. The participant eccentricity is defined as: ε = q h r cos(2 φ part ) i + h r sin(2 φ part ) i h r i (3)where r and φ part are the polar coordinate positionsof participating nucleons in the AMPT model. Sim-ilar to the definition of the eccentricity the partici-pant triangularity, ε is defined as: ε = q h r cos(3 φ part ) i + h r sin(3 φ part ) i h r i (4)Figure 6 shows the h ε i and h ε i vs. N part forvarious configurations of U+U collisions at √ s NN = 200 GeV and Au+Au collisions at √ s NN = 200GeV from default AMPT model. For the same N part the U+U collisions without any specific selection ofcollision configuration have higher h ε i compared toAu+Au collisions. For U+U collisions the tip-to-tipconfiguration has a lower h ε i compared to no spe-cific selection of collision configuration. The side-on-side configuration have the largest values of h ε i for the systems studied. The h ε i for body-to-bodyconfiguration shows a specific trend as a function of N part , it is similar to side-on-side and tip-to-tip inmost peripheral collisions, then decreases sharply tovalues below those from tip-to-tip collisions for midcentral collisions which is followed by an increasein values of h ε i with N part to reach the same val-ues as side-on-side for the most central collisions.This clearly reflects the specific geometrical configu-ration traversed by the two Uranium nuclei in differ-ent cases. The h ε i however is found to be similar forall configurations in U+U studied and for Au+Aucollisions as a function of N part . Since these are spe-cific to geometrical configurations of the nuclei, weobserve no difference in these variable for the stringmelting version of the model.Next we study the fluctuation in ε and ε as it hasimportant consequences on understanding of the ini-tial conditions in heavy-ion collisions as well as flowfluctuations. The observables used are the ratio ofroot mean square (rms) value of ε to h ε i , rms of ε to h ε i and those suggested in Ref. [22]: h ε n i / h ε n i part N > ε < AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au (a) part N > ε < AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au (b)
FIG. 6: (Color online) (a) Participant eccentricity ( h ε i )and (b) triangularity ( h ε i ) as a function of number ofparticipating nucleons ( N part ) for various configurationsof U+U collisions and Au+Au collisions at √ s NN = 200GeV from default AMPT model. (for n = 2 , ε and ε asa function of N part for U+U and Au+Au collisionsat √ s NN = 200 GeV respectively. The fluctuationsin ε for U+U collisions with no specific selectionon collision configuration closely follows those forAu+Au collisions, however for the most central col-lisions the fluctuations are slightly smaller for U+Ucollisions. The fluctuations in ε for tip-to-tip con-figuration are comparable to those for Au+Au col-lisions. The fluctuations in ε for side-on-side con-figuration are the smallest among the configurationsstudied. On the other hand, those for body-to-bodyU+U collisions reflects an unique trend with fluctua-tions in ε being largest in mid-central collisions andthen decreasing with increase in centrality to reachthe corresponding values of side-on-side for centralmost collisions. Exactly similar trends are observedusing the variable h ε n i / h ε n i as a function of frac-tion of collision centrality (Fig. 7 (c) and (d)). Inthe Figs. 7 (c) and (d) the x-axis value near 0 meansmost-peripheral and the value near 1 means most-central collisions. The centrality is determined from part N > ε < ⁄ ) ε r m s ( AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au (a) part N > ε < ⁄ ) ε r m s ( AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au (b)
Centrality > ε < ⁄ > ε < AMPT-Default
U+U bodyU+U tipU+U sideAu+AuPb+Pb (2.76 TeV)U+U (c)
Centrality > ε < ⁄ > ε < AMPT-Default
U+U bodyU+U tipU+U sideAu+AuPb+Pb (2.76 TeV)U+U (d)
FIG. 7: (Color online) (a) Ratio of root mean square(rms) value of ε to h ε i and (b) rms of ε to h ε i vs. N part for various configurations of U+U collisions andAu+Au collisions at √ s NN = 200 GeV using defaultAMPT model. (c) and (d) h ε n i / h ε n i , with n = 2 ,
3, ver-sus fraction of collision centrality for U+U and Au+Aucollisions at √ s NN = 200 GeV using the default AMPTmodel. The Pb+Pb results corresponds to Glaubermodel simulations from Ref. [22] at √ s NN = 2.76 TeV. part N > < v AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au |<0.5 η | (a) part N > < v AMPT-Default
U+U bodyU+U tipU+U sideU+UAu+Au |<0.5 η | (b) FIG. 8: (Color online) (a) Average elliptic flow ( h v i )and (b) triangular flow ( h v i ) versus N part for differentcollision configuration of U+U and Au+Au collisions atmidrapidity for √ s NN = 200 GeV from default AMPTmodel. In (b) the h v i values close to zero are thosecorresponding to h v i calculated using ψ . the impact parameter distribution. The fluctuationin ε are observed to be independent of the collisionconfiguration in U+U and similar to Au+Au colli-sions, except perhaps for the central most collisions.For comparison results from a Glauber model sim-ulation for Pb+Pb collisions at √ s NN = 2.76 TeVfrom Ref. [22] are also shown. Our study shows thatif different U+U configurations can be selected inexperimental data, it would lead to interesting vari-ations of flow and flow fluctuations as a function ofcollision centrality, thereby providing a way to un-derstand initial conditions in heavy-ion collisions athigh energies. C. Elliptic and Triangular flow
The elliptic flow v which is the second Fouriercoefficient of particle distribution with respect to ψ is given as v = h cos(2( φ − ψ )) i (5) part N > < v AMPT-SM
U+U bodyU+U tipU+U sideU+UAu+Au |<0.5 η | (a) part N > < v AMPT-SM
U+U bodyU+U tipU+U sideU+UAu+Au |<0.5 η | (b) FIG. 9: (Color online) Same as Fig. 8 for AMPT stringmelting version. where ψ is the minor axis of the ellipse defined as ψ = atan2 (cid:0)(cid:10) r sin(2 φ part ) (cid:11) , (cid:10) r cos(2 φ part ) (cid:11)(cid:1) + π . (6)Similar to the definition of the elliptic flow and ψ , the triangular flow, v and ψ are defined as: v = h cos(3( φ − ψ )) i (7)where ψ is the minor axis of participant triangular-ity given by ψ = atan2 (cid:0)(cid:10) r sin(3 φ part ) (cid:11) , (cid:10) r cos(3 φ part ) (cid:11)(cid:1) + π . (8)Figure 8(a) and (b) shows the h v i and h v i as afunction of N part at midrapidity ( | η | < .
5) for dif-ferent configurations of U+U collisions and Au+Aucollisions at √ s NN = 200 GeV. The characteristictrend of centrality dependence (smaller values forcentral collisions and larger values for mid-centralcollisions) of h v i is observed for most of the config-urations studied except for U+U body-to-body col-lisions. In fact the body-to-body collisions showsa minimum h v i for mid-central collisions which isconsistent with the variation of h ε i with centrality c) ⁄ (GeV T p > < v AMPT-Default |<0.5 η | <120 part U+U bodyU+U tipU+U sideU+UAu+Au (a) c) ⁄ (GeV T p > < v AMPT-Default |<0.5 η | <120 part U+U bodyU+U tipU+U sideU+UAu+Au (b)
FIG. 10: (Color online) (a) Elliptic flow ( v ) and (b) tri-angular flow ( v ) as a function of transverse momentum( p T ) at midrapidity for 80 < N part <
120 U+U colli-sions for different configurations and Au+Au collisionsat √ s NN = 200 GeV from default AMPT model. as shown in Fig. 7(a). Figure 8(b) shows the cor-responding results for v . It is found v is slightlyhigher for Au+Au collisions compared to U+U colli-sions without any choice of configuration. For U+Ucollisions with various configurations the largest v seems to be from body-to-body condition, whilethose for side-on-side are smaller. Also shown in8(b) are the h v i values (close to zero) when calcu-lated using ψ instead of ψ . The h v i value of zeroshows that the minor axis of triangularity is foundto be uncorrelated with the reaction plane angle forboth U+U and Au+Au collisions. The correspond-ing results for the string melting version are shownin Fig. 9. The conclusions are same as for the de-fault case, except that the magnitude of the h v i and h v i are typically 40% and 80% higher respec-tively. Also for h v i the tip-to-tip configuration havethe largest values while those from Au+Au collisionshave smallest values.Figure 10 and 11 shows the transverse momen-tum ( p T ) dependence of v and v for different col-lision configuration of U+U and Au+Au collisionsat midrapidity ( | η | < .
5) at √ s NN = 200 GeV for c) ⁄ (GeV T p > < v AMPT-Default |<0.5 η | <200 part U+U bodyU+U tipU+U sideU+UAu+Au (a) c) ⁄ (GeV T p > < v AMPT-Default |<0.5 η | <200 part U+U bodyU+U tipU+U sideU+UAu+Au (b)
FIG. 11: (Color online) Same as Fig. 10 for 160 200 . for 80 < N part < 120 and for 160 < N part < v ( p T ) for U+U collisions with-out any specific collision configuration, tip-to-tipand Au+Au collisions have similar values for the p T range studied. The results for v ( p T ) from body-to-body U+U collisions are smaller and those for side-on-side configuration in U+U collisions are highercompared to Au+Au collisions at similar p T values.The Fig. 10(b) shows the corresponding results for v . The general trend as observed for p T integrated v (shown in Fig. 8(b)) is also followed by v ( p T ).The v ( p T ) for Au+Au and U+U body-to-body con-figurations seems to be slightly higher compared tothose from U+U tip-to-tip and U+U with no specificconfiguration selected.Figure 12 and 13 shows the corresponding resultsas given in Fig 10 and 11 respectively, for the stringmelting version of the AMPT model. The generalconclusions are similar, except the magnitude of the v and v values are higher for string melting relativeto default case. Further one notices the difference inboth v ( p T ) and v ( p T ) for various collision configu-ration seems to have increased for string melting casecompared to default case. For the several configu-rations studied the v ( p T ) in default AMPT modelfor U+U collisions are mostly below the correspond- c) ⁄ (GeV T p > < v AMPT-SM |<0.5 η | <120 part U+U bodyU+U tipU+U sideU+UAu+Au (a) c) ⁄ (GeV T p > < v AMPT-SM |<0.5 η | <120 part U+U bodyU+U tipU+U sideU+UAu+Au (b) FIG. 12: (Color online) Same as Fig. 10 for AMPT stringmelting version. ing values from Au+Au collisions, while for stringmelting case the U+U collision v ( p T ) are mostlyhigher than the corresponding values from Au+Aucollisions. IV. SUMMARY In this study we have implemented the possibil-ity of studying high energy collisions with deformedUranium nuclei within the framework of AMPTmodel. Experimental U+U collisions at around √ s NN = 200 GeV is planned for the year 2012 atthe RHIC facility. The Uranium nuclei is imple-mented by using a deformed Woods-Saxon profileand the projectile and target Uranium nuclei arerandomly rotated along the polar and azimuthal di-rections event-by-event with the probability distri-bution sin Θ and uniform distribution for Θ and Φ,respectively. In the current work we have studiedthree specific configurations of U+U collisions for √ s NN = 200 GeV, based on the choice of the polar,azimuthal angles of the two nuclei and the impactparameter direction. The results from these colli-sions have been compared to U+U collisions withno specific choice of orientation and Au+Au colli- c) ⁄ (GeV T p > < v AMPT-SM |<0.5 η | <200 part U+U bodyU+U tipU+U sideU+UAu+Au (a) c) ⁄ (GeV T p > < v AMPT-SM |<0.5 η | <200 part U+U bodyU+U tipU+U sideU+UAu+Au (b) FIG. 13: (Color online) Same as Fig. 12 for 160 120 and 160 < N part < v whileU+U body-to-body configuration has the smallest v . For the other configurations, tip-to-tip, U+Uand Au+Au the values are similar. A more clearer p T dependence of v is observed in string meltingcase compared to default case. In the string melt-ing case, the v of tip-to-tip and body-to-body aresimilar and higher than U+U, U+U side-on-side andAu+Au collisions.The future scope of our study includes studyingthe effect of jet-quenching and jet-medium interac-tions via dihadron correlations for different config-urations of U+U collisions. Furthermore we planto use the AMPT model to study the most effectiveway to select various configuration in U+U collisionsin an experiment. Acknowledgments This work is supported by the DAE-BRNS projectgrant No. 2010/21/15-BRNS/2026. [1] I. Arsene et al., [BRAHMS Collaboration], Nucl.Phys. A , 1 (2005); B.B. Back et al., [PHO-BOS Collaboration], Nucl. Phys. A , 28 (2005);J. Adams et al., [STAR Collaboration], Nucl. Phys.A , 102 (2005); K. Adcox et al., [PHENIX Col-laboration], Nucl. Phys. A , 184 (2005).[2] U. Heniz and A. Kuhlman, Phys. Rev. Lett. ,132301 (2005); A. Kuhlman and U. Heniz, Phys.Rev. C , 037901 (2005).[3] T. Hirano, P. Huovinen and Y. Nara, Phys. Rev. C , 021902(R) (2011).[4] H. Masui, B. Mohanty and N. Xu, Phys. Lett. B , 440 (2009).[5] S. A. Voloshin, Phys. Rev. Lett. , 172301 (2010).[6] A. Pikin et al., JINST ,2716 (1999).[9] C. Nepali, G. Fai and D. Keane, Phys. Rev. C ,051902(R) (2007); Phys. Rev. C , 034911 (2006).[10] P. Filip, R. Lednicky, H. Masui and N. Xu, Phys.Rev. C , 054903 (2009).[11] D. Teaney and E. V. Shuryak, Phys. Rev. Lett. ,4951 (1999). [12] P. F. Kolb, J. Sollfrank and U. W. Heinz, Phys. Rev.C , 054909 (2000).[13] D. Kharzeev, R. D. Pisarski and M. H. G. Tytgat,Phys. Rev. Lett. , 512 (1998).[14] L. E. Finch, A. Chikanian, R. S. Longacre,J. Sandweiss and J. H. Thomas, Phys. Rev. C ,014908 (2002); S. A. Voloshin, Phys. Rev. C ,044901 (2000).[15] B. I. Abelev et al. [STAR Collaboration], Phys. Rev.Lett. , 251601 (2009).[16] Z. W. Lin and C. M. Ko, Phys. Rev. C 65 , 034904(2002); Z. W. Lin et al. , Phys. Rev. C 72 , 064901(2005).[17] K. Hagino, N. W. Lwin and M. Yamagami, Phys.Rev. C , 017310 (2006).[18] P. Moller, J. R. Nix, W. D. Myers and W. J. Swiate-cki, Atom. Data Nucl. Data Tabl. , 185 (1995).[19] X. N. Wang and M. Gyulassy, Phys. Rev. D 44, 3501(1991).[20] B. Alver et al. [PHOBOS Collaboration], Phys. Rev.C , 024913 (2011).[21] B. Alver, G. Roland, Phys. Rev. C81 , 054905(2010).[22] R. S. Bhalerao, M. Luzum, J. -Y. Ollitrault, Phys.Rev. C84