Multiplicity, average transverse momentum and azimuthal anisotropy in U+U at √s NN = 200 GeV using AMPT model Md. Rihan Haque 1 Zi-Wei Lin 2 Bedangadas Mohanty 1 1 Variable Energy Cyclotron Centre, Kolkata, and 2 Department of Physics, East Carolina University, Greenville, USA LBNL, May 14 th -18 th, 2012

Motivation 2  U+U collisions was planned for 2012 at RHIC with center of mass energy around 200 GeV and now running with CM energy = 193 GeV.  Higher transverse particle density can be achieved in U+U collisions than Au+Au at same beam energy.  Central U+U collisions are not spherical in the transverse plane, but has an elliptic shape.  Body-to-body U+U collisions are expected to provide almost twice as much difference between the in-plane and out-of-plane path lengths compared to Au+Au collisions.

Configurations with Deformed U+U 3 YYY X(b) Tip-Tip Side-SideBody-Body Impact parameter lies along X-axis Beam axis (Z) is perpendicular to this plane Go to slide# 10, 21(back up)

Two modes of AMPT: 4 AMPT Default ModeAMPT String Melting Mode Ref: Physical Review C 72, (2005)

Modification for deformed Uranium: 5 The nucleon density distribution is parameterized as a deformed Woods- Saxon profile, i.e., Where ρ 0 is the normal nuclear density, ‘R’ is the radius of the nucleus and ‘a’ denotes the surface diffuseness parameter. We have used R = fm and a = fm for 238 U nucleus. The denotes the spherical harmonics and θ is the polar angle with the symmetry axis of the nucleus. Deformation parameters are β 2 = 0.28 [ Ref: PRL. 94, (2005) ] and β 4 = [ Ref: Atom. Data Nucl. Data Tabl. 59, 185 (1995) ]

Results: N charge distribution 6 The shapes of the distributions are very similar for different configurations of U+U and Au+Au collisions. However the maximum values of N ch attained for U+U tip- to-tip configuration among various configurations dN cn /dη slide# 23

E T distribution: 7 The shapes of the distributions are very similar for different configurations of U+U and Au+Au collisions. However the maximum values of E T attained for U+U tip- to-tip collisions in among various configurations

Participant distribution in AMPT: 8  The participant distribution fluctuates for same impact parameter and same system. Au+Au

Formulations: 9  The participant eccentricity ε 2 is defined as:  and participant triangularity ε 3 is defined as:  the angle of the minor axis of the participant eccentricity is defined as:  the angle of the minor axis of participant triangularity is defined as: Ref: Phys. Rev. C 81, (2010)

Results: ε 2 and ε 3 distribution 10  For the same N part, the U+U collisions without any specific selection of collision configuration have higher compared to Au+Au collisions.  The side-on-side configuration have the largest values of for the systems studied.  The variation of is similar systems and configurations studied. Came here from slide# 15 ??

(I) Fluctuation in ε 2 and ε 3 : 11  Fluctuations in for U+U, with no specific choice, closely follows those for Au+Au collisions.  Fluctuations in for tip-to-tip configuration are comparable to those for Au+Au collisions.  Fluctuations in for side-on-side configuration are the smallest among the configurations studied.  Fluctuations in for body-to-body U+U collisions reflects an unique trend.  The fluctuations in for U+U and Au+Au collisions reflect similar nature.

(II) Fluctuation in ε 2 and ε 3 : 12  Similar trends are observed using the variable (where n=1,2) as a function of fraction of collision centrality.  The fluctuation in are observed to be independent of the collision configuration in U+U and similar to Au+Au collisions, except perhaps for the central most collisions. Ref: Phys. Rev. C 84, (2011) x-axis: 0 means the most-peripheral collisions 1 means the most-central collisions. The centrality is determined from the impact parameter distribution.

(dN ch /dη)/(N part /2) vs N part : 13  The shape of the dN ch /dη are similar for all collision configuration studied.  The (dN ch /dη)/(N part /2) at at midrapidity (|η| < 0.5) in U+U collisions extends to higher Npart values compared to Au+Au collisions.  The Au+Au collision values for central collisions are similar to those from the general U+U configuration case for similar Npart. Au+Au DATA Ref: Phys. Rev. C 83,

p T vs N part distribution: 14  Charged particle p T at midrapidity increases with increase in N part.  For central collisions the p T for tip-to- tip is about 30 MeV higher than the body-to-body case.  p T values for general U+U configuration lies in between tip-to- tip and body-to-body.  For AMPT String Melting case, p T saturates with increase in N part.

Results: V 2, V 3 vs N part 15  The characteristic trend of centrality dependence of is observed for most of the configurations studied except for U+U body-to-body collisions.  is smaller for central collisions and larger for mid-central collisions.  body-to-body collisions shows a minimum for mid-central collisions which is consistent with the variation of with centrality.  Not much difference in is observed which is consistent with the distribution with centrality. ε 3 Distribution in slide# 10

v 2, v 3 vs p T distribution: 16  The for U+U collisions, without any specific collision configuration, tip-to-tip and Au+Au collisions have similar values for the p T range studied.  The results for from body-to-body U+U collisions are smaller and those for side-on-side configuration has highest value for all p T range.  values in U+U collisions are lower compared to Au+Au for AMPT Default. ε 3 Distribution in slide# 10

v 2, (v 3 ) vs p T distribution: 17 Similar conclusions for String Melting results…

Summary and conclusion: 18 The charged particle multiplicity and charged particle transverse energy is found to be about 15%–35% higher for the different U+U configurations relative to Au+Au collisions. For string melting version the multiplicities are higher by about 8% for U+U collisions compared to default model, whereas for the transverse energy they are lower by about 10% compared to default. The average transverse momentum for charged particles increases with number of participating nucleons for the default case, whereas they saturate for central collisions in case of the string melting version. Within the different configurations studied, the multiplicity, transverse energy and average transverse momentum at mid-rapidity are largest for the tip-to-tip configuration. For peripheral collisions, v 2 in U + U can be about 40% larger than in Au + Au, whereas for central collisions, it can be a factor of 2 higher depending on the collision configuration. In SM version of AMPT, the magnitude of v 2 and v 3 for U+U configurations are typically 40% and 80% higher than corresponding Default version. This observation may be used in future to select events of particular configuration for U+U collisions.

Future motivation: Study flow properties in U+U collisions (Run 12) and compare with simulation results 2. … Reference for this ppt: PhysRevC

Thank You… 20

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Back up The charged particle multiplicity is about 8% higher compared to the default case. However, the transverse energy of charged particles at midrapidity is about 10% lower for the string-melting case compared to the default version of the AMPT. (fig-3 paper) 2. For central collisions, pT for the tip-to-tip case is about 30 MeV higher than for the body-to-body case, with the general U + U configuration pT values lying in between. pT at midrapidity (|η| < 0.5) for U + U tip-to-tip collisions relative to Au + Au collisions is small and is about 10 MeV. 3. The saturation of pT values for central collisions in the string-melting version could be due to additional partonic interactions and the quark coalescence process in the model relative to that for the default case. 4.In SM version the magnitude of v2 and v3 for U+U are typically 40% and 80% higher than Deft

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