1 / 16

Determining the Special Orientations in Deformed 238 U + 238 U Collisions at CSR

Determining the Special Orientations in Deformed 238 U + 238 U Collisions at CSR. Kejun Wu 1 , Fei Xie 1 , Feng Liu 1 , Nu Xu 1,2 1) Institute of Particle Physics, Huazhong Normal University, China 2) Nuclear Science Division, LBNL, Berkeley, CA 94720, USA. Outline. Motivation

yetta-owen
Download Presentation

Determining the Special Orientations in Deformed 238 U + 238 U Collisions at CSR

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Determining the Special Orientations in Deformed 238U+238UCollisions at CSR Kejun Wu1, Fei Xie1, Feng Liu1, Nu Xu1,2 1) Institute of Particle Physics, Huazhong Normal University, China 2) Nuclear Science Division, LBNL, Berkeley, CA 94720, USA Outline • Motivation • Results and discussions • Summary and Outlook --- Orientation Effect on High Density Matter --- Selecting those Events with High Density IWND2009, Shanghai, China, August 23~25

  2. Motivation : Why UU? Two most special geometry orientations Advantages and Suggestions: PRC 61,021903 (2002) PRC 61,034905 (2003) PRL 94,132301 (2005) PRC 72, 037901 (2005) PRC 73,034911 (2006) PRC 76, 051902(R) (2007) … tip-tip ( Two extreme collision condition ) ★Besides large atomic weight, Uranium is the most deformed stable nucleus. ★Longer duration for central tip-tip --- Higher local baryon density and easier thermalization ★Large initial eccentricity for central body-body ---Strong anisotropy flow IWND2009, Shanghai, China, August 23~25

  3. Motivation: QCD phase diagram ★ Emax =520MeV for U in CSR. ★ For tip-tip UU,medium has high temperature and density, partonic phase may be achieved. ★ CSR could make significant contribution in searching for the possible phase boundary. ★ Find a proper probe to study EoS and Chiral symmetry restoration. Cross-over CSR The Heavy Ion Research Facility in Lanzhou (HIRFL) - Cooler Storage Ring (CSR) IWND2009, Shanghai, China, August 23~25

  4. ART (a Relativistic Transport) Model The ART model was developed from the Boltzmann-Uehling-Uhlenbeck (BUU) model. BUU equation describes the time evolution of single particle in phase space. G.F.Bertsch and S.Das Gupta,Phys.Rep.160,189(1988). More baryon/meson resonances and their interactions are included. The maximum beam energy is 15 GeV/nucleon. • The particle-in-cell method of hydrodynamics • Divide the phase space into cells and set suitable test particles. • Evolving the test particle by Newton mechanics. • The initial condition the particle are distributed uniformly with a radius parameter of r0=1.12 fm. the momentum distribution is given by local Fermi gas approximation. • The collision integral is treated by dividing the ensemble of test particles into individual INC( intra-nuclear cascade) simulations. 1) B.A.Li and W.Bauer,Phys.Lett.B 254,335(1991);Phys.Rev.C 44,450(1991)。 2) B.A.Li and W.Bauer,and G.F.Bertsch,Phys.Rev.C 44,2095(1991)。 IWND2009, Shanghai, China, August 23~25

  5. Central Local Density UU vs. AuAu ( Full stopping for pp) b=0 fm ART 1.0, Energy and baryonic number conservation Tlab=500MeV Zhuang P.F, Nuclear Physics Review, Vol.19,No.3 Sep.,2002 • The maximal local baryon density can large than 3.2ρ0. • Longer duration in tip-tip UU than AuAu, even 2 times of body-body. • Baryon and energy density profile are similar. IWND2009, Shanghai, China, August 23~25

  6. Initial Geometry of Random Orientation θT,P:X-Z plane -π/2 ~π/2 φT,P :X-Y plane 0~2π tip-tip: θT =θP=0 ,φT φp random body-body: θT=θP= ±π/2, φT=φp±π • Non-polarized U random orientation • Ideal tip-tip and body-body events are quite unusual. • Our goal is to select central tip-tip like events. What are the tip-tip like events? How to get the tip-tip like events ? IWND2009, Shanghai, China, August 23~25

  7. Centrality Dependence on Baryon Density bmax=13fm for tip-tip bmax=19fm for body-body Define: is central cube with 1fm3 The most interesting events are tip-tip collision with b<2.6 fm , which might be selected by measuring distinctively the forward neutron multiplicity. S>70 IWND2009, Shanghai, China, August 23~25

  8. OrientationDependence on Baryon Density θ effect in central collisions Φ effect in central collisions • S is independent on φ when θ is fixed. ( Only for central events ) • θ <200 if s>70 IWND2009, Shanghai, China, August 23~25

  9. Open Questions • What are the central tip-tip like events? As a rough estimate, those events should be with b<2.6fm (central) and θT,P <20°(tip-tip like). • How to determine those events in the experiment? Firstly, find certain measurable (Nn or Nch)as online analysis to scale centrality and gain the sub-sample with small b . Secondly, find some special observables as offline analysis to select those events withsmall θT,P. IWND2009, Shanghai, China, August 23~25

  10. Determining the Central Events b<=2.6fm 4fm<b<=6fm 2.6fm<b<=4fm • Nn cut for online analysis is satisfying. • In order to further enhance those events, offline analysis is needed. IWND2009, Shanghai, China, August 23~25

  11. Nuclear Stopping Power In low energy region, H.Kruse et al.,PRC 31,1770(1985) When the ratio R is about 1, indicating that the hadronic system might reached thermal equilibrium. • R cut for offline analysis is satisfying. IWND2009, Shanghai, China, August 23~25

  12. The purity of tip-tip like Events Total 402K, b<2.6fm 20K,tip-tip like (all particles) TOF acceptance (charge particles with θ<80°) No PID (charge particles with θ<80°and regarded as nucleons) • The purity can be improved when R and Nn cut are used together. IWND2009, Shanghai, China, August 23~25

  13. Summary and Outlook • The events with extended high density phase (the central tip-tip like events) are with b<2.6fm and θT,P<20°. • Using the forward neutron multiplicity (e.g. Nn<=40) as online analysis in CSR experiment is recommended. This can hold the central events effectively. As an additional result, the body-body like events can be rejected effectively by cutting Nn. • Using nuclear stopping power (e.g. R/Rc/Rc*) as offline analysis can select effectively the central tip-tip like events. • We expect the available UU data can be analyzed. Thanks! IWND2009, Shanghai, China, August 23~25

  14. Basic models for heavy-ion collisions IWND2009, Shanghai, China, August 23~25

  15. X Long axis Z Y X Φ1 Long axis θ1 θ X θ2 Z Φ2 Rotation of colliding nuclei: Y Beam direction: Z T=RZ(Φ)*RY(θ) Rotation Matrics: Y IWND2009, Shanghai, China, August 23~25

  16. Y (2) (1) (4) θ1 Z θ1 (3) Y (2) Y (4) Φ angle (1) θ1 Z X θ1 (3) (1) tip-tip like collision Beam direction: Z (2)body-body like collision IWND2009, Shanghai, China, August 23~25

More Related