Quest for omega mesons by their radiative decay mode in √s=200 GeV A+A collisions at RHIC-PHENIX
Mid-peripheral collisions : PLF* decay
description
Transcript of Mid-peripheral collisions : PLF* decay
Mid-peripheral collisions : PLF* decay
Statistical behavior isotropy vH > vL vL > vH
P
T TLF*
PLF*
1 fragment vL > vH
forwardvH > vL
backward
Sylvie Hudan, Indiana University
Experimental setup
Miniball/Miniwall
Beam
LASSA : Mass resolution up to Z=97 lab 58
114Cd + 92Mo at 50 A.MeV
Detection of charged particles in 4
Projectile48
Ring Counter :Si (300 m) – CsI(Tl) (2cm)2.1 lab 4.21 unit Z resolutionMass deduced†
† : Modified EPAX K. Sümmerer et al., Phys. Rev. C42, 2546 (1990)
Events with two fragments from a PLF*
ZH
ZL
ZHZL
PLF*
vL > vH, forward
vH > vL , backward
LH*PLF ZZZ )f(ZAA *PLFL*PLF HA
*PLF
LLHH*PLF
A
vAvAv
Anisotropy of PLF* decay6 NC 10
Different charge splits more asymmetric split for the backward case
Different alignments more alignment for the backward case
B. Davin et al., Phys. Rev. C65, 064614 (2002)
Different relative velocities higher vrel for the backward case
Asymmetry of the breakup :
Sensitivity to vPLF*
6 NC 10
vprojectile = 9.45 cm/ns
More asymmetric Z distribution for the backward case
Higher asymmetry at high vPLF* (low E*,J)
For all vPLF* , asymmetry for the backward case An other degree of freedom?
vL > vH vH > vLvPLF*
9.2
8.9
8.3
8.6
E*,J
x100
x20
x2
x80
x10
x1
B. Davin et al., Phys. Rev. C65, 064614 (2002)
To summarize…
The forward and backward cases are different :
Forward emission is consistent with standard statistical emission
Backward emission is consistent with dynamical decay
Different charge split dynamical has higher asymmetry
Different alignment dynamical is more aligned
Different relative velocity for the same ZL dynamical has higher vrel
Different Z distribution for a given (E*,J)
Well-defined PLF* : ZPLF* and vPLF*
Same correlation
expected if vPLF* and E* correlated
*PLF*PLF vvσ
More dissipation and fluctuations as ZPLF* decreases
For a given size, less dissipation for the dynamical case
vL > vH
vH > vL
dynamical
statistical
dynamical
Opening channels
Dynamical emission opens at higher vPLF* , i.e. lower E*
Up to 10% of the cross-section in the 2 fragment decay
vL > vH
vH > vL
1 fragment (x 0.1)
Asymmetry and Coulomb barrier
Higher asymmetry for the dynamical case
Coulomb barrier lower
Dynamical case appears at lower E*
35 ZPLF* 39
LH
LH
ZZ
ZZη
Energy in the fragments
More kinetic energy in the 2 fragments for the dynamical case
For a given vPLF*, difference of 20-30 MeV
A statistical picture : Viola systematics
Comparison statistical / Viola
At large vPLF*, statistical Viola
Deviation for low vPLF*
Temperature ?
7.3AA
ZZ*0.755Viola
1/32
1/31
21
Comparison dynamical / Viola
For all vPLF*, dynamical >>Viola
More compact shape needed for the dynamical case
Estimation of the temperature
T2CoulombTKE Measured Estimated
(Viola systematic)
Temperatures between 0 and 10-12 MeV
These temperatures are consistent with T=7 MeV from the isotopes in LASSA
(for 30 ZPLF* 46)
Statistical case : vL > vH
To summarize…
vPLF* as a good observable :
Same correlation (vPLF*)-vPLF* for statistical and dynamical cases
Dynamical case appears at higher vPLF* Coulomb barrier effect
vPLF* (TKE)dynamical > (TKE)statistical by 20-30 MeV
Statistical Viola at high vPLF* and deviation with increasing vPLF*
Temperature
Dynamical case always underestimated by Viola
A law : energy conservation
For a selected vPLF* E*
Kinetic energy in the fragments Higher for the dynamical case
Q value
Evaporated particles
+ +PLF*
E* , BEPLF*
ZH
TKEH , BEH
ZL
TKEL , BEL TKEevap , BEevap
nevaporatioQTKEE* fragments
“Missing” energy : Q value?
Same Q value in both cases for all vPLF*
(MeV
)
44Z35 *PLF
“Missing” energy : evaporation?
Multiplicity of Z=2 emitted forward to the PLF* (in LASSA)
Higher average multiplicities for the statistical case
Deviation of 10-20%
vL > vH
vH > vL
statistical
dynamical
Energy conservation : balance
vPLF* fixed
lstatisticadynamical
lstatisticadynamical
lstatisticadynamicalnevaporatio
Q
TKEE* fragments
Fixed
Suggests a longer time scale in the statistical case
for Z=2
A picture of the process
TKE
TimeSaddle-point Scission-point
Q
Coulomb
Collective
“Extra” energy
Initial kinetic energy?
Fluctuations of TKE(Q+Coulomb)-TKE correlation
TKE : width of the distribution
More fluctuations in the dynamical case
consistent with an additional kinetic energy at the scission-point
Conversion : Q + Coulomb to TKE
StatisticalTKE Q + Coulomb
DynamicalTKE Q + Coulomb + E0
Conclusions : building a coherent picture
We observed… We interpreted…
Correlation (vPLF*)-vPLF* vPLF* good selector for
E*Correlation vPLF* - Mevap
Different TKE for all vPLF* Initial TKE at scission
Different TKE for all vPLF* for the dynamical case is
Correlation TKE-(Q+Coulomb) larger than the statistical case
Multiplicities of evaporated Z=2scission,dynamical < scission,statistical
Collaboration
S. Hudan , B. Davin, R. Alfaro, R. T. de Souza, H. Xu, L. Beaulieu, Y. Larochelle, T. Lefort, V. Viola and R. Yanez
Department of Chemistry and Indiana University Cyclotron Facility, Indiana University, Bloomington, Indiana 47405
R. J. Charity and L. G. Sobotka
Department of Chemistry, Washington University, St. Louis, Missouri 63130
T. X. Liu, X. D. Liu, W. G. Lynch, R. Shomin, W. P. Tan, M. B. Tsang, A. Vander Molen, A. Wagner, H. F. Xi, and C. K. Gelbke
National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824