Post on 03-Jan-2016
0(1530) in sNN=200 GeV
Au+Au Collisions in STARRichard Witt for the STAR collaboration
Motivation Data Set Analysis Technique Results Comparisons Conclusions
OutlineYale University
2 Richard Witt – for the STAR Collaboration
(Re)Scattering and (Re)Generation
Resonances continue to decay Lifetime < therm for some resonances
Losses due to daughter scattering Some generation possible Depends on hadronic
*
*
*
K
K*
*
p
K
p
Time oflast scatter~8-10 fm/c
= therm - chem
Non-resonanceratios fixed
F. Retiere and M. Lisa, PRC 70, 044907 (2004)
Expect:suppression of short-lived resonancesenhancement of long-lived resonances
STAR Collaboration PRL 97, (2006) 132301
3 Richard Witt – for the STAR Collaboration
Properties and Data Sets Spin 3/2 multi-strange
baryon resonance
Well established (4-star)
Two charge states
only 0(1530) here
0(1530) ⇒ - + +
Long-lived (c~21 fm) But...
Small production
4-particle final state
Feed-down to - (as much as 40% at 170 MeV)
Letessier and Rafelski, Hadrons and Quark Gluon Plasma, Cambridge, 2002, pg. 34
Provides another model constraint
Regeneration in Au+Au
What do we learn?
0 to 12%: 7.6 M events
10 to 40%: 5.4 M events
40 to 80%: 6.8 M events
Au+Au @ sNN = 200 GeV
4 Richard Witt – for the STAR Collaboration
Rotational Background Subtraction
“Narrow”rotation
Each - pT vector
rotate by 180˚
take small variations
about rotated vector
mix with all +
Each + pT vector
take small variations
about original direction
mix each with all -
Narrow Method (Au+Au)
- pT
180˚
+ all +…
+ pT
+ all -…
Automatically includes v2
minimizes flow distortions of background
5 Richard Witt – for the STAR Collaboration
Rotational Background Subtraction Background well
described
Visible signal before subtraction
S / (S+B) 8.6
Mass agrees with PDG
~60% wider (detector resolution)
STAR PreliminaryAu+Au @ sNN = 200 GeV
Breit-Wigner Fit2/ndf 336.8 / 268 1.531 +/- 0.001 0.015 +/- 0.002
STAR PreliminaryAu+Au @ sNN = 200 GeV
6 Richard Witt – for the STAR Collaboration
Transverse Momentum Spectra Measurements in 7 pT bins
out to ~5 GeV/c 3 centralities
Fit with mT-exponentials TmA=
dydp
Nd
pN TTTevt
/exp2
1 2
Mid-rapidity yields
scale ~linearly with Npart
same as STAR Collaboration arXiv:nucl-ex/0606014
7 Richard Witt – for the STAR Collaboration
STAR Preliminary
Mean Transverse Momentum
<pT> fits into systematics
p+p points
see arXiv:nucl-ex/0607033
Inverse Slope
flat with centrality
tracks with -
8 Richard Witt – for the STAR Collaboration
Resonance to Non-Resonance
Y. Kanada-En'yo and B. Muller, nucl-th/0608015
M. Kaskalov and E. Oset, PRC 73, (2006) 045123
Centrality */ Ratio
0-12% 0.92 ± 0.28
10-40% 0.60 ± 0.12
40-80% 0.51 ± 0.12
Implicationsignificant hadronic scattering
density of bath?large - cross-section?
Ratios (resonance to non)scaled to central pointshort-lived K* suppressed
re-scattering
*/ level
(re-) generation*/ suppressed
at creation?
L=2 decay?
*/ enhanced
9 Richard Witt – for the STAR Collaboration
Thermal Model
Parameter T B S Q S radius
Value 0.169 +/- 0.0060.04 +/- 0.01 0.016 +/- 0.009 -0.01 +/- 0.01 0.91 +/- 0.06 7.5 +/- 1.0
Thermal model (THERMUS)
ratios at chem
Resonance pattern
suppressed K*/K
level */
suppressed */
enhanced */
suggests significant hadronic scattering
10 Richard Witt – for the STAR Collaboration
Comparison with EPOS EPOS
arXiv:hep-ph/0603064
microscopic
partonic interactions
hadronization via string frag.
“Core”: high string density
“Corona”: low string density
Calculations
no normalization
some slope discrepancy
For even more * results, see poster 106 by Petr Chaloupka
11 Richard Witt – for the STAR Collaboration
STAR is the first experiment to have measured the 0(1530) transverse momentum spectra and mid-rapidity yields in heavy-ion collisions.
The mid-rapidity yields increase approximately linearly with Npart, <pT> falls within the current systematics.
The inverse slopes are approximately constant with centrality
Ratios indicate feed-down to - is significant
A stronger statement should be possible with statistics on disk and with the p+p point.
Pattern of resonance enhancement/suppression with respect to Thermal model calculations suggests significant hadronic scattering
A microscopic model, EPOS, also does well at describing the spectra and provides an alernative physics picture
Summary and Conclusions
(Thank You!)
12 Richard Witt – for the STAR Collaboration
Argonne National Laboratory• Institute of High Energy Physics, Beijing• Institute of Physics, Bhubaneswar• University of Birmingham• Brookhaven National Laboratory• California Institute of Technology• University of California, Berkeley• University of California, Davis• University of California, Los Angeles• Carnegie Mellon University• University of Illinois at Chicago• Creighton University• Nuclear Physics Inst., Academy of Sciences• Laboratory for High Energy (JINR), Dubna• Particle Physics Laboratory (JINR), Dubna• University of Frankfurt• Indiana University, Bloomington• Institut de Recherches Subatomiques, Strasbourg• Jammu University• Kent State University• Institute of Modern Physics, Lanzhou• Lawrence Berkeley Laboratory• Massachusetts Institute of Technology • Max-Planck-Instit fuer Physik, Munich• Michigan State University• Moscow Engineering Physics Institute• Indian Institute of Technology, Mumbai• City College of New York• NIKHEF and Utrecht University• Ohio State University• Panjab University• Pennsylvania State University• Institute of High Energy Physics, Protvino• Purdue University• Pusan National University• University of Rajasthan• Rice University• Universidade de Sao Paulo• University of Science and Technology of China (USTC)• Shanghai Institue of Nuclear Research (SINR)• SUBATECH, Nantes• Texas A & M• University of Texas, Austin• Tsinghua University• Valparaiso University• Variable Energy Cyclotron Centre, Kolkata• Warsaw University of Technology• University of Washington• Wayne State University• Institute of Particle Physics, Wuhan• Yale University• University of Zagreb
The STAR Collaboration
14 Richard Witt – for the STAR Collaboration
Where in Systematics? Where is the 0(1530)
what does it tell us?
Inline with current systematics?
Implications for Hadronic
15 Richard Witt – for the STAR Collaboration
Rotational Background Subtraction
Event 1: Au+Au - + + + X
Event 2: Au+Au - + + + X
…
2 Techniques
Event mixing
Rotation
2 variations
isotropic
narrow
pT
60˚ + all +
+ all +
+ all +
Isotropic Method (p+p)Narrow Method (Au+Au)
pT
180˚
+ all +…
+ pT
+ all -