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

13 Richard Witt – for the STAR Collaboration

Backups

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 -