# Presentation: 400354

## Testing Models of Hadron Production with Strange Hadrons in the intermediate pT region using the STAR Detector.

Peter Jones
(University of Birmingham, UK)
for the STAR collaboration

 Physics Motivation
To understand hadron production at 2 < pT < 6 GeV/c.
Can quark coalescence account for all the features in the spectra?
2. What do the data tell us?
 and K0s production in p+p, Au+Au and d+Au at √s = 200 GeV.

**Testing Models of Hadron Production with Strange Hadrons in the intermediate p****T**** region using the STAR Detector.**
**Peter Jones**
- (University of Birmingham, UK)
- for the STAR collaboration
** ****Physics Motivation**
- To understand hadron production at 2 < *p*T < 6 GeV/c.
- Can quark coalescence account for all the features in the spectra?
**2. What do the data tell us?**
-  and K0s production in p+p, Au+Au and d+Au at √s = 200 GeV.

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## Quark coalescence / recombination

**Evidence of quark coalescence?**
- Particle dependence of elliptic flow.
- 	Constituent quark scaling.

**Is this a consistent picture?**
**Can it also explain ... **
- Anomalous B/M ratio?
- Particle dependence of hadron      suppression?
**This talk ...**
-  /K0S in pp and AuAu.
-  RCP of  and K0S in AuAu and dAu.

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## Measuring strangeness in STAR

-   p + 

- K0s + + 

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## K0s and  pT distributions

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## / K0s as a function of pT

**Observations**
- 1.	Ratio increases with centrality.
- 2.	Maximum at pT ~ 3 GeV/c.
- 3.	Ratio appears to converge for all centralities at pT >  6 GeV/c.
- 6.	Still in excess of ratio in pp data in this pT region.

- Note:  not corrected for / feedown. Approx 10% correction, independent of pT.

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## Baryon enhancement by coalescence

**Baryon enhancement by coalescence**

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## / K0s comparison with models

**Observations**
- 1. **Reco+Frag**
- 	magnitude:
- 	turnover:
- 	low pT:
- 2. **Soft+Hard Reco**
- 	magnitude:
- 	turnover:
- 	low pT:

- Greco et al.

- Fries et al.

- ( ****  =  no s+h component)

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## Nuclear modification factor, RCP

**Nuclear modification factor, R****CP**

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## d+Au Nuclear Modification h±

- STAR, PRL 91 (2003) 072304

**d+Au Nuclear Modification h****±**

- Cronin enhancement

- Jet-quenching

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

**Notes:**
Put reference for STAR data

## Nuclear modification in p+A collisions

**Cronin enhancement**
- Initial-state multiple scattering.

- pT (GeV/c)

- pT (GeV/c)

- Dominates at intermediate pT.

- Depends on “target” mass, A.
- Particle mass dependence?

**R(p+W)/(p+Be)**

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## Nuclear modification in p+A collisions

**Cronin enhancement**
- Initial-state multiple scattering.

- Decreases with √s.

- √s (GeV)

- √s (GeV)

- Decreasing trend for  and K.
- Trend not clear for proton.
**Extrapolation to √s = 200 GeV?**

- Dominates at intermediate pT.

- Depends on “target” mass, A.
- Particle mass dependence?

**R(p+W)/(p+Be)**

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## Similar B-M effect at intermediate pT?

- B-M difference is smaller than in Au+Au case.

**d+Au at 200 GeV**

**Note: R****CP**** ≠ R****dAu**

**STAR Preliminary**

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## Summary

**Enhancement in ********/K****0****s**** ratio increases with centrality.**
- Baryon excess is limited to 2 < pT < 5 GeV/c.
- Ratio exceeds p-p value out to 6 GeV/c.
- Recombination models are in qualitative agreement with the data.
- Model incorporating baryon junctions is also in agreement.

**AuAu Nuclear modification factor, R****CP****, shows B-M difference.**
- Consistent with quark recombination.
**d+Au Nuclear modification factor, also shows B-M difference.**
- Effect is smaller than in Au+Au collisions.
- Is this behaviour evidence of recombination?
- Preliminary PHENIX data appears to support B-M difference.
**Outlook**
- Results of 62 GeV Au-Au run expected soon.

- P. G. Jones, Hot Quarks, 19-24 July, 2004.

## Slide 14