# Presentation: 904702

## Trigger - identified V0 correlations in Au+Au collisions at STAR

- Léon Gaillard
- University of Birmingham

- Léon Gaillard, University of Birmingham

## Outline

-  Jet Tomography
-  Same side features in Au+Au
-  V0 - triggered correlations
-  Analysis
-  Results
-  Outlook

- Léon Gaillard, University of Birmingham

## Jet Tomography

- Azimuthal correlations tell half the story...

- ~

- d+Au

- Léon Gaillard, University of Birmingham

## Same side features in Au+Au

- 

- 

- 

- 

- d+Au

- Au+Au
- 0-5%

*Eur. Phys. J. C ***38 **461

- see talk by Joern Putschke

- 3.0 < pT,trigger < 6.0 GeV/c
- 2.0 < pT,assoc < 3.0 GeV/c

- Léon Gaillard, University of Birmingham

## Meson-Baryon difference

- Ridge is seen when pT,assoc. < 3GeV/c
- Spectra - Thermal dominated
- Correlations - more sensitive to shower - thermal contributions
- Should the baryon-meson difference feature in correlations?

- Associated track selection

- Trigger track selection

*J. Phys. G *(2004)* ***30 **S963

*J. Phys. G (*2005)* ***31 **S399

- RCP

- Léon Gaillard, University of Birmingham

## Identified correlations

- What causes the ridge?
- Compare correlations involving baryons with anti-baryons and mesons
- neutral strange particles ( K0short)  are a good source of all three out to high-pT

- Léon Gaillard, University of Birmingham

## Ridge Analysis I

- - (ridge + v2)

- (jet + ridge + v2)

- = jet yield

- Unidentified charged tracks in Au+Au
- 3.0 < pT,trigger < 4.0 GeV/c	2.0 < pT,assoc < 3.0 GeV/c

- 

- 

- Léon Gaillard, University of Birmingham

## Bin counting results

- 0-5%

- 5-10%

- 10-40%

- 40-60%

- 60-80%

- K0s-Ch

- Jet yield constant with centrality...
- Little dependence seen on window
- separation between baryon and meson triggered yields?

**nPart**

- Léon Gaillard, University of Birmingham

## Bin counting results

- 0-5%

- 5-10%

- 10-40%

- 40-60%

- 60-80%

- K0s-Ch

- Baryon and meson triggered yields are consistent in online central triggered events (x5 stats)
- Some systematic effects still under investigation

*preliminary*

**nPart**

- Léon Gaillard, University of Birmingham

## Ridge Analysis II

- Analysis
- projection : Jet
- projection : Jet + Ridge + v2

- 

- Unidentified charged tracks in Au+Au
- 3.0 < pT,trigger < 4.0 GeV/c	2.0 < pT,assoc < 3.0 GeV/c

- Léon Gaillard, University of Birmingham

## Projection studies - K0Ch

- 0-5%
- (online)

- 5-40%

- 40-80%

- Léon Gaillard, University of Birmingham

## Projection studies - K0Ch

- 0-5%
- (online)

- 5-40%

- 40-80%

- Fit is poorly constrained
- Peak is too shallow/wide

*preliminary*

- Léon Gaillard, University of Birmingham

## Projection studies - (La+Lb)Ch

- 0-5%
- (online)

- 5-40%

- 40-80%

- Léon Gaillard, University of Birmingham

## Projection studies - (La+Lb)Ch

- 0-5%
- (online)

- 5-40%

- 40-80%

- Fit is poorly constrained
- Peak is too shallow/wide

- Léon Gaillard, University of Birmingham

## Projection studies - dPhi yields

- jet + ridge yield ( fit)

- 3.0 < pT,trigger < 6.0 GeV/c	2.0 < pT,assoc < 3.0 GeV/c

- dPhi jet plus ridge yield increasing with centrality
- dEta jet yield poorly defined

- Léon Gaillard, University of Birmingham

## summary

- Two particle correlations with V0 triggers
- Jet yield appears flat with centrality
- Jet + ridge projection increases with centrality
- Baryon and Meson triggers consistent within statistics

- Future work
- Investigate systematic differences between V0 triggers
- Extend range to 
- Identified **associated** V0s

- For more V0 correlations see Jana Bielcikova’s talk

- Léon Gaillard, University of Birmingham

## Backup

- Léon Gaillard, University of Birmingham

## Constituent Quark Scaling

- Low pT: < 2Gev/c
-  strong anisotropic flow exhibited
-  described by hydrodynamic models with infinitesimal mean free path
- Intermediate pT: 2 GeV/c < pT < 6 GeV/c
-  constituent quark scaling
-  quark coalescence

- anisotropic flow

- Léon Gaillard, University of Birmingham

## V2 correction

- We see a cos(2 modulation of background in AuAu due to anisotropy of collision system

- particles emerge preferentially in the reaction plane

**reaction plane**

- Léon Gaillard, University of Birmingham

## efficiency correction

- Mean pT of associated tracks

- Scale up histograms by reconstruction efficiency of associated tracks

- Léon Gaillard, University of Birmingham

## Acceptance correction

****

- Corrected correlation

- mixed event

- real correlation

*preliminary*

- 

- Limited acceptance of STAR TPC introduces pair-wise shape. Correction using event mixing - making pairs with tracks from different events

- Léon Gaillard, University of Birmingham

## Antimerging cut II

- Léon Gaillard, University of Birmingham

## dEta-dPhi ChCh d+Au

- Away side is spread out in pseudorapidity difference
- because the system is **not** viewed from the centre of
- momentum frame of the parton scatter

- 

- 

- 

- 

- 

- 

- 

- 

- 

- event 1

- event 2

- event 3

- +

- +

- {

- Léon Gaillard, University of Birmingham

## Jets in heavy Ion Collisions

- _x0008__x0008_prediction: huge radiative energy loss
- prediction: screening delays fragmentation

- Léon Gaillard, University of Birmingham

## Interpretation

*Eur. Phys. J. C ***38 **461

- What causes the ridge and jet broadening?
-  Radiated gluon contributes to ridge and broadening **Armestro Eur. Phys. J. C 38 461**
-  Coalescence of quarks from the medium  **Chiu & Hwa Phys. Rev. C72:034903,2005 **
-  Collective flow combined with jet-queching **Voloshin nucl-th/0312065**** **

- Léon Gaillard, University of Birmingham

## Ridge Properties

- pt,assoc. > 2 GeV

- preliminary

- preliminary

- absolute ridge yield
- = {(jet+ridge) - (jet)}

- relative ridge yield

-  ridge yield

- Relative ridge yield decreasing with trigger pT
- Absolute ridge yield constant as function of trigger pT

- relative ridge yield
- = {(jet+ridge) - (jet)} / (jet)

- central

- peripheral

- transverse momentum of trigger

- transverse momentum of trigger

- Léon Gaillard, University of Birmingham

## Relativistic Heavy Ion Collider

**RHIC**

- BRAHMS

- PHOBOS

- PHENIX

- STAR

**AGS**

**TANDEMS**

**Long Island, NY**

- Time Projection Chamber

- Léon Gaillard, University of Birmingham

## Bin counting results

- Vary size of windows

*preliminary*

**nPart**

- Léon Gaillard, University of Birmingham

## Bin counting results

- K0short

- 0-5%

- 5-10%

- 10-40%

- 40-60%

- 60-80%

- 

- 
- 

- }

- Jet yield = yield() - yield()

- trigger V0

*preliminary*

**nPart**

- Léon Gaillard, University of Birmingham

## Bin counting results

- 0-5%

- 5-10%

- 10-40%

- 40-60%

- 60-80%

- K0s-Ch

- Baryon and meson triggered yields are consistent in online central triggered events (x5 stats)

*preliminary*

**nPart**

- Léon Gaillard, University of Birmingham

## Bin counting results

- K0short

- 0-5%

- 5-10%

- 10-40%

- 40-60%

- 60-80%

- 

- 
- 

- }

- Jet yield = yield() - yield()

- trigger V0

- Slight increase in most central yields
- Broad jet peak

*preliminary*

**nPart**

- Léon Gaillard, University of Birmingham

## Projection studies - dPhi yields

- jet + ridge yield ( fit)

- 3.0 < pT,trigger < 6.0 GeV/c	2.0 < pT,assoc < 3.0 GeV/c

- dPhi jet plus ridge yield increasing with centrality
- dEta jet yield poorly defined

- Compare to jet yield from bin counting

- Léon Gaillard, University of Birmingham