# Presentation: 535360

## Slide 1

## Outline

- Motivation
- Interesting phenomena at intermediate pT
- Baryon/meson differences
- Method
- Comparisons of systems and energy
- Comparisons of unidentified to strange
- Conclusions

## Motivation – Jet and Ridge

- Long-range pseudorapidity (Δη) correlations observed by STAR in Au+Au at intermediate pT
- Near side jet peak sits on plateau (*Ridge*)‏
- Significant contribution to the near-side yield in central Au+Au
*Jet *harder than *Ridge*; *Ridge *closer to bulk

- J. Putschke (STAR),J.Phys.G34:S679-684,2007

## Ridge production mechanisms

**Radiated gluons, broadened by**
- Longitudinal flow, Armesto et al, PRL 93 (2004)
- QCD magnetic fields, Majumder et al,Phys.Rev.Lett.99:042301,2007
- Anisotropic plasma, P. Romatschke, PRC,75014901 (2007)
**Momentum-kick model**C.-Y. Wong , Phys.Rev.C76:054908,2007
**Medium heating + recombination**Chiu & Hwa, PRC72, 034903** **
**Radial flow + trigger ****	****bias **S. Voloshin, nucl-th/0312065, Nucl. Phys. A749, 287E. Shuryak,* **Phys.Rev.C76:047901,2007*

*E. Shuryak*

## Method: Yield extraction

*Ridge* previously observed to be independent of Δη in Au+Au
- Yield = number of associated particles/trigger particle
- To determine relative contributions, find yields for near-side, take ΔΦprojections in
- -0.75<Δη<0.75** *****Jet *****+ *****Ridge***
- 0.75<|Δη|<1.75 ***Ridge***
*Jet * = (*Jet*+*Ridge*) – *Ridge**.75/1.0
*Ridge* = yield from -1.75<Δη<1.75 – *Jet *yield
- Flow contributions to jet cancel
- v2 independent of η for |η|<1
- Phys. Rev. C72, 051901(R) (2005), Phys. Rev. Lett. 94, 122303 (2005)‏

- J. Putschke (STAR), J.Phys.G34:S679-684,2007

## Slide 6

## Jet yield vs pTtrigger

- d+Au, Au+Au √sNN=200 GeV from J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Cu+Cu √sNN=200 GeV from C. Nattrass (STAR), SQM2007
- Data points at same pTtrigger offset for visibility

*Jet* yield rises with pTtrigger in h-h
- Central Au+Au and Cu+Cu jet yields comparable
**Similar trend for ****√****s****NN****=62 GeV**

## Near-side Yield vs Npart 

- Near-side Yield vs Npart

*Jet* yield
**√****s****NN****=**200 GeV:
- Nearly independent of Npart
- √ sNN=62 GeV
- Also nearly independent of Npart
- Yield/trigger smaller

- d+Au, Au+Au √sNN=200 GeV from J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Cu+Cu √sNN=200 GeV from C. Nattrass (STAR), SQM2007

- 3.0 GeV/c < pTtrigger 6.0 GeV/c; 1.5 GeV/c < pTassociated < pTtrigger

## pT-distribution of associated particles

- pT-distribution of associated particles

*200 GeV*
*Jet *spectra similar in Cu+Cu, Au+Au
- 62 GeV
- Au+Au and Cu+Cu *Jet* similar
- Softer than 200 GeV

- Fits assuming 1/pT dN/dpT = A pT exp(-pT/T)‏

- J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Nattrass (STAR), SQM2007

- √sNN=200 GeV	Au+Au 0-10% Cu+Cu: 0-54%
- √ sNN=62 GeV	Au+Au 0-80% Cu+Cu: 0-60%

- 3.0 GeV/c<pTtrigger<6.0 GeV/c

## Near-side Yield vs Npart 

- Near-side Yield vs Npart

*Ridge *yield
- 200 GeV
- No *Ridge* in d+Au
- Increases with Npart
- Cu+Cu consistent with Au+Au
- 62 GeV
- Also increases with Npart in √sNN = 62 GeV
- yield/trigger smaller

- Jet yields: 10% error added h triggers to account for track merging

- 3.0 GeV/c < pTtrigger 6.0 GeV/c; 1.5 GeV/c < pTassociated < pTtrigger

- d+Au, Au+Au √sNN=200 GeV from J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Cu+Cu √sNN=200 GeV from C. Nattrass (STAR), SQM2007

## Ridge/Jet Ratio

- Ridge/Jet ratio independent of energy, system

- 3.0 GeV/c < pTtrigger 6.0 GeV/c; 1.5 GeV/c < pTassociated < pTtrigger

- Au+Au √sNN=200 GeV from J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Cu+Cu √sNN=200 GeV from C. Nattrass (STAR), SQM2007

## Unidentified summary

## Slide 13

## Motivation

- Identified trigger particles
- Effect of leading particle mass, flavor
- Identified associated particles
- Probe *Jet* and *Ridge* composition

## Jet yield vs pTtrigger

- Au+Au √sNN = 200 GeV from J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Data points at same pTtrigger offset for visibility
- Jet yields: 10% error added to V0 and h triggers to account for track merging, 15% to  triggers

- No significant trigger type dependence
- Note: Additional systematic error due to loss of tracks at small Δη, Δφ not yet quantified

## Jet yield - 

- Near-side Yield vs Npart

*Jet* yield -
- No significant trigger type dependence

- Data points at same Npart offset for visibility
- Jet yields: 10% error added to V0 and h triggers to account for track merging, 15% to  triggers

- d+Au, Au+Au √sNN=200 GeV from J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Cu+Cu √sNN=200 GeV from C. Nattrass (STAR), SQM2007

## pT-distribution of associated particles

- No significant trigger type dependence

- J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Nattrass (STAR),SQM2007

- √sNN=200 GeV  Au+Au 0-10% Cu+Cu: 0-54%
- √sNN=62 GeV  Au+Au 0-80% Cu+Cu: 0-60%

- 3.0 GeV/c<pTtrigger<6.0 GeV/c

- Fits assuming 1/pT dN/dpT = A pT exp(-pT/T)‏

## Ridge yield -

- Near-side Yield vs Npart

- Data points at same Npart offset for visibility
- Jet yields: 10% error added to V0 and h triggers to account for track merging, 15% to  triggers
- v2 errors shown only for h-h. K0S-h error bars comparable to h-h.  -h and -h errors roughly 1.5 times as large as h-h.

*Ridge* yield -
- Large systematic errors
- No significant difference?  Depends on how correlated systematic errors (v2) are

- d+Au, Au+Au √sNN=200 GeV from J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Cu+Cu √sNN=200 GeV from C. Nattrass (STAR), SQM2007

## pT-distribution of associated particles

- No significant trigger type dependence
- Systematic errors under investigation
- Jet:
- loss of tracks at small Δη, Δφ
- Ridge subtraction
- Ridge:
- systematic error from v2

- J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Nattrass (STAR),SQM2007

- √sNN=200 GeV  Au+Au 0-10% Cu+Cu: 0-54%
- √sNN=62 GeV  Au+Au 0-80% Cu+Cu: 0-60%

- 3.0 GeV/c<pTtrigger<6.0 GeV/c

- Fits assuming 1/pT dN/dpT = A pT exp(-pT/T)‏

**Jet**

**Ridge**

## Ridge production mechanisms

**Radiated gluons, broadened by**
- Longitudinal flow, Armesto et al, PRL 93 (2004)
- QCD magnetic fields, Majumder et al,Phys.Rev.Lett.99:042301,2007
- Anisotropic plasma, P. Romatschke, PRC,75014901 (2007)
**Momentum-kick model**C.-Y. Wong , Phys.Rev.C76:054908,2007
**Medium heating + recombination**Chiu & Hwa, PRC72, 034903** **
**Radial flow + trigger ****	****bias **S. Voloshin, nucl-th/0312065, Nucl. Phys. A749, 287E. Shuryak,* **Phys.Rev.C76:047901,2007*

- Do particles in Ridge look like bulk?  Look at dependence on particle type

## pTtrigger of identified associated yield

*Jet: (***Λ**+**Λ)/2K0S ≈0.5 in both systems

- pTtrigger of identified associated yield

**Particle ratios in Jet similar to those in p+p**

**Identified associated**

## pT-distribution of associated particles

*(***Λ**+**Λ)/2K0S ≈0.5 Independent of pTassociated

- J. Bielcikova (STAR), J.Phys.G34:S929-930,2007
- Nattrass (STAR),SQM2007

- √sNN=200 GeV  Au+Au 0-10% Cu+Cu: 0-54%
- √sNN=62 GeV  Au+Au 0-80% Cu+Cu: 0-60%

- 3.0 GeV/c<pTtrigger<6.0 GeV/c

- Fits assuming 1/pT dN/dpT = A pT exp(-pT/T)‏

## pTtrigger of identified associated yield

- pTtrigger of identified associated yield

- Ridge: *(***Λ**+**Λ)/2K0S ≈ 1
- Note: systematic error due to v2 not shown

**Identified associated**

## pTtrigger of identified associated yield

- M. Lamont (STAR), J.Phys.G32:S105-S114,2006
- J. Bielcikova (STAR), v:0707.3100 [nucl-ex]

**Particle ratios in Jet similar to those in p+p**

**(********Λ+Λ)****/2K****0****S**

## Identified summary

**Identified trigger**

**No significant dependence on trigger particle?**

**Identified associated**

**Jet looks like p+p**
**Ridge looks more like bulk?**

## Energy dependence: 

- Energy dependence:
- Ridge present at √sNN=62 GeV
- Both *Jet* and *Ridge* yields smaller at √sNN=62 GeV than √sNN=200 GeV
*Ridge/Jet Ratio independent of collision energy*
- Identified trigger particles:
- No significant dependence on trigger type
- Identified associated particles:
- Jet *(***Λ**+**Λ)/2K0S similar to p+p
- Ridge *(***Λ**+**Λ)/2K0S similar to bulk?

## Outlook

- More Au+Au √sNN = 200 GeV from Year 7 – 4x statistics, EMC-triggered data
- Allow separation of *Jet* and *Ridge* components of  triggered correlations?

## STAR Collaboration

**Argonne National Laboratory - University of Birmingham - Brookhaven National Laboratory - California Institute of Technology - University of California, Davis - University of California - University of California, Los Angeles - Carnegie Mellon University - University of Illinois at Chicago - Creighton University - Nuclear Physics Institute Prague - Laboratory for High Energy (JINR) - Particle Physics Laboratory (JINR) - University of Frankfurt - Institute of Physics, Bhubaneswar  - Indian Institute of Technology, Mumbai - Indiana University, Bloomington - Institut de Recherches Subatomiques - University of Jammu - Kent State University - Institute of Modern Physics, Lanzhou - Lawrence Berkeley National Laboratory - Massachusetts Institute of Technology - Max-Planck-Institut fuer Physik - Michigan State University - Moscow Engineering Physics Institute - City College of New York - NIKHEF and Utrecht University - Ohio State University, Columbus - Panjab University - Pennsylvania State University - Institute of High Energy Physics, Protvino, Russia - Purdue University - Pusan National University, Pusan, Republic of Korea - University of Rajasthan, Jaipur - Rice University - Universidade de Sao Paulo - University of Science & Technology of China - Shanghai Institute of Applied Physics - SUBATECH, Nantes, France - Texas A&M University - University of Texas - Tsinghua University - Valparaiso University - Variable Energy Cyclotron Centre, Kolkata, India - Warsaw University of Technology - University of Washington - Wayne State University - Institute of Particle Physics, CCNU (HZNU), Wuhan - Yale University - University of Zagreb**

## STAR

## Ridge in other systems and energies

- Ridge also present at √sNN = 62 GeV
- Lower statistics
- Weaker signal
- Apply method as done for √sNN = 200 GeV