# Presentation: 796335

## Multi-strange Baryon Correlations in p+p and d+Au Collisions at 

**Multi-strange Baryon Correlations**** ****in ****p+p**** ****and**** ****d+Au ****Collisions at**** **
**√****s****NN****  = 200 GeV**

*Hot Quarks ’04, Taos, New Mexico*

## Why Study Identified Correlations?

- STAR measured jet suppression, collective flow, RAA suppression.  Did it measure a QGP?

*A detailed study needed to understand the medium created at RHIC*

-   Difference in particle-antiparticle production mechanisms?
-   Difference with respect to strange-quark content?
-   What fraction of ’s are made in jets? A predominant mechanism in *p+p* and *d+Au*? Which *p**T* range?
-   Base line for a *Au+Au* study?

## The STAR Experiment

**S****olenoidal ****T****racker ****A****t ****R****HIC: **
**50 institutions from 14 countries – 500+ collaborators!**

***The STAR Experiment***

## 

****

- p+p

***       ******Procedure:***
- Apply loose cuts to find   and Anti-’s with *p**T** >2* GeV/c in a given event
- Find primary tracks with  *p**T**>1.5* GeV/c in the same event
- Make sure tracks are not  decay products
- Calculate  and plot it

***What we’re up against in p+p:***
-  *Mean multiplicity of a p+p event: 5.5 *
* **Raw ****’s and A-****’s per event: 3x10**-4*
*d+Au: higher multipl., better statistics...*

**y**

****

**High p****T**** track**

**x**

-  daughters
- a *p**-/+** *and a ***+/-*

-  bachelor, a ***±*

## p+p : Mean pT as a function of Multiplicity

- The mean pT appears to increase with multiplicity for for ’s and K0S
- (*See Mark Heinz’ talk today at 10:45*).
- Are ’s made in higher mult. events?  Does it mean ’s are made in jets?

***  ******Understanding the data***
*p+p : Mean p**T **as a function of Multiplicity*

*Mean ppMinBias event multiplicity*:
-  5.5 primary tracks/event

- Further study needed

##  Pythia numbers: 
3.2 x 107 events
4.2 x 105 (1.3% events) w/a -
1921 -’s w/pT>2 GeV/c (0.0016% events)
515 events with at least 1 track w/pT >1.5 GeV and a w/pT>2GeV/c
705 correlations (1.37 Corr/-);
|y| < 0.75

* **Pythia numbers:*
- 3.2 x 107 events
- 4.2 x 105 (1.3% events) w/a -
- 1921 -’s w/pT>2 GeV/c (0.0016% events)
- 515 events with at least 1 track w/pT >1.5 GeV and a w/pT>2GeV/c
- 705 correlations (1.37 Corr/-);
- |y| < 0.75

***p+p******: PYTHIA Simulation***

## p+p: Real Data Correlations (data: Y02 ppMinBias)

**Used both ******** and Anti-******** for the study **
**Used nHits cut to remove same-side split-track correlations, charged tracks are CTB-matched to remove pile-up**

- 13M events, ~770/13M = 0.0052% events with a high pT or
-  Not every one of 972 candidate events had a valid primary track

***p+p******: Real Data Correlations (data: Y02 ppMinBias)***

-   Correlation Candidates: 			972
-   Correlated: 	232 in 295 correlations (1.3 correlation per candidate)
-  Uncorrelated: 	740

##  pT distribution:

-  pT distribution:
-       at higher pT statistics start looking similar, however not enough to see a signal.  Need to go farther down in pT to gain stats
*40M events in Y05 run?*

***p+p: What’s Being Correlated?***

## No hope in p+p.  d+Au?

**No hope in p+p.  d+Au?**

*972 trigger particles*

## On to  d+Au...

*On to  d+Au...*

- dAu Challenges :
- underlying event shape,
- lots more background
- dAu Advantages:
- Lots more statistics
- background is manageable
- no thermalized medium expected, thus still a base line
- Omegas (not yet!..) ?
- All* trigger* *p**T* are above 2 GeV/c, all *associated* *p**T *are above 1.5 GeV/c

## d+Au Minimum Bias Y03

-      **11.6M dAu Minimum Bias  events considered (more data coming)**
**     ****6.2M passed all event cuts (triggerID and Z vtx <50 cm)**
**     ****2477 events with a ****************or************ candidate with p****T**** > 2 GeV**

***d+Au Minimum Bias Y03***

*0 tracks correlated: 1085 ev*

*1 track correlated: 772 ev*

**2+ tracks: 510 ev**

## d+Au   Correlations

***d+Au   Correlations***

***Height of the same-side peak is comparable to p+p ************-h******±****** same-side peak height: ~0.4 (************) vs. ~0.3 (************) (****See talk byYing Guo on Saturday****)***

- 1392 events with at least 1 correlation
- 2399 trigger particles
- 2358 Correlations
- 1.5  Corr/ !

## Conclusions and Outlook

*Good News*: There’s hope in *d+Au*!
- In *p+p *about 25% of observed ’s above 2GeV seem to be correlated
- Might get much more data in Y05...
*Not-so-good News*: Currently  not enough data for a thorough p+p study.
*Lots more to do!*
- Need better PYTHIA. Tuning?
- Need a thorough *d+Au* study:
- Add all available statistics
- Process the high pT-triggered dataset
- Measure and subtract the underlying soft physics correlations (momentum conservation)
- Need models: how many ’s come from  resonances?  How many should we expect from hard scattering?
- March on to *Au+Au*...

- The end. Thank you, thank you, thank you.

## d+Au   Correlations: 2 Gaussians fit (2/ndf : 1.031/3)

***d+Au   Correlations***: 2 Gaussians fit (2/ndf : 1.031/3)

***Height of the same-side peak is comparable to p+p ************-h******±****** same-side peak height: ~0.4 (************) vs. ~0.3 (************) (****See talk byYing Guo on Saturday****)***

- 1392 events with at least 1 correlation
- 2399 trigger particles
- 2358 Correlations
- 1.5  Corr/ !