# Presentation: 691859

## Experimental Results for Fluctuations And Correlations as a Signature of QCD Phase Transitions in Heavy Ion Collisions

- Gary Westfall
*Michigan State University, USA*

- Gary Westfall, Quark Matter 2008

## Correlations and Fluctuations

- Depend on previous talk for theoretical justification
- Look for discontinuities or changes in experimental results for correlations and fluctuations as a function of incident energy
*K*/*π* Fluctuations
- Balance Function
- Net Charge Fluctuations
- Multiplicity Fluctuations - several approaches
*p**t* Correlations
- RHIC Energy Scan
- SPS Program

- Gary Westfall, Quark Matter 2008

## K/π Fluctuations

- Gary Westfall, Quark Matter 2008

- NA49
- Preliminary

- See talk by Z. Ahammed
- in Session X

- See talk by M.
- Rybczynski, Session X

## K/π Fluctuations

*K*/*π* Fluctuations

- Gary Westfall, Quark Matter 2008

- See talk by Z. Ahammed
- in Session X

- Torrieri
- QM06

## K/π FluctuationsScaling with dN/dη

*K*/*π* FluctuationsScaling with *dN*/*dη*

- Gary Westfall, Quark Matter 2008

- See talk by Z. Ahammed
- in Session X

- Au+Au statistical errors
- Cu+Cu statistical+systematic errors

## Balance Function

- Charge fluctuations can be studied with several different variables that can be expressed in terms of each other
- We choose to illustrate charge fluctuations using the balance function

- Gary Westfall, Quark Matter 2008

- Bass, Danielewicz, Pratt PRL 85 2689  (2000)

## Balance Function

- Gary Westfall, Quark Matter 2008

- NA49
- Phys. Rev. **C** 76, 024914 2007

- Balance functions for
- Pb+Pb at sNN1⁄2 =
- 6.3 to 17.3 GeV

- Balance functions for
- Au+Au at sNN1⁄2 =
- 20 to 200 GeV

- Data

- Shuffled

- Au+Au 200 GeV

- STAR, QM 02, QM 04

## Balance Function

- Gary Westfall, Quark Matter 2008

- NA49

- NA49
- Phys. Rev. **C** 76, 024914 2007

- Large W means narrow balance function

## Net Charge Fluctuations at RHIC

- Gary Westfall, Quark Matter 2008

- See poster by M. Sharma

## Net Charge Fluctuations at RHIC

- Gary Westfall, Quark Matter 2008

- See poster by M. Sharma

- The slope in p+p, Cu+Cu and Au+Au depends on the correlation length: the shorter the correlation, the  larger the slope
- The distributions indicate that the correlation length is shorter for central collisions and for larger systems, in agreement with the observed reduction of
- the width of the balance function

## Net Charge Fluctuations at the SPS

- Gary Westfall, Quark Matter 2008

- NA49 PRC 70, 064903 (2004)

## Multiplicity Fluctuations at the SPS

- Gary Westfall, Quark Matter 2008

- NA49, 0712.321 [nucl-ex] 2007

- 1% most central
- Scaled to 4*π*

## Multiplicity Fluctuations at RHIC

- Gary Westfall, Quark Matter 2008

- PHENIX, PRC 76, 034903 (2007)

## Multiplicity Fluctuations at RHIC

- Gary Westfall, Quark Matter 2008

- PHENIX, PRC 76, 034903 (2007)
- See talk by K. Homma in Session X

## Forward/Backward Multiplicity Correlations

- Gary Westfall, Quark Matter 2008

- See talk by B. Srivistava Session XIX
- See poster 220 by T. Tarnowsky

## Energy Dependence of F/B Multiplicity Fluctuations

- Gary Westfall, Quark Matter 2008

- Central Au+Au 0 – 10%

- 200 GeV

- 62.4 GeV

- Long range correlations are an indicator of multiple elementary
- elastic collisions

- Long range correlations decreases as the incident energy is decreased

- STAR preliminary

- See talk by B. Srivistava Session XIX
- See poster 220 by T. Tarnowsky

## pt Fluctuations

*p**t* Fluctuations

- Gary Westfall, Quark Matter 2008

- Adamova et al., CERES
- Miskowiec for NA49, CPOD 2007

## pt Fluctuations

- Gary Westfall, Quark Matter 2008

- Adamova et al., CERES

- Calculate <*Δp**t,i**,Δp**t,j**> *for pairs within a given range of *Δ**φ* and multiply by *dN*/*dη*

- The region of 30° < *Δ**φ* < 60° is free from effect such as HBT and jets and may be a fruitful region to search for discontinuities as a function of incident energy

## RHIC Energy Scan

- Energies as low as sNN1/2 = 4.5 GeV (10 AGeV fixed target)

- Gary Westfall, Quark Matter 2008

| (GeV) | (MeV) | Min Bias BBC Rate
(Hz) | Days/
Mevents | Number
Of Events

 | Number of
beam days |
| --- | --- | --- | --- | --- | --- |
| 4.6 | 570 | 5(5) | 9(4.6) | 5 | 45(23+2) |
| 6.3 | 470 | 7(50) | 4(0.5) | 5 | 20(3+1) |
| 7.6 | 410 | 13(150) | 2(0.2) | 5 | 10(1+1) |
| 8.8 | 380 | 20(300) | 1.5(<1) | 5(>5) | 7.5(1+1) |
| 12 | 300 | 54(1000) | 0.5(<1) | 5(>50) | 2.5(1+1) |
| 18 | 220 | >100(>1000) | 0.25(<1) | 5(>50) | 1.5(1+1) |
| 28 | 150 | >100(>1000) | 0.25(<1) | 5(>50) | 1.5(1+2) |

- T. Satogota, RHIC

## NA 49/61 Future Program

- Gary Westfall, Quark Matter 2008

- M. Gazdzicki

## Proposed Energy and Mass Scans

- Gary Westfall, Quark Matter 2008

## Addition of TOF to STAR

- Gary Westfall, Quark Matter 2008

- STAR will add TOF for Run 10
- The TOF will provide excellent particle identification for *π*, *K*, and *p* for a large fraction of the measured particles event-by-event
- Improved *K*/*π* fluctuation measurements
- Improved balance functions with identified *π*, *K*, and *p*
- See talk by G. Odyniec, session XXIV

- P. Sorensen

- Charged pions and kaons
- 0.2 < pt < 0.6 GeV/c

## Conclusions 1

- We have experimental results for correlations and fluctuations covering incident energies where one might expect effects from the QCD critical point and we have some hints in the
- However, the results are not conclusive
- In particular, we have several different variables, acceptances, and interpretations that need to be unified
- We need to measure correlation fluctuation variables over the broadest range in incident energy and system size

- Gary Westfall, Quark Matter 2008

## Conclusions 2

- The SPS and RHIC scans will provide an excellent opportunity to study the QCD critical point
- SPS system/energy scan will add a large number of points in *T*/*μ**B* space in the search for the critical point
- We also look forward to correlations and fluctuations related to the QCD phase transition at GSI/FAIR

- Gary Westfall, Quark Matter 2008

## Extra Slides

- Gary Westfall, Quark Matter 2008

## Balance Function with Identified Pions

- Gary Westfall, Quark Matter 2008

- Charged pion pairs
- 0.2 < pt < 0.6 GeV/c

- The excellent particle identification for *π*, *K*, and *p* for a large fraction of the measured particles event-by-event will allow new kinds of event-by-event measurements such as the balance function with identified particles

## Relation between Net Charge Fluctuations and the Balance Function

- Gary Westfall, Quark Matter 2008

- Jeon and Pratt
- PRC 65, 044902 (2002)

## HBT

- Gary Westfall, Quark Matter 2008

## HBT

- Gary Westfall, Quark Matter 2008