Title: The Balance Function: Experimental Studies in STAR
1The Balance FunctionExperimental Studies in STAR
- Marguerite Belt Tonjes,
- G.D. Westfall, A.M. Vander Molen, the STAR
collaboration
2STAR
- Solenoidal Tracker At RHIC
- large acceptance detector with near 4? coverage,
study hadrons, jets, event-by-event, high pt
particles, strangeness.
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4Selecting Good Data
- Use AuAu 130GeV events from Year1 running,
summer, 2000 - Physics events
- Central trigger
- Minimum bias trigger
- -75cm vertexz 75cm
- -1cm vertexx 1cm,
- -1cm vertexy 1cm
5Selecting good TPC tracks
- Collaboration-wide selection cuts
- h lt 1.3
- 0.1 GeV/c pt 2 GeV/c
- DCA 1 cm (distance of closest approach to the
primary vertex ? choose tracks from the vertex) - Fit points 15
- Fit points/possible points gt 0.52
6PID
- Compare measured dE/dx with Bethe-Bloch
calculation of dE/dx for p, K, p, and e. - Particles within 2s of predicted ionization are
tagged.
7PID cuts
- ZPidp ln( Imeas/Ihyp(p))
- Imeas measured truncated mean for track
- Ihyp(p) expected ionization for p hypothesis
- p p0.7 GeV/c, and ZPidp0.2
- K p0.8 GeV/c, ZpidK0.2, ZPidpgt0.2,
ZPidpgt0.2 - P p 1 GeV/c, ZPidp0.2, ZPidpgt0.2,
ZPidKgt0.2 - E ZPide0.2, ZPidpgt0.2, ZPidKgt0.2,
ZPidpgt0.2
8Calculating the Balance Function
- For p pairs
- B 1/2 D - /N D- /N- - D/N - D- -/N-
- D- Histogram of y(p) - y(p-) , for all
possible pairs within an event. This histogram is
summed over all events. - For charged particle pairs, we sum over all
charged particle pairs. - D- Histogram of h(particle)-h(particle-)
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12Conclusions and future analysis
- More statistics are needed, and are being
analyzed - We see no difference between central and
peripheral events in HIJING - Need to study beam pipe/detector effects for
simulations - Study pt sensitivity
- Look at pp simulations
13Thanks to
- Gary Westfall, Skip Vander Molen, Scott Pratt for
much discussion of the analysis - The STAR Collaboration
- DOE
- NSF