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UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Page 1: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 1Rosi Reed

Low Energy Test Run Results

Rosi Reed

University of California at Davis

Page 2: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 2Rosi Reed

Introduction

• Event quality• Beam Pipe Events

– Spectra– HBT

• Beam Profile Analysis

2

Page 3: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Summary 9 GeV Test Run

3

5.5 % with Vertex

Yellow = cogged at Phenix

3.3% with Vertex r < 2 cm

Page 4: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 4Rosi Reed

Multiplicity – Cut on Events heading into the TPC

30% Central

62.4 GeV points are scaled to match 3.2 GeV points at Nch = 13

Au-AlAu-Al + Alpha-Al

An increased yield in low multiplicity events could be the result of alpha particles from Au break-up hitting the beam pipe

Page 5: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 5Rosi Reed

Au-Al HBT Analysis – Rigidity

π+

π-

pt

d

Page 6: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 6Rosi Reed

Some Calculations – Au-Al Events

Page 7: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Eta for Au-Al Events

30% Central

All

All

30-100% Central

Events with a Negative Average Eta Flipped for Graphs 2-4

12

43

Increase at Eta = 0 from Spectators from Al

Page 8: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 8Rosi Reed

Eta for Au-Al Events

30% Central

Proton

30% Central

Pion

30-100% Central

Proton

30-100% Central

Pion

PID done through nSigma cut

Page 9: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Pion+ Proton Yield for Au-Al Eventsybin = 0.5 around ycm

No efficiency corrections made

T ~ 80 +/- 2 MeV T ~ 91 +/- 3 MeV T ~ 99 +/- 4 MeV

Page 10: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Proton/Pion Ratio for Au-Al Events

Increase in p vs pi at y = 0 comes from Al spectators

Page 11: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Au-Al HBT Analysis (root SNN = 3.2)

• Event quality cuts:– Vr > 2 cm (Not Au+Au collisions)– |Vz| > 75 cm (Not Au+Be collisions)– Vz*TotalEventPz < 0 (Events “into” TPC)– Events with Pz < 0 flipped (pz = pz*-1)– Multiplicity > 10 (30% Central)

• Track Quality cuts:– Assumed all negatively charged tracks were pions– nHits/nPossHits > 0.5 for either TPC or FTPC

Page 12: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Au-Al pi- HBT Analysis

Page 13: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Beam profile vs time

• Analyzed Vx vs Vy distributions vs time for – Run 72 (13:26:02 – 28:25)– Run 73 (13:36:10 – 13:37:30)– Run 74 (43:12 – 44:21)

• Binned distributions with the same Vernier scan location

• No Z vertex cuts• Cut on Vr < 2

Page 14: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Gaussian Multiplication

• Beam is gaussian in shape• Distribution of collisions in xy space is equal

to the beam distributions multiplied by each other– Also gaussian in shape

Page 15: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Assuming the beams have the same width

Page 16: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Beam profile vs time Summary

Calculated from Vx vs Vy distributions

# Beam-Beam Events

Blue = Run 72, Yellow Run 73, Grey Run 74

Page 17: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 17Rosi Reed

Beam Sigmas calculated from formula on pg 15

Sigma X = 1.75 mm +/- .20

Sigma Y = 2.40 mm +/- .15

Error bars reflect statistical error only

If our assumptions are correct, these distributions should be flat

Beam Sigmas

Page 18: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 18Rosi Reed

Vernier Scan Versus Average Event Location

Slope should be +/- 0.5 if our assumptions were correct

Page 19: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Time Decay for Run 97

Empty events fall off exponentially

Beam-Beam and Empty Events have the same time constant

Beam-Pipe events have twice the time constant of Beam-Beam and Empty Events

Run 97 occurred after BBC threshold was lowered

Page 20: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

UC Davis June 16-21st 2008 20Rosi Reed

Events During Vernier Scan

During Vernier Scan it appears the empty event rate follows the beam-beam event rate in runs 72 and 73.

Page 21: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Conclusion

• We still do not understand why we triggered– Empty events

• BBC threshold changed but the trigger rate still seems to be beam related

– Beam-Pipe Events• Beam Pipe events are a combination of Au-Pipe

Material and Alpha-Pipe Material

• We have a reasonable estimate of the good event rate

Page 22: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Backup Slides

Page 23: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Vernier Scan

Page 24: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Vx Vy Distribution of 1st Primary Vertex at 9 GeV

24

Page 25: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Z Axis distributions

Thin Be beam pipe extends from Z = -75 cm to 75 cm. Outside 75 cm there is a thicker Al beam pipe.

3.6 AGeV Au+Be

3.6 AGev Au+Al

3.6 AGev Au+Al

Page 26: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Number of Vertices per Event

26

• 78.9% of events had 1 primary vertex– 81.6% of “beam-beam” events have 1 primary vertex– 71.6% of “beam-pipe” events have 1 primary vertex

(Data taken from runs 97,76,72)

Page 27: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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XY Location of 2nd + 3rd Vertices for Events with Vertex 1 r > 2 cm

Data from Runs 97, 76, 72

Only 8 % of secondary vertices and 8 % of teritary vertices of events labeled as beam pipe events are located in the center

Indicates that most events labeled as beam pipe events are not Au-Au events that have kicked off an energetic particle.

Page 28: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Average Eta by Event

28

Run 97, 76, 72

Eta averaged over primary tracks only

Page 29: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Vx vs Vy Distributions for Same Vernier Scan Locations

Page 30: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Vx vs Vy Distributions for Same Vernier Scan Locations

Page 31: UC Davis June 16-21 st 2008 1 Rosi Reed Low Energy Test Run Results Rosi Reed University of California at Davis

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Track Eta Distribution for Eta Ave > 0