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Low Energy Test Run Results. Rosi Reed University of California at Davis. Introduction. Event quality Beam Pipe Events Spectra HBT Beam Profile Analysis. 2. Summary 9 GeV Test Run. 5.5 % with Vertex. 3.3% with Vertex r < 2 cm. Yellow = cogged at Phenix.

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low energy test run results
Low Energy Test Run Results

Rosi Reed

University of California at Davis

introduction
Introduction

Event quality

Beam Pipe Events

Spectra

HBT

Beam Profile Analysis

2

summary 9 gev test run
Summary 9 GeV Test Run

5.5 % with Vertex

3.3% with Vertex r < 2 cm

Yellow = cogged at Phenix

multiplicity cut on events heading into the tpc
Multiplicity – Cut on Events heading into the TPC

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

Au-Al + Alpha-Al

Au-Al

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

30% Central

eta for au al events
Eta for Au-Al Events

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

All

All

2

1

30% Central

30-100% Central

Increase at Eta = 0 from Spectators from Al

4

3

eta for au al events1
Eta for Au-Al Events

30% Central

Proton

30% Central

Pion

PID done through nSigma cut

30-100% Central

Pion

30-100% Central

Proton

pion proton yield for au al events y bin 0 5 around y cm
Pion+ Proton Yield for Au-Al Eventsybin = 0.5 around ycm

T ~ 80 +/- 2 MeV

T ~ 91 +/- 3 MeV

T ~ 99 +/- 4 MeV

No efficiency corrections made

proton pion ratio for au al events
Proton/Pion Ratio for Au-Al Events

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

au al hbt analysis root s nn 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

Au-Al HBT Analysis (root SNN = 3.2)
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

Beam profile vs time
gaussian multiplication
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
beam profile vs time summary
Beam profile vs time Summary

# Beam-Beam Events

Calculated from Vx vs Vy distributions

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

beam sigmas
Beam Sigmas

Beam Sigmas calculated from formula on pg 15

Error bars reflect statistical error only

Sigma X = 1.75 mm +/- .20

Sigma Y = 2.40 mm +/- .15

If our assumptions are correct, these distributions should be flat

vernier scan versus average event location
Vernier Scan Versus Average Event Location

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

time decay for run 97
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

events during vernier scan
Events During Vernier Scan

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

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

Conclusion
z axis distributions
Z Axis distributions

3.6 AGev Au+Al

3.6 AGev Au+Al

3.6 AGeV Au+Be

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

number of vertices per event
Number of Vertices per Event
  • 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)

26

xy location of 2 nd 3 rd vertices for events with vertex 1 r 2 cm
XY Location of 2nd + 3rd Vertices for Events with Vertex 1 r > 2 cm

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.

Data from Runs 97, 76, 72

average eta by event
Average Eta by Event

Run 97, 76, 72

Eta averaged over primary tracks only

28