STARSTAR

Slide 1 of 40Brovko, Haag, CebraJanuary 06, 2011

LF Spectra Phone Conference

STAR as a Fixed Target Experiment?

Sam Brovko, Brooke Haag, Daniel CebraAbstract for APS meeting: Analysis of fixed target collisions between gold ions in the beam and aluminum nuclei in the beam pipe using the STAR detector at RHIC will be presented. These fixed target collisions allow us to study a region of collision energy below the lowest energy scheduled for the RHIC beam energy scan. This might extend the region baryon chemical potential available for discovery of the critical point in the hadronic gas to quark-gluon plasma boundary in the nuclear matter phase diagram. In this talk, we will show preliminary results of pion, proton and light nuclei spectra as well as dN/dy distributions for pions and protons. Comparisons will be made to results from the AGS heavy ion program and to UrQMD simulations.

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Slide 2 of 40

Low Energy Reach of Fixed Target Collision Energy(GeV)

Single Beam Energy

Single Beam Pz (GeV/c)

Fixed TargetRoot S

Single Beam Rapidity

Center of Mass Rapidity

200 100 99.996 13.7 5.41 2.70

64 32 31.98 7.72 4.23 2.11

39 19.5 19.48 6.17 3.93 1.97

27 13.5 13.47 5.19 3.37 1.68

18 9.0 8.95 4.30 2.96 1.48

11.5 5.75 5.67 3.53 2.48 1.24

7.7 3.85 3.73 2.98 2.07 1.04

6.1 3.05 2.90 2.73 1.84 0.92

Bea

m E

nerg

y S

can

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Beam Energy Scan

64 GeV

Fixed Target points

What if the critical point is here?

Or here?

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Slide 4 of 40

Be Beam Pipe

Al Beam Pipe

Al Beam Pipe

h=1.0 h=1.5

h=2.0

h=1.0h=1.5h=2.0

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Slide 5 of 40

Required Steps:1) Demonstrate that we can select Al target events2) Demonstrate that we can demonstrate that we have

am Au projectile3) Demonstrate that we know that collision energy

3 AGeV 197Au + 27Al

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Slide 6 of 40

Selecting Aluminum Target

“7.7 GeV” Data set:Select Events with 100 < |Vz| < 200 and 2 < Vr < 5 cm

Vz Vx

VyCou

nts

Al AlBe

FTPC SVT Support Au+AuBeam pipe

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Slide 7 of 40

Determining the Collision Energy

Challenge – We have “oriented” the target parallel to the beam axis The target is infinitely “thick”.

The initial projectile energy is 2.94 AGeV. How much energy is lost prior to the Au+Al nuclear collision?

Range of 3 AGeV Au in Al is 64.8 cm due to dE/dxThe Au+Al nuclear interaction length is 3.63 cm.The Au ion travels only 5% of its range before

experiencing a nuclear collision, therefore it will lose only 5% of its energy.

Collision Energy is 2.8 +/- 0.2 AGeV

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Slide 8 of 40

Data to Support Collision Energy

Note, protons show a narrow distribution around mid-rapidity.

p+ contamination

STARSTAR

Slide 9 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

Determining that the projection is Au

7.7 GeV Au+AuProjectile + 27Al

From E895 Au+AuMmax at 2 AGeV is ~200Mmax at 4 AGeV is ~300

Npart ~380

Mmax ~50

For Au+Al:Npart ~70

Expect Mmax ~45 fromextrapolation of E895

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Slide 10 of 40

Determining that the projection is Au

Glauber Prediction for 3 AGeV Au+Al

STAR3 AGeV Au+Aldata

STARSTAR

Slide 11 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

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Pion Spectra from 3.85 AGeV Au+Al

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Acceptance for Fixed Target

h = 1.8

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Conclusions

• We can select fixed target Au+Al events • The collision energy is fairly well defined

• Fixed target geometry is adequate to RHIC sub-injection energy beams.

• We will focus on charged particle spectra.

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Slide 15 of 40

Backup Slides

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Slide 16 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

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Slide 17 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

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Slide 18 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

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Slide 19 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

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Slide 20 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

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Slide 21 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

STARSTAR

Slide 22 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

STARSTAR

Slide 23 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

STARSTAR

Slide 24 of 40Daniel CebraOctober 6, 2009

STAR Collaboration MeetingLBNL

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Slide 25 of 40

STAR Beam Pipe LocationA description of the STAR beam pipe can be found at arXiv:nucl-ex/0205008v1

Features:• Diameter of the central region of the beam pipe is 7.62 cm• There is/was a support disk for the SVT at 54.8 cm with OD

128 mm and ID 89 mm• From 0 to 76 cm => pipe is made of 1.0 mm thick beryllium• At 76 cm there is a weld to an 1.24 mm thick aluminum pipe• At 130 cm there is an Al to Al weld, no change in pipe

diameter or thickness.• From 76 to 402 cm => the pipe is 1.24 mm thick aluminum• There is a flange and bellows at 4 meters, the pipe diameter

goes to 12.7 cm• There is another flange and bellows at 7.12 meters.

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Schematic Diagram of the beam pipe profile

STARSTAR

Slide 27 of 40Daniel CebraApril 26, 2010

19.6 GeV Au+Au 2001 9.2 GeV Au+Au 2008

Vxy Vxy

Vz(r>2)

Vz

(r>2)

Al AlAlAl

Be Be

6733 Au+Au4150 Beam pipe

100863 Au+Au2882 Beam pipe

~3000 Au+Al~1000 Au+Be

2241 Au+Al641 Au+Be

Au+Al |Vz|>75Au+Be |Vz|<75

Au+Au r<2Au+pipe r>2

Beam Pipe Locations

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Slide 28 of 40

22.4 GeV Cu+Cu 2005 7.7 GeV Au+Au 2010

Vxy

Vz

(r>2)AlAl Be

Au+Au Beam pipe

Au+Al |Vz|>75Au+Be |Vz|<75

Au+Au r<2Au+pipe r>2

Vxy

Vz(r>2)

Al Al

Be

Cu+Cu Beam pipe

Beam pipe supports

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Slide 29 of 40

Beam-on-Pipe Collisions