star as a fixed target experiment?nuclear.ucdavis.edu/~cebra/star/fixedtarget_06jan11.pdf · star...

STARSTAR

Slide 1 of 40Brovko, Haag, Cebra

January 06, 2011

LF Spectra Phone Conference

STAR as a Fixed Target Experiment?

Sam Brovko, Brooke Haag, Daniel Cebra

Abstract 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.

STARSTAR

Slide 2 of 40

Low Energy Reach of Fixed Target

Collision

Energy

(GeV)

Single

Beam

Energy

Single

Beam Pz

(GeV/c)

Fixed

Target

Root 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

ner

gy

Sca

n

STARSTAR

Slide 3 of 40

Beam Energy Scan

64 GeV

Fixed

Target

points

What

if the

critical

point

is

here?

Or here?

STARSTAR

Slide 4 of 40

Be Beam

Pipe

Al Beam

PipeAl Beam

Pipe

h=1.0 h=1.5

h=2.0

h=1.0

h=1.5

h=2.0

STARSTAR

Slide 5 of 40

Required Steps:

1) Demonstrate that we can select Al target events

2) Demonstrate that we can demonstrate that we have

am Au projectile

3) Demonstrate that we know that collision energy

3 AGeV 197Au + 27Al

STARSTAR

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

STARSTAR

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/dx

The 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

STARSTAR

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 Cebra

October 6, 2009

STAR Collaboration Meeting

LBNL

Determining that the projection is Au

7.7 GeV Au+AuProjectile + 27Al

From E895 Au+Au

Mmax at 2 AGeV is ~200

Mmax at 4 AGeV is ~300

Npart ~380

Mmax ~50

For Au+Al:

Npart ~70

Expect Mmax ~45 from

extrapolation of E895

STARSTAR

Slide 10 of 40

Determining that the projection is Au

Glauber Prediction for 3 AGeV Au+Al

STAR

3 AGeV

Au+Al

data

STARSTAR


October 6, 2009


LBNL

STARSTAR

Slide 12 of 40

Pion Spectra from 3.85 AGeV Au+Al

STARSTAR

Slide 13 of 40

Acceptance for Fixed Target

h = 1.8

STARSTAR

Slide 14 of 40

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.

STARSTAR

Slide 15 of 40

Backup Slides

STARSTAR


October 6, 2009


LBNL

STARSTAR

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.

STARSTAR

Slide 26 of 40

Schematic Diagram of the beam pipe profile

STARSTAR


April 26, 2010

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

Vxy Vxy

Vz

(r>2)Vz

(r>2)

AlAlAl

Al

Be Be

6733 Au+Au

4150 Beam pipe

100863 Au+Au

2882 Beam pipe

~3000 Au+Al

~1000 Au+Be

2241 Au+Al

641 Au+Be

Au+Al |Vz|>75

Au+Be |Vz|<75

Au+Au r<2

Au+pipe r>2

Beam Pipe Locations

STARSTAR

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|>75

Au+Be |Vz|<75

Au+Au r<2

Au+pipe r>2

Vxy

Vz

(r>2)

Al Al

Be

Cu+Cu

Beam pipe

Beam pipe supports

STARSTAR

Slide 29 of 40

Beam-on-Pipe Collisions

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