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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
Slide 11 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
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
Slide 16 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
LBNL
STARSTAR
Slide 17 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
LBNL
STARSTAR
Slide 18 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
LBNL
STARSTAR
Slide 19 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
LBNL
STARSTAR
Slide 20 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
LBNL
STARSTAR
Slide 21 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
LBNL
STARSTAR
Slide 22 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
LBNL
STARSTAR
Slide 23 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
LBNL
STARSTAR
Slide 24 of 40Daniel Cebra
October 6, 2009
STAR Collaboration Meeting
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
Slide 27 of 40Daniel Cebra
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