Overview of TPC Reactions Experiments

1
Overview of TPC Reactions Experiments

• NSCL TPC Workshop
• Gary Westfall
• Michigan State University

2
Outline

• Focus on reactions with incident energies up to
  200 MeV/nucleon with variable isospin beams
• Selected existing data on isospin dependence in
  reactions
• Existing TPCs for nuclear reactions
• EOS/E895
• NA49
• STAR
• ALICE
• Considerations for TPC for NSCL reactions
• Physics to be addressed

3
Proposed Observables
As a function of isospin of the projectiletarget
system, centrality, and incident energy

• Neutron/proton energy spectra
• Neutron and proton flow
• px vs. y (v1)
• Elliptic flow (v2)
• As a function of pt
• Disappearance of flow (balance energy)
• ?/? - spectra
• ?/? - flow
• px vs. y (v1) and elliptic flow (v2)
• As a function of pt
• Isotope energy spectra
• t/3He ratio, 3He/4He ratios, 6Li/7Li ratios,
  6He/6Li
• Isotope flow, p, d, t, 3He, 4He, 6Li, 7Li
• px vs. y
• Elliptic flow
• As a function of pt

4
Features of NSCL Energy Range for Reactions
All depend on the isospin asymmetry!

• Incident energy dependence of directed transverse
  flow
• Balance energies occur
• Disappearance of flow (v1 goes to zero)
• Incident energy dependence of elliptic flow
• Transitions energies occur
• In-plane to out-of-plane (v2 changes sign)
• Increasing pion production with increasing energy
• Energy dependence of isospin dependence of
  multifragmentation
• Onset of dramatic radial flow
• Reach above normal nuclear density

5
Isospin Dependence of Flow
Flow is always higher for neutron-rich system
55 AMeV
6
Isospin Dependence of Balance Energy
58Fe58Fe 4? Data
58Fe58Fe Daffin and Bauer BUU, ? -0.3
58Ni58Ni Daffin and Bauer BUU, ? -0.3
58Ni58Ni 4? Data
58Fe58Fe B.A. Li, IBUU
58Ni58Ni B.A. Li, IBUU
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Predictions for the Isospin Dependence of Flow
DiToro, Yennello, and LiEPJA, 30, 153 (2006)
8
Predictions for the Isospin Dependence of Flow
DiToro, Yennello, and LiEPJA, 30, 153 (2006)
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Predictions for the Isospin Dependence of Flow
3H
3He
DiToro, Yennello, and LiEPJA, 30, 153 (2006)
Flow is predicted to be 20 larger for
3He, opposite from Coulomb effects
10
TPCs Can Address These Experimental Challenges

• A TPC is a 4? solid angle device with excellent
  spatial resolution and good particle
  identification
• TPCs can take data at high rates
• TPCs can take data at 1000 events/second
• TPCs can handle high interaction rates and
  trigger on interesting events
• TPCs can measure flow for charged particles
• TPCs have isotope resolution for light particles
• TPCs can measure ? and ? - spectra and flow
• Using external neutron detectors, TPCs can
  measure neutron flow
• Using a TP-MUSIC, TPCs can study peripheral
  collisions and reverse kinematics
• Projectile fragmentation, multifragmentation

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TPCs for Nuclear Collisions

• EOS/E895 - Bevalac, AGS (Fermilab)
• Fixed target energies up to 10 GeV/nucleon
• Fixed target energies down to 100 MeV/nucleon
• NA49 - SPS
• Fixed target energies up to 160 GeV/nucleon
• Fixed target energies down to 20 GeV/nucleon
• Actually 4 TPCs
• 2 vertex (magnetic field - rigidity measurement)
• 2 main (particle ID - energy loss measurement)
• STAR - RHIC
• Collider energies
• AuAu, 10 GeV/nucleon 10 GeV/nucleon
• AuAu, 100 GeV/nucleon 10 GeV/nucleon
• pp (100 GeV 100 Gev, 250 GeV 250 GeV)
• dAu, 100 GeV/nucleon 100 GeV/nucleon
• ALICE - LHC
• Collider energies
• PbPb, 2.76 TeV/nucleon 2.76 TeV/nucleon
• pp, 7 TeV 7 TeV

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TPC Comparisons

• Typical values
• Sampling rate 10 MHz
• Shaping time 180 ns
• Gas (atmospheric pressure)
• 90Ar, 10 CH4 (EOS and STAR)
• 90 Ne, 10 CO2 90 Ar, 5 CO2, 5 CH4
• 90 Ne, 10 CO2, 5 N2 (ALICE)

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EOS
14
EOS - E895
15
EOS PID
16
NA49
17
NA49 Event
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Interior of NA49 MTPC Field Cage
19
NA49 VTPCs
20
STAR Detector
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Drawing of STAR TPC
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Event in STAR TPC
23
STAR PID from AuAu at 200 GeV
K
p
?
p
24
ALICE TPC
25
NSCL TPCDipole
TP-MUSIC
Neutron Detectors
Charged Particle TOF
Beam
TPC
Dipole Magnet
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TPCSolenoid
Charged Particle TOF
TOF
TP-MUSIC
Beam
TPC
Neutron Detectors
Solenoid Magnet
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Simulated NSCL PID for Isotopes
Assume fireball with T 100 MeV
4He
3He
7Li
6Li
t
d
p
?
Simulation using STAR dE/dx and momentum
resolutions
28
Simulated PID for Isotopes, Scaled to EOS
Simulation using STAR resolutions
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Simulated PID for Light Particles
t
p
d
?
Simulation using STAR dE/dx and momentum
resolutions
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Summary

• A TPC for NSCL can carry out a cost-effective
  experimental program directed at the study of the
  isospin dependence of the nuclear equation of
  state based on well established detector and
  electronics techniques
• A TPC can take advantage of the huge range in
  isospin available at NSCL

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Idea for NSCL TPC