Transcript Document

Prospects for STAR with the Time-of-Flight Detector
and Muon Telescope Detector
Lijuan Ruan
(Brookhaven National Laboratory)
Outline:
• What have we learnt at RHIC
• What still needs to be addressed
• Physics capabilities from Time of Flight Detector
• Physics perspectives with Muon Telescope Detector
• Conclusions
08/10/2010
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RHIC @ Brookhaven National Laboratory
BRAHMS
PHOBOS
99.995% the speed of light
PHENIX
h
STAR
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197Au
+ 197Au Collisions at RHIC
Central Event
E = m c2
STAR
08/10/2010 (real-time Level 3)
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S. Bass
Physics Goals at RHIC
& LGT study the properties of matter with partonic
CYMand
Identify
degrees of freedom
(flavor,
color, sound, temperature …)
hadronization
PCM & clust.
1. Penetrating probes: parton energy loss in NFD
the medium
identified particle spectra at high pT,
NFD & hadronic TM
heavy flavor and quarkonia
jets …
string & hadronic TM
PCM & hadronic TM
2. Bulk properties: energy density, collectivity and freeze out properties
identified particle spectra at low pT, v2 …
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PID Spectra – Freeze-out dynamics
RHIC’s strength of measuring many particle species:
K(p); resonant and multi-strangeness states
Chemical freeze-out: distribution of particle species
Kinetic freeze-out: momentum spectra
RHIC: Nucl. Phys. A 757 (2005)
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Kinetic freeze out properties
Blast-wave model:
E.Schnedermann et al, PRC48 (1993) 2462.
dn
 m cosh    pT sinh  
  r dr mT K1  T
 I0 

mT dmT 0
T
T

 

R
where
  tanh 1 r
and
r (r)  s f (r)
peripheral
central
STAR: Nucl. Phys. A 757 (2005) 102
1.
Kinetic freeze out temperature decreases from peripheral to central
collisions
2. Velocity profile increases from peripheral to central collisions.
3.  and  have smaller cross sections at hadronic stage, freeze out
earlier.
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Probes between chemical and kinetic freeze out
Resonances: probe hadronic
interactions via re-scattering
of their daughter particles and
regeneration
Life time:
0 (1.3 fm)
++ (1.6 fm)
K* (3.9 fm)
(1385) (5.5 fm)
(1520) (12.6 fm)
 (41 fm)
…
(p) > () > (K)
Derive the life time of hadronic
stage 3-10 fm/c
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PRL97(2006)132301
Phys. Lett. B 612 (2005) 181
Phys. Rev. Lett. 99 (2007) 112301
Phys. Rev. C 71 (2005) 64902
Phys. Rev. Lett. 92 (2004) 92301
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High pT: penetrating probe
q
q
RHIC: Nucl. Phys. A 757 (2005)
In central Au+Au collisions at RHIC: Fragmentation + energy loss at pT > 6
GeV/c:
Significant suppression of inclusive charged hadron observed at pT>6 GeV/c:
dNg/dy~1000. M. Gyulassy et al., nucl-th/0302077.
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Intermediate pT: baryon/meson pattern
At pT~2 GeV/c, pbar/ ratio ~1. It can not be factorized jet
fragmentation (Dq/g(pbar)/Dq/g() << 1).
At 2<pT<5 GeV/c, p,  increase faster than , KS, K from peripheral to
central collisions. STAR: Phys. Rev. Lett. 92 (2004) 052302; PHENIX: Phys. Rev. Lett. 91
(2003) 172301; V. Greco, et al., Phys. Rev. Lett. 90, 202302 (2003).
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Recombination/Coalescence at hadronization
Fragmentation works for p+p collisions for hadrons at pT
> 2 GeV/c
fragmenting parton:
ph = z p, z<1
recombining partons:
p1+p2=ph
R.J. Fries, QM2004
If phase space is filled with partons, recombine/coalesce
them into hadrons. (hadrons at 2 < pT < 6 GeV/c)
baryon enhancement, v2 NCQ scaling.
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Centrality Dependence: RCP in Au+Au
STAR: Nucl. Phys. A 757 (2005) 102
2<pT<6GeV/c, K*,  follow meson trend  coalescence + jet model
works, however, errors on K*, , , are also big.
Coalescence does not necessarily mean that baryon (meson) RCP are
the same.
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From previous to now
• Bulk properties (energy density, collectivity and
freeze out properties): pT<2 GeV/c
• Jet energy loss + fragmentation: high pT>6 GeV/c
• Coalescence/recombination: intermediate pT.
The recent resents on:
Freeze out properties: thermal-like replaced by
Tsallis-like
Constrain fragmentation function: light quark and
gluon FFs
Jet quenching: q,Q,g
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Tsallis statistics in Blast-wave model
d3N
(u  p )/T fo
E

e
pd   

dp 3
BGBW:
 mT cosh    pT sinh  
R
dN
  rdrmT K1 
I 0 


0
mT dmT
T
T
fo
fo

 


r
r  S  
R
  tanh 1  r
1
I0 ( z) 
2
2
 exp[ z cos( )]d ,
0
  0.5,1, 2

K1 ( z )   cosh( y ) exp[  z cosh( y )]dy
0
With Tsallis distribution:
exp( 
mT
m
(q  1)mT 1/(q 1)
)  exp q ( T )  [1 
]
T
T
T
Tsallis Blast-wave (TBW) equation is:
Y

dN
q 1
 mT  cosh( y)dy  d  rdr{1 
[mT cosh( y) cosh(  )  pT sinh(  ) cos( )]}1/(q 1)
mT dmT
T
Y

0
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R
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Fit results in Au+Au collisions
Zebo Tang,Yichun Xu, Lijuan Ruan, Gene van Buren, Fuqiang Wang and Zhangbu Xu, Phys. Rev. C 79, 051901 (R) (2009)
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Fit strange hadrons only
All available species
Strangeness, Au+Au 0-10%:
<> = 0.464 +- 0.006
T = 0.150 +- 0.005
q = 1.000 +- 0.002
chi^2/nDof = 51/99
Tstrange>Tlight-hadrons
Strangness decouple from
the system earlier
M. Shao, L. Yi, Z. Tang, H. Chen, C. Li and Z. Xu, arXiv:0912.0993
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Centrality dependence for T and <T>
strange
non-strange
strange
non-strange
strange
non-strange
non-strange
strange
 Multi-strange hadrons decouple earlier
 Hadron rescattering at hadronic phase doesn’t produce a
collective radial flow, instead, it drives the system off equilibrium
 Partons achieve thermal equilibrium in central collisions
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M. Shao, L. Yi, Z. Tang, H. Chen, C. Li and Z. Xu, arXiv:0912.0993
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Flavor and color charge dependence of energy
loss
STAR: PRL98(2007) 192301
STAR: PRL97,152301(2006)
Bottom energy loss, significantly as light flavor: no mass effect on partonic energy loss?
heavy quark spectra steeper than calculated in the FONLL calculations?
Collisional dissociation of heavy mesons, in-medium heavy resonance diffusion,
multi-body mechanisms might play an important role for heavy quark energy loss
A. Adil and I. Vitev, Phys. Lett. B649, 139 (2007); H. van Hess, V. Greco and R. Rapp, Phys. Rev. C 73; 034913
(2006); W. Liu and C. M. Ko, nucl-th/0603004
Common suppression of protons and pions: no color charge dependence of partonic
energy loss?
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Discussion: g/q jets conversion in the medium
gluon
Quark
At RHIC,
initially produced hard strange quarks are much fewer than the strange quarks in a hot, dense
•medium.
gluon/quark jets conversion in the medium. (W. Liu et al., nuclC.M. Ko,the
ISMD2006.)
Theth/0607047;
interaction between
initially produced light quark (gluon) and the medium will lead to
elastic
scattering:
q g <-> gatq,high
qbar
more
strangeness
production
pTg <-> g qbar.
inelastic scattering: q qbar<->g g
Using the same factors, Liu and Rries predicts RAA(KS0) > RAA ()
This leads to jet hadron chemistry change in AuAu collisions compare to in pp
•collisions.
There is
net quark to gluon jets conversion in the medium.
W. Liu and R. Fries, PRC77(2008)054902
•
A much larger net conversion is needed to explain the data.
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Constrain fragmentation function
In 200 GeV p+p collisions
•
-/+, pbar/p decrease
versus pT indicating
valence quark effect
plays a significant role at
high pT in particle
production
•
PYTHIA can describe the
ratios better but deviates
from the spectra data.
•
NLO calculations
describe spectra better
but deviate from ratio
STAR preliminary
Yichun Xu, QM2009
This is important to understand gluon/quark contribution factors to proton, pion and kaon
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Constrain intermediate pT model calculations
STAR preliminary, QM2006
There are quantitative differences between data and current models at
intermediate pT.
Hard component should be able to help constrain the reco/coalescence model
calculations.
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What have we learnt so far
A hot, dense medium with partonic degree of freedom
create at RHIC:
Jet quenching
Baryon enhancement
…
Next:
The details of jet quenching and coalescence
What’s the temperature of the medium?
What’s the chemical composition?
Have we observed color screening effect?
Whether the system is thermalized and how to achieve
thermalization?
What’s the initial state effect?
…
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Hadron/Electron PID capability
|1/β-1|<0.03
TPC
TOF PID: (, K) ~ 1.6, p ~ 3 GeV/c.
rdE/dx PID: (, p) 2.5-12 GeV/c
TOF+rdEdx PID: 0.3-5 GeV/c
electron
s
Clean electron PID can be obtained up to
PT < 3 GeV/c.  measure the
semileptonic decay of open charm.
(STAR Collaboration, PRL94(2005)062301)
STAR Collaboration, PLB616(2005)8; nuclex/0606003.
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Muon identification at low pT
0.15<pT<0.25 GeV/c, DCA < 3 cm
STAR Collaboration, ArXiv: 0805.0364
Significantly reduce the systematic
uncertainty on the charm cross section
measurement.
Yifei Zhang
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PID physics at intermediate pT
200 GeV Au+Au
STAR Preliminary
• Number of constituent quark
(NCQ)
• Transition regime 2<pT<5 GeV/c
• Multi-strangeness baryons
Surprising discoveries at RHIC:
Coalescence of quarks?
New hadronization mechanism?
• Heavy Mesons (K*, )
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What can TOF bring – spectra, efficiency,
background rejection
•
•
•
•
•
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Particle
pT range (GeV/c)
TPC+TOF/TPC
K*0
0-1
2.0
K*0
1-2
1.85
K*0
2-3
1.74
K*0
3-5
1.39

0-2
5.0

2-5
3.42
Λ*
0-1.6
11.4
D0
0-5
4.6
Kp pT range (1 < pT < 3 GeV/c), efficiency > 80%
 efficiency x 8
Resonances x 2--10
Reject correlated background due to misidentified particles.
Eliminate this systematic error ( 20%)
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Jet associated spectra/correlations
Leading
hadrons
Medium
Jet dissipates energy
•
•
•
•
Away-side spectra approaching the bulk
Chemically and thermally?
Need PID 1<pT<4 GeV/c
Not be able to do without FULL TOF
Another surprise waiting for discovery?
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Energy scan: search for the critical point
B
√sNN
J. Phys. G30 (2004) S1381
———————————————————
180 MeV
420 MeV
725 MeV
25 GeV
7.5 GeV
4.5 GeV
———————————————————
Cleymans, et.al.
08/10/2010
•
•
Energy scan: run 10
Mapping out the critical point:
Fluctuation K/, p/  need PID, large
acceptance.
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(Di)lepton program with STAR-TOF
Heavy flavor (charm) physics: heavy, Mc  1.3 GeV >> Tc, QCD, Muds
created at intial impact, sensitive to evolution/thermalization:
• charm cross section and medium modification (q,g,Q):
DK ; ceX; cµX
• Heavy quarkonia, color screening, charm quark recombination:
J/e+ e-
efficiency
Dilepton physics: QGP thermal radiation and vector meson inmedium properties, possible chiral symmetry restoration:
STAR J/ at intermediate mass (1.1-3.0 GeV)
• QGP thermal radition: di-lepton
• Vector meson in-medium properties: ρee, ωee, φee
pT (e)>1.5 GeV/c
pT (GeV/c)
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Prototype TOF related charm results
•
•
•
•
Charm total cross section scales approximately with Nbin
Charm produced at initial impact, sensitive to the evolution/thermalization
Suppression at pT(e) >1.5 GeV/c  strong energy loss for charm
Full TOF improves (x5) charm hadronic reconstruction
STAR Collaboration, Phys. Rev. Lett. 94 (2005) 062301; ArXiv: 0805.0364.
Yifei Zhang
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Nuclear modification factor RAA
• Consistent with no
suppression at high pT:
RAA(pT>5 GeV/c) =
1.4± 0.4±0.2
arXiv: 0904.0439
Zebo Tang
• RAA(pT>5GeV/c) > 0.6
(97% C.L.) 
RAA increase from low pT to
high pT STAR:PRC80(2009)014902
• Jet quenching: strong open charm suppression. J/ is likely to be
produced dominantly through CS states A. Adil and I. Vitev, Phys. Lett. B649, 139 (2007), and I.
Vitev private communication; S. Wicks et al., Nucl. Phys. A784, 426 (2007), and W. A. Horowitz private communication.
•Contrast to AdS/CFT+ Hydro prediction (99% C.L.) H. Liu, K. Rajagopal and U.A.
Wiedemann PRL 98, 182301(2007);T. Gunji, J. Phys.G 35, 104137 (2008)
•Formation time, gluon dissociation, recombination, B reproduces the trend
X. Zhao and R. Rapp (2007), arXiv:0712.2407.
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Future dramatic improvement
of J / at low pT
dE/dx after TOF cut
significance
~ 5.7 σ
0-20% d+Au
STAR, C. Powell, QM2009
PHENIX Acceptance:
|h|<0.35, =2*/2
STAR TOF-Upgrade Acceptance: |h|<0.9, =2*
J/ yields from 1 billion minbias Au+Au events:
43.8x10-9/0.040x109*292*0.5*1.8*0.5=
144,0000.3% v2 error
J/pp
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N
Nbin
e
y
pT (e)>1.5 GeV/
RAA
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QGP signature
R. Rapp, hep-ph/0010101
• Vector meson properties
• Thermal dileptons/photons
• Heavy flavor
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R. Rapp, hep-ph/0010101
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Di-lepton Program at STAR
STAR @ 200 GeV p+p collisions
107 M events
Bingchu Huang, Yifei Zhang
di-lepton at run9 p+p collisions:
1) 5  ee signal was observed.
2) Cocktail + simulation can describe the di-lepton continuum.
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Muons: Penetrating Probes
A large area of muon telescope detector
(MTD) at mid-rapidity, allows for the
detection of
• di-muon pairs from QGP thermal radiation, quarkonia, light vector
mesons, possible correlations of quarks and gluons
as resonances in QGP, and Drell-Yan production
• single muons from their semi- leptonic decays of heavy flavor
hadrons
• advantages over electrons: no  conversion, much less Dalitz
decay contribution, less affected by radiative losses in the detector
materials, trigger capability in Au+Au
Z. Xu, BNL LDRD 07-007;
L. Ruan et al., Journal of Physics G: Nucl. Part. Phys. 36 (2009) 095001
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Muons: Penetrating Probes
The initial temperature of sQGP; the mass origin of hadrons;
color screening features of heavy quarkonia …
Measurements
low mass di-muons
Physics
thermal radiation of QGP;
in-medium modifications of vector
meson (  ), chiral symmetry
restoration
intermediate mass di-muons
thermal radiation of QGP;
heavy flavor modification;
resonances in sQGP
large mass: heavy quarkonia
T of QGP, color screening,
quarkonium production mechanism
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Concept of Design
A detector with long-MRPCs covers the
whole iron bars and leave the gaps inbetween uncovered. Acceptance: 45% at
|h|<0.5
117 modules, 1404 readout strips, 2808 readout
channels
Long-MRPC detector technology, HPTDC
electronics (same as STAR-TOF)
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MTD Real Acceptance
  














: 0 trays per backleg (3)
: 5 trays per backleg (18)
J/ efficiency
J/psi efficiency dropped
by a factor of 3.
Others : 3 trays per backleg (9)
Total: 117 trays
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High Mass Di-muon Capabilities
1. J/: S/B=6 in d+Au and S/B=2 in
central Au+Au
2. With HFT, study BJ/ X; J/
using displaced vertices
3. Excellent mass resolution: separate
different upsilon states
Heavy flavor collectivity and color
screening, quarkonia production
mechanisms:
J/ RAA and v2; upsilon RAA …
Quarkonium dissociation temperatures – Digal, Karsch, Satz
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Compared to Υ  e+e- with HFT
With HFT, it’s hard to
separate different upsilon
states;
e+e- channel samples
collisions of |vz|<10 cm;
can not sample full
luminosity due to
more material at |vz|>10 cm
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Future Measurement Projection
J/
Υ
J/
J/ RAA and v2;
Υ RAA versus Npart…
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Distinguish Heavy Flavor and Initial Lepton Pair
Production: e-muon Correlation
e correlation simulation with Muon Telescope Detector at STAR from ccbar:
S/B=2 (Meu>3 GeV/c2 and pT(e)<2 GeV/c)
S/B=8 with electron pairing and tof association
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Summary
•
TOF physics:
coalescence, jet quenching, QCD critical point …
dilepton continuum from thermal radiation, vector meson in-medium
properties, charm and heavy quarkonia
•
MTD will advance our knowledge of Quark Gluon Plasma:
trigger capability for low to high pT J/ in central Au+Au collsions
excellent mass resolution, separate different upsilon states
e-muon correlation to distinguish heavy flavor production from initial
lepton pair production
different background contribution provides complementary
measurements for dileptons
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Backup
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Upsilon Statistics Using MTD at |y|<0.5
Delivered luminosity: 2013 projected;
Sampled luminosity: from STAR operation performance
Collision
system
Delivered
lumi.
12 weeks
Sampled
lumi.
12 weeks
(70%)
Υ counts
Min. lumi.
precision on
Υ (3s) (10%)
200 GeV p+p
480 pb-1
200 pb-1
336 pb-1
140 pb-1
930
390
420 pb-1
500 GeV p+p
1200 pb-1
840 pb-1
6970
140 pb-1
200 GeV
Au+Au
22 nb-1
16 nb-1
1770
10 nb-1
Upsilon in 500 GeV p+p collisions can also be measured in good precision.
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MTD schedule
A run-11 prototype is also planned to address several integration issues.
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Institutional responsibilities
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