Transcript Beam Energy Scan at RHIC - Instytut Fizyki Jądrowej PAN

Experimental Approach
to the QCD Phase Diagram
Beam Energy Scan at RHIC
Grazyna Odyniec/LBNL
IV International Workshop on Correlations and Femtoscopy
Krakow, September 10-14, 2008
Outline :
QCD phase diagram - #1 single figure
Lattice and HI exp. (BES @ RHIC)
Grazyna Odyniec
Experimental questions
“QCD diagram is fairly EMPTY …”
K.Rajagopal, INT, opening talk
Exploring the rest of QCD phase diagram (T =0, m=0) by:
- heavy ion collisions
- lattice calculations (requires m/T not too large)
“Locate” the CP (:= second order point where a line of 1st order transition ends) either
- via experimental detection of signatures
- via lattice calculations
Stress on plural !
- need agreement of several signatures
- need agreement of different calculations
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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QCD phase diagram
Theory at the “edges” is believed to be
well understood:
M.Stephanov, hep-ph/0402115v1 (March 2006)
1. Lattice QCD finds a rapid, but smooth,
crossover at large T and mB~0
2. Various models find a strong 1st order
transition at T~0 and large mB
Either the theory is badly broken or
there must be a critical point.
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Theory
Predictions (models, lattice) for location of CP
M.Stephanov, hep-ph/0402115v1 (March 2006)
be careful !
this figure is of great
historical interest but it
does not represent the
span of theories that
are currently given
strong credibility
Lattice
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Lattice
Several methods on lattice (no agreement so far):
•
•
•
•
Reweighting : Fodor + Katz -> CP
Imaginary m: D’Elia + Lombardo, de Forcrand+Philipsen -> no CP
Taylor expansion of the pressure: Karsh, Gavai Gupta, -> CP
….
mB CP
< or ~ 2
Tc(m=0)
LR01, LR04
LTE03, LTE04
Theory problem: including mB>0 “breaks” existing numerical techniques at a very basic
level (the notorious “sign problem”)
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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hep-lat/0701002v1
Lattice - green points !
mB<500
Given the very significant theoretical difficulties,
data may lead the study of QCD phase diagram …
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Road Map by K.Rajagopal (INT,Aug.2008 ):
Experiment
+ Photons
(PHENIX)
but
No need to hit CP(!) – signature
will be just as big if you pass
anywhere in
mB ~ 100 MeV
(Hatta+Ikeda model, estimate is both
crude and uncertain, it would be good to
get it on lattice)
Focusing of trajectories that
pass near the critical point = NO
need to take very small steps in
mB !!!
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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“sQGP” at RHIC top energy
RHIC
At RHIC:
(1) mT-NQ scaling
LHC
(2) partonic collectivity
(3) deconfinement
RHIC experiments in agreement
hot and dense matter with partonic collectivity
has been formed at RHIC
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Beam Energy Scan at RHIC: sNN ~ 5-50 GeV
experimental window to QCD phenomenology
at finite temperature and baryon number density
At RHIC : indications of sQGP found
but remain unknown:
(1) properties of hypothesized sQGP
(2) boundary between hadronic and
partonic phases
(3) possible critical point
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Some indications of something new/not understood at lower energies
– NA49 at SPS
proton v2
non-monotonic K+/p+
behavior,“horn”, but
dynamical fluctuations quite
monotonic…?
NA49 PRC
40A GeV
collapse of proton v2 - signature of
phase transition (Stoecker,Shuryak),
but result depends on analysis
technique … ?
inconclusive
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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INT, Seattle, August 2008
T.Schuster/M.Mitrovski for NA49/NA61:
NA49 Results on the energy dependence of fluctuations:
Onset of deconfinement
Critical Point
Charge Fluctuations:
No sensitivity
No predictions
<pT> Fluctuations:
No predictions
No signal observed
Multiplicity Fluctuations: No sensitivity
No signal observed
Hadron Ratio Fluctuations:
No quantitative predictions
• but the structure seen in the energy dependence of K/π fluctuations cannot be explained
in a hadronic scenario !
Very nice analysis of Pb+Pb at sqrt(S)= 6.3, 7.6, 8.8, 13.3, 17.3 GeV
no dependence on sqrt(S)
Grazyna Odyniec
BES at RHIC - access to large range of mB and T
produces systems with lower freezout temperatures and higher baryon densities
-explore a broad region of the QCD phase
diagram
-look for the evidence of ordered transition
-study the evolution with beam energy of the
unusual medium properties found at RHIC
-do any of the partonic properties change or
“turn off” ?
-new surprises in unexplored region …
advantage of collider geometry !
At fixed target geometry:
detector acceptance changes with energy
track density at mid-y increases fast with energy
-> technical difficulties in tracking
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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What should be measured during BES ?
Mainly related to bulk properties
yields and particle ratios
T vs mB,
particle spactra (pt, rapidity, …),
strangeness production (K/p, multistrange, …),
fluctuations and correlations of many varietes (K/p,<pt>, HBT,v2@CP,…)
flow (v1,v2,v4, …) with charged and identified particles,
signals of parity violation,
“lumpy”(“clumpy” ?) final state
prospect of data will “encourage” theorists to be more specific
Search for : - disappearance of partonic activities
- fluctuations, correlations
turn on and off signature of deconfinement
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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The Signature !
decrease sqrt (S) -> increase mB
The signature is a CHANGE (not observable itself) = rise and then fall of Gaussian e-by-e
fluctuations of:
….
….
Note, number fluctuations will better survive the late time hadron gas
so, K/p fluctuations have more chance than <pt> fluctuations
-> lighter ions, shorter time in hadron gas phase – NA61 argument
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Excellent match with STAR detector capabilities
and existing, well understood STAR analysis techniques.
STAR after 2010 :
FTPC
Compatibility of FTPCs and FGT/HFT under investigation (only issue if run after 2010)
Other anticipated/studied issues: triggering and PID
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Triggering using BBCs
Studies indicate BBCs can be used for triggering during BES
Multiplicity larger than that for p+p
AuAu @ 5 GeV
AuAu @ 8.75 GeV
impact
parameter
BBC Inner
BBC Outer
BBC Inner
BBC Outer
0<b<3
5
27
12
54
3<b<6
11
30
21
57
6<b<9
22
35
39
40
b>9
44
30
66
8
BBC is sensitive down to single MIP hitting the detector
Triggering is not a problem
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Particle Identification in STAR
log10(dE/dx)
TPC+TOF (completed in 2010)+EMC+Topology
log10(p)
•
•
TOF alone: (p,K) up to 1.6 GeV/c, p up to 3 GeV/c
TOF+TPC(dE/dx, topology) up to 12 GeV (NIMA 558 (419) 2006)
Good quality PID over a broad range:
~ 0.2 – 12 GeV/c
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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STAR’s beam energy scan proposal (PAC 2008)
14 weeks physics+1 week commissioning
√sNN
μB
(GeV) (MeV)
Rate
(Hz)
Duratio
Events
n
(days)
5.0
550
0.5
Test
7
6.1
491
1.4
1M
23
7.7
410
2.7
2M
20
8.6
385
4
2M
15
12.3
300
10
5M
15
17.3
229
25
10M
12
27
151
30
10M
7
39
112
50
10M
6
mB<500
(Lattice)
Grazyna Odyniec
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STAR experience with Low Energy RHIC running
2001: 19.6 GeV Au+Au
2004: 22.4 GeV Cu+Cu
2007: 9 GeV Au+Au
2008: 9 (5) GeV Au+Au !
Preliminary
D. Cebra QM2008
Preliminary
E802 PRL81, 2650
(1998)
E866 PLB476, 1
(2000)
E917 PLB490, 53
(2000)
NA44 PLB471, 6
(1999)
WA98 PRC67,
104906 (2003)
NA49 PRC66,
054902 (2002)
NA49 EPJC33, S621
(2004)
NA49
arXiv:0710.0118v2
PHENIX PRC69,
034909 (2004)
PHENIX PRL88,
242301 (2002)
STAR PRL92, 112301
(2003)
STAR PLB595, 143
(2004)
Sufficient data to extract ratios, flow
velocity, HBT radii, v2
Data fit into systematics
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
19
2008: low energy run with 9.2 GeV Au+Au
Injecting and colliding Au+Au√sNN = 9.2 GeV, a few hours -> 4K good events !
Short test @√sNN = 5 GeV allowed study of beam optics
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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some preliminary plots from 9.2 GeV analysis
shown by H.Caines at INT, August 2008
primary vertex
STAR preliminary
Raw multiplicity
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Au+Au and Au+Al collisions !
Investigated primary vertex location:
They are “real”collisions.
Vertex Y
Au+Au collisions
Au+Beampipe collisions
Au+Al
Au+Al
R. Reed
Vertex X
Can see the change in beampipe material and thickness
Au+Be
Vertex Z (cm)
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Au+Au √sNN=9.2 GeV
_
STAR preliminary
All strange particles up to Λ
Raw Yield
0.018/event
Preliminary
Clean PID for π, K, p + anti-particles
Invariant mass (pπ) [GeV/c2]
Preliminary
Uncorrected charged particle midrapidity pT spectra out to ~4GeV/c.
(Not corrected.
Can’t extract physics yet)
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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• The unique RHIC energy scan program will map the QCD diagram
in sNN =5-50 GeV, (corresponding to mB ~ 600-150 MeV)
– systematic study of collective dynamics and fluctuations with p, L, X, W, p, K, K*, r, f...
– turning off partonic activities (e.g. v2 of f, W, D – no NQ scaling, quenching ->0, …)
but …
• experimentalist’s questions:
Can we get as quantitative as possible about critical line shape and use hydro
or something else to connect freeze-out point to it ?
Can we try to predict freezout versus sqrt(s) with and without CP ?
…
?
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
24
Experimentalist’s request to the community of
correlations/fluctuations experts :
other signals of the first order phase transition and CP
new analysis techniques, tools (correlations, fluctuations, ?)
We will study all of them with the data.
First run soon.
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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THANKS !
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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ETRA SLIDES
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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If there, a critical point doesn’t hide…
Image courtesy of C.Nonaka
•Hydro predicts that the evolution of
the system is attracted to the critical
point.
•Effect observed already for liquidgas nuclear transition
•Focusing causes broadening of
signal region - No need to run at
exactly Critical Point energy
Correlation lengths expected to reach at most 2 fm (Berdnikov, Rajagopal and Asakawa,
Nonaka): reduces signal amplitude, no sharp discontinuities
Finding evidence for a 1st order phase transition would
immediately narrow location of the critical point.
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Colliders are a great choice for E-scan
Acceptance
π
NA49
K
π
STAR
K
• Occupancy for collider detectors is
much less dependent on beam
energy
• Less problems with track merging,
charge sharing hits etc..
Acceptance for collider detectors is
totallyOdyniec
independent of beam energy
Grazyna
Better control of systematics
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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Luminosity is the key issue
Determined collision rate for
2008 9 GeV Au+Au test to be
Total Event Rate [Hz]
Image courtesy of
T.Satogata
~1Hz.
Rate can be increased by:
•factor 2 by adding more
3
bunches - only 56 used for tests
(max 120).
•factor 3-6 by operating with
higher charge in bunches.
•factor few by running in
continuous injection mode
Expect to reach γ3 rate even at
lowest energies
Grazyna Odyniec
•electron cooling in RHIC (?)
(not helpful at lower √s)
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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RHIC run 10 (2010)
(1) Large energy range accessible
(2) Collider geometry (acceptance won’t change with S, track density varies slowly)
(3) RHIC detectors well suited (large acceptance), tested & understood
STAR PAC 2007 Strawman proposal:
sNN [pft]
GeV [GeV/c]
mB
[MeV]
<BBC Rate>
[Hz]
Days/
Mevent
# events
# beam days
4.6 [9.6]
570
3
9
5M
45
6.3 [18.8]
470
7
4
5M
20
7.6 [27.9]
410
13
2
5M
10
8.8 [37.7]
380
20
1.5
5M
7.5
12 [71.0]
300
54
0.5
5M
2.5
18 [161]
220
>100
0.25
5M
1.5
28 [391]
150
>100
0.25
5M
1.5
Note: NA61 @ CERN (starting in 2010): 10, 20, 30, 40, 80, 158 GeV/c
Grazyna Odyniec
IV International Workshop on Correlations and Femtoscopy, Krakow, September 10-14, 2008
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