after the first discoveries at rhic
DESCRIPTION
After the First Discoveries at RHIC. Hideki Hamagaki Center for Nuclear Study (CNS) University of Tokyo. Primary Goal of Study with High-Energy Heavy-Ion Collisions. Understand hadronic matter under extreme conditions Basic QCD property; confinement & chiral symmetry - PowerPoint PPT PresentationTRANSCRIPT
After the First Discoveries at RHIC
Hideki HamagakiCenter for Nuclear Study (CNS)
University of Tokyo
2008/04/26 After the First Discoveries at RHIC 2
Our knowledge of QCD matter has been limited to the region at T ~ 0 and 0
~ 1
Our knowledge of QCD matter has been limited to the region at T ~ 0 and 0
~ 1
Primary Goal of Study with High-Energy Heavy-Ion Collisions
•Understand hadronic matter under extreme conditions−Basic QCD property; confinement & chiral symmetry−Relevance to Early universe
High-energy heavy-ion collision provides extreme conditions
• Accelerators• Cosmic rays
High-energy heavy-ion collision provides extreme conditions
• Accelerators• Cosmic rays
Phys.Rev. D72 (2005) 034004
2008/04/26 After the First Discoveries at RHIC 3
Accelerators
1970 1980 1990 2000 2010 2020
LBL Bevalac1974~1993ECM=2GeV
BNL AGS1986~ECM=5GeV
CERN SPS1986~ECM=17GeV
BNL RHIC2000~ECM=200GeV
CERN LHC2009~ECM=5500GeV
(GeV)
1000
100
10
1
2008/04/26 After the First Discoveries at RHIC 4
Gross Features of High-Energy Heavy-Ion Collisions
• nuclei = Lorentz contracted disks (d~2R/)• participant-spectator picture works well
– classical trajectory– participant region is geometrically determined
• Specification of ‘Centrality’ is a Must to characterize the collisions Spectator -- beam fragment
Spectator -- target fragment
Participant
2008/04/26 After the First Discoveries at RHIC 5
Initial Processes in High-Energy Heavy-Ion Collisions
• Collisions in high energy– between partons (quarks and gluons) in t
he colliding nucleons
• Two competing processes in the initial stage– hard process
• large-Q2 scattering between partons• pQCD calculation• becomes prominent in high energy
– soft process• dominant in the low-energy collisions• multi-particle production with low-pT• non-perturbative
2008/04/26 After the First Discoveries at RHIC 6
Characteristics of Hard Process
• jet & single photon production• production yield; proportional to number of binary collisions
between nucleons (<- Glauber model)
– with known nuclear effects• Cronin effect• Nuclear shadowing effect
• Nuclear modification factor
pp
coll
AAdp
NdEN
dp
NdE
3
3
3
3Color Glass Condensate (CGC) becomes important at high gluon density; central subject at LHC)
TTppcoll
TTAATAA dppdNN
dppdNpR
2008/04/26 After the First Discoveries at RHIC 7
RHIC and the Experiments
• New York State, USA• Long Island• Brookhaven National Lab.
BRAHMS, PHOBOS • Small collaborations (~100)• Large but small coverage
STAR , PHENIX • Big collaborations (~500)• Small but large coverage
RHIC• 2 independent rings• 3.83 km circumference• CMS energy
– Au + Au: up to 200 A GeV– p + p: 500 GeV (polarized)
• two programs: Heavy Ion and SPIN
2008/04/26 After the First Discoveries at RHIC 8
Japanese group in PHENIX
• Two Japanese groups have been participating in the PHENIX experiment
– Heavy ion: Japan-US collaboration in High Energy Physics– SPIN: RIKEN SPIN project
2008/04/26 After the First Discoveries at RHIC 9
RHIC Physics Runs• RUN-1: June ~ Sep.4, 2000
Au+Au: (sNN)1/2 = 132 GeV• RUN-2: Aug. 2001 ~ Jan. 2002
Au+Au, p+p: (sNN)1/2 = 200 GeV• RUN-3: Jan. 2003 ~ May 2004
d+Au, p+p : (sNN)1/2 = 200 GeV• RUN-4: Jan. 2004 ~ May 2004
Au+Au, p+p: (sNN)1/2 = 200, 63 GeV• RUN-5: Jan. 2005 ~May 2005
Cu+Cu: (sNN)1/2 = 200, 63 GeV
p+p: (s)1/2 = 200 GeV• RUN-6: Feb. 2006 ~June 2006
p+p: (s)1/2 = 200 GeV, 63 GeV• RUN-7: Mar. 2007~June 2007
Au+Au, p+p: (sNN)1/2 = 200 GeV• RUN-8: Nov.29 2007~Mar. 2008
d+Au, p+p: (sNN)1/2 = 200 GeV,...
First Au + Au collisions at √sNN = 56 GeVJune 12, 2000
2008/04/26 After the First Discoveries at RHIC 10
The First Major Discovery at RHIC• Strong suppression of pion yie
ld at high-pT in central Au+Au collisions– most high-pT pions are from jet f
ragmentation
• Strong jet energy loss >>> Evidence of formation of hi
gh-density matter
Energy loss in plasma
p p
Hot dense medium
TTppcoll
TTAATAA dppdNN
dppdNpR
2008/04/26 After the First Discoveries at RHIC 11
The Second Major Discovery at RHIC
• Large anisotropy in angular distribution in azimuth – hydro-dynamical behavior ~ consistent with hydro with
no viscosity => perfect liquid
React
ion
plan
e
Spatial anisotropy --->>> Momentum anisotropy
2008/04/26 After the First Discoveries at RHIC 12
Top Story 2005
According to American Institut of Physics, the top physics story in 2005 was the discovery of the perfect liquid
2008/04/26 After the First Discoveries at RHIC 13
Where has all the energy gone?
• Collective excitation, analogous to shock wave? --- having been sought since BEVALAC era
4 < pT,trig< 6 GeV/c, 2< pT,assoc< pT,trig
STAR, PRL 90 (2003) 082302
Leadinghadrons
Medium
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Sideward Particle Emission
• Clear change from back-to-back correlation to sideward correlation with increase of centrality
PHENIX preliminary
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12
1
3
0
Event by event deflection of jets
1
3
12
0
Cone like structure in each event
Origin of Sideward Peak
• Jet deflection• Cone-like structure
3-particle correlation data by STAR indicates cone-like particle emission
12
1
3
2008/04/26 After the First Discoveries at RHIC 16
3-Particle Correlations at PHENIX
*
Cone Jet
Deflected Jet
Normal Jet
(medium excitation)
(scattered jet axis)
(unmodified)
PHENIX Preliminary
*
High pT (1)
Assoc. pTs (2,3)
Same Side
Away Side
*
*12
*13
* _=
*12
=
2008/04/26 After the First Discoveries at RHIC 17
Trying to Reproduce Mach Cone in Hot QCD Matter
Relevant dynamical quantities:• g2Q projectile color charge• mD screening mass• cs
2 (= dp/d) sound speed– p = /3 -> cs
2 = 1/3
• s = 4/3sT: attentuation length– s = (4/3)(1/4)(1/T) = 1/3T
QM08: B. Mueller, M. Asakawa, R.B. Neufeld, C. Nonaka , J. Ruppert
2008/04/26 After the First Discoveries at RHIC 18
(( 44
• Conjectured lower quantum limit – Derived first in (P. Kovtun, D.T. Son, A.O. Starinets, Phys. Rev. Lett.
94:111601, 2005) – AdS/CFT (Anti de Sitter space / Conformal Field Theory) correspond
ence (J. Maldacena: Adv. Theor. Math. Phys. 2, 231, 1998)
Perfect Fluids?
4
s
• “ordinary” fluids– water (at normal conditions)
• /s ~ 380 ћ/4– helium (at point)
• /s ~ 9 ћ/4
• Need observables that are sensitive to shear stress• Damping (flow, fluctuations, heavy quark motion) ~ /s
2008/04/26 After the First Discoveries at RHIC 19
Heavy Flavor• Production of charm (and bottom) is a
hard process– leading order at low x = ’’gluon fusion’’– Ncoll scaling should hold, with known n
uclear effects of nuclear shadowing and kT broadening
• Interaction is considered to be weaker– gluon bremsstrahlung is suppressed at
forward angles (dead cone effect); < mQ/EQ
• How to measure– “exclusive” is favorable, but difficult in h
eavy ion collisions– semi-leptonic decay measure electro
ns/muons
22QQ
2 ])/([
1
Em
2008/04/26 After the First Discoveries at RHIC 20
In Au+Au Collisions at sNN = 200 GeVPhys.Rev.Lett.98:172301,2007
• Binary scaling of total e± yield from heavy-flavor decays– Expected from heavy-quark production via hard scattering
• High pT e± suppression increasing with centrality– Energy loss
2008/04/26 After the First Discoveries at RHIC 21
RAA and v2 of non-photonic Electrons
• At pT > 4 GeV/c – b/(c+b) > 0.5– RAA continues dropping– (New) v2 result stays high
-> bottom seems to interact strongly as charm
... need further study to make it quantitative
Large yield suppression and significant v2
2008/04/26 After the First Discoveries at RHIC 22
Viscosity from Heavy Flavor Data• Strongly suppressed & significan
t v2 implies high density & small diffusion coefficient
• DHQx2T ~ 4-6– Rapp & van Hees (PRC 71,
034907 (2005))
• D ~ 6 /(e+P)– Moore & Teaney (PRC 71, 064904
(2005))
• e+P = Ts at B = 0 --> /s = (1.3-2.0)/4= Very close to conjectured lim
itPHENIX : PRL98, 172301 (2007)
2008/04/26 After the First Discoveries at RHIC 23
4/)8.30.1(/ s
S. Gavin and M. Abdel-Aziz: PRL 97:162302, 2006
pTfluctuations STAR
Compilation of Estimates 4/)2.12.01.1(/ s
R. Lacey et al.: PRL 98:092301, 2007
v2 PHENIX & STAR
4/)4.24.1(/ s
H.-J. Drescher et al.: arXiv:0704.3553
v2 PHOBOS
conjectured quantum limit
• Estimates of /s based on flow and fluctuation data– Indicate small value as well– Close to conjectured limit– Significantly below /s of heliu
m (s ~ 9)
2008/04/26 After the First Discoveries at RHIC 24
Summary
• First major discoveries at RHIC– Parton energy loss -- high density matter– Hydrodynamical flow -- perfect liquid(?)
• Many interesting results afterward– Mach cone-like structure -- shock wave?– Energy-loss and thermalization of heavy flavor– Anomalous baryon/meson ratio -- recombination pictur
e– Thermal photons in p-p & HI collisions– Low-mass lepton-pairs in HI collisions– Charm to bottom ratio– J/ systematics
2008/04/26 After the First Discoveries at RHIC 25
Outlook
• Good d + Au run in RUN8 -- we will soon have high-statistics results for cold nuclear matter effect
• Au + Au run for low-mass e+e- pairs with HBD (PHENIX)
• Charm and bottom identification with VTX silicon tracker
• Energy scan (to lower energy) for critical point search
• SPIN PROGRAM -- G and W
Backups
2008/04/26 After the First Discoveries at RHIC 27
CMS energy
Initial energy density
Why do we need Higher Energy?
With collisions at higher energy• High initial energy density
– Large margin at RHIC and LHC– Longer duration time of QGP
• Description of space-time evolution becomes simpler– Higher particle density shorter mean free path
• chemical & thermal equilibrium– Hydro-dynamical description may
become possible comparison with models
becomes reliable• Availability of hard probes
– jet & hard photon – heavy flavor
2008/04/26 After the First Discoveries at RHIC 28
Nuclear Effects
• Cronin effectpA(pT) = pp(pT) A(p
T)
(pT) > 1 in the high pT
– small-angle multiple scattering of partons in the initial stage
– kT broadening
• Nuclear shadowing– modification of parton
structure function in case of nuclei
– large depletion in small x
2008/04/26 After the First Discoveries at RHIC 29
Soft Process• non-perturbative phenomenological
description• string model
– confinement potential x with string tension ~ 1 GeV/fm
• Bjorken’s picture– Boost invariance space-time
evolution is determined by proper time
• string trajectory = hyperbola
– string fragmentation at a certain proper time particle production
z
t
0
mT
r02A2/30
dNdy
1r0
2A2/30
dET
dy