Physics Revealed at Intermediate p T Rudolph C. Hwa University of Oregon Quark Matter 2008 Jaipur,...
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Physics Revealed at Intermediate pT
Rudolph C. HwaUniversity of Oregon
Quark Matter 2008
Jaipur, India
February 6, 2008
2
pT2 6
low intermediate
high
pQCDhydro
no rigorous theoretical framework
But that is where the action is, albeit experimental.
What can we learn from the abundant data?
3
OverviewSingle particle distributionpT
Two particle correlation data
Near side Away side
Ridge Jet Double bump
Three particle correlation
(1 or 2 triggers)
Auto-correlation
(no trigger)
RCPdAu
decrease with
Huge p/ at =3.2
B/M ~ 1RCPp > RCP
(dAu)
RCPΛ,Ξ > RCP
K ,φ
v2
nq
ETnq
⎛
⎝⎜
⎞
⎠⎟ univers
alquark number scaling&
breaking
4
OverviewSingle particle distributionpT
RCPdAu
decrease with
Huge p/ at =3.2
Two particle correlation data
Near side Away side
Ridge Jet Double bump
Three particle correlation
(1 or 2 triggers)
Auto-correlation
(no trigger)
B/M ~ 1RCPp > RCP
(dAu)
RCPΛ,Ξ > RCP
K ,φ
v2
nq
ETnq
⎛
⎝⎜
⎞
⎠⎟ univers
alquark number scaling&
breaking
5
p T
R
JS
Recombination at Intermediate
pT
partons
hadronsReco
What partons?
Medium effects
u, d, sg converted
to qc,b,t primordial
6
pT
Λ/K
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STAR4
3
2
1
0
in recombination/coalescence model (Reco)
Baryon/Meson ratios
“Baryon anomaly”On the contrary, high B/M ratio is a signature of Reco. Baryons need less quark momenta than
mesons.
implies that fragmentation is normal.
7
Elliptic flow
v2M (pT )=v2
T q1( ) + v2T q2( ) v2
B (pT )=v2T q1( ) + v2
T q2( ) + v2T q3( )
M: TT + TS + SS B: TTT + TTS + TSS + SSS
Ifq1 =q2 =q3 =pT / 3
M:
B:
q1 =q2 =pT / 2 then
v2M
2
pT2
⎛⎝⎜
⎞⎠⎟;
v2B
3pT
3⎛⎝⎜
⎞⎠⎟
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0.1
0.05
v2 / nq
pT → KET
Molnar & Voloshin, PRL91,(2003)
quark number scaling(QNS)
a property of naïve recombination
8
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RH&CBY,0801.2183
STAR, PRC75,054906(07)
minbias
However, at larger KET
M: TT + TS + SS B: TTT + TTS + TSS + SSS
v2M (pT )≈v2
T q1( ) + v2S q2( ) v2
B (pT )≈v2T q1( ) + v2
T q2( ) + v2S q3( )
q1 ≠q2v2T ≠v2
S
v2M
2
pT2
⎛⎝⎜
⎞⎠⎟≠
v2B
3pT
3⎛⎝⎜
⎞⎠⎟
QNS is broken, but hadronization is still by recombination
pΛ
K
9
BRAHMS, nucl-ex/0602018Au+Au at 62.4 GeV Forward production
TT
TS
TTT
xF = 0.9
xF = 0.8
xF = 1.0
Shower partons are suppressed at the kinematical boundaryFew
antiquarks at large
mainly p produced
10
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BRAHMS(preliminary)
Comments at the end, if asked.
11
Ridgeology
Putschke, QM06
J+R
R
J
Correlation on the near side
STAR
ridge R Jet J
Properties of Ridge YieldDependences on Npart, pT,trig, pT,assoc, trigger B/M ratio in the ridge
12
Jet+Ridge ()
Jet ()
Jet)
Putschke, QM06
R
1. Dependence on Nparton pT,trig2.
pt,assoc. > 2 GeVSTAR preliminary
Ridge is correlated to jet production. Surface bias of jet ridge is due to medium effect near the surface
Medium effect near surface
Ridges observed at any pT,trig
Ridge yield 0as Npart 0
depends on medium
13
3. Dependence on trigger
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STAR (preliminary)
A. Feng
20-60%, 3-4:1.5-2
| 1RP
s
T
Ridge develops by radial flow near the jet axis
Mismatch of T and the direction of radial expansion.
has more ridge yield than
Ridge yield decreases with increasing s
Comments at the end, if asked.
14
Ridge
Putschke, QM06
4. Dependence on pT,assoc
Yet Ridge is correlated to jet production; thermal does not mean no correlation.
Ridge is from thermal source enhanced by energy loss by semi-hard partons traversing the medium.
Ridge is exponential in pT,assoc slope independent of pT,trigExponential behavior
implies thermal source.
STAR
15
5. B/M ratio in the ridge
Ridge hadrons are formed by recombination
Large B/M
Bielcikova, WWND07
K
Λ+Λ
Λ + ΛK
: 2
pt,assoc. > 2 GeV
Au+Au 0-10%
Putschke, QM06p
2-4p(R) / p(J )
(R) / (J )
STAR
16
Medium effect near surface coordinated with radial flow
SS
trigger
TT ridge (R)
associated particles
These wings are useful to identify the RidgeBut of interest below is
mainly the distribution.
Ridge is from enhanced thermal source caused by semi-hard scattering.
Recombination of partons in the ridge
ST
peak (J)
17
What are the consequences of Ridgeology?
1. Jet correlation at low and intermediate pT
2. Effect on single particle spectra
3. Effect on elliptic flow
18
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PHENIX
2.5<pT,trig<4 GeV/c
1.8<pT,assoc<2.5
PH
EN
IX,
PLB
64
9,3
59
(07
)Peak is referred to as jet
1. Jet correlation at intermediate pT
Not seeing the ridge does not mean that it is not there.
J
R
Correlation in J is different from correlation in R
Does not see the ridge
||<0.35
19
STAR preliminary
Jet
STAR preliminary
Jet + RidgePHENIX, PLB 649,359(07)
SS TS
TT
Not un-correlated. Ridge would not be there without semi-hard scattering.
How can intermediate-pt Jet yield be independent of centrality?
0.35
20
PHENIX data cannot be properly understood without taking Ridge into account
2.5<pT,trig<4.0 GeV/c
PHENIX 0712.3033
J
R
: 1 2
2p(R) / p(J )
(R) / (J )
pt,assoc. > 2 GeV
Au+Au 0-10%
Putschke, QM06p
STAR
21
2. Effect of Ridge on single-particle spectra
Semi-hard scattering at kT~2-3 GeV/c is pervasive.
Ridges are present with or without triggers.
STAR, PRC 73, 064907 (2006)
Auto-correlation without triggers.
0.15<pt<2.0 GeV/c, ||<1.3, at 130 GeV
22
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Bulk+Ridge
TT
Semi-hard partons generating ridge
TS
Fragments from hard partons
SS
(fragmentation)
T includes enhanced thermal partons --- Ridge
23
sss
How can we see better the TT component?
Remove the TS and SS components, if possible.
production: Au+Au + anything
(sss) s quark suppressed in shower
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pt
dN
/ptd
pt
(log
sc
ale
)
TTS
TTT
uud
Exposes the long exponential behavior in production
24
spectrum is exponential (thermal)
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QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.Chiu & Hwa, PRC76,024904(2007)
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How can it have correlated partners? --- the puzzle.
STAR
Resolution: Both and its associated hadrons are in the Ridge.
Prediction: there is no peak (J) in the distribution --- only R
R only
25
= cos-1(b/2R)
If the semi-hard jets are soft enough, there are many of them, all restricted to || < .
A semi-hard scattering near the surface gives rise to a jet, whose direction, on average, is normal to the surface.
Initial configuration
There is a layer of ridges at the surface without triggers.
3. Effect of Ridge on elliptic flow
26
In momentum space
B
B+R
dN
pTdpTdφ=B(pT ) + R(pT )Θ(φ)
v2 (pT )= cos2φ =sin2(b)
B(pT ) / R(pT ) + 2(b)
Relate ridgeology to v2 Hwa, 0708.1508
Use data on B(pT) and R(pT)
bow tie region
27
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Elliptic flow at low pT
v2 driven by Ridge
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Made no assumption about rapid thermalization.
28
Elliptic flow at intermediate pT
v2 dominated by TS recombination
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Hwa & CB Yang, 0801.2183
29
Away-side correlation
PHENIX 0705.3238 & .3060
Double-bump first observed by STAR
STAR, PRL 95, 152301 (05)
has been studied extensively --- experimentally and theoretically.
Mach conegluon radiation
Cherenkov radiation deflected jets …
Is there any connection between the double bumps and ridge w/o peak(J)?
2D
mild dependence of D on pt,assoc favors
30
Possible relationship between ridge and bump (Renk, Jia)
Near side Away side
Ridge Bump
Generated by semi-hard scattering
Mach cone, deflected jet,--- due to recoil of semi-hard parton
Due to recombination of enhanced thermal partons
What is partonic structure of the Mach-shock-wave?
Exponential pt,assoc Distribution in pt,assoc ?
Large B/M ratio B/M ratio is also large.
31
Papers submitted to the session on: “Response of Medium to Jets”
Experimental
Netrakanti (STAR)Wenger (PHOBOS)McCumber (PHENIX)Suarez (STAR)Feng (STAR)Adare (PHENIX)Barannikova (STAR)Catu (STAR)Daugherity (STAR)Pei (PHENIX)Haag (STAR)Szuba (NA49)G. Ma (STAR)Wang (STAR)Noferini (ALICE)Chetluru (UIC)
TheoreticalMajumder
C.Y.Wong
Gavin
Mizukawa, Hirano, Isse, Nara, Ohnishi
Pantuev
Lokhtin, Petrushanko, Snigirev, Sarycheva
Levai, Barnafoldi, Fai
Betz, Gyulassy, Rischke, Stoecker, Torrieri
Molnar
Asakawa, Mueller, Neufeld, Nonaka, Puppert
Schenke, Dumitru, Nara, Strickland
BauchlePlenary session X Ulery
Jia
32
On to LHCMany predictions made (see arXiv:0711.0974)
Those with existing codes can make extrapolations.
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Eskola et al (EKRT model)
Is there new physics that cannot be obtained by extrapolation?
SS
hard parton
hadron
energy loss
p/>>1
Density of semi-hard partons is high at LHC.
SS
semi-hard partons
SS or SSS recombination to form or p.
33
What is the bulk background at LHC?
Since SS and SSS recombination of semi-hard partons are uncorrelated, they occur in mixed events.
Thus they belong to the background.
But those partons are not thermal, not in hydro.
Can Ridge be identified in association with a high pT trigger --- pT,trig > 20 GeV/c?
The ridge may not stand out among the background that consists of TT, TS, SS, TTT, TTS, TSS, SSS hadrons.
Physics at intermediate pT at LHC may be very different from that at RHIC ----- cannot be obtained by extrapolation.
So there is a mismatch between bg and hydro.
34
Summary
p T
R
JS
Physics revealed by phenomena observed at intermediate pT
soft & semi-hard partons
35
T S
Large B/M ratio
QN scaling and breaking
Exponential pT at large
v2
Ridge
Jet
Double bump
Reco at LHC
36
Backup slides
37
At large xF, proton can be formed by leading quarks from different nucleons. dxi
xii=1
3
∏⎛
⎝⎜⎞
⎠⎟∫ Fνu(x1)Fν
u(x2 )Fνd(x3)Rp(x1,x2 ,x3,x)
p x can exceed 1
Antiquarks at low xi are affected by the regeneration of that depends on .qq
Pions are suppressed due to the lack of antiquarks at large xi.
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BRAHMS (preliminary)
should be larger less degradation more protons less increase of pions larger p/ ratio
~0.75 Hwa & CBYang, PRC76,104901(2007)
momenta degraded survival probability
“baryon stopping”
Forward production
38
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STAR (preliminary)
A. Feng
20-60%, 3-4:1.5-2
| 1
3. Dependence on trigger
RP
s
T
Ridge develops by radial flow near the jet axis
Ridge yield decreases with increasing sMismatch of T and the direction of radial expansion.
has more ridge yield than