charles gale mcgill qm 2005 thermal photons and dileptons* why? how? theory low mass dileptons...
TRANSCRIPT
![Page 1: Charles Gale McGill QM 2005 Thermal Photons and Dileptons* Why? How? Theory Low mass dileptons Intermediate mass dileptons Photons: low and high(er) p](https://reader030.vdocuments.site/reader030/viewer/2022033101/5697bf921a28abf838c8f0ef/html5/thumbnails/1.jpg)
QM 2005 Charles Gale
McGill
Thermal Photons and Dileptons*
•Why? How? Theory•Low mass dileptons•Intermediate mass
dileptons•Photons: low and high(er)
pT photons
•EM signature of jets
((** Not an exhaustive review…) Not an exhaustive review…)
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QM 2005 Charles Gale
McGill
Why? The information carried by EM probes
3
3 3
1Im ( )
(2 ) 1Rd R g
kd k e
Emission rates:
[photons]
6 2
3 3 6 4
2 1 1Im ( )
(2 ) 1Rd R e
E E L kd p d p k e
[dileptons]
•The electromagnetic spectra will be direct probes of the in-medium photon self-energy•They are hard probes:
•EM signals as probes for hadronic tomography
EM 3%s
McLerran, Toimela (85), Weldon (90), Gale, Kapusta (91)
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QM 2005 Charles Gale
McGill
The current-current correlatorA model for the hadronic electromagnetic current: VMD
2 2 2e e eJ m m m
g g g
The current-field identity(J. J. Sakurai)
Im Im ImVMD
TT TJ J D Spectral density
The photon/dilepton signal can tell us about the in-medium
spectral densities of vector mesons. Rates need to be integrated
over the space-time history, with some dynamical model
3 3( , ) Im ( , )RdR
E E C p p k Td p d p
D
2 2 2 2 2 2( , )
L TP P k kk T
k m F k m G m k
D
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QM 2005 Charles Gale
McGill
What is expected (dileptons)• Low masses receive
significant contribution from radiative decays
• High masses dominated by DY
• Intermediate mass region interesting from QGP perspective, (Shuryak (78), Shor (89))
• Photons: similar story, but featureless spectra
• Experiments: DLS, Helios, TAPS, NA38, -50, WA98, CERES, PHENIX, HADES, NA60
DD
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QM 2005 Charles Gale
McGill
Expectations, part II
•Thermal QGP plasma radiation•Many-body, in-medium, effects on spectral densities
0
( , ) ( , ) 0L LV Ad p p
Weinberg (67)Kapusta, Shuryak (94)
+ other possibilities…
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QM 2005 Charles Gale
McGill
UrQMD
In-medium: what medium?
Phase-space trajectory goes through qualitatively different media
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QM 2005 Charles Gale
McGill
Low Masses:Vector Meson Spectral Densities:Hot Meson Gas
The spectral density is flattened
and broadened
Rapp, Gale (99)
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QM 2005 Charles Gale
McGill
Vector Meson Spectral Densities, II(adding baryons)
R. Rapp & J.Wambach, 1999
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QM 2005 Charles Gale
McGill
Vector spectral densities from data
c.m.c.m.
c.m.
1 exp( )1( )
12 4 sin2
P
apR a PR
a aRP
R R
q r if s W s
q sM s i
3c.m.
3( , ) 4 ( ) ( )
(2 )a a a
d k sE p n k f s
•Should hold near the mass-shell•Adler decoupling enforced
E. V.Shuryak, Nucl. Phys. A 533, 761 (1991); V. L. Eletsky and V. L.Ioffe, Phys. Lett. B 401, 327 (1997); Eletsky, Belkacem, Ellis, Kapusta,Phys. Rev. C 64, 035202 (2001)
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QM 2005 Charles Gale
McGill
Two approaches:
•Rates are also constrained by nuclear photoabsorption data•Lagrangians are constrained by hadronic phenomenology•Mass shifts & broadening are related by dispersion relations
Rapp & WambachEletsky, Ioffe, Kapusta
(Giessen, Frankfurt, Munich)
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QM 2005 Charles Gale
McGill
Fold in With a Dynamical Evolution Model
Huovinen, Belkacem, Ellis, and Kapusta (02)
What’s new?
Rapp, Brown-Rho
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QM 2005 Charles Gale
McGill
e+e- mass spectrum: comparison to the models
calculation by R.Rapp using Rapp/Wambach medium modification of rho spectral function
calculation by R.Rapp using Brown-Rho scaling
B. Kämpfer, thermal emission
...added to the cocktail.
in the 0.8 < m < 0.98 GeV region:Brown-Rho curve: 2/n = 2.4the other two curves: 2/n ~ 0.3
Sergey Yurevich (CERES)
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QM 2005 Charles Gale
McGill
NA60 Comparison of data to RW, BR and NA60 Comparison of data to RW, BR and Vacuum Vacuum
pT dependence
Sanja Damjanovic
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QM 2005 Charles Gale
McGill
NA60 Comparison of data to RW, BR and NA60 Comparison of data to RW, BR and Vacuum Vacuum
•Linear scale!!!Linear scale!!!•Quality of data enables a preciseQuality of data enables a precise determination of the spectraldetermination of the spectral properties.properties.•The beginning of a new era…The beginning of a new era…
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QM 2005 Charles Gale
McGill
The intermediate mass sector: some background
• Direct connection to Hard Probes• Off-shell effects are potentially important for
effective hadronic interactions Gao & Gale, PRC 57, 254 (1998)
• A lot of data already exists!
DD_
DY
NA50Pb-Pb 158 GeV
central collisions
charm DY
A. Shor, PLB 233, 231 (1989)
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QM 2005 Charles Gale
McGill
e+ e- Data: A Wealth of Information
• OLYA
• CMD
• DM-1(2)
• ARGUS
• M3N
•
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QM 2005 Charles Gale
McGill
A larger comparison
• Agreement across theoretical
models
• Those channels are absent
from the spectral densities used in comparisons with CERES and the new NA60 data.
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QM 2005 Charles Gale
McGill
Li and Gale, PRC (1998)
Intermediate mass data
A. L. S. Angelis et al. (Helios 3), Eur. Phys. J. (1998)
R. Rapp & E. Shuryak, PLB (2000)
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QM 2005 Charles Gale
McGill
NA50 Data (cont’nd)
I. Kvasnikova, C. Gale, and
D. K. Srivastava, PRC 2002
•In agreement with multiplicity dependence•Includes detector acceptance & efficiency
(O. Drapier, NA50)
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QM 2005 Charles Gale
McGill
NA60 IMR analysis: weighted offset fits (R. Shahoyan)
or
Fix Charm contribution to “world average” value
Fix Charm contribution to NA50 p-A expected value
Fit always requires ~2 times more Prompts
1
Extract prompts by fixing Open Charm contribution
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QM 2005 Charles Gale
McGill
Low and Intermediate masses: partial summary
• Thermal sources shine in the LMR and IMR. No great sensitivity to the QGP
• The data is precise enough to consider a differentiation of space-time models
• DY? At low M, medium-enhanced multiple parton scatterings might be large (Qiu, Zhang (02), Fries, Schaefer, Stein, Mueller (00). pA measurement.)
2 21 ( )NNAB
AB
ddAB R Q
dQ dQ
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QM 2005 Charles Gale
McGill
(Theory) Homework
• Unite (standardize?) space-time modeling [nD hydro, fireballs, transport approaches…]. Rapidity dependence of photon signal: a probe of stopping (Renk, PRC (05))
• The power of the data is only fully realized if a general-purpose acceptance filter exists.
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QM 2005 Charles Gale
McGill
Electromagnetic radiation from QCD
First approaches
McLerran, Toimela (1986); Kajantie, Kapusta, McLerran, Mekjian (1986)Baier, Pire, Schiff (1988); Altherr, Ruuskanen (1992)
Rates diverge: 2ln( / 0)s T q
HTLresummation
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QM 2005 Charles Gale
McGill
• HTL program: Klimov (1981), Weldon (1982)
Braaten & Pisarski (1990); Frenkel & Taylor (1990)
2Im lnR
th
T
m gT
Kapusta, Lichard, Seibert (1991)Baier, Nakkagawa, Niegawa, Redlich (1992)
Going to two loops: Aurenche, Kobes, Gelis, Petitgirard (1996) Aurenche, Gelis, Kobes, Zaraket (1998)
Co-linear singularities: 22
2s sth
T
m
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QM 2005 Charles Gale
McGill
Singularities can be re-summed
Arnold, Moore, and Yaffe
JHEP 12, 009 (2001); JHEP 11, 057 (2001)
• Incorporates LPM
• Complete leading order in αs
• Inclusive treatment of collinear enhancement, photon and gluon
emission
Can be expressed in terms of the solution to a linear integral equation
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QM 2005 Charles Gale
McGill
How big (small) is this?
Turbide, Rapp & Gale PRC (2004)
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QM 2005 Charles Gale
McGill
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QM 2005 Charles Gale
McGill
Azimuthal correlation– Shows the absence of “away-side” jet.
Pedestal&flow subtracted
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QM 2005 Charles Gale
McGill
Quenching = Jet-Plasma interaction. Does this have an EM signature?
qg q
The plasma mediates a jet-photon conversion
Fries, Mueller & Srivastava, PRL 90, 132301 (2003)
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QM 2005 Charles Gale
McGill
Photon sources• Hard direct photons
• EM bremsstrahlung
• Thermal photons from hot medium
• Jet-photon conversion
• Jet in-medium bremsstrahlung
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QM 2005 Charles Gale
McGill
Energy loss in the jet-photon conversion? Jet bremsstrahlung?
Use the approach of Arnold, Moore, and Yaffe
JHEP 12, 009 (2001); JHEP 11, 057 (2001)
• Incorporates LPM
• Complete leading order in S
• Inclusive treatment of collinear enhancement, photon and gluon
emission
Can be expressed in terms of the solution to a linear integral equation
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QM 2005 Charles Gale
McGill
Time-evolution of quark distribution
The entiredistribution isevolved by the collision Kernel(s)Of the FP equation
Turbide, Gale, Jeon, and Moore (2004)
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QM 2005 Charles Gale
McGill
With the new (preliminary) PHENIX data
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QM 2005 Charles Gale
McGill
Photons: establishing a baseline
Aurenche et al., NPB 286, 553 (1987)Consistent with Gordon & Vogelsang
(preliminary)
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QM 2005 Charles Gale
McGill
Direct in d+Au
• p+p and d+Au spectra compared to NLO pQCD
• ratio to NLO pQCD• consistent with 1• No indication for
nuclear effects
2
Poster H. Torii
Poster D. Peressounko
(S. Bathe)
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QM 2005 Charles Gale
McGill
RHIC jet-plasma photons
With E loss
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QM 2005 Charles Gale
McGill
RHIC Au Au data
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QM 2005 Charles Gale
McGill
New (preliminary) PHENIX Data(Bathe, Buesching)
*
*direct direct
inclusive inclusive
4 3 *
2 3 2 33
d d
dM d q M d q
*
*direct
direct inclusiveinclusive
÷
÷÷
0-3
0
90-1
40
140-2
00 M
eV
200-3
00
Rdata
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QM 2005 Charles Gale
McGill
New (preliminary) PHENIX Data(Bathe, Buesching)
A prediction: all source
Sizes fixed prio
r to QM
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QM 2005 Charles Gale
McGill
QM05 Stefan Bathe 31
The Spectrum
Compare to thermal + pQCD• data consistent with
thermal + pQCD
Compare to thermal model
• data above thermal at high pT
• D. d’Enterria, D. Perresounko
• nucl-th/0503054
Compare to NLO pQCD
• excess above pQCD
• L.E.Gordon and W. Vogelsang
• Phys. Rev. D48, 3136 (1993)
2+1 hydroT0
ave=360 MeV(T0max=570 MeV)
0=0.15 fm/ c
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QM 2005 Charles Gale
McGill
Other signature of jet-photon conversion?
• Jet-plasma photons will come out of the
hadron-blind region. “Optical” v2 < 0
1 2 cos2 n
nT T T T
dN dNv n
p dp d p dp
Turbide, Gale, Fries (05)
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QM 2005 Charles Gale
McGill
If photons can be detected in coincidence with hadronsThe jet-plasma photons can be easier to isolate (Cole)
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QM 2005 Charles Gale
McGill
Jet-plasma interactions: measurable EM signatures!
• RHIC:– Jet-plasma interaction is a large source of photons up to
pT ~ 6 GeV. – Conclusions include energy-loss considerations– True also in the dilepton channel: signal competes with
Drell-Yan (NLO)
• LHC:– Jet-plasma photon signal is important– Large mass lepton pairs dominate over Drell-Yan
emission.
Towards a consistent treatment of jets & EM radiation
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QM 2005 Charles Gale
McGill
Summary, Conclusions, Open Issues• Low and mass dileptons: NA60 data can distinguish
between models• IMR: More homework to be done (Higher twist…)• Space-time evolution models• RHIC: There are measurable electromagnetic
signatures of jet-plasma interaction: those constitute complementary observables to signal the existence of conditions suitable for jet-quenching
• Photon v2, a revealing probe • RHIC dileptons: systematic errors still too large to
permit source identification (A. Toia, PHENIX)• EM radiation and hard probes: the start of a
beautiful friendship…
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QM 2005 Charles Gale
McGill
Collaborators:
•Simon Turbide, McGill University
•Rainer Fries, University of Minnesota
•R. Rapp, Texas A&M
•Dinesh Srivastava, VECC, Calcutta