Upload
zareh
View
29
Download
0
Embed Size (px)
DESCRIPTION
Heavy-Quark Diffusion in the Primordial Quark-Gluon Liquid. Vector Mesons in Medium and Dileptons in Heavy-Ion Collisions. Ralf Rapp Cyclotron Institute + Physics Department Texas A&M University College Station, USA Strong Interaction Seminar TU M ünchen , 26.10.09. - PowerPoint PPT Presentation
Citation preview
Heavy-Quark Diffusion
in the Primordial Quark-Gluon Liquid
Vector Mesons in Medium
and Dileptons in Heavy-Ion Collisions
Ralf Rapp Cyclotron Institute + Physics Department
Texas A&M University College Station, USA
Strong Interaction SeminarTU München, 26.10.09
1.) Intro-I: Probing Strongly Interacting Matter
• Electromagnetic Probes: penetrating: EM >> Rnuc
• Equilibrium: EM spectral function Im EM(q0,q;B,T)
Information via EM Spectral Function: • degrees of freedom (parton vs. hadron)• transport properties (EM conductivity, susceptibility)• relation to order parameters (chiral symmetry)• measure of temperature
1.2) Intro-IIa: Low-Mass Dileptons at CERN-SPS
CERES/NA45 [2000]
mee [GeV]
• strong excess around M ≈ 0.5GeV (and M > 1GeV ) • little excess in region
NA60 [2005]
1.2) Intro-IIb: Low-Mass Dileptons SIS + RHIC
HADES [2008]
• awaiting larger system sizes …
PHENIX [2008]
mee [GeV]
• very large low-mass excess• awaiting HBD results (run-10) …
1.) Introduction
2.) Chiral Symmetry + Vector Mesons EM Emission and Vector Mesons Chiral Symmetry Breaking and a1 Meson in Medium
3.) Dilepton Spectra in A-A and -A Thermal Emission and NA60 (SPS) Photoproduction and CLAS (JLab)
4.) Conclusions
Outline
2.1 Thermal Electromagnetic Emission
Tiqx )](j),x(j[)x(exdi)q(Π 0emem0
4em
EM Current-Current Correlation Function:
e+
e-
γ
)T(fMqd
dR Bee23
2em
4
)T(fqd
dRq B
2em
30
Im Πem(M,q)
Im Πem(q0=q)
Thermal Dilepton and Photon Production Rates:
Imem ~ [ImD+ ImD/10 + ImD/5]Low Mass: -mesondominated
But: “Higgs” Mechanism in Strong Interactions:qq attraction “Bose” condensate fills QCD vacuum
Spontaneous Chiral Symmetry Breaking
2.2 Chiral Symmetry + QCD Vacuum
)m( d,u 0QCD L : isospin + “chiral” (left/right-handed) invariant
350000 fm|qqqq||qq| LRRL
>
>
>
>qLqR
qL-qR
--
Profound Consequences:• effective quark-mass: ↔ mass generation
• massless Goldstone bosons 0,± , pion pole-strength f= 93MeV
• “chiral partners” split, M ≈ 0.5GeV:
00 |qq|m*q
JP=0± 1± 1/2±
• Weinberg Sum Rule(s)
2.3 Hadron Spectra + Chiral Symm. Breaking
Axial-/Vector Correlators
)Im(Ims
dsf IA
IV
112
pQCD cont.
“Data”: lattice [Bowman et al ‘02] Theory: Instanton Model [Diakonov+Petrov; Shuryak ‘85]
Constituent Quark Mass
• chiral breaking: |q2| ≤ 1 GeV2
• Gellmann Oakes Renner:
m2 f
2 = mq ‹0|qq|0›-
2.4 Sum Rules and Order Parameters
)Im(ImsdsI IA
IV
nn
11
210
21
222 0
31 q)q(αcI,I,fI,FrfI sπAππ
[Weinberg ’67, Das et al ’67, Kapusta+Shuryak ‘93]
• QCD-SRs
[Hatsuda+Lee ’91, Asakawa+Ko ’92, Klingl et al ’97, Leupold et al ’98, Kämpfer et al ‘03, Ruppert et al ’05, Kwon et al ‘08]
Promising synergy of lQCD and effective models
• Weinberg-SRs: moments VectorAxialvector
sQ
)s(Ims
dsQ
)Q(Π
20
2
2
...
Q
)qq(C
Q
GQ)()Q( ss
s 6
2
4
22
2
2
22
3ln1
81
>>
B*,a1,K1
...
N,,K…
2.5 -Meson in Medium: Hadronic Interactions
D(M,q;B ,T) = [M 2 - m2 - - B - M ] -1-Propagator:
[Chanfray et al, Herrmann et al, RR et al, Koch et al, Klingl et al, Mosel et al, Eletsky et al, Oset et al, Sasaki et al …]
= B,M=Selfenergies:
Constraints: decays: B,M→ N, scattering: N → N, A, …
B /0
0 0.1 0.7 2.6
[RR,Wambach et al ’99]
Meson “Melting” Switch off Baryons
2.6 Axialvector in Medium: Dynamical a1(1260)
+ + . . . =
Vacuum:
a1
resonance
InMedium: + + . . .
• in-medium + propagators• substantial broadening of - scattering amplitude• consequences for chiral restoration to be elaborated
[Cabrera,Jido,Roca+RR ’09 in preparation]
3.) Dilepton Spectra in A-A and -A
Thermal Dilepton Emission Rate:e+
e-
)T,q(fMqdxd
dN Bee023
2em
44
Im Πem(M,q;B,T)
Thermal Sources: Relevance:
- Quark-Gluon Plasma: high mass + temp. qq → e+e , … M > 1.5 GeV, T >Tc
- Hot + Dense Hadron Gas: M ≤ 1 GeV → e+e , … T ≤ Tc
-
q
q
_
e+
e
e+
e
Im Πem ~ Im D
3.1 Dilepton Rates: Hadronic vs. QGP
dRee /dM2 ~ ∫d3q f B(q0;T) Im em
• Hard-Thermal-Loop [Braaten et al ’90]
enhanced over Born rate
• Hadronic and QGP rates “degenerate” around ~Tc
• Quark-Hadron Duality at all M ?! ( degenerate axialvector SF!)
[qq→ee] [HTL]
-
3.2 Dilepton “Excess” Spectra at SPS
• “average” (T~150MeV) ~ 350-400 MeV
(T~Tc) ≈ 600 MeV → m
• fireball lifetime: FB ~ (6.5±1) fm/c[van Hees+RR ‘06, Dusling et al ’06, Ruppert et al ’07, Bratkovskaya et al ‘08]
)y,M(Acc),T;q,M(qxdd
dNq
qMd)(Vd
dMdN
iFB
fo
44
therm
0
3therm
0
Thermal Emission Spectrum:
3.2.2 NA60 Data vs. In-Medium Dimuon Rates
• acceptance-corrected data directly reflect thermal rates!
M[GeV] [RR,Wambach et al ’99]
[van Hees+RR ’07]
3.2.3 NA60 Dimuons: Sensitivity to QGP and Tc
• vary critical and chemical-freezeout temperature (Tfo ~ 130 MeV fix)
• overall shape of spectra robust: “duality” of dilepton rate around “Tc”!
• yields slightly larger for large Tc (hadronic volume!), || < 1fm/c
• intermediate mass (M>1GeV): QGP vs. hadronic depends on Tc
Intermediate Mass Region“EoS-B” “EoS-C”
3.3 Low-Mass Dileptons at RHIC: PHENIX
• Successful approach at SPS fails at RHIC
3.4Meson in Cold Nuclear Matter
+ A → e+e X e+
e
Nuclear Photo-Production:
[CLAS/JLab ‘08]
[Riek et al ’08]Theoretical Approach:
Mee[GeV]
Fe - Ti
N ≈ 0.5 0
N
elementary production amplitude
in-medium spectral function+
M [GeV]
E=1.5-3 GeV
4.) Conclusions
• Electromagnetic Probes - study matter properties in nuclear reactions - low mass: in-medium vector mesons
• Chiral Symmetry Breaking (Restoration) - chiral partners: - a1 (degeneracy at Tc)
• Thermal Dilepton Rates - melting toward Tc (quark-hadron duality?)
• Dilepton Spectra - quantitative agreement at SPS - ok at TJNAF (-A) - failure at RHIC thus far
4.5 EM Probes in Central Pb-Au/Pb at SPS
• updated fireball (aT=0.045→0.085/fm)• very low-mass di-electrons ↔ (low-energy) photons
[Srivastava et al ’05, Liu+RR ‘06]
Di-Electrons [CERES/NA45] Photons [WA98]
[van Hees+RR ‘07]
4.8 Axialvector in Medium: Explicit a1(1260)
>
> >
>
N(1520)…
,N(1900)…
a1 + + . . .
Exp: - HADES (A): a1→(+-) - URHICs (A-A) : a1→
)DImg
mDIm
g
m(
s
dsf a
a
a1
1
1
2
4
2
42
N-1
2.5Cold Nuclear Matter: Photo-Production
Fe -Ti N ≈ 0.5 0
+ A → e+e X
E=1.5-3 GeV
[Riek et al ’08]
[CLAS/JLab +GiBUU ’08]
2.3.2 Acceptance-Corrected NA60 Spectra
• more involved at pT>1.5GeV: Drell-Yan, primordial/freezeout , …M [GeV] M [GeV]
X.) Example for Comprehensive Analysis: NA60
thermal medium radiating from around Tc with melted ,
well-bound J/ with large collectivity
DileptonsCharmonium
FlowCharmonium
Production
2.4 Spectral Function at Lower Collision Energies
• largest sensitivity for M ≤ 0.4 GeV soft modes!
• Critical point: -L mixing (q≠0) with m→ 0, but: → e+e signal (too) weak