what does the rho do? na60’s dimuon experiment and in-medium modifications of vector mesons
DESCRIPTION
Jörg Ruppert. Thorsten Renk. Nuclear Theory, Department of Physics, McGill University, Montreal, Quebec, Canada. Department of Physics, University of Jyväskylä, Jyväskylä, Finland. In collaboration with:. - PowerPoint PPT PresentationTRANSCRIPT
J. Ruppert Quark Matter 2006, Nov. 2006
What does the rho do? NA60’s dimuon
experiment and in-medium modifications
of vector mesonsJörg Ruppert
Nuclear Theory, Department of Physics,McGill University, Montreal, Quebec, Canada
In collaboration with:
Thorsten RenkDepartment of Physics,
University of Jyväskylä, Jyväskylä, Finland
J. Ruppert Quark Matter 2006, Nov. 2006
Outline
1. Dilepton emission in URHIC2. Dynamical Evolution3. In-Medium modifications4. NA60’s 158 AGeV In-In di-muon
spectra 5. Conclusions
J. Ruppert Quark Matter 2006, Nov. 2006
Focus on dileptons in low mass region in this talk
EM probes in URHICEM probes in URHIC
J. Ruppert Quark Matter 2006, Nov. 2006
What to learn from dilepton emission?
What to learn from dilepton emission?
Averaged in-medium photon spectral function(EM correlator)
In-medium EM current-current correlator and dynamical evolution of the system are folded in order to predict the spectrum.
On top of that contributions from non-thermal sources (hadron decays, Drell-Yan, open charm etc.)
(modulus factor accounting for finite lepton masses)
(Equilibrium description, for firstnon-equilibrium studies see Schenke, Greiner)
J. Ruppert Quark Matter 2006, Nov. 2006
Evolution vs. EM correlator
Evolution vs. EM correlator
J. Ruppert Quark Matter 2006, Nov. 2006
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Reliable (extensively tested for PbPb) fireball evolution model as basis for In-In calculations!
T. Renk (2005)
Dynamical evolution model for URHIC
Dynamical evolution model for URHIC
J. Ruppert Quark Matter 2006, Nov. 2006
“Vacuum rho” vs. “cocktail rho”“Vacuum rho” vs. “cocktail rho”
Concept introduced and importance of vacuum rho contribution
pointed out in Renk, Ruppert, hep-ph/0605130.
Contribution is important for all centrality classes!
J. Ruppert Quark Matter 2006, Nov. 2006
Flow profile and pt Flow profile and pt
J. Ruppert Quark Matter 2006, Nov. 2006
Vector-meson dominanceVector-meson dominance
The current-field identity(J. J. Sakurai)
μυυμμυυμρρ Π⇒⇒⇒ ImImImIm JJD Spectral density
Dilepton emission in URHIC in the low mass region can teach us about in-medium modifications of vector mesons spectral densities once the dynamical evolution is fixed!
J. Ruppert Quark Matter 2006, Nov. 2006
In-Medium vector mesons
In-Medium vector mesons
Vector-meson spectral densities as calculated in hadronicmany-body approaches. E.g. Rapp & Wambach (1999), Lichard & Gale (1994), Renk&Mishra (2004), Lichard & Juran (2006)
Vector-meson spectral densities as inferred from experiment. E.g. Shuryak (1991); Eletsky & Ioffe (1997); Eletsky, Belkacem, Ellis, Kapusta (2001); Martell & Ellis (2004), Klingl, Kaiser, Weise (1997)
J. Ruppert Quark Matter 2006, Nov. 2006
Hot meson gas in Phi-functional approach
Hot meson gas in Phi-functional approach
Nota Bene: Results for in-medium modifications of the rho-meson based onRuppert, Renk, Phys.Rev.C71:064903,2005 are to be reinvestigated (Calculations
for an erratum are in progress. Prepints using this spectral function for
dilepton studies will be updated.) Thanks to Knoll, Riek, and van Hees for pointingout a wrong numerical factor in the self-energy formulas and discussions regarding
the influence of spurious modes on the results.
Phi-Functional approach [Baym, Luttinger, Ward, Cornwall, Jackiw, Tomboulis]
All results presented here don’t rely on this approach.
J. Ruppert Quark Matter 2006, Nov. 2006
Vector Meson spectral densities as inferred from experiment
Vector Meson spectral densities as inferred from experiment
Eletsky, Belkacem, Ellis, Kapusta (2001)
Contribution to retarded self-energy from rho/particle pion/nucleon scattering
Scattering amplitude in cm-frame from rho/ particle pion/nucleon scattering
Shuryak (1991), Eletsky & Ioffe (1997)
J. Ruppert Quark Matter 2006, Nov. 2006
Comparison to NA60 data
Comparison to NA60 data
QGP quasi-particle picture,(Schneider et al. (2002))
In-medium Rho spectral function(Eletsky et. al. (2001))
In-medium Omega spectral function(Martell & Ellis (2004))
(Results were obtained by folding with the schematic acceptance matrix,
not the full MC acceptance simulation.)
In-medium Phi not (yet)included
Renk, Ruppert (2006)
Contributions included in our calculation:
J. Ruppert Quark Matter 2006, Nov. 2006
Pt-cut M-spectraPt-cut M-spectra
(Results were obtained by folding with the schematic acceptance matrix,not the full MC acceptance simulation. Theory curves for high p_T are integratedup to p_T<1.5 GeV.)
Renk, Ruppert (2006)
J. Ruppert Quark Matter 2006, Nov. 2006
Results for central collisions
Results for central collisions
(Results were obtained by folding with the schematic acceptance matrix,not the full MC acceptance simulation.)
Renk, Ruppert (2006)
J. Ruppert Quark Matter 2006, Nov. 2006
pt - spectrapt - spectra
•Good description in low-mass, rho-like, and higher-mass region can already be obtained with the original version of the scaled evolution (hep-ph/0605130). Adjustment in flow profile lead only to a ~10 MeV change in slope. Model accounts for the data above p_T>0.5 GeV.
J. Ruppert Quark Matter 2006, Nov. 2006
What to learn from pt - spectra?
What to learn from pt - spectra?
•Rather insensitive to intrinsic momentum dependences of in-medium hadronic spectral-functions and QGP rate, sensitive to emission temperature and flow => Tool to characterize emission region.
•pT-spectrum above ~1 GeV (in 0.6<M<0.9 GeV integrated region)and above ~1.25 GeV (in 0.4<M<0.6 GeV) dominated by vacuum-rho,naturally small contribution to the M>1.0 GeV region.
•Effective T* is significantly lower in 1.0<M<1.4 GeV integrated region. This is an strong indication of a different source in comparison to lower mass regions.
•pT-spectrum in 1.0<M<1.4 GeV integrated region is in our evolutiondominated by a partonic source.
J. Ruppert Quark Matter 2006, Nov. 2006Compilation by S. Damjanovic
pt -spectra model-comparison
pt -spectra model-comparison
J. Ruppert Quark Matter 2006, Nov. 2006
What about 4pi contribution?What about 4pi contribution?Suggested as dominant source due to chiral mixing in the M>1 GeV region by van Hees & Rapp (2006) (for details of their approach see next talk).
We employed a different rate to study 4-pi contributions in our evolution, namely
4-pion annihilation rates by Lichard (2006) (cmp. also Lichard & Juran (2006)).
Assumption: 4pi-processes are contributing as 2pi-processes all the way down to Tf=130 MeV (augmented by the corresponding fugacity factor) .
Gives an upper limit of the contribution.
Lichard (2006), hadronic interaction adjusted to describe BaBar Data
In-medium-Phi not(yet) included.
Renk, Ruppert (2006)
J. Ruppert Quark Matter 2006, Nov. 2006
Discrimination of dominant source in M>1.0 GeV region via pt
- spectra
Discrimination of dominant source in M>1.0 GeV region via pt
- spectra Different mechanisms:Experimentum crucis•QGP dominant, contributes at higher T, low flow. If this is the dominant source=> lower effective T* in dilepton pt - spectra (1.0<M<1.4 GeV
integrated)
•4pi-annihilation, contributes significantly close to Tf << Tc
(augmented by fugacity factor), considerable flow has built up.
If dominant source => higher effective T* in pt - spectra (1.0<M<1.4 GeV integrated)
General argument based on flow is not specific to one evolution model!
J. Ruppert Quark Matter 2006, Nov. 2006
SummarySummary•Reliable dynamical evolution essential to infer information about in-medium modifications of EM-current-current correlator
•Different sources (Vacuum rho, in-medium vector mesons, QGP, 4pi) built up dilepton-spectrum! Still clear message from low mass dileptons => Substantial in-medium broadening of the Rho-meson necessary to describe low mass dimuon enhancement.
• Substantial broadening of Rho-meson caused by scattering off from nucleons and pions (Eletsky et al. (2002)), partial contribution from pion scattering in In-In substantial. In-medium broadening including scattering off by nucleons and pions seem to be on the same order as Rapp/Wambach (1999) approach. (see talks R. Rapp and H. van Hees).
•pt - spectra can probe different stages of the medium-evolution and reveal information about the dominant sources in different mass regions. Important:flow must be implemented consistently.
•Experimental pt - spectra indicates substantial contribution from partonic component in the 1 GeV<M<1.5 GeV region.
•Outlook: Calculations for the IMR region 1 Gev<M<3 GeV.
Special thanks to
S. Damjanovic, C. Gale,
J. Kapusta,
P. Lichard, B. Müller,
B. Neufeld, H. Specht
J. Ruppert Quark Matter 2006, Nov. 2006
J. Ruppert Quark Matter 2006, Nov. 2006
4-pion annihilation as inferred from hadronic
interactions
4-pion annihilation as inferred from hadronic
interactions
Lichard (2006)
Example: Annihilation of four chargedpions into a rho-meson and viaVMD into dileptons.
Comparison between model prediction an inverse process Measurement byBaBaR.
J. Ruppert Quark Matter 2006, Nov. 2006