V. Workshop on Particle Correlations and Femtoscopy

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V. V. Workshop on Particle Workshop on Particle Correlations and Femtoscopy Correlations and Femtoscopy Significant in-medium reduction of the mass of η’ mesons in √s NN = 200 GeV Au+Au collisions Róbert Vértesi 1 , Tamás Csörgő 1,2 , János Sziklai 1 1 MTA KFKI RMKI, Budapest Hungary 2 Department of Physics, Harvard University, Cambridge USA arXiv:0905.2803 [nucl-th] CERN, 10/14/2009 η η η η * * 10/14/2009 1 R.

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V. Workshop on Particle Correlations and Femtoscopy. η ’. η ’. *. Significant in-medium reduction of the mass of η ’ mesons in √s NN = 200 GeV Au+Au collisions Róbert Vértesi 1 , Tam ás Csörgő 1,2 , János Sziklai 1 1 MTA KFKI RMKI , Budapest Hungary - PowerPoint PPT Presentation

Transcript of V. Workshop on Particle Correlations and Femtoscopy

Page 1: V.  Workshop on Particle Correlations and  Femtoscopy

V.V. Workshop on Particle Workshop on Particle Correlations and FemtoscopyCorrelations and Femtoscopy

Significant in-medium reduction of the mass of η’ mesons

in √sNN= 200 GeV Au+Au collisions

Róbert Vértesi1, Tamás Csörgő1,2, János Sziklai1

1MTA KFKI RMKI, Budapest Hungary2Department of Physics, Harvard University, Cambridge USA

arXiv:0905.2803 [nucl-th]

CERN, 10/14/2009

ηη’’ ηη’’**

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OutlineOutline Three-quark model, Chiral symmetry breaking

Restoration of symmetry in a hot, dense medium

Role of the η' mass Dilepton spectra in Heavy Ion Collisions η' mass through π± Bose-Einstein correlations

Possible experimental signatures BEC measurements at RHIC Dilepton excess found by PHENIX

BEC-calculations for different models Spectra, λ*(mT), systematics…

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Chiral Symmetry BreakingChiral Symmetry Breaking The three-quark model

SU(3) flavour-symmetry Spontaneously broken => 9 Goldstone bosons Corresponding to light mesons

There are only 8! (Meson-octet)

UA(1) chiral symmetry explicitly broken Distinct topological vacuum-states Tunneling b/w them – quasiparticles (instantons) 9th boson gains mass − η' (958 MeV)

KK00

ππ−− ππ++

KK++

KK−− KK00

ηη

ηη’’ππ00

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Restoration of the Symmetry Restoration of the Symmetry in a Hot, Dense Mediumin a Hot, Dense Medium

High energy densities Asymptotic freedom αs → 0 Nontrivial topology vanishes U(1) no more broken SU(3) restored

Remark:From SSB, One expects massless mesons.However, the flavour symmetry is inexact.

Mass reductionLower bound (Gell-Mann – Okubo):Upper bound (S,NS isosinglet eigenstates):

Δm is the extra mass from instantons in a not-so-dense medium

KK00

ππ−− ππ++

KK++

KK−− KK00

ηη

ηη’’**

ππ00

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Signature: Particle AbundancySignature: Particle Abundancy Hagedorn-model

Production of light mesons:

TH~160 MeV Hagedorn-temperature

In case of a possible mass drop: Number of η's would be small: With a strongly reduced η' mass:

An enhancement of a factor of 50 at maximum Increased weight of strange states, rather 3 to 16

Consequence of the reduced mass:An increased abundancy of η' mesons

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The The ηη' ' through Phase Transitionthrough Phase Transition Hadronization

Reduced-mass η' mesons produced with a decreased mass with an increased abundancy

Decoupling from non-Goldstonic matter Mean free path for annihilation is large Long lived

”Condensate” in the medium Low-pT η' mesons are unable to get on-shell in the vacuum Medium acts as a trap for low- pT η's

As medium dissolves, the η's regain their original mass

The Return of the prodigal Goldstone boson. J. I. Kapusta, D. Kharzeev, L. D. McLerran Phys.Rev.D53:5028-5033,1996. Hep-ph/9507343

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Channels of ObservationChannels of Observation

Leptonic decay Increased η'/π proportion in the low-pT range Excess in the ℓ+ℓ− spectrum under the ρ mass

η meson (BR=63%) Enhancement of η production BEC of charged pions

Sensitive to the sources of the pions

Direct measurement? Would be convincing, however, poor S/B ratio (π0→γγ)

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10/14/2009

Discovered and still used in Astrophysics

Consider two plain vawes:

Bosons: symmetrization needed

Spectra:

Correlation:

Simplified picture: plain wave, no multiparticle-interactions, thermalization etc.

HBT HBT effecteffect (BEC (BEC))

k1 k2

x1

x2

1,2

S(x,k)

source

detector

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Pions from QM freezeout Primordial (from phase transition) Fast decaying resonances Long-life resonances (ω,η,η',KS

0)

Correlation

Intercept

Correlation measurent ↔ λ*(mT) ↔ core−halo ratio

ππ±± Correlations Correlations and the and the Core-Halo Core-Halo picturepicture

Core

Halo

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Core: π±, K±, Λ, Σ, …

Halo: η’, η, ω, KS

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Simulating the CondensateSimulating the Condensate Resonance ratios from different models

ALCOR, FRITIOF, Kaneta et al., Letessier et. al., Stachel et al., UrQMD.

η' excess:

Restored η' mass: If , the η' can’t get onshell;

a M-B distribution is assumed:

Parameters From measurements TFO = 177 MeV, <uT> = 0.48 Conservative assumption TFO

η' =TFO Tcond=TFO

Hydrodynamical models α (related to the dimension of expansion) Looked for: in-medium mass mη'

* inverse slope B-1

Spectra from decays using JETSET10/14/2009 10 R. Vértesi

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Data:NA44 200 GeV S+Pb

Resonances:FRITIOF

Earlier, less refinedmodelling of condensate

No sign of mass reduction

SPS SPS data and simulation: No signdata and simulation: No signalal

Signal of partial U(A)(1) symmetry restoration from two pion Bose-Einstein correlationsT. Csörgő, D. Kharzeev,, S.E. Vance. e-Print: hep-ph/9910436

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NA44S+Pb data

mT (GeV)

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RHIC RHIC datadata Properties

Central Au+Au sNN1/2 = 200 GeV

Mid-rapidity |η|<0.1 π+π+ correlation measurements λ*(mT)/λ*max

(different methods)

Data used in the analysis PHENIX Sinyukov 50% STAR Edgeworth expansion

(6th order, only even)

Shown for comparison purposes PHENIX preliminary STAR Gauss

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Finding the most likely massFinding the most likely mass

Simulations all over the (B-1, m*) plain Here: Resonance ratios of Kaneta & Xu, arXiv:nucl-th/0405068

Mapping the confidence level Choose best λ*(mT)/λ*max fit

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Calculations vs. PredictionCalculations vs. Prediction

Theoretical region: Kapusta et al. arXiv:nucl-th/9507343 Sigma-contours from model calculations: either in

accordance with theory, or slightly below Different α expansion exponents: systematic uncertainity

α = -1/2α = 0

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SSystematics and Resultsystematics and Results

Largest uncertainity: models for resonance ratios

Modifying parameters in the widest reasonable range −1/2 ≤ α ≤ +1/2 (1) 140 MeV ≤ Tcond

≤ 220 MeV

100 MeV ≤ TFO ≤ 177 MeV(altogether 17 x 1248 x 1000000 events simulated)

An upper boundary can be determined for the η’ mass: Each and every setup fails when m*η’ > 750 MeV (failure means CL<0.1%)

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Systematics – a Visual SummarySystematics – a Visual Summary

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Dilepton Excess in CERESDilepton Excess in CERES

Measurement

Model calculations

Excess in the range b/w the π and ρ mass

Invariant e+ e- pair yield measurements compared to hadronic model yealds e+ e- pair production in Pb - Au collisions at 158-GeV per nucleon.

CERES cn. (G. Agakichiev et al.). Jun 2005. 39pp. Eur.Phys.J.C41:475-513,2005. e-Print: nucl-ex/0506002

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Au+Au invariant e+ e- pair yield

Significant excess in PHENIX 200 GeV Au+Au measurements Not present in p+p data – in accordance with hadronic models Excess must be an effect of the hot, dense medium

Dilepton ExcessDilepton Excess in in PHENIXPHENIX

A. Adare et al. (PHENIX cn.)Phys.Lett.B670:313-320,2009.

S. Afanasiev et al. (PHENIX cn.) e-Print: arXiv:0706.3034

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The η’ Spectrum

Resonance ratios from Kaneta – Xu arXiv:nucl-th/0405068 An enhancement factor of ~24, mostly at low-pT

Breaks mT –scaling at low-pT

Possible explanation of the dilepton excess needs check!

mT-m [GeV]

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Cross-check with dilepton spectrum needed

More λ* data at low pT is needed to reduce systematics

Revitalize interest in chiral symmetry restoration

KK00

ππ−− ππ++

KK++

KK−− KK00

ηη

ηη’’**

ππ00 200 MeV

at the 99.9% confidence levelfrom PHENIX+STAR π+π+ correlation data + 6 models

m*η’ mη’

ConclusionConclusion

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The EndThe End

Thank You for your attention

backup slides follow…

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mmTT-s-scalingcaling

pp

central

periph.

E. Shuryak, Prog.Part.Nucl.Phys.53:273-303,2004. 

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ηη' mass: ' mass: Fitted valuesFitted values

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ηη' mass: ' mass: Acceptability boundariesAcceptability boundaries

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Dilepton excess in detailsDilepton excess in details

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ReResonancessonances: : Kaneta-Xu Kaneta-Xu vs. RHICvs. RHIC

Statistical chemical freezeout model Central mid-η 200 GeV Au+Au Describes PHENIX hadron spektrum well

Kaneta & Xu, arXiv:nucl-th/0405068

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ReRessonanconanceses::Letessier-Rafelski vs. RHICLetessier-Rafelski vs. RHIC

Statistical chemical freezeout model Central mid-η 200 GeV Au+Au

J.Letessier J.Rafelski, arXiv:nucl-th/0504028

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ReRessonanconanceses::ALCORALCOR vs. RHIC vs. RHIC

Coalescence-model

η’/ η ratio has to be fixed from other models (Kaneta, here)

P. Levai, T.S. Biro, T. Csorgo, J. Zimanyi, hep-ph/0007247

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ReResonancessonances::FRITIOF vs.FRITIOF vs. RHIC RHIC

200 GeV mid-rapidity Au+Au simulation Note:Does not describe STAR data, neither the unified PHENIX+STAR

dataset. For PHENIX data only, it is consistent with mη’=958MeV.

B. Anderson et al., Nucl. Phys. B 281 (1987) 289.

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ReRessonanconanceses::Stachel et al. vs. RHICStachel et al. vs. RHIC

Statistical chemical freezeout model Central mid-η 200 GeV Au+Au

J.Stachel et al., arXiv:nucl-th/9907090

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ReRessonanconanceses::UUrQMD vs. RHICrQMD vs. RHIC

200 GeV midrapidity

Au+Au, RHIC √sNN=200 GeV

J. P. Sullivan et al., Phys. Rev. Lett. 70 (1993) 3000

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Rafelski vs. PHENIXRafelski vs. PHENIX

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Rafelski vs. PHENIX & STARRafelski vs. PHENIX & STAR

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Rafelski vs. STARRafelski vs. STAR

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SSystematicsystematics: : Rafelski Rafelski αα=−1/2=−1/2

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SSystematicsystematics: : Rafelski Rafelski αα=0=0

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SSystematicsystematics: : Rafelski Rafelski αα=+1/2=+1/2

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SSystematicsystematics: : Rafelski T’Rafelski T’=140 MeV=140 MeV

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SSystematicsystematics: : Rafelski T’Rafelski T’=177 MeV=177 MeV

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SSystematicsystematics: : Rafelski T’Rafelski T’=220 MeV=220 MeV

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SSystematicsystematics: : Rafelski TRafelski TFOFO=100 MeV=100 MeV

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SSystematicsystematics: : Rafelski TRafelski TFOFO=177 MeV=177 MeV

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