Study of the QCD Phase Structure through High Energy Heavy Ion Collisions
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Study of the QCD Phase Structure through High Energy Heavy Ion Collisions Bedanga Mohanty National Institute of Science Education and Research (NISER) ine: QCD Phase Structure Theoretical and Experimental status Highlights from RHIC Beam Energy Scan Program Summary 1
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Study of the QCD Phase Structure through High Energy Heavy Ion Collisions. Outline: QCD Phase Structure Theoretical and Experimental status Highlights from RHIC Beam Energy Scan Program Summary. Bedanga Mohanty National Institute of Science Education and Research (NISER). - PowerPoint PPT Presentation
Transcript of Study of the QCD Phase Structure through High Energy Heavy Ion Collisions
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Study of the QCD Phase Structure through High Energy Heavy Ion Collisions
Bedanga MohantyNational Institute of Science Education and Research
(NISER)
Outline: QCD Phase Structure Theoretical and Experimental status Highlights from RHIC Beam Energy Scan Program Summary
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Phase Diagram and Basic Interactions
Phase diagram of Water Electromagnetic interactionPrecisely known
Phase diagram of strong interactionsLargely still a conjecture
arXiv:1111.5475 [hep-ph]
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QCD Phase Diagram
Rich phase structure:-- Phases QGP & Hadronic-- Cross over-- 1st order-- Critical Point
Physical systems undergo phase transitions when external parameters such as the temperature (T) or a chemical potential (μ) are varied.
Conserved Quantities: Baryon Number ~ Electric Charge ~ Q ~ small Strangeness ~ S ~ small
K. Rajagopal and F. Wilczek, Handbook of QCD
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QCD Phase Diagram - Experimental
Vary beam energy to change Temperature & Baryon Chemical Potential
Vary: T, B, S, Q
Conservation in strong interactions-- Charge -- Baryon number-- Strangeness
Nature 448 (2007) 302
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Transition Temperature
Nucl. Phys. A 830 (2009) 805c
Prog. Theor. Phys. Suppl. 153, 106 (2004)
gparton ~ 47 ~ g (2/30)
g ~ 3
High Temperature De-confined state of quarks and gluons
Science 332 (2011) 1525-1528
Phys.Rev. D85 (2012) 054503
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Cross-over Nature443:675-678,2006
No significant volume dependence
At high T and = 0 is a cross over.
JHEP 1208 (2012) 053
Phys. Rev. Lett. 110, 012302 (2013)
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Establishing Quark Gluon Phase
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initial > c (Lattice)
At and below 11.5 GeV – Hadronic interactions dominate. Need pA data for a quantitative statement.
QGP turned off ?
STAR: QM2012
Eur.Phys.J. C72 (2012) 1945; Advances in High Energy Physics 2013
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Establishing Quark Gluon Phase
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Partonic Collectivity De-confinementTurned off at low energy ?
STAR Preliminary
Phys. Rev. Lett., 110, 142301 (2013)
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Establishing Quark Gluon Phase
At and below 11.5 GeV – Hadronic interactions dominate.
QM2012: STAR
o Possible Local Parity Violation effectso Requires De-confined matter of quarks and gluonso Requires chiral symmetry to be restored
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QCD Phase structure at B ~ 0 Close to zero baryonic chemical potential the
QCD transition corresponding to a state of de-confined quarks and gluons takes place at high temperature.
First principle QCD calculations suggest it is a cross over. Indirectly supported by experimental data.
Transition temperature using chiral condensates ~ 154 MeV, using Susceptibilities and Polyakov loop ~ 175 MeV – width around 15 MeV
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Transition Line - Theory
Width of transition line wide Freeze-out line close to transition line at Lower B
Larger B deviations of freeze-out curve from transition line Interesting T vs. B dependence at lower beam energies
JHEP 1104 (2011) 001
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Softening of Equation of State
Minimum between 11-20 GeV Softening of Equation of State ?
STAR Preliminary
Theory:D. H. Rischke et al., Heavy Ion Phys. 1, 309 (1995).H. Stoecker, Nucl. Phys. A 750, 121 (2005).J. Brachmann et al., Phys. Rev. C 61, 024909 (2000).L. P. Csernai and D. Rohrich, Phys. Lett. B 458, 454 (1999).
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QCD Phase structure at B > T Transition line from lattice QCD has large
uncertainties.
Transition line close to chemical freeze-out line at small B but deviates at large B. Interesting trends of T vs. B at lower energies.
Experimental hints towards no QCD transition to de-confined state ~ 11.5 GeV center of mass energy.
Directed flow data shows non-monotonic dependence on beam energy – Soft EOS ?
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Search for Critical Point - Theory
Numerical QCD calculations difficult at large B – sign problem
Techniques: Reweighting, Taylor expansion & imaginary potential
Issues (not common to all) : lattice spacing, physical quark mass, continuum limit, Volume
Theory still some more work to be done …… need more CPU
S. Gupta, QM2009 Acta Phys.Polon.Supp. 5 (2012) 825-835Phys. Rev. D 78, 14503 (2008);
JHEP 0404, 50 (2004)Phys.Rev.D71:114014,2005
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Search for Critical Point - Experiment
Nuclear liquid-gas transition with a critical end point
Beam Energy Scan Program at RHIC
Observables : Related to correlation length or susceptibility
< (N)2> ~ 2 < (N)3> ~ 4.5 < (N)4> - 3 < (N)2>2 ~ 7
Challenging to measure :Finite size effects < 6 fmCritical slowing down, finite time effects ~ 2 - 3 fm
No dynamical theoretical estimates exists. Experimentally look for non-monotonic variations with beam energy (T, B).
S ~
Phys.Lett. B696 (2011) 459Phys.Rev.Lett. 105 (2010) 022302
Phys. Rev. Lett. 102, 032301 (2009)Phys. Rev. Lett. 91, 102003 (2003)Phys. Rev. D 61, 105017 (2000)
Phys.Rev.Lett. 107 (2011) 052301
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Search for Critical Point - Experiment
STAR: arXiv: 1309.5681 (submitted to PRL)Phys.Rev.Lett. 105 (2010) 022302
Central collisions Deviations from PoissonianDeviations from transport modelDeviations from peripheral collisions Higher statistics needed at 7.7 & 11.5 GeV + a new data point around ~15 GeV
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More on Net-proton Higher Moments
Below 27 GeV results dominated by protons only
Anti-protons follow Poisson
Protons deviate from Poisson
Net-protons deviate from Poisson
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More on Net-proton Higher Moments
Comparison with Hadron Resonance Gas Model with exact acceptance.
Deviations from HRG model observed
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QCD Phase structure: Critical Point
Science 332 (2011) 1525-1528
Theory: Lattice QCD calculations have uncertainties. Some calculations indicate it to lie between 10-30 GeV beam energy
Experiment: If signal survives hadronization then ruled out for beam energies > 39 GeV
Promising prospects below 39 GeV. High statistics data set needed below 20 GeV.
Theory+Experiment: Need quantitative dynamical theory calculations with realistic correlation lengths to compare to data.
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Rich Physics from RHIC - BES
No Jet quenching
Jet quenching
Softening of EOS
Critical point search
NCQ Scaling
No NCQ Scaling
NCQ Scaling
No NCQ Scaling
CME
No CME
Caveat: Qualitative picture
STAR Preliminary
STAR Preliminary
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Experimentally accessible by colliding Heavy-Ions at different beam energies
QGP
Hadron Gas
Lattice QCD and experiments suggest there are two distinct phasesBeam Energy Scan Program – hints at turn-off of QGP signatures
QGP
Hadron Gas
154 – 175MeV
Cross-over
At~ 0 : Lattice QCD: Transition temperature and cross-overSupported by experimental data
QGP
Hadron Gas
154 – 175MeV
Cross-over
First order
At> T: Lattice QCD and Models : CP and transition line(model uncertainties needs to be controlled)Experimental data very intriguing : proton v1 and fluctuations
SummaryWhat is known about the QCD phase diagram and to what degree ?
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Phase structure: Interesting Possibilities
Quarkyonic phase (Theoretical) Experimental signature (Baryon correlations, Photons) ?
Rept.Prog.Phys. 74 (2011) 014001
Nucl.Phys. A830 (2009) 709C-712CNucl. Phys. A 796, 83 (2007 arXiv:1302.1119
