system size and beam energy dependence of azimuthal anisotropy from phenix michael issah vanderbilt...
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System size and beam energy System size and beam energy dependence of azimuthal anisotropy dependence of azimuthal anisotropy
from PHENIXfrom PHENIX
Michael IssahVanderbilt University
for the PHENIX Collaboration
QM2008, Jaipur, India
QM 2008, Jaipur, India
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Origin of azimuthal anisotropy
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Interactions among the produced particles lead to pressure gradients which generate an azimuthal anisotropy in particle emission or elliptic flow, measured by v2, from which can be obtained valuable information about the early dynamics after the collision
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Spatial anisotropy Momentum anisotropy
QM 2008, Jaipur, India
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Azimuthal anisotropy at different beam energies in Azimuthal anisotropy at different beam energies in Au+AuAu+Au collisionscollisions
Comparison between v2 for different pT and centralities show that the measured v2 is very similar at different beam energies Suggests that v2 does not change much with beam energy over the range √s=62.4-200 GeV
0-10%
10-20% 20-30% 30-40%
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Centrality and pT dependence of elliptic flow at different
beam energies
Detailed differential centrality and pT dependence of v2 show similar magnitudes at √s = 62.4, 130 and 200 GeV Increase in measured v2 between SPS energies and RHIC energies
PRL 94, 232302 (2005)
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Beam energy dependence of elliptic flowBeam energy dependence of elliptic flow
v2 saturates in the energy range √s=62.4-200 GeV suggesting a softening of the equation of state of matter at RHIC Extracted value for <cs> ≈ 0.35 ± 0.05 or <cs
2> ≈ 0.12 (PRL 98, 162301) This value lies between the ideal gas limit (cs
2=1/3) and mixed phase value (cs
2=0)
PRL 94, 232302 (2005)
F. Karsch, hep-lat/0601013
QM 2008, Jaipur, India
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Beam energy comparison in Cu+CuBeam energy comparison in Cu+Cu
Measured v2 in Cu+Cu at √s = 62.4 GeV is observed to be of comparable magnitude or somewhat lower than v2 √s = 200 GeV. Systematic errors are big. The smaller size of the system and smaller energy densities created in Cu+Cu may be factors in explaining the difference observed in Cu+Cu compared Au+Au system
0-10% 10-20% 20-30% 30-40%
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PRL. 98, 162301 (2007)
Hydrodynamic behavior tested by transverse kinetic energy scaling for low transverse kinetic energy KET = mT – m Baryon and mesons scale separately after KET ≥ 1 GeV Partonic recombination manifest by scaling by the number of constituent quarks nq (NCQ scaling) NCQ scaling is observed to break at around KET/nq ~1 GeV – see S. Huang’s talk later in the sesssion
Test of hydrodynamic behavior and partonic degrees of Test of hydrodynamic behavior and partonic degrees of freedom in Au+Au collisions at freedom in Au+Au collisions at √s = √s = 200 GeV200 GeV
QM 2008, Jaipur, India
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Similar picture in Au+Au at 200 GeV and 62.4 GeV Partonic degrees of freedom are manifest in Au+Au collisions at √s=62.4 GeV
Au + Au at √s = 62.4 GeV
QM 2008, Jaipur, India
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NCQ scaling NCQ scaling across systems and beam energies
Au+Au 200 GeV Cu+Cu 200 GeV Au+Au 62.4 GeV
PRL. 98, 162301 (2007)
Number of constituent quark scaling holds in Au+Au and Cu+Cu colliding systems at 200 GeV at low KET
Suggests that coalescence of particles with the quantum numbers of quarks occurs over the energy range 62.4 – 200 GeV for colliding systems of different sizes
Centrality 10-40%min bias
QM 2008, Jaipur, India
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KET + Number of constituent Quarks (NCQ) scaling
Scaling seems to hold well for different centralities up to 60% centrality The goodness of the scaling can be tested by fitting the scaled curves with a polynomial and taking ratio of data/fit
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Ratio of measured v2 to a fit to the data confirms that there is good NCQ scaling in the region where such scaling is expected to hold Scaling fails at low KET/nq (<0.2). Could be due to feed down from resonances More in-depth study of systematic errors needed at low KET as well as comparison to hydrodynamic models
NCQ scaling and fit to data
QM 2008, Jaipur, India
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Reaction plane v2 less affected by non-flow than cumulant v2 because of large rapidity gap between PHENIX central arms and BBCs
Non-flow mainly due to jet correlations
Differences between reaction plane and cumulant v2 measurements show that jet correlations become influential as from pT ~3.5 GeV/c at all centralities
Non-flow contributions in Au+Au at Non-flow contributions in Au+Au at √s=200 GeV√s=200 GeV
PHENIXPreliminar
y
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High statistics Run7 data enable detailed study of different flow harmonics
v4 of unidentified hadrons scale with integral flow between centrality 10-40%
v4/(ε’)2 is well described by (v2/ε’)2 up to pT ≈ 2 GeV/c
Ratio v4/v22 probes degree of thermalization
Results for different particle species reported in S. Huang’s talk later in this session
v4 of unidentified charged hadrons
A.TaranenkoPoster 212
ε’ : <v2>
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SummarySummary Differential azimuthal anisotropy measurements in Au+Au and
Cu+Cu at different beam energies and centralities indicate saturation of v2 with beam energy at RHIC
Transverse kinetic energy (KET) scaling, as well as number of constituent quark scaling, is observed in both systems at different beam energies and for KET/nq < 1 GeV and for centrality up to 60%
More in depth study needed to look into the goodness of the KET/nq scaling at low KET
Comparison between reaction plane and cumulant v2 shows
that non-flow correlations due to jet correlations exist for different centralities as from pT ~3.0 – 4.0 GeV/c. May explain the break of the NCQ scaling at KET > 1 GeV
Detailed study of different flow harmonics carried out in Run7. It is observed that v4 scales with eccentricity and with v2
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Thanks to: M. Shimomoura, H. Masui and A. Taranenko
Acknowledgements
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BACK UP
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Eccentricity scaling across colliding systemsEccentricity scaling across colliding systems
k ~ 3.1 (from data )
Eccentricity scaling observed in hydrodynamic model over a broad range of centralities v2 is observed to scale with eccentricity and across system size
Hydrodynamic model simulations (Bhalerao,
Blaizot, Borghini, Ollitrault , nucl-th/0508009)
QM 2008, Jaipur, India
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Estimate of the speed of soundEstimate of the speed of sound (I)(I)
Energy dependence at RHIC energies seem to indicate a soft equation of state. How soft ?
Estimate of cs from elliptic flow measurements can be made from
eccentricity scaled v2
Bhalerao, Blaizot, Borghini, Ollitrault , nucl-th/0508009
QM 2008, Jaipur, India
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Eccentricity scaling from PHOBOS