Summary: QGP Meet’06

The tradition continues:

Emergence of Subhashis as the GeNext Organizer-in-Chief:&Establishment of Bedang, Vikash,& Zubayer as the GeNext organizers.

Subhashis tried to give an excuse about starting the meeting starting on a Sunday.

But this Sunday it was Vishma’s birth-day (Vishma-asthami). And in any case day-names are a western aberration, Indians believed in “tithi”s (number of the day).

Ashis Chaudhuri: Valiant Effort to tackle

a very tough & challenging problem.• Viscousity: Irreversible transfer of momentum

from points where velocity is large to where it is small.

Raimond Snellings•Excellent (Near Complete Review!): Anisotropy of Initial State & Multiple Interactions.

•The interactions could also be the radiation of gluons/collisions as a jet traversed the plasma. Different from hydrodynanmic flow.

•Validity of hydrodynamics.- Flow develops early in the collision.

•Failure of hydrodynamics & recombination model

•Higher order harmonics.

•Parton cascade models can give flow only if the parton cross-sections are raised by a factor of 50 or so.

Manifestations of Collective Flow (radial and anisotropic)

x

y

x

y

z

x

• Only type of transverse flow in central collision (b=0) is radial flow – Integrates pressure history over complete

expansion phase

• Elliptic flow (v2) , hexadecupole flow (v4) , v6, … caused by anisotropic initial overlap region (b > 0)– More weight towards early stage of

expansion.

• Directed flow (v1) , sensitive to earliest collision stage (b > 0)– pre-equilibrium at forward rapidity, at

midrapidity perhaps different origin

Dependence on the EOS!• EoS Q and EoS T

(both have significant softening) do provide the best description of the magnitude of the mass scaling in v2(pt)

• The lattice inspired EoS (EoS qp) in ideal hydro does as poorly as a hadron gas EoS!

Pasi Huovinen, arXiv:nucl-th/0505036

STAR QM2001

Mass dependence

• Identified particle elliptic flow at low pt

– Mass dependence in accordance with collective flow. QGP equation of state (phase transition) provides best description

Hydro calculation: P. Huovinen et. al.

• Top RHIC energies at dip in v2

• Hydro prediction for lower energies v2 increases?

• the radial flow <v> increases monotonically with beam energy (pion multiplicity at fixed impact parameter), is the slope of v2(pt) expected to increase for ideal hydro?

• Where are the 62 GeV calculations?

Adapted from P.F. Kolb and U. Heinz, in Quark Gluon Plasma, nucl-th/0305084

Energy dependence of v2(pt)

Is the slope of v2(pt) more sensitive to the energy dependence?

Munshi Golam Mustafa

Comparison to NLO pQCD

NLO pQCD with AKK FF relatively better than KKP for the p+pbar data

AKK differ from KKP, in the way the light flavor FF are obtained

NLO pQCD with Kretzer FF inconsistent with data

NLO pQCD with KKP FF inconsistent with the p+pbar data

Kretzer differ from KKP, in the gluon to fragmentation

Pawan Kumar Netrakanti

Scaling in particle production

e+ and e- does not have a parton distribution function.There will be a (sNN )2 multiplied to cross-section in e+e- collisions. For p+p collisions n ~ 6.5 for , p

(pbar)

   

System expansion: Initial vs Final Size

Proton initial size = 0.89 fm from e-scattering

Smooth expansion of the system from p+p to Au+Au

… but not trivial

AuAu: system expands

pp (dAu): no or less expansion

CuCu 200 AGeV

is crucial as it helps

In understanding

the “missing link”

Collisions at 200GeV only

STAR PRELIMINARY

Debashis Das

Proportionalto dNch/d

Freeze out a constant density

Also seeRef :CERES PRLNucl-ex/0207008

STAR PRELIMINARY

Constant Freeze out density hypothesis

At high energies: Baryon density << Pion density

Pion rapidity density freeze out volume (Rs

2RL)

Velocities ( zero at initial time t0 ) which start differing over extended volume by the end of the QGP phase, become almost identical at the end of hadronic phase.

nucl-th/0511079 –Rupa Chatterjee, Evan S. Frodermann, Ulrich Heinzand Dinesh K.Srivastava .

.

Rupa Chatterjee

Fluid velocity along the constant energy density contour for =q(for

QGP phase),=h (for mixed phase) and =f (for hadronic phase ) for x (y=0) (dashed curve) and y (x=0) (solid curve) .

•v2 for thermal photons from 200 AGeV Au+Au collision is shown by the red curve.

.Quark and hadronic contributions to v2 are shown separately. •v2 for pion is also shown in comparison with hadronic v2. • pion v2 tracks the hadronic v2.

nucl-th/0511079

Impact parameter dependence of the elliptic flow

Impact parameter are chosen to roughly correspond tocollision centralities of 0-10%(b=3 fm), 10-20%(b=5.4 fm), 20-30%(b=7 fm), 30-40% (b=8.3 fm), 40-50% (b=9.4 fm), and 50-60% (b=10.4) .

nucl-th/0511079

Jajati Kesari Nayak

Radial expansion?

No radial flow!

Pradip Kumar Roy

Collisional e-loss;Careful evaluation

R_AA?

Results (contd..)

Participant number dependence ofelectromagnetic fraction of total energy.

No significance dependence of electromagnetic fraction on collision centrality. Tells about the particle production mechanism.

STAR Preliminary

STAR Preliminary

The centrality dependence of ET/Nch

Hydrodynamic flow effect is reflectedin the peripheral collisions.

If the expansion is isentropic, dNch/dwill remain constant, whereas dET/dwill decrease due to the performance oflongitudinal work.

R. Sahoo

Results (contd..)

Excitation function of ET/Nch

Production of constant transverse energy per charge particle (~ 0.8 GeV) has been observed from AGS to RHIC.

Energy pumped into the systemgoes for particle production, insteadof increasing energy per particle.

Recall: Jean Cleymans & Krzysztof Redlich Freeze-out along <E>/N= 1 GeV.

Pseudorapidity Distribution of photons (CuCu 200 GeV)

STAR preliminary

Upper limit on systematic Error ~ 24%

Monika Sharma

?

Pseudorapidity Distribution of photons (CuCu 200 GeV)

STAR preliminary

Upper limit on systematic Error ~ 24%

Monika Sharma

Comparison of results from PHOBOS (Charge Particles)

Charge particle production at forward rapidities are independent of system size

Are these outcome of only soft-collisions? Can you check if <pT> is smaller than at central rapidity?

P. Chakrabory; Also quark number susceptibility

Jan-e Alam

What aboutP_T distribution??????

Summary

Detectors at forward rapidity region provide the experiment : centrality and trigger Forward rapidity region provides rich information on particle production certain universality (species, energy) observed Forward rapidity region provides information on nuclear stopping, baryon transport and energy for particle production Forward rapidity provides a chance to scan the QCD phase diagram Forward rapidity provides the best place to study the possible initial conditions at RHIC : CGCForward rapidity provides testing ground for NLO pQCD

Measurements at forward rapidity (kinematical limits and detector constraints) are also an experimental challenge

Bedanga Mohanty

????

Sudhir Bhardwaj; Important step towards measuring v_2

MUON Spectrometer aims to measure the signals

• As a function of centrality – Identify suppression/enhancement patterns

• As a fuction of the size of the colliding system– Distinguish between normal and anomalous suppression

• For all onium species– Different survival probabilities probe the temp of the system

• As a function of pt– Disentangle QGP model

• With good vertex resolution– Distinguish between prompt and secondary charmonium

• Verses the reaction plane– Distinguish between Glauber and Comover absorption

• Together with other QGP signals

MUON Spectrometer aims to measure the signals

• As a function of centrality – Identify suppression/enhancement patterns

• As a fuction of the size of the colliding system– Distinguish between normal and anomalous suppression

• For all onium species– Different survival probabilities probe the temp of the system

• As a function of pt– Disentangle QGP model

• With good vertex resolution– Distinguish between prompt and secondary charmonium

• Verses the reaction plane– Distinguish between Glauber and Comover absorption

• Together with other QGP signals

Signal Normalization

• Drell-Yan above 4 GeV/c2 (NA38/NA50)– At LHC, D-Y completely drowned into the background from

semi-leptonic decay of open charm and open beauty• Open Charm (bottom) cross-section

– Charm (beauty) thermal production can increase dramatically in QGP with higher temp

– Shadowing and/or quenching – suppression of high pt charm/bottom.

=> Reference dependent on QGP properties• Minimum Bias method

– Centrality dependence of the efficiency for Dimuon measurement – accuracy => error

• No Normalization– Careful estimation of systematic error

MUON Spectrometer aims to measure the signals

• As a function of centrality – Identify suppression/enhancement patterns

• As a fuction of the size of the colliding system– Distinguish between normal and anomalous suppression

• For all onium species– Different survival probabilities probe the temp of the system

• As a function of pt– Disentangle QGP model

• With good vertex resolution– Distinguish between prompt and secondary charmonium

• Verses the reaction plane– Distinguish between Glauber and Comover absorption

• Together with other QGP signalsSukalyan Chattopadhyay

Signal Normalization

• Drell-Yan above 4 GeV/c2 (NA38/NA50)– At LHC, D-Y completely drowned into the background from

semi-leptonic decay of open charm and open beauty• Open Charm (bottom) cross-section

– Charm (beauty) thermal production can increase dramatically in QGP with higher temp

– Shadowing and/or quenching – suppression of high pt charm/bottom.

=> Reference dependent on QGP properties• Minimum Bias method

– Centrality dependence of the efficiency for Dimuon measurement – accuracy => error

• No Normalization– Careful estimation of systematic error

Production in progressProduction in progress