Charge asymmetric correlation measurement
as a possible signature of Local Parity Violationin 200GeV Au+Au collisions at RHIC-PHENIX
ShinIchi Esumi for the PHENIX collaboration
Inst. of Physics, Univ. of Tsukuba

CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba1

L or B

directed plane Φ1 (spectators) : Global P.V.
elliptic plane Φ2 (participants) : Local P.V.

This is two particle correlation
measurement with respect to thereaction plane <cos(φA+φB-2ΦR.P.)>,
which is sensitive to the local parityviolation, but this variable would be
affected by many other effects.
Therefore we are not intending to claim
an observation of the violation, but justto present the measured correlation
parameter.
Ys1!1 c2

c1!2

Reaction
Plane Xs2
v1= 0 , Bin ≈ Bout
CPODD workshop at BNL, 25/Jun/2012

acceptance correction with event mixing
reaction plane resolution correction
ShinIchi Esumi, Univ. of Tsukuba2

dN/dη

ηCharged Particle Tracks|η|<0.35, π/2 x 2 arms
Central Arm Spectrometer (DC,PCs)
Mid Reaction Plane
1.0<|η|<2.8, 0<φ<2πReaction Plane Detector (RXN)
Forward Reaction Plane
3.0<|η|<3.8, 0<φ<2π
Beam Beam Counter (BBC)Muon Piston Calorimeter (MPC)
CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

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Event mixing with fine bin in laboratory R.P. angle Φ{2}{forward η}

φB
φA(50, 49, 48, …)
x π/50Φ{2}R.P. angle
determinedat forward η(1, 2, 3, …)
x π/50For a given particle φA in an eventwith Φ{2}R.P. angle, another particle
φB is taken from a different eventwith a similar Φ{2}R.P. angle.

CPODD workshop at BNL, 25/Jun/2012

event mixing incentrality: 10 bins [0-100%]z-vertex: 10 bins [-30~30cm]
reaction plane: 50 bins [−π/2∼π/2]
mixed event within the same
event class of (cent, z-vtx, Φ{2}R.P.)
in order to take into account theacceptance as well as residual
flow effects to be removed.
* measure FAB=<cos(φA+φB-2Φ{2}R.P.)>and for F+−, F++ and F−−
for both real and mixed pairs* take a difference between real
and mixed, then correct for R.P.
resolution: (Freal-Fmixed) / ResR.P.

ShinIchi Esumi, Univ. of Tsukuba

4

Centrality dependence−aAaB

negative values for like sign pairs
suppressed magnitude for un-like sign pairs in central
CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

5

pT dependence

correlations goes up at higher pTstronger signal for peripheral
CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

6Comparison with STAR resultscomparable to STARmeasurements
CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

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AMPT simulation (with string melting)<cos(φA+φB-2ΦRP)>(%)
1(−,−) pair(+,+) paircentrality
0-10%

10-20%

pT > 0.5GeV/c cut(+,−) pair20-40%

40-60%

60-93%

0-1024 (GeV/c)similar magnitude for like-sign pairs ~0.2% at 2GeV/cnegative values also for un-like-sign pairssome similarity (+− > ++,−−) to experimental data
CPODD workshop at BNL, 25/Jun/2012<pT> =(pT1+pT2)/2 (GeV/c)

ShinIchi Esumi, Univ. of Tsukuba8Comparison with LHC results
S. A. Voloshin, Phys. Rev. C 70, 057901 (2004).

STAR Collaboration: Phys. Rev. Lett. 81, 251601 (2009)STAR Collaboration: Phys. Rev. C81, 054908 (2010)

P. Christakoglou, QM11

very similar results between RHIC and LHC energies

CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

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smaller signal for a given pT
at LHC than at RHIC?

Comparison with LHC results--- pT dependence ---P. Christakoglou, QM11CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

10Summary
Charge dependences of the 2-particle and R.P. correlation
are observed similarly in various experimental studies…
Simulations can not easily explain the measurements…

CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

11Collective expansion and freeze-out
photons

hadrons

arXiv:1105.4126

v2

v2 ofhadrons

quark
coalescencehydroexpansionenergyloss

arXiv:1203.2644

CPODD workshop at BNL, 25/Jun/2012

thermal photon (low pT)
surprisingly large v2
prompt photons (high pT)
reasonably small

v2 of
direct photons

ShinIchi Esumi, Univ. of Tsukuba

12Initial fluctuation followed by collective expansion
WMAP

centralperipheral

initial density distribution
PHENIX

determination of initial conditions andhydro-dynamic parameters of QGP

PRL107, 252301 (2011)

CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

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Identified particle higher order event anisotropy

CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

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Reaction plane (path length) dependent energy loss--- one of dominant sources of v2 at high pT ---thickness dependenceof penetration is more
dominant thantangential surface
emission.

QM04: STAR

CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

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200GeV Au+Au -> h-h (run7)c2(data) - c2(flow)

in-planetrigger selection(5) φs=[0,1]π/8(4) φs=[-1,0]π/8(pTTrig=2~4GeV/c, pTAsso=1~2GeV/c)

mid-central : 20-50%
(1)

(8)

(2)

(6) φs=[1,2]π/8(7) φs=[2,3]π/8(8) φs=[3,4]π/8(3) φs=[-2,-1]π/8

in-plane
associate
regions

(3)

(6)

(4)

(5)

(5)

(4)

(6)

(3)

(7)

(2) φs=[-3,-2]π/8(1) φs=[-4,-3]π/8(7)in-plane(2)(8)

strong preference ofassociate particle
emission towards thein-plane direction(1)

φs = φTrig. − ΦR.P.
[−π/2,π/2]

out-of-plane
trigger selection

average

PHENIX preliminary

significant

Δφ = φAsso. − φTrig. (rad)CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

not significant comparedwith systematic errors

16Observed left/right asymmetry remains
after “the usual/normal” v3 subtraction.
Trigger angle
selection w.r.t.
Φ2 separately
for left(up) /right(down)

out-of-plane
trigger case

Trig.

Trigger angle
selected 2-part.
corr. data areplotted in polar
coordinate byrotating Φ2 R.P.
angle as X-axis.
Flow subtracted
yield is shown
radially with base
line.

Trig.

in-planetrigger case

200GeV Au+Au -> h-h(pTTrig=2~4, pTAsso=1~2GeV/c)v2(v4{Φ2})-only subtraction
PHENIX preliminary

Φ2 R.P.

Φ2 R.P.

Trig.
Trig.

surface dominancepenetration dominanceTwo competing processes seen
CPODD workshop at BNL, 25/Jun/2012

ShinIchi Esumi, Univ. of Tsukuba

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