wuhan meeting, 4-6/dec/2008shinichi esumi, univ. of tsukuba1 jet study at rhic and jet...

Wuhan meeting, 4-6/Dec/2008 ShinIchi Esumi, Univ. of Tsukuba 1

Jet study at RHIC and Jet reconstruction study at LHC energy for ALICE experiment

ShinIchi Esumi Inst. of Physics, Univ. of Tsukuba, Japan

ContentsJet-Suppression and ModificationMach-cone and Ridge w.r.t. Reaction PlaneJet reconstruction study with pythia at LHC energyParticle identification to Jet identification


RHIC 200GeV SPS 17GeVRHIC 62GeV

PHENIXnucl-ex/0611019

S.Kniege, ISMD 2007

jet

p p

Au Au

Jet suppression modification with 2-particle correlation


p+p, peripheral Au+Au central Au+Au PHENIX QM08

d+Au, 200 GeV STAR QM06

(rad)

RidgeRidge

“jet”

Au+Au, 200 GeV


STAR Preliminary

TInclusive ~ TShoulder ~ TRidge < TJet

QM06

QM08

ridgejet

inclusive

< <

Both ridge and shoulder <pT> are almost independent with centrality and trigger pT selections.It’s just like a bulk matter… suspicious on BG(bulk) subtraction… but this is what we see…


PHENIX preliminary

Identified 0 trigger with associate hadron

Width does not change with centrality similar to charged hadron triggered case.Surface bias (as in 2+1 correlation case)

7-9 (X) 1-20-20%

7-9 (X) 4-50-20%

7-9 (X) 4-520-40%

7-9 (X) 4-540-60%

7-9 (X) 4-560-90%

7-9 (X) 6-840-60%

QM08 PHENIX


1/N

trig

dN

/d

(A.U

.)

pT, photon GeV

Per-

Trig

ger

Yiel

d (A

.U.)

Run 6 p+p @ 200 GeV

0

Run 7 Au+Au @ 200 GeV, cent=0~20%, preliminary

Direct trigger with associate hadronQM08 PHENIX

p+p: Consistent w

ith trigger photon carrying the full jet energy, aw

ay side jets are sim

ilar between

0 and triggers.

Need m

ore studies and statistics for A

u+Au case.

Run 4/5 p+p/Au+Au @ 200 GeV


3<pTtrig<4GeV/c & 1.0<pT

asso<1.5GeV/c 20-60%STAR

= associate - trigger (rad)

Jet modification and geometry(and v2)

QM08: STAR, PHENIX

QM04: STAR

Mach-cone shape depends on R.P. angle.Mach-cone is a source of of v2


STAR Preliminary

Ridge

Jet

3<pTtrig<4, 1.5<pT

trig<2.0 GeV/c

QM08 STAR

STAR

(rad)

RidgeRidge

“jet”Au+Au, 200 GeV

Ridge shape depends on R.P. angle.Ridge is a source of of v2

Jet does not depends on itJet reduces v2

(rad)

PYTHIA p+p

away side (in d) of one di-jet can be near side (in d) of another di-jet


ASSO.-TRIG. < 0

ASSO.-TRIG. > 0

in-pl.

in-pl.

out-of-pl.

out-of-pl.


In order to continue and develop the Jet tomography study in Heavy-Ion collisions at LHC, we have started to consider building a new calorimeter in ALICE at azimuthally opposite side of the existing EMcal as Yasuo mentioned.

We use control variables like centrality and reaction plane, which have been utilized in the previous Heavy-Ion experiments, which Dousatsu has discussed. We also like to treat a high pT jet axis of an event as another control variable for Heavy-Ion collisions.

For this purpose, I just have started to play with PYTHIA p+p events to test the jet finding and reconstruction in the Heavy-Ion collision environment (by superposition of many p+p events) for the detector to be built. Hiroki/Dousatsu will continue to talk about his studies on jets and di-jets using HYDJET model. I’m still in the beginning and learning phase, so I appreciate your suggestions and comments.


Jet Finder/Reconstruction study for Heavy Ion Collision Environment

* superposition of PYTHIA 5.5TeV p+p Min.Bias events N(p+p)max~ 200 events (~35k final particles/event, dNch/d~2000)

* inclusion of single hard scattered p+p event with various pT

hat selections (> 20 ~ 90 GeV)

* modification of jet finding routine (CellJet) in pythia8.107 with event-by-event BG subtraction, based on an idea from CMS paper E.P.J C50, 117-123(2007)

(1) get average energy of cell in [] space with step of (0.1,0.1) for each event(2) subtract the average energy from all cells, ignore negative cells(3) find the jet seeds with cell energy of more than 5GeV(4) sum-up all the cell energies within a cone of (d+d<0.25 from each seed(5) define the jet with the total energy above 20GeV(6) recalculate the average energy by excluding the found jet cones(7) repeat steps (2)-(6) for 3 times


single p+p event pThat > 40 GeV 14 min.bias p+p events added

(Pb+Pb peripheral)

pTm

ax

pTmax



(Pb+Pb central)

pTm

ax

pTmax

pT max pT

max


Jet pTSUM (GeV/c)

pythia8.107 p+p 5.5TeV superimposed on Pb+Pb min.bias (pT

hatmin> 20 / 40 / 60 / 80 GeV)

triggered p+p event+ superimposed min. bias Pb+Pb

min. bias Pb+Pb alone (BG)

triggered p+p eventalone

BG subtracted signal

dN/d

p T (a

.u.)


(A) solid lines(B) dashed lines

pTHat

Min=20GeV pTHat

Min=40GeV pTHat

Min=60GeV pTHat

Min=80GeV

(C) solid lines(A-B) points

pTSUM (GeV/c) N(p+p) = 0~50N(p+p) = 50~100N(p+p) = 100~150N(p+p) = 150~200

dN/d

p T (a

.u.)

pTSUM (GeV/c)

(A) triggered p+p event + superimposed Pb+Pb(B) superimposed Pb+Pb alone(C) triggered p+p event alone(A-B) BG subtracted signal


pTSum > 30GeV

pTSum > 50GeV

pTSum > 70GeV

pTSum > 90GeV

Signal to BG noise ratio increases with increasing the jet energy

Increased efficiency of jet finding, which could be caused by the upward BG fluctuation…# of found jet in p+p is the reference.

(A-B

) / (C

)(B

G s

ubtra

cted

sig

nal)

/(tr

igge

red

p+p

even

t alo

ne)

Npart ~ 2*N(p+p)

(A

) / (C

)(tr

igge

red

p+p

even

t + s

uper

impo

sed

Pb+

Pb)

/

(tri

gger

ed p

+p e

vent

alo

ne)

Signal + BG

Signal

Output

Input


pythia8.107 p+p 5.5TeV (pT

hatmin>20GeV)

p+p event

same p+p event+ superimposed min. bias Pb+Pbby pile-up p+p events from min. bias p+p

QCD hard all qq -> qq qg -> qg gg -> gg

pTm

ax

pTmax

4

0

-4

0

Trigger(pTmax) - particle(pT>4GeV/c) correlation


p+p event


pTm

ax


pTmax

4

0

-4

0


hatmin>50GeV) Trigger(pT

max) - Jet(pT>50GeV/c) correlation


Jet pTSUM (GeV/c)

p+p Pb+Pb min.bias Pb+Pb central

RM

S w

idth

(

pT

max

) at

aw

ay s

ide

[/2

,3/

2]

QCD hard all

qq -> qqqg -> qg

gg -> gg

pythia8.107 p+p 5.5TeV Possibility of Jet Identification #1RMS width (pT

max) at away side [/2,3/2]


p+p Pb+Pb min.bias

QCD hard all

qq -> qqqg -> qg

gg -> gg

Pb+Pb central

Jet pTSUM (GeV/c)

Par

ticle

mul

tiplic

ity

with

in J

et c

one

(r<0

.25)

pythia8.107 p+p 5.5TeV Possibility of Jet Identification #2Particle multiplicity within Jet cone

RMS width of this particle multiplicity distribution within jet cone is large, therefore jet by jet identification might not be possible, however statistically feasible.


Summary

* Jet suppression and Jet modification at RHIC* Strong relation between v2 and Jet* Jet reconstruction study with pythia at LHC energy* Particle identification to Jet identification* Surface-bias (particle-particle, jet-particle and jet-jet correlation with respect to reaction plane, centrality)


(1)

(2)

(3)

(4)

(2)

(3)

(4)

(1)

Trigger particle

x(R.P.)

y

ASSO.TRIG.

In order to study the jet modification (mach-cone, ridge) and it’s relation with almond geometry in more detail…

with and without R.P. aligned event mixing

Associate particle 1

Associate particle 2


Simulation of flow subtraction for jet shape extractionpure flow + jet (~10% of total yield) modelR.P. is not biased by the embedded jets3 different shapes (which do not depend on R.P. orientation)

Shape#1, usual jet Shape#2, mach-coneShape#3, asymmetric

Reminder: we should expect the extracted jet shape should look like the jet shape above the pedestal (dashed lines, ZYAM bias).

embedded jets shape


Shape#1, usual jet Shape#2, mach-cone Shape#3, asymmetric

Event mixing method “CASE.B” used for all three cases

C2flow+jet : Points in the figures are given by

MC with pure flow + jet simulationC2

flow : Lines in the figures are given by MC with pure flow simulation

C2 =

(Rea

l pai

r) /

(Mix

ed p

air)


After the subtraction

Shape#1, usual jet Shape#2, mach-cone Shape#3, asymmetric

J =

C2(fl

ow +

jet) -

C2(fl

ow)

Non-R.P. dependence of jet shape recovered!



(Pb+Pb mid-central)

pTm

ax

pTmax



hatmin>20GeV)

p+p event


pTm

ax


pTmax

4

0

-4

0

Trigger(pTmax) - Jet(pT>20GeV/c) correlation

wuhan meeting, 4-6/dec/2008shinichi esumi, univ. of tsukuba1 jet study at rhic and jet...

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