Back-to back jetwith parton ID
as a probe of QGP
Proposal of small addition to ALICEin order to enhance physics capability

Yasuo MIAKE
Univ. of Tsukuba
D. SakataS. Esumi
H. Yokoyama
Dec.2008, Wuhan

1Major Two Discoveries on
Soft & Hard at RHIC

pedestal and flow
subtracted

Hadron✓Large elliptic flow
• hydro + recombination

QGP

Universal quark distribution; wDec.2008, Wuhanw ∝ (1+ 2v 2,q cos2φ )✓Jet quench
272

Shoulders at ΔΦ＝π

1.1

PHENIX, arXiv:0705.3238 [nucl-ex]✓Shoulders appear at lower momentum.
✓Location & <pt> of shoulder seem to be independent ofcentrality and pt.
➡Shock wave / Mach Cone?

Dec.2008, Wuhan

3

Shock Wave from Bevalac
From slides shown by S. Nagamiya at Tamura Symposium, Nov. 2008

W. Greiner!s proposal."✓I was very excited with this idea,
Dec.2008, Wuhan

when I was a grad. student.

4

Wish jets to penetrate !
V.S. Pantuev, arXiv:hep-ph/0701.1882v1

STAR, arXiv:nucl-ex/0701074✓Claims• Stopped parton is the source ofridge as well as Mach cone.
• This happens only at the surface• There should be velocity boost at
the ridge region (pi,K,p)• v3 components independent ofR.P.

Dec.2008, Wuhan

I wish to have jets with higher energy!

5

If we have higher energy
jets,
V.S. Pantuev, arXiv:hep-ph/0701.1882v1✓Mach cone with awayside jet.

✓Higher, the better;• Clear separation inmomentum and φ

Dec.2008, Wuhan

6

Jet Tomography
Jet Tomography

Positron EmissionTomography

M. Gyulassy ?

✓Final tool to provestructure of the densematterDec.2008, Wuhan

7

View from RHICians✓Nothing muchRHICLHC√ sNN (GeV)2005500

T/Tc

1.9

3.0-4.2ε(GeV/fm3)

515-60τQGP (fm/c)

2-4>10changes from what
we see at RHIC.

✓Nevertheless,• Larger/longer QGP• High pt jets become
available!

Dec.2008, Wuhan

8

Plenty of high pt jets

✓Many orders ofmagnitude!

Dec.2008, Wuhan

9

QGP made of soft particles✓QGP with T˜a few 100 MeV
is made of soft particles.

• Meas. of soft/low pt particles
is a must for the property ofQGP.

✓As a probe of QGP, high pt
parton is important✓In other words, modification ofAnimation by Jeffery Mitchell (Brookhaven NationalLaboratory). Simulation by the UrQMD CollaborationDec.2008, Wuhan

soft particles with high energy
jet is what we want to study.

10

CMS Heavy Ion Program
Overview:
CMS has a broad heavy ion physics program- precision tracking |η| < 2.5- muon identification |η| < 2.5- high-res calorimetry |η| < 5- forward coverage
CMS expects to excel at- photon-tagged jet measurements(FF modifications)- quarkonium measurements

John Harris (Yale)US Members:
University of California at Davis
University of Illinois at Chicago
University of Iowa
University of Kansas
Los Alamos National Laboratory
University of Maryland
MIT
University of Minnesota
Rice University
Vanderbilt University

Tamura Symposium, U. T. – Austin, 20 – 22 Nov. 2008

ATLAS Heavy Ion Program
Overview:
ATLAS has a broad heavy ion physics program- excels at jet and photon measurements

Jets- reconstruct jets in a large kinematical range
ET > 40 GeV and |η|<5- perform key fragmentation measurements- jet shape and FF modifications- multi-jet studies

US Members:
Brookhaven National LabColumbia University
Iowa State University
Stony Brook University

Photons- isolate / measure photons in large range, ET > 10 GeV and |η|<2.5- unique calorimeter design allows additional rejection beyond isolation
John Harris (Yale)

Tamura Symposium, U. T. – Austin, 20 – 22 Nov. 2008

ALICE – the Heavy Ion Experiment
ALICE is a versatile, heavy ion detector at the LHC
Overview:
Soft Probes – “ala RHIC”• Expansion dynamics different from RHIC
• Soft physics measurements ala RHIC+ extended PID• Day 1 physics +Hard Probes – Jet Quenching• Jets, γ , pi-zeros, leading particles to large pT
Hard Probes – Heavy Quarks• Displaced vertices (Do → K- π+) from TPC/ITS• Electrons in Transition Radiation Detector (TRD)

Hard Probes – Quarkonia•

J/ψ, ϒ, ϒ’ (excellent), ϒ’’(2-3 yrs),

John Harris (Yale)

ψ’ ???

US Members:Cal. St. U. – San Luis Obispo
Creighton University
University of Houston
Lawrence Berkeley Nat. Lab
Lawrence Livermore Nat. Lab
Oak Ridge National Lab
Ohio State University
Purdue University
University of Tennessee
Wayne State University
Yale University
Affiliated US Member:
University of Texas – Austin

Tamura Symposium, U. T. – Austin, 20 – 22 Nov. 2008

J-Cal (EM)✓J-Cal (EM) for back-to back

ALICE EMCALjets in ALICE➡ Define back-to back jets
➡ Trigger back-to back jets

✓Why back-to back jets?
• Origins clean• Kinematically clean➡ Energy balance➡ back-to back in phi✓Physics Goal
J-Cal
J as Jet,Japanese,Dec.2008, Wuhan• Modification of soft particles
EMCAL
˜1 supermodule(ΔΦ,Δη)˜(0.4,0.4)

with high E jet➡ Mach Cone, Ridge, etc• Tomography of QGP14

Control variables requiredfor Heavy Ion Exp.
✓Since heavy ion collisions is so complicated,while there is no ʻstandard modelʼ, we needto measure heavy ion collisions w. many control
variables.

• Centrality / impact parameter of collisions• Reaction Plane Angle• Yet, another control variable for the next
generation experiments ;→ Jet Axis
Dec.2008, Wuhan

15

Possibility of Parton ID
CDF, PRL94(2005)171802✓As a new generationexp., from Particle ID toParton ID !

• According to CDF exp.,
charged/neutral works

gluon jet✓Might be very difficult inquark jet

heavy ion environment✓Nevertheless, challenge!
✓It becomes feasible forhigher pt jet
Dec.2008, Wuhan

16

Technical Challenge✓Backgrounds !
• A lot of mini-jets may sweep away
the jet structure.

✓Keys are,• higher the jet energy, S/N ratio
improves➡OK as a probe of QGP• kinematical cleaness of di-jets
structure improves the S/N• But, higher the jet energy, the ratedrops !
➡Need optimization !

Simulation activities going on→ Talks by D. Sakata, S. Esumi, H. Yokoyama
Dec.2008, Wuhan

17

Rates and Our Goal
From slides shown by J. Harris at Tamura Symposium, Nov. 2008

✓1 month running/year✓104 events/year✓Using Day-1 ALICE withJ-Cal• Establish Dijets Axis
up to100˜150 GeV
Full Dijets reconstruction
by EMCAL+JCALThanks – Peter Jacobs
Dec.2008, Wuhan

18

Clean Kinematics
φ1PYTHIA8

ΦJET1-ΦJET2✓We want a clean back-to

pt = 40 GeV/c80
120back jets as a probe.

• back-to back in φφ2➡φ resolution is the key
phibalEntries
10
Mean
102.7
RMS
45.29

phi vs pTHat

RMS of (φ1-φ2)

0.5charged0.4

0.30.2Visible

0.100Dec.2008, Wuhan

20406080100120pt [GeV/c]

14016018020019Technical details

W. Current Our Budget

˜ 1 Super Module
16 x 16 =256 modules(ΔΦ,Δη)˜(0.4,0.4)
4 towers/module

11 super moduleΔΦ=110o (~1.9 rad)|η|<0.7✓We like to increase #ofmod. by sacrificing readouts

1 super module=12 x 24=288 modules
Dec.2008, Wuhan➡for larger yields and for jet
broadening✓Why not with PHOS?

➡Too narrow in phi for jet finding

20

Budget (Grant in Aid,JSPS)
20082011
トリガー導入陽子・陽子衝突における測定と研究
鉛・鉛衝突における測定と研究

第１モジュール

システムテスト

2012

測定器
完成

検出器製作

開発・試験
個別要素試験

2010
搬入

テスト
実験

設計計算

2009

第２モジュール

ｐｐ物理解析・評価

成果発表

PbPb物理解析・評価

第３モジュール

Tomography解析

最終製作図面
第４モジュール

トリガープログラム試験

GEANT4開発

2008.4.1現在

解析プログラム開発

トリガープログラム開発

D1 渡邊健悟
M2 佐野正人
M2 坂田洞察M1 横山広樹M1 浜田英太郎
M1 梶谷緑M1 轟木
M1 木村瑞希✓ Total of ≲1 M$ in 5 yrs✓ T. Chujo, Y. Sekine, R.Takeuchi visits Wayne State next week.
✓ We are looking for a Post Doc for J-Cal.
Dec.2008, Wuhan

21

Summary✓J-Cal (EM) for back-to back jets in ALICE➡Define back-to back jets
➡Trigger back-to back jets
➡Yet, another control variable ; jet axis

✓Physics Goal
• Modification of soft particles with high E jet➡Mach Cone, Ridge, etc• Tomography of QGP✓Need your support/help !!!
• Rate is important → More money, more coverage!
• We have just started !
• We are looking for a PostDoc
Dec.2008, Wuhan

22

Now, paperback ($80)

Nov., 2008,Tamura Symposum, Austin23