Toward the LHC-ALICE experiment

Hideki HamagakiCenter for Nuclear Study

University of Tokyo

2008/10/13 ATHIC2008 2

CNS+ group

• Staff Members– Hideki Hamagaki (Group leader)– Taku Gunji (Deputy leader)– Kyoichiro Ozawa

• Students:– 4 students for PhD (Doctoral course)

• 3 for RHIC-PHENIX, 1 for LHC-ALICE

– 4 students for Diploma (Master course) • 2 for LHC-ALICE, 2 for R&D of GEM detectors

2008/10/13 ATHIC2008 3

Activity of CNS in ALICE• ALICE-TRD collaboration since 2002.

– Natural choice, based on the CNS group activities at RHIC-PHENIX

• Prototype TRD beam test @ CERN (2002)– optimize the radiator, study the basic characteristics

(dE/dx, TR, gain, space charge, resolution…) and improve analysis technique (Likelihood, neural network) for eID

• First realsize TRD beam test @ CERN (2004) – performance test (chamber, readout electronics,

material budget)

• Final TRD beam-test (2007) and data analysis • 2 diploma thesis from CNS (2004, 2006)• many NIM papers

2008/10/13 ATHIC2008 4

Current Activity in ALICE-TRD• Development of Detector Control System

(DCS)– PVSS

• User interface

– FS/CE/libTRD• Handle MCM/SCSN/ORI

– distribute configuration pars.– read results, status and publish to upper layer.

• Applications (hardware access functions)

– Testbench at CNS (DCS/ROBs/Other infra.)

• Commissioning (installation/tests) @ CERN

2008/10/13 ATHIC2008 5

Physics Strategies in ALICE

• Current major physics topics of the CNS group– Quarkonia in p+p/p+A/Pb+Pb via di-electron

decays – Open heavy flavor measurement via electrons

and/or hadrons– Multiplicity measurement in p+p and Pb+Pb with

TPC

• Possible (near-future) topics– Extensive study of gluon PDF at small x --- CGC

• New: forward EMCal for direct , 0, J/,

– (Exotic) hadrons with multiple heavy quarks• Upgrade: CsI-GEM in HMPID

2008/10/13 ATHIC2008 6

Color Glass Condensate• High gluon density -> non-

linear gluon-gluon fusion

– Sizable A dependence– End of independent particle

description of partons

• Gluon PDF at x < 10-2 is very uncertain -> LHC could be an ideal machine to investigate CGC

2008/10/13 ATHIC2008 7

A Hint from RHIC data• Saturation hint at RHIC

– hadrons from d + Au by BRAHMS: RdAu ~ 0.8 for = 3.2, pT ~ 3 GeV/c (= x ~ 10-3)

• Sizable PDF modification could be possible even at central rapidity in LHC– y = 0, pT ~ 3 GeV/c (= x ~ 10-3)

– RdAu ~ 0.8 -> RPbPb ~ (0.8)2 ~ 0.6

• p+A data is crucial, probably more than at RHIC – uncertain gluon PDF at low x

– interpretation of RAA needs RpA

2008/10/13 ATHIC2008 8

Hard Collisions•Many jets in central Pb+Pb

collisions at LHC– njet/ ~ 1.7 x N(coll) ~ 1700

• n/ ~ 0.2 x N(coll) for RHIC•gluon shadowing is not taken

into account

–Most of them have low energy

•stopped in short-distance, and heat up the system

–Energetic jets•fraction grows with energy• jet quenching -- need some

distance, before stopping

X 2000X 2000

2008/10/13 ATHIC2008 9

Hard Collisions (cont.)• Complication of initial state

– With much larger number of energetic partons, time needed for thermalization may become longer at LHC?

• Space-time evolution may also become complicated

– A honeymoon between QGP and Hydro may be disturbed more often at LHC with intruding jets

– a part of lost energy may be used to heat up the fluid, while other part may simply escape the system

• This should be a quantitative question hopefully to be answered before having collisions at LHC

2008/10/13 ATHIC2008 10

Outlook

• Situation at LHC is NOT a mere extension of RHIC

• Tools and knowledge, both experimental and theoretical, acquired at RHIC can be utilized to challenge the new problems.

• Surely new findings at LHC– although I cannot guarantee it, since it is

beyond my imagination.

Low pT photon production at LHC, pT ~ 2 GeV/c

M. G. Song, D. H. Lee, B. K. Kim, B. S. Chang,

Y. Kwon, J. H. KangDepartment of Physics, Yonsei Univ.,

Korea

Old human record says…

• Genesis – In the beginning God created the heaven and

the earth. – And the earth was without form, and void; and

darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.

– And God said, Let there be light: and there was light.

– And God saw the light, that it was good: and God divided the light from the darkness.

– And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.

• Direct production in p+p

One of the best known QCD process…

Hard photon : Higher order pQCDSoft photon : Initial radiation,

Fragmentation function

Leading order diagram in perturbation theory

Really?

Direct production

Multiple collision in factorization? Higher twist?

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QOffH

QffHQ

Saturation scale? Qs

~ 1/Q2

RHIC Qs ~ 1 GeV LHC Qs ~ 2-3 GeV

Why very low mass dileptons?

* e+e- , R H Dalitz 1951 Proc. Phys. Soc. A 64 667-669

• AND we can avoid 0 background!e-

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phase space factorform factorinvariant mass of virtual photon

invariant mass of Dalitz pair

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invariant mass of virtual photon

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      web pages created by  Pier-Luigi Barberis  for 

ALICE  Experiment

Particle identification by ALICE

TRD(Transition Radiation Detector)

• |η|<0.9, 45°<θ<135°

• 18 supermodules in Φ sector

• 6 Radial layers

• 5 z-longitudinal stack

total 540 chambers

750m² active area

28m³ of gas

• In total 1.18 million read-out

channels

Tsukuba group activities for LHC-ALICE

Transition Radiation Detector(TRD)

Construction/Installation/Commissioning/Detector-control/Test-experiment/Analysiswith Heidelberg, GSI, Frankfurt, Muenster

groups•Outside of TPC, inside of TOF •Electron ID & high pT hadron measurement•Online tracking & higher-level online trigger•J/, , jet, di-jet, mini-jet trigger

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M. Konno (P.D.)D. Sakata (M2)M. Sano (M2)

Final Test Beam experiment for TRDjust before installation in ALICE

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Chamber with read-out electronics

Super Module

M. Konno (P.D.)R. Tanabe (D2)K. Watanabe (D1)H. Yokoyama (M1)

Development of Detector Control System for TRD

H.V. control, Front-end Electronics (FEE) control and error log

Hadron Calorimeter Project (JCAL) for ALICEfrom Particle Identification to Parton Identification

Total Energy measurement of Jet Jet Trigger capabilityGluon/Quark Jet separation

This Project is approved to do the detector R&D and and to make asmall proto-type for ALICE.

dd

Particle distribution in Jetswith PYTHIA

Detector Simulationwith GEANT

0

-10

10superimposed PYTHIA events

5.5 TeV Pb+Pb central Event

Photon detector test with LED:

MAPMT,APD, MPPC

PRL 94 (2005) 171802

Jet-Tomography : hadron-hadron, direct gamma-hadron, electron-hadron, identified hadron correlation, two-particle, three-particle correlation, mach-cone, ridge analysis, jet-reconstruction, jet-identification

Single (identified) spectra (RAA), event anisotropy (v1, v2) analysis : reaction plane

QGP in p+p collisions : <pT>, v2, HBT, Jet-shape, fluctuation, correlation, etc… vs Multiplicity, Geometry

Staff 三明康郎 Yasuo Miake江角晋一 ShinIchi Esumi中條達也 Tatsuya Chujo稲葉基 Motoi Inaba金野正裕 Masahiro Konno

（ technical ） 加藤純雄 Sumio Katou（ secretary ） 酒井初芽 Hatsume SakaiDoctor course students 下村真弥 Maya Shimomura

三木健太朗 Kentaro Miki池田義雅 Yoshimasa

Ikeda田辺 嶺 Rei Tanabe渡邊健悟 Kengo Watanabe

Master course students 坂田洞察 Dousatu Sakata佐野正人 Masato Sano横山広樹 Hiroki Yokoyama梶谷緑 Midori Kajigaya浜田英太郎 Eitaro Hamada塩原尚希 Naoki Shiohara木村瑞希 Mizuki Kimura轟木貴人 Takahito Todoroki

Undergraduate students 常鵬 Chang Peng関根祐輝 Yuki Sekine竹内理将 Toshimasa

Takeuchi

Univ. of Tsukuba (High-Energy Heavy-Ion Experimental) Group