ALICE Experiment at LHC Hiroshima University T. Horaguchi 03/18/’09 for the Recent Topics in...

ALICE Experiment at LHC

Hiroshima UniversityT. Horaguchi

03/18/’09 for the Recent Topics in Hadron Physics

Outline

• Introduction– Motivation in Quark Physics– History of Universe & QCD– Theoretical Background

• Proton-Proton collisions• Heavy Ion Collisions

– History of QGP Search– What did we learn at RHIC ?

• ALICE Experiment• Contribution from Japan• Summary & Future Plan

2009/3/18

Recent Topics in Hadron Physics @ TITECH

2


3

Introduction• Motivation in “Quark Physics”

– State of early Universe • Matter state around 10-5 s after Big Bang• Evolution of the universe• Differentiation of each interaction

– Fundamental property in Strong Interaction • Quark confinement• Quark deconfinement ?

– Property of material of deconfined partons ?

– Origin of Mass• 2 Stage Mechanism

– Mass of quarks with Higgs Mechanism– Mass of hadrons with Chiral Symmetry Breaking

• LHC with ALICE – LHC : Strong QCD Machine– ALICE : Wide purpose Heavy Ion Experiment

2009/3/18


4

History of the Universe & QCD

2009/3/18

15 by

1 by

1012 s

Birth of Life

Formation of Galaxy

Formation of Atom

Formation of Nucleus102 s

10-6 s

10-35

s

0.00s Big Bang

Inflation

Quark ConfinementAnti-Quark

AnnihilationProduction of

Quark


5

Theoretical Background

• Perturvative QCD (pQCD)– QCD (Quantum ChromoDynamics)– Basement for proton-proton & heavy ion

collisions at high energy• Lattice QCD

– Predict new state of Quark Matter• Quark Gluon Plasma (QGP)

2009/3/18

Karsch,Lect. Notes Phys. 583

(2002) 209


Proton-Proton Collisions with pQCD

• The cross section for a hard scattering process in proton-proton collisions, for example the production of a hadron “h” (pp→hX) , can be written as follows;

• The cross section can be factorize the three parts.

),(),,,(ˆ),(),( 222

21

,,

2121

21

21

21

zDxxpdxfxf

dxdxd

hfh

Xfffpp

fff

hXpp

Parton Distribution

Function (PDF)

Fragmentation Function (FF)

Subprocess cross section calculated with pQCD

2009/3/18


7

Heavy Ion Collisions

Pre-equilibriumThermalization

QGP phase?

Mixed phaseHadronization (Freeze-out) + Expansion

2009/3/18


Glauber Model

A

BSpectator

Participant

8 2009/3/18

Impact Parameter : b

• Spectator– Nucleon which do not

participate in Reaction• Participant (Npart)

– Nucleon which participates in Reaction

• Number of Binary Collisions (Ncoll)– Number of total

nucleon-nucleon collisions in heavy ion collisions

ypσσN

ypN=R

Tcoll

TAB ddd

ddd

ppinelNN

AB

//

/


9

History of QGP Search• Bevalac @LBNL

– p=0.8 GeV/A, sNN=1.8 GeV• E802/859/866 @AGS-BNL 　

– p=14.6 GeV/A, sNN=5.4 GeV• NA44/WA98 @SPS-CERN 　　

– p=160 GeV/A, sNN=17 GeV• PHENIX @RHIC-BNL

– p=100+100 GeV/A, sNN=200 GeV• ALICE @LHC-CERN

– p=2750+2750GeV/A, sNN=5500 GeV

2009/3/18

What do we learn from RHIC ?

• dense: energy loss of (even heavy) quarks– jet quenching (high pT suppression)– jet modification

• partonic: quarks’ degrees of freedom, screening– constituent quark number scaling of collective

motion– J/Y suppression

• strongly coupled: perfect fluidity– hydro-dynamical collective motion

• hot: thermally radiative– thermal (virtual) photons

2009/3/18


10


11

RHIC Outcomes: New State of Matter (1)

2009/3/18

ypσσN

ypN=R

Tcoll

TAB ddd

ddd

ppinelNN

AB

//

/

•pedestal and flow subtracted

• dense: energy loss of (even heavy) quarks– jet quenching (high pT suppression)– jet modification


12


QGP

Hadron

27

Universal quark distribution; w

w (1 2v2,q cos2)

Beam axis

x

z

ＹReaction Plan

Not Central Collision

• partonic: quarks’ degrees of freedom, screening– constituent quark number scaling of

collective motion• strongly coupled: perfect fluidity

– hydro-dynamical collective motion

2009/3/18


13


2009/3/18

• partonic: quarks’ degrees of freedom, screening– J/Y suppression

• hot: thermally radiative– thermal (virtual) photons


14

labcm mEEs 2

ALICE

CMS

LHC-b

ATLAS

labcm mEEs 2

A Large Ion Collider Experiment

• The heavy ion experiment at LHC• Collider Experiment

– Advantage:– Disadvantage : Difficulty of covering the

acceptance• Circumstance : 27km• 30 countries; ~ 100 institutes; > 1,000

membersSweden

PolandNorway

Russia

JINR

Japan BrazilRomaniaSpain/Cuba

South AfricaUSA

ChinaCroatia

ArmeniaIndia

Korea

UkraineMexico

Czech Rep.Slovak Rep.

CERNDenmark

Finland

Germany

France

Italy

GreeceUK

HungaryNetherlands

2009/3/18


15

ALICE ： “ Wide-Purpose” Detector

• Central barrel spectrometer: -0.9 < h < 0.9– Tracking and particle identification in full

azimuth– Partial coverage of HMPID, PHOS, EMCal

• Forward muon spectrometer: - 4 < h < -2.4

• Multiplicity: - 3 < h < 5.4

(charged particles)

µ arm

2009/3/18


16

ALICE (L3) Magnet + Detector Cage

2009/3/18


17

Time Projection Chamber• Main tracking device

– |h| < 0.9, full azimuth• Largest ever

– 88 m3, 10 m long, 5.6 m diameter, 570 k channels

– 3 % X0, Ne (86)/CO2 (9.5)/ N2 (4.5), O2 ~ 1 ppm

– max. 80 MB/event (after compression)

2009/3/18


18

Inner Tracking System

• Tracking (|h|< 1) + multiplicity (|h|< 2)• Si pixel/drift/strip; 2 layers each

– rf resolution: 12, 38, 20 mm

2009/3/18


19

Transition Radiation Detector

• Tracking and particle identification– |h| < 0.9, full azimuth– 400 – 600 mm resolution in rf, 23 mm in z– e/p separation > 100 at pT > 3 GeV/c

2009/3/18


20

Time of Flight

• Hadron identification– |h| < 0.9, full azimuth; 3.7 m flight path

• Multi-gap resistive plate chamber– Time resolution ~ 50 ps, 160 k channels

2009/3/18


21

High Momentum PID

• Ring imaging Cherenkov with CsI photo-cathode– gth = 1.57, |h| < 0.6, Df = 58; 11 m2, 16.1 k

channels

2009/3/18


22

Photon Spectrometer

• High granularity, high resolution EM calorimeter

• (details later)2009/3/18


23

Forward (Di-)Muon Spectrometer

• Quarkonia and heavy flavor in forward region– 2.4 < h < 4.0– Mass resolution: < 70 MeV at J/Y, < 100 MeV

at – Momentum cutoff: 4 GeV/c

2009/3/18


24

Trigger, DAQ, Offline• 1.2 GB/s (500 MB/s initially); 2.5 PB/y• Multi-layered trigger

– Central trigger processor L0, L1, L2– High level trigger

• 1 K CPU; scalable to 20 K CPU

• LHC computing grid (LCG)– Tested world wide in 2007

• whole collected data systematically reconstructed• 18 TB of reconstructed data shared world wide• 7.5 K CPU, 1 PB disks at 65 sites in 4 continents

2009/3/18


25 2009/3/18

ALICE Data Flow

DAQ

CASTOR @ T0

T0

Buffer

CAF

T1

ESDT2

T2

ESD AOD

On lineAnalysis

First Reco 2-3 Reco

User Analysis

CERN

JP-HIROHSIMA-WLCG etc.…


26

ALICE in Japan

• Full membership since 2006– Hiroshima University

• Physics primarily via photon channels• PHOS R&D and construction• “Tier 2” analysis facility

– CNS, University of Tokyo• Physics primarily via electron channels• Photon/electron trigger R&D• TRD construction

– University of Tsukuba• Physics primarily via collective behavior (?)• TRD construction• CERN branch office• J-Cal construction

2009/3/18


27

Photons Physics @ Hiroshima University

• ALICE photon spectrometer: PHOS– photons, nuetral mesons, jet tagging

• + L0, L1 trigger capability• wide coverage from 100 MeV to 100 GeV

– high eneregy resolution, high granularity• s/E ~ 3 %/E up to 100 GeV • PbWO4 crystals of 22 (1.0 RMoliere)×22×180 (20 X0)

mm3

• APD + charge sensitive pre-amplifier readout• cooled and controlled at -250.1 C

– |h| < 0.12, Df = 100 at 4.6 m• 56×64×5 modules; 17,920 channels, 12.5 t

2009/3/18


28

Photon Physics #1: Neutral Mesons

thermal ~ e-E/T

hadron decays

jet-medium interaction jet-photon conversion bremsstrahlung

pQCD processes ~ pT-n

compton scattering annihilation fragmentation

• “day-1” physics program– enough acceptance with initial 3 PHOS

modules

• higher pT reach + stronger suppression than RHIC– clearer measurement of quark energy loss– less background for direct photon

measurement

2009/3/18


29

• direct photon at RHIC: consistent with pQCD– consistent with simple p+p superposition– consistent w/ and w/o nuclear modification of

PDF– consistent w/ and w/o string fragmentation

quenching• hard photons at ALICE/LHC

– # prompt photons ~ # decay photons at > 60 GeV

– large rate up to very high pT

Photon Physics #2: pQCD Photons

K.J.Eskola et al.,NPB535 (1998) 351

F.Arleo,hep-ph/0601075 (2006)

2009/3/18


30

Quenched String Fragmentation

~ 60 % suppression at 10 GeV/c

F.Arleo,hep-ph/0707.2320 (2007)

• significant suppression of pQCD photons expected– independent measurement of quark energy

loss– less background for thermal photon

measurement

2009/3/18


31

Photon Physics #3: Thermal Photons

• RHIC outcome– radiation at 300 – 500 MeV implied

• indirect measurement via g*• cf. critical temperature ~ 170 MeV

– models not strongly constrained

• LHC prospect– direct measurement of thermal photons

• higher temperature + longer life time• reduced background due to quenching• ALICE-PHOS detector

– understanding of thermal properties of partonic system

2009/3/18


Computing @ Hiroshima University• GRID Computing• Local Cluster

– PHENIX / ALICE– Cluster

• Xeon 3.0GHz– 16node x 2cpu x

2core• Xeon X5355 2.66GHz

– 31nodex 2cpu x 4core • Xeon X5356 3.oGHz

– 20nodex2cpux2core– Storage Server

• 26TByte– Band Width

• 1GBps– OS

• SL4.4 or SLC4.5– Batch Job System

• Condor• ALICE Analysis

– Physics Simulation– Simulation for PHOS

Calibration• Production

– ALICE Full Simulation• 1G Event32

NFS

NFS

Library & Condor Server

Strage Server

Local Cluster

2009/3/18


33

Computing GRID @ Hiroshima University

• Site name– JP-HIROSHIMA-WLCG

• Site Administrator – T. Sugitate– T. Horaguchi

• Site Security Officer– T. Sugitate– T. Horaguchi

• Site Component– VOBOX– Computing Element– Storage Elemet

• ~200TByte– Monitoring– User Interface– Worker Node

• Intel Xeon5160 2cpu x 2core x 16• Network Bandwidth

– 1GBit Ethernet on SINET3• Regional Supported by ASGC in Taiwan• Possible associated Tier-1 in Lyon

WN

VOBOX

CE

SE

UI

Router

SINET-3

2009/3/18


34

J-Cal (EM) @ University of Tsukuba

• J-Cal (EM) for back-to back jets 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– Modification of soft particles

with high E jet• Mach Cone, Ridge, etc

– Tomography of QGPJ-Cal

ALICE EMCAL

J as Jet, Japanese, EMCAL

~1 supermodule(ΔΦ

,Δη) ~(0.4,0.4)

2009/3/18


35

ALICE Status and Plan• Initial configuration in 2009

– Full: ITS, TPC, HMPID, muon, trigger detectors– Partial: TRD (> 8/18), TOF (> 8/18), PHOS

(3/5)– Reduced: high level trigger (30%)

• i.e. Initially:– Almost full hadron/muoncapability– Partial electron/photon capability

• Mid-term (a few years) plan for completion– Full TRD, TOF, PHOS– EMCal– Enhanced higher level trigger 2009/3/18


36

• Vital reference for Pb+Pb– Elementary processes at unknown energy

region• s, c, b, quarkonia, …

• Own physics in p+p– Particle production mechanisms at highest ever

energy• Multiplicity, baryon transport, …

– ALICE advantages• pT coverage from < 100 MeV/c (XT < 10-5) to > 100

GeV/c• Good particle identification• Trigger capability including minimum-bias, multiplicity,

…

• Physics in high multiplicity p+p events

Initial Strategy ： p+p Physics

2009/3/18


37

Boundary Condition: LHC Schedule

• LHC start-up schedule– 2008/09 first beam– 2009/09 re-commissioning (p+p)– 2009/10 p+p, s = 10 TeV?, 1032 cm-2s-1

– 2010? Pb+Pb, sNN = 5.5 TeV, 5×1025 cm-

2s-1

• expectations in initial years– p+p s = 14 TeV, 1031 cm-2s-1 (ALICE), 107 s/y

s = 5.5 TeV, 1031 cm-2s-1, 106 s/y×1 y

– Pb+Pb sNN = 5.5 TeV, 1027 cm-2s-1, 106 s/y

– p+Pb sNN = 8.8 TeV, 1029 cm-2s-1, 106 s/y×1 y

– Ar+Ar sNN = 6.3 TeV, 1029 cm-2s-1, 106 s/y×1 y

2009/3/18


38

• Discovery of deconfined partonic matter at RHIC

• Not end of story; new prospects at LHC– global understanding of hot partonic matter

• ALICE at LHC starting in months– Uniquely suitable for hard/heavy probes– Opening new ground for “soft” photonic probes– ALICE-J in full commitment (along with RHIC)

• ALICE ： “ wide-purpose” heavy ion experiment– Broad prospect coverage + high capacity for

“unknown”• Physics harvests around corner (even in

initial p+p)

Summary & Future Plan

2009/3/18


39

Backup

2009/3/18


40Dec.2008, Wuhan

View from RHICians

• Nothing much changes from what we see at RHIC.

• Nevertheless,– Larger/longer QGP– High pt jets

become available!

RHIC LHC

√ sNN (GeV) 200 5500

T/Tc 1.9 3.0-4.2

ε(GeV/fm3) 5 15-60

τQGP (fm/c) 2-4 >10

2009/3/18

Backup (v2)


42

V2 ってなに？

ビーム軸

x

z

反応平面

非中心衝突

Ｙ

生成粒子と反応平面の為す角度 Φ

x ( 反応平面 )

Ｙ

φ

粒子の収量が、（ x 方向） > （ y 方向）なら、 v2>0

v2 は、生成される粒子の方位角方向の異方性（ Azimuthal anisotropy ）の強度をあらわしている？？？

の分布をフーリエ展開

＝

dN/d(-Ψ) = N (1 + 2v2cos(2(-Ψ)))

ex. Φ-Ψ の分布

v2 　・・・　生成粒子の反応平面に対しての楕円率

2009/3/18


43

楕円型フロー（ Elliptic Flow ）ってなに？

• フロー　・・・　粒子の集団運動• 楕円型　・・・　ｘ方向とｙ方向に流れるフローの

量が違う。

Y

XR.P.

衝突関与部の初期の幾何学的な異方性が運動量空間における方位角異方性となって検出されている。→　衝突で生成された物質の性質を反映している測定量

？？？

？？？

Y

X

λ >> R ; 等方的(Isotropic)

λ << R ; 異方的(anisotropic)

粒子の平均自由行程（ λ ）が衝突関与部の半径 Rより十分大きければ、相互作用せず、粒子は等方的に広がる。 ( 圧力勾配もうまれない )

2009/3/18


44

• QGP 中でのパートンの平均自由行程 λ が衝突関与部の半径 Rに比べて十分に小さいと、系が局所的熱平衡に達して圧力勾配をうむ粒子の運動量空間での方位角異方性– λ>> R ; isotropic 　自由ガスのように振舞う– λ<< R ; anisotropic 流体のように振舞う

もし平均自由行程（ λ ）が衝突関与部の半径 R より十分小さければ・・・

圧力勾配　小

圧力勾配　大粒子放出　大

粒子放出　小原子核の非

中心衝突では、衝突部の初期の形はアーモンド形（幾何学的異方性をもつ）

ビーム軸

x

z

反応平面

非中心衝突

Ｙ

ＱＧＰ物質の相互作用　　圧力勾配　　楕円型フロー　　 v2 が有限　v2 測定は、衝突関与部の初期の幾何学的な異方性が運動量空間における方位角異

方性となって検出されている。→　衝突で生成された物質の性質を反映している測定量

ｖ２は衝突関与部の楕円率と１対１対応と考えられていた。

2009/3/18


45

相互作用があればｖ 2 は、発達する可能性がある。

衝突後の時間発展の描像

衝突

QGP

パートン熱平衡

化学的凍結

熱的凍結

ハドロン化ｖ 2 が増える。

v ２は、いつ作られたのか？

2009/3/18


46

反応関与部の楕円率 ( 説明 )

22

22 -

xy

xy

Eccentricity =

Participant Eccentricity 　がより実験室の状態に近い。

2009/3/18


47

Elliptic flow @ Low pT

RHIC 実験では様々な粒子の v2 が

　　測定され、有限な値を示している！

運動量が 1.5 GeV/c 以下では　　質量が軽い粒子ほど v2 が大きく

　　なることが観測されている。 v2(π)>v2(K)>v2(p)

　 => 流体力学モデルで説明。非常に早い時間での熱平衡を仮定

　　　 τ0 = 0.6 fm/c

　 => 系が熱平衡状態になっていることを示唆　　　　強く相互作用する物質の存在

meson(π,K) と baryon(p) の v2 の振る舞いが

mid pT で異なる

Hydro;Phys. Rev. C 67 (03) 044903v2; Phys.Rev.Lett.91 182301 (2003) 　 PHENIX

金＋金、√ s =200GeV

2009/3/18

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000091000018182301000001&idtype=cvips&gifs=yes


48

Elliptic flow @ Mid pT

v2: Au+Au, √s = 200GeV , MB

KET = mT-m0

Mid pT (~1.5GeV/c<pT <~4.0GeV/c)• 流体力学モデルで説明できない。• meson(π,K) と baryon(p) で v2 の振る

舞いが異なり、クォーク数でスケールする。– クォーク数でスケールすると v2 は同じ

カーブを描く (universal v2 の存在 )• KET scaling で、質量の効果を取り除く

と低い pT 領域から一致する。• v2 の横運動エネルギー依存が粒子種に

よらずに一致する。（なぜか？）• Φ メソンもクォーク数でスケールする。• u,d,s クォークに比べて重い c クォーク

も、 u,d,s クォークと同程度に flow しているという解析結果もある。（ Shingo’s D-thesis ）

PRL 98, 162301

Recombination の描像と一致する。クォークレベルで flow が決まっている

ことを示唆している。 2009/3/18


49

Quark Number Scaling

)3(

)2(

33

3

23

3

tB

B

tM

M

pwCpd

NdE

pwCpd

NdE

QGP

Hadron

ハドロン化のメカニズムの一つで、近くにある同じぐらいの運動量を持つクォークがくっついてハドロンをつくるというモデル

qq => Meson (π,K)qqq => Baryon (p) Universal なパートン分布 w(pT) を仮

定　

mesonbaryon

w(pT)

パートン分布

)3(3

)2(2

,2,2

,2,2

tqB

tqM

pvv

pvv

v2 がパートンレベルで決まっていれば以下の式が成り立つ

p/π ratio をよく再現している。

recombination

Recombination model

fragmentation

v2 (200GeV 　Au+Au ) のbaryon とMeson の違いを再現している。 2009/3/18


50

v2(KET/nq)/nq/epar/Npart1/3

Universal Scaling Different System (Au+Au, Cu+Cu) Different Energy (200GeV ~

62.4GeV) Different Centrality (0-50%) Different particles (π/ K /p 　・・・ )

Universal Curve !!

3/1

2 )/(

partq

qET

Nn

nKv

2009/3/18

Backup (Heavy Quark)


52

• RHIC outcome– J/Y suppression as strong signature of

deconfinement– mechanism not uniquely identified

• no J/Y melting, but only Y’ and cc?• melting/regeneration balance?

• LHC prospect– systematic measurements of J/Y,, excited

states– unified understanding of suppression

mechanism(s)

Initial(?) Strategy #3 ： Heavy Q’onia

2009/3/18


53

• LHC: hard/heavy QCD machinecharm/beauty sNN (mb) shadowing

multiplicity• p+p 14 TeV 11.2/0.5 1.0/1.0

0.16/0.007• central Pb+Pb 6.6/0.2 0.65/0.85 115/4.6

• fate of J/Y?– larger energy density leading to J/Y melting

at last?– larger charm yield leading to regeneration

dominance?– note 20 – 30% J/Y from B decay

• open beauty measurement important

J/ Y at ALICE/LHC

2009/3/18


54

• (1s) melting only at LHC• (2s) expected to melt approximately

with J/Y• pT dependence of (1s)/ (2s) interesting

– key to resolve possible melting/regeneration balance

Relevance of

2009/3/18


55

• ALICE uniquely down to pT = 0 and at large rapidity

Quarkonia Measurements at LHC

2009/3/18


56

• ALICE (and CMS) capable to separate substates– ~ 100 MeV resolution required

Quarkonia Resolution: Sub-States of

ALICE e+e-

s < 80 MeV

ALICE m+m-

s < 100 MeV

CMS m+m-

s ~ 80 MeV

ATLAS m+m-

s > 120 MeV

2009/3/18


57

• e.g. in 1 month of Pb+Pb– J/Y: good statistics

• up to ~ 20 GeV/c

– Y’: smaller S/B– (1s), (2s): good S/B

• up to ~ 8 GeV/c

– (3s): lower statistic

Quarkonia Statistics/Feasibility

S[103

]B[103

]S/B S/(S+B)

J/Y 130 680 0.20

150

Y’ 3.7 300 0.01

6.7

(1S) 1.3 0.8 1.7 29

(2S) 0.35 0.54 0.65

12

(3S) 0.20 0.42 0.48

8.1

m+m- raw spectra

m+m- after combinatorics subtraction

2009/3/18

Backup (Photon)


59

pt direct/decay direct/decay thermal/decaythermal/decay

(GeV/c) w/o suppression 80% suppression w/o suppression 80% suppression

3 [1] 4 – 10 % 4 – 10 % 3 – 9 % 3 – 9 % [2] 5 – 9 % 5 – 9 % 5 – 9 % 5 – 9 % [3] 5 – 10 % 5 – 10 % 4 – 8 % 4 – 8 %

5 [1] 6 – 12 % 12 – 25 % 3 – 9 % 6 – 18 % [2] 6 – 10 % 12 – 20 % 3 – 5 % 6 – 10 % [3] 11 – 15 % 20 – 30 % 7 – 12 % 14 – 22 %

10 [1] ~ 10 % ~ 50 % ~ 5 % ~ 25 % [2] ~ 10 % ~ 50 % < 1 % < 5 % [4] 25 – 30 % 15 – 20 %

[1] F.Arleo et al., hep-ph/0311131[2] F.Arleo, D.d’Enterria, D.Peressounko,

nucl-th/0707.2357[3] S.Turbide, R.Rapp, C.Gale, hep-ph/0308085[4] S.Turbide, C.Gale, S.Y.Jeon, G.D.Moore,

hep-ph/0502248

Direct/Thermal Photon Expectations

2009/3/18


60

• extrapolated from PHENIX/EMC to ALICE/PHOS– based on expected PHOS performance

Systematic Errors on Photons

p0 pt (GeV/c) 2 6 10 16

Peak extraction (%) 3.7 2.5 2.4 2.3

Acceptance (%) 1.0 1.0 1.0 1.0

PID efficiency (%) 5.8 4.1 4.3 4.1

Energy scale linear (%) 4.0 4.0 4.0 4.0

Energy scale non linear (%) 1.7 0.7 0.5 0.5

Merging (%) 0.0 0.0 0.0 0.0

Non vertex (%) 2.0 2.0 2.0 2.0

Conversion (%) 3.4 3.4 3.4 3.4

Total (%) 9.1 7.5 7.8 7.0

gpt (GeV/c) 2 6 10 16

Peak extraction (%) 3.7 2.5 2.4 2.3

Charged contamination (%) 2.4 2.4 2.4 2.4

Neutron contamination (%) 2.0 0.1 0.1 0.1

Other mesons contribution (%) 6.0 3.0 3.0 3.0

Acceptance (%) 0.7 0.7 0.7 0.7

PID efficiency (%) 3.0 2.0 2.0 2.0

Energy scale non linear (%) 1.7 0.7 0.5 0.5

Merging (%) 0.0 0.0 0.0 0.0

Non vertex (%) 2.0 2.0 2.0 2.0

Conversion (%) 1.8 1.8 1.8 1.8

Total (%) 8.9 5.8 5.7 5.7

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61

Pre-equilibriumThermalizationQGP phase?

Mixed phaseHadronization (Freeze-out) + Expansion

Photons from Multi Stage

Compton/AnnihillationFragmentation

Prompt PhotonJet-Photon Conversion

Jet-Bremsstrahlung (QGP)

Jet+MediumThermal Photon (QGP)Thermal Photon (HG)

Thermal Photon

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62

Decay photons

+ Decay photon as huge background

The decay photon background strongly reduced due to jet suppression in A+A

Schematic Spectrum in A+A

Thermal Photon (QGP)Thermal Photon (HG)

Jet-Photon ConversionJet-Bremsstrahlung (QGP)

Thermal Photon

/g E Tethermal:nT

1

phard:

Jet+MediumCompton/Annihillation

Fragmentation

Prompt Photon

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63

Schematic Spectrum in A+A

Thermal Photon (QGP)Thermal Photon (HG)

Thermal Photon

Compton/AnnihillationFragmentation

Prompt Photon

pT ~ Tmedium

~ 1 GeV (QGP) ~ 200 MeV (HG)

pT ~ QCD

Tmedium ~ 1 GeV (QGP)

Jet-Photon ConversionJet-Bremsstrahlung (QGP)

Jet+Medium

pT ~ pT

q (Conversion)

< pTq (Brems)

Jet

Compton

Fragmentation

Conversion

Fries et.al.PRL90(2003)132301

2009/3/18

64

BNL-RHIC-PHENIX: Au+Au sNN=200 GeV

PHENIX

p+p 衝突の重ね合わせで記述できる。 2009/3/18



65

100 xT

Au+Au minimum bias

gq ->q is main contribution

BNL-RHIC-PHENIX: Prompt Photon

x=0.1 から 0.2 にかけて 20 ％の減少がみられた次のページへ

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66

BNL-RHIC-PHENIX: Prompt Photon

• pQCD Photon = Direct Photon + Fragmentation

PRL98(2007)012002, PHENIX

direct

Fragmentation

calculation by W. Vogelsang

At RHIC energy, the fragmentation contribution is not negligible, ~30% at 10GeV/c photon.

p+p

Au+Au

Isolation cut により直接光子の収量が減る。 Fragmentation + Underlying Event

により説明可能

Isospin effect + Fragmentation Quenching is consistent with data

Hep-ph/0601075, by F.Arleo

Arleo JHEP 0609 (2006) 015

2009/3/18


67

BNL-RHIC-PHENIX: Thermal Photon

• NLO pQCD

• A particular thermal Model– 2+1 hydro, t0=0.15 fm/c

– T0ave=360 MeV(T0

max=570 MeV)

– The data are consistent with thermal + pQCD

– pQCD questionable down to low pT

• needs confirmation from analysis of p+p data

L.E. Gordon, W. VogelsangPhys. Rev. D48, 3136 (1993)

D. d’Enterria, D. Peressounkonucl-th/0503054

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68

QGP-ThermalJet-photon

NLO-pQCD

All

• Interaction of hard-scattered parton with dense matter.– Compton scattering

(jet-photon conv.)• R.J. Fries, Phys.Rev. C72

(2005) 041902 – Over estimation at high-

pT• S. Turbide, Phys.Rev. C72

(2005) 014906– Reproduce data well

– Bremsstrahlung• B.G. Zakharov, JETP Lett.

80 (2004) 1

Jet-quenching effect for fragmentation photons are estimated with AMY formalism.

BNL-RHIC-PHENIX: Jet-Medium

もう少し理解が必要

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69

Direct Photon Measurement in ALICE Hard photon

Strong suppression of high pT hadrons will help to improve the S/N ratio

High pT photons can be found Thermal photon

Direct evidence of thermal equilibration

Created matter in LHC will have high temperature, high density and long life time matter comparison with RHIC, so we can expect large thermal photon component in ALICE

Primary contributor in low pT regionThermal photon measurement is

very challenging because it is very hard due to a large background from hadron decays.

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70

Low pT Photons

In ‘real’ photon measurement Measured yield with a large systematic

errorDifficulty on measuring low pT “real” direct photons

1. Finite energy resolution of the EMCal

2. Large hadron background

Advantages on measuring ‘virtual’ photons

1. High momentum resolution of the TPC

2. Reliable estimation of the hadron decay components using Kroll-Wada formula

Experimental determination is very important since applicability of pQCD is doubtable in low pT region

2009/3/18


Virtual Photon Measurement

71/16

Case of Hadrons

Obviously S = 0 at Mee > Mhadron

Case of g*

– If pT2>>Mee2

Possible to separate hadron decay

components from virtual photon in the proper mass window.

Any source of real g can emit g* with very low mass.

Convert direct g* fraction to real direct photon yield

S : Process dependent factor

3

2

222 1

hadron

eeee M

MMFS

1S

qg*

g q

e+e-

gp

SdNMM

m

M

m

dM

Nd

eeee

e

ee

e

ee

121

41

3

22

2

2

22

inclusive

direct

inclusive

direct

gg

gg

Kroll-Wada formula

2009/3/18


Evaluation the Statistics in First Year Evaluation from NLO pQCD

calculation Used INCNLO

http://wwwlapp.in2p3.fr/lapth/PHOX_FAMILY/readme_inc.htm

CTEQ6M, BFG √s : 14TeV pp μ : 0.5pT,1.0pT,2.0pT

Evaluation of the number of the virtual photon

Assumed DAQ rate :100KHz

1 Day ： ~2M 1 Month ： ~60M 3 Month: ~ 180M

Acceptance Correction Considered TRD

acceptance |h|< 0.9 f coverage: 8/18 x 2p72

30 Days90 Days

Enough Statics !

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73

• expected signal/background ratio– 4 ~ 10 % (3 GeV/c) – 25 ~ 50 % (10 GeV/c)

• expected systematic error with ALICE/PHOS– 8.9 % (2 GeV/c) – 5.7 % (10 GeV/c)

Direct/Thermal Photon Feasibility

2009/3/18

Backup (RHIC Results)

75 2009/3/18



76

RHIC Outcomes: New State of Matter

2009/3/18

Backup (J-Cal)


78Dec.2008, Wuhan

Plenty of high pt jets

• Many orders of magnitude!

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79

Technical details

• We like to increase #of mod. by sacrificing read outs• for larger yields and for jet

broadening

• Why not with PHOS?• Too narrow in eta for jet finding

1 super module =12 x 24

=288 modules

~ 1 Super Module16 x 16 =256 modules

(ΔΦ,Δη)~(0.4,0.4)

11 super module ΔΦ=110o (~1.9 rad)|η|<0.7

W. Current Our Budget

4 towers/module

2009/3/18

ALICE Experiment at LHC Hiroshima University T. Horaguchi 03/18/’09 for the Recent Topics in...

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