ALICE実験測定器の現状
Status of ALICE detector in p+p

中條 達也（筑波大学 物理学系）
Tatsuya Chujo (Univ. of Tsukuba)

日本物理学会 ２０１０年秋季大会（九州工業大学）

２０１０年９月１３日

Snap shot of ALICE Control Room (2010.08.25)- Data taking period, very quite… -�

JPS 2010, Sep. 13, T. Chujo

2最初の陽子-陽子衝突を喜ぶ研究者たち
First collision p+p s= 900 GeV(2009.11.23, ALICE Control Room)Same Room�JPS 2010, Sep. 13, T. Chujo

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The first “event” in p+p 0.9 TeV

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… and 7 TeV p+p�JPS 2010, Sep. 13, T. Chujo

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After ~9 months later…
Already lots of first results from ALICE !�

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JPS 2010, Sep. 13, T. Chujo

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Outline�
1. Quark Gluon Plasma (QGP) at LHC
2. LHC & ALICE
3. ALICE & QGP– Parton energy loss
– Collectivity– Temperature

4. Summary

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1. QUARK GLUON
PLASMA & LHC�
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9Temperature

QCD phase diagram and QGP

Tc~170 MeV• QGP in Astrophysics

RelativisticHeavy Ion
Collisions

CriticalpointQuark Gluon Plasma– Early universe:
time < 10-6 seconds– Possibly in the interiorof neutron stars

Early Universe

Hadron Gasnuclei

Color superconductor
Color-flavor
locking
Neutron Stars?

Baryon Density• QGP in Nuclear Physics–Create at the lab. by heavy ion collisions–Study the nature of QCD matterat the extreme temperature and energy density
JPS 2010, Sep. 13, T. Chujo

10Highlights at RHIC
• Jet quenching, indicating dNg/dy ~1100, ε > 100 ε0.
• Jet-medium interaction: shock wave
(hit to cs)?
• Collective ﬂow, suggesting quark
recombination.
• Heavy quark suppression and ﬂow.
• Thermal photon emission

Phys. Rev. Lett. 91, 072304(2003).

Pedestal&flow
subtracted‒ T > 300 MeV > Tc.

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RHIC vs. LHC�
RHIC�

LHC�

√sNN (GeV)�

200�

5500�

T/Tc�

1.9�

3.5-4.0�ε (GeV/fm3)�

5�

15-60�

τ QGP (fm/c)�

2-4�

> 10�

• High temperature QGP(2 x TRHIC).

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RHIC vs. LHC�
RHIC�

LHC�

√sNN (GeV)�

200�

5500�

T/Tc�1.9�

3.5-4.0�ε (GeV/fm3)�

5�

15-60�

τ QGP (fm/c)�

2-4�

> 10�

• High temperature QGP(2 x TRHIC).
• Jet production dominant.

RHIC�

LHC:Inclusive jets,
annual yield; 104 @pT = 200 GeV/c(5.5 TeV, Year-1)
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RHIC vs. LHC�
RHIC�

LHC�

√sNN (GeV)�

200�

5500�

T/Tc�

1.9�

3.5-4.0�ε (GeV/fm3)�

5�

15-60�

τ QGP (fm/c)�

2-4�

> 10�
[JW Harris, Winter WS on Nucl. Dynamics (2008)]• High temperature QGP(2 x TRHIC).
• Jet production dominant.
• Copious heavy quark
production (10x σc-cbar ).

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RHIC vs. LHC�
RHIC�

LHC�

√sNN (GeV)�

200�

5500�

T/Tc�

1.9�

3.5-4.0�ε (GeV/fm3)�

5�

15-60�

τ QGP (fm/c)�

2-4�

> 10�

• High temperature QGP(2 x TRHIC).
• Jet production dominant.
• Copious heavy quark
production (10x σc-cbar ).
• LHC:– Study the matter byclean probes, andresponse of bulk matterin HI collisions. JPS 2010, Sep. 13, T. Chujo [JW Harris, Winter WS on Nucl. Dynamics (2008)]

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2. LHC & ALICE EXPERIMENT �JPS 2010, Sep. 13, T. Chujo

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Large Hadron Collider (LHC)
LHC Basics :Magnets: 1232, 15 m long, 9 T, superconducting dipoles
Circumference: 27 km

p+p √s = 14 TeV, L = 1034 cm-2s-1
Pb+Pb √sNN = 5.5 TeV, L = 1027 cm-2s-1

ALICE

JPS 2010, Sep. 13, T.
Chujo

ATLAS
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ALICE experiment
ALICE = A Large Ion Collider Experiment•Dedicated heavy ion experiment at LHC:– Study ‘state of matter’ at high temperature & energy
density; QGP.
– LHC: 30 x energy of RHIC
• Expect very different type of ‘QGP’• ‘hard signals’ to probe QGP (jets, γ, c and bquark )• First Pb+Pb (2.76 TeV) collisions Nov. 2010

• ALICE Institutes from Japan(ese).
– Hiroshima Univ.: PHOS
– Tokyo Univ. (CNS): TRD, FoCAL upgrade– Univ. of Tsukuba: EMCal, DCal
+ Heidelberg Univ. (K. Oyama): TRD, Trigger

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ALICE Collaboration

Collaboration:> 1000 Members> 100 Institutes> 30 countries
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ACORDE
V0T0
ZDC
FMD
PMD

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Detector:Size: 16 x 26 20meters
Weight: 10,000 tons

Detector configuration 2010
•
••
•
•

ITS, TPC, TOF, HMPID, MUON, V0, T0, FMD, PMD, ZDC (100%)
TRD (7/18)
EMCAL (4/12)
PHOS (3/5)
HLT (60%)

 Full hadron and muon capabilities Partial electron and photon

ALICE detector is fully
operational !
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Data taking / Trigger (2009-2010)�
Run�

Period�System�√s(TeV)�

# of events�

Run1�

Nov. –Dec.
2009�

p+p�

0.9�

500 k (MB)�

Run2�

Mar. 30 p+p�
– Oct.
2010 �7.0

700 M (MB)500 M (singlemuon)
300 M (highmulti.)�

p+p�

0.9�

2 M (MB)�

Recorded trigger vs. Date�

Trigger: Minimum bias (MBor): SPD or V0-A or V0-C
(96% eff. for INEL).
 at least one charged particle in 8 pseudorapidity units

 V0AND: Hit on both side of V0. (93% eff. for NSD).
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Absolute normalization•••

Vernier (van der Meer) scan tells trigger cross section
Performed in Apr. for p+p at 7 TeV
V0-AND trigger cross section (~62 mb) measured with 8 % of syst. uncertainty•– beam size @ β*=2 m• X: 44 µm• Y: 47 µm
Using this result, the crosssection normalization for all
measurements (J/ψ,charm) are on going

top rate

Dx or Dy
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3. ALICE EXPERIMENT AND
QGP PHYSICS�
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(1)Energy loss of parton
R AA =YieldAuAu / 〈Nbinary 〉 AuAuYieldpp

Phys. Rev. Lett. 91, 072304 (2003).

Pedestal&flow subtracted– At RHIC energy:– High pT yield suppression.
– Gluon density: dNg/dy ~ 1100
– Energy density: ε > 100 ε0 (!)– = ε > 15 GeV / fm3– Disappearance of away side jet.

JPS 2010, Sep. 13, T. Chujo?
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Where is the lost energy?
How parton propagates indense matter ?

PHENIX (PRL 97, 052301, 2006)�

Away side

Near side

Two peaks in Away side.
Shock wave?
JPS 2010, Sep. 13, T. Chujo

Key detectors for hard probes inALICE�•••ITS, TPC, TRD (40%), TOF, HMPID– Charged particles Δη = 1.8.
– Excellent momentum resolution.
– Excellent PID and heavy flavortagging.
– TRD: high pT and electrontrigger.
EMCal (40%)– Pb-Scint.
– Energy of neutral particles– Δφ = 107°, Δη = 1.4– Energy resolution ~10%/√Eγ– Jet and γ trigger
PHOS (60%)–PWO– 220° < φ < 320°, Δη = 0.24
– Energy resolution ~3%//√Eγ– γ trigger.
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Time-Projection Chamber (TPC)

p (GeV/c)

Momentum resolution (ΔpT/pT)�

TPC dE/dx vs. p�• Detector fully operational: 99.9% of all channels• dE/dx resolution: < 5%
• Momentum resolution: < 7% at 10 GeV• Working on distortion map: Δp/p < 5% at 10 GeV• Read-out rate up to 1kHz
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Calorimeters: PHOS, EMCAL �• Invariant mass of π0 at 7 TeV p+p data.
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29•e± identification in TPC•Study of γ conversion
points/material budget

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Di-Jet event (7 TeV p+p)�

η-φ grid�

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DCAL (Dijet Calorimeter)
A 60% expansion of EMCal
arranged to permit back-toback hadron-jet, jet-jet andgamma-jet measurements.
Goal: QGP tomography via
detailed «jet quenching»studies: PbPb/pp jet x-section
ratios, fragmentation
functions, …
( T. Gunji’s Talk)

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JPS 2010, Sep. 13, T. Chujo

(2) Collectivity••••

At RHIC energy:
Quark number scaling of v2 works.
Indication of quark level collective motion at RHIC.
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What happens at LHC?

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T

explosive
sourcelightT,βheavypT

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1/pT dN/dpT

purely thermal
source1/pT dN/dpT

Radial flow�

lightheavy
pT

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Radial flow at RHIC�
Au+Au 200 GeV central (b < 2.6 fm)

D.d'Enterria &D. Peressounko
nucl-th/0503054••

Large radial flow observed at RHIC.
Charged particle identification is key to understand matter
properties.�
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ALICE PID Capability�

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ALICE PID performance (1)ITS
ALICE performance
Work in progress

dE/dx (a.u.)

TOFTPC PID using ITS, TOF, TPC
TPC dE/dx:• separates p/ K up to 1.1 GeV
TOF:• separates K/ π up to ~ 1.5 GeV

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ALICE PID performance (2)�
TPC

HMPID
(Cherenkov ring angle vs. momentum)e±�JPS 2010, Sep. 13, T. Chujo

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Strangeness productions (p+p 7 TeV)Σ* → Λ π

Κ* → Κ πΩ→ΛΚΞ→Λπ< 2% of statistics
at 7 TeV

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(3) Temperature

DATA: Tini > TAuAu ~ 220 MeV
MODELS: Tini = 300 to 600 MeV
Lattice QCD prediction： Tc ~ 170
MeV

Indicating thermal photonemission at low pT.
PHENIX (PRL 104, 132301 (2010))�
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Charmonium: suppression or enhancment?
J/ψ suppression & regeneration at LHC?
χc, ψ’ suppression (J/ψ TD ~ 1.5-2.0 Tc)?

enhancedregeneration

enhanced
suppression

TLHC >> J/ψ TD
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SPS
RHIC
LHC

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Transition-radiation detector (TRD)

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Muon detector (di-muon event display)

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J/Ψ at p+p 7 TeV
J/Ψ → e+e- |y| < 1J/Ψ → µ+µ-, y = 2.5 - 4 1

Mass resolution ~50 MeV even with low field,
due to low material budget

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Charm at p+p 7 TeV

Impact Parameter Resolution vs pT

80 µm @ 1 GeV
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Prospects for Pb+Pb
What will be luminosity for November 2010?
••

Design luminosity for Pb+Pb: 1027 cm-2s-1– ~ /10 from number of bunches– ~ /10 from increased beam size (lower energy, less focussing)
Most probable value  1025 cm-2 s-1 [J. Jowett]

What is expected amount of data sample?
••

Depends critically on overall duty factor and number of dayse.g.: 20 days at 50 Hz min bias at 20% overall duty factor
 ~ 1.5 x 107 min bias events (as opposed to target of a few 107
central!)JPS 2010, Sep. 13, T. Chujo46

Summary�• ALICE detector is fully operational since thefirst collision.
• p+p (mainly 7 TeV):– Re-discovering “standard model” and particle zoo.
– Providing an important reference data to the heavy
ion data.

• Pb+Pb:– Will start the 2.76 TeV Pb+Pb run on Nov. 2010.

• Exciting moment, new regime of QCD matter,and discoveries !!
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Wow !
it’s not liquid,
it’s QGP gas…�

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Thank you for your attention.

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