physics in initial years at alice kenta shigaki, hiroshima university (alice collaboration) 30,...

Physics in Initial Yearsat ALICE

Kenta Shigaki, Hiroshima University(ALICE Collaboration)

30, October 2007

Workshop on Phenomenology of QGP in Heavy Ion Collisions:

from SPS and RHIC to LHC

at RCNP, Osaka University

LHC/ALICE/PHOS status and plans physics via photons in initial few years at

ALICE neutral mesons pQCD photons thermal photons

ALICE/PHOS news physics at PHENIX in parallel to ALICE summary and concluding remarks

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop

- Presentation Outline -

30, October 2007 2


- Plans at LHC/ALICE -

last cryo-dipole installated in August 2007

LHC start up plan 2008/04 accelerator/experiments closed 2008/05 beam commissioning 2008/07 p+p, s = 14 TeV, first collision 2008/end p+p, s = 14 TeV, 1032 cm2s1

soon after ?Pb+Pb, sNN = 5.5 TeV, 5×1025 cm2s1

expectation in initial few years p+p s = 14 TeV, < 1031 cm2s1 at ALICE Pb+Pb s = 5.5 TeV, 1027 cm2s1, 2 – 3

years “p”+Pb s = 8.8 TeV, 1029 cm2s1, 1 year Ar+Ar s = 6.3 TeV, 1029 cm2s1, 1 year

30, October 2007 3


- ALICE: A Large Ion Collider Experiment -

the heavy ion experiment at LHC 30 countries, 90 institutions, ~1,015

members

Sweden

PolandNorway

Russia

JINR

Japan BrazilRomaniaSpain/Cuba

South AfricaUSA

ChinaCroatia

ArmeniaIndia

Korea

UkraineMexico

Czech Rep.Slovak Rep.

CERNDenmark

Finland

Germany

France

Italy

GreeceUK

HungaryNetherlands

1000th ALICE member

30, October 2007 4


- ALICE ≈ STAR + PHENIX -

(charged particles)

µ arm

central barrel: 0.9 < < 0.9 tracking and particle identification in full

azimuth partial coverage of HMPID, PHOS, EMCal

forward arm: 4 < < 2.4 multiplicity: 3 < < 5.4

30, October 2007 5


- ALICE Photon Spectrometer: PHOS - photons, neutral mesons, jet tagging

+ level 0 and level 1 trigger capability high resolution, high granularity

/E ~ 3 %/E up to 100 GeV PbWO4 of 22 (1.0 RMoliere)×22×180 (20 X0) mm3

APD + charge sensitive preamplifier readout temperature controlled at 250.1 ˚C

|| < 0.12, = 100 degrees 56×64×5 modules

17,920 crystals, 12.5 t

30, October 2007 6

- PHOS #1 (Out of 5) - waiting for installation in 2 weeks

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop30, October 2007 7


- ALICE/PHOS Start Up Timeline - 2007/11/12 – 14 PHOS #1 installation 2007/12/02 PHOS #2 ready (?) 2007/12/10 – 21 magnet test 2007/12/10 – 21 cosmic test run 2008/01/08 – TPC commissioning 2008/02 cosmic run 2008/02/08 PHOS #3 ready (?) 2008/04 LHC/ALICE closed 2008/07 – physics run by 2009 ? PHOS #4, #5 installed30, October 2007 8


- Physics via Photons at LHC - vital probe of initial hot dense phase

thermal photons… temperature thermal photon HBT… space-time evolution direct photons… pQCD processes + jet

tagging neutral mesons… quark energy loss

experimental virtues photons and neutral mesons in same detector particle identification to very high pt

even more powerful at LHC than ever large rates up to ~ 100 GeV

30, October 2007 9

thermal ~ eE/T

hadron decays

jet-medium interaction jet-photon conversion bremsstrahlung

pQCD processes ~ pTn

compton scattering annihilation fragmentation

- Physics Topic #1: Neutral Mesons - first piece of physics

enough acceptance with 2 – 3 PHOS modules

stronger quenching and higher pt reach clearer measurement of quark energy loss leading to less background for direct photons

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 1030, October 2007

- Physics Topic #2: pQCD Photons -


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

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

direct photons at RHIC consistent with pQCD consistent with simple accumulation of p+p consistent with structure function modification consistent with/without quenched

fragmentation

- Quenched Fragmentation at LHC - pQCD photons to be suppressed

significantly another view of quark energy loss leading to less background for thermal photons


~ 60 % suppression at 10 GeV/c

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

- Physics Topic #3: Thermal Photons -


indirect measurement at PHENIX suggesting thermal component of 300 – 500

MeV high quality direct measurement at ALICE

longer life of thermalized high temperature phase

background photons suppressed due to quenching

superb PHOS detector

- Direct Photon Yield Predictions - pt direct/decay direct/decay thermal/decay

thermal/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


- Expectation at a Glance - predicted fraction of direct/decay photons


- Limiting Factors in Photon Measurement -


0 pt (GeV/c) 2 6 10 16

Peak extraction (%) 3.7 2.5 2.4 2.3

Acceptance (%) 4.0 4.0 4.0 4.0

PID efficiency (%) 5.8 4.1 4.3 4.1

Energy scale linear (%) 5.1 7.5 7.1 6.5

Energy scale non linear (%) 3.5 1.5 1.0 5.8

Merging (%) 0.0 0.0 0.0 4.8

Non vertex (%) 1.5 1.5 1.5 1.5

Conversion (%) 2.5 2.5 2.5 2.5

Total (%) 10.5 10.3 10.0 12.1

major systematic error sources in PHENIX conversion (uncertainty in amount of material) off-vertex photon (uncertainty in amount of

material) acceptance (uncertainty in bad module map) calibration and linearity efficiency (uncertainty in reconstruction

probability) charged/neutral hadron contamination peak extraction (uncertainty in background

shape)

- Extrapolated Systematic Errors - extrapolated from PHENIX/EMC to

ALICE/PHOS based on expected PHOS performance


0 pt (GeV/c) 2 6 10 16


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


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

pt (GeV/c) 2 6 10 16


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


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

- Potential at a Glance - expected sensitivity versus theory

prediction



- Thick Detectors in Front of PHOS: TRD+TOF -

30, October 2007 19


- Transition Radiation Detector - tracking and particle identification

400 – 600 m resolution in r, 23 mm in z e/ separation > 100 at pt > 3 GeV/c

|| < 0.9, full azimuth

30, October 2007 20


- Time of Flight Detector - multi-gap resistive plate chamber (MRPC)

time resolution < 100 ps || < 0.9, full azimuth; 3.7 m from beam

axis

30, October 2007 21

- Material Budget Comparison - material budget in front of EM calorimeter

WA80 11 % WA98 8.5 – 10 % PHENIX 15 % STAR 10 % D0 15 %

material in front of PHOS ITS+TPC w/o TRD+TOF 20 % ITS+TPC and TRD+TOF in technical design report

40 % ITS+TPC and TRD+TOF in current design 85

%


- Radiation Length Map -


- Problems Due to TRD/TOF Materials -


loss of photon statistics factor ~ 2 for single photons

significant especially in hard high pt region

leading to lower pt reach

extra systematic errors factor ~ 3 on neutral meson yield

due to factor ~ 3 lower S/N ratio for photon pairs leading to increased (major) systematic error

extra background photons factor ~ 4 of off-vertex photons leading to increased systematic error

- Potential at another Glance - reevaluated sensitivity versus theory

prediction ~ fatal for direct photon measurement

need to recover physics capabilityPhysics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 2530, October 2007

- News: Good Sign for Resolution -


proposal to reduce material in front of PHOS backed up by (partly reviewed) physics

arguments contributions from Hiroshima based on PHENIX

experiences

“holes” recommended and agreed in 3 (out of 5) TRD+TOF modules in front of

PHOS on ALICE management board on 2007/10/04 “hole” in reality yet to be defined


- Summary and Concluding Remarks - LHC/ALICE starting in summer, 2008

uniquely suitable for hard (and/or heavy) probes opening new ground for “soft” photonic probes

many physics via photons planned in initial years suggestions/comments more than welcome penetrating probes never easy to measure material issue against PHOS being solved

Hiroshima in full commitment on ALICE/PHOS based on old (PHENIX) and new (R&D) expertise along with still exciting physics at RHIC/PHENIX

30, October 2007 27

physics in initial years at alice kenta shigaki, hiroshima university (alice collaboration) 30,...

Documents

shigaki rcnp workshopphysics

shigaki rcnp workshop

shigaki rcnp workshop30

shigaki rcnp workshop

lhcat rcnp

phos photons

heavy ion experiment

heavy ion collisions