The%20first%20Physics%20with%20ALICE

1
LHC??ALICE????PHOS????
??? ( ???? ??????? )
2
??????-???
3
(No Transcript)
4
LHC??2007????????? ?????????????? ????,????
5
Initial Conditions
pre-RHIC guess still expect conditions to be
significantly different
6
ALICE _at_ LHC
CERN/LHC???????????? 14 TeV?????
5.5 TeV????,??????ATLAS,CMS,LHCb?ALICE?
ALICE(A Large Ion Collider Experiment),an
experiment is optimized to study in detail the
behaviour of matter at high densities and
temperatures, in view of probing deconfinement
and chiral-symmetry restoration?
------??QGP???
7
(No Transcript)
8
Novel aspects Qualitatively new regime

• Probe initial partonic state
• in a novel Bjorken-x range
• (10-3-10-5)
• nuclear shadowing,
• high-density saturated gluon distribution.
• Parton dynamics dominate the fireball expansion

9
Novel aspects Qualitatively new regime

• Hard processes contribute significantly to the
  total AA cross-section
• (shard/stot 98)
• Bulk properties dominated
• by hard processes
• Very hard probes are abundantly produced.
• Weakly interacting probes become accessible
• (g, Z0, W).

10
ALICE/PHOton Spectrometer
PHOton Spectrometer (PHOS), will detect
electromagnetic particles in a limited acceptance
domain at central rapidity and provide photon
identification as well as neutral mesons
identification via the 2-photon decay channel.
Main physical goals

• Testing thermal and dynamical properties of the
  initial phase of collision, in particular the
  initial temperature and space-time dimensions of
  hot zone.

• measurement of direct single-photon and
  di-photon spectra

• measurement of Bose-Einsten correlations of
  direct photons

• Investigating jet quenching as a probe of
  deconfinement, studied via high pT p0 spectrum,
  and identifying jets through gamma-jet and
  jet-jet correlations measurements.

• signals of chiral-symmetry restoration.

11
Physical goals

• Direct photons
• once produced dont interact with the fireball ?
  carry information about early stage of a
  collision
• Thermal photon spectra pT ? 5GeV
• dominantly from early, hot QGP phase
• ? initial temperature of a QGP fireball
• Thermal photon HBT correlations
• ? space-time dimension of the fireball and direct
  photon yield at low pT
• Hard process (pQCD) photon spectra pT gt 5GeV
• Test of Ncoll scaling of hard processes
• ? tagged jets
• Spectra of identified p0 in a broad transverse
  momentum range
• Determination of the decay photon background
• Study of the jet quenching
• Spectra of identified ?-mesons

12
Technical data 17920
lead-tungstate crystals(PWO) -distance to IP
4600mm
-coverage in
pseudorapidity -0.120.12 -coverage
in azimuthal angle 100o -crystal size
22x22x180
mm3 -depth in radiation length
20 -modularity
5 modules -total area
8m2
-total crystal weight
12.5 t -operating temperature
-25 oC -photon readout
APD
PHOS (PHOton Spectrometer) is a high resolution
electromagnetic calorimeter consisting of 17920
detection channels based on lead-tungstate
crystals(PWO).
13
Assembly of PHOS module
14
Energy and spatial resolution of PHOS
???????????1 GeV/c?????????????????3.2 mm???3.9
mm,????10 GeV/c???1.2 mm?? ?2.6 mm
??????1 GeV/c??4???100 GeV/c??1
15
Trigger system of ALICE
ALICE??????????????????????????????????????
????ALICE???????????????ALICE??????????????,??????
?ALCIE???????????????????ALICE???????????????????
??(Level 0,??L0),????(Level 1,??L1)?????(Level
2,??L2)
L0????,?????1.2 µs??,????ALICE????????????(FEE)??
?
L1????,?????6.5 µs??,??L0????????????,????????(DA
Q)??????????????????????????
L2?????????,?????88 µs???,???????TPC???????????,?
??????????????????????????????DAQ?HLT(High Level
Trigger)???
16
Trigger signals L0, L1, L2
L0?????????T0?V0???,?????PHOS?EMCAL???TRD?µ???????
L1???????????????????(1)??µ?????????(2)???????,?
PHOS?FMD?ZDC????
L2???????TPC?????????L2????????,????TPC??????
?ALICE?????,?24?L0??,20?L1???6?L2???
??ALICE?????PHOS( Photon Spectrometer
)??L0?L1????,??ALICE????????
17
Trigger decision criterion of PHOS
PHOS??????FPGA?????????,?????????????-???????????
?L0???????-??????????????L1???
18
FEE-gtTRU signal routing

• 112 analog sums are fanned in, via 14 FEE to
  1 TRU
• due to 22 sums one TRU covers 448
  crystals
• 1 level-0 output
• 3 level-1 outputs

19
Trigger decision criterion of PHOS
ALICE?????,??PHOS??L0???????????800
ns,??L1???????????6200 ns?
PHOS??TRU???????????????L0?L1,??????PHOS??????????
20
Energy reconstruction performance
????????µ5.510 GeV,??s0.104 GeV,sE/E1.89
????????µ5.660 GeV,??s0.099 GeV,sE/E1.75?
????????PHOS??????????????????????????
21
Trigger efficiency of PHOS
Trigger threshold
??????????
Trigger efficiency loss about 4 due to the TRU
boundaries
22
Trigger rate of PHOS for P-P collision
? pp run L 51030 cm-2s-1, vsNN14 TeV,
mini-bias events stotal0.1 b Pythia6.2, 6106
pp collision events.
1 module Df 20? Dy 0.25
3 modules Df 60? Dy 0.25
5 modules Df 100? Dy 0.25
23
Trigger rate of PHOS for Pb-Pb collision
? PbPb run L 51026 cm-2s-1, vsNN5.5
TeV,stotal7.7 b Hijing1.36, 1105 PbPb
collision events, impact parameters (0, 3 fm).
1 module Df 20? Dy 0.25
3 modules Df 60? Dy 0.25
5 modules Df 100? Dy 0.25
24
Summary

• ? LHC/ALICE is a powerful next generation
  detector
• first truly general purpose HI experiment
• addresses most relevant observables from
  super-soft to ultra-hard
• many evolutionary developments SSD, SDD,
  TPC, em cal,
• some big advances in technologyelectronics,
  pixels, TOF, computing

• ? ALICE/PHOS performs well in trigger decision
• with good performance of energy reconstruction in
  a broad transverse momentum range from 0.5 GeV/c
  to 100 GeV/c
• trigger efficiency 1) showed a first order
  exponential decay versus pT, 2) showed a loss
  about 4 due to the TRU boundaries
• trigger rate 1) for direct photons was much
  higher than it for p0 and ?-mesons, 2) PHOS could
  provide L0 trigger by its FEE card to low pT
  photon events and ALICE/CTP provide L0 trigger to
  high pT photon events, 3) PHOS could provide L1
  trigger by its FEE card.

25
Thanks!
26
PHOS mechanics
Crystal detector unit
PHOS module Working temperature -25 oC

• Modular structure
• 5 independent modules each of 3584 crystal
  detector units
• PWO crystal APD preamp.

Strip unit of 16 detector units
PHOS Cradle