The ALICE experiment and its Electromagnetic Calorimeter EMCAL E mgm EM L

87 Pages·2011·10.51 MB·English

The ALICE experiment and
its EElectrommaggnetic Calorimmeter EEMMCALL
Alessandra Fantoni
INFN, LaboratoriNazionaliFrascati
ALICE Collaboration
I -The ALICE experiment:
aa)) SSoommee iinnffooss
b) Characteristiques, Constraints and Solutions
c) Obtained results
II -The Electromaggnetic Calorimeter EMCAL:
a) Characteristiques
b) How it works
c) The Assembly
dd)) RReessuullttss ffrroomm tteesstt bbeeaammss
e) The EMCAL status
f) The EMCAL upgrade: DCAL
g) Performance pplots
h) Physics capabilities
2011 BCVSPIN Advanced Study Institute in Particle Physics and Cosmology
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Hue’, Vietnam, July 25-30, 2011
I. The ALICE experiment
~ 11000000 MMembbers andd growiing…
from both NP and HEP communities
~30 Countries
~100 Institutes
~ 150 MCHF capital cost
(+ ‘free’ magnet)
HHiissttoorryy:: ttwwoo ddeeccaaddeess ……
1990-1996: Design
1992-2002: R&D
2000-2010: Construction
22000022-22000077: IInsttallllattiion
2008 -> : Commissioning
4 TP addenda along the way:
1996 : muon sppectrometer
1999 : TRD
2006 : EMCAL
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2010 : DCAL
I – a)) Some infos
• 4 large experiments
• ALICE
(cid:57)mainlly ddeddicatedd to
heavy-ion physics
(cid:57)p-p run for physics
aanndd rreeffeerreennccee
8.6 km
- Hard & Soft physics
- Excellent PID
-TTrackkiing ddown tto very
low momenta
LLHHCC
LHC
QCD expectations
Protons and neutrons are colorless objects made
bbyy ccoonnffiinneedd ccoolloorreedd qquuaarrkkss ee gglluuoonnii:: QQCCDD
QCD aymptotic freedom (Nobel 2004 to Gross-
Wilczek-Politzer) : at very high momentum transfer,
tthhe hhaddroniic matttter wiillll melltt iin a pllasma off
deconfined and colored quarks and gluons.
TThhee ccrriittiiccaall tteemmppeerraattuurree ooff 117700 MMeeVV hhaass bbeeeenn
reached by SPS and RHIC but evidence of
residual interaction has been shown.
TThhe matttter creattedd att RRHHIICC bbehhaves lliikke a
liquid and not like a gas!
LHC will ggo well above the critical tempperature
A Quark Gluon Plasma can be created, as it was
in the early Universe just after the Big Bang
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Dynamics and signals
((tthhaatt wwiillll bbee ssttuuddiieedd bbyy AALLIICCEE))
??
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I – b) Characteristiques, Constrainsts and Solutions
• What makes ALICE different from ATLAS, CMS and LHCb?
– EExperiiment ddesiignedd ffor HHeavy IIon colllliisiion
• only dedicated experiment at LHC, must be comprehensive and be able to
cover all relevant observables
•• VVEERRYY rroobbuusstt ttrraacckkiinngg
– high-granularity detectors with many space points per track, very
low material budget and moderate magnetic field
• PPIIDD oovveerr aa vveerryy llaarrggee pp rraannggee
TT
• Hadrons, leptons and photons
• Very low p cutoff
T
• EExcellent vertexingg
– Price to be paid:
• Slow detectors
• LLiimmiitteedd ηη aanndd pp ccoovveerraaggee
TT
• Complementary to the other experiments
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Experimental Constraints
((ffrom tthhe HHeavy IIon runniing))
– eexxttrreemmee ppaarrttiiccllee ddeennssiittyy ((ddNN //ddηη ~~ 22000000 – 88000000))
ch
• x 500 compared to pp @ LHC
– llaarrggee ddyynnaammiicc rraannggee iinn pp ::
TT
• from very soft (0.1 GeV/c) to fairly hard (100 GeV/c)
– leppton ID, hadron ID, pphoton detection
– secondary vertices
– modest Luminosityy and interaction rates
• 10 kHZ (Pb-Pb) to 300 kHZ (pp) (< 1/1000 of pp@1034)
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Experimental Solutions
• dN /dη:
high granularity, 3D detectors (560 million pixels in the TPC alone,
ch
giving 180 space points/track, largest ever: 88m3), large distance to vertex
((use a VVEERRYY llarge magnet ))
- EMCAL high-density crystals of PbWO at 4.5 m (typical is 1-2 m !)
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• pp coveragge: thin det,, moderate ffield ((low pp )),, largge lever arm + resolution
tt tt
(large p )
t
– ALICE: < 10%X in r < 2.5 m (typical is 50-100%X ), B= 0.5T, BL2
0 0
~ like CMS !
• PID
: use of essentially all known technologies
– dE/dx, Cherenkov & transition rad., TOF, calorimeters, muon
ffiilltteerr, ttooppoollooggiiccaall,
• rate
: allows slow detectors (TPC, SDD), moderate radiation hardness
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ALICE in 2001
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ITS Installation 15.3.07
… in construction …
TPC
SPD
SSD/SDD
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Traversing the TPC