Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Detection of photons and electrons in EMCAL...
-
Upload
kenneth-warner -
Category
Documents
-
view
229 -
download
0
Transcript of Cynthia HadjidakisTerzo Convegno sulla Fisica di ALICE Detection of photons and electrons in EMCAL...
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Detection of photons and electrons in EMCAL
Photons, Electrons and 0 at large pT
Identification of photons and 0 with EMCAL Detection of electrons in EMCAL
Cynthia Hadjidakis
Terzo Convegno sulla Fisica di ALICE Wednesday, November 14, 2007
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Photons, 0 and electrons at large pT
Direct photonsprompt photons
hard processes: compton (g q q) and annihilation (q q test QCDproduction unperturbed by the medium-jet events
Neutral mesonsvia decay photons detection
medium effect observation of hadron suppression in Heavy Ion collisions
Electronsfrom semi-leptonic decays of b and c quarks
medium effect different suppression for light and heavy quarks in Heavy Ion collisions
_
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Calorimetry in ALICE
PHOS: = 0.24, =100ºDistance to I.P 4.40 mhigh granularity: 17.920 crystalsE > 10 GeV E/E < 1.5%
11 Super Modules2 SM per 20o sector
EMCAL = 1.4, = 110o
Distance to I.P 4.28 mgranularity: 12.672 towers ×~ 0.014×0.014E>10 GeV E/E < 4%
Y
X
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
EMCal and high pT physics
EMCAL capabilities:
inclusive jets : ET ~ 200 GeV
dijets: ET ~ 170 GeV
inclusive : pT ~ 90 GeV/c
inclusive : pT ~ 70 GeV/c + jet pT ~ 40 GeV/c
e (semi-leptonic decay of heavy quarks ): pT ~ 25 GeV/c
10k/year
Annual yields in ALICE with EMCAL
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Identification of photons and 0 in EMCAL
pT< ~ 10 GeV/c 10 ~ < pT< ~ 40 GeV/c
merged cluster→ shower shape analysis
resolved clusters → invariant mass
analysis
small aperture angle isolation cut
→ talk by Gustavo
R
TPC
candidate
IP
three regions of analysis
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
0 reconstruction via invariant mass
→ effect of the HI environment: efficiency decreases (<10%)→ measured 0 yield as input of simulation to obtain the decay distribution
→ measurement of direct
effi
cien
cy only EMCAL● single particles○ + HI
even
ts
1 2 invariant mass (GeV)
simulation for pp and PbPb conditionshigh occupancy in PbPb: increase cluster energy threshold
100 MeV (pp) → 500 MeV (PbPb)
mGeV
simulation: single particles+HI only EMCAL
only EMCAL- single particles + HI
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Shower shape analysis
0, longest axis of cluster ellipsoid
Bayesian method developed for the PID based on a parametrization of 0
, e-
°
charged hadrons
0 27 GeV
fit: Landau+Gaussian
02
dn
/d 0
2
Guénole Bourdaud
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
rejection () about 5 Ndirect /N from NLO calculations:
→ isolation cut needed to improve rejection
Shower shape analysis
→ HI environment: lower efficiency (10 to 20%)
→ Identification of and 0 from ~10 GeV to ~40 GeV with this method
(preliminary results: studies with realistic background needed)
pp PbPb
0.002-0.02 0.01-0.1
PID for0PID for
effi
cien
cy/p
urity
effi
cien
cy/p
urity
simulation: single particles full ALICE flat and 0 distributions
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Detection of electrons in EMCaLtrack matching: each charged track is associated with a EMCAL cluster (if any)
→ add ALICE PID information from EMCAL to high pT charged tracks (TRD rejection for high pT)
simulation: single particles full ALICE
Alberto Pulvirenti
Mark Heinz, Jennifer Klay, Alex Donoghue
pTPC / EEMCAL
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Electron identification
→ rejection of 100-500
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Photon Conversion
Center of Collision
Time Projection Chamber
EMCAL
Inner Tracking System
TRD and TOF
50% of photons convert into e+e-
→ 45% of photons convert into TRD and TOF→ removed by p/E cut
Other sources of background: photon conversion and Dalitz decay
X (cm)
Y (
cm)
Cynthia Hadjidakis Terzo Convegno sulla Fisica di ALICE
Conclusion
EMCAL improves ALICE capabilities to measure high pT photons, electrons and 0
Direct photons and 0 measurements Identification with invariant mass technique up to pT ~ 10 GeV/cIdentification with shower shape analysis up to pT ~ 40 GeV/cIsolation cut to improve rejection and for higher pT region
Detection of electrons
Electron identification and good rejection with track matching