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EM Resolution Studies EM Resolution Studies
D. Banfi, L. Carminati (Milano), D. Banfi, L. Carminati (Milano), S.Paganis (Wisconsin)S.Paganis (Wisconsin)
egamma WG, Atlas Software egamma WG, Atlas Software Week, Week,
CERN, 26-May-2005CERN, 26-May-2005
26-May-2005 EM Resolution Studies 2
IntroductionIntroduction
Continue work that started last year Continue work that started last year (Slovakia Workshop), to understand in (Slovakia Workshop), to understand in detail the origin of loss of resolution at detail the origin of loss of resolution at high etahigh eta
Motivate/Study corrections which recover Motivate/Study corrections which recover the nominal resolution (TDR/TBeams)the nominal resolution (TDR/TBeams)
Study corrections with MC Test corrections in the combined TestBeam (material
scans)
Our goal here is to identify the dominant Our goal here is to identify the dominant effects and NOT to propose a correction:effects and NOT to propose a correction:
Possible corrections will be discussed/proposed by a group of people from the LAr+egamma communities.
26-May-2005 EM Resolution Studies 3
Resolution vs upstream Resolution vs upstream materialmaterial
From Scott Snyder’s Resolution studiesConfirmed by L.Flores and G.Unal with 10.0.1
X0 map of material in front of strips (SP)
26-May-2005 EM Resolution Studies 4
Longitudinal FluctuationsLongitudinal Fluctuations
strips
e 50GeV
Middle Back
Presampler LAr CalorimeterUpstream Material
ATLAS Longitudinal weights calculated today using:ATLAS Longitudinal weights calculated today using:
33210 EWEEEWbE presrec
Best Performance: Erec independent of Eloss (function of shower depth)
TDR + offset (coming from TBeam Analysis)
Longitudinal Leakage
Out of cone
Losses betweenPS and S1
Upstream Losses
26-May-2005 EM Resolution Studies 5
Simulation 10.0.2:Simulation 10.0.2:
Full Simulation: Full Simulation: 20, 50, 100GeV electrons, photons Eta = 1.2125 (~3X0 in front of Strips) Phi = Flat or Fixed Use shower dE/dx information anywhere
(calibration hits)
Calibration Hits:Calibration Hits: Energy in LAr = ‘active energy’ Energy in Passive material (i.e. Lead) = ‘inactive
energy’ Energy in Cryostat, cables etc = ‘dead energy’
26-May-2005 EM Resolution Studies 6
Out-of-cone fluctuations depend on Out-of-cone fluctuations depend on shower depth (shower depth (50GeV electrons, eta=1.212550GeV electrons, eta=1.2125):):
We confirm L.Carminati’s findings
26-May-2005 EM Resolution Studies 7
Loss between Strips and PS also Loss between Strips and PS also depends on depth depends on depth (50GeV electrons, (50GeV electrons, eta=1.2125):eta=1.2125): : :
26-May-2005 EM Resolution Studies 8
Longitudinal leakage vs Longitudinal leakage vs depthdepth
26-May-2005 EM Resolution Studies 9
Accordion Sampling Fraction vs Accordion Sampling Fraction vs depthdepth
26-May-2005 EM Resolution Studies 10
3x7 EM Energy alas ATLAS 3x7 EM Energy alas ATLAS 50GeV e50GeV e
3210
1EEE
SFEWbE
accpresrec
=1.88%
26-May-2005 EM Resolution Studies 11
Caution: the PS weight and offset Caution: the PS weight and offset include downstream lossesinclude downstream losses
actPS
beforeSloss
actPS
passivePS
actPS
SbetweenPSloss
upstreamPSloss
accPSrec
E
E
E
EEEEW
EEESF
EWbE
11
0
3210
1
We obtain W0 and b by fitting Eps versus Eloss: by doing that we obtain weights very similar to the ones in ATLAS
26-May-2005 EM Resolution Studies 12
What we should be doing What we should be doing instead is:instead is:
accacc
SPSLossPSact
PS
pasPS
actPS
PSactPS
uptoPSLoss
rec ESF
EEE
EEE
E
EbE
11
Or even better, to correct for “out-of-cone” energy fluctuations:
accacc
SPSLossPSact
PS
pasPS
actPS
PSactPS
uptoPSLoss
outconerec ESF
EEE
EEE
E
EbEE
11
Presampler Linearity valid up to 3-4X0
Smaller additional corrections: Longitudinal Losses + SF correction
26-May-2005 EM Resolution Studies 13
Now use the true Eloss between the S1 and Now use the true Eloss between the S1 and PSPS
accacc
SPSLossPSact
PS
pasPS
actPS
PSactPS
uptoPSLoss
rec ESF
EEE
EEE
E
EbE
11
True Eloss
=1.45%
26-May-2005 EM Resolution Studies 14
Now use all cells to remove out-of-cone Now use all cells to remove out-of-cone effectseffects
accacc
SPSLossPSact
PS
pasPS
actPS
PSactPS
uptoPSLoss
rec ESF
EEE
EEE
E
EbE
11
True Eloss
=1.32%
26-May-2005 EM Resolution Studies 15
Now use all cells and ATLAS Now use all cells and ATLAS calibrationcalibration
=1.74%
3210
1EEE
SFEWbE
accpresrec
26-May-2005 EM Resolution Studies 16
Summary of EM Resolution Loss at Summary of EM Resolution Loss at eta=1.2125eta=1.2125
Electron EnergyElectron Energy 20GeV20GeV 50GeV50GeV3x7 EM Resolution3x7 EM Resolution 2.88%2.88% 1.88%1.88%3x7 EM Resolution no 3x7 EM Resolution no losses between PS and losses between PS and S1S1
2.23%2.23% 1.45%1.45%
Approx. Optimum EM Approx. Optimum EM Resolution (*)Resolution (*)
2.12%2.12% 1.32%1.32%
Loss due to Eloss Loss due to Eloss between S1 and PSbetween S1 and PS
-23%-23% -23%-23%
Loss due to out-of-cone Loss due to out-of-cone fluctuationsfluctuations
-5%-5% -9%-9%
(*) Only dE/dx, i.e. no noise, no pile-up, no charge effects etc.
~9.5%/sqrt(E)
26-May-2005 EM Resolution Studies 17
Resolution vs Depth for 3x7 Resolution vs Depth for 3x7 clusters clusters ((50GeV electrons, eta=1.212550GeV electrons, eta=1.2125))
Strong correlation between resolution and shower depth when we reconstructusing the present ATLAS parametrization
Weak correlation between resolution and shower depth when we remove the effects of Elosses between Strips and PS
26-May-2005 EM Resolution Studies 18
Eloss between S1-PS from TestBeam sqrt Eloss between S1-PS from TestBeam sqrt parametrization (T.Carli) parametrization (T.Carli)
accacc
SPSLossPSact
PS
pasPS
actPS
PSactPS
uptoPSLoss
rec ESF
EEE
EEE
E
EbE
11
Eloss from TBeam parametrization
=1.66%
acc
SPSs E
EEWc 1
Significant (12%) improvement!
26-May-2005 EM Resolution Studies 19
Photons (Photons (L.Carminati @SlovakiaL.Carminati @Slovakia))
Presampler Weight W0 is 10% less for photons. The accordion SF is the same for electrons and photons.
This explains why the photons in ATLAS today are overcorrected by about ~1% (we use electron calibration).
26-May-2005 EM Resolution Studies 20
SummarySummary
EM energy resolution deteriorates at EM energy resolution deteriorates at high eta due to the presence of upstream high eta due to the presence of upstream material which significantly increases material which significantly increases fluctuations of energy losses.fluctuations of energy losses.
At eta=1.2 we found for electronsAt eta=1.2 we found for electrons ~23% resolution loss due to fluct. of Eloss between
PS-S1 ~9% resolution loss due to fluct. of Eloss out-of-cone
Fluctuations correlate with (a definition Fluctuations correlate with (a definition of) the shower depth.of) the shower depth.
Test-beam material scans very important Test-beam material scans very important for testing potential corrections.for testing potential corrections.
26-May-2005 EM Resolution Studies 21
Supporting ViewgraphsSupporting Viewgraphs
26-May-2005 EM Resolution Studies 22
Presampler Linearity at Presampler Linearity at eta=1.2125eta=1.2125
Offset=160MeVW0=4.911
26-May-2005 EM Resolution Studies 23
Sqrt correction from TBeam Sqrt correction from TBeam 0202
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