Update on Beamtest 06 CU PSF study C. Cecchi S. Germani M. Pepe Università di Perugia and INFN...

Update onUpdate on Beamtest 06 Beamtest 06 CU PSF studyCU PSF study

C. CecchiS. Germani

M. Pepe

Università di Perugia and INFN

Gamma-ray Large Area Gamma-ray Large Area Space TelescopeSpace Telescope

Beam Test Worksop II May 15-17, 2006

Beam Test Worksop 2

Pisa, May 16th, 2006

C. Cecchi S. Germani M. Pepe 2

Simulated DataSimulated Data

BeamtestRelease v1r0801p0– PS simulation from beamtest06 v4r0 (updated)– 4.5M e- generated with E=2.5 GeV /angle(0°, 20°,

40°)– 4.5M e- generated with E= 1 GeV /angle– 800k e- from SLAC pipeline /angle(0°, 40°)

0°

20°

40°

• Analyzed using Gleam v6r12 hit the towers at 3 different Beam Angles (0° and 40° are the same as Mass Production (SLAC))

Beam Test Worksop 2



Basic Event SelectionBasic Event Selection

We used the Merit ntuple after adding PS variables

- goodCal = EvtEnergyCorr>20 && EvtEnergyCorr<BeamEnergy-goodNumTracks = TkrNumTracks > 0-goodTag = e_silicon[i] > 0 i=0, 3

e_silicon[0]e_silicon[1]

e_silicon[3]e_silicon[2]

Beam Test Worksop 2



Vertex and TrackVertex and Track

• Good Vertex Merit Variable VtxStatus = 34 : 2 tracks vertex + two tracks share first

hit 162 : 34 + DOCA location lies inside track hits else use only BestTrack

After cuts we have roughly the same number of events in each of the two categories

Beam Test Worksop 2



Energy and DirectionEnergy and Direction

• Reconstructed Energy compare EvtEnergyCorr

TagEnergy (BeamEnergy – E_rec)

• Photon Direction derived using first two tag detectors (Ptag)

• PSF defined from angular error:

– good Vertex acos(Ptag·PVtx)

– best Track acos(Ptag·PTkr1)

Beam Test Worksop 2



Tagger Silicon DetectorTagger Silicon Detector

Beam Test Worksop 2



Angle Error (Vtx Scaled)Angle Error (Vtx Scaled)2 GeV (SLAC)

2.5 GeV

1 GeV

Beam Test Worksop 2



McEnergy (e- 2.5 GeV)McEnergy (e- 2.5 GeV)

0 deg 40 deg

McEnergy =ΣMcEγ MultiGamma Any M_gamOne Gamma M_gam==1

The MultiGamma effect is small we can neglect to distinguish between 1 and multigamma events

Beam Test Worksop 2



Energy Rec. Comparison 1 Energy Rec. Comparison 1 GammaGamma

0 deg 40 deg

e- 2.5 GeVe- 2.5 GeV

Resolution of the tagger worse at low energies wrt EvtEnergy visible in the scaled PSF

Beam Test Worksop 2



Tagger EnergyTagger Energy

40 deg

Tagger Energy = BeamEnergy–E_rec

0 deg


Beam Test Worksop 2



EvtEnergyCorrEvtEnergyCorr

0 deg

40 deg

20 dege- 2.5 GeVe- 2.5 GeV

Beam Test Worksop 2



McDirErr – Measured McDirErr – Measured DirErrDirErr

e- 2.5 GeVe- 2.5 GeVVtx EventsVtx Events

Beam Test Worksop 2



Tagger Selection (4Si vs Tagger Selection (4Si vs 2Si)2Si)

0 deg

Requiring e_silicon>0 (signal) only from the first two Tagger Planes does not affect the PSF !


Beam Test Worksop 2



Electron Beam 2.5 GeV Electron Beam 2.5 GeV

Vtx Events

Tkr Events

Beam Test Worksop 2



SLAC Mass Production vs 2.5 SLAC Mass Production vs 2.5 GeV GeV

Beam Test Worksop 2



e- 2.5GeV – 2GeV – 1 GeVe- 2.5GeV – 2GeV – 1 GeV

Beam Test Worksop 2



Evaluating PSF Evaluating PSF ErrorError

• The number of events within 68% is N68

• The error on N68 is ΔN68=sqrt(NTOT×0.68×(1-0.68)) [Binomial]

• ΔPSF68 is obtained computing the quantiles corresponding to a number of events equal to N68 ±ΔN68

68%

PSF68

Beam Test Worksop 2



PSF Error one beam energy vs PSF Error one beam energy vs allall

Vtx 0 deg

Goal Error Level

Beam Test Worksop 2



ConclusionConclusionss

• 1 and 2.5 GeV e- simulated on PG-farm 27M analysed • 2 GeV SLAC production 1.6M (e-) analysed

• No difference selecting 1 or M• Tag energy difference only on scaled PSF at low energies• Simulated and reconstructed energies gives same results on

PSF• Selection with only the first two silicon higher photon

energy

• Is 800K e-/angle/energy enough to reach 1% error on PSF?No at low energies...... At higher energies may depend on true rejection

• Cross check results using only not scaled PSF

Update on Beamtest 06 CU PSF study C. Cecchi S. Germani M. Pepe Università di Perugia and INFN...

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