Update on Beamtest 06 CU PSF study C. Cecchi S. Germani M. Pepe Università di Perugia and INFN Gamma-ray Large Area Space Telescope Beam Test Worksop II May 15-17, 2006

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 2 Simulated 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 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 3 Basic 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 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 4 Vertex 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 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 5 Energy and Direction Reconstructed Energy compare EvtEnergyCorr TagEnergy (BeamEnergy – E_rec) Photon Direction derived using first two tag detectors (P tag ) PSF defined from angular error: – good Vertex acos(P tag · P Vtx ) – best Track acos(P tag · P Tkr1 )

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 6 Tagger Silicon Detector

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 7 Angle Error (Vtx Scaled) 2 GeV (SLAC) 2.5 GeV 1 GeV

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 8 McEnergy (e- 2.5 GeV) 0 deg40 deg McEnergy =ΣMcEγ MultiGamma Any M_gam One Gamma M_gam==1 The MultiGamma effect is small we can neglect to distinguish between 1 and multigamma events

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 9 Energy Rec. Comparison 1 Gamma 0 deg40 deg e- 2.5 GeV Resolution of the tagger worse at low energies wrt EvtEnergy visible in the scaled PSF

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 10 Tagger Energy 40 deg Tagger Energy = BeamEnergy–E_rec 0 deg e- 2.5 GeV

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 11 EvtEnergyCorr 0 deg 40 deg 20 deg e- 2.5 GeV

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 12 McDirErr – Measured DirErr e- 2.5 GeV Vtx Events

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 13 Tagger Selection (4Si vs 2Si) 0 deg Requiring e_silicon>0 (signal) only from the first two Tagger Planes does not affect the PSF ! e- 2.5 GeV

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 14 Electron Beam 2.5 GeV Vtx Events Tkr Events

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 15 SLAC Mass Production vs 2.5 GeV

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 16 e- 2.5GeV – 2GeV – 1 GeV e- 2.5GeV – 2GeV – 1 GeV

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 17 Evaluating PSF Error The number of events within 68% is N 68 The error on N 68 is ΔN 68 =sqrt(N TOT ×0.68×(1-0.68)) [Binomial] ΔPSF 68 is obtained computing the quantiles corresponding to a number of events equal to N 68 ±ΔN 68 68% PSF68

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 18 PSF Error one beam energy vs all Vtx 0 deg Goal Error Level

Beam Test Worksop 2Pisa, May 16th, 2006 C. Cecchi S. Germani M. Pepe 19 Conclusions 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