Update Kmu3 Branching Ratio measurement

Anne Dabrowski Northwestern University Collaboration Meeting 22nd February 2005 Update Kmu3 Branching Ratio measurement A. Dabrowski, February 22 2005

Strategy: Measure Kmu3 Br normalised to pipi0 • Test 2 Particle ID muon strategies: • Muon Veto as Muon ID • Check muon veto status 1 or 2 • Timing association of 2ns for track between muon veto and hodoscope time • LKR and HAC as Muon ID • Use the mip signal in calorimeters: • LKR < 1.5 GeV and HAC < 5 GeV for the cluster associated to the tracks.. • Requirement for signal and normalisation: • 1 track and 1 pi0 • Kinematic cuts using LKR and DCH A. Dabrowski, February 22 2005

Data Sample • Compact 7.2 & Database pass 5 Min bias 2003 (15745,15746 and 15747) • Alignment • E-baseline correction • Bad burst • Alphas and betas • Projectivity and Blue Field • MC Sample: • Ginsberg correction to Kmu3 – Evelina Marinova finalized correction that Mengkei started • DCH resolution from Eddy, and latest official updates • Michal’s low energy correction to MC (not in presented Dec 2004 numbers) A. Dabrowski, February 22 2005

Simple selection wanted....Common for Kmu3 and pipi0 • Track Section (no extra tracks allowed): • 1 track after excluding Ghost-tracks • Hodoscope time window (-17. 20. ns) • Track quality > 0.8 CDA < 2.5 , Beta, alpha corrections from database • x,y vertex (-1.8,1.8) cm , z vertex (-500,8000)cm • Blue Field correction applied • Pi0 Selection (extra gammas allowed for both) • Energy of gamma (3, 65) GeV • Separation between gammas > 10 cm • Time difference between gammas (-5., 5.) ns • Pi0 mass cuts at 3 sigma and depends on pi0 energy • For this talk I use Michals cut, and cut 3 sigma, In dec meeting, I used my old 2004 pi0 cut for the official numbers • Projectivity correction • Latest Energy scale by Michal A. Dabrowski, February 22 2005

Difference between Kmu3 and Pipi0 selection • Kaon Mass (0.475,0.515) GeV • Mom (10, 50) GeV • PT track < 0.215 • Nu mass (-0.0025, 0.001) GeV2 • Distance between track & gammas > 35 cm • PT pi0 < 0.220 • E/P < 0.95 • Use muon rejection only when the muon veto in used in the Kmu3 analysis. • Kaon Mass (assuming pi) <0.475 or >0.515 GeV • Mom (10, 40) GeV • PT track (0.0, 0.2) GeV • Nu mass (-0.01, 0.01) GeV2 • Dist between track & gammas > 10 cm • Energy pi0 < 40 GeV • COM pi0 < 0.24 GeV • COM Track < 0.23 GeV • Mass of mu pi0 < 0.445 GeV • Particle ID for muons (2 methods used) A. Dabrowski, February 22 2005

Method 1: Muon ID using the Muon Veto • Muon ID efficiency calculated using Kμ2 sample from min bias run; • check status 1 or 2 and 2 ns between hod time and muon veto time • Kinematic cuts Momentum (10,40) • Banana PT vs P cut (Luca) • Mass ν2 (-0.02;0.01) GeV2 • Event Timing and Fiducial cuts as in Kmu3 Br analysis • Efficiency between 0.997 and 0.998 • IN MC 6.4m decay volume, particle decay not simulated – Apply a correction to mc acceptance • See Michal Talk Torino A. Dabrowski, February 22 2005

Method 2: Muon ID signals using the LKR and HAC • Cuts chosen • LKR < 1.5 GeV and HAC < 5 GeV • Muon sample using Kμ2 events from min bias run. • Kinematic cuts • Momentum (10,40) • Banana PT vs P cut • Mass ν2 (-0.02;0.01) GeV2 • Muon Veto requested • Event Timing and Fiducial cuts as in Kmu3 Br analysis A. Dabrowski, February 22 2005

Method 2: Muon ID efficiency using the LKR and HAC • Muon ID requirement: • LKR (cluster<1.5 GeV) and HAC (cluster<5.0 GeV) • Muon ID is energy dependent with max ~0.987 • Analysis done bin by bin in momentum Method 1 eff at 0.998 Corrected bi-nomial errors A. Dabrowski, February 22 2005

Method 2: Pion mis-identification as muons using the LKR and HAC • Pions can be to mis-identified as muons • Need a pion mis-identification probability, and background subtraction. • Sample used for calculating the mis-identification probability • Pions from my standard pipi0 selection, with the muon Veto requirement. • Plus a tighter Kaon mass cut for this sample (0.485, 0.505 GeV). • Event Timing and Fiducial cuts as in Kmu3 Br analysis Corrected bi-nomial errors A. Dabrowski, February 22 2005

Main difference between this and the dec meeting: • 1. the pipi0 acceptance is defined as just those events for which the pi+ does not decay .. So pipi0dk is a background to pipi0. • For all analysis, the Number events = Ns(1+Ns/Nb) is used.

Comparison in result between 2 methods K+ Muon Veto LKR HAC A. Dabrowski, February 22 2005

Comparison in result between 2 methods K- Muon Veto LKR HAC A. Dabrowski, February 22 2005

Br Result Muon Veto LKR HAC • The error statistical and includes: • Data sample • MC statistics • Errors in particle ID efficiency • No systematic errors have been included • I must still propagate the errors due to the background • And the “not decay after lkr error” A. Dabrowski, February 22 2005

My to do – and questions My own pi0 mass cut as a function of energy (right now using Michals – possible source for decrease of events in data? Have to check, will check changes in data base / compact why events have decreased since dec meeting) The Br as a function of momentum When kmu3 is a source of background – see the effect of the kmu3 Br from PDG used in the analysis (higher order todo) Vertex in data/mc problem The factor to correct for particles not decaying after lkr in MC – need to checked if a small correction should be applied to LKR/HAC case –for the region between lkr and hac … for the pipi0dk and pipi0pi0dk backgrounds. Right now not corrected. Re-measure the correction for decay not simulated in MC as a check. Check sensitivity to vertex and pt cuts A. Dabrowski, February 22 2005

Pion ID efficiency E/P < 0.95 (common to both analysis methods) • Pion ID efficiency calculated using pipi0 sample from min bias run. • Kinematic cuts (as in my selection) • Muon veto requirement to reject muons • But have a tighter Kaon mass cut for this sample (0.485, 0.505 GeV). • Event Timing and Fiducial cuts as in Kmu3 Br analysis Corrected bi-nomial errors A. Dabrowski, February 22 2005

Update Kmu3 Branching Ratio measurement