Semileptonic Analysis from Low Intensity Run

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Semileptonic Analysis from Low Intensity Run

• Anne Dabrowski
• Northwestern University
• NA48 Collaboration Meeting
• 26 February 2004

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Want to measure Vus using K? e?p0 and K?
µ?p0 events

• Measuring Vus involves
• Br (K?e?p0) and Br (K?µ?p0)
• Goal measure ratio
• e?p0 / (pp0 µ? ppp .)
• Goal measure ratio
• µ?p0 / (pp0 µ? ppp .)
• Extract the Form Factors
• Step for NOW
• Study e?p0 pp0 µ?p0
• Want small backgrounds, high acceptance
• Systematic error contribution less than 1/1000
• Good understanding of the MC and the DATA

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Outline of Talk

• Data Quality Check
• Trigger Efficiency
• Selection
• Acceptance
• Backgrounds
• Ongoing work
• Radiative corrections
• MC tuning

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Proton Intensity for Special Run

• Data from Special run 15746 15747 1800 bursts.
• Low intensity (I/8)
• Trigger Q1/4 or 1 Trackloose/100 something
  else.
• Data for this talk is non-reprocessed data

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DATA Quality issues

• NOTE
• We do NOT apply cut on the difference between
  track and cluster time

Due to the difference between the track and
cluster (associated to the track) time varies
with E/P as seen here.
E/P
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The difference between Track and Cluster time for
each channel
pp0 events
Mean 0.6 Rms 1.3
e?p0 events
Mean 1.5 Rms 0.5
µp0? events
Mean -0.2 Rms 1.6
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Cluster times among themselves fine

• Plot of the difference in the time of the 2
  gammas

pp0 events
Mean -0.4 Rms 0.5
e?p0 events
Mean -0.5 Rms 0.5
µp0? events
Mean -0.4 Rms 0.5
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Timing a function of EOP

• Since timing varies as a function of EOP (energy
  in LKR of cluster), we do not cut on the
  difference between track and cluster time for
  clusters associated to tracks.
• We would have to have a separate timing cut for
  each channel
• This would cause bias
• Needs investigation, not believe to be such a
  problem right now, because of the low intensity
  and low accidental activity.

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Trigger Efficiency

• Trigger Q1/4 or 1 Trackloose/100 something
  else
• Data for this talk on non-reprocessed data

pp0 (99.900.02-0.01) e?p0 (99.85
0.06-0.06) µ?p0 (99.880.04-0.04)
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Current Selection in Summary

• Data from Special run 15746 15747 1800 bursts.
  Low intensity (I/8)
• Trigger Q1/4 or 1 Trackloose/100 something
  else
• Data for this talk is non-reprocesed data
• MC used is CMC003 version released on 2 February
  2004

pp0 e?p0 µ?p0
Number good events 556887 111161 48840
Acceptance (using cmc003 release 2 February 2004) (25.680.19) (13.540.01) (14.090.01)
Trigger Efficiency (99.900.02-0.01) (99.850.06-0.06) (99.8770.041-0.04)
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Selection

• Classify all single track events WITH a single
  p0, as either
• pp0
• e ?p0
• µ?p0
• events.
• Future work will include e ?p0 ? and µ?p0 ?
• Future it is hoped to implement a particle decay
  ID probability for each Kaon event in your
  detector.
• Preferably only kinematic cuts
• Avoid cuts in Dalitz plane (extract form factors)
• Similarly, avoid cuts on COM energy (sensitive
  radioactive corrections)
• Treat event classification of selection and
  normalization as close as possible to cancel
  systematic inefficiencies.

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Treatment of Tracks

• Cuts
• 1 track events (not ghost track)
• Hodoscope Track in time window of event (-15.5
  19.5) ns
• Track Time min max (-17.5, 19.5) ns
• Standard fiducial volume of every sub detector
  (see Appendix)
• Track Quality gt 0.7
• CDA from dx/dz and dy/dz
• CDA cut lt 1.5
• Min Max z vertex (-2500 8000.) cm
• Min Max X vertex (-1.8 1.8) cm
• Min Max y vertex (-1.8 1.8) cm

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Treatment of Gammas

• Use Michal Szlepers LKR energy scale (see talk
  M. Szleper)
• Look for a p0 candidate using charged vertex.
• In the case of pp0
• Loop over all in time good gammas to find a
  good pizero mass
• In the case of e?p0 and µ?p0
• Select only 2 in time good gammas
• Good gamma is
• Energy (1.5, 65.) GeV
• Sep distance gt 10 cm
• Evt time Gamma time (-2.4, -0.3) ns
• Timing between themselves (-1.5, 1.5) ns
• Cut on pizero mass (0.128, 0.142) GeV

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So we have a event with a track and a p0. What
next?
Exploit differences in kinematics
pp0
pp0
e?p0
e?p0
µp0?
µp0?
Scale in y arbitrary
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COM energy of pizero
Visible energy of event
pp0
e?p0
µp0?
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Neutrino mass Constraint
The neutrino mass squared is calculated with the
assumption of the mass of the particle associated
the that track. Assuming 60GeV of the Parent
Kaon. Mis-ID of track mass gives skewed
distribution to neutrino mass.
Assuming p mass e mass µmass
pp0 MC
ep0? MC

µp0? MC
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PT vs P plane
Invariant mass of Track and Pizero
e?p0 or µp0?
pp0
pp0
µp0?
ep0?
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Check 1.IS Combination of 1Track and p0 a pp0
event ?

• K? pp0 is most constrained channel (no missing
  energy). My selection algorithm checks for these
  events first.
• Cuts
• Masskaon (Mkaon-0.2, Mkaon0.2) GeV
• Momentum (10 , 50) GeV
• (min cut of 10 if for efficient MUV status)
• PT Track (0.0 , 0.215) GeV
• PT p0 (0.0 , 0.22) GeV
• Nu mass min max (-0.0025 , 0.001) GeV
• Energy of p0 (10 , 50) GeV
• Particle ID
• EOP gt 9.5 candidate Ke3 event (not considered as
  a pp0 candidate)
• MUV Status candidate Kmu3 event (not considered
  as a pp0 candidate )

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Note Particle ID Cuts

• We choose to use particle ID (EOP and MUV status
  check)
• Although this introduces the need for an
  efficiency study into these cuts, without these
  cuts, you get a 2 contamination
  (mis-identification) of Ke3 and Kmu3 events as
  pipi0.
• Possibility to implement the neural network in
  future.

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Check 2Is event e?p0 or µ?p0 candidate ?

• IF the event fails the pp0 event ID ? then
  candidate for e?p0 or µ?p0 selection check

• Cuts Ke3
• P min max (5.,40.) GeV
• Pt Track min max (0.01,0.2) GeV
• PT p0 min max (0.01,0.23) GeV
• Nu mass min max (-0.012,0.012) GeV
• Energy of p0 gt 10. GeV
• COM energy p0 lt 0.27 GeV
• COM energy Track lt 0.22GeV

• Cuts Kmu3
• P min max (10.,40.) GeV
• (min cut of 10 if for efficient MUV status)
• Pt Track min max (0.02,0.2) GeV
• PT p0 min max (0.02,0.22) GeV
• Nu mass min max (-0.01,0.01) GeV
• Energy of p0 min max (10.,40) GeV
• COM energy p0 lt 0.24 GeV
• COM energy Track lt 0.23GeV
• Kaon mass lt 0.45 GeV

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DATA / MC comparison momentum of Track
pp0
e?p0
µp0?
Check quality of low momentum events
CMC003 mc rad cor on MC dots in above plot Ratio
Data/MC
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DATA/MC comparison energy of p0
pp0
µp0?
e?p0
CMC003 mc rad cor on MC dots in above plot Ratio
Data/MC
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DATA/MC comparison PT of p0
pp0
µp0?
e?p0
CMC003 mc rad cor on MC dots in above plot Ratio
Data/MC
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DATA/MC comparison PT of Track
pp0
µp0?
e?p0
CMC003 mc rad cor on MC dots in above plot Ratio
Data/MC
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DATA/MC comparison COM energy p0
pp0
µp0?
e?p0
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Naïve Background Contributions
pp0 events coming through e?p0 2.1x10-3
pp0 events coming through µ?p0 2.9x10-3
e?p0 and µ?p0 events coming through pp0
4.7x10-4
Other channels checked, and not a significant
source of background e ?p0 ? and µ?p0 ?
channels are sources of background but are
missing from MC.
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Acceptance for channels as a function of PT pp0
e?p0
pp0
µp0?
pp0 e?p0 µ?p0
Acceptance (using cmc003 release 2 February 2004) (25.680.19) (13.540.01) (14.090.01)
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Radiative Corrections Ke3 1/2
Radiative Corrections have been applied by
Stoyan. Based on treatment by Ginsberg. Plot
shows the effect of radiative corrections to the
mass of the e?p0 More work will be done to check
radiative corrections by V Bytev
arXivhep-ph/0210049 . in the cmc. Need to
generate e?p0 ? separately too.
pp0
µp0?
ep0?
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Radiative corrections Ke3 2/2

• The existing calculations were E.S.Ginsberg and
  T.Becherrawy in the late 60s
• Their results for corrections to the decay rate,
  Dalitz plot, pion and positron spectra disagree,
  in some places quite sharply for example
  Ginsbergs correction to the decay rate is .0.45
  while that of Becherrawy is .2 (corresponding to
  corrections to the total width of 0.45 and 2
  respectively).
• Work will be done with Rosners Student at
  U-Chicago and Earl Swallow to help understand and
  implement the corrections.

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Radiative Corrections Kmu3

• Radiative Corrections have been coded by Mengkei
  at Northwestern, and are being debugged. They
  are the corrections of Ginsberg.
• Phys Rev D Vol1 Number 1 1 Jan 1970 p220
• The Effect of radiative corrections to Kmu3 less
  than that of Ke3.

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TO do list

• MC tune up of beam
• Great improvement from Dmitri with the
  introduction of new turtle description of Turtle
• Northwestern will help tune beam (shift at DCH1
  in y known problem of cmc tuning group)
• Check MC / DATA energy scale in LKR
• Implement µ?p0 radiative corrections
• Carefully re-examine new papers out of e?p0
  radiative corrections to understand treatment
• e ?p0 ? and µ?p0 ?