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Ratio of Ke3 to Pipi0. Anne Dabrowski Northwestern University NA48/2 Analysis Meeting 26 May 2005. Outline. Data & MC samples DATA / MC of final selection Trigger Efficiency Particle ID efficiency Br results K+ / K- Error analysis Statistical contributions Inputs from PDG (pizero Br)

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ratio of ke3 to pipi0
Ratio of Ke3 to Pipi0

Anne Dabrowski

Northwestern University

NA48/2 Analysis Meeting

26 May 2005

outline
Outline
  • Data & MC samples
  • DATA / MC of final selection
  • Trigger Efficiency
  • Particle ID efficiency
  • Br results
    • K+ / K-
  • Error analysis
    • Statistical contributions
    • Inputs from PDG (pizero Br)
    • Systematic Errors, stability under variation of selection cuts, and form factor (λ+)
  • Final result
  • Conclusion
data and mc samples
Data and MC samples

Data:

  • Compact 7.2 & Database (database-2005-02-11) pass 5 Min bias 2003 (runs 15745,15746 and 15747)
    • Bad burst
      • Check: DCH,MBX,HODC,LKR,MUV,PMB and MNP33Current ne 0)
      • Reject 31 bursts for which momentum = 10.0 GeV
      • Total number of bursts after bad burst rejection: 2244
    • Alphas and betas
    • Projectivity and Blue Field (Alan algorithm to remove phi dependence)

MC Sample:

    • Ginsberg correction
    • Constants from PDG 2002 for ke3 (λ+ = 0.02760)
    • Pi0 decays according to its branching ratio
    • CMC005 corrections including corrections of May 9th 2005
    • Result based on sample size of 8 M pipi0 and 8 M ke3
    • Pipi0 mc has 0.13% pipi0g (IB) included in it at generation level
common selection for ke3 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 charge 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

Energy scale

Projectivity correction

Calculate neutral vertex for each pair of gammas, and choose gammas based on best difference between charge and neutral vertex

Use this neutral vertex in the blue field routine to correct the slopes of the track (reason: phi dependence studies of Alan)

Common Selection for Ke3 and pipi0
difference between ke3 and pipi0 selections
Kaon Mass < 0.4772 or > 0.5102 (3 sigma from the mean)

Momentum (5, 35) GeV

PT track (0.01, 0.2) GeV

Nu mass (-0.012, 0.012) GeV2

Dist between track & gammas > 10 cm

COM Track < 0.22 GeV

COM pi0 < 0.27 GeV

Mass (eπ0 ) < 0.425 GeV

Particle ID for electrons:

EOP > 0.95 and shower width rms in x and y (0.65 – 0.85)

Difference between Ke3 and pipi0 Selections
  • Kaon Mass (0.4772,0.5102) GeV
  • Momentum (10, 50) GeV
  • PT track < 0.215 GeV
  • Nu mass (-0.0025, 0.001) GeV2
  • Distance between track & gammas > 35 cm
  • PT pi0 < 0.220 GeV
  • E/P < 0.95
electron id
Electron ID

E/P > 0.95 and shower rms cut 0.65 – 0.85 in each of x and y

  • Selected electrons from tight ke3 selection
  • Used same data sample, and timing and fiducial cuts as in analysis
  • Used cuts in analysis plus
    • Mk < 0.465 or mk > 0.525
    • Pt track < 0.175 GeV
    • -0.005 < m nu < 0.00025 GeV^2
    • Mx^2 < -0.0025 GeV^2
    • ECOMpi0 < 0.23 GeV
    • ECOMtrk < 0.17 GeV
    • Mass mupi0 < 0.36 GeV

Global efficiency (96.59 +- 0.14) %

electron id as background for pipi0
Electron ID as background for pipi0

E/P > 0.95 needed for background contribution estimate in pipi0 (pion ID is E/P < 0.95)

  • Selected electrons from tight ke3 selection
  • Used same data sample, and timing and fiducial cuts as in analysis
  • Used cuts in analysis plus
    • Mk < 0.465 or mk > 0.525
    • Pt track < 0.175 GeV
    • -0.005 < m nu < 0.00025 GeV^2
    • Mx^2 < -0.0025
    • ECOMpi0 < 0.23 GeV
    • ECOMtrk < 0.17 GeV
    • Mass mupi0 < 0.36 GeV

Global efficiency (96.70 +- 0.14) %

pion id for background to ke3 estimate
Pion ID for background to ke3 estimate

E/P > 0.9>5 and shower shape needed for background contribution estimate of pipi0 in ke3

  • Selected from tight pipi0 selection:
  • 0.485 < mkaon < 0.505
  • 0.245 < Ecmpi < 0.25
  • Mx^2 > -0.0015

Same timing, data sample, trigger selection and fiducial volume cuts as selection

Global efficiency (0.38 +- 0.16) %

pion id e p 0 95
Pion ID E/P < 0.95

E/P < 0.95 particle ID condition for pions in normalization

  • Selected from tight pipi0 selection:
  • 0.485 < mkaon < 0.505 GeV
  • 0.245 < Ecmpi < 0.25 GeV
  • Mx^2 > -0.0015 GeV^2

Same timing, data sample, trigger selection and fiducial volume cuts as selection

Global efficiency (99.522 +- 0.001) %

trigger efficiency
Trigger Efficiency

Result of two charges combined

  • Main Trigger Q1/4
  • Min bias trigger for trigger efficiency calculation Trackloose/100
result ratio ke3 pipi0
Result (Ratio Ke3/pipi0)
  • The error in the Br includes:
    • Data sample (signal and normalization)
    • Systematic
      • Trigger efficiency
      • MC statistics (8 M pipi0 and 8 M kmu3 of each charge)
      • Errors in particle ID efficiency (particle ID error bin by bin and propagated)
      • Errors due to background subtraction (including particle ID)
  • No systematic errors due to kinematic cuts or form factor changes have been included
result br ke3
Result ( Br Ke3)
  • The error in the Br includes:
    • Data sample (signal and normalization)
    • Systematics
      • Trigger efficiency
      • MC statistics (8 M pipi0 and 8 M kmu3 of each charge)
      • Errors in particle ID efficiency (particle ID error bin by bin and propagated)
      • Errors due to background subtraction (including particle ID)
  • No systematic errors due to kinematic cuts or form factor changes have been included
ratio of ke3 pipi0 as a function of momentum
Ratio of Ke3/ pipi0 as a function of momentum

K+

K-

Χ2/ndf 11.81 / 12

Χ2/ndf 16.99 / 12

estimation of systematic error
Estimation of Systematic Error
  • Systematics considered:
    • Fiducial volume – z vertex cut
    • Low energy neutral energy scale
    • Varying E/P cut for both electrons and pions
    • Parameter describing energy dependence of form factor (λ+ )
low neutral energy scale k
Low neutral energy scale K+

Energy γ 1

Energy γ 2

low neutral energy scale k1
Low neutral energy scale K-

Energy γ 1

Energy γ 2

final result for ratio ke3 pipi0 and br ke3
Final result for ratio Ke3/pipi0 and Br(Ke3)

Recall PDG:

Br(Ke3) = 0.0487+- 0.0006

Br(pipi0) = 0.2113 +- 0.0014

Ratio(ke3/pipi0) = 0.2305+-0.0032

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