Status of K ± p ± p 0
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Transcript of Status of K ± p ± p 0
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Status of K± ±0
E. De Lucia
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PDG fit BR(K±) = (21,13 ± 0.14)% BR/BR = 6,6x10-3
CHIANG ’72 BR(K±) = (21,18 ± 0.28)% BR/BR = 1,3x10-2
• Self-tag on one side using K- (nuclear interactions)•Vertex with 2 tracks in DC on the signal side
Strategy
Fitting the distribution of the momentum of the secondary track (p*) in the kaon reference frame we can extract BR(K±)
The selection efficiency is only related to DC reconstruction:• tracking efficiency • vertex efficiency
Method:
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The method
MCLIKE-DATA
MCTRUE
DATA εε
ε
1) peak: p*( mass) distribution from “-cluster” sample
2) peak: p*( mass) distribution requiring the
3) 3-body decays: p*( mass) distribution from MC
VTXTRKTAG
FITππ0
ε1
cut)*ε(p1
N
N)ππBR(K
fit windowp* cut
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shape (1)and180 < E < 230 MeV .and. cos< -0.95 .and. (Emiss-Pmiss)< 30 .and. |tof_mass2| < 104 MeV
p*(MeV)
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shape (2)
DATA
Systematic uncertainty can be estimated from the fluctuation of N obtained from the shape obtained varying the previous cuts
MC
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Fit stability1)“run by run” : MC runs for 2002 data have been
divided in 12 groups called “runs”
2) “by range” : changing the starting point of the fit
window
from 150 MeV up to 190 MeV using 5 MeV steps
3) “by shape” : using different shapes for the 0 peak
obtained changing the selection cuts
a) N0/Ntag from the fit
b) N0/Ntag from the fit corrected for p* window cut (correction from 0 “data-like” shape …agreement with 0 MC true shape )
FITTAG
0
NNππ
Compare the MC true numbers with :
)*ε(p1
NNππ
CUTFITTAG
0
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Fit stability: “run by run” (I)
“Run number”
FITTAG
0
NNππ
)*ε(p1
NNππ
CUTFITTAG
0
“Run number”
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Fit stability: “run by run” (II)
FITTAGNN
)*ε(p1
NN
CUTFITTAG
“Run number”
“Run number”
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Fit stability: “by range” (I)
FITTAG
0
NNππ
)*ε(p1
NNππ
CUTFITTAG
0
different fit window
different fit window
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Fit stability: “by range” (II)
FITTAGNN
)*ε(p1
NN
CUTFITTAG
different fit window
different fit window
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Fit stability: “by shape” (I)
FITTAG
0
NNππ
)*ε(p1
NNππ
CUTFITTAG
0
different shape
different shape
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Fit stability: “by shape” (II)
FITTAGNN
)*ε(p1
NN
CUTFITTAG
different shape
different shape
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Reconstruction efficienciesVertex efficiency fromneutral vtx sample
Kaon tracking efficiencyextrapolating from tag side
pKthetaK
P secondary (MeV)
With MC 2002 : 0.05%39.42εMC2002
REC TRUE 0.13%38.65ε
MC2002
VTXTRK
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Using the MC (2002)Stability vs fit window(lower edge from 150 to 190 MeV)
0.13 21.18 )ππBR(K
0.1463.47 μν)BR(K0
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0.13 21.21 )ππBR(K
0.1263.70 μν)BR(K0
Stability vs fit window(lower edge from 150 to 190 MeV)
Using the DATA (2002)
p*(MeV)
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Zoom on the peaks
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To do listConcerning the fit:1)Finalize systematic uncertainty on the fit results using the “by shape” stability on data
Concerning efficiencies:
1)Vertex is healthy next step : use kinematic fit2) Tracking now using overall number (all decay
channels) next step: work on neutral vertex sample to get
directly the efficiency for 0 decay 3) efficiencies on run by run basis to study stability of
B.R. measurements
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B.R.’s vs 2002 data taking periods
Using corrections fordata efficiencies but mean MC corrections for each point …
need MC corrections for different periodspossible with the 1:1MC production
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Using DATA 2002