Status of K ± p ± p 0
description
Transcript of Status of K ± p ± p 0
Status of K± ±0
E. De Lucia
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:
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
shape (1)and180 < E < 230 MeV .and. cos< -0.95 .and. (Emiss-Pmiss)< 30 .and. |tof_mass2| < 104 MeV
p*(MeV)
shape (2)
DATA
Systematic uncertainty can be estimated from the fluctuation of N obtained from the shape obtained varying the previous cuts
MC
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
Fit stability: “run by run” (I)
“Run number”
FITTAG
0
NNππ
)*ε(p1
NNππ
CUTFITTAG
0
“Run number”
Fit stability: “run by run” (II)
FITTAGNN
)*ε(p1
NN
CUTFITTAG
“Run number”
“Run number”
Fit stability: “by range” (I)
FITTAG
0
NNππ
)*ε(p1
NNππ
CUTFITTAG
0
different fit window
different fit window
Fit stability: “by range” (II)
FITTAGNN
)*ε(p1
NN
CUTFITTAG
different fit window
different fit window
Fit stability: “by shape” (I)
FITTAG
0
NNππ
)*ε(p1
NNππ
CUTFITTAG
0
different shape
different shape
Fit stability: “by shape” (II)
FITTAGNN
)*ε(p1
NN
CUTFITTAG
different shape
different shape
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
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
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)
Zoom on the peaks
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
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
Using DATA 2002