E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Updates on BR(KUpdates on BR(K++ππ++ππ00))
E. De LuciaE. De Lucia
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
PDG fit ‘06 BR(K±±0) = (20,92 ± 0.12)% BR/BR = 5,7x10-3
CHIANG ’72 BR(K±±0) = (21,18 ± 0.28)% BR/BR = 1,3x10-2
N.B. This decay enters in the normalization of BR(KN.B. This decay enters in the normalization of BR(Kl3) by NA48, ISTRA+, E865l3) by NA48, ISTRA+, E865
•Self-triggering K-tag• Fitting the distribution of the momentum of the charged decay particle in the kaon rest frame assuming the pion mass (p*)
Method:Method:
The starting pointThe starting point
• Global efficiency TRK+VTX from K±X±0 decay vertex technique:
asymmetric p*(0) cut (old method) ~~12% correction from mc_method/mc_true 12% correction from mc_method/mc_true + 11% Kl3 contamination11% Kl3 contamination
d_fromClu cut (new method) ~~1% correction from mc_method/mc_true 1% correction from mc_method/mc_true + 3% Kl3 contamination3% Kl3 contamination
• The shape for the The shape for the peak: old vs new method peak: old vs new method investigating on the results obtainedinvestigating on the results obtained
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
1)1) ttag on one side with Kag on one side with Kpreselection
-zPCA 20cm - PCA 10cm - pK (70,130) MeV
selection - VTX (40,150) cm - dp (-320,-120) MeV - p(m) (180,270) MeV
self-triggering tag (2 trigger sectors fired)
2) look for signal on the other sidelook for signal on the other side vertex in fiducial volume VTX (40,150) cm
kaon track can be extrapolated to the I.P. (time info)
Signal selectionSignal selection
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
MCMETHOD
MCTRUE
DATA ε
εε
1) peak: p*( mass) distribution from “-cluster” sample2) peak: p*( mass) distribution requiring the
3) 3-body decays: p*( mass) distribution from MC
N.B. for 1) and 2) bin by bin MC corrections are applied.
fit windowp* cuttagb estimated from MC kpm04
The methodThe method
tagb
1
cut)*(pε1
N
N)ππBR(K
DCTAG
FITππ0
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
MC bin by bin correction: MC bin by bin correction: old old shapeshapeThe final shape used in the fit (shapeshapeFITFIT) is obtained applying a bin by bin MC correction to shape from the DATA control sample (shapeshapeDATADATA), accounting for distortions due to the control sample selection
DATA
π0)(vtxshapeπ0)(shape
π0)x(vtxshapeshape MC
MCDATA FIT
p* (MeV)
π0)(vtxshapeDATA
Larg
e MC
Larg
e MC
corre
ctions n
eeded
corre
ctions n
eeded
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
X0 decay vtx selection d_fromClu < 28 cm vertex from signal selection
green = mc truered = selected
p*(MeV)
Smaller M
C
Smaller M
C
Correcti
on needed
Correcti
on needed
MC bin by bin correction: MC bin by bin correction: new new shapeshape
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Conclusions: Conclusions: last meetinglast meetingThe quality of the fit on the peaks is poor
The disagreement on the 0 and peaks signalsthe difference between DATA and MC resolutions
The population of each bin of the p*+ distribution used forthe extraction of the MC bin by bin correction is crucial
Several methods to improve the situation have been tried but unfortunately without the desired result
Possible solutions:1)1) smearing the MC true distribution of p*smearing the MC true distribution of p*+ with the resolution+ with the resolution measured on DATA (using the measured on DATA (using the from EMC selection)from EMC selection)2) increase the bin width for the MC bin by bin corrections3) ….
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Output of the fit: Output of the fit: last meetinglast meeting
With the new shape
The number of 0 increases
The difference is larger intwo sub-samplesdetailed investigation needed
The number of remains stable
sub-sample
Looking at the 7 sub-samples of 25 pb-1 each of 2002 data
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Output of the fit: Output of the fit: todaytoday
sub-sample
Looking at the 7 sub-samples of 25 pb-1 each of 2002 data
Now the raw counters Now the raw counters from the two shapes from the two shapes are in agreementare in agreement
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Output of the fit: Output of the fit: last last meetingmeeting
p*(MeV)
residuals
normalized residuals
Old shapeOld shape
p*(MeV)
residuals
normalized residuals
New shapeNew shape
25 pb-1
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Output of the fit: Output of the fit: todaytoday
p*(MeV)
residuals
normalized residuals
Old shapeOld shape
p*(MeV)
residuals
normalized residuals
New shapeNew shape
25 pb-1
We have improved the quality of fit and the residualsWe have improved the quality of fit and the residuals
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
What have been doneWhat have been done1)Smearing parameters to be applied to the MC momenta have been obtained from the simultaneous fit of the p*distributions from data control samples of 0 and decays 2) Check the number of events used for the bin by bin correction evaluation.
Then going back to the fit of p*distribution to extract NFIT
a) for and 0 shapes, the smearing parameters have been used to evaluate the MC bin by bin corrections
b) for the shape of 3-body decays, the MC smeared distribution is used
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
MC smearingMC smearing
Applying a smearing to the MC momenta in the lab:the 0 peak in the p* distribution from DATA is very well reproduced while the peak still exhibits a disagreement
sample sample
DATA MC
DATA MC
p*(MeV)
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
MCMETHOD
MCTRUE
DATADC εε
εcut)*(pε
tagb
1
cut)*(pε1
N
N)ππBR(K
DCTAG
FITππ0
Results on 2002 DATA Results on 2002 DATA samplesample
syststat 0.00010.00051.0106tagb
p*(MeV)
0.06521.048)ππBR(K 0
1912818347NFITππ
12113686 NTAG
MeV 180 cut*p
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
MCMETHOD
MCTRUE
DATADC εε
εcut)*(pε
tagb
1
cut)*(pε1
N
N)ππBR(K
DCTAG
FITππ0
Results on 2002 DATA Results on 2002 DATA samplesample
syststat 0.00010.00051.0106tagb
0.06521.048)ππBR(K 0
1912818347NFITππ
12113686 NTAG
MeV 180 cut*p
Fractional Uncertainty
on BR(K0())
Signal counting + Shape Stat 0.23%
Global efficiency 0.15%
Efficiency MC correction 0.13%
Tag bias 0.05%
Total 0.30%
0.00131.0105εεMCMETHOD
MCTRUE
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Peaks on 2002 DATA Peaks on 2002 DATA samplesample
p*(MeV)
p*(MeV)
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Systematic effect (I)Systematic effect (I)Using the 2002 data sample and varying: the starting point of the fit window (p*CUT ) the d_fromClu cut for the efficiency evaluation
p*p*CUT CUT
165 -> 190 MeV/cBR/BR 0.06 %BR/BR 0.06 %
DC DC
cut 28 (26*) -> 32 cmBR/BR 0.24 %BR/BR 0.24 % (0.39%)
(*) distorts the distribution used for efficiency evaluation
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Systematic effect (II)Systematic effect (II)Using the 2002 data sample and comparing the results obtained with the New and the Old 0 shapes
New vs Old shapeNew vs Old shapeusing the same d_fromClumaximum differencemaximum differenceBR/BR 0.16 %BR/BR 0.16 %
new
New vs Old shapeNew vs Old shaped_fromClu = 30 cmand p*= 180 MeVBR/BR 0.07 %BR/BR 0.07 %
old
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Time stabilityTime stabilityLooking at the 7 sub-samples of 25 pb-1 each of 2002 datawe have checked the time stability of the measurement
sub-sample
p0 = 0.21042 ± 0.0005
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Using the whole DATA sample:
13
13
64
64
FLAGT
TAGTAG
FLAGTSIGSIG
TAG
SIG
xNN
xNN
N
N
BR(K0()) BR x CT3
CT3 = 0.9994 0.0003
BRT3FILTER negligible O(10-6)
T3FILTER correction T3FILTER correction
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
SIGTAG
TAGFILFOC
1
1iFILFO
iAFILFO
iAFILFO
i NN
N
CFILFO = 1.00006 0.00032 (DATA)CFILFO = 0.99967 0.00015 (MC)
Using the same set of runs for DATA and MC from BR(K()) studies:
In agreement within the errorsIn agreement within the errors
BRFILFO = 3x10-4BR(K0()) BR x CFILFO
FILFO correctionFILFO correction
The evaluation of CFILFO using exactly the signal selection is ongoing
E. De Lucia Neutral and Charged Kaon Meeting – 7 May 2007
Conclusions and check listConclusions and check list The quality of the fit has been improved applying smearing parameters to the MC momenta measured in the lab. A preliminary measurement of BR(K0()) has been presented Final corrections from cosmic ray veto and FILFO to be applied The evaluation of systematic uncertainties is ongoing:
systematic effects from the selection cuts used for the efficiency control sample (now we have evaluated only for d_fromClu cut) acceptance correction (use mc true value) and efficiency with
K±X±0 decay vertex sample in FV and before DC inner wall systematic effects from the fit :
shape 0 new vs old shape 3 body decays shape starting point of the fit window (p* cut)
cosmic ray veto effect FILFO effect negligible (see K++()) time stability on 2002 data
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