k two body decays
DESCRIPTION
K two body decays. Absolute BR measurements BR( K ) B. Sciascia BR( K p p 0 ) E. De Lucia BR( K p p 0 )/BR( K ) M. Martemianov, V. Kulikov. Barbara Sciascia on behalf of Charged Kaon Working Group KLOE General Meeting - PowerPoint PPT PresentationTRANSCRIPT
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 1
K two body decays
Barbara Sciasciaon behalf of Charged Kaon Working
GroupKLOE General Meeting
Roma - November, 14th 2003
Absolute BR measurements
BR(K ) B. Sciascia BR(K ) E. De Lucia BR(K )/BR(K )
M. Martemianov, V. Kulikov
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 2
K decay:state of the art
Highest K branching ratio (63%) - A single measure exists (Chiang ‘72)
Tag for absolute BR measurements - Tag Bias - -Trigger - Correlation effects - Cosmic veto/T3 correction
2001 and 2002 Data
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 3
Event selection Reconstruction:
FilFo
Tracking 1
EvCl 1 (5 Algos)
“Kaon joining”
EvCl 2 (5 Algos)
Tracking 2
Algorithm 5th: TagDecay Preselection:
-zPCA 20cm - PCA 10cm - pK (70,130) MeV
Selection: - VTX (40,150) cm - dp (-320,-120) MeV - p(m) (180,270) MeV
Systematics: to be studied
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 4
Caveat:
K 63.46
K e 4.86
K 3.27
K 21.08
K 1.73
K 5.548
K Nuclear int. 0.04K 61.32
K e 4.69
K 3.15
K 20.36
K 1.67
K 5.345
K Nuclear int. 3.47
KLOE MC truth K
KLOE MC truth K-
Tag: K- Signal: K
K nucl. interaction not well simulated under 400-500 MeV
Measured by KLOE? (see Patera talk)
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 5
Tag and signal selection
Tag - “recover” K from EvCl2 (TagDecay) - p(m): 3 cut - Trk-to-clu for -track - 2 trigger sectors fired by the
Sig (DC only) - Look for K (TagDecay preselection) - V2 vertex - VTX (40,150) cm - p(m): 3 cut
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 6
K Tag Bias
K 0.1 0.4
K e 0.9 0.4
K 1.3 0.4
K 1.9 0.4
K 6.6 0.4
K 17.7 0.4
K 1.3 0.4
K e 0.1 0.4
K 1.3 0.4
K 0.9 0.4
K 4.5 0.4
K 19.1 0.4
DC selection (p, m mass hypothesis) Trk-to-Clu for track -cluster fires 2 trigger sectors (AutoTrigger)
Tag K Signal K Tag K Signal K
MC: 4 pb-1 for 20 pb-1 of Data
K Tag Bias at the same level
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 7
pions
on calorimeter: Data and MC
muons
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 8
Efficiency- Tag in one side- One “-cluster” different from the tag one: 0 cluster with ECLU (EA,EB) MeV 1 cluster with ECLU (EB,EC) MeV
MC: EA = 20 MeV EB = 120 MeV EC = 370 MeV
Data: EA = 20 MeV EB = 90 MeV EC = 320 MeV
MC vs MC: MC Truth = (28.9 0.1) MC-like-Data = (30.1 0.1)MC-like-Data Corr = (28.8 0.1)
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 9
“Correlation” Tracking seems to correlate Tag
and Signal emispheres Try an estimation from MC Method:
aba
abaaba
aba
p
pp
p
2
1
0
1
1
1211
b
babp
1211
Define a “kind of correlation”, :
Correction to be applied:
- from MC- from Data - typical value: 1.0460.002 (4pb-1of MC, 20pb-1 of data)
DC HW efficiency
Layer
Present MC eff.
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 10
Branching ratio MC (4pb-1) vs MC (4pb-1):
- BR(K) = (63.46 0.40) - BR(K--) = (62.44 0.40) - Remind MC truth: 63.46 and 61.32
Cosmic veto/T3 efficiency: 0.2
2001-2002 Data/MC
K+ () K- ()
NSIG/NTAG (Stat) 0.051 0.053
Efficiency (Stat) 0.059 0.062
Correlation (Stat MC) 0.050 0.051
Tag Bias (Stat MC) 0.076 0.076
Cosmic veto/T3 (Stat)
0.030 0.030
Total 0.12 0.13
BR(K) = (64.84 0.08) BR(K--) = (63.88 0.08)
Very preliminary, for K . . .
waiting for new MC:
HW DC eff. and on calo
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 11
• Self-tag on one side using K- (avoid nuclear interactions)• Vertex with 2 tracks in DC on the signal side
Strategy
Fit the distribution of the momentum of the secondary track (p*) in the kaon reference frame
The selection efficiency is only related to DC reconstruction :• tracking efficiency (see Patera’s talk) • vertex efficiency (ongoing work to be finalized)
Method:
Status of K±±
E. De Lucia
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 12
Difference between Tags
tag –
p* (MeV/c)
x10-2
p* (MeV/c)
tag tag
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 13
DATA vs MC
Clear resolution effects…two possibilities 1) work on resolutions MC wrt DATA 2) use two “clusters” sample
p* (MeV/c)p* (MeV/c)
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 14
2) Use the two”-cluster” sample
a) hp: and peaks have the same resolution function b) p*( mass) distribution for peakc) p*( mass) distribution for peak
p*( mass): peak
p* (MeV/c)
MC
peak fit with p*( mass)
MC
p* (MeV/c)
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 15
In order to extract the number of decays:
1) Estimate the background - require a in the calo and measure the efficiency2) Take into account the 3-body decays contribution - fit the distribution down to 180 MeV in order to have 3-body decays contribution only from kl3 channel
Perform the fit:
a) using the MC shapeb) parametrize it with a Fermi-Dirac distribution (first MC tuned)
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 16
DATA
a) using MC shape for 3-body decays
MC
p* (MeV/c) p* (MeV/c)
2/ndf = 1.08 2/ndf = 0.96
fit lower edge 180 MeV
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 17
b) using Fermi-Dirac shape for 3-body decays
MC
p* (MeV/c)p* (MeV/c)
MC
and populations agree within errors Work in progress
fit lower edge 180 MeV
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 18
Analysis of ratio BR(K 0)/BR(K )M. Martemianov V. Kulikov
cosK.KselKfit.Ktrg
window.exp
K
0K
K
0KR
Ktrigger - trigger efficiency,
extracted from EXP. data
Kfit - efficiency of signals and
background rejection, based on MC
data and performed of EXP data,
Ksel - selection efficiency,
from MC and EXP. data
Kvetocos - efficiency of
cosmic veto rejection, EXP. data
- hyphotesis for secondary particles
Selected - window : 190 - 220 MeV/c
Selected - window : 220 - 260 MeV/c
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0.00220.00030.3346ν)μBR(K
)ππBR(K (syst.)(stat.)0
2(syst.)(stat.) 10)65.00.09(133.46
Both triggers employed
New checks on Ktrg and Kcos
Result is in good agreement with world data
Statistical error negligible due to the huge sample of kaon decays (more than 6.5 M; 2002 Data).
Systematic error ( 0.65 %) dominates.
Result can be updated by further investigation of MC/EXP uncertanties
Include calculation of K decay
Analysis of ratio BR(K 0)/BR(K )
B.Sciascia KLOE General Meeting - Roma - November, 14th 2003 20
Br(K ): measurement on a good shape Br(K ): ongoing work Br(K )/Br(K ): memo in
preparation
New MC (see M. Moulson presentation): - Small sample - HW+Tracking efficiencies (by S.Dell’agnello, ready) - on EMC (by C.Bloise, M.Testa, and T.Spadaro, ongoing work) Improve correlation study
Conclusions
Tags in a good shape for absolute BR measurements
Efficiencies: a lot of work . . .
Selection effects: - FilFo - Trk 1/Trk 2; EvCl 1/EvCl 2
Different techniques have been implemented Systematics: to be finalized. . .