Determining the Coherence Factor, R, of D ® K3 p Decays. Motivation Reminder B ® DK: Access to CKM g Use of DCS D 0 Decays: ‘ADS’ Approach Coherence Factor, R . Status with Preliminary Measurements Reconstruction Efficiencies Background Estimations (Data and MC)
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Determining the Coherence Factor, R, of D ®K3pDecays
Andrew Powell (University of Oxford)
On behalf of the UK group
D-Hadronic PTA, CLEO-c Collaboration Meeting, July 9th 2007
gfromB±®DK ±
ColourSuppressed
Common starting point for a variety of methods to extractg
‘ADS’ Strategy: D ® hh
Large interference possible if amplitudes of similar magnitude
f(D) = non-CP Eigenstate(e.g. K+p-)
DCS Decay
CF Decay
Interference is now large when
looking at ‘wrong sign’ decays: (2) & (4)
(1)
(2)
(3)
(4)
These + other rates (e.g. D®KK, pp) allow unknowns to be fitted.
‘ADS’ Strategy: D ® Multi-Body
where we introduce the additional parameters rDK3p and dDK3p
[ Atwood & Soni, Phys Rev D 68 (2003) 033003 ]
MeasuringRK3p
Opposite Sign Kaon
CP even
CP odd
Same Sign Kaon
Why These Tags?
4) :
Therefore, can get separate measurements of
and
Preliminary K3p vs Tags
Selection Results
MC Reconstruction Efficiencies
(MBC(K3p), MBC(Tag)) = (1.86 : 1.87, 1.86 : 1.87)
eRec (%)
MC
Assoc.
MC
Events
|DE|
Cut (GeV)
Tag
Reco
Events
5,000
0.0177
1,427
KK
1,379
24.3
pp
0.024
764
739
2,000
32.6
Ksp0
13.8
2,650
2,456
0.048
15,000
Kppp
22.3
0.015
22,324
25,260
100,000
Non-Peaking Background In Data
As shown last time, Jim Libby has run a selection for these 5 modes over the 281pb-1 data set. Applying the same techniques as quoted in Alexander Scott’s CBX note, Jim has estimated the non-peaking, combinatoric, background from analysing the Mbc sidebands.
K3π vs K3π(Opp. Sign)
A
S
C
D
B
D
K3π vs K0S π0
K3π vs K3π (likesign)
The Other Modes …
K3π vs π+π−
K3π vs K+K−
Counting Signal + Non-Peaking Bkg
Assessing the events found for each mode within these defined sideband regions results in the following signal and estimated background numbers:
Avoids double counting
of combinatoric background
In order to determine sources of peaking background, we have looked at the generic DDbar MC…
MC Background Studies
Observed ratios
(I : II : III) = (10 : 4 : 1)
RK3p cos(z ) :Sensitivity
Predictions
With Current Data Set
& Implementation
sstat= 0.36
Above plot generated using an “Illustrative” value: RK3p cos(z ) = -0.5
With Final Data Set
& Additional Tags
sstat~ 0.15
Above plot generated using an “Illustrative” value: RK3p cos(z ) = -0.5
‘Non-Global’ Determination of RK3p cos(z )
Summary