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. K -. K +. -. e +. Absolute Branching Fractions and Form Factor Measurements in DK/ π e + . Introduction Branching Fractions Form Factors Summary. Bo Xin Purdue University CLEO collaboration. APS April Meeting, Apr 14-Apr 17, 2007. *. *. Introduction. - PowerPoint PPT Presentation
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Bo XinDK/π e+ BF and FF 1 4/14/2007
Absolute Branching Fractions and Form Factor Absolute Branching Fractions and Form Factor Measurements in Measurements in DK/πe+
Introduction Branching Fractions Form Factors Summary
Bo Xin
Purdue University
CLEO collaboration
APS April Meeting, Apr 14-Apr 17, 2007
K-
-
e+
K+
Bo XinDK/π e+ BF and FF 2 4/14/2007
• Semileptonic decays are an excellent laboratory to study
• Gold-plated modes are P P semileptonic transitions as they are the simplest modes for both theory and experiment:
– Cabibbo favored :– Cabibbo suppressed :
• Main goals of the analyses:– Measure efficiency-corrected absolutely-normalized decay rate distributions and form
factors – Measure form factor parameters to test LQCD and model predictions
• We analyze both D0 and D+ decays. By isospin invariance
– . – .
This is a nice cross check and adds statistics to improve statistical precision.
)(,)(24
))(( 22223
3)(
2
)(2
2
eMqwhereqfPVG
dq
eKDd KcdcsF
IntroductionIntroduction
eDeDeKDeKD
00
00
,,
eDeD
eKDeKD00
00
2
Weak PhysicsQCD Physics
* *
Bo XinDK/π e+ BF and FF 3 4/14/2007
The CLEO-c detector and data sampleThe CLEO-c detector and data sample
SVX
CLEO III
p/p = 0.6% at 800 MeV/cp/p = 0.6% at 800 MeV/c
E/E = 2% at 1 GeV, E/E = 2% at 1 GeV,
5% at 100 MeV5% at 100 MeV93% coverage (charged and neutral)93% coverage (charged and neutral)
Excellent electron and particle IDExcellent electron and particle ID
CLEO-c
• Advantages at (3770)– Pure , no additional
particles – Low multiplicity– High tagging efficiency
• The generic MC sample (40X luminosity of the data).
DD
Today’s analyses (281/pb)
30X MARK III
15X BES II
Bo XinDK/π e+ BF and FF 4 4/14/2007
Tagged Reconstruction of Semileptonic DecaysTagged Reconstruction of Semileptonic Decays Candidate events are selected by reconstructing
a D, called a tag, in several hadronic modes
Then we reconstruct the semileptonic
decay in the system recoiling from the tag.
Two key variables in the reconstruction
of a tag:
Define The absolute branching fraction is
Tagging creates a single D beam of known 4-momentum
0
0
0
0
(3770)
,
D
D
D
D K eK
22
42 /cp/cEM Dbeambc
beamD EEE
|| missmiss PEU
Bo XinDK/π e+ BF and FF 5 4/14/2007
~30% event tagging efficiency
~20% event tagging efficiency
Examples of Mbc for tag modes in the data
)281(/163~
:1
pbK
tagsDAll
)281(/308~
:1
0
pbK
tagsDAll
eventsK
KD
51~
0
eventsK
KD
98~
00
eventsK
KD
23~
000 eventsK
KD
80~
eventsK
KD
24~
0
eventsK
KD
16~
0
One D tag candidate per D tag flavor per mode is chosen.
D0D0 and and D+D+ tag yields in 281/pb of Data tag yields in 281/pb of Data
Bo XinDK/π e+ BF and FF 6 4/14/2007
29520
69928
291055
679684
U = Emiss– |Pmiss| (GeV)
Fit to U distributionsFit to U distributions
eKD0
eD0
eD )( 00
eKKD )( 0*000
in fakes
KD
eK
eKKD )( 000*
eKD 0
eKKD )( 000*
Bo XinDK/π e+ BF and FF 7 4/14/2007
Neutrino Reconstruction (Untagged)Neutrino Reconstruction (Untagged)
The Reconstruction Algorithm:
Find an event with a signal electron and a signal K or π
Reconstruct the event missing (neutrino)
4-momentum
Calculate ΔE and scaled Mbc
is the scale factor for Pmiss that sets Δ E to zero.
( )
2 2( )( )
K e miss beam
bc beam K e miss
E E E E
M E
p
p p p
14397132134749
58468845029
Bo XinDK/π e+ BF and FF 8 4/14/2007
DK/πe+ Branching fractions
Isospin Invariance:
(From Tagged analysis)
Tagged/untagged consistent, 40% overlap DO NOT AVERAGE
Bo XinDK/π e+ BF and FF 9 4/14/2007
qq22 resolutions and Raw q resolutions and Raw q22 distributions distributions
2q
d
d
D0→K-e+ν
2q
d
d
D0→π-e+ν
700 eventsS/B ~40/1
CLEOIII(Y(4S)): q2 ~ 0.4 GeV2
CLEO-c((3770)): q2 ~ 0.012GeV2
q2 ~ 0.012GeV2
q2 ~ 0.011GeV2
Raw q2 distributionq2 resolution
Note the background in blue
7000 eventsS/B > 300/1
D0→π-e+ν
D0→K-e+ν
To find the absolute decay rate, need to subtract background and apply efficiency corrections.
Bo XinDK/π e+ BF and FF 10 4/14/2007
Fit to the Absolute Decay ratesFit to the Absolute Decay rates
D0→K-e+ν D+→Kse+ν
D0→π-e+ν D+→π0e+ν
Modified Pole (BK) Model
Simple Pole Model
22
2
/1
0
poleMq
fqf
k
kk qza
qqPqf )0,(
0,
1 222
2
Hill Series
parameterization
Tagged Modified Pole Model Shown
Bo XinDK/π e+ BF and FF 11 4/14/2007
Shape
Form factors as a stringent test of LQCDLQCD: C. Aubin et al.,
PRL 94 011601 (2005).
DATA FIT
LQCD
eD0
DATA FIT
LQCD
Vcd = 0.22380.0029Vcs = 0.97450.0008(CKM unitarity)
eKD0
+Normalization f (0)
CL
EO
pre
lim
inar
y
LQCD precision lags experiment.
Bo XinDK/π e+ BF and FF 12 4/14/2007
0.320.26
Uncertainty (%)
exp. thy. tot.
( ) 1.04 0.16 6 14.2 15.4
0.94 0.014 31
( ) 1.14 0.07 0.11 6.5 10.4 1
1.014 0.016 0.106 1.6 10.
2
4 10
.8
.5
cs
CL
V
PDG Ke
W cs
BESI
O c
I Ke
E
13.094.0 32.026.0
Vcs and Vcd Results (CLEO preliminary)
Tagged/ untagged consistent, 40% overlap DO NOT AVERAGE
Combine measured |Vcx|f+(0) values using Becher-Hill parameterization with (FNAL_MILC-HPQCD) for f+(0)
Decay Mode |Vcx| ± (stat) ± (syst) ± (theory) PDG
D e(tagged) 0.234 ± 0.010 ± 0.004 ± 0.024 0.230 ± 0.011
D e (untagged) 0.229 ± 0.007 ± 0.005 ± 0.024 (interactions)
D Ke(tagged) 1.014 ± 0.013 ± 0.009 ± 0.1061.04 ± 0.16 (excl. sl. Width
excluding CLEO/BES)
D Ke(untagged) 0.996 ± 0.008 ± 0.015 ± 0.104 Wcs
tagged
Expt. uncertainties Vcs <2% Vcd~4% Theory 10%
CLEO-c: Best determination of Vcs / Vcd in good agreement with PDG
13.094.0 32.026.0
Bo XinDK/π e+ BF and FF 13 4/14/2007
SummarySummary
We have presented preliminary results for D K/ e+ branching
fractions and form factors using the CLEO-c 281/pb data sample collected at the (3770).
These results obtained from the tagged and untagged analyses are consistent and are being combined (will be available soon).
Together, they represent the most precise charm semileptonic branching fraction measurements and form factors to date.
Using the unitarity of the CKM matrix we obtain the most precise values of f+(0) for D K/ e+ .
Using three flavor unquenched LQCD we have made the most precise determination of |Vcs| and |Vcd| is in good agreement with PDG.