Study of DK/ π e + and measurement of |V cs | and |V cd | at CLEO-c
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Transcript of Study of DK/ π e + and measurement of |V cs | and |V cd | at CLEO-c
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 1 4/15/2008
Study of Study of DK/πe+ and measurement of and measurement of |V|Vcscs| and |V| and |Vcdcd| at CLEO-c| at CLEO-c
Introduction Reconstruction techniques Results: branching fractions,
form factors, |Vcs| and |Vcd| Summary
Bo Xin
Purdue University
CLEO collaboration
APS April Meeting, Apr 12 - 15, 2008
K-
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K+
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 2 4/15/2008
• Semileptonic decays are an excellent laboratory to study
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IntroductionIntroduction
Weak PhysicsQCD Physics
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eDeDeKDeKD
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• Gold-plated modes are P P semileptonic transitions as they are the simplest modes for both theory and experiment:– Cabibbo favored :– Cabibbo suppressed :
Assuming theoretical calculations of form factors, we can extract |Vcs| and |Vcd|
Since |Vcs| and |Vcd| are tightly constrained by unitarity, we can check theoretical calculations of the form factors
Tested theory can then be applied to B semileptonic decays to extract |Vub|.
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 3 4/15/2008
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
DD
CLEO has world’s largest data set at 3.770 GeV
Today’s results (281/pb)
30X MARK III
15X BES II
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 4 4/15/2008
Analysis Technique (tagged)Analysis Technique (tagged) 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:
For semileptonic D : The absolute branching fraction is
Tagging creates a single D beam of known 4-momentum
0
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(3770)
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D
D
D
D K eK
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beamD EEE
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from fits to U
from fits to Mbc
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 5 4/15/2008
Pure DD,zero additional
particles, ~5-6 charged
particles per event
~3.1x 105 D0 and~1.6 x 105 D+ tagsreconstructed from
~1.8 x 106 DD events
We tag ~25% of the events,
compared to ~0.1% of B’s at the
Y(4S)
D D tagging at CLEO-c (281/pb of Data)tagging at CLEO-c (281/pb of Data)
World’s largest data set at 3.770 GeV
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42 /cp/cEM Dbeambc
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 6 4/15/2008
Reconstruction of Semileptonic Decays (tagged)Reconstruction of Semileptonic Decays (tagged)
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pEU
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Belle luminosity = 282/fb = 1000xCLEO-c
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Extract yields from U distributions and measure branching fractions with multiple tag modes separately and combined
Study form factors and CKM matrix elements using efficiency-corrected decay rate distributions
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PRELIMINARY
S/N π - lν K - lν
CLEO-c ~40/1 ~300/1
Belle ~ 4/1 ~ 20/1
Signal events π - lν K - lν
CLEO-c ~700 ~6800
Belle ~220 ~2700
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 7 4/15/2008
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Neutrino Reconstruction (Untagged)Neutrino Reconstruction (Untagged)
Larger signal yields, also larger backgrounds
Hermeticity and excellent resolution of the CLEO-c detector,
hence excellent understanding of the background
Simultaneously fit Mbc distributions of the 4 signal modes in 5 q2 bins to extract d(BF)/dq2 and integrate to get branching fractions.
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 8 4/15/2008
DK/πe+ Branching Fractions
Precision measurements from BABAR/Belle/CLEO-c. CLEO-c most precise. Theoretical precision lags experiment.
0 2B( ) 10
3.58(5)(5) (tag) (prelim.
3.56(3)(9) (not g
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a )
D K e 0 3B( ) 10
0.31(1)(1) (tag) (prelim.
0.30(1)(1) (no
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tag)
D e ( ( )) / ( ) ~ 2%
( ( )) / ( ) ~ 4.5%
B Ke B Ke
B e B e
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 9 4/15/2008
Absolute dAbsolute dΓΓ/dq/dq2 2 DistributionsDistributions
Modified Pole (BK) Model
Simple Pole Model
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poleMq
fqf
k
kk qza
qqPqf )0,(
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Hill Series
parameterization
Fit to Simple Pole Model Shown
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PVG
dq
eKDd KcdcsF
0D K e
0( 2)D e 0D e
0D K e
PRELIMINARY
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 10 4/15/2008
DD00 K K --ee++ Form factors: test of LQCD
1/ 2
32( )2( ) ( )
( ( ) )~ /i
K ii
cs cd
D K ef q P
qV
)0( :ionNormalizat Kf
Assuming Vcs=0.9745CKM Unitarity
Shape: CLEO-c prefers smaller value for αNormalization: experiments (2%) consistent with LQCD (10%). Theoretical precision lags.
2
2 2 2 2
(0)( )
1 1pole pole
f qq m
f
q m
Modified pole model used as example
Shape: ( )Ke
FNAL-MILC-HPQCD (Curve courtesy Andreas Kronfeld)
2
cs2 33 2 22( ) V
24F
KPGd
f qdq
)( , *spole DMMwith
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 11 4/15/2008
DD00 --ee++ Form factors: test of LQCD
1/ 2
32( )2( ) ( )
( ( ) )~ /i
K ii
cs cd
D K ef q P
qV
)0( :ionNormalizat f
AssumingVcd = 0.22380.0029 (CKM Unitarity)
shape: ( )e
Modified pole model used as example
2
2 2 2 2
(0)( )
1 1pole pole
f qq m
f
q m
FNAL-MILC-HPQCD
Shape: experiments compatible with LQCDNormalization: experiments (4%) consistent with LQCD (10%). CLEO-c is most precise. Theoretical precision lags.
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F PGd
f qdq
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Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 12 4/15/2008
Vcs and Vcd Results
13.094.0 32.026.0
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 ± 0.0240.230 ± 0.011
(interactions)D e (untagged) 0.217 ± 0.009 ± 0.004 ± 0.023
D Ke(tagged) 1.014 ± 0.013 ± 0.009 ± 0.106 1.04 ± 0.16 (excl. sl. width excluding CLEO/BES)
taggedD Ke(untagged) 1.015 ± 0.010 ± 0.011 ± 0.106
Expt. uncertainties Vcs <2% Vcd~4% Theory 10%
CLEO-c: Best determination of |Vcs|, and |Vcd| in good agreement with PDG
scW , 13.094.0 32.0
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PRELIMINARY
PRELIMINARY
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Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 13 4/15/2008
SummarySummary
Most precise B(D K e+) and B(D e+).
Most precise measurements of f+(0) and shape for D e+ .
Best direct measurement of |Vcs|.
Most precise determination of |Vcd| from semileptonic decays.
Statistical uncertainties will be reduced
by a factor of
Most systematic uncertainties are being reevaluated.
Some are expected to be reduced.
More stringent tests of theory -- f+(0) and shape for D K/ e+ .
Reduced uncertainties on |Vcs| and |Vcd|.
What we have achieved (281/pb)
What we are going to achieve (818/pb)
We are eagerly awaiting
more precise LQCD calculations of semileptonic form factors.
3~
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 14 4/15/2008
Backup slidesBackup slides
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missmiss
eKtagmiss
eKbeammiss
pEU
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pEq
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ppq
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ppppEp
Isospin Invariance: (from tagged analysis)
Systematics missing….
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 15 4/15/2008
Reconstruction of Semileptonic Decays (tagged)Reconstruction of Semileptonic Decays (tagged)S/N ~ 40/1, Compared to Belle 282/fb = 1000xCLEO-c~220 signal events, S/N ~ 4/1
S/N ~ 300/1, Compared to Belle 282/fb = 1000xCLEO-c~2700 signal events, S/N ~ 20/1
Extract yields from U distributions and measure branching fractions with multiple tag modes separately and combined
Study form factors and CKM matrix elements using efficiency-corrected decay rate distributions
29520
69928
291055
679684
PRELIMINARY|| missmiss pEU
•A Belle plot here?
for comparision
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 16 4/15/2008
qq22 resolutions and Raw q resolutions and Raw q22 distributions distributions
2q
d
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D0→K-e+ν
2q
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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
background in blue
~7000 eventsS/B > 300/1
D0→π-e+ν
D0→K-e+ν
Excellent q2 resolution and S/B ratio
To find the absolute decay rate, need to subtract background and apply efficiency corrections.
background in blue
PRELIMINARY
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 17 4/15/2008
Form factors as a stringent test of LQCD
Removing the kinematic termsreveals the form factor
1/ 2
32( )2( ) ( )
( ( ) )~ /i
K ii
cs cd
D K ef q P
qV
Assuming Vcs = 0.97450.0008 (CKM unitarity)
FNAL-MILC-HPQCD
(Curve courtesy Andreas Kronfeld)
Modified Pole (BK) Model
shown
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 18 4/15/2008
Simple Pole ModelSimple Pole Model
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poleMq
fqf
D → K e+
ν
CLEO-c has 1st measurements of Mpole for D+
Important consistency check!
My average
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 19 4/15/2008
Modified Pole (BK) ModelModified Pole (BK) Model
D → π e+
ν
0.32(5)
BK parameterization α~1.75
CLEO-c values > 10σ away
Physical basis of BK model not supported
Compatible
Consistent
For D → K e+ ν, CLEO-c α values > 27σ away from BK physical value, LQCD precision (10%) lags experiments (2%) !
LQCD precision(10%) lags experiments (4%)
My average
0.634(18)(9)(8)
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 20 4/15/2008
Becher-Hill series parameterizationBecher-Hill series parameterization
k
kk qza
qqPqf )0,(
0,
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2
•Both linear “series(2)” and quadratic “series(3)” parameterization describes data well•Quadratic term a2 not well-determined with current statistics•As data does not support physical basis for the pole & modified pole models, the model independent Becher-Hill series parameterization is used for |Vcx|.
Dashed lines show 1σ region
Bo XinDK/π e+ and |Vcs| and |Vcd| at CLEO-c 21 4/15/2008
Projections with 818/pb dataProjections with 818/pb data
281/pb 818/pb 281/pb 818/pbNOT CLEO-c official
Statistical uncertainties will be reduced by a factor of Most systematic uncertainties are being reevaluated.
some are expected to be reduced.
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