Absolute Branching Fractions and Form Factor Measurements in DK/ π e +

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+


• 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

* *


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


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


~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


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*


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


DK/πe+ Branching fractions

Isospin Invariance:

(From Tagged analysis)

Tagged/untagged consistent, 40% overlap DO NOT AVERAGE


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.


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


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.


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


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.

Absolute Branching Fractions and Form Factor Measurements in DK/ π e +

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