1

Charm Semileptonic Decay

• The importance of charm SL decay• Pseudoscalar l decay• Vector l decay

– Analysis of DK*– The V/PS enigma: (D+K* / K– The Dsform factor enigma

• The future of SL decay– Cleo-c / Bes III (3770) running

Jim Wiss Univ of IllinoisHQL2004June 2 , 2004

Apologies for all the important and fascinating results that I had to skip

Featuring results from

2

Charm semileptonic decay as tests of LQCD

Apart from form factors, these decays can be computed using perturbation theory and are first order in CKM elements

The form factors incorporate hadronic complications and can be calculated via non-perturbative Lattice QCD.

(*)KD

c W l

q

scsV

Charm SL decays provide a high quality lattice calibration crucial to reducing future systematic error in the Unitarity Triangle. The same techniques validated in charm can be applied to beauty.

3

Pseudoscalar l decays

22 3

2 3

22 2

2(

4( ) )

F cq P

lf q O mG V Pd D P

dq

Provides a way to either measure CKM elements or to verify f+(q2) calculations

...But a major disconnect exists between experiment and theory. Theory works best where experiment works worse.

0 0.5 1 1.5 2 2.5 3

3P

2q

cleanest theory

highest rate

D l

2 2pole

1f

q m

2expf q ISGW

Two forms are used to parameterize f+(q2)

pole

These should be among the first unquenched lattice calculations... is easiest for LQCD

c

q

2max

2 qq s

q

l

lattice daughtera Kaon at rest in D frame

4

Comparing pole versus ISGW form in De

De should provide a powerful test of future lattice predictions

dp

dLattice

hep-ph/0101023

better sys as P0

Unfortunately present LGT offers very little discrimination between the two common forms

dp

d

P (GeV)

2q

22f q

...where differences are dramatic.e decay gets quite

close to the D* pole...

2 2 ( )q GeV

But past esignals have severe backgrounds and poor q2 resolution. Thus requiring parameterizations.

The lattice can now calculate f+ as a function of q2.

5

De/Ke

(0)0.86 0.07 0.05

(00.01

)K

f

f

Consistent w/ SU(3) breaking

32

2

2

2

2

324( )

F cq P

d D P

dq

G Pf

Vq

•Look for D*D decays. The “signal” is in the m plot.

•3 bins in q2 to get form factor info.

•Include peaking and non peaking backgrounds

0.082 .006 0.005 CLEOe

Ke

A big advance in precision!

Kl l

6

q2 information in De/Ke

MK

3

E691

Cleo

91

Cleo

93

E687 tag

E687 in

c

Cleo

04

1.4

1.6

1.8

2.0

2.2

2.4

2.6

Ke

nu

po

le m

as

s

The Cleo 04 epole mass is

After correcting for smearing Cleo reports these corrected q2 fractions

e

Ke

Clearly the data does not favor the simple Ds* pole

1.90 0.05

Disfavors ISGW2 form by ~4.2

7

Dvector decays

H0(q2), H+(q2), H-(q2) are helicity-basis form factors computable by LQCD...

A

22

22 2 2

20

0

sin sin(1 cos )sin

sin sin1( ) (1 cos )sin

8 2cos cos2sin cos

2cos

il Vi

l V il Vi

l l Vl V

l VV t

e He H

e Hmq m e H

q HH

H

c

c

cmc

q qq q

q qq q

q qq q

q

+

+ ---

-

ì üï ïï ïï ï+ï ïï ï+ï ïï ï= - - - +í ýï ï+ï ïï ï-ï ïï ï+ï ïï ïî þ

right-handed + left-handed +Two amplitude sums over W polarization using D-matrices

22 2

(0)( )

1i

iA

AA q

q M

22 2

(0)( )

1 V

VV q

q M

Helicity FF are combinations of the vector and two axial form factors

v 1(0) (0)r V A

2 2 1(0) (0)r A A

Two numbers parameterize the decay

8

Interference in D+ K*

Yield 31,254

DataMC

K* interferes with S- wave K and creates a forward-backward asymmetry in the K* decay angle with a mass variation due to the varying BW phase

(2002)

F-B

asy

mm

etry

(m K

The S-wave amplitude is about 7% of the (H0) K* BW with a 45o relative phase

Focus “K*” signal

The same relative phase as LASS

matches model

-15% F-B asymmetry!

9

K*form factors

1 cos 0.5V

0.5 cos 1V

0.5 cos 0.5V

acoplanarity

Results are getting very precise and unquenched calculations for incisive tests of the theory would be very desirable.

Incisive tests of the model are possible

Due to interference

10

Further tests of the K*model

Vcos

cos

Vcos

cos

Generally the model tracks the data rather well…

cos

A dramatic mismatch is seen at very low q2

suggesting a V(q20) problem

Focus even has a preliminary analysis of the K*0 line shape. K*0)is less than PDG by~1.6 MeV w/ errors

11

The vector/pseudo scalar enigma

K*l

/

K

E691

E653

Focus

Argus

Omega

Cleo 1

Cleo 2

Cleo 2

E687

0.3

0.4

0.5

0.6

0.7

0.8

0.9

muons electrons

0.620.02

*

0

Quark models predicted a

1

But V/PS 1/2 in data

oD KV

PS D K

The 2002 CLEO result tended to resolve this discrepancy by reporting a larger K*l/K2 BR

circa 1993Form factor ratios were well predicted but the scales were not.

The 2002 FOCUS result tended to reinstated it by getting a value close to previous K*l/K2 world average.

Direct (D+K* / K

*0

00.594 0.043 0.033

D K

D K

Use upstream Ks (~10%) so that both the numerator (K) and denominator (Ks ) leave 3 tracks in FOCUS -strip

0

0( ) ( ) (11 11) /K K

D D ns

0

0( ) ( ) ( 25 9.7) /K e K e

D D ns

sK

0CLEO(02) partially reflects a inconsistency in ( )D K e

0using (D K

*0 0D K l K l Theory

S-wave corrected

13

Ds form factor enigma

Theoretically the Dslform factor should be within 10% of D+ K*l The rV values were consistent but r2 for Dslwas 2 higher than D+ K*l

E7

91

CL

EO

E6

53

E6

87

BK

S

LM

MS

ISG

W2

0

0.5

1

1.5

2

2.5

3R

V

0

0.5

1

1.5

2

2.5

3

R2

circa 1999

ISG

W2

Fo

cus

E79

1

CL

EO

E65

3

E68

7 BK

S

LM

MS

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 1 2 3 4 5 6 7 8 9

RV

But the (2004) FOCUS measurement has consistent r2 values as well!

Ds versus D+ K*l

14

Other results on Ds

NO evidence for s-wave interference in Ds (<4%) of (H0 ) BW

Vcos cos

2qacoplanarity

Angular projections look finefo

cu

s

cle

o2

cle

o

arg

us

e687

0.2

0.4

0.6

0.8

0.540 0.040

BR relative to are consistent

A highly cut sample is required to remove backgrounds

15

The future of charm SL physics

“yellow book”1 fb-1MC

U = Emiss - Pmiss

Closing the neutrino in D e events

Cleo-c and Bes III: Run at (3770) with high luminosity and a modern detector

DoDo, DoK-+

K-

K+

+

Extremely clean events!

U = Emiss - Pmiss

prelimin data (60 pb-1)

Pavlunin

APS Talk

dp

d

P (GeV/c)

dp

d

P (GeV/c)

yellow book1 fb-1 (MC)

The q2 impasse afflicting SL data for the last 20 years should finally be overcome

16

Summary

Consistent FF for D+ K* & Ds

+

(m K

s-wave interferencein D+ K*

F-B

asy

mm

etry

V(q20) problem D+ K*

q2< 0.2

cos

New CLEO De/Keresult

0.082 .006 0.005 e

Ke

*( )sm D

(0)0.86 0.07 0.05

(0)K

f

f

*0

0

)

)

D K

D K

V/PS

ratio

17

dp

d

D e

1 fb-1 (MC)

U = Emiss - Pmiss

prelim dataSL Physics of the future

Promises of a rosy future with precision neutrino closure