Recent Charm Results From CLEO

• Searches for D0-D0 mixing

• D0 -> K0s+-

• D0->K*+l-• Conclusions

Alex SmithUniversity of Minnesota

1) Large |x| 2) |x| >> |y| 3) CP violation of any kind

D0 – D0 Mixing Analyses: Preliminaries

Use D0’s from D* decays to tag flavor of D0

D*+ D0+

Categorize D0 decays according to flavor of D0 and of K:

“Right sign (RS)”:

“Wrong sign (WS)”:

*0

00

0

KD

KD

KD

*0

00

0

KD

KD

KD

Cabibbo-favored (CF) decays

x, y, or doubly Cabibbo-suppressed decays (DCSD)

Complication: Strong phase s due to final state interactions:

SS

SS

xyy

yxx

sincos

sincos

x and y are what we really want

Current Status of D0-D0 MixingRecent Experiments:

CLEO, FOCUS, Belle, BaBar, E791Recent Predictions:

= x = y = non-SM

(|x|,

|y|,

etc.

)

(1/2|Am

plitude| 2)

Motivation to Study D0->Ks0+-

• Measure x and y rather than x’2 and y’

• RS and WS occupy the SAME Dalitz plot:

• First measurement of relative strong phase between D0 and D0 to to K0

s+- final state

• Only mode with sensitivity to sign of x!

• Doubly-Cabibbo-suppressed modes

• Comparable sensitivity to y as CP eigenstate (eg., D0->K+K-) analyses

• Better scaling of sensitivity to x with int. luminosity than D0->K+- analysis

• Low backgrounds ~1%!

• ~Flat efficiency in e+e- collisions

D0->Ks0+-: Dalitz Formalism

Visualize as pseudo-two-body

decay:

rBAABrABr

CDDr FPPqiMMM

PPF

22

*

0M

nr

nn

rr i

rr

i

rr

i

rr eAeAeA MMMM 2

22

1

11

Amplitude for each resonance given by a relativisticBreit-Wigner, with angular distribution determined by J. For J = 1 we have:

Total amplitude is the sum with a complex coefficient:

We consider 18 resonant and non-resonant decay modes:

resonant-non ,1430 ,

,1710 ,1500 ,1370 ,1270 ,980

,500 ,1700 ,1450 , , ,1780

,1680 ,1430 ,1430 ,1410 ,

0*

00020

0003

*20

**

KK

fffff

K

KKKKK

Con

trib

utio

ns to

the

Dal

itz

Plo

t

K*-

K0(

1430

)-K

2(14

30)-

K* (

1680

)-

0

f 0(98

0)

f 2(12

70)

f 0(13

70)

0(1

700)

/ 0

(145

0)

K*+

K0(

1430

)+

Dalitz Plot

Data

Fit Result

Component Amplitude Phase (0) Fit Fraction

K*(892)+

(770)0

(792)

K*(892)-

f0(980)

f2(1270)

f0(1370)

K0(1430)-

K2(1430)-

K*(1680)-

Non-res.

Results of Dalitz Plot Fit

054.0030.0

050.0016.0 029.0131.0

4

1158 11152

0.00200041.0

0.011227.0 005.0006.0 0.01 006.0055.0

38 4 7117

0.003013.0 05.007.0 0.04 05.068.1

35

32 2149

0.014672.0

0.005040.0

0.002006.0

0.0107.0

0.009080.0

0.002015.0

0.006023.0

0.016027.0

06.002.0

06.003.0 02.036.0

8.02.0

2.03.0 2.08.0

(fixed) 0(fixed) 0.1

199

13 5185

271321368

7.05.0

24.0010.0 14.056.1

0.4 1.02.2 1.02.0

0.4 1.09.0 3.00.0

8.22.4 0.9 8.06.5

4.19.0

6.04.0 6.09.1

2111

217 674

1022

65 511

1911 6847

1820 128173

169

167 1130

syst. modelingsyst. exp.stat.result

D0->Ks0+- Summary

• First observation (4.5) of WS D0->K0+-

• We observe 5 new submodes (10 total) of this decay

• First measurement of strong phase shift s between D0->K0+- and D0->K0+- = (-3 +/- 14)0

• Time-dependent analysis can measure sign of x (coming soon!)

• This is the best mode in which to search for mixing:

• y is likely to be comparable to or larger than x => must measure strong phase

D0->K*+e-• Reconstruct K*+ in Ks

0+, Ks0-> + - mode

• Advantages of this mode:• Only mixing contributes to WS signal

• Distinct proper time distribution of mixing: t2e-t

• K* mass cut rejects backgrounds

• Drawbacks of this mode:• Low momentum tracks due to e final state

• Soft e momentum due to forward neutrino favored by V – A coupling

• Must “pseudo-reconstruct” the undetected neutrino

• Only sensitive to x

D0->K*+e-: Fit to the “Right-sign” Data

candidates 51638

Distributions from Monte Carlo

D0->K*+e-: Fit to the “Wrong-signed” Data

candidates 99.100.0

Fit distributions from Monte Carlo

D0->K*+e-• Systematic uncertainties:

• Signal and background shapes• MC Statistics

• Resolution and background parameters

• Differences in RS and WS efficiencies

C.L. %95@ 0087.0

10(syst) 0.32(stat) 31.000.0

mix

2mix

R

R

2221

mix yxR

• Results to be combined with D0->K+l- analysis• Comparable sensitivity

Other CLEO Charm Analyses in Progress:

Summary• First observation (4.5 statistical

significance) of DCSD D0->K0+-

(prelim.)

• We observe 5 new submodes of this decay

• First measurement of strong phase shift s between D0->K0+- and D0->K0+- = (-3 +/- 14)0 (prelim.)

• First analysis that can measure sign of x (coming soon!)

• Best channel in which to search for mixing

C.L. %95@ 0087.0

10(syst) 0.32(stat) 31.000.0

mix

2mix

R

R

D0->K0+-:

D0->K*+l-:

• CP-even and CP-odd intermediate states provide sensitivity to 1 and 2, thus y

• Sensitivity to sign of x = M/ through sin term in |M|2

•

• Interference between Cabibbo-favored and DCSD may enhance sensitivity to x

D0->Ks0+-: Time Evolution of the Dalitz Plot

xofsign tosensitivex y tosensitivit

y y tosensitivit

2

y y tosensitivit

22sinsincoscos221 xtexteee ttttM

odd

002

even

001

CP

CP

DqDpD

DqDpD

22110

22110

2

1

where, 2

12

DteDteq

tD

eteDteDtep

tD ttiMi

ii

Mass eigenstates are also eigenstates of CP:

Time evolution is given by:

Evaluating <f | D1> and <f | D2>, collecting terms with similar time-dependence, and squaring the amplitude gives:

measured becan

and between phase strong Relative 0000s

KDKD