Recent CLEO Charm Meson and Baryon Results

Jim Napolitano (RPI & Cornell)

We will discuss the following results:

1) First Observation of D0 → K0Sηπ

0

Branching Ratio and Dalitz Plot Structure

2) Form factors in D0 → {π−,K−}e+νFirst measurement of D0 → π−e+νe Form Factor

3) Measurement of Ξ0c → pK−K−π+

Color-Suppressed Diagrams in Ξ0c Decay

2004 Phenomenology SymposiumUniversity of Wisconsin, Madison

26-28 April, 2004

1

CLEO Integrated Luminosities

CLEO III

CLEO II.V

CLEO II

CLEO I.V

CLEO I

CLEO Physics

CESR Upgrades

1980 1985 1990 1995 2000 2005

109

108

107

106

105

104

BB

/ Ye

ar

b c

(BB Mixing)b u

KK/

NewTracking

CsI

2cm BPSilicon

3.5cm BP

He-propane

Microbeta7 Bunches

1 IR

Crossing Angle9X3 Bunches

2230902-007

CLEO Upgrades

9x4 Bunches

9x5 Bunches

B Decay

Ds

(4S), (5S)

b sB K*

BACP Limits

DD Mixing

SC IR QuadsSC RF

Limit

I

IBBB

I

RICH(1D)

Pretzel Orbits

NewTracking

2

1) First Observation of D0 → K0Sηπ

0

CLEO-II.V analysis to be submitted to Phys.Rev.Lett.

Little is known about D0 decays including η:

PDG 2002: B(D0 → ηX) < 13% @90% CL

K0Sηπ

0 is a CP = +1 eigenstate with potential resonantsubstructures. For example:

• D0 → K̄?0(892)η

• D0 → K0Sa

00(980)

• Others?

Underlying scalar mesons in D decay are still controversial

a0(980), f0(980), “σ”, “κ”, . . .

3

Selection of D0 from D?+ → π+

slowD0

Example: D0 → K0Sπ

0 (“Calibration” mode)

⇒ Use Q ≡ M(π+slowKSπ

0) −M(KSπ0) −mπ

0

200

400

600

0 0.005 0.01 0.015 0.02

Events in hist.=3165Func: GG(comm.center) + Frac.Pol.GG Area= 2930.7± 149.2ev.Center= 0.005828± 0.000011R.M.S.= 0.000708± 0.000077Frac.1= 78.55± 3.60%

Frac.2= 21.45± 5.19%

s1= 0.000443± 0.000016s2= 0.001272± 0.000126

Q , GeV/c2

Even

ts

0

100

200

0 0.005 0.01 0.015 0.02Q , GeV/c2

Even

ts

0

0.01

0.02

0.03

0.04

0 2 4 6P(D*+) , GeV/c

Prob

abili

ty /

bin

Continuum

BB-bar

0

100

200

300

-0.1 0 0.1

Entries 3113

m(KSp0)-m(D0) , GeV/c2

Even

ts

MC statistics:Tot:3085S+B:2912S :2838B :74Qsb:2929.15

0

50

100

-0.1 0 0.1

Entries 1500

m(KSp0)-m(D0) , GeV/c2

Even

ts

Data statistics:Tot:1410S+B:1220S :1111B :109Qsb:1161.53

0

100

200

300

-0.1 0 0.1

Fit to MCFit to MC

Function: Gauss + LineEvents in hist.=3085

G Area=2800.8± 85.4 event

Mean=-2.314± 0.380 MeV/c2

s=18.431± 0.330 MeV/c2

m(KSp0)-m(D0) , GeV/c2

Even

ts

0

50

100

-0.1 0 0.1

Fit to DataFit to Data

m(KSp0)-m(D0) , GeV/c2

Even

ts

0

100

200

300

-0.1 0 0.1

Fit to MCFit to MC

Events in hist.=3085Func: GG + P1GG Area= 2876.7± 208.0eventCenter= 0.000771± 0.000000R.M.S.= 0.019268± 0.001577Frac.1= 65.72± 5.11%

Frac.2= 34.28± 7.53%

s1= 0.014023± 0.000692s2= 0.026571± 0.001346Mean1= 0.001173± 0.000648Mean2= -0.012288± 0.002426

m(KSp0)-m(D0) , GeV/c2

Even

ts

0

50

100

-0.1 0 0.1

Fit to DataFit to Data

Events in hist.=1410Func: GG + P1GG Area= 1107.3± 78.1eventCenter= 0.002174± 0.000000R.M.S.= 0.017461± 0.001868Frac.1= 46.48± 4.98%

Frac.2= 53.52± 9.18%

s1= 0.014417± 0.001082s2= 0.019727± 0.002443Mean1= 0.004677± 0.002705Mean2= -0.011245± 0.002692

m(KSp0)-m(D0) , GeV/c2

Even

ts

4

Observation of D0 → K0Sηπ

0

B(D0 → K0Sηπ

0)

B(D0 → K0Sπ

0)= 0.46 ± 0.07 ± 0.06

⇒ B(D0 → K̄0ηπ0) = (1.05 ± 0.16 ± 0.14 ± 0.10)%

5

Dalitz Plot for D0 → K0Sηπ

0

Tighter cuts than for branching ratio measurement

Substructure isdominated byK?(892) and a0(980)

Interference!• Deficit in center• a0(980) asymmetry• Shift(?) in K?(892)

6

Fit Dalitz Plot for AmplitudesUnbinned maximum likelihood fit to Breit-Wigner shapes

FF(D0 → K?(892)η) = 0.293 ± 0.062 ± 0.029 ± 0.019

FF(D0 → a0(980)KS) = 1.19 ± 0.09 ± 0.20 ± 0.16

FF(D0 → Other) = 0.246 ± 0.092 ± 0.025 ± 0.087

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2) Form Factors in D0 → {π−,K−}e+ν

New CLEO-III analysis to be published soon.

For qµ ≡ pµ(W+) havedΓ

dq2=

G2

24π3

∣∣∣∣∣Vcq∣∣∣∣∣2 p3

∣∣∣∣∣∣F(q2)∣∣∣∣∣∣2

Note: First measurement of D → πeν form factor shape!

Plus: New result for B(D0 → πeν)/B(D0 → Keν)

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Signal and Background in CLEO-III

Reconstruct D0 using pν = pmissing and subject to the

constraint that M({K−, π−}e+ν) = M(D0).

Use ∆M ≡ M(πslowD) −M(D)

D0 → K−e+ν

0.12 0.17 0.22 0.27 0.320

500

1000

1500

∆M (GeV/c2)

D0 → π−e+ν

0.12 0.17 0.22 0.27 0.320

100

200

300

400

∆M (GeV/c2)

⇒ The challenge for D → πeν is significant!

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D0 → π−e+νe Normalized q2 Distribution

Preliminary! Paper will be submitted shortly.

Form factor models

1ΓdΓdq2

×Effic.

Binned data points

LOW MID HIGH0.00

0.10

0.20

0.30

0.40

0.50

0.60

q2 (GeV2/c2)

Results are consistent with form factor models, but notquite enough sensitivity to distinguish them.

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Relative Semileptonic Branching Ratio

Preliminary! Paper will be submitted shortly.

We findB(D0 → πeν)

B(D0 → Keν)= 0.097 ± 0.010 ± 0.010

0 0.05 0.1 0.15 0.20

1

2

3

4

5

This Work

E687 (1996)

CLEO (1995)

CLEO (1993)

Mark!III (1989)

B(πeν)/B(Keν)

Systematic error dominatedby three sources:

1) Neutrino reconstructionsimulation (∼ 3%)

2) Misidentification of kaonsas pions (∼ 4%)

3) Uncertainty in backgroundbranching fractions (∼ 4%)

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Solenoid Coil Barrel Calorimeter

Drift ChamberInner Drift Chamber /

Beampipe

EndcapCalorimeter

IronPolepiece

Barrel MuonChambers

MagnetIron

Rare EarthQuadrupole

SC Quadrupoles

SC QuadrupolePylon

2230104-002

CLEO-c

Ring Imaging CherenkovDetector

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CLEO-c event: e+e− → ψ′′(3770) → D0D̄0

D0 → K−e+νe D̄0 → K+π−

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3) Measurement of Ξ0c → pK−K−π+

I. Danko et al., Phys. Rev. D 69, 052004 (2004)

Physics: The decay Ξ0c → pK−K̄?(892)0 cannot proceed

through external W decay, so it is “color suppressed”.⇒ Want to separate it from nonresonant four-body decays.

Measured Ξ0c → pK−K−π+ rate relative to Ξ0

c → Ξ−π+

Needs extensive p,K, π particle identification madepossible by RICH in CLEO-III

Only previous result: ACCMOR 1990 (four events, all K̄?)

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Final State Particles and Weak Decay Diagrams

External W+

cds

sds

ud

Ξc0 Ξ−

π+

cds

s

ds

u

d

Ξc0 p

K-

K0(∗)

. . . or sds → K−pK−, etc

Internal W+

cds

sds

ud

Ξc0 Ξ−

π+

cds

s

ds

u

d

Ξc0 p

K-

K0(∗)

⇒ Absence of a π+ (or K+) implies that the decayproceeds through an internal W+ line, and these shouldbe color-suppressed.

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Results: Ξ0c Decay

Ξ0c Decay modes

150

100

50

02.30 2.40 2.50 2.60

Entr

ies / 6

(M

eV

/c2)

M(pK K +) (GeV/c2)

II

0990803-002

pK−K−π+

2.30 2.40 2.50 2.60

Entr

ies / 6

(M

eV

/c2)

M( +) (GeV/c2)

I

0

25

50

75

1000991203-003

Ξ−π+

K−π+

mass:

B(Ξ0c → pK−K−π+)/

B(Ξ0c → Ξ−π+) = 0.35±0.06±0.03

B(Ξ0c → pK−K−π+; No K̄?)/

B(Ξ0c → Ξ−π+) = 0.21±0.04±0.02

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Summary

• CLEO still produces results from high energy data sets

Several publications are on the way.See also Vladimir Savinov, this conference.

• Some first observations are presented here

· D0 → K0Sηπ

0 including D0 → K0Sa0(980)

· Form factor shape for D0 → π−eν

· Ξ0c → pK−K−π+; No K̄?

• Stay tuned for new charm results from CLEO-c

See also Alex Smith, this conference.

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