Zijin Guo

University of Hawaii(Representing BES Collaboration)

Quarkonium Working Group ’04, IHEP Beijing

October 13, 2004

Study of c Decays at BES

OUTLINE

• Introduction

• cJ pp,

• cJ h+h-KsKs

cJ K*(892)0K*(892)0

c0 f0(980)f0(980)

• c2 polarization

• Summary

INTRODUCTION

Charmonium System

• Exclusive quarkonium decays contribute an important laboratory for investigating QCD.

• Compared to J/ decays, relatively little is known concerning PC = ++ cJ decays.

• Color octet mechanism (COM) important for P-wave quarkonium decays.

A consistent set of theoretical predictions for the branching fractions, as well as more precise experimental measurements will lead to a better understanding of the COM and the nature of cJ states.

• Furthermore, the decays of cJ , in particular c0 and c2, provide a direct window on glueball dynamics in the 0+

+ and 2++ channels. C. Amsler and F. Close, PRD53 (1996) 295

World (2S) Samples (×106)

(2S)

0

2

4

6

8

10

12

14

MKI MKII MKIII CBAL BESI BESII CLEO

BESII Detector

Color octet mechanism (COM) important for P-wave quarkonium decays.

G. T. Bodwin et al., Phys Rev. Lett. D51, 1125 (1995).H.-W. Huang and K.-T. Chao, Phys. Rev. D54, 6850 (1996).J. Bolz et al., Phys. Lett. B392, 198 (1997).

Color octet graphs (qqg)

Color singlet graphs (qq) for

CJ → .

cJ pp,

(2S) cJ ΛΛ p-p+

Clear Λ Λ-barsignal

Monte Carlo

Data

cJ

c0 c1 c2

BcJ

(10 –4) 4.7 ± 1.0 2.6 ± 0.6 3.3 ± 0.7+1.3-1.2

+1.0-0.9

+1.5-1.3

PRD67, 112001 (2003)

Sideband background

Data/Monte Carlo

cJ signal

c0

c1 c2

c0

c2

c1

Final states: pp

)10( 4 0c1c 2c

)( ppB cJ )04(PDG 27.024.2 13.072.0 07.068.0

)( ppB cJ 47.071.2 43.039.0

09.057.0 17.015.0

10.065.0 24.021.0

cJ pp

0c1c 2c

BESRB 63.073.1

598.0

08.308.5

449.0

34.256.4

COM for cJ B B

Discussion

COMRB

Many systematic errors cancel!

Calculate

• The results on c1 and c2 decays only agree marginally with model predictions. • No prediction for c0 .

Phys.Rev.D69:092001,2004

cJ → KSKS

cJ → +-KSKS

BESII PreliminaryBESII Preliminary

cJ h+h-KsKs

(2S) cJ

cJ → K+K-KSKS

BESII PreliminaryBESII Preliminary

The branching fractions of cJ decays to +-KSKS and

K+K-KSKS are observed for the first time.

The branching fractions of c0 and c2 decays to KSKS are measured with improved precision.

Measure more decays to better

understand P-wave decays.

Study χcJ → K*(892) K*(892)

→ K+K-+-

Require Prob(24C) > 1% and

higher than +-+- and K+K-K+K-

cases, and PID imposed.

cJ K*(892)0K*(892)0

(2S) → +-K+K-

Accepted by Phys. Rev. D, hep-ex/0408012

K*(892)

significance = 4.7σ, 4.5σ, 7.6σ

c0 c1 c2

f0(980) controversial:

Even mass and width complicated

by KK threshold.

Experimental results needed.

Study (2S) → χc0

→ f0f0 → +-+-

Require Prob(24c) > 1%.

• qq-bar meson?

• KK-bar molecule?

• multiquark state?

• glueball ?

c0 f0(980)f0(980)

c0 → +-+- c2 → +-+-

f0f0

Results

N = 65 – 51/1.75 = 35.9 ± 9.0 significance = 4.6σ

ε = (3.92 ± 0.07)%

B((2S) → c0 → f0f0 → +-+-) = (6.5 ± 1.6 ± 1.3) x 10-5

B(c0 → f0f0 → +-+-) = (7.6 ± 1.9 ± 1.6) x 10-4

f0

Accepted by PRD, hep-ex/0406079

Plot mass recoiling

from f0(980)

• In general, it is believed that (2S) cJ is dominated by the E1 transition, but with some M2 (for c1 and c2) and E3 contributions (for c2).

• The calculated pure E1 transition rates and the experimental results are quite different.

Determine the contributions of the higher multipoles

• S- and D-wave mixing of (2S) and (3770) may be the key to solve the long-standing puzzle and to explain (3770) non-DD decays.

• Crystal Ball studied the decay angular distributions in (2S) c2 using (2S) J/ first; no significant higher multipoles found (with limited statistics).

c2 polarizationin (2S) c2, c2 +-, K+K-

No background from c1 since the c1 +-, K+K-

processes are forbidden by parity conservation.

The helicity amplitudes are determined by a maximum likelihood fit to the angular distribution, where x=A1/A0, y=A2/A0, A0,1,2 are the c2 helicity amplitudes.

good agreement is observed in all angular distributions

+-

K+K-

combine them,

quadrapole amplitude a2´

octupole amplitude a3´

consistent with the pure E1 transition well

: correlation factor

(CB)

Accepted by PRD, hep-ex/0409034

c decays to pp, , h+h-KsKs, K*0K*0 and f0(980)f0(980) are measured for the first time or with higher sensitivity using BESII’s 14 million (2S) data sample.

helpful to better understand the nature of c states and test the new QCD approach.

• The helicity amplitudes of (2S) c2 are measured for

c2 +- and K+K-, and x = 2.08 0.44, y = 3.03 0.66 with correlation = 0.92 are obtained.

in good agreement with a pure E1 transition

• More experimental facts are desired

Theoretical predictions…

SUMMARY

Thank you

谢谢