Recent BESII Results of Charmonium DecaysGang LIGang LI

CCAST&IHEP, BeijingCCAST&IHEP, Beijing

for Ψ(2S) GroupTopical Seminar on Frontier of Particle Physics

2005: Heavy Flavor Physics August 13- 17, 2005

Outline

Introduction cJ Study ’ Decay to Multihadrons Summary

0

2

4

6

8

10

12

14

MKI MKII MKIII CBAL BESI BESII CLEOc

Introduction

P-wave charmonium decays c0 , c1 , c2

3M

14M

6.42 pb-1 data at Ecm=3.65 GeV for continuum study.

4M

2001.Nov.01to 2002.Mar.02

cJ Study --- Motivation 1. Compared with J/, relative little is known about P-wave triplet cJ(J=0,1,2) decays, more data on exclusive decays of them are important for understanding of the nature of cJ.2. The decays of cJ , in particular c0 and c2 , provide a direct window on glueball dynamics in 0++ and 2++, as the cJ hadronic decays may proceed via ccbar gg qqbar qqbar 3. PWA is an excellent tool to investigate the intermediate resonant decay account for the interferences when calculating Brs.

Partial Wave Analysis of c0 K K

cJ Study (I)

1. Qi = 0 ; 2. p()+p( ) > 650 MeV [BG:’ J/ ]; 3. Prob( K K )> Prob(

)& Prob( K K )> Prob(

K K K K );4. M( ) [497±50] MeV/c2

& second vertex <5mm

[BG: KS ];

Event

level

c0 K K

Avoid introducing a huge number of partial waves and also limited by statistics; our study is devoted to c0 K K

1371 eventsc0

c1(3511.3±1.3MeV)

c0(3414.7±0.6MeV)

c2(3556.4±0.9MeV)

5C-

fitdot with

error bar :data

In our final fit, all thesepartial waves have beenincluded, together withtheir interferences.For convenience of narration, we are todescribe following decay modes one by one:

1. ( )( K K )2. (K )(K )3. (K ) K

1371 events

( )( K K )f0(1710)

f0(2200)

f0(980)

f0(1370)

(770)

S:change in log likelihood

S.Flatte, Phys. Lett. B 63(1976)224; B.S.Zou &D.V.Bugg, Phys. Rev. D48(1993)R3948Flatte formula :

）（ 22112980

1 ggMisM

f

i (s)=sqrt(1-4m2i/s) : phase space factor for &K K ;

g i : squares of coupling constants to &K K ;[B.S.Zou &D.V.Bugg, Phys. Rev. D48(1993)R3948]:M=0.9535; g1=0.1108 GeV; g2=0.4229 GeV;

For , formula once used by BES in analysis of J/ [ PLB598(2004)149-158]

MisMRBW 2

1Other resonances

Breit-Wigner formula :

( )( K K )

Positive values indicate poorer fits

Bad fit without scalar indicates that a scalar f0(2200) decays to K K is needed around 2.2 GeV .

( )( K K )

( )( K K ) ResultsBES II PDG2004

resonance Mass (M) and Width () [unit:MeV]

resonance Mass (M) and Width () [unit:MeV]

f0(1370) M:1265±30(+20–35) f0(1370) M:1200~1500

: 350±100(+105–60) : 200 ~500 f0(1710) M:1760±15(+15–10) f0(1710) M:1714±5

: 125±25(+10–15) : 140±10 f0(2200) M:2170±20(+15–10)

: 220±60(+10–15)

Significance : 5. 3

Significance : 7. 1

Significance : 6. 5

(K )(K )1371 events

MisMRBW 2

1BW formula:

with:3

022

20

20

0 11

pp

prpr

mm

m: mass of K system; m0 : mass of resonance; 0 resonance width; p: momentum of K in K system; p0: p evaluated at resonance mass; r=3.4: Interaction radius[D.Aston et al., NPB296(1988)493]

K*0(1430)

K*0(1950)

K*(892)0

Results

BES II PDG2004resonance Mass (M) and Width

() [unit:MeV]resonance Mass (M) and Width ()

[unit:MeV]K*0(1430) M:1455 ± 20 (+15–15) K*0(1430) M:1412 ± 6

: 270 ± 45 (+30–35) : 294 ± 23 K*0(1950) M:1945 ± 30 K*0(1950) M:1945 ± 10 ± 20

: ~500 : 201 ± 34 ± 79 #: 201 (fix to PDG in fit)

Significance : 7. 1

Significance : 7. 2

Significance : 8. 7

(K )(K )

(K )K

1371 events

M(K ) [896±60]

M( ) [700,800]

K1(1270)

K1(1270)

K1(1400)

K1 (1279): S-wave BW

K1(1400): S-wave BW

90% C.L.

K1(1270)

Strange axial meson mixing(K )K

K1(1270) =KA sinK + KB cos K ,K1(1400) = KA cos K – KB sin K ,

KA = K1(1270) sin K + K1(1400) cos K ,KB = K1(1270) cos K – K1(1400) sin K ,

Here is an interesting problem involving K1(1270), K1(1400), that is the mixing of the two strange axial mesons

In the quark model , there are two ground-state axial vector nonets, one is (3P1) state (KA) , the other is (1P1) state (KB). For a strange quark mass is greater than those of up and down quarks, so SU(3) is broken

which lead to mixing of KA and KB states to give a physical K1 state: viz.

or

In SU(3) limit, only KA couples to the weak current, and the degenerated twooctets before mixing lead to mixing angle ( K )equal to 45° which means that

there should be equal amount of K1(1270) and K1(1400).

Flavor-SU(3)-violating of K1(1270) -K1(1400) asymmetry is observed.

However, our PWA yields :K1(1270)K [Br:(42±6)%] signal of 68.3±11.0 events;K1(1400)K* [Br:(94±6)%] signal of 19.7±6.9 events;

Strange axial meson mixing(K )KAnother interesting problem here is about the mixing angle K. According to

present BES results, the mixing angle K >57º for c0

More interesting fact is from decay. By virtue of K1 measurement together with relativized quark model estimation, the mixing angle should be within a range:–35º< K <45º at 68% C.L. [H.G.Blundell et al. ,PRD53,3712(1996)]

But according to previous BES results, K <29º for [PRL83,1918(1999)]

K >48º for J/ [PRL83,1918(1999)]

All discrepancies displayed here indicate that more further theoretical and experimental works are needed.

Summary of PWA of c0 K K

Events: (1371-29) ; efficiency: (5.85 ± 0.01)%

CLEO:PRD70,112002(2004)

B(K*(892)K )=100%

=

BES:PRD70,09002(2004)

B(’ c0 f0(980) f0(980) )=(6.5 ± 1.6 ± 1.3) 10 –5

B(’ c0)=(9.22 ± 0.11 ± 0.46) 10 –3

Summary of PWA of c0 K K (con’t)

From these c0 K K fit results, it is found that scalar resonances have larger decay fractions compared to those of tensors, and such decays provide a relatively clean laboratory to study the properties of scalars, i.e. f0(980),f0(1370),f0(1710),f0(2200), K*0(1430), and so forth.

B(’ c0)=(9.22 ± 0.11 ± 0.46) 10 –3CLEO:PRD70,112002(2004)

First evidence of c0, c2

cJ Study (II)

•Kinematic fit6-C fit is required, the additional 2-C is that two pair photons all satisfy M

=M0, Furthermore, 2(6C)<12 •Prob(6C)> Prob(7C) is added if N>5 so that the background from the potential 0,2 +00 can be suppressed.

Removing the recoil J/ events by minimizing |M+-(recoil)-MJ/|, the recoiling mass of the candidate pion pair can’t fall into J/ peak region(3.08-3.12GeV).

Event selectionEvent selection

Some distributions in 0,2 from data

Sideband region: 200 MeV wide aroun

d peak

Event levelEvent level

Signal region

c0c2

0 +0+054(=1.66%)MC simulationMC simulation

c0

Fit mass spectrum

No obvious signal is found in sideband.

M(c0)=3420.1±9.0MeVM(c2)=3553.3±11.9MeV

(BW fit ;width fixed)

c0

c2

Backgroundsideband

N(c0)= 38.19.9Sif. 4.4

N(c2)= 27.77.4Sif. 4.7

(Mass & width fixed)

dot with error

bar :data

The signal is described by BW convoluted with double-Gaussian obtained from MC simulations and background shape is determined by sideband shape.

Summary of c0, c2 decay

)()()( 02BBN

NBcJ

obscJ

• We first observed 0,2 decay and measure their branching ratios. • We did not see obvious evidence below 3.2 GeV energy region.

’ decay to Multihadrons

’ 3(+-)

’ +-0K+K-

Strong decay of ’ 3(+-) suppressed due to G-parity violation.

e+e- 3(+-) EM process (continuum contribution) will be estimated by off-resonance data @3.65 GeV.

X-sections @3.65 & 3.686 GeV give the EM form factor for 3(+-) state.

BR of J/ 2(+-) determined via ’ +-J/ , J/ 2(+-).

’ 3(+-)

’ 3(+-)

ψ’ π+π-J/ ψ, J/ψ 2(π+π-) bkgd removed by requiring

3.06< <3.14 GeV

MππrecM

recM

4C fit for ψ’ π+π- π+π- π+π-

ψ’ KsKs π+π- bkgd removed by requiring 2 π+π- pairs satisfyi

ng 0.47<M ππ<0.53 GeV

PRD71(2005)072006

Ks bkgdJ/ bkgd

’ 3(+-)

ψ’ 3(π+π-) @3.686 GeV

Histogram = signal MC@3.686 GeV + continu

um @3.65 GeV

Hatched histogram = e+

e-3(π+π-) DT@3.65 GeV

4C fit for π+π- π+π- π+π- final state

e+e-3(π+π-) @3.65 GeV

Histogram = MC simulation

BR of J/ 2(+-)Systematic error reduced by

comparing 2 processes:

Difference between MC & DTdue to the simulation of error matrix in

track fitting.Taken into account in systematic error.

Confidence level distribution for kinematic fitting of

+- J/ , 2(+-)

recM

’ 3(+-) RESULTS ’ 3(+, - ), J/ 2(+, - ) BRs measured with improved accuracies. B[’ 3 (+, -)]= (5.450.42 0.87) x 10 –4

greater than Mark I result (1.51.0) x 10 –4 {PRD17(1978)1731} B[J/ 2(+, -)]= (3.530.12 0.29) x 10 –3

consistent with Mark I result (4.01.0) x 10 –3 {PRL 36(1976291} and BaBar result (3.610.26 0.26) x 10 –3 { hep-ex/0502025 } • pQCD 12% rule tested. Q[3(+, -) ]= (148)% Q[2(+, -) ]= (133)% • Form factors for e+e- 3(+, - ) at Ecm=3.65, 3.686 GeV determined F3.65 [3(+, -) ] = 0.190.02 F3.686 [3(+, -) ] = 0.240.02

’+-0K+K-

• PID for π and K• 4C kinematic fit for ’+-γγK+K-

• | -3.096 | >0.05 GeV/c to reject ’+- J/• removed by identifying Ks+-

• Fit M(γγ) to obtain ’+-0K+K- evts.

0 KK s

recM

Mγγ @ Ecm=3.686 GeV Mγγ @ Ecm=3.65 GeV

0: 69841 evts. 0: 357 evtsPreliminary

’ωK+K-

• | Mγγ – 0.135 | <0.03 GeV/c2 to select ’+ - 0K+K- evts. ’ωK+K- evts are obtained by fitting M(+ - 0).

M(+-0) @ Ecm=3.686 GeV M (+-0) @ Ecm=3.65 GeV

Preliminary

ω: 7811 evts. ω: evts.@68.3% C.L.3.100

’ωf0(1710)

Dalitz plot

for ’ωK+K- candidates

M(K+K-) for ’ωK+K- candidates

Preliminary

’ ωf0(1710)

18.9 6.2 evts.

’+-0K+K-

Preliminary resultsChannel BΨ’ h(10-4) BJ/Ψ h(10-4) Qh(%)

K ＋ K － π ＋ π －π0

12.4 1.8 120 28 10.3 2.9

ωK ＋ K － 2.38 0.47 16.8 2.1 14.2 3.4

ω f0(1710) ωK ＋ K －

0.59 0.22 6.6 1.3 8.9 3.8

The PWA on c0 K K in ’ c0 decay is preformed. We fit the significant contributions from f0(980) f0(980) , f0(980) f0(2200) , f0(1370) f0(1710) , K* (892) 0 K* (892) 0 , K*

0 (14

30) K* 0

(1430) , K* 0

(1430) K* 2(1430) +c.c.

Flavor-SU(3)-violating of K1 (1270)-K1(1400) asymmetry is obs

erved and the mixing angle between two strange axial mesons is determined to be greater than 57 degree.

First observed c0, c2 decay and their branching ratios are measured.

Summary

BRs of ’ 3(+–), J/ 2(+–) with improved accuracy.

F[3(+–)] determined at Ecm=3.65, 3.686 GeV.

BRs of ’ +–0K+K–; ωK+K–; ωf0(1710)ωK+K– with improved accuracy.

Summary （ cont’d ）

Thanks a lot !