Recent Results from BES J/ and (3770) Decays

Xiaoyan SHENRepresenting BES Collaboration

Institute of High Energy Physics (IHEP)CAS, Beijing, P.R.Chinashenxy@ihep.ac.cn

2nd International Workshop on Heavy Quarkonium Sept. 20 – 22, 2003, Fermilab

Outline Introduction Study of and Precise measurement of Study of Measurement of Study of the excited baryon states -- N* in the decay of

-- N* and * in the decay of

(3770) J/ . Summary

ppJ /

npJ / pKJ /

0/ J

),(/ VVJ

J/ data samples

0

10

20

30

40

50

60

CBAL MK II MK III DM2 BES I BES II

BESII 58M

J/ events

BESI 7.8M J/ events

DM2 8.6M J/ events

MKIII 5.6MJ/ events

MKII 5.6MJ/ events

CBAL 2.2MJ/ events

Introduction to J/ Physics

3-gluon Electromagnetic Radiative Via c

a good lab for studying hadron spectroscopy a good lab for excited baryon states hunting for glueballs in J/ radiative decays

in J/

-- 4 good charged tracks with total Q=0

-- 2 or more good photons

-- Particle ID by TOF and dE/dx

-- 24C (J/++) < 40

-- Selection of 0 : | M - M 0 | < 40 MeV

-- Selection of : | M + 0 - M | < 40 MeV

BESII 58M J/

Two methods are used:

Method 1 Method 2

M+ <1.55GeV whole M+ region treats as a particle uses the decay info. J/f2(1270) J/f2(1270)

f0(980) f0(980) b1(1235) b1(1235) 0 ’(1450) phase space f2(1565) f2(2240)

Pole position of (BESII preliminary)

If the σ amplitude is written as:

pole: (542 ±10 ± 40 ) – i(249 ±25 ±60) MeV

If (s) = 0(s)/ (M2) pole: (516 ± 15 ± 50 ) – i(313 ±25 ±65) MeV

If = constant pole: (540 ± 10 ± 40 ) – i(267 ±30 ±65) MeV

Fit to the J/→+

f0 contribution f2 contribution

b1(1235)

preliminary

in J/ K*K and K+K-

4 good charged tracks with total Q=0 Particle ID by TOF and dE/dx, prob(K/ ) > 0 24C (J/K+K +) <40 prob4C(K+K + )probpid(K+) probpid(K) probpid(+) probpid() > other particle assump. ( ++ ;K+KK+K; K + ) Remove KS, by | M + - MKS| > 0.04 GeV; | M K+K - M | > 0.02 GeV

Before K*(892) 0 cut

After K*(892) 0 cut

Method 1:

selecte K*0(892): | M + K - 0.892| < 0.08GeV study K+ spectrum

contribution

s

spgs

ssismBW

8

)()(

)(

1

12

2

If is treated as a resonance,

)191( 851 691683253

1074313047

i

Pole position:

MeV

Fit J/→K+K-+- whole phase space

Method 2

If amplitude is written as:

K0(1430) is fitted with a flatte formula:

Pole position: )35400( )35810( .. statstat i MeV

Precise measurement of J/

The angular distribution of two baryon final

states can be written as

Where is the angle between the baryon direction and

the positron beam direction

Theoretical models from first order QCD give

various value predictions.

pp

BB

d

dN 2cos1cos

B

Status of J/ pp

theo1:S.L.Brodsky,G.P.Lepage, Phys. Rev. D24, 2848(1981)theo2:M.Claudson,S.L.Glashow,M.B.Wise, Phys. Rev. D25, 1345(1982)theo3:C. Carimalo, Int. J. Mod. Phys. A2, 249(1987)

BES measurement on J/

Br=(2.26 ±0.01 ±0.12) ×10-3

=0.676±0.036±0.027 , agrees with theo3

sys. error

sys. error

pp

Study of J/V (V=,)

o Theoretical prediction for (1440)

state : =9 : 2

Pure glueball: : =1 : 1

o MARKIII Results (1440) →

Mass= 1432 ± 8MeV

= 90 ± 26 MeV

B(J/ → ) ×B( → )

=(0.64±0.12±0.07)×10-4

(1440) → B(J/ → ) ×B( → ) < 1.6×10-4 (90% C.L.)

qq

BES results on (preliminary) /J ’ f1(1285) (1440)

BCK from J/→0,

B(J/X)=(0.310.30)10-

4

B(J/X)<0.8210-4

95% C.L.

BES results on (preliminary) /J

After BCK subtraction

48.4847.14 events

Measurement of J/→ +-0 (preliminary)

Absolute Measurement from BESII 58M J/ Decays

Basic Criteria:

Two oppositely good charged tracks

At least two good photons

5C kinematic fit 2(+-0)15

Further Criteria: 5C kinematic fit 2(+-0)2(K+K-0) to reject J/→ K+K-0

(+-)10 to reject conversion

The photon angle in the 0 rest frame

|cos|<0.98 to reject radiative events,

Further Criteria(continued):

such as J/→’The deposited energy of two charged pions in Barrel Shower Counter less than 2GeV to reject J/→()e+e-

Remaining BG less than 1% relative from MC study (BG mainly comes from J/

K+K- 0 and ’).

Signal selection efficiency is 17.83%

0S

B(J/ →+-0) =(21.350.041.85)10-

3

00

+-

-+

+0

Systematic errors include: BG from continuous energy region(1%), reconstruction of each charged track(2%), photon detection(2%), 5C kinematic fit(2.9%), further criteria(1%), MC model uncertainty(3%), BG uncertainty(1%) and J/ total number(5%) TOTAL 8.7%

m+0

m+-

m-0

Relative Measurement from 14M (2S) Decays

BESII 14M (2S) :

B(J/→+- 0)=(20.90.21.1)10-3

(preliminary)

Similar cuts are used for process I and II , many systematic errors can be cancelled.

PDG: (15.0 2.0) 10-3 inconsistent !

Discussion on BESII J/→+- 0 results

BESII 58M J/ : B(J/ →+- 0)=(21.350.041.85)10-3 is well consistent with BESII 14M (2S) :B(J/→+- 0)=(20.90.21.1)10-3

Combining BESII J/ , (2S) : B(J/B(J/→→++- - 00)=(21.0)=(21.01.1)1.1)1010-3-3

Inconsistent with PDG : J/J/→ → ++--00 = = (152)10-3

Extensive and careful checks on BESII SIMBES DATA consistencies have been made, such as MDC reconstruction, kinematic fit χ2 , photon detection, Barrel Shower Counter performance.

No significant BESII SIMBES DATA inconsistency has been found

J/----- : DATA : SIMBES

J/----- : DATA : SIMBES

4C-fit 2(+- 0)

5C-fit 2(+- 0)

An example of BESII SIMBES DATA consistency check:

5C kinematic fit 2(+- 0)<15 efficiency systematic error is about 2.9%

Cut here

Study of Excited Baryon States

Probe the internal structure of light quark baryons Search for missing baryons predicted by quark model Obtain a better understanding of the strong interaction fo

rce in the non-perturbative regime Jefferson Lab. electro&photo-production exps. CB-ELSA facility at Bonn University SPRING8 in Japan GRAAL at Grenoble of France started exps

J/ decays

processes branching ratios(10-

3)N* decays

2.00.1

6.00.5

2.00.1

2.10.2

0.90.4

1.30.3

0/ ppJ ppJ /

relatively large branching ratios (PDG2002) (58M J/)

npJ / ppJ /

'/ ppJ ppJ /

NN *

NN *NN *

NN *NN '* NN *

Pure isospin 1/2

Feynman diagram of the production of

For and , N and N systems are limited to be pure iso

spin 1/2.

**,*,*, Np

/J NN /J NN

from BESII data

Events selection

2 good charged tracks Q1+Q2 = 0 |cos| < 0.8 PID: TOF and dE/dx Mp > 1.15 GeV

0.88<Mmiss<1.0 GeV

/J p n

N* in /J p n

N*(1440)

N*(1520)

N*(1535)N*(1650)

N*(1675)

N*(1680)

?

• Estimate the BG from the fitting of the data.

• The Monte Carlo of J/ inclusive decay is also used in the background analysis.

• Background < 8%.

BG estimation

N* in /J p n

Sideband events1.1<Mmiss<1.15

No bump around 2.0 GeV

Fitting formula

k : momentum of q : proton momentum in Mx frame

2 1

2 2 2 20 0 0( )

lq k

M M M

n

►Possible new N* resonance (preliminary)

► Detailed information needs PWA

+15 2 2-30M = 2065 3 MeV/c =175 12 40MeV/c

N* in /J p n

from BESII data

Two clear peaks at 1520, 1690 MeV/c2 in pK mass N* in K mass PWA is being performed

)(GeV/M 2pK c )(GeV/M 2

KΛ c

N*(1650)

pKJ /

Search for the (3770) non- decay to +- J/

DD

Motivation--- (3770) is believed to be a mixture of the 23S1

and 13D1 states of the system and to decay almost entirely to pure .

ccDD

(P.A. Rapidis et al., (MARK-I), Phys. Rev. Lett. 39, 526(1978))

--- Recently, some theoretical calculation point out that (3770) could decay to non- final states.

DD

(H.J. Lipikin, Phys. Lett. B179, 278(1986), Y.P. Kuang, Phys. Rev. D65, 094024(2002) )

• 4 good charged tacks• PID based on TOF, dE/dx and BSC• COS > 20o

Ell - ECM<2.5ll

Mll - M<150MeV

Rcoil mass of Fitted mass of ll

/)3770( J /)3770( J

Pfit(2,4)>1%

Evidence of (3770) J/ , J/ in a data set of 8.0 0.5 pb-1 at BESII

ll

Background due to (2S)

The number of background due to (2S) production around the nominal center-of-mass energy was estimated by Monte Carlo.

Differential cross section for

and

productions at actual c.m. energy

/'' J /' J

][GeV ll of Mass fitted

cmE

/)3770( J /)2( JS

MC (400 data)

Branching fraction

)%16.028.058.0()/( '' JBF

)%16.026.059.0()/( '' JBF

(no K. F.)

(Kinematic Fit)

410)3.17.5('' prodN

(8.2 2.9) - (1.4 0.2) events

(8.83.3) - (1.9 0.2) events,

Summary Based on BESII 58M J/ (preliminary)

is clearly seen in J/. The pole position of is determined.

is studied in J/ K*K and K+K-. The pole position of is determined.

Br.(J/ )= (2.26 ±0.01 ±0.12) ×10-3

= 0.676±0.036±0.027

J/(1440), is observed, but no

clear signal

pp

Br(J/ →+- 0)=(21.01.1)10-3

A possible “missing” N* is found in

PWA to BESII 58M data is in progress

In , two peaks around 1520 and 1690 MeV in pK mass are clearly seen.

Evidence of (3770) J/ .

+15 2 2-30M = 2065 3 MeV/c =175 12 40MeV/c

/J p n

/J

pKJ /