Zijin Guo

Univ. of HawaiiRepresenting BES Collaboration

J/ pp and

BES

Beijing, China

The BES Detector

TOF

EM Shwrcounter

World J/ and (2S) Samples (106)

J/ (2S)

0

10

20

30

40

50

60

MarkI I I DM2 BES I BES I I

0

2

4

6

8

10

12

14

MKI MKII MKIII CBAL BESI BESII

A narrow pp enhancementnear Mpp 2mp in J/pp

NN bound states (baryonium)??

+ n +

deuteron:

loosely bound 3-q 3-

q color singlets with

Md = 2mp-

baryonium:

loosely bound

3-q 3-q color singlets with Mb = 2mp-?

attractive nuclear force attractive force??

There is lots & lots of literature about this possibility

ppe+e

Bardin etal

e+ehadronsFENICE e+e6

2mp

2mp

Fit: M = 1870 ± 10 MeV= 10 ± 5 MeV

R. Calabrese PEP-N work-shop proceedings

DM2 unpub.

Is there a narrow JPC=1 pp system near Mpp = 2mp?

study pp from J/pp

• C-parity = +

• S (P?)-wave (for Mpp 2mp)

• probes JPC= 0(0?) states

• complements ppee and ee annihilation

• unpolluted (by other hadrons) environment

Use BESII’s 58M J/ decays

J/pp

Select J/pp

• 4-C kinematic fit

• dE/dx for proton id

• non-pp bkg small

• main bkg from J/pp

????

• J/ccpp (calibration reaction)

Fit signal with an S(P)-wave BW

200

220

2

312000

)()(

)/(

MMM

kqqMBW

l

q = daughter momentum

q0 = daughter momentum @ peak

keep consta

nt

threshold factor

Fit to data

M=1859 MeV/c2

< 30 MeV/c2 (90% CL)

J/pp

M(pp)-2mp (GeV)

0 0.1 0.2 0.3

3-body phase spaceacceptance

2/dof=56/56

fitted peak location

acceptance weighted BW +3 +5

10 25

P-wave fit??

M=1876 ± 3 MeV < 30 MeV (90% CL)

2/dof=59/56

OK!

M=2mp

cos distribution

1+cos2(expected for

J/)

sin2

M(pp)<1.9 GeV

Summary (I)

if what we see is an S-wave resonance:

M=1859 MeV/c2

< 30 MeV/c2 (90% CL)

+3 +510 25

A narrow pp enhancementnear Mpp 2mp in J/pp

• not consistent with any PDG meson state

• peak below, but near 2mp : baryonium?

• narrow width: why so long-lived?

• similar patterns seen in baryon-antibaryon systems produced in B meson decays

– BppK BppD Bp Bpc

Strange & charmed systems

Bp

M(p)(GeV)

Bpc

M(cp)(GeV)

(in these cases, the peaking doesn’t seem to be right at threshold)

Partial Wave Analysis of J/KK

• Lattice QCD: the ground state scalar glueball should be in the mass range 1.5 – 1.7 GeV

• Long history of uncertainty about f0(1710)

• J/ K+K- and KSKS are very important to investigate the f0(1710)

Data and Analysis Method • Perform separate amplitude analyses for

J/ K+K-

KSKS

• Amplitudes are fit to relativistic covariant tensor expressions (mass range 1-2 GeV)

• The maximum likelihood method is employed

• Bin-by-bin fit: the data are analyzed independently in each mass bin (40MeV)

Global fit: Breit-Wigner structures + mass, width scan + lnL comparison

The K+K- and KSKS mass distributions from J/ radiative decay after

acceptance and isospin corrections

J/ f’2(1525)

f0(1710)

f2(1270)

f0(1500)

+broad 0++ and 2++

Components used in the PWA fit

Bin-by-bin fit Global fit

Amplitude intensity

Summary (II)

• Using BESII data, partial wave analyses

were done on the K+K- and KSKS

systems produced in J/ radiative decay for the mass range 1-2 GeV

• KK D- wave intensity shows a clear f’2(1525) signal and the helicity amplitude ratios x,y appear to be consistent with the theoretical prediction

• Strong production of f0(1710) M = 1740±4±10 MeV Г = 166+5+15 MeV (Global fit)

• The non-flat angular distribution in the KK mass region ~1.7 GeV is due to the interference between S- wave and weak D- wave amplitudes

• Bin-by-bin fit and global fit give very consistent analysis results

25

-8

-10

Results

Bin-by-bin

Global

Systematic Error global fit

Study J/0pp bkg with MC & data

J/0pp (data)

three-bodyphase spaceMonte Carlo

J/0pppp (MC)

M(pp)-2mp (GeV)

no peak!!

Is Mpeak really less than 2mp?

No turnover at thresholdpeak mass must be <2mp

weight events by q0/q:(i.e remove threshold factor)

M(pp)-2mp (GeV)

mass determination bias

threshold

observed peak

BW “peak”below-

threshold mass & widths measurement

s can be biased

when there is background

could it be a tail of a known resonance?

0 resonances in PDG tables:(1760) M=1760 = 60 MeV

(1800) M=1801 = 210 MeV

2/dof=323/58 2/dof=412/58

Coulomb effect?

2

)3(

)/exp(1

/ 2vv

v

v

coulomb factor

phase-spaceterm

BW vs Coulomb