Transcript Update on J/y gpp

J/y  gpp and gKK
Zijin Guo
Univ. of Hawaii
Representing BES Collaboration
Beijing, China
BES
The BES Detector
EM Shwr
counter
TOF
World J/y and y(2S) Samples (106)
y(2S)
J/y
60
14
50
12
10
40
8
30
6
20
4
10
2
0
0
MarkIII
DM2
BESI
BESII
MKI
MKII
MKIII
CBAL
BESI
BESII
A narrow pp enhancement
near Mpp  2mp in J/ygpp
NN bound states (baryonium)??
There is lots & lots of literature about this possibility
deuteron:
baryonium:
attractive nuclear force
+
n
loosely bound
3-q 3-q color
singlets with
Md = 2mp- e
attractive force??
+
-
loosely bound
3-q 3-q color
singlets with
M = 2m -d ?
Is there a narrow JPC=1- - pp system
near Mpp = 2mp?
2mp
e+e-hadrons
FENICE
ppe+eBardin etal
e+e-6p
2mp
DM2
unpub.
Fit: M = 1870 ± 10 MeV
G = 10 ± 5 MeV
R. Calabrese PEP-N
work-shop proceedings
study pp from J/ygpp
• C-parity = +
• S (P?)-wave (for Mpp  2mp)
•  probes JPC= 0-+ (0++?) states
• complements ppe+e- and e+e- annihilation
• unpolluted (by
other hadrons)
environment
Use BESII’s 58M J/y decays
Select J/ygpp
• 4-C kinematic fit
• dE/dx for proton id
• non-pp bkg small
• main bkg from J/yp0pp
• J/yghc ; hc pp
(calibration reaction)
J/ygpp
????
Fit signal with an S(P)-wave
BW
threshold
factor
2l +1
M 0G0 (q / q0 ) k
BW 
2
2 2
2
(M - M 0 ) + (M 0G0 )
3
keep
constant
q = daughter momentum
q0 = daughter momentum @ peak
Fit to data
fitted peak
location
acceptance
weighted BW
J/ygpp
+3 +5
M=1859 -10 -25 MeV/c2
G < 30 MeV/c2 (90% CL)
c2/dof=56/56
0
3-body phase space
0.1
0.2
M(pp)-2mp (GeV)
0.3
acceptance
P-wave fit??
M=1876 ± 3 MeV
G < 30 MeV (90% CL)
M=2mp
c2/dof=59/56
OK!
cosqg distribution
1+cos2qg (expected for J/yg0-+ )
M(pp)<1.9 GeV
sin2qg
Summary (I)
if what we see is an
S-wave resonance:
+3 +5
2
M=1859 -10 -25 MeV/c
G < 30 MeV/c2 (90% CL)
A narrow pp enhancement
near Mpp  2mp in J/ygpp
• 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
– BppK BppD BpLp BpLcp
Strange & charmed systems
B0pLp-
B-pLcp-
M(Lp) (GeV)
(in these cases, the peaking doesn’t
seem to be right at threshold)
M(Lc+p) (GeV)
Partial Wave Analysis of J/ygKK
• 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/y  gK+K- and gKSKS are very important to
investigate the f0(1710)
Data and Analysis Method
• Perform separate amplitude analyses for
J/y  gK+KgKSKS
• 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/y
radiative decay after acceptance and isospin
corrections
J/y  gf’2(1525)
gf0(1710)
gf2(1270)
gf0(1500)
g+broad 0++ and 2++
Components used in the PWA fit
Bin-by-bin fit
Amplitude intensity
Global fit
Summary (II)
• Using BESII data, partial wave analyses
were done on the K+K- and KSKS systems
produced in J/y 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
25
+5+15
Г = 166
MeV
-8 -10
(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
Results
Bin-by-bin
Global
Systematic Error
global fit
Study J/yp0pp bkg with MC & data
J/yp0pp (data)
no peak!!
J/yp0ppgpp (MC)
M(pp)-2mp (GeV)
three-body
phase space
Monte Carlo
Is Mpeak really less than 2mp?
weight events by q0/q:
(i.e remove threshold factor)
No turnover at threshold
peak mass must be <2mp
M(pp)-2mp (GeV)
mass determination bias
below-threshold
mass & widths
measurements
can be biased
when there is
background
BW “peak”
observed peak
threshold
could it be a tail of a known
resonance?
0-+ resonances in PDG tables:
h(1760) M=1760 G = 60 MeV
p(1800) M=1801 G = 210 MeV
c2/dof=323/58
c2/dof=412/58
Coulomb effect?
p / v
v(3 - v )

1 - exp(-p / v)
2
2
coulomb
factor
phase-space
term
BW vs Coulomb