Download - Recent Results from BES J/ and (3770) Decays
Recent Results from BES J/ and (3770) Decays
Xiaoyan SHENRepresenting BES Collaboration
Institute of High Energy Physics (IHEP)CAS, Beijing, [email protected]
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.)
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 /