1. PWA of J/pp0 and measurement of J/pp, pp'
H.X. Yang (for BESII collaboration.)
Workshop on the Physics of Excited Nucleon – NSTAR2009, Beijing, April 19 – 22, 2009

2. Outline Introduction of BEPC and BESII Motivation PWA of
Measurement of
Summary

3. Beijing Electron Positron Collider (BEPC) at IHEP
L ~ 51030 /cm2s
at J/
Ebeam~ 1 – 2.5 GeV
BESI: run from
BESII: run from
BESIII: running

4. BESII @ BEPC VC: xy = 100 m TOF: T = 180 ps  counter: r= 3 cm
MDC: xy = m BSC: E/E= 22 % z = 5.5 cm
dE/dx= 8.5 %  = 7.9 mr B field: T
p/p =1.7%(1+p2) z = 3.1 cm 4

5. Motivation Probe the internal structure of baryons
Search for missing baryons predicted by quark model
Obtain a better understanding of the strong interaction force in the non-perturbative regine

6. First observation of N(2065)
With J/pn-
N*(1520)
N*(1535)
N*(1440)?
N*(1650)
N*(1675)
N*(1680)
Quark model predicts
N(2050).
Never observed. ?
N(2050): 1/2+ or 3/2+
N(1440):
（N(1440) peak: never be found before)
Phys. Rev. Lett. 97 （2006）062001

7. Study of (i) 0 
M2(p0)
M

8. study of (ii)

9. PWA of (iii)
Resonances used in PWA

10. Example of mass and width scan
PWA of (iv)
Example of mass and width scan
After we decide the best fit result and check there isn’t other N* state needed, we optimize the masses and widths of some N* states.
This is an example of mass and width optimization during our analysis.
The left plot is mass optimized result and right is width optimized results of N(1520)

11. Comparison of data With fit results (I)
PWA of (v)
Comparison of data With fit results (I)
+ : data
hist.: fit

12. Comparison of data With fit results (II)
PWA of (vi)
Comparison of data With fit results (II)

13. PWA of (vii)
Nx(2065) exists in this channel with high significance (>>5σ)
The spin-parity favors 3/2+ N*
M(MeV/c2)
(MeV/c2) JP
fraction(%)
Br (×10-4)
N(1440)
1/2+
9.74~25.93
1.33~3.54
N(1520)
3/2-
2.38~10.92
0.34~1.54
N(1535)
1/2-
6.83~15.58
0.92~2.10
N(1650)
1/2-
6.89~27.94
0.91~3.71
N(1710)
1/2+
4.17~30.10
0.54~3.86
N(2065)
3/2+
23.0~41.8
0.91~3.11

14. Measurement of the branching ratio
PWA of (viii)
Measurement of the branching ratio
Estimate the detection efficiency of each resonance and normalize them with the corresponding fraction in PWA result. The total efficiency of is %
We measure the branching ratio after the partial wave analysis because we use the detection efficiency include N*s.
After the systematic errors analysis we get the branching ratio of J/psi to ppbar pi0 is ….

15. Study of (i)
+-0

’+-
’

16. Study of (ii)
Invariant mass spectrums in

17. Study of (iii)
Invariant mass spectrums in

18. Study of (iv) Measured Branching Ratios Decay Modes Nobs Br (10-4)
PDG
BESII
J/p pbar  ()
J/p pbar  (+-0)
148.9
953.744.7
20.9  1.8
19.20.21.8
18.30.92.4
J/p pbar ’ (’+-)
J/p pbar ’ (’)
64.511.5
200.329.3
94
2.30.40.4
1.90.30.3

19. summary The new excited baryon Nx(2065) is confirmed
in with JP=3/2+ and
Clear signals for N* are observed, the masses, widths and branching ratios are measured with PWA on
N* signals are also observed in
The branching ratios of
and are measured

20. THANK YOU!