1. Search for Rare and Forbidden Processes at BES
-- Only some selected topics
Xiaobin Ji
Institute of High Energy Physics, CAS
Beyond the Standard Model
Aug. 7 – 11, Beijing

2. Focus on the Following Topics
Invisible decays of mesons
Weak decays of 
Lepton Flavor/baryon number violated decays

3. Invisible Quarkonium Decays

4. Invisible Quarkonium Decays
With in SM, the invisible quarkonium decays are predicted by:
hep-ph/ , L.N Chang, O.Lebedlev and J. N. Ng
With 2-3% uncertainty!
One get:
Theoretical clean process
can be used to test model
and probe new physics!
Br(Y(1S) ) = 110-5
Br(J/  ) = 2.69 10-8
New physics may enhance the production rate of the invisible
Charmonium decays.

5. MeV Dark Matter Candidates
511KeV emission line from SPI group at INTEGRAL satellite
in France
P. Jean et al
Astron. Asronphys
407(2003) L55
The intrinsic line width is
2.950.5 KeV
The Gamma-ray is centered just at positron mass,
They are from the annihilation of positronium in the
Galactic center.
The low energy e+e- pair could be from the annihilation of
lighter Dark Matter candidates
C. Boehm et.al Phys. ReV. Lett. 92(2004)101301

6. Dark Matter (Exist?)
A halo exist, and
imply dark matter existence

7. (1-100)MeV Dark Matter: Has it been detected
If the Dark Matter (DM) annihilation happened in Galactic center
00  e+e-
The energy loss of e+e- will be inside (confined) in Galactic Bulge
SPI can see the 511KeV line
Phys. Report
405, 279(2005)

8. New Physics in Heavy QQ Decays
H(QQ)   : looking for invisible decay in Y(nS) and (ns)
n = 1, 2,3 ; hep-ph/
Br(Y(1S)  ) = 0.41%
Br(J/   ) = 0.023%
Br(   ) =0.033%
SM:
Br(Y(1S) ) = 110-5
Br(J/  ) = 2.69 10-8
Search () invisible decay using 58 M J/ data of BES II

9. J//, where / invisible
Reconstructing K+K , looking at missing mass or missing momentum of  decays
Fast  (1.2 GeV) will help us define the decay direction of
invisible decay of /
No any hit information are required
outside of the core of  decays.
Tag direction
Missing
direction

10. Results of J//, where / invisible
Signal MC
58 M J/
 missing momentum distribution
Extended ML fit is used
hep-ex/

11. Weak Decay of  search for

12. Weak decays of J/y at BES II
Kinematically J/y can not decay into charmed meson D pairs, however it can decay into signal D meson. The study provides tests of SM theory and serve as a probe to New Physics
Feynman diagrams for the weak decays processes
The Feynman diagram for the Flavor Changing Neutral Current process , it is a typical contribution to cu FCNC transitions in the Minimal Supersymmetric SM.

13. Decay modes used in the analysis

14. Results 58 million J/y data at BES-II  K*
Accepted by PLB: hep-ex/
58 million J/y data at BES-II  K*

15. Results

16. Lepton flavor violating processes in J/ decays

17. Introduction of LFV
In the SM, the lepton flavor symmetries are conserved
In many extension of the SM, such as SUSY, GUT, left-right symmetric models, lepton flavor symmetries speculated to be violated
SuperK, SNO, and KamLAND experimental results indicates strongly m0, and mix with each others.

18. BES II Results m momentum distribution BESII upper limit
BR(J/  e) < 1.110-6
BR(J/  et) < 8.310-6
BR(J/  mt) < 2.010-6
with 58M J/  sample
BESII
PLB561, 49 (2003)
PLB598, 172(2004)

19. Prospects of BES III

20. BESIII Detector Magnet: 1 T Super conducting xy=130 m
Two rings, 93 bunches:
Luminosity
1033 cm-2 s-1 @1.89GeV
6 1032 cm-2
6 1032 cm-2 2.1GeV
Magnet: 1 T Super conducting
MDC: small cell & He gas
xy=130 m
sp/p =
dE/dx=6%
TOF:
T = 100 ps Barrel
110 ps Endcap
Muon ID: 9 layer RPC
Data Acquisition:
Event rate = 3 kHz
Thruput ~ 50 MB/s
EMCAL: CsI crystal
E/E = GeV
z = 0.6 cm/E
Trigger: Tracks & Showers
Pipelined; Latency = 6.4 ms
The detector is hermetic for neutral and charged particle with excellent resolution ,PID,
and large coverage.

21. Charm Productions at BEPCII
Average Lum: L = 0.5×Peak Lum.; One year data taking time: T = 107s
Nevent/year = exp L T
Resonance
Mass(GeV)
CMS
Peak Lum.
(1033cm-2s-1)
Physics Cross Section (nb)
Nevents/yr
J/
3.097
0.6
3400
10  109
t+t-
3.670
1.0
2.4
12  106
(2S)
3.686
640
3.2  109
D0D0bar
3.770
3.6
18  106
D+D-
2.8
14  106
DsDs
4.030
0.32
1.0  106
4.170
2.0  106
Huge J/ and (2S) sample at BESIII;
Largest D/DS sample near the threshold.

22. Sensitivities of Charmonium Invisible Decays at BES-III
3X109 y(2S) events per year at BES-III
Invisible
The sensitivity at BESIII will be for J/y, C and C  Invisible ,

23. Study of invisible decays of , , ’,  and  in J/ two body decays
10X109 J/y events per year at BES-III
Invisible
The sensitivity at BESIII will be for , ’ Invisible ,

24. Access to Weak J/ Decay at BESIII (1)
J/   DS (DS*) M (M = p, r, ,,’,K, K*,)
hep-ph/ , K. Sharma
J/   PP
Mode
Decay
Br(10-10)
( 40% )
DC = DS=+1
(c  s )
DC=+1,DS=0
(c  d)
  DS+ p-
 D0 K0
DS+K-
 D+p-
 D0
 D0 ’
 D0p0
8.74
2.80
0.55
0.016
0.003
0.055
J/   PV
Mode
Decay
Br(10-10)
( 40% )
DC = DS=+1
(c  s)
DC=+1,DS=0
(c  d)
  DS+ r-
 D0 K*0
DS+K*-
 D+r-
 D0r0
 D0 
 D0
36.30
10.27
2.12
2.20
0.22
0.18
0.65
<
G (  DS*+ p- )
R =  3.5
G(  DS+ p-)
Sensitive to new physics
if larger BRs measured.
G (  DS*+ r- )
R =  1.4
G(  DS+ r-)

25. Access to Weak J/ Decay at BESIII (2)
The rate of weak decay of J/ is at
10-8 level, and the inclusive search
at BESIII may be available:
J/   D*+S X
D*+S  DS+ g (soft g )
D+S p+
K*0K+
KSK+
The sensitivity at BESIII: 10-7 – 10-8

26. LFV at BES III
J/y  e, et, t, the sensitivity can be 10-8 – at BES-III with 1010 J/y events per year
J/y  e- proton +c.c, J/y  m- proton +c.c can also be searched for.

27. Summary Using 58 M BES II data
The invisible decays of / are searched in the process J//
Measured weak decays of J/ in
and
LFV processes J/y  e, et, t
We can look for many rare and forbidden decays of Charm and charmonium, and challenge the SM at BES III

28. Thank You!