Search for Rare and Forbidden Processes at BES

Xiaobin Ji

Institute of High Energy Physics, CAS

Beyond the Standard Model

Aug. 7 – 11, Beijing

-- Only some selected topics

Focus on the Following Topics

• Invisible decays of mesons

• Weak decays of • Lepton Flavor/baryon number violated

decays

Invisible Quarkonium Decays

Invisible Quarkonium DecaysWith in SM, the invisible quarkonium decays are predicted by: hep-ph/9806487, L.N Chang, O.Lebedlev and J. N. Ng

With 2-3% uncertainty!

One get: Br(Y(1S) ) = 1105

Br(J/ ) = 2.69 108

Theoretical clean process can be used to test model and probe new physics!

New physics may enhance the production rate of the invisible Charmonium decays.

MeV Dark Matter Candidates511KeV emission line from SPI group at INTEGRAL satellite in France

The intrinsic line width is 2.950.5 KeV

The Gamma-ray is centered just at positron mass,They are from the annihilation of positronium in the Galactic center.

P. Jean et alAstron. Asronphys407(2003) L55

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

Dark Matter (Exist?)

drrrrM

r

rGMrv

2)(4)(

,)(

)(

A halo exist, and imply dark matter existence

(1-100)MeV Dark Matter: Has it been detected

If the Dark Matter (DM) annihilation happened in Galactic center 00 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)

New Physics in Heavy QQ Decays

H(QQ) : looking for invisible decay in Y(nS) and (ns) n = 1, 2,3 ; hep-ph/0506151

Br(Y(1S) ) = 0.41% Br(J/ ) = 0.023% Br( ) =0.033%

SM:

Br(Y(1S) ) = 1105

Br(J/ ) = 2.69 108

Search () invisible decay using 58 M J/ data of BES II

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 /

Tag directionMissing direction

No any hit information are required outside of the core of decays.

Results ofJ//, where / invisible

Signal MC 58 M J/

missing momentum distribution

..%90@1069.6)'(

)'(

..%90@1065.1)(

)(

2

3

LCBR

invisibleBR

LCBR

invisibleBR

hep-ex/0607006

Extended ML fit is used

Weak Decay of

search for

Weak decays of J/ at BES II• Kinematically J/ 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 cu FCNC transitions in the Minimal Supersymmetric SM.

Decay modes used in the analysis

Results58 million J/ data at BES-IIAccepted by PLB: hep-ex/0604005

K*

Results

Lepton flavor violating processes in J/ decays

• 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 m0, and mix with each others.

Introduction of LFV

BES II Results

momentum distribution

eeJ ,/ ,/ eJ

BESII upper limit

BR(J/ e) < 1.1106

BR(J/ e) < 8.3106

BR(J/ ) < 2.0106

with 58M J/ sample

BESII PLB561, 49 (2003)PLB598, 172(2004)

Prospects of BES III

Magnet: 1 T Super conducting

MDC: small cell & He gas xy=130 m sp/p = 0.5% @1GeV dE/dx=6%

TOF: T = 100 ps Barrel 110 ps Endcap

Muon ID: 9 layer RPC

EMCAL: CsI crystal E/E = 2.5% @1 GeV z = 0.6 cm/E

Trigger: Tracks & ShowersPipelined; Latency = 6.4 s

Data Acquisition: Event rate = 3 kHz Thruput ~ 50 MB/s

BESIII Detector

The detector is hermetic for neutral and charged particle with excellent resolution ,PID, and large coverage.

Two rings, 93 bunches:

• Luminosity

1033 cm s @1.89GeV

6 1032 cm s @1.55GeV

6 1032 cm s @ 2.1GeV

Resonance Mass(GeV)CMS

Peak Lum.(1033cm-2s-1)

Physics Cross Section (nb)

Nevents/yr

J/ 3.097 0.6 3400 10 109

3.670 1.0 2.4 12 106

(2S) 3.686 1.0 640 3.2 109

D0D0bar 3.770 1.0 3.6 18 106

D+D- 3.770 1.0 2.8 14 106

DsDs 4.030 0.6 0.32 1.0 106

DsDs 4.170 0.6 1.0 2.0 106

Average Lum: L = 0.5×Peak Lum.; One year data taking time: T = 107s

Nevent/year = exp L T

Charm Productions at BEPCII

Huge J/ and (2S) sample at BESIII; Largest D/DS sample near the threshold.

Sensitivities of Charmonium Invisible Decays at BES-III

3X109 2S events per year at BES-III

The sensitivity at BESIII will be 106 107 for J/, C and C Invisible ,

Invisible

Study of invisible decays of , , ’, and in J/ two body decays

The sensitivity at BESIII will be 106 107 for , ’ Invisible ,

10X109 J/ events per year at BES-III

Invisible

Access to Weak J/ Decay at BESIII (1)

• J/ DS (DS*) M (M = , ,,’,K, K*,)

J/ PP

Mode Decay Br(1010)

( 40% )

C = S=+1

(c s )

C=+1,S=0

(c d)

DS+

D0 K0

DS+K

D+

D0 D0 ’ D00

8.74

2.80

0.55

0.55

0.016

0.003

0.055

J/ PV

Mode Decay Br(1010)

( 40% )

C = S=+1

(c s)

C=+1,S=0

(c d)

DS+

D0 K*0

DS+K*

D+

D0 D0 D0

36.30

10.27

2.12

2.20

0.22

0.18

0.65

hep-ph/9801202, K. Sharma

DS*+

R = DS

+

DS*+

R = DS

+ Sensitive to new physics if larger BRs measured.

<

Access to Weak J/ Decay at BESIII (2)

The rate of weak decay of J/ is at

108 level, and the inclusive search

at BESIII may be available:

J/ D*+S X

D*+S DS

+ (soft )

D+S

KSK+The sensitivity at BESIII: 107 – 108

LFV at BES III

• J/ e, e, , the sensitivity can be 10 – 10 at BES-III with 1010 J/ events per year

• J/ e proton +c.c, J/ proton +c.c can also be searched for.

SummaryUsing 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/ e, e, • We can look for many rare and forbidden d

ecays of Charm and charmonium, and challenge the SM at BES III