1. Status of BESIII and upgrade of BESIII
Ming Shao / USTC
for the BES Collaboration

2. Outline Commissioning of BEPCII/BESIII
Performance of the BESIII detector
Upgrade of BESIII
Summary

3. BEPC II Storage ring: Large angle, double-ringRF SR RF
Beam energy:
GeV
Luminosity:
1×1033 cm-2s-1
Optimum energy:
1.89 GeV
Energy spread:
5.16 ×10-4
No. of bunches: 93
Bunch length:
1.5 cm
Total current:
0.91 A
SR mode:
2.5 GeV IP

4. Main parameters achieved in collision mode
design
Achieved
BER
BPR
Energy (GeV)
1.89
Beam curr. (mA)
910
650
700
Bunch curr. (mA)
9.8
>10
Bunch number 93
RF voltage
1.5
*ns @1.5MV
0.033
0.032
x*/y* (m)
1.0/0.015
~1.0/0.016
Inj. Rate (mA/min)
200 e-/ 50 e+
>200
>50
Lum. (1033cm-2s-1) 1
0.30

5. CsI(Tl) calorimeter, 2.5%@1GeV
BESIII detector
SC magnet, 1T
Magnet yoke
RPC MUC
TOF, (barrel) 90/ (endcap)110~120ps
Be beam pipe
MDC, 130 mm
CsI(Tl) calorimeter,

6. First collision event on July 19, 2008
14 M y’ events collected in 2008

7. Drift chamber
To measure the momentum of charged particles by their curvature in the magnetic field
7000 Signal wires: 25 mm gold-plated tungsten
22000 Field wires: 110 mm Al
Gas: He + C3H8 (60/40)
Momentum
Babar: ~ 110 mm
BELLE: ~ 130 mm
CLEO: ~ 110 mm
BESIII: ~ 130 mm

8. MDC calibration Reso. 136 mm Eff.: ~ 98% Beam related backgrounds
● Layer 7
● Layer 22
Wire reso.
σP=13.7MeV/c

9. dE/dx resolution  K p
dE/dx reso.: 5.80%

10. BESIII CsI(Tl) crystal calorimeter
To measure the energy of electromagnetic particles
Barrel: 5280 crystals，Endcap: 960 crystals
Crystal: (5.2x 5.2 – 6.4 x 6.4) x 28cm3
Readout: Photodiodes, 1cm2cm,
Energy range：20MeV – 2 GeV
position resolution: 6 1GeV
Tilt angle: theta ~ 1-3o, phi ~ 1.5o
Babar:
BELLE:
CLEO:
BESIII:
Cesium Iodide doped with thallium

11. EMC calibration 4.4 mm Barrel energy resolution
energy deposit for e+e-gg
energy resolution for Bhabha events
Position resolution for Bhabha
4.4 mm

12. PID: TOF system Barrel: 2*88 BC 408, 2.4 m long, 5cm thick
Endcap：2*48 BC 404
PMT: Hamamatzu R5924
experiment
lengt(cm)
Intrinsic resolution
BESIII
240
90 ps
CLEOII
280
139 ps
OBELIX
300
170 ps
BELLE
255
90~100 ps
CDFII
279
100 ps
HARP
160 ps

13. TOF calibration TOF Barrel: 103 ps Design：100~110 ps (single layer)
Endcap TOF：125ps
Design：110~120 ps

14. m system : RPC
9 layer, 2000 m2
Special bakelite plate w/o lineseed oil
4cm strips, channels
Noise less than 0.1 Hz/cm2

15. MUON Chamber
Efficiency
Spatial resolution
Single counting rate

16. BESIII commissioning and data taking milestones
Mar. 2008: first full cosmic-ray event
April 30, 2008: Move the BESIII to IP
July 20, 2008: First e+e- collision event in BESIII
Nov. 2008: ~ 14M (2S) events collected
April 14, ~100M (2S) events collected
May 30, ~42 pb-1 at continuum collected (3.65 GeV)
July 28, ~200M J/ events collected
Peak Nov. 2008: 1.21032cm-2s-1
Peak May 2009: 3.21032cm-2s-1

17. Data accumulated at BESIII
Mar. 6 – April 14
May 24 – June 2
100 M (2S) data
42 pb-1 data
at 3.65 GeV
June 12 – Jul. 28
200 M J/ data

18. Upgrade of BESIII TOF ! ΔT>3.38 σ separation rate >95.4%(2σ)
Current time resolution can separate kaon/pion of <0.95GeV/c in the middle of barrel
We aim at GeV/c

19. Time resolution in BESIII/TOF
Item
Barrel time reso.
Endcap time reso.
Intrinsic time reso. of one TOF layer for 1 GeV muon
80~90 ps
80 ps
Uncertainty from electronics
25 ps
Uncertainty from bunch length
15 mm，35 ps
Uncertainty from bunch time
~20 ps
Uncertainty from Z position
5 mm,25 ps
10 mm,50 ps
Resolution of expected time of flight
30 ps
Total time reso, one layer of TOF for 1 GeV muon
100~110 ps
110~120 ps
Total time reso, double layer of TOF for 1 GeV muon
90 ps
Non TOF ~60ps
Upgrade!
Target: Intrinsic time resolution < 45 ps, Total time resolution < 72 ps, corresponding to a K/pi separation capability up to >1.1 GeV (95%C.L.).

20. TOF Technique - MRPC
A 24 gaps Timing MRPC

21. Time distribution (ps)
Beam Test at T10
Efficiency (%)
Time resolution (ps)
HV (kV)
HV (kV)
Signal width – TOT (ns)
Time distribution (ps)

22. Schematic view of MRPC TOF
endcap
barrel

23. Thank you ! Summary BEPCII achieved a luminosity of 31032cm-2s-1
The performance of the BESIII detector reached expectations
100 M y’ , 200M J/ events have been accumulated; the data quality is good & preliminary results are being obtained
We are expecting exciting physics results
Upgrade of BESIII is undergoing
Thank you !

25. EMC installation

26. MDC and TOF installation

27. Be Beam-pipe installation

28. BESIII moved to IP: precision < 1 mm

29. MDC Data/MC comparison
Detailed simulation:
Resolution/efficiency of each cell as a function of drift distance, DOCA, Q, HV, Noise, entrance angle, …
Improvements: more data, better understanding, …

30. Very low electronics noise (EMC)

31. EMC Data/MC comparison for Bhabha events
Dots: data
Solid line: MC with background mixing
Dash line/shade: MC without background mixing

32. EMC Data/MC comparison

33. Summary of BESIII performance
● Layer 7
● Layer 22
Wire reso.
Design: 130 mm
dE/dx reso.: 5.80%
Design：6-8%
CsI(Tl) energy reso.
Design: 1 GeV
Bhabha
Barrel TOF reso.: 78 ps
Design：90 ps