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

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

BEPC II Storage ring: Large angle, double-ring RF SR RF Beam energy: 1.0-2.3GeV 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: 0.25A @ 2.5 GeV IP

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

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, 2.5%@1GeV

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

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 resolution@1GeV: Babar: ~ 110 mm BELLE: ~ 130 mm CLEO: ~ 110 mm BESIII: ~ 130 mm

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

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

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: 13000 Photodiodes, 1cm2cm, Energy range：20MeV – 2 GeV position resolution: 6 mm @ 1GeV Tilt angle: theta ~ 1-3o, phi ~ 1.5o Babar: 2.67%@1GeV BELLE: 2.2% @1GeV CLEO: 2.2% @1GeV BESIII: 2.5%@1GeV Cesium Iodide doped with thallium

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

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 180-250 160 ps

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

m system : RPC 9 layer, 2000 m2 Special bakelite plate w/o lineseed oil 4cm strips, 10000 channels Noise less than 0.1 Hz/cm2

MUON Chamber Efficiency Spatial resolution Single counting rate

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, 2009 ~100M (2S) events collected May 30, 2009 ~42 pb-1 at continuum collected (3.65 GeV) July 28, 2009 ~200M J/ events collected Peak Lumi. @ Nov. 2008: 1.21032cm-2s-1 Peak Lumi. @ May 2009: 3.21032cm-2s-1

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

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 1.1-1.2GeV/c

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.).

TOF Technique - MRPC A 24 gaps Timing MRPC

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

Schematic view of MRPC TOF endcap barrel

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 !

EMC installation

MDC and TOF installation

Be Beam-pipe installation

BESIII moved to IP: precision < 1 mm

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, …

Very low electronics noise (EMC)

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

EMC Data/MC comparison

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: 2.5%@ 1 GeV Bhabha Barrel TOF reso.: 78 ps Design：90 ps