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Status of BESIII Representing BES collaboration Weiguo Li IHEP, CAS liwg@ihep.ac.cn ICHEP04 Beijing, Aug. 18, 2004

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BEPCII/BESIII Project BESIII Design and Current Status Schedule and Collaboration Summary

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BEPCII/BESIII Project Covered by Zhang Chuang in this session Two rings

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BEPCII Design Goals

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Physics Channel C. M. Energy (GeV) Peak Lumi. (10 33 cm -2 s -1 ) Cross Section (nb) Events per Year J/ 3.0970.6~3400 10 10 9 3.6701.0~2.4 12 10 6 3.6861.0~640 3.0 10 9 D3.7701.0~5 25 10 6 DsDs 4.0300.6~0.32 1.0 10 6 DsDs 4.1400.6~0.67 2.0 10 6 Expected Number of Events in One Years Running

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BESIII Detector

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systemBES III XY = 130 m MDC P/P = 0.5 %(1 GeV) dE/dx = 6-7 % EMC E/E = 2.5 %(1 GeV) z, = 5-6mm (1 GeV) TOF T = 90-100 ps Barrel 110 ps endcap counter 9- 8 layers Magnet 1.0 tesla BESIII Main Parameters

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Main drift chamber Inner diameter: 63mm; Outer diameter: 810mm; length: 2400 mm;43 sense wire layers. Inner cylinder: 1.2 mm Carbon fiber, outer cylinder: 11 mm CF with 8 windows Outer endplate: 18 mm; stepped section 25mm; Al 7075 6796 Signal wires : 25 m gold-plated tungsten 21884 Field wires: 110 m gold-plated Aluminum Small cell: inner---6*6 mm2, outer--- 8.1*8.1 mm2, Gas: He + C 3 H 8 (60/40) Wire resolution < 130 m Momentum resolution@1GeV: dE/dX resolution: 6-7%.

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Blue/red Stereo wires Black:Axial: 12+7 wires Structure and layer arrangement

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1 Cell structure Drift velocity vs field

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Resolution vs Drift Distance cosmic ray 16.4mm cell 14.0mm cell Primary ionization fluctuations Distortion of field Wire resolution of 130 m is achievable; beam test done at KEK, data is being analyzed; Outer and inner cylinders are ready; Endplates are in fabrication; feed through prototypes are fine;wiring machine will be ready soon;prototype of readout electronics. Wiring will start at the end of 2004

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Time of Flight Counters Barrel 2*88 scintillator bars, BC408, 2.32 m long, 5cm thick Endcap 48+48 scintillator bars resolution 100-110 ps/layer PMT: Hamamatzu R5942 Endcap sideview Barrel mechanical

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Source of errorsBarrel Time resolution Endcap time resolution One layer intrinsic time resolution 80 90ps 80-90ps Bunch time uncertainty 20ps Bunch length uncertainly 15mm 35ps MDC positioning precision 5mm,25ps10mm,50ps Electronics25ps Track length30ps Time walk correction10ps Total resolution for one layer 100 110ps110 120ps K/ separation: 0.8GeV. Factors contribute to the time resolution

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Time of Flight system Beam test finished, intrinsic timing resolution of BC408 reached ~90ps for barrel and ~95ps for endcap, comparing with Eijen 200 scintillators PMT tested in 1T magnetic field Electronics using HPTDC tested, resolution ~ 18 ps Currently under study: reflecting materials for scintillator bars Testing facility for mass production PID with Aerogel Cerenkov counters Start to order PMT and scintillator in 2005

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Beam Test Intrinsic resolution of BC408 and EJ200 BarrelEndcap

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CsI(Tl) EMC 6240 crystals, (5.2x 5.2 6.4 x 6.4) x 28cm 3 PD readout, noise

Light output > 33% of reference crystal ~5000 e/MeV Uniformity < 7% Radiation hardness Light output > 80% after 1krad Crystal size: Lateral, +0 -200 m Crystal quality control

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Coil: Single layer solenoid, steady field Cooling mode: In-direct cooling by two phase flow liquid helium Cable: Pure Al stabilized NbTi/Cu Fabrication technology:Inner winding Cold mass support: GFRP tension rod Thermal shield: Liquid Nitrogen plus multi-layer thermal insulation Flux return: Barrel/End yoke, pole tip BESIII Super-conducting magnet Cryostat Inner radius 1.375m Outer radius1.7m Length3.91m Coil Mean radius1.485m Length3.52m Cable dimension3.7mm*20m m Electrical parameters Central field1.0T Nominal current3250A Inductance2.1H Stored energy9.5MJ Cold mass3.6ton Total Weight14.6ton Radiation thickness2X 0

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BESIII Super-conducting magnet SC cable Hitachi cable Ltd., delivered SC magnet Collaboration with WANG NMR INC., US. Current status Engineer design completed Winding machine ready Supporting cylinder will be ready end of Aug. Engineer design of cryogenics is nearly done Start winding the magnet this Sep. Magnet cooled down summer of 2005, then field mapping

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system : RPC 9 and 8 layers, 2000 m 2 Bakelite, no linseed oil 4cm strips, 10000 channels Production started (endcap) Noise less than 0.04 Hz/cm 2 Covered by ZHANG Jiawen in this session

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Expected Performances Solid angle: 0.89 Barrel: 0.62- 0.77 Position resolution: 1.2 cm Minimum momentum 0.4GeV Efficiency: > 95% Punch-through:

DAQ System data transfer requirements Sub-DetectorChannels Drift Chamber (T+Q)6796+6796 Electromagnetic Calorimeter6240 Time of Flight (T+Q)448+448 Muon Counter9216 Trigger Total~ 30K L1 trigger rate: 4 KHz Event Size: 12 KBytes Bandwidth required after L1: 48 MByte/sec Bandwidth required on tape: 36 MByte/sec > 1000 current BESII system

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DAQ System configuration

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Some tests of power pc

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Beam pipe and shielding Be beam pipe: 30 cm long, 63mm in diameter, 2 layers 10-20 m Gold plating to reduce SR backgrounds HOM power: 200W, SR: < 24 W Liquid cooling channel between walls 20 mm Tungsten shielding

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Beam background: a serious issue 1.89 GeV @ 1 Amp All Cu surfaces

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Total Beam-related Backgrounds Backgrounds are simulated from - Synchrotron Radiation; - Beam-gas; - Touschek effect; - Injection. With some masks and shielding near detector Single rate Max: at MDC 40 K; TOF: 10K Dose/year at endcap EMC Max:~210rad/year, Ave:~ 50rad/year. Should be carefully monitored

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BESIII Offline Software System (BOSS) A Team has been set up, most of the tasks are assigned Completed: Three versions of software Framework Currently based on Gaudi A GEANT4 based MC with all sub-detectors Preliminary reconstruction codes with most sub- detectors Three releases planned before end of 2006 Need more people to work on the reconstruction and prepare for the calibration

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4 - tracks in BESIII p=0.5 -1.5GeV |cos|