Status of BESIII

Weidong Li

IHEP, CAS, Beijing

Nanchang

17th April, 2010

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RFRF SR

IP

22 m

rad

2. 5m8ns

1. 5cm

0.1cm

Beam energy: 1.0-2.3 GeVLuminosity: 3~10×1032 cm-2s-1

Optimum energy: 1.89 GeVEnergy spread: 5.16 ×10-4

No. of bunches: 93Bunch length: 1.5 cmTotal current: 0.91 ASR mode: 0.25A @ 2.5 GeV

BEPCII Storage Ring

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BESIII Detector

μCounter

8- 9 layers

R=1.4 cm~1.7 cm

　 　

Time Of Flight(TOF)T (ps)=100-120　ps　Barrel

　　　　　　　110-130　ps　endcap

Mian Drift Chamber(MDC)

P/P (0/0) = 0.5-0.7 %

(1 GeV ）dE/dx (

0/0) = 6-8%

EMC ： E/√E(0/0) = 2.5 -3 % (1 GeV)

z,(cm) = 0.5cm-0.7 cm/√E

Super-conducting magnet1.0 tesla

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BEPCII/BESIII Commissioning milestones Oct. 25-31, 2007: accumulation of electron/positron beams Nov. 18, 2007: first e+e- collision without BESIII detectorMar. 2008: Collision at 500 mA × 500 mA, Lumi.: 1 ×1032 cm-2s-1

Mar. 2008: first full cosmic-ray event in BESIIIApril 30, 2008: Move the BESIII to IPJuly 18, 2008: First e+e- collision event in BESIIINov. 2008: Lumi. ~1.2 1032cm-2s-1, BESIII ~ 10M (2S) eventsApril 14, 2009 BESIII ~100M (2S) events (~40 days)May 14, 2009 BEPCII Lumi. ~ 3 1032cm-2s-1

July 28th, 2009 BESIII ~200M J/ Ψevents (41 days)

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First Hadronic Event

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Main Drift Chamber (MDC)

43 (8+12+16+7) sense wire layers group to 11 superlayer

Cell is nearly square in shape

cosfrom -0.93 to 0.93

He + C3H8 (60%+40%)

Interaction point

Cosθ=0.83

Cosθ=0.93

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MDC Calibration T0 (Time offset) calibration: T0 is determined cell by cell using the

difference between measurement drift distance and doca (distance of closest approach)

Calibration of Time-to-distance relation (X-T relation)

Use Bhabha events to do initial calibration

Use pion sample to calibrate X-T functions with large entrance angle

Calibration of Q-T function: to calibrate the correlation between timing difference and pulse height of the signalX-T functions of different entrance

angle in layer 40 Q-T function (layer 29)

0 1 /walk p QpT

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= 135 m

P=11.3MeV/c@1.548GeV/c

For Bhabha from 2s) data, spatial resolution is 136m and P is 14.7MeV/c

For Bhabha from J/ data, spatial resolution is 135m and P is 11.3MeV/c

For Bhabha from data, spatial resolution is 138m and P is 15.7MeV/c

Performance from Bhabha events

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RunPea

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Calibration Monitoring

J/ scan

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MDC M.C. Tuning (1)

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MDC M.C. Tuning (2)

eμπp

dEdx Measurement

raw ADC

2 30 4

2 03

( 1) 1( ) { 1 ln[ ( ) ]}

pp

p

p ydEy p p p

dx y y

6% e/πK/π

p/πp/K

3σ separation

resolution for minimum ionization particles

separation power as a function of momentum

ADC comparison betweenADC comparison between MC and dataMC and data

dE/dx energy loss curve y≡βγ=p/m

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Time of Flight

The Geometry of TOF

Measure the time of flight charged particles

Solid coverage

Barrel 0~0.83

End-cap 0.85~0.95

Barrel: 2*88 BC408, 2.4 m long, 5cm thick

Endcap： 2* 48 BC 408

PMT: Hamamatzu R5942

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Time Resolution and Efficiency (1)

BarrelSingle End

BarrelSingle Layer

BarrelDouble Layer

141ps 98ps 79ps

Time Resolution versusTOF Counter Number Barrel Efficiency vs TOF Counter Number

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Endcap

98ps

Time Resolution versusTOF Counter Number

Endcap Efficiency vs TOF Counter Number

Time Resolution and Efficiency (2)

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Kaon and Pion Separation Capability

BarrelDesigned Target

Barrel Data

(0) = 105ps (0) = 94ps@1.0GeV

2(C.L. 95.5%) separation corresponds to ΔT>3.38; The momentum of 2 K/ separation achieved 0.96GeV/c for barrel double layers TOF

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Time resolution and rec. efficiency

Barrel bhabha Barrel pion

Endcap bhabha Endcap bhabha

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TOF Q distribution

Bhabha Sample Dimu Sample

Barrel

Endcap

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EMC Detector Crystal

CsI(Tl)

Front face: ~5×5 cm2

Rear face: ~6.5×6.5 cm2

Length: 28 cm

Geometry 1 barrel + 2 endcaps

Acceptance: 93%Х4π

Total crystals: 6240

Barrel: 44 rings, 120 crystals each ring, No of crystals= 44*120=5280

Endcap: 6 rings in each endcap, No of crystals= 480*2=960

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Energy Resolution in EMC at 1.843GeV

2Gamma　:　　2.7%

Bhabha:　2.4%

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• φ, use digamma

– Δφ = r (|φ1-φ2|-π ), r=distance from EMC shower to z-axis, photon position resolution is Δ /2.

• θ, use bhabha with 0.8<e/kalp<1.0

– Δx=l (θemc-θext ), l=distance from EMC shower to IP

– The error of MDC tracking and track extrapolation is included.

Position resolution (boss6.5.1)

Position correction was not done at Endcap

3.686GeV Bhabha

θ向位置分辨随 θ的变化 Φ向位置分辨随 θ的变化

3.686GeV digamma

1.843GeV位置分辨(boss651

)

Barrel East　Endcap

West　Endcap

MC 4.6mm

5.6mm

5.6mm

Data 4.5mm

6.0mm

5.9mm

MC 4.7mm

6.8mm

6.8mm

Data 5.1mm

7.6mm

7.2mm

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Muon Counter

One barrel (9 layers), two endcaps (8 layers each)

Coverage of the solid angle 0.9(4π)

9152 electronics channels

One dimensional readout

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MUC Performance Operating parameters: HV

7.2±0.2kV, threshold 100mV, gas Ar/F134a/ios-butane=50/42/8

Performance was checked with Dimu events:

σrφ ＝ 14.75 mm

σz ＝ 16.13 mm

Data/MC comparisonData/MC comparison

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BESIII Performance

子探测器 设计指标 测量值

主漂移室

动量分辨（ 1　GeV） 0.5-0.7% 0.58　%

dE/dx分辨 6-8%

6.0%　（ hadron）5.3%　

(Bhabha)

量能器能量分辨（ 1　GeV） 2.5-3% 2.5　%

位置分辨 5-7　mm 6.0　mm

飞行时间 时间分辨

桶部 ( 单层 ) 100-120　ps

98　ps　(Bhabha)

端部（单层） 110-130　ps

98　ps　(dimuon)

子探测器 R=1.4　cm~1.7　cm <　1.7　cm

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Computing and Software Environment Underlying framework

GAUDI (originally developed by LHCb)

Simulation

GEANT4

Other external LIBs:

CERNLIB, CLHEP, ROOT, AIDA, XercesC, GDML …

Database: MySQL

Computer language: C++ (BESII legacy code written in Fortran )

Operation system:

SLC4/ gcc3.4.6

 Ethernet core network system with 10 Gbps bandwidth for both computing and storing data

several disk pools (~500 TB) distributed over around ~40 disk servers for data caching

a mass storage system with a tape library of ~5 PB capacity for storing raw data and reconstructed data.

BESIII Software Framework

PhysicsConst. Svc

Calib.ConstantService

DetectorGeom.Service

Simulation

Calib./Rec.

Analysis

BESIIIOffline

DB

EventDataStore

Raw DataRaw DataCnv

Rec DataCnv

Rec.Data

Event DataEvent Data FlowFlow

Detector DataDetector Data FlowFlow

ExecutionExecution SequenceSequenceNavigation

Svc

MagnetFieldSvc

ParticleProp. Svc

DST DataDSTDataCnv

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BESIII Software Infrastructure

More than 250 BESIII packages, size of source code is ~180 MB

External libraries 2.7 GB

Package version management: CVS

Configuration management: CMT

Automatic software validation

Installation tool: Pacman

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Data Management

Processing history of data files —— keep the related jobs’ information in the database together with the data files’ information

• Files: file location, file type, file size, event type, generated date, generated by which job, events number and file qualities.

• Jobs: the software version, submitted date, the location of its job options and logs.

Other interesting information: Data format vs package version

Run information: trigger/event filter criteria, beam condition……

Calibration constants, dead channels/detection efficiencies….

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Data Production Data reconstruction

Data ψ’ data （ run8093-run9025） Data taken at 3.65GeV (run9613-9779) J/ψ data (run9947-run10878)

Time needed (1000 cores used) 3 days for all ψ’ data 1 days for data @ 3.65 GeV 4 days for all J/ ψ’ data

Data size RAW: 60TB REC: 133TB DST: 14TB

MC data production 300M psip inclusive MC

400M jpsi inclusive MC

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Summary

The BESIII detector reached very good performance

Offline software works well

MC tuning is in progress

Low Pt tracking needs to be improved

We are expecting new physics results.

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