EMC in BESIII Experiment

Weiguo LiRepresenting BESIII Collaboration

Calor2010May 10, 2010IHEP, Beijing

1

Outline

BEPCII /BESIII

EMC Design and Construction

EMC Performances

Summary

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BEPC II Storage ringBEPC II Storage ring:: Large angle, double-ring

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RFRF SR

IP

22 mrad

2.5m8ns

1.5cm

0.1cm

Beam energy: 1.0-2.3 GeV

Luminosity: 1×1033 cm-2s-1

Optimum beam energy:

1.89 GeVEnergy spread:

5.16 ×10-4

No. of bunches:93

Bunch length:1.5 cm

Total current:0.91 A

Achieving high lum. with many bunches And low β

Magnet: 1 T Super conductingcurrent 3400 Amp

MDC: small cell & Gas: He/C3H8 (60/40)

σxy=130 µmσp/p = 0.5% @1GeVdE/dx=6%

TOF:σT = 100 ps Barrel

110 ps Endcap

Muon ID: 9 layers RPC8 layers for endcap

EMC: CsI crystal∆E/E = 2.5% @1 GeVσz = 0.6 cm/√E

Data Acquisition:Event rate = 4 kHzTotal data volume ~ 50 MB/s

BES-III

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

Resonance Mass(GeV)CMS

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

Physics Cross Section (nb)

#Nevents/year

J/ψ 3.097 0.6 3400 10 × 109

τ+τ− 3.670 1.0 2.4 12 × 106

DsDs 4.030 0.6 0.32 1.0 × 106

ψ(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 4.170 0.6 1.0 2.0 × 106

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

Nevent/year = σexp ×L× T

Expected Events productions per year at BEPCII

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66

Japan (1)Tokyo Univ.

US (6)Univ. of Hawaii

Univ. of WashingtonCarnegie Mellon Univ.

Univ. of Minnesota Univ. of Rochester Univ. of Indiana

EUROPE (8)Germany: Univ. of Bochum,

Univ. of Giessen, GSIRussia: JINR, Dubna; BINP, Novosibirsk

Italy: Univ. of Torino，Frascati LabNetherland：KVI/Univ. of Groningen

BESIII collaboration: 43 Institutes

China(26)IHEP, CCAST, Shandong Univ., Univ. of Sci. and Tech. of ChinaZhejiang Univ., Huangshan Coll.

Huazhong Normal Univ., Wuhan Univ.Zhengzhou Univ., Henan Normal Univ.

Peking Univ., Tsinghua Univ. ,Zhongshan Univ.,Nankai Univ.

Shanxi Univ., Sichuan UnivHunan Univ., Liaoning Univ.

Nanjing Univ., Nanjing Normal Univ.Guangxi Normal Univ., Guangxi Univ.Hong Univ., Hong Kong Chinese Univ.

Korea (1)Souel Nat. Univ.

Pakistan (1)Univ. of Punjab

~ 300 collaborators

BEPCII Construction and Data TakingDec. 2003, Project approved June 19 2008 first physics collision

July 17, 2009, passed government review 7

So far, peak luminosity achieved ~3.0 *1032cm-2s-1

BESIII reached designed performancesTill now, data taking106M ψ(2S); 220M J/ψ events are obtained;Currently run on psi(3770) with ~ 610 pb-1 so far

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0.51

1.52

2.53

3.5

1-2 1-22 2-11 3-3 3-23 4-12

Peak Lum.

in 2010,

at 1032cm-2s-1

March 25 8:00 – March 26 8:00

• Delivered collision beam for 19.9 hours，• Data taking for 16.8 hours• Online luminosity 12.8pb-1

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Stable data taking, BESIII eff. > 80%

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3-6 3-11 3-16 3-21 3-26 3-31 4-5 4-10 4-150

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5-24 5-26 5-28 5-30 6-1 6-3

Mar. 6 – April 14, 2009 May 24 – June 2, 2009

∼100 M ψ(2S) ∼ 45 pb-1@3.65 GeV

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20

40

60

80

6-12 6-17 6-22 6-27 7-2 7-7 7-12 7-17 7-22 7-27

June 12 – Jul. 28, 2009

∼220 M J/ψ

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01-18 01-25 02-01 02-08 02-15 02-22 03-01 03-08 03-15 03-22 03-29 04-05 04-12 04-19

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01-18 01-25 02-01 02-08 02-15 02-22 03-01 03-08 03-15 03-22 03-29 04-05 04-12 04-19

Jan. 17 – Apr. 12, 2010450 pb-1

MDC, Good performance

Eff.: ~ 98%

Beam related backgrounds

Wire reso. design：130mm

σP=11.0 MeV/cdE/dx design:6%

TOF, Top time resolutionBarrel Double Layer

Z (cm)

Time Resolution (ps)

Time Resolution（ps）

Design Target

Bhabha Dimu

Barrel Single Layer

100~110 98.0 95.3

Barrel Double Layer

80~90 78.9 76.3

Endcap 110~120 136.4 95.0

BESIII CsI(Tl) EMC, Design and Construction

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• 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• Tiled angle: theta ~ 1-3o, phi ~ 1.5o

Energy resolution

Babar: 2.67% @1GeV

BELLE: 2.2% @1GeV

CLEO: 2.2% @1GeV

BESIII: 2.5%@1GeV

Crystal calorimeter without

supporting wall between crystals

Single crystal unit

2 Photodiode + 2 Preamplifier + (1 Amplifier)Photodiode(PD): Hamamatsu S2744-08 (1cm x 2cm)Preamplifier noise: < 1100 e (~220keV)Shaping time of amplifier: 1µs

Crystal Production

Have to check the crystal dimensions, light output, radiation dose sensitivity,

Light output and uniformity along crystalbarrel: 5280 pieces

• By PMT + 137Cs• Requirement: LO > 33%; Uniformity < 7%• Quality control : LO > 35%; Uniformity < 7%

uniformityLight-output

Photo diode ( PDS2744-08,13200) checkout

Measure the dark current, capacitance and quantum efficiency of each PD

There is a LED-optical fiber system to monitor every crystal

during construction and data taking. See Jian Fang’s talk.

Checkout of pre-amplifier , and match two in one crystal to similar gains

The difference between the two preamps in the same crystal should be < 3% .

Quality Control of Crystal Radiation Hardness

• Radiation hardness: after 1000rads radiationdecrease of light out <20%

• 100rads radiation decrease of light out <9%

Sample check Most of crystals’ radiation

hardness is good, some crystals unqualified were rejected

17 pieces of 210 samples have not passed Total we rejected 482

Electronics Design parameters

average noise of 384 channels 973e.

Parameter Values

Number of channels 6,240

System clock 20.8 MHz

L1 trigger latency 6.4 μs

Max single channel hit rate ≤ 1 kHz

Equivalent noise charge (energy) 0.16 fC (200 keV) @80 pF

Integral non-linearity ≤ 1% (before corrections)

Cross talk ≤ 0.3%

Dynamic range 15 bits

Information to trigger Analog sum of 16 channels

Gain adjustment range for triggers ≤ 20 %

EMC Electronics

Q-module

Test ControlFanout

On crystalsBy detector

PreampRange selection

buffers

Main amplifier

L1 Tigger System

CR-(RC)2

10 bitADC

10 bitADC

10 bitADC

T/QInfo

VME

÷2

×2

× 16

Use three 20.8 MHz 10 bit ADCs to cover 15 bits required

dynamic range, and provide 6 bits peaking time

See Jinfan Chang’s talk on BESIII EMC electronics21

　　 Barrel EMC assembly

Installation Barrel and endcapbarrel weight : 54 ton

Moving from stand installing Barrel EMC

Endcap　 assemblyNo gap between crystals

Experience in EMC design and construction

• Insure mechanical stability: calculation; matching drilling of crystal support and frame; support of whole EMC at the bottom; so far so good;• Good signal and noise control: insure good connection of cables and careful shielding and grounding; no crystal is lost so far, channels with only one FED from 2 to < 10 now; low noise, ~ 200 keV;• Co-operate with BEPCII people to control radiation dose to EMC; dose under control;

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Radiation DoseCsI Crystal Calorimeter is the most expensive part of the detector,

According to the design, the allowed radiation dose per year should be less than 200 Rads at crystals, ( at 1000 rads, crystal light should be > 80% of original)

Pin diode can withstand more dose, RadFET has moreDynamic range and comparatively more stable

Results from pin diodes and RadFETs

PIN Diodes6 on east and west sides respectively

Phi angles :30°90°… 330° 1-6 : East; 7-12 : West

Are used for tuning the injection and beam orbit

RadFETs

桶部 端盖 Barrel

Endcap

From RadFET, so far, for ~two years operation, average dose < 100 Rad,From detector calibration, the average drop of light < 3%.

Crystal radiation damage from the offline calibConst

3.7-3.27 Psip

4.2-4.14 Psip

5.25-6.2 3.65GeV

6.7-7.28 Jpsi

Machine study

1.18-3.30 psipp

4.10-4.25 psipp

2009 2010So far acceptable, should be careful at higher beam currents, understand the reasons for some higher light loss ~15% ( radiation damage vs light coupling?).

Changes from offline calib.

Changes from LED

EMC in BESIII triggerTrigger cell, barrel 4x4, endcap 15, thres. at 70-80 MeV; then

form cluster, fully efficient at ~ 200 MeV;

Trigger condition from EMC, Nclus, Etot, ClusBB

Etot_l 50% @ ~ 200MeV; 100%@~400MeV

Etot_m 50% @ ~ 700MeV; 100%@~1000MeV (neutral events)

For Etot_l For Etot_m

Efficiency for trigger conditions for event total energy in EMC

Endcapbk-bk

Charge 1

Charge 2

Barrel bk-bk

Charge 3

Charge 4

Neutral

NLTRK ≥ 1 --------- -------- -------- -------- Y Y Y --------- ----------

NLTRK ≥ 2 --------- Y Y Y Y Y--- -------- -------- Y Y Y ----------

STRK_BB Y Y Y -------- -------- -------- -------- -------- ----------

LTRK_BB --------- -------- -------- Y----Y -------- -------- ----------

NBTOF ≥ 1 --------- -------- -------- Y------ Y Y Y Y Y Y ----------

NBTOF ≥ 2 --------- Y Y Y Y Y--- -------- -------- -------- ----------

NETOF ≥ 1 Y Y Y -------- -------- -------- -------- -------- ----------

BTOF_BB --------- -------- -------- ----- Y -------- -------- ----------

NBCLUS ≥ 1 --------- Y Y Y -------- -------- -------- Y Y Y ----------

NBCLUS ≥ 2 --------- -------- -------- -------- -------- -------- ----------

NECLUS ≥ 1 Y Y Y -------- -------- -------- -------- -------- ----------

NCLUS ≥ 2 --------- -------- -------- -------- -------- -------- Y Y Y

ETOT_L --------- -------- -------- -------- Y Y Y -------- ----------

ETOT_M --------- -------- -------- -------- -------- -------- Y Y Y

Global Trigger tables

Y: 1st data set ψ(2S); Y: 2st data set J/ψ; Y: 3rd data set ψ(3770),

To reduce the trigger rate at ψ(3770) (by a factor ~3), Charge 2 trigger is not used,

still very efficient for hadron events → importance of EMC in trigger

J/ψ data

Etot_M is very efficient for neutral events

EMC calibration and monitoringBhabha events are used for normalizing the crystal gain

Radiative Bhabha and di-photons/π0 are used for energy scale

Correct detector material important for data/MC agreement

LED system is used for monitoring the EMC conditions

Operationally, EMC is on with power all the time, help to

monitor the machine operation and make lum. measurement

easier.

See Liu Chunxiu’s talk on calibration using Bhahba

Bian Jianming’s talk on absolute energy calibration

E5x5 vs. Phi of Bhabha event @ boss6.5.1

Lab

Data(black)

MC(red)

Phi

e5x5

CMS

Data(black)

MC(red)

e5x5

PhiIn lab, calibrate to the MC expected energy

DATA/MC consist with each other both in Lab. and CMS after Bhabha calibration.

Energy peak and resolution in CMS in different runsEnergy peak

Energy resolution

8447(3.686GeV) 9680(3.65GeV) 10138(3.097GeV)

DATA and MC consist very well for Bhabha events,

after the calibration with Bhabha

EMC PerformancesNo channel lost so far;

Low electronic noise;

Energy resolution and position resolution reached

design values;

Gap effect at the boundary of crystals is small;

Timing information is very useful in rejecting background;

Energy reconstruction with TOF information, improve

performance, especially for low energy showers;

Performance reach/exceed designBarrel energy resolution

energy resolution for Bhabha events Position resolution for Bhabha

4.4 mm@1.89 GeV

energy deposit for e+e- γγ

design：2.5%@1GeV

design：6mm/√E

Nice features

Air gap

crystal center

Photon detection: EMC+TOF

Energy resolution in gaps: minimum dead material

Using timing info. to reject bks.

Lowest electronic noise: < 200 KeV

With TOF

Without TOF

EMC energy resolution after energy correction at the boundary of crystals

MC(3.770GeV) digamma bhabhaBefore correction 2.59% 2.40%After correction 2.46% 2.19%

Bhabha data 3.770GeV 3.686GeV 3.097GeV

Before correction

2.57% 2.50% 2.56%

After correction 2.33% 2.27% 2.36%

To be used in the physics analyses

ψ’ γχc1,2 γγJ/ψ γγl+l- (With TOF)

ψ’ γχc1

ψ’ γχc2

Eγ Etof

Eγ with/without TOF

Eγ Etof

Eg with/without TOF

Data/MC differenceEnergy scale: 0.5%Energy resolution: 5%

The tail of the line shape is reduced due to the use ofTOF energy

Line shape have good DATA/MC consistency after using TOF energy

The DATA/MC agreement of TOF Energy indicates thecalibration of TOF energy work well

Energy scale and resolution(With TOF energy)see Miao HE’s talk for details of EMC reconstruction

Fit result of ψ’ γχc2 γ γ J/ψ Fit result of ψ’ γχc1 γ γ J/ψ

Energy scale ~0.5% Energy resolution ~5%Data/MC

Emeasure/Eexp in radative Bhabha(solid-data, circle-MC) Difference in Emeasure/Eexp between DT/MC

Photon efficiency improvement with TOF energy

Solid-Without TOF, circle-With TOF

Photon efficiency increased significantly when E<0.8GeV

For higher energy, the difference is smaller

Detection efficiency improvement

π0 efficiency of ψ’ π0 π0J/ψ with/without TOFMC efficiency improvement

DATA efficiency improvement

~12%

~12%

circle: without TOF energydot: with TOF energy

circle: without TOF energydot: with TOF energy

MC efficiency

DATA efficiency

Mgg (0.12-0.145GeV)

π0 efficiency increase about 12% in low energy range

EMC is well understood, so the BESIII physics

analyses based on EMC (neutral channels) are published 1st,

ψ(2S)→ γπ0π0 , γηη (η→ γγ , π0 → γγ )

χc2χc2χco

χco

sψ’ γπ0π0

Nχc0 : 17443±167 Nχc2 : 4516±80

ψ’ γηη

Nχc0 : 2132±60 Nχc2 : 386±25

χc2

χc0

χc2

χc0

BR (10-3) χc0 χc2

BESIII 3.23±0.03±0.23±0.14 0.88±0.02±0.06±0.04

PDG08 2. 43±0.20 0.71±0.08π0π0

CLEO-c 2.94±0.07±0.32±0.15 0.68±0.03±0.07±0.05BESIII 3.44±0.10±0.24±0.15 0.65±0.04±0.05±0.03

PDG08 2.4±0.4 <0.5ηη

CLEO-c 3.18±0.13±0.31±0.16 0.51±0.05±0.05±0.03

CLEO-arxiv:0811.0586Phys. Rev. D 81, 052005 (2010)

E1-tagged ψ’ π0hc, hc γηc

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Significance = 18.6σM(hc)=3525.40±0.13MeVN(hc)= 3679±319Γ(hc) = 0.73±0.45MeVχ2/d.o.f = 33.5/36

Breit-Wigner convoluted with a D-Gaussian resolution + bkg.The mass and width of hc are allowed to float. The background is represented by the π0 recoil mass spectrum in the sideband of the E1 photon and the normalization is allowed to float.

π0 recoil mass spectrum in E1-tagged analysis

Inclusive ψ’ π0hc

Significance = 9.5σN(hc) = 10353±1097χ2/d.o.f = 24.5/34

DATA inclusive

The mass and width of hc are fixed to the values obtained from E1-

tagged analysis. The background is parameterized by a 4th-order

Chebychev polynomial, and all of its parameters are allowed to float.

Inclusive π0 recoil mass spectrum in ψ’ decay

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Summary of systematic errors

The total systematic errors are the square root of the sum of all systematic errors squared, at this stage, the systematic errors are somewhat conservative, can be reduced further

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Results Phys.Rev.Lett. 104(2010) 132002

Combine the fully inclusive and E1-tagged analysis, we get:

BESIII CLEO (E1-tagged)

M(hc) 3525.40±0.13±0.18 MeV 3525.35±0.23±0.15 MeV

Γ(hc) 0.73±0.45±0.28 MeV(<1.44MeV at CL=90%)

-

B(ψ’ π0hc) ×B(hc γηc)

(4.58±0.40±0.50) ×10-4

(Γ(hc) float)(4.22±0.44±0.52) ×10-4

(Γ(hc) fixed to 0.9MeV)Br(ψ’ π0hc ) (8.4±1.3±1.0) ×10-4 No measurement

Br(hc γηc) (54.3±6.7±5.2)% No measurement

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SummaryBESIII EMC successfully built with very nice performances

-- all channels working; Low noise; nice energy and position

resolutions;

-- Timing information is useful to reject background

-- EMC is essential in BESIII trigger

Reconstructing energy with TOF information improves the

performances

BESIII EMC has been understood well, physics papers are

published mainly with EMC information

Thanks

π0 DATA/MC in ψ’ π0π0J/ψ with/without TOF energy

π0 shape with/without TOF energy

π0 daughter photon energy π0 daughter photon energy in the TOF

π0 shape with TOF energy

The tail of π0 line shape is reduced after adding the TOF energy in to the shower energy

Novosibirsk function

)22

)*4ln

)4lnsinh(1(lnexp(*)(

2

2

02

tt

mmt

ttAmfNov −

−+−

= σ

A: Normalization factorm0: Peakt: describe asymmetry tails: resolution

Drill holes in the bigger end of crystal

Assembly of the module

Four holes (2.8mm )are drilled on the big end of the crystal The position of holes in different circle are different fixing the aluminum base plate

Two pieces of PDs areglued togetheronto the plastic 1.5mm

Once gluing 80 piece crystal

Drill machine

4 screws to Fixed Al base plate and preamp

LED-fiber monitor

One crystal has one LED-fiberCheck modules quality Monitor Radiation Hardness calibration energy

Scan energy：10MeV-1.5GeVScan rate: 300HzStability：< 1% 10 min/run

Electronics:Control LED-pulse (10 point) Scan address (10) CLK L1

self-trig

before assembly of super module Test each cell by LED-fiber, if light output < 80% of PMT data, it will opened cell to check PD-crystal gluing and preamplifiers and so on.

Int. Dose of Crystals

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1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69

系列1

East endcap barrel

West endcap

The Int.dose at west endcap

is larger than that at east.

Barrel mechanical structure

The container are slat structure and is divided into 60 grid ,each grid have two rows of crystals and one row in Z direction have 44 crystal , in Φ direction are 120 ring

barrel total 44 x 120 = 5280 crystal Mass are 21 tonSince the gap between crystals is hope as small as possibleThe Crystal will be hang up by screwThere are not compartment wall between crystals for calorimeter mechanical support.

Four holes (2.8mm )are drilled on the big end of the crystal The position of holes in different circle are differentfixing the aluminum base plate

Two pieces of PDs areglued togetheronto the plastic 1.5mm

Once gluing 80 piece crystal

Drill machine

4 screws to Fixed Al base plate and preamp

Drill holes in the bigger end of crystal

Assembly of the module