1

EMC in BESIII Experiment

Weiguo Li

Representing BESIII Collaboration

Calor2010May 10, 2010

IHEP, Beijing

2

BEPCII /BESIII

EMC Design and Construction

EMC Performances

Summary

Outline

3

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

IP

22 m

rad

2. 5m8ns

1. 5cm

0.1cm

Beam energy: 1.0-2.3 GeVLuminosity: 1×1033 cm-2s-1

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

No. of bunches: 93Bunch length: 1.5 cmTotal current: 0.91 AAchieving high lum. with many bunches And low

4

Magnet: 1 T Super conducting current 3400 Amp

MDC: small cell & Gas: He/C3H8 (60/40) xy=130 m p/p = 0.5% @1GeV dE/dx=6%

TOF: T = 100 ps Barrel 110 ps Endcap

Muon ID: 9 layers RPC 8 layers for endcap

EMC: CsI crystal E/E = 2.5% @1 GeV z = 0.6 cm/E

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

BES-III

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

5

Resonance

Mass(GeV)CMS

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

Physics Cross

Section (nb)

#Nevents/year

J/ 3.097 0.6 3400 10 109

3.670 1.0 2.4 12 106

DsDs 4.030 0.6 0.32 1.0 106

(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 = 107s

Nevent/year = exp L T

Expected Events productions per year at BEPCII

6

6

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 China

Zhejiang 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

7

BEPCII Construction and Data Taking

Dec. 2003, Project approved

June 19 2008

first physics collision

July 17, 2009, passed government review

8

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

BESIII reached designed performances

Till now, data taking

106M (2S); 220M J/ events are obtained;

Currently run on psi(3770)

with ~ 610 pb-1 so far

0.51

1.52

2.53

3.5

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

Luminosity（E32/cm2/s）

Peak Lum.

in 2010,

at 1032cm-2s-1

9

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

10

0

30

60

90

120

150

180

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

10

20

30

40

50

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

0

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

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

100 M (2S)

220 M J/

45 pb-1@3.65 GeV

Stable data taking, BESIII eff. > 80%

0

50

100

150

200

250

300

350

400

450

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, 2010

450 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

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BESIII CsI(Tl) EMC, Design and Construction

• 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, 1cm2cm,

• 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: 1s

Crystal Production

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

Light output and uniformity along crystal barrel: 5280 pieces

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

uniformity Light-output

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

Photo diode ( PDS2744-08,13200) checkout

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 radiation decrease of light out <20%

• 100rads radiation decrease of light out <9%

17 pieces of 210 samples

have not passed

Total we rejected 482

Sample check Most of crystals’ radiation

hardness is good, some crystals unqualified were rejected

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 %

Electronics Design parameters

average noise of 384 channels 973e.

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  Q-module

Test ControlFanout

On crystals

By detector

Preamp

Range selection

buffers

Main amplifier

L1 Tigger System

CR-(RC)2

10 bitADC

10 bitADC

10 bitADC

T/QInfo

VME

2

2

16

EMC Electronics

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 electronics

　　 Barrel EMC assembly

Installation Barrel and endcap barrel weight : 54 ton

No gap between crystals

Moving from stand installing Barrel EMC

Endcap assembly

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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;

Radiation Dose

CsI 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 more

Dynamic range and comparatively more stable

Results from pin diodes and RadFETs

Phi angles :30°90°… 330°

PIN Diodes6 on east and west sides respectively

1-6 : East; 7-12 : West

Are used for tuning the injection and beam orbit

桶部 端盖

RadFETs

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 2010

So 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 LED

Changes from offline calib.

EMC in BESIII trigger

Trigger 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)

Efficiency for trigger conditions for event total energy in EMC

For Etot_l For Etot_m

Endcap

bk-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

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

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

still very efficient for hadron events importance of EMC in trigger

Global Trigger tables

Etot_M is very efficient for neutral events

J/ data

EMC calibration and monitoring

Bhabha events are used for normalizing the crystal gain

Radiative Bhabha and di-photons/0 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

e5

x5

CMS

Data(black)

MC(red)

e5

x5

Phi

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

In lab, calibrate to the MC expected energy

Energy peak and resolution in CMS in different runs

8447(3.686GeV) 9680(3.65GeV)

10138(3.097GeV)

DATA and MC consist very well for Bhabha events,

after the calibration with Bhabha

Energy peak

Energy resolution

EMC Performances

No 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-

design ：2.5%@1GeV

design ： 6mm/E

Nice features

Air gapcrystal 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

Bhabha data 3.770GeV 3.686GeV 3.097GeV

Before correction

2.57% 2.50% 2.56%

After correction 2.33% 2.27% 2.36%

MC(3.770GeV) digamma bhabha

Before correction 2.59% 2.40%

After correction 2.46% 2.19%

To be used in the physics analyses

’ c1,2 J/ l+l- (With TOF)

’c1

’c2

E Etof

E with/without TOF

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

Fit result of ’c2 J/ Fit result of ’ c1 J/

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

Difference in Emeasure/Eexp between DT/MC

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

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

0 efficiency of ’ 0 0J/ with/without TOF

circle: without TOF energydot: with TOF energy

circle: without TOF energydot: with TOF energy

MC efficiency

DATA efficiency

MC efficiency improvement

DATA efficiency improvement

~12%

~12%

Mgg (0.12-0.145GeV)

0 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,

BR (10-3) c0 c2

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

PDG08 2. 43±0.20 0.71±0.08

CLEO-c 2.94±0.07±0.32±0.15 0.68±0.03±0.07±0.05

BESIII 3.44±0.10±0.24±0.15 0.65±0.04±0.05±0.03

PDG08 2.4±0.4 <0.5

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

CLEO-arxiv:0811.0586

(2S)→ 00 , → , 0 →

c2

c2co

co

Phys. Rev. D 81, 052005 (2010)

s’00

Nc0 : 17443±167 Nc2 : 4516±80

’

Nc0 : 2132±60 Nc2 : 386±25

c2

c0

c2

c0

47

Significance = 18.6M(hc)=3525.40±0.13MeV

N(hc)= 3679±319

(hc) = 0.73±0.45MeV

2/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 recoil mass spectrum in the sideband of the E1

photon and the normalization is allowed to float.

E1-tagged ’hc, hcc

0 recoil mass spectrum in E1-tagged analysis

48

Significance = 9.5

N(hc) = 10353±1097

2/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 ’hc

Inclusive 0 recoil mass spectrum in ’ decay

49

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

Summary of systematic errors

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

BESIII CLEO (E1-tagged)

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

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

-

B(’hc) ×B(hcc)

(4.58±0.40±0.50) ×10-4

((hc) float)

(4.22±0.44±0.52) ×10-4

((hc) fixed to 0.9MeV)

Br(’hc ) (8.4±1.3±1.0) ×10-4 No measurement

Br(hcc) (54.3±6.7±5.2)% No measurement

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

Summary BESIII 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

shape with/without TOF energy

daughter photon energy daughter photon energy in the TOF

shape with TOF energy

DATA/MC in ’J/ with/without TOF energy

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

Novosibirsk function

)22

)*4ln

)4lnsinh(1(ln

exp(*)(2

2

02

t

t

mm

t

tt

AmfNov

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

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 are glued together onto 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

LED-fiber monitor

One crystal has one LED-fiber

Check modules quality

Monitor Radiation Hardness

calibration energy Scan energy ： 10MeV-1.5GeV Scan rate: 300Hz Stability ： < 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

0

100

200

300

400

500

600

700

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

1系列

East endcap barrel

West endcap

The Int.dose at west endcap

is larger than that at east.