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
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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.
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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
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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
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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 [email protected] 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
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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 [email protected] 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
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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
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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.