1. 1 EMC in BESIII Experiment Weiguo Li Representing BESIII Collaboration Calor2010 May 10, 2010 IHEP, Beijing

2. 2  BEPCII /BESIII  EMC Design and Construction  EMC Performances  Summary Outline

3. 3 BEPC II Storage ring: BEPC II Storage ring: Large angle, double-ring RF SR IP Beam energy: 1.0-2.3 GeV Luminosity: 1×10 33 cm -2 s -1 Optimum beam energy: 1.89 GeV Energy 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 

4. 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. 5 ResonanceMass(GeV) CMS Peak Lum. (10 33 cm -2 s -1 ) Physics Cross Section (nb) #Nevents/year J/  3.0970.6340010  10 9     3.6701.02.412  10 6 DsDs4.0300.60.321.0  10 6  (2S)3.6861.06403.2  10 9 D 0 D 0 bar3.7701.03.618  10 6 D+D-D+D- 3.7701.02.814  10 6 DsDs4.1700.61.02.0  10 6 Average Lum: L = 0.5×Peak Lum.; One year data taking: T = 10 7 s N event /year =  exp  L  T Expected Events productions per year at BEPCII

6. 6 6 Japan (1) Tokyo Univ. US (6) Univ. of Hawaii Univ. of Washington Carnegie Mellon Univ. Univ. of Minnesota Univ. of Rochester Univ. of Indiana EUROPE (8) Germany: Univ. of Bochum, Univ. of Giessen, GSI Russia: JINR, Dubna; BINP, Novosibirsk Italy: Univ. of Torino ， Frascati Lab Netherland ： 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 Univ Hunan 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. 7 BEPCII Construction and Data Taking Dec. 2003, Project approved June 19 2008 first physics collision July 17, 2009, passed government review

8. 8 So far, peak luminosity achieved ~3.0 *10 32 cm -2 s -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 Peak Lum. in 2010, at 10 32 cm -2 s -1

9. 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. 10 June 12 – Jul. 28, 2009 Mar. 6 – April 14, 2009May 24 – June 2, 2009  100 M  (2S)  220 M J/   45 pb -1 @3.65 GeV Stable data taking, BESIII eff. > 80% Jan. 17 – Apr. 12, 2010 450 pb -1

11. MDC, Good performance Eff.: ~ 98% Beam related backgrounds Wire reso. design ： 130mm σ P =11.0 MeV/c dE/dx design:6%

12. TOF, Top time resolution Barrel Double Layer Z (cm) Time Resolution (ps) Time Resolution （ ps ） Design Target BhabhaDim u Barrel Single Layer 100~11098.095.3 Barrel Double Layer 80~9078.976.3 Endcap110~120136.495.0

13. 13 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 28cm 3 Readout: ~13000 Photodiodes, 1cm  2cm, Energy range ： 20MeV – 2 GeV position resolution: 6 mm@1GeV Tiled angle: theta ~ 1-3 o, phi ~ 1.5 o 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

14. 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: 1  s

15. Crystal Production Have to check the crystal dimensions, light output, radiation dose sensitivity,

16. Light output and uniformity along crystal barrel: 5280 pieces By PMT + 137 Cs Requirement: LO > 33%; Uniformity < 7% Quality control : LO > 35%; Uniformity < 7% uniformity Light-output

17. 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.

18. 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%.

19. 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

20. ParameterValues Number of channels6,240 System clock20.8 MHz L1 trigger latency6.4 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 range15 bits Information to triggerAnalog sum of 16 channels Gain adjustment range for triggers≤ 20 % Electronics Design parameters average noise of 384 channels 973e.

21. 21 22 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

22. Barrel EMC assembly

23. Installation Barrel and endcap barrel weight : 54 ton No gap between crystals Moving from stand installing Barrel EMC Endcap assembly

24. 24 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;

25. 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

26. Results from pin diodes and RadFETs Phi angles : 30°90°… 330° PIN Diodes 6 on east and west sides respectively 1-6 : East; 7-12 : West Are used for tuning the injection and beam orbit

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

28. 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 20092010 So far acceptable, should be careful at higher beam currents, understand the reasons for some higher light loss ~15% ( radiation damage vs light coupling?).

29. Changes from LED Changes from offline calib.

30. 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

31. Endcap bk-bk Charge 1 Charge 2 Barrel bk-bk Charge 3 Charge 4 Neutral NLTRK  1 ----------------- Y Y Y------------------- NLTRK  2 ---------Y Y YY Y----------- Y Y Y---------- STRK_BBY Y Y-------- ---------- LTRK_BB----------------- Y----Y-------- ---------- NBTOF  1 ----------------- Y------Y Y Y ---------- NBTOF  2 ---------Y Y YY 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: 1 st data set  (2S); Y: 2 st data set J/  ; Y: 3 rd 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

32. Etot_M is very efficient for neutral events J/  data

33. 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

34. E5x5 vs. Phi of Bhabha event @ boss6.5.1 Lab Data(black) MC(red) Phi e5x5 CMS Data(black) MC(red) e5x5 Phi DATA/MC consist with each other both in Lab. and CMS after Bhabha calibration. In lab, calibrate to the MC expected energy

35. 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

36. 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;

37. Performance reach/exceed design Barrel 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

38. 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

39. EMC energy resolution after energy correction at the boundary of crystals Bhabha data3.770GeV3.686GeV3.097GeV Before correction 2.57%2.50%2.56% After correction2.33%2.27%2.36% MC(3.770GeV)digammabhabha Before correction2.59%2.40% After correction2.46%2.19% To be used in the physics analyses

40.  ’   c1,2   J/    l + l - (With TOF)  ’   c1  ’   c2 EE Etof E  with/without TOF EE Etof Eg with/without TOF Data/MC difference Energy scale: 0.5% Energy resolution: 5% The tail of the line shape is reduced due to the use of TOF energy Line shape have good DATA/MC consistency after using TOF energy The DATA/MC agreement of TOF Energy indicates the calibration of TOF energy work well

41. Energy scale ~0.5%Energy resolution ~5% Data/MC Fit result of  ’   c2    J/  Fit result of  ’   c1    J/  E measure /E exp in radative Bhabha (solid-data, circle-MC ) Difference in E measure /E exp between DT/MC Energy scale and resolution(With TOF energy) see Miao HE’s talk for details of EMC reconstruction

42. 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

43. Detection efficiency improvement

44.  0 efficiency of  ’   0  0 J/  with/without TOF circle: without TOF energy dot: with TOF energy circle: without TOF energy dot: with TOF energy MC efficiency DATA efficiency MC efficiency improvement DATA efficiency improvement ~12% M gg (0.12-0.145GeV)  0 efficiency increase about 12% in low energy range

45. EMC is well understood, so the BESIII physics analyses based on EMC (neutral channels) are published 1st,

46. BR (10 -3 )  c0  c2 0000 BESIII3.23±0.03±0.23±0.140.88±0.02±0.06±0.04 PDG08 2. 43±0.200.71±0.08 CLEO-c 2.94±0.07±0.32±0.150.68±0.03±0.07±0.05  BESIII3.44±0.10±0.24±0.150.65±0.04±0.05±0.03 PDG08 2.4±0.4<0.5 CLEO-c 3.18±0.13±0.31±0.160.51±0.05±0.05±0.03 CLEO-arxiv:0811.0586  (2S)→  0  0,   → ,  0 →   c2  co Phys. Rev. D 81, 052005 (2010) s  ’   0  0 N  c0 : 17443±167 N  c2 : 4516±80  ’   N  c0 : 2132±60 N  c2 : 386±25  c2  c0  c2  c0

47. 47 Significance = 18.6  M(h c )=3525.40±0.13MeV N(h c )= 3679±319  (h c ) = 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 h c 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  ’    h c, h c   c  0 recoil mass spectrum in E1-tagged analysis

48. 48 Significance = 9.5  N(h c ) = 10353±1097  2 /d.o.f = 24.5/34 DATA inclusive The mass and width of h c 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  ’    h c Inclusive  0 recoil mass spectrum in  ’ decay

49. 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

50. 50 Results Phys.Rev.Lett. 104(2010) 132002 BESIIICLEO (E1-tagged) M(h c )3525.40±0.13±0.18 MeV3525.35±0.23±0.15 MeV  (hc) 0.73±0.45±0.28 MeV(<1.44MeV at CL=90%) - B(  ’    h c ) ×B(h c   c ) (4.58±0.40±0.50) ×10 -4 (  (h c ) float) (4.22±0.44±0.52) ×10 -4 (  (h c ) fixed to 0.9MeV) Br(  ’    h c ) (8.4±1.3±1.0) ×10 -4 No measurement Br(h c   c ) (54.3±6.7±5.2)%No measurement Combine the fully inclusive and E1-tagged analysis, we get:

51. 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

52. Thanks

53.   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

54. Novosibirsk function A: Normalization factor m 0 : Peak t: describe asymmetry tail s: resolution

55. 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

56. 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.

57. Int. Dose of Crystals East endcap barrel West endcap The Int.dose at west endcap is larger than that at east.