2. BESIII Workshop Summary Summary Fred Harris With help from many speakers IHEP, Beijing, Oct. 15, 2001

3. I apologize for my primitive slides I am a beginner with Power Point, and my progress with Power Point in Chinese is slow.

4. Before I begin I want to thank all the speakers, subgroup coordinators, organizers, and participants. I think the meeting has been a great success. The BESIII design will be greatly improved.

5. Outline 1. Physics 2. Preliminary Design 3. Changes – no time to include 4. Problems/questions 5. Relationship of CLEOc – BESIII 6. Time Schedule 7. Summary

6. Physics at BEPCII/BESIII Rich source of resonances, charmonium, and charmed mesons Transition between perturbative and non-perturbative QCD Charmonium radiative decays are the best lab to search for glueballs, hybrids, and exotic states

7. Physics to be studied in  -charm region   Search for glueballs, quark-gluon hybrids and exotic states  Charmonium Spectroscopy and decay properties  Precision measurement of R  Tau physics: tau mass, tau-neutrino mass, decay properties, Lorenz structure of charged current, CP violation in tau decays …  Charm physics: including decay properties of D and D s, f D and f Ds; ; charmed baryons.

8.   Light quark spectroscopy, m c  Testing QCD, QCD technologies, CKM parameters  New Physics: rare decays, oscillations, CP violations in c- hadrons  ….. To answer these physics questions, need precision measurements with High statistics data samples Small systematic errors

9. Advantages of Running on Threshold Resonances Charm events produced at threshold are extremely clean Large , low multiplicity Pure initial state: no fragmentation Signal/Background is optimum at threshold Double tag events are pristine –These events are key to making absolute branching fraction measurements Neutrino reconstruction is clean Quantum coherence aids D mixing and CP violation studies

10. Absolute Branching Ratios ~ Zero background in hadronic tag modes *Measure absolute Br (D  X) with double tags Br = # of X/# of D tags # of D's is well determined Double tags are pristine  B/B Includes Stat, sys & bkgd errors Decay  s L Double PDG CLEOc fb-1 tags (  B/B %) (  B/B %) D 0  K -  + 3770 3 53,000 2.4 0.6 D +  K -  +  + 3770 3 60,000 7.2 0.7 D s  4140 3 6,000 25 1.9 CLEO-c sets absolute scale for all heavy quark measurements MC

11. CLEO-c Impact semileptonic dB/B CLEO-c PDG CLEO-c will make significant improvements in the precision with which each absolute charm semileptonic branching ratiois known

12. BaBar 400 fb -1 Current Comparison between B factories & CLEO-C Systematics & Background limited CLEO-c 3 fb -1 Statistics limited abcdefghi

13. Compare to B Factories Systematics & background limited. 2.3% 1.7% 0.7% 1.9% 0.6% 2-2- 0  2% 6 – 9 Statistics limited. UL 14%

14. Crucial Validation of Lattice QCD: Lattice QCD will be able to calculate with accuracies of 1-2%. The CLEO-c decay constant and semileptonic data will provide a “ golden, ” & timely test. QCD & charmonium data provide additional benchmarks. (E2 Snowmass Working Group) CLEO-c Physics Impact (what Snowmass said) Imagine a World where we have theoretical mastery of non- perturbative QCD at the 2% level Now Theory errors = 2%

15. Knowledge of absolute charm branching fractions is now contributing significant errors to measurements involving b ’ s. CLEO-c can also resolve this problem in a timely fashion Improved Knowledge of CKM elements, which is now not very good. CLEO-c Flavor Physics Impact (what Snowmass said) VcdVcsVcbVubVtdVts 7%16%5%25%36%39% 1.7%1.6 % 3% 5% B Factory Data & CLEO-c Lattice Validation (Snowmass:E2 Working Group) CLEO-c data and LQCD PDG

16. Expected Event Rates/Year at BES III ParticleEnergy Single Ring （ 1.2f b -1 ） Double Ring (4f b -1 ) D0D0  ’’ 7.0  10 6 2.3  10 7 D+D+  ’’ 5.0  10 6 1.7  10 7 DSDS 4.14GeV 2.0  10 6 0.72  10 7 +-+- 3.57GeV 3.67GeV 0.6  10 6 2.9  10 6 0.2  10 7 0.96  10 7 J/  1.6  10 9 6  10 9 ’’ 0.6  10 9 2  10 9

17. ψ(2S) Physics BESII may collect 1.6  10 7 ψ(2S) events. and BESIII 2  10 9 ψ(2S) events/year. Hadronic decays, systematic study of decays with better BR measurements, 15% rule, VP, VT and other modes BR uncertainty 10-30%  a few % and 1 P 1 search.  c decays, systematically measure BR BR uncertainty 10-30%  a few % Upper limits will be improved by two orders

18. Re-measure R-values in BEPC Energy Range The contribution to the  (M Z 2 ) from R-value remains to be significant. After R values at lower energy get measured accurately, from VEPP-2M in Novosibirsk and  factory in Frascati (~1%level), it is worth while making the R measurement in BEPC energy range with an uncertainty of ~3%, should check if 1% level is possible? Should try to maintain this possibility in the design of BEPCII. Study of QCD and hadron production in BEPC energy region

19. The Impact of BES’s New R-Values on the SM Fit

20. Searches and Possible New Physics Lepton flavor violating J/ψ decays J/ψ  e , e ,   J/ψ decay to D+X CP violation in J/ψ decays With more than 10 9 J/ψand ψ’ events, the upper limits for rare and forbidden decays, Br measurements can reach the level of 10 -6 ~10 -7

21. BESIII Detector Overview The “straw man” detector uses the retired L3 BGO crystals as the barrel calorimeter. This workshop will help refine our detector greatly. I apologize for not covering everyone’s talk.

22. Schematic of BESIII detector

23. Major Upgrades in BESIII Superconducting magnet Calorimeter: BGO with  E/E ~ 2.5 % @ 1GeV MDC IV: with small cells, Al wires, and He gas Vertex detector: Scintillation fibers for trigger Time-of-flight :  T ~ 65 ps Muon detector New trigger and DAQ system New readout electronics

25. Scintillating fiber for Trigger 1.27 mm or thinner Be beam pipe may be used R ~ 3.5 cm 2 double-layers: one axis layer and one stereo layer Scintillating fiber: 0.3*0.3 mm 2, L~60 cm Clear fibers: 0.3*0.3 mm 2, L~1.4 m two side readout by APD (Φ3) (below –30 0 ) Signal/noise: /   ~ 50  m  z ~ 1mm Total # of channels: 27 x 8 = 216

26. Main Draft Chamber End-plates with stepped shape to provide space for SC quads and reduce background –Inner part: stepped conical shape, cos θ= 0.93 –Outer part: L = 190 cm, cosθ= 0.83 with full tracking volume cell size: ~ 1.4 cm x 1.4 cm Number of layers (cell in R): 36 Gas: He:C 2 H 6, or He:C 3 H 8 Sense wire: 30  m gold-plated W, Field wire: 110  m gold-plated Al Single wire resolution : 130  m Mom. resolution : 0.8 % @ 1GeV &1T, 0.67% @1GeV&1.2T DE/dx resolution: 7%

27. The structure of MDC IV

28. Trackerr simulation of MDC,  pt as a function of pt in % for pion, wire resolution 130  m

29. BGO Barrel Calorimeter To provide minimum space for main draft chamber and TOF and to obtain the necessary solid angle, one must modify L3 BGO crystals, and add new crystals 13 X 0 :  E/E ~ 2.5 % @ 1GeV R in ~ 75cm, L in ~ 200cm cos  = 0.83 Cut L3 BGO crystals (10752) 22 X 0 (24cm) into 13X 0 (14cm) + 8.5 X 0 (9.5cm) Making new bars of 14 cm by gluing 9.5cm + new crystal of 4.5cm new BGO crystals needed.

30. BGO

32. BGO Summary A basic design of BEMC is to use L3 BGO crystals after cutting, grinding and polishing, with nearly 13X 0 in length Building BEMC with a size: R~77cm, L~ 194cm Readout: adopt two PD S2662 in each crystal,total channels: 19360 Single crystal calibration will adopt γ source and Xenon flusher for monitoring MC:  E /E ≤ 3%/√E,  Mπ0 ~ 6 MeV Expected performance:  E /E ≤ 3%/√E,  ,  ≤ 3mm/√E Thanks

33. PID: Time of Flight Counters Double layers TOF: ( or TOF +CCT) plastic scintillator (BC-404) 80 pieces per layer in  R: 66 ~ 75 cm, Thickness 4 cm, length ~ 190 cm Readout both sides by F-PMT Time Resolution ~ 65 ps 2σon k/  separation: 1.1~1.5 GeV/c (for polar angle 0 0 ~ 45 0 )

34. Dimension Length: 1906mm Coverage: ~83% Pieces: 80 /layer Place: Space: 105mm Reserved: 7mm Thickness: 49mm /layer

35. CCT Principle & advantages Cherenkov radiation: Improve PID Greater mass, Smaller angle, Longer time Cheap Simple

36. Comparison of K/  sep. TOF+TOFTOF+CCT

37. Muon Counter Barrel (L ~ 3.6m ) + Endcap: cos  ~ 0.9 Consist of ~ 12 layers streamer tube or RPC R in ~ 145cm (yoke thickness ~40cm) Iron plate thickness: 2-6 cm  counter thickness: ~1.5 cm Readout hits on strips ~3cm total weight of iron: ~400 tons

38. The Plastic Streamer Tubes (PST) Larger signal pulse, good signal noise ratio Taking ALEPH  detector as an example  Typical strip signals around 6 mV (at BESIII  detector, the strips are shorter than ALEPH, so the signal maybe larger than 6 mV )  Rise time 10 ns and width at the base ~ 100ns Have a rather long plateau Stable operation, ALEPH has stop working, however the PST still works very stably More experience At IHEP, Beijing, some people ever made many PSTs for ALEPH

39. Muon acceptance Pion contamination

40. Superconducting Magnet for BESIII B: 1 ~ 1.2 T, L ~ 3.2 m R in ~ 105 cm, R out ~ 145 cm Technically quite demanding for IHEP,no experience before, need collaboration from abroad and other institutes in China, both for coil and cryogenic system. Also the design and manufacture are on critical pass.

41. Superconducting Solenoid Magnet BESIII Workshop Zian Zhu Beijing, Oct.13,2001 The field uniformity and forces on the coil are strongly influenced by the proximity of the iron yoke. We will calculate the field and forces using the ANSYS program. Magnetic Field Design B along Z axis (B0=1T, Poisson method)

42. Luminosity Monitor Because the situation at the IR, the luminosity has to either be located quite far away from the IR (3-5m), or in front of Machine Q magnet, to be designed carefully. Accurate position determination; Multiple detection elements at each side to reduce the variation of luminosity when the beam position shifted BGO crystals ?

43. LUM Type I Extremely Forward Luminosity Monitor The Defining and Complimentary Counter Dimension of θ : Scintillation fiber or Silicon Strips Dimension of φ : Plastic scintillator The Calorimeter BGO / PWO Crystal

44. LUM Type II Zero Degree Luminosity Monitor Luminosity Monitor Based on e － (e ＋ ） single Bremsstrahlung(SB) The photons  are emitted along the e － (e ＋ ) direction within a cone of total aperture of (m e /E b ) with cylindrical symmetry, where E b and m e is energy of beam and mass of electron respectively.

45. The photo-diode Hamamstsu S3584-09 will be coupled through the air light guide and concave mirror to the GSO like the Belle design

46. Interaction Region It is very compact at IR, very close cooperation is needed in the designs of detector and machine components at IR Understand the space sharing, the support, vacuum tight Understand the backgrounds from machine and how to reduce them, - Beam loss calculation (masks) - Synchrotron radiation (masks) - Heating effect (cooling if necessary) Understand the effects of the fringe field from SCQ to the detector performances

48. IR Summary IR design is very preliminary Due to the background issues we must do more detail IR design Many items are not taken into account such as background from the loss particle, vacuum, beam diagnostics, …

49. Trigger 1. Trigger rate estimation (using the same trigger conditions as now) Background rate, with 40 times beam current and half of the beam lifetime, the rough estimation for the background is 80 times the current rate (10-15), or 800-1200 Hz, taking 1500 as a design number Good event rate When leave room for maximum luminosity to be as calculated, 1  10 33, 200 times as current event rate, to be 1500 Hz Cosmic ray background can almost be negligible Total peak trigger rate can be more than 3000 Hz, additional trigger (software) is needed to reduce the event rate to 2000Hz.

50. The principle of BESIII trigger(2) Hardware trigger + software filter FEE signal splitted: trigger + FEE pipeline Trigger pipeline clock 20MHz Level 1(L1): 2.4  s FEE Control Logic checks L1 with pipeline clock L1 YES: moves pipeline data to readout buffer L1 No : –overwritten by new data Detector switch BESIII FEE pipeline and Data flow Level 1 FEE pipeline Readout buffer Farms Disk Time Reference 0 s 2.4  s Ev.Filter

51. Global Trigger Logic 2.4  s Schematic of BES III Trigger VC TOF MDC EMC MU DISC Mu track DISC BTE Sum Hit Count Track Finder Tile Processor Total Ener Sum Hit/Seg Count Track Seg. Finder L0 trigger Logic DAQ RF TTC Tile Sum FEE L1P L0P CLOCK

52. Data Acquisition System Event builder 3000 Hz  6 K bytes ~ 20 Mb/s Event filtering Data storage Run control Online event monitor Slow control Switch network

53. Configuration and Software Structure branch 1branch n

54. On-Line System Tasks Event rate ~2000Hz after L2 filter ~16MBytes/sec to persistent store Event Builder System Transport information from readout crate to Online(L2) farm L2 trigger System Software trigger. Selects events for storage Online System –Run environment monitoring and controlling –Experiment monitoring and controlling –Human interface

55. Offline Computing and Analyses Software Computing, network, data storage, data base, processing management Supporting software package, data offline calibration, event reconstruction, event generators, detector simulation Substantial manpower needed for software Total CPU 36000 MIPS Data storage 500 Tbytes/y on tapes, 24 Tbytes/y on disks Bandwidth for data transfer 100 Mbps

57. Endcap Detector Two possible technologies can be used, 1.CsI crystals as in the detector figure, similar technology as in the barrel, need endcap TOF. 2. Similar technique as KLOE using lead-fiber technique, may not need TOF counters. The first choice is preferred.

58. Subsystem BES III CLEOc Vertex  XY (  m) = 50 ? MDC  XY (  m) = 130 90  P/P ( 0 / 0 ) = 0.8 % 0.35 %  dE/dx ( 0 / 0 ) = 7 % 5.7 % BEMC  E/√E( 0 / 0 ) = 2.5 % 2%  z (cm) = 0.3 cm/ √E ? cm / √E TOF  T (ps) = 65 ps   counter 12 层 (?) Magnet 1.0 tesla BESIII – CLEOc Comparison

59. Concerns and Comments To achieve high precision, need excellent detector to reduce systematic errors. Our design is very preliminary. More detector simulation to achieve design optimization. Is BGO the right solution? Need more simulation to study the physics reach with BESIII. We must compare to CLEOc and B-factory experiments. Compare on key channels – those where BESIII has an advantage over B - factories. Physics group? Is the Pid good enough? Can do DCS decays cleanly? BESIII is comparable to the B-factory experiments is difficulty. We need to borrow as much technology, experience, software, etc. as possible from them and CLEOc.

60. Concerns and Comments (continued) Much more study about the interplay between detector and machine, especially in IR. Instrumentation. Radiation budget? Need 12 layers in muon system? Use for K L catcher? Each system (detector components, DAQ and electronics) needs R&D, prototypes. Test L3 BGO. Need good communication and documentation. Web based. Refine cost and schedule. When to have the next workshop? Need BESIII review panel. When?

61. Major issues related with BESIII design The radius of crystal calorimeter, affecting performance and cost. Possibility of using CsI crystals as EMC. Backgrounds associated with machine operation, the design of interaction regions, vacuum, masks, etc. Critical detector sub-sys. affecting the overall schedule - SC magnet, including magnet supporting structure - EMC calorimeter - Main drift chamber Experienced man power big issue

62. CLEOC CLEOc project has already benefited BEPCII – now 2 ring collider. Collaboration/cooperation between BES and CLEO? BESIII follows CLEOc. BESIII can benefit greatly from CLEOc expertise and experience. How to optimize? BESIII physicists join CLEOc at Cornnell? CLEOc physicists join BESIII? High luminosity tau charm physics after CLEOc. Ideas?

63. Schedule Feasibility Study Report of BEPC II has been submitted to the funding agency. Technical Design Report of BEPC II to be submitted by first half of 2002. Construction started from Summer of 2002 BESII detector moved away Summer of 2004, and the BESIII iron yoke started to be assembled, mapping magnet early 2005 Preliminary date of the machine long shutdown for installation : Spring of 2005 Tuning of Machine : Beginning of 2006 BESIII detector moved to beam line, May 2006 Machine-detector tunning, test run at end of 2006Machine-detector tunning, test run at end of 2006

64. Intl. Cooperation on BEPC II / BES III Intl. cooperation played key role in design, construction and running of BEPC/BES. Intl. cooperation will play key role again in BEPC II / BES III: design, review, key technology, installation, tuning …… Participation of foreign groups is mostly welcomed. BESIII should be an international collaboration.

65. Summary BEPC energy region is rich of physics, a lot of important physics results are expected to be produced from BESIII at BEPCII. Detector design is started, need a lot of detailed work to finish detector design! Very interesting and very challenging project. Thanks