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

BESIII Workshop Summary Fred Harris With help from many speakers IHEP, Beijing, Oct. 15, 2001. I apologize for my primitive slides. I am a beginner with Power Point, and my progress with Power Point in Chinese is slow. Before I begin.

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

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

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

  3. 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.

  4. 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

  5. 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

  6. 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 Ds, fD and fDs;; charmed baryons.

  7. Light quark spectroscopy, mc • 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

  8. 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

  9. 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 MC Decay s L Double PDGCLEOc fb-1 tags (dB/B %) (dB/B%) D0K-p+ 3770 3 53,000 2.40.6 D+  K- p+p+ 3770 3 60,000 7.20.7 Ds fp 4140 3 6,000 251.9 dB/B Includes Stat, sys & bkgd errors CLEO-c sets absolute scale for all heavy quark measurements

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

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

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

  13. CLEO-c Physics Impact (what Snowmass said) • 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) Imagine a World where we have theoretical mastery of non- perturbative QCD at the 2% level Now Theory errors = 2%

  14. CLEO-c Flavor Physics Impact (what Snowmass said) • 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. PDG PDG B Factory Data & CLEO-c Lattice Validation CLEO-c data and LQCD (Snowmass:E2 Working Group)

  15. Particle Energy Single Ring（1.2fb-1） Double Ring (4fb-1) D0 ’’ 7.0106 2.3107 D+ ’’ 5.0106 1.7107 DS 4.14GeV 2.0106 0.72107 +- 3.57GeV 3.67GeV 0.6106 2.9106 0.2107 0.96107 J/ 1.6109 6109 ’ 0.6109 2109 Expected Event Rates/Year at BES III

  16. ψ(2S) Physics • BESII may collect 1.6  107ψ(2S) events. • and BESIII 2  109 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 1P1 search. • cdecays, systematically measure BR • BR uncertainty 10-30% a few % • Upper limits will be improved by two orders

  17. Re-measure R-values in BEPC Energy Range The contribution to the (MZ2) 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

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

  19. 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 than109J/ψand ψ’ events, the upper limits for rare and forbidden decays, • Br measurements can reach the level of 10-6~10-7

  20. 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.

  21. Schematic of BESIII detector

  22. 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

  23. 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 mm2, L~60 cm • Clear fibers: 0.3*0.3 mm2, L~1.4 m • two side readout by APD (Φ3) (below –300) • Signal/noise: <6 p.e.> / <~1p.e.> • ~ 50 m z~ 1mm • Total # of channels: 27 x 8 = 216

  24. 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:C2H6 , or He:C3H8 • 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%

  25. The structure of MDC IV

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

  27. 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 X0: E/E ~ 2.5 % @ 1GeV • Rin ~ 75cm , Lin ~ 200cm cos  = 0.83 • Cut L3 BGO crystals (10752) 22 X0 (24cm) into 13X0 (14cm) + 8.5 X0(9.5cm) • Making new bars of 14 cm by gluing 9.5cm + new crystal of 4.5cm • new BGO crystals needed.

  28. BGO

  29. BGO Summary • A basic design of BEMC is to use L3 BGO crystals after cutting, grinding and polishing, with nearly 13X0 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

  30. 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 00~ 450)

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

  32. CCT Principle & advantages • Cherenkov radiation: • Improve PIDGreater mass, Smaller angle,Longer time • Cheap • Simple

  33. TOF+TOF TOF+CCT Comparison of K/ sep.

  34. Muon Counter • Barrel (L ~ 3.6m ) + Endcap: cos ~ 0.9 • Consist of ~ 12 layers streamer tube or RPC • Rin ~ 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

  35. The Plastic Streamer Tubes (PST) • Larger signal pulse, good signal noise ratio Taking ALEPH m detector as an example • Typical strip signals around 6 mV (at BESIII m 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

  36. Muon acceptance Pion contamination

  37. Superconducting Magnet for BESIII • B: 1 ~ 1.2 T, • L ~ 3.2 m • Rin~ 105 cm, Rout ~ 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.

  38. Superconducting Solenoid Magnet Magnetic Field Design 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. B along Z axis (B0=1T, Poisson method) BESIII Workshop Zian Zhu Beijing, Oct.13,2001

  39. 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 ?

  40. 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

  41. LUM Type IIZero 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 (me/Eb) with cylindrical symmetry, where Eb and me is energy of beam and mass of electron respectively.

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

  43. 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 thefringefield from SCQ to the detector performances

  44. 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, …

  45. 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 is80 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1033, 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.

  46. The principle of BESIII trigger(2) Time Reference Detector 0 s • 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 FEE pipeline Level 1 2.4s Readout buffer switch Ev.Filter Farms Disk BESIII FEE pipeline and Data flow

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

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