Recent BES Results and the BESIII Upgrade

Transcription

1 Recent BES Results and the BESIII Upgrade Menu2007 IKP, Forschungzentrum Juelich, Germany Sept , 2007 Frederick A. Harris Sept. 11, 2007 For the BES Collaboration

2 OUTLINE Introduction BESII physics ψ ττ ψ BB-bar ψ radiative decays J/ψ, ψ(2s) ΛΛπ 0 & ΛΛη J/ψ and ψ (2S) nk 0 S Λ ψ(3770), ψ(4040), ψ(4160), ψ(4415) BESIII TOF calibration system Summary

3 Introduction BES CM Energy ranges from 2 to 5 GeV Luminosity at J/ψ ~ 5 x cm 2 s -1 Detector Performance: Beijing, China BESII A unique e + e - machine in the τ-charm energy region since 1989 until CLEOc.

4 World J/ψ and ψ(2s) Samples ( 10 6 ) BES: J/ψ M ψ(2s) M MarkIII DM2 BESI BESII MKI MKII MKIII CBAL BESI BESII CLEO 2006 Many papers based on these BESII samples.

5 BESII Physics

6 ψ ττ B(ψ ττ) = 2.71 ± 0.43 ± first measured by BESI: [PRD65, (2002)]: According to sequential lepton hypothesis, branching ratios expected to satisfy: BESI:

7 ψ ττ BESII Remeasure with larger sample Measure in ψ ττ (μν τ ν μ )(eν τ ν e ) Characterized by 2 charged tracks; 1 μ and 1 e missing energy and momentum no extra hits in BSC ε = 17.8%

8 BESII ψ ττ Result: B(ψ ττ) = (3.10±0.21±0.38) x 10-3 PRD 74: (2006) Lepton universality is tested in charmonium decays. B ee (10-3 ) B μμ (10-3 ) B ττ / (10-3 ) PDG07 PDG07 BESII 7.43 ± ± ± 1.1

9 ψ BBbar First measurement by BESI, remeasure BR with BESII data sample. ψ ΛΛ pπ ΛΛ-bar - pπ + ψ Σ 0 Σ 0 ΣΣ-bar γpπ - γpπ + ψ Ξ - Ξ + ΞΞ-bar p2π - p2π + ψ pp pp-bar Consistent with 12% rule.

10 MARK-II K*K ρπ

11 ψ BBbar BESII CLEOc comparison BES CLEO pp-bar ΛΛ-bar ΣΣ-bar ΞΞ-bar Consistent with SU(3) symmetry. Reduced Branching Ratios BES R = Br/(π p * /s ½ ), p * is baryon momentum. R s same under SU(3) symmetry. Phys. Lett. B648, 149 (2007)

12 ψ radiative decays Only a few modes measured by BESI ' - γη, γη [PRD58,097101(1998)] -ψ ( 2S ) γ ΚΚ, γ ππ [ PRD67, (2003)] Measure more modes with BESII data. ψ ( 2S ) γ + X X 2 - prong : π prong : 2( π 6 - prong : 3( π π, Κ + + π ), π ), Κ π + + 2( π, pp, ηππ π + Κ Κ π ) Κ +, π Κ + + π pp, 2( K + K ), K S K + π + c. c.

13 First measurements of ψ radiativedecays Expect ~1% BR, but only 0.05% previously observed. ~ 0.1% more observed in this analysis. Mode BR ( 10-5 ) [m<2.9 GeV/c 2 ] γ pp-bar 2.9 ± 0.4 ± 0.4 γη 12.6 ± 2.9 ± 1.5 γ 2(π + π - ) 39.6 ± 2.8 ± 5.0 γ K S K + π - +c.c ± 3.6 ± 3.6 γπ + π - K + K ± 2.7 ± 4.3 γπ + π - ppbar 2.8 ± 1.2 ± 0.7 γ 2(K + K - ) < 4.0 γ 3(π + π - ) < 17 γ 2(π + π - )K + K - < 22 PRL 99, (2007)

14 PRD74, (2006).

15 J/ψ and ψ(2s) ΛΛπ 0 and ΛΛη J/ψ ΛΛπ 0 measured by DM2 and BESI B(J/ψ ΛΛπ 0 ) = (2.2 ± 0.6) x 10-4 PDG isospin violating ψ(2s) ΛΛπ 0 unmeasured J/ψ and ψ(2s) ΛΛη unmeasured isospin conserving Select J/ψ ΛΛπ 0 (p π - )(pπ + )γγ Require: 4C kinematic fit, χ2 < 10 L > 5 mm M(p π) M(Λ) < 10 MeV/c 2 and M(ΛΛ) < 2.8 GeV/c 2 Background J/ψ Σ 0 Σ 0

16 J/ψ and ψ ΛΛπ 0 and ΛΛη J/ψ ΛΛ π 0 : BES finds large background from J/ψ ΣπΛ. Must measure BR for this process. Preliminary Backgrounds biggest from J/ψ ΣπΛ N(J/ψ ΛΛπ 0 ) < 7.0 signal shape Use similar selection for J/ψ ΛΛ η signal shape Clear signal. N(J/ψ ΛΛη) = 44 ± 10

17 J/ψ and ψ ΛΛπ 0 and ΛΛη Preliminary ψ(2s) ΛΛπ 0, ΛΛ η signal shapes No signals seen. First measurement! hep-ex:

18 J/ψ and ψ (2S) nk 0 Λ and c.c S In 2004, BES published a threshold enhancement in J/ψ and ψ(2s) pk - Λ. PR 93: (2004). Also see one in M(KΛ) ψ(2s) pk - Λ M(KΛ) GeV/c 2 J/ψ pk - Λ For J/ψ pk - Λ S wave BW fit: M = 2075 ± 12 ± 5 Mev/c 2 Γ = 90 ± 35 ± 9 Mev/c 2 B(J/ψ K - X) B(X pλ) = (5.9 ± 1.4 ± 2.0) x 10-5

19 J/ψ and ψ (2S) nk 0 Λ and c.c. S Here study: J/ψ nk 0 S Λ + c.c. n π + π - p π + + c.c. Require K 0 S and Λ : M(ππ) M(K 0 S) < 12 MeV/c 2 M(pπ) M(Λ) < 20 MeV/c 2 L xy (Λ) > 5 mm Further: Preliminary χ 2 (1C) < 5 L xy (K 0 S) > 5 mm n signal K 0 SΛ

20 J/ψ and ψ (2S) nk 0 SΛ and c.c. J/ψ nk 0 S Λ + c.c. n π+ π - p π + + c.c. Preliminary See KΛ enhancement consistent with PWA in pkλ. [Int. J. Mod. Phys., A 552, 344 (2005)]. Possible interesting structures. N * s Λ * s Fitting with simple BW: M = 1648 ± 6Mev/c 2 Γ = 61 ± 21 Mev/c 2 (errors stat. only) But no obvious nλ threshold enhancement like in pk Λ. B(J/ψ K S X)B(X nλ +c.c.) < 4.8 x 10-5 (90% CL) Not inconsistent.

21 J/ψ and ψ (2S) nk 0 Λ and c.c. S ψ(2s) nk 0 S Λ + c.c. n π + π - p π + + c.c. use similar selection Preliminary Results B(J/ψ nk 0 SΛ + c.c.) = (6.42 ± 0.20 ± 0.99) x 10-4 B(J/ψ nk 0 SΛ) = (3.09 ± 0.14 ± 0.56) x 10-4 B(J/ψ nk 0 SΛ) = (3.37 ± 0.14 ± 0.45) x 10-4 B(ψ(2S) nk 0 SΛ + c.c.) = (0.77 ± 0.11 ± 0.13) x 10-4 B(J/ψ K 0 SX) B(X nλ + c.c.) < 4.8 x 10-5 (90% CL) Q h = B(J/ψ nk 0 SΛ + c.c.) B(ψ(2S) nk 0 SΛ + c.c.) Signal = (12.0 ± 3.2)% (consistent with 12% rule of pqcd)

22 ψ(3770), ψ(4040), ψ(4160), ψ(4415) In 1998 and 1999, BES scanned 91 energy points between 2 and 5 GeV to determine R. Phys. Rev. Lett. 84, 594 (2000) and 88, , (2002).

23 ψ(3770), ψ(4040), ψ(4160), ψ(4415) Resonant parameters In the calculation of ISR factor (1+δ), the values of resonant parameters in PDG2000 were used. Here we refit to determine parameters of high mass J PC = 1 -- states. Use Breit Wigner amplitudes with arbitrary phase to describe resonances: Allow interferences between resonances.

24 ψ(3770), ψ(4040), ψ(4160), ψ(4415) Use 2 nd order polynomial for charm continuum. (Compare to DASP phenomenological form.) Use potential model variable hadronic width. (Compare with Effective Interaction Theory model.) Must fit using iterative procedure - resonant parameters will influence (1+δ) and then R exp. Other models: The results are not the same, but are consistent within errors. For details, see hep-ex:

25 The new results hep-ex: preliminary

26 The new results Comparison of the updated R value and the old results in Phys. Rev. Lett. 88 (2002) preliminary Differences in R values are due to the updated resonant parameters and initial state radiative correction factor (1+δ obs ). hep-ex:

27 preliminary Resonant parameters

28 BEPCII/BESIII

29 BEPCII: a high luminosity double ring collider SC RF Beam magnets

30 BEPCII Design goal Energy range GeV Optimum energy 1.89 GeV Luminosity 1 x cm -2 s 1.89 GeV Injection Synchrotron mode Full energy injection: GeV Positron injection rate > 50 ma/min GeV Use many bunches and mini-beta.

31 BEPCII Status Nov start commissioning; beam stored in storage ring. June SR radiation for users at 2.5 GeV/c; 200 ma, τ = 5.5 hr. Aug beam current reached 0.5 A. At present: moving SC quads to IR; machine studies to start. BESIII detector to IR in Mar. 2008; commissioning summer 2008.

32 BESIII Detector Muon Counter SC magnet TOF Be beam pipe Drift Chamber CsI(Tl) calorimeter

33 MDC Parameters R inner: 63mm ; R outer: 810mm Length (out.): 2582 mm Inner cylinder: 1.2 mm Carbon fiber Outer cylinder: 11.5 mm CF with 8 windows Sense wire : 25 micron gold-plated tungsten (plus 3%Rhenium ) Layers (Sense wire ): 43 Field wire: 110 micron gold-plated Aluminum Gas: He + C3H8 (60/40) σ x ~ 130 μ m Cell: inner chamber mm σ P outer chamber mm ~ 0.5 P Polar angle: cos θ < 0.83 (all layers) σ de < 0.93 (20 layers) dx ~ 6 % de Expected performance dx

34 MDC construction

35 MDC wiring

36 Cosmic ray test of completed MDC L V T σ=120μm =60, V H T =80 resrevoverall Entries Mean e-05 RMS χ 2 / ndf 2234 / 154 Prob 0 p ± 24.2 p e-05 ± 1.416e-04 p ± p ± 23.5 p ± p ± Residual (mm) resolution 120 μm MDC ready for installation in detector.

37 CsI(Tl) crystal calorimeter Design goals: Energy: 1GeV Spatial: 1GeV Crystals: L = 28 cm (15 X 0 ) Barrel: 5280 w: kg Endcaps: 960 w: 4051 kg Total: 6240 w: 25.6 T

38 Assembly of Barrel EMC Mechanical structure EMC Status: Barrel assembly complete. End cap begun. View from inside Insertion

39 Crucial for particle ID Barrel 50mm x 60mm x 2320 mm (inner layer). BC408 2 layers 88 in each Radius from 810 to 930 mm. Endcap 48 fan shaped pieces each end. BC404 PMT: Hamamatsu R5942 fine mesh TOF TOF IHEP TOF electronics - USTC

40 Superconducting Magnet Coil: single layer solenoid First of its kind built in China. Cooling mode: two phase helium force flow Cryostat Superconductor: Al stabilized NbTi/Cu Winding: inner winding Cold mass support: tension rod Coil Thermal shield: LN 2 shield, MLI Flux return: barrel/end yoke, pole tip Inner radius 1.375m Outer radius 1.7m Length 3.91m Mean radius 1.482m Length 3.52m Cable dimension 3.7mm*20mm Electrical parameters Central field 1.0T Nominal current Inductance Stored energy Cold mass Total Weight 3650A 2H 10MJ 3.6ton 15ton Radiation thickness 2X 0

41 BESIII SC Magnet Progress wiring Thermal insulation assembly transportation installation

42 BESIII SC Magnet Progress Sept. 19, Voltage(V) Time:19:00 VTL1A-VTL2A VTLL1A-VTLL2A VTLL1B-VTLL2B VTLL3A-VTLL4A VTLL3B-VTLL4B VTM6A-VTM1A VTM6A-VTM5A VTM1A-VTM2A VTM3A-VTM4A VTM4A-VTM5A Time:22: Voltage curve shows that the magnet is in super-conducting state. Field mapping of magnet completed. Magnetic field Gauss.

43 Spring 2005: All RPC production, assembly, testing, and installation completed.

44 Physics Topics at BESIII Open charm factory : Absolute BR measurements of D and Ds decays Rare D decay D 0 -D 0 bar mixing CP violation f D+, f Ds form factors in semi-leptonic D decays precise measurement (1.6% stat.) of CKM (Vcd, Vcs) CP violation and strong phase in D Dalitz Decays light meson spectroscopy in D 0 and D + Dalitz Decays.

45 Physics Topics at BESIII Charmonium: J/ψ, ψ(2s), η C (1S), χ C{0,1,2}, η C (2S), h C ( 1 P 1 ), ψ(1d), etc. New Charmonium states above open charm threshold Exotics : hybrids, glueballs, and other exotics in J/ψ and ψ(2s) radiative decays. Baryons and excited baryons in J/ψ and ψ(2s) hadronic decays. Mesons and mixing of quark and gluon in J/ψ and ψ(2s) decays. Electromagnetic form factors and QCD cross section (R values). tau mass and tau physics near the threshold Very rich and interesting energy region.

46 Production Average Lum: L = 0.5 Peak Lum.; One year data taking time: T = 10 7 s N event /year = σ exp L T Resonance Mass(GeV) CMS Peak Lum. (10 33 cm -2 s -1 ) Physics Cross Section (nb) Nevents/yr J/ψ τ ψ(2s) D 0 D 0 bar D + D DsDs DsDs Huge J/ψ and ψ(2s) samples at BESIII

47 BESIII Collaboration Institute of High Energy Physics University of Science and Technology Peking University Tsinghua University Shangdong University Nankai University Central China Normal University University of Anhui University of Zhejiang University of Zhengzhou Nanjing Normal University Nanjing University Shanxi University Sichuan University Henan Normal University University of Hawaii University of Washington University of Tokyo Joint Institute of Nuclear Research, Dubna GSI University of Bochum University of Giessen Need more here!

48 BESIII TOF Monitoring System

49 BESIII TOF Monitoring System Monitor the amplitude and time performance of each channel including PMTs and electronics. Concept: Use fiber cable bundles (2 cables) to distribute light to barrel and endcap TOF counters. Use light splitter to illuminate one bundle at a time. Electronic switch Fiber bundles Laser Diode Light splitter TOF barrel 176 fibers TOF endcap 48 fibers connector Fiber To TOF electronics Beam splitter Ref. PMTs fiber TOF barrel 176 fibers TOF endcap 48 fibers PMT TOF barrel PMT

50 BESIII TOF Monitoring System Use PicoQuant 440M Laser Diode (440 nm). Simple to use and maintain. Long lifetime (6 k hours at full power). Peak power: ~1W Pulse width < 70 ps. Wavelength 440 ± 10 nm. Power stability 1% RMS. 1.5 x 10 8 photons/pulse. PicoQuant LDH-P-440M

51 Fiber Bundle Cables (need 2) Barrel TOF EC TOF

52 Time difference measurement Scheme: LD illuminates common end; measure time difference between reference fiber and all other fibers. Laser diode illuminating common end of bundle through diffuser. Barrel distribution boxes. One set of distribution fibers. Two distribution fibers connected to reference PMTs.

53 Summary Many results from BESII J/ψ and ψ' data sets. Only presented a few. BEPCII/BESIII progressing well. Commissioning in summer Rich physics program after CLEO-c. Complementary to B-factories. Collaborators welcomed!