Beijing Spectrometer III

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1 Status and Physics Prospects of the Beijing Spectrometer III Niklaus Berger Institute of High Energy Physics Chinese Academy of Sciences 北京谱仪三

2 Overview Our tools: The BEPC II collider The BES III experiment Our goals Light hadron spectroscopy Charmonium physics Charm physics And beyond (Tau physics and QCD) Summary BES III DESY Mai 2008 Niklaus Berger Slide 2

3 The BEPC II Collider 北 BES III DESY Mai 2008 Niklaus Berger Slide 3 京正负电子对撞机二

4 sn2. 5m8The BEPC II Collider Beijing Electron Positron Collider II Double ring, 11 mrad crossing angle Beam energies GeV 93 Bunches Design current: 2 x 0.91 ma Design luminosity at 1.89 GeV: cm -2 s cm22 mrad 1.5cmIP BES III DESY Mai 2008 Niklaus Berger Slide 4

5 BEPC II Commissioning so far Nov Beam was stored in the storage ring Accumulated beam ~ 6 A hrs., beam life time ~ mA. Dec Start to provide SR beams for users Mar First e + e - collision, Lumi ~ cm -2 s -1 June 2007 Provide SR beams for users at 2.5GeV, 200 ma with a lifetime of 5.5 hr Aug Beam current reached 500 ma Sep SCQ moved to the interaction region Jan BEPCII collided 500mA 500mA (in 93 Bunches) Lumi estimated as cm -2 s -1 Mar Beam pipe installed in BES III Mai 2008 BES III moved to interaction region BES III DESY Mai 2008 Niklaus Berger Slide 5

6 BES III DESY Mai 2008 Niklaus Berger Slide 6

7 BES III DESY Mai 2008 Niklaus Berger Slide 7

8 BES III DESY Mai 2008 Niklaus Berger Slide 8

9 BES III DESY Mai 2008 Niklaus Berger Slide 9

10 BES III DESY Mai 2008 Niklaus Berger Slide 10

11 BEPC II charm production Average Luminosity: L = 0.5 Peak Lum.; One year data taking time: T = 10 7 s N event /year = σ exp L T Physics Mass(GeV) Peak Lum. Cross Events/year CMS (10 33 cm -2 s -1 ) Section (nb) J/ψ τ + τ ψ(2s) D 0 D 0 bar D + D DsDs DsDs BES III DESY Mai 2008 Niklaus Berger Slide 11

12 The Beijing Spectrometer III 北京谱仪三 BES III DESY Mai 2008 Niklaus Berger Slide 12

13 The Beijing Spectrometer III Typical small collider experiment with: Drift chamber Time of flight scintillators CsI (Tl) Crystal calorimeter 1 Tesla SC magnet RPC based Muon system BES III DESY Mai 2008 Niklaus Berger Slide 13

Two Be cylinders (0.8 mm and 0.5 mm thick, 0.

component of the BES-III detector Beryllium

14 Two Be cylinders (0.8 mm and 0.5 mm thick, 0.8 mm gap), cooled by paraffin 14.6 μm gold on the inner surface The beam pipe was installed on March 27, 2008, as the last component of the BES-III detector Beryllium Beam Pipe BES III DESY Mai 2008 Niklaus Berger Slide 14

Drift Chamber Measure the momentum of charged particles Design spec: Single wire resolution de/dx resolution. CLEO: ~110 μm, 5.7 % Babar: ~110 μm, 6.2 % Belle: ~130 μm, 5.

15 Drift Chamber Measure the momentum of charged particles Design spec: Single wire resolution de/dx resolution. CLEO: ~110 μm, 5.7 % Babar: ~110 μm, 6.2 % Belle: ~130 μm, 5.7 % BESIII ~120 μm 6 % R in = 63mm; R out = 810mm; length = 2400 mm 7000 Signal wires: 25μm gold-plated tungsten (3% Rhenium) Field wires: 110 mm Al Gas: He + C3H8 (60/40) Momentum resolution@1gev: 0.5% BES III DESY Mai 2008 Niklaus Berger Slide 15

Standalone Cosmic Ray Test 800 90 hits dr 25.025 phi0 3.23820 dz -326.564 tanl -0.

=80 resrevoverall Entries 781908 Mean -2.772e-05 RMS 0.123 χ 2 / ndf 2234 / 154 Prob 0 p0 5551 ± 24.2 p1 9.471e-05 ± 1.416e-04 p2 0.

16 Standalone Cosmic Ray Test hits dr phi dz tanl 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) BES III DESY Mai 2008 Niklaus Berger Slide 16

17 Time Of Flight System Double layers at barrel of 88 counters/layer, readout at both ends High quality plastic scintillator, 2.4 m long, 5 cm thick 100 ps timing, 90 ps for two layers Barrel TOF Endcap TOF Endcaps each have 48 counters, read out at the inner end, one layer 120 ps timing BES III DESY Mai 2008 Niklaus Berger Slide 17

18 BES III DESY Mai 2008 Niklaus Berger Slide 18

19 BES III DESY Mai 2008 Niklaus Berger Slide 19

Crystal Calorimeter Measure the energy of electromagnetic particles CsI (Tl) Barrel: 5280 crystals, Endcap: 960 crystals Crystal: (5.2 x 5.2 6.4 x 6.

20 Crystal Calorimeter Measure the energy of electromagnetic particles CsI (Tl) Barrel: 5280 crystals, Endcap: 960 crystals Crystal: (5.2 x x 6.4) x 28 cm 3 Readout: ~13000 Photodiodes, 1 cm 2 cm, Energy range:20mev 2 GeV position resolution: 6 mm@1gev BES III DESY Mai 2008 Niklaus Berger Slide 20

Crystal Calorimeter Performance BES II: 22% @1GeV Babar: 2.67% @1GeV BELLE: 2.

21 Crystal Calorimeter Performance BES II: Babar: BELLE: CLEO: BESIII: BES III DESY Mai 2008 Niklaus Berger Slide 21

22 Barrel Calorimeter Installation BES III DESY Mai 2008 Niklaus Berger Slide 22

23 BES III DESY Mai 2008 Niklaus Berger Slide 23

24 9 layer, 2000 m 2 Special bakelite plate without linseed oil 4cm strips, ~10000 channels Noise less than 0.1 Hz/cm 2 Muon System 螺栓 M36 螺栓 M20 BES III DESY Mai 2008 Niklaus Berger Slide 24

25 BES III DESY Mai 2008 Niklaus Berger Slide 25

Magnet Magnet reached 1 Tesla (3364 A) in September 2006 Mapped the field including BEPC SC quadrupoles in August 2007 x 10 4 1.025 1.02 1.

26 Magnet Magnet reached 1 Tesla (3364 A) in September 2006 Mapped the field including BEPC SC quadrupoles in August 2007 x Bz (Gauss) Z (mm) phi (degree) BES III DESY Mai 2008 Niklaus Berger Slide 26

27 Data Acquisition Capable of 4000 Hz ~ 50 MB/s 10x B-Factories 1000x BES II At the edge of what is possible via VME BES III DESY Mai 2008 Niklaus Berger Slide 27

28 Cosmics BES III DESY Mai 2008 Niklaus Berger Slide 28

29 The BES III Collaboration USA (7) University of Hawaii University of Washington Carnegie Mellon University Univ. of Florida Univ. of Minnesota Rensselaer Polytechnic Institute University of Rochester Spectators : four institutes from Italy Totally 37 institutions now Europe (5) GSI, Germany University of Bochum, Germany University of Giessen, Germany JINR, Dubna, Russia Budker institute of Nuclear Physics Japan (1) Russia China (24) Tokyo University IHEP, CCAST, GUCAS, Univ. of Sci. and Tech. of China Shandong Univ., Zhejiang Univ. 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 Kong University Chinese Univ. of Hong Kong BES III DESY Mai 2008 Niklaus Berger Slide 29

30 BES III DESY Mai 2008 Light Niklaus Berger Hadron Spectroscopy Slide 30

31 Light Hadron Spectroscopy J/ψs are probably enough to answer most questions about light hadron spectroscopy Meson spectroscopy Baryon spectroscopy Glueballs and hybrids Checks on all the things seen with BES II Y(2175) in J/ψ ηφf 0 (980) X(1580) in J/ψ K + K - π 0 X(1860) in J/ψ γpp X(1835) in J/ψ γη π + π - Partial wave analyses BES III DESY Mai 2008 Niklaus Berger Slide 31

$fractions allows to estimate glue$

32 Glueballs Lightest glueball predicted by lattice at ~ 1710 MeV Scalar state Expected to mix with qqbar f 0 states Glueballs Indeed: Find three f 0 states nearby (two expected from qqbar) Study of decay branching fractions allows to estimate glue component BES III DESY Mai 2008 Niklaus Berger Slide 32

33 However: Resonances concerned are mostly broad Large non-scalar contributions Partial Wave Analysis Take into account angular dependences and interference by performing a partial wave analysis Very powerful tool, especially with large statistics Computationally extremely expensive Massive parallel calculations using graphics cards (GPU) BES III DESY Mai 2008 Niklaus Berger Slide 33

Euros Recently double precision became available Make use of this: General Purpose Computing on

34 Digression: GPU based computing 3D computer games require lots of manipulations on floating-point 4-vectors Gaming market drives hardware 320 fold parallel processors available for less than 200 Euros Recently double precision became available Make use of this: General Purpose Computing on Graphics Processing Units (GPGPU) Application to PWA at BES BES III DESY Mai 2008 Niklaus Berger Slide 34

35 Partial wave analysis of J/ψ γπ + π - and γπ 0 π 0 f 0(1500)? f 0 (1710)? + J /ψ γπ π Channels fitted in the PWA: M(π + π - ) J 0 / ψ γπ π 0 M(π 0 π 0 ) Phys. Lett. B 642 (2006) 441 BES III DESY Mai 2008 Niklaus Berger Slide 35

36 Partial wave analysis of J/ψ γπ + π - and γπ 0 π 0 PWA components: f 0 (1500) f 0 (1710)? f 0 (2020) f (1270) 2 f ( ) f 2 (2150) f (2050) 4 all 0 ++ all 2 ++ BES III DESY Mai 2008 Niklaus Berger Slide 36

37 X(1860) in J/ψ γpp Enhancement at (below) pp threshold Clarify angular structure Baryonium? Fragmentation? M=1859 MeV/c 2 Γ < 30 MeV/c 2 (90% CL) Phys. Rev. Lett. 91, (2003) BES III DESY Mai 2008 Niklaus Berger Slide 37

38 X(1835) in J/ψ γη π + π -, η ηπ + π - Same resonance as X(1860)? BES III has much improved photon reconstruction BES III MC study, 3x10 9 J/ψs 5.0σ >10σ Phys.Rev.Lett.95:262001,2005 BES III DESY Mai 2008 Niklaus Berger Slide 38

39 Charmonium Physics BES III DESY Mai 2008 Niklaus Berger Slide 39

40 Charmonium Physics Understand charmonium spectroscopy and charmonium decay dynamics Hadronic transition (54%) Radiative transition (28%) Study of spin-singlets (h c, η c, η c ) Hadronic decays (15%) Leptonic decays (2%) Radiative decays (2%) ψ(2s) events /year at BES-III BES III DESY Mai 2008 Niklaus Berger Slide 40

41 Charmonium Physics at BES III Mass, width, non-dd decays & Γ(ππJ/ψ) of the ψ Mass width & other decay modes of the η c Mass of the h c Rel. to χ cn c.o.g. other decay modes M2 components in χ cj γj/ψ? Γ(J/ψ γη c )=? Mass & width of the η c BES III DESY Mai 2008 Niklaus Berger Slide 41

42 η c mass and width Not well understood previous measurements inconsistent May be due to line shape see recent CLEO-c publication BES III DESY Mai 2008 Niklaus Berger Slide 42

43 η c mass and width Only ad-hoc phenomenological model seems to work for lineshape Cleo: arxiv:hep-ex: BES III DESY Mai 2008 Niklaus Berger Slide 43

44 M(J/ψ) - M(η c ) - Lattice S.Choe et al, QCD-TARO hep-lat MeV BES III DESY Mai 2008 Niklaus Berger Slide 44

45 The XYZ states States above D threshold found, which mostly decay to charmonia Other decay modes of the 1 states (need detailed scan) 4008 Are there XYZ states down here that are not seen (because they don t decay to J/ψ or ψ )? Can BESIII see them in η c decay channels? Are there ss versions of the XYZ states (i.e. Y(2175)) to be seen in φ & η final states? BES III DESY Mai 2008 Niklaus Berger Slide 45

46 Scan of ψ(3770) peak BES III DESY Mai 2008 Niklaus Berger Slide 46

47 BES III DESY Mai 2008 Niklaus Berger Charm Physics Slide 47

48 Charm Physics 128 million DD pairs are expected at BES-III with 4 years luminosity. 5 M at CLEO-c until M 700M M 5 M 128M BESII CLEO-c BES-III BaBar Belle ψ(3770) peak Υ(4S) Peak Background free Higher statistics BES III DESY Mai 2008 Niklaus Berger Slide 48

49 Charm physics, CKM and QCD Interplay with B-factories: Constrain CKM with B and K measurements, check with measurements in charm sector Many B measurements depend on lattice QCD calculations of e.g. f D, f Ds BES can measure these decay constants with good precision Check/calibrate the lattice calculations D 0 mixing and possible CP violation in the D system BES III DESY Mai 2008 Niklaus Berger Slide 49

50 D-Meson decay constants test LQCD CLEO-c: 281 pb -1 BES-III reaches 2% with 20 fb -1 ψ(3770). BES III DESY Mai 2008 Niklaus Berger Slide 50

51 Precise determination of f Ds challenge LQCD See Hewett [hep-ph/ ] & Hou, PRD 48, 2342 (1993). H.B.Li,J.H.Zou arxiv: sigma discrepancy between LQCD and experimental determination in the SM. f D /f Ds ratio is especially interesting 3.2% 1.2% 1.0% BES III DESY Mai 2008 Niklaus Berger Slide 51

52 The D-meson unitarity triangle BES III DESY Mai 2008 Niklaus Berger Slide 52

53 The D-meson unitarity triangle BES III DESY Mai 2008 Niklaus Berger Slide 53

54 The D-meson unitarity triangle BES III DESY Mai 2008 Niklaus Berger Slide 54

55 The D-meson unitarity triangle BES III DESY Mai 2008 Niklaus Berger Slide 55

56 BES III DESY Mai 2008 Niklaus Berger Slide 56 Neutral D meson mixing D 0 and D 0 can transform into each other (like Kaons an Bs) The mass eigenstates are With eigenvalues c u c u 0 D 0 D D q D p D D q D p D = + = Γ = Γ = i m i m μ μ , 2, 2 Γ ΔΓ Γ + Γ Γ Γ Δ + m m m m m m + long distance physics (Kaon loop)

57 Quantum Correlation PRD 73, (2006) Asner and Sun I.I.Bigi SLAC report-33, 1989 page 169 (C= 1) e + e ψ(3770) D D Forbidden if no mixing K π + K π + Forbidden if no mixing K l + ν K l + ν Forbidden by CP conservation CP+ CP+ Forbidden by CP Conservation CP CP BES III DESY Mai 2008 Niklaus Berger Slide 57

Mixing Rate R M Sensitivity in 20 fb -1 data at BES-III: R M = x 2 + 2 y 2 = N[( K N[( K ± ± π )( K π )( K ± π )] ± π )] Background estimate done for 20

58 Mixing Rate R M Sensitivity in 20 fb -1 data at BES-III: R M = x y 2 = N[( K N[( K ± ± π )( K π )( K ± π )] ± π )] Background estimate done for 20 fb -1 : 2 events in the signal region due to mis-id. (the mis-id rate for pi as a Kaon is 1%). R M < BES III DESY Mai 2008 Niklaus Berger Slide 58

59 CP violation in the D system CP violation in the mixing CP violation in D decays CP violation in interference All clean ways to probe new physics since the SM predicts an unobservable asymmetry of ~10 4 1% level CPV likely indicates new physics. However: Needs extremely good control of systematic effects at the 10-3 level very challenging! BES III DESY Mai 2008 Niklaus Berger Slide 59

60 Rare and Forbidden Decays BES III DESY Mai 2008 Niklaus Berger Slide 60

61 Rare and forbidden decays Search for New Physics in Charm Sector: Lepton flavour and lepton number violating decays of charmonium and open charm Rare charm decays heavily GIM suppressed: BF(c ull)~10-8 Loops different from B and K systems because c is an up-type quark Weak charmonium decays: J/ψ DX BES almost reaches down to rates predicted in SM Charm Mixing (Large CPV in mixing indicates New Physics) CP Violation - Direct (New Physics could be ~%) BES III DESY Mai 2008 Niklaus Berger Slide 61

62 Lepton flavour violating decays of the J/ψ Lepton flavor violating (LFV) processes are strongly suppressed in the Standard Model by powers of the (small) neutrino masses. Such decays signal new physics. J/ψ eμ, eτ, τμ, the sensitivity can be at BES-III with J/ψ events per year J/ψ e - proton +c.c, J/ψ μ proton +c.c can also be searched for. BESII upper limit BR(J/ψ eμ) < BR(J/ψ eτ) < BR(J/ψ μτ) < with 58M J/ ψ sample BESII PLB561, 49 (2003) PLB598, 172(2004) BES III DESY Mai 2008 Niklaus Berger Slide 62

63 Rare and forbidden charm decays Charm FCNC decays heavily GIM suppressed in SM: Burdman et. al., PRD66(2002) New Physics can contribute in loop, loop is different from B and K mesons Lepton decays: D 0 l + l (l = e,μ); GIM suppressed decays: D (±) 0 M (±) 0 l + l (M is an allowed meson); LFV decays: D 0 e + μ, D (±) 0 M (±) 0 e + μ ; LNV decays: D ± M ± l + l + (l = e, μ; same signed di-lepton); BES III DESY Mai 2008 Niklaus Berger Slide 63

64 Sensitivity to rare and forbidden charm decays 10-8 BES-III(20 fb-1) CLEO-c(1fb-1) BaBar(288fb-1) B( D e e 0 + ) 370 D K0 e μ + B( D e e ) D π e μ D 0 ± μ e D + μ μ B( D B( D e e 0 + ) e e 0 + ) LFV and LNV are smoking guns, any indication of a deviation from zero will indicate New Physics. BES III DESY Mai 2008 Niklaus Berger Slide 64

65 Summary BES III DESY Mai 2008 Niklaus Berger Slide 65

$Many things just skipped Measurement of τ mass and branching fractions requires precise beam energy measurement Precise R measurements, including spectroscopy above DD$

66 Many things just skipped Measurement of τ mass and branching fractions requires precise beam energy measurement Precise R measurements, including spectroscopy above DD threshold Hundreds of branching fraction measurements Studies of invisible decays Upgrades planned: Beam energy Better ToF BES III DESY Mai 2008 Niklaus Berger Slide 66

67 Summary There is a lot of interesting physics at charm energies Many measurements are unique to BES III BES III will contribute to Hadron spectroscopy Charmonium physics Charm physics Tau physics BES III will mostly be systematically limited a lot of work in front of us First beam time from June to end of year First results by next year if things go moderately well, could have the worlds largest J/ψ sample by then BES III DESY Mai 2008 Niklaus Berger Slide 67

68 谢谢大家 Many thanks for slides and advice to Li Haibo, Steve Olsen, Shen Xiaoyan, Sébastien Descotes-Genon, Matthew Shepherd BES III DESY Mai 2008 Niklaus Berger Slide 68

69 In the Tunnel BES III DESY Mai 2008 Niklaus Berger Slide 69

70 BES III DESY Mai 2008 Niklaus Berger Slide 70

71 Search for 1 -+ in J/ψ ρ 0 X, X ηπ 0 M(ηπ 0 ) GeV/c 2 M(ηπ 0 ) GeV/c 2 Requires Partial Wave Analysis BES III DESY Mai 2008 Niklaus Berger Slide 71

72 y CP Sensitivity to y and y CP at BES-III y can be probed with first order sensitivity: Reconstruct K+K- (CP+) decay other side must be D 1 (CP-) n = 2B Γ = 2 B (1 η y) Γ where η = ± 1 for CP= ± KK KK 1 KK n 1 y = 2N KK DD 1 B y CP in semileptonic tag + CP tags: KK Γ(CP+ ) Γ(CP ) = Γ(CP+ ) + Γ(CP ) = y cos φ + x Δ sin φ With 20 fb 1 data at BES-III, and a CP tag rate of 1.1%, the sensitivity to y CP is 0.003, which would be 4.3 σ with the current world average y CP = ( 1.12 ± 0.32)% No CPV in mixing PRD 75, (2007) Cheng, He, Li, Wang and Yang y ycosφ BES III DESY Mai 2008 Niklaus Berger Slide 72 CP

73 Neutral D mixing current state Semileptonic and hadronic D decays R R M M 2 2 '2 x + y x + y = = = (2.1± 1.1) 10 '2 Averaged y CP from KK, ππ lifetime ratio y CP = ( 1.12 ± 0.32)% (3.9 σ) Averaged WS Kπ mixing results (time-dependent): Inconsistent with no-mixing at 3.9σ Averaged mixing results (time-dependent): BES III DESY Mai 2008 Niklaus Berger Slide 73

Strong phase CP even: 0 0 ( D D ) 1 D 1 = + 2 CP odd : 1 D2 = 2 0 0 ( D D ) CP tagged Kπ decay: At BES-III, 20 fb 1

74 Strong phase CP even: 0 0 ( D D ) 1 D 1 = + 2 CP odd : 1 D2 = ( D D ) CP tagged Kπ decay: At BES-III, 20 fb 1 data, the sensitivity: δ (cosδ) = 0.04 Important for unitarity triangle γ BES III DESY Mai 2008 Niklaus Berger Slide 74

75 Rare D decays BES III sensitivities SM ( 10 6 ) RPV ( 10 6 ) Current limit ( 10 6 ) BESIII %CL D + K + μ μ (FOCUS) 10.5 D + π + μ μ (FOCUS) 8.7 D + ρ + μ μ (E653) 24.0 D 0 π 0 μ μ (E653) 12.3 D 0 ρ 0 μ μ (E791) 13.7 D 0 Κ 0 μ μ (E653) 10.6 D + K + e e (CLEO-c) 6.7 D + π + e e (CLEO-c) 5.6 D + ρ + e e D 0 π 0 e e (CLEO-II) 7.9 PRD66(2002) D 0 ρ 0 e e (CLEO-II) 10.3 D 0 K 0 e e (CLEO-II) 7.5 BES III DESY Mai 2008 Niklaus Berger Slide 75

76 LFV and LNV D Decays SM RPV Current limit BESIII %CL LNV LFV D + K μ + μ (653) 10.4 D + π μ + μ (FOCUS) 8.7 D + ρ μ + μ (E653) 19.4 D + Κ e + e (CLEO-c) 6.7 D + π e + e (CLEO-c) 5.6 D + ρ e + e D + K + e μ (E791) 8.3 D + π + e μ (E791) 5.9 D + ρ + e μ D 0 π 0 e μ (CLEO-II) 9.7 D 0 ρ 0 e μ (CLEO-II) 11.0 D 0 Κ 0 e μ (CLEO-II) 9.6 PRD66(2002) BES III DESY Mai 2008 Niklaus Berger Slide 76

BEPC II status and prospects

BEPC II status and prospects Hesheng Chen Institute of High Energy Physics, Beijing Introduction Construction Commissioning Physics at BESIII Summary Beijing Electron Positron Collider (BEPC) at IHEP E