New Physics Opportunities in the Charm/Tau Region: The BESIII - Experiment at IHEP/Beijing

Transcription

1 New Physics Opportunities in the Charm/Tau Region: The BESIII - Experiment at IHEP/Beijing Introduction BES3/BEPC2 Physics Programme First Results Summary 1 W.Kühn, Univ. Giessen

2 Charmonium: Positronium of QCD Binding energy [mev] Positronium Mass [MeV] 4100 Charmonium ψ (4040) S S D D2 3 3 D S 2 3 S 2 1 P 2 3 P P D2 2 3 P S S ev Ionization energy 10-4 ev ~ 600 mev e nm e η c(3590) ηc(2980) ψ (3770) 3 D 1 ψ (3686) h c (3525) ψ(3097) 3 P (~ 3940) 2 3 P (~ 3880) 1 3 D (~ 3800) 3 3 P (~ 3800) 0 χ 2(3556) χ1(3510) χ 0(3415) 1 D 2 C 3 D 2 Threshold 1 fm C 2900 W.Kühn, Univ. Giessen Charmonium states are narrow and well separated! 2

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4 Satellite view of BEPCII /BESIII LINAC South BESIII detector 2004: start BEPCII construction 2008: test run of BEPCII 2009-now: BECPII/BESIII data taking 4

5 Beam energy: GeV Design Luminosity: cm -2 s -1 Achieved Luminosity: cm -2 s -1 Optimum energy: 1.89 GeV Energy spread: No. of bunches: 93 Bunch length: 1.5 cm Total current: 0.91 A Circumference: 237m 5

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7 Data samples So far BESIII has collected : 2009: 225 Million J/ψ 2009: 106 Million ψ : 2.9 fb -1 ψ(3770) (3.5 x CLEO-c) - May 2011: 0.48fb MeV: Ds, XYZ spectroscopy Plans for 2012: 1 Billion J/ψ, 700 Million ψ Tau mass scan 7

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9 ψ ψ η χ η ψ 9

10 Motivation: Establish spectrum of light hadrons Search for non-conventional hadrons Understand how hadrons are formed Why at a τ-charm collider? Gluon rich Clean environment J PC filter 10

11 ψ ψ η χ η ψ 11

12 ρπ 12

13 ψ ψ η χ η ψ 13

14 Measurements of the total cross section for e + e annihilation into hadrons are Indispensable input for the determination of the non perturbative hadronic contribution to the running of the QED fine structure constant, An essential input parameter in precision electroweak measurements 14 W.Kühn, Univ. Gießen

15 ψ ψ η χ η ψ 15

16 Leptonic decays of D mesons: Non-perturbative QCD meets CKM physics D + decay constant CKM Matrix Element D + 16

17 Decay constants and Lattice QCD f D σ f Ds 17

18 Search for new physics Energy frontier (LHC) Direct production of new particles Higgs, SUSY etc. Precision frontier (SuperB, Tau/Charm factories, other precision experiments) New physics appears in loops Modified SM decay rates Look at rare or forbidden decay modes Non-SM-CP violation Invisible decays 18

19 Selected results Light hadron spectroscopy Charmonium spectroscopy Open charm production 19

20 Observation of proton-antiproton mass threshold enhancement M pp -2m p (GeV) M=1859 MeV/c 2 Γ < 30 MeV/c 2 (90% CL) PRL 91 (2003) M= MeV/c 2 Γ < 38 MeV/c 2 (90% CL) Chinese Physics C 34, 421 (2010) 20

21 BESIII 21

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23 PWA on the ppbar mass threshold structure in Obviously different line shape of ppbar mass spectrum near threshold from that in J/ψ decays BESIII 23

24 Confirmation of X(1835) and Observation of two new structures PRL 95,262001(2005) BESII J/ψ γη pi + pi - η ηpi+pi - η γrho f1(1510) PRL 106, (2011) new guys! BESIII 24

25 Confirmation of X(1835) and Observation of two new structures Resonance M( MeV/c 2 ) Γ( MeV/c 2 ) Stat.Sig. X(1835) ± ± >20σ X(2120) ± ± σ X(2370) ± ± σ BESIII PWA is needed to understand these structures. X(1835) consistent with

26 What s the nature of these structures? PRD73,014516(2006) Y.Chen et al First time observation of resonant structures in the 2.4 GeV/c 2 region LQCD prediction: lowest pseudoscalar glueball: around 2.4 GeV 0 -+ : 2560(35)(120) 2 ++ : 2390(30)(120) J/ψ-->γppη' decay suitable for observing 0 -+ glueballs. Nature of X(2120)/X(2370) pseudoscalar glueball? η/η excited states? 26

27 EM transition inclusive photon spectrum h BESIII preliminary 27 27

28 Observation of h c (taged and inclusive) 28

29 η C resonance parameters from ψ γη C BESIII preliminary BESIII preliminary KsKpi KKpi 0 pipiη BESIII preliminary BESIII preliminary BESIII preliminary KsK3pi 2K2pipi 0 3(pipi) BESIII preliminary Simultaneous fit with BW by considering the interference between η c and non-η c decays, as well as the energy dependence of phase space: mass: ±0.5 stat ±0.6 sys MeV/c 2 width: 30.5±1.0 stat ±0.9 sys MeV f: 2.35±0.05 stat ±0.04 sys rad f: relative phase between η c decay and non-resonant component at the signal region, assuming non-η c is

30 Comparison of the mass and width for η c The world average in PDG2010 was using earlier results BESIII results include both stat. and syst. errors, which is the most precision measurement: the interference between η c decay and non-resonant contributions is important. 30

31 BESIII Preliminary results on N* baryon in ψ ηpp decay Dalitz plot data Dalitz plot MC fit A full PWA is performed. N(1535) M(pη) M(pp) N(1535) is 1/2 - Mass: Width: Br(ψ' ppη)=(6.6±0.2±0.6) 10-5 Br(ψ' N(1535)p) Br(N(1535) pη PDG2010: (6.0±1.2) c.c.) = 31

32 New results on η 3pi in J/ψ γppp BESIII preliminary BESIII preliminary J/ψ γpi 0 pi 0 pi 0 J/ψ γpi + pi - pi 0 Preliminary results: PDG2010: ( ) 10-3 (2009 CLEO-c) PDG2010: (1.68±0.22) 10-3 (1984: GAM2) 32

33 Observation of η c (2S) in ψ γη c (2S),η c (2S) K s Kp M(η c (2S)) = (3638.5±2.3±1.0) MeV/c 2 N(η c (2S)) = 50.6±9.7 Statistical significance larger than 6.0s! Br(ψ γη c (2S) γkskπ) =(2.98±0.57 stat ±0.48 sys ) Br(η c (2S) KKπ)=(1.9±0.4±1.1)% From BABAR(PRD78,012006) M1 transition Γ(η c (2S)) fixed to 12MeV (world average) Br(ψ γη c (2S)) =(4.7±0.9 stat ±3.0 sys ) 10-4 CLEO-c: < PRD81,052002(2010) Potential model: ( )x10-4 PRL89,162002(2002) 33

34 Evidence for ψ decays into γpi and γη PRL105, (2010) 34

35 PRL105, (2010) Some surprises Q. Zhao, PLB697(2011)52 35

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