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Results from BESII and Prospects at BESIII

Results from BESII and Prospects at BESIII. Weiguo LI (Representing BES Collaboration) Institute of High Energy Physics, Beijing Sep. 3 , 2009, Beijing, China. Outline. Introduction Results from BESII (selected topics) Results on light hadron spectroscopy R measurement

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Results from BESII and Prospects at BESIII

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  1. Results from BESII and Prospects at BESIII Weiguo LI (Representing BES Collaboration) Institute of High Energy Physics, Beijing Sep. 3 , 2009, Beijing, China

  2. Outline Introduction Results from BESII (selected topics) Results on light hadron spectroscopy R measurement Non-DD decays and the line shape of the hadron cross section Physics at BESIII Summary

  3. Beijing Electron Positron Collider (BEPC) at IHEP Linac Storage ring BES BSRF 3

  4. （BEPC/BES） beam energy: 1.0 – 2.3(2.5) GeV Physics goal BES 1-2.3GeV e+ e- collisions produce charmonium states （J/，(2S)， cJand (3770)etc.), charm mesons and  lepton. 4 4

  5. We are unique now in -charm region Physics at BEPC/BES From PDG 5 • In transition region between pQCD and non-pQCD.

  6. Physics Topics at BES • Study of Light hadron spectroscopy • search for non-qqbar or non-qqq states • meson spectroscopy • baryon spectroscopy • Study of the production and decay mechanisms of • charmonium states: J/, (2S), C(1S), C{0,1,2} , • C(2S), hC(1P1), (3770), etc. • New Charmonium states above open charm threshold. • Precise measurement of R values • Precise measurement of CKM matrix • Search for DDbar mixing, CP violation, etc. 6

  7. Study of the spectroscopy – a way of understanding the internal structure glueball spectrum from LQCD • Motivation: • Establish spectrum of light hadrons • Search for non-conventional hadrons • Understand how hadrons are formed • Study chiral symmetry in QCD • Why at a -charm collider ? • Gluon rich • Larger phase space than at higher energies • Clean environment, JPC filter Many results in BESII: ~ 50 publications Much more from BESIII: 100 statistics, 10 g resolution Y. Chen et al., PRD 73 (2006) 014516 7 7

  8. New forms of hadrons • Hadrons consist of 2 or 3 quarks： Naive Quark Model： • QCD predicts the new forms of hadrons: • Multi-quark states：Number of quarks >＝ 4 • Hybrids： qqg，qqqg … • Glueballs： gg， ggg … Meson（ qq ） Baryon（q q q）

  9. Multi-quark states, glueballs and hybrids have been searched for experimentally for a very long time, but none is established. The observation of the new forms of hadrons will be a direct test of QCD. This has been one of the important physics goals for many experiments.

  10. Charmonium physics • Examples of interesting/long standing issues: • rp puzzle • Missing states ? • Mixing states ? • New states above open charm thre.(X,Y,Z,…) • What to study ? • Production, decays, transition, spectrum • For what ? • A lab for pQCD and non-pQCD • Calibrate LQCD • How quarks form a hadron ? • Why at a tau-charm collider ? • A clean environment • Tagging possible • Abundantly produced

  11. R measurement Why precise R important? Essential for precise tests of SM. • the global fit of Higgs mass • anomalous  magnetic moment from g-2 R : one of the most important and fundamental quantities in particle physics. 11

  12. Precise measurement of CKM elements -- Test EW theory CKM matrix elements are fundamental SM parameters that describe the mixing of quark fields due to week interaction. 5% precision 10% precision CKMmatrix Three generations of quark? Unitary matrix? Expect precision < 2% at BESIII Precision of measurement CKM matrix elements --a precise test to SM！ New physics beyond SM? 12

  13. Decays constants vs LQCD 2.3  difference for fDs. Real ? BESIII may resolve this issue, reach the precision of LQCD.

  14. e+e- (3770)  D0D0 CP violation and mixing • CPviolation is regarded as the origin of asymmetry of the matter and anti-matter. • CP violation predicted by theoretical models is not big enough to describe the asymmetry. • CP violation is observed in K and B decays, but has never been in charm sector. 0 0 In SM, the mixing is very small. At BESIII, the sensitivity of the mixing rate:1.5  10-4 mixing : a good place to search for CP violation 14

  15. BESII @ BEPC VC: xy = 100 m TOF: T = 180 ps  counter: r= 3 cm MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.5 %  = 7.9 mr B field: 0.4 T p/p =1.7%(1+p2) z = 3.1 cm 15

  16. BESI: run from 1989-1998 • BESII: run from 1999-2004 L ~ 51030 /cm2s at J/ Ebeam~ 1 – 2.5 GeV BESII data samples 16

  17. A structure at 2175MeV was observed in e+e-   ISR f0(980), e+e- ISR K+K-f0(980) initial state radiation processes Observation of a new 1-- resonance Y(2175) at BaBar Y(2175) 6.2  (1680) Y(2175) Phys. Rev. D 74 (2006) 091103(R) Phys. Rev. D 76 (2007) 012008

  18. BESII: Y(2175) in J/  f0(980) Final states: , K+K-, f0(980)+-   f0(980) Define , , f0(980) signal and sideband regions. Phys. Rev. Lett., 100, 102003 (2008)

  19. A peak around 2175 MeV/c2 is observed in J/  f0(980) 5.5  M =2.186±0.010 GeV/c2 =0.065±0.023 GeV/c2 N events= 5212 M(f0(980)) GeV/c2

  20. BELLE: e+e- ISR  +- 673 fb-1 Φ(1680) Two(+1 for third peak) coherent BW Fit results: M(Φ(1680)) = 1687  21MeV/c2 Γ(Φ(1680)) = 212 29 MeV/c2 M(Y(2175)) = 2133+69-115MeV/c2 Γ(Y(2175))= 169+105-92MeV/c2 One BW interfering with non-resonant 20 Belle: I. Adachi et al., arXiv:0808.0006

  21. What is Y(2175)? Some theoretical interpretations: • A conventional state? • An analog of Y(4260) ( )? • An 4-quark state? More experimental information needed. To understand the nature of Y(2175), we are now working on J/K*K*, , KK, …

  22. BESII: Y(2175) in J/K*0K*0 ? BES II Preliminary  M(K-+) K* M(K+-) M() B(J/K*K*)=(7.70.81.4)10-4 First measured.

  23. K*0K*0invariant mass in J/K*0K*0 BES II Preliminary background 3-body phase space M(K*K*) Upper limit @ 90% C.L. B(J/Y(2175))B(Y(2175)K*K*) < 2.5210-4

  24. The observation of new N* peaks in N*(1520) N*(1535) N*(1650) N*(1675) N*(1680) N*(1440)? ? Missing mass spectrum (GeV/c2) 24

  25. Phys. Rev. Lett. 97 (2006) 062001 N*(2065) BW fit yields: PWA is performed. • well-established N*’s are fixed to PDG values. • for N*(2065), L=1 is much worse than L=0 in the fit. •  1/2+ or 3/2+ (improve log likelihood by 400) • 1/2+ + 3/2+ (improve log likelihood further by 60) 25

  26. BESII: PWA of 0  M2(p0) M

  27. Resonances used in the PWA

  28. Comparison of data with fit results + : data hist.: fit

  29. N(1440), N(1520), N(1535), N(1650), N(1675), N(1680), N(1710) are needed. • Nx(2065) exists in this channel (stat. sig. >>5σ) The spin-parity favors 3/2+ N* M(MeV/c2) (MeV/c2) JP fraction(%) Br (×10-4) N(1440) 1/2+ 9.74~25.93 1.33~3.54 N(1520) 3/2- 2.38~10.92 0.34~1.54 N(1535) 1/2- 6.83~15.58 0.92~2.10 N(1650) 1/2- 6.89~27.94 0.91~3.71 N(1710) 1/2+ 4.17~30.10 0.54~3.86 N(2065) 3/2+ 23.0~41.8 0.91~3.11

  30. Observation of charged  at BESII •  was first found in K scattering data • However, its phase shift is much less than 180o and it cannot be • filled into any nonets of ordinary mesons. • There have been hot debates on the existence of . • In recent years: • FNAL E791 found evidence of neutral  in D+ K-++ • CLEO D0 K-+0 data find no evidence of  • FOCUS data on K+K-++ require K*0 interfere with either a constant amplitude or a broad 0+ resonance in K • BESII observed neutral  in J/  K*0K  KK • neutral  pole:

  31. The existence of charged  is expected ! • CLEO reported the necessity of in • However, no charged  is needed in BABAR data. • Charged  is observed at BESII in • Different parameterizations of  • are tried in PWA. Consistent • results on the pole of charged  • are obtained. • The pole position for charged  • is consistent with that for • neutral  within the error. BESII Preliminary K*(1410), K*(1430) M(K0) GeV/c2 

  32. First observation of (2S)+ This decay mode is thought to be mainly produced from the annihilation of three gluons into ss pair.   M Statistical significance ~ 5 • X,Y,Z type of particles in • ss system ? • Hint: Y(2175) ? • BESIII will answer these questions with help from theorists M BESII preliminary

  33. Resonance parameter fit Probability =31.8% Phys. Lett. B660, (2008)315 Heavy charmonia parameters were fitted with the data between 3.7–5.0GeV, taking into accounts the phase angles, interference, energy-dependent width, etc.

  34. Fitting Results Comparison Phys. Lett. B660 (2008) 315-319

  35. (3770) non-DD decays • (3770) decays most copiously into DD. • (3770) is a mixture of the 13D1 and 23S1, other (2S)-like decays for (3770) are expected. (mixing angle 122o). • Many theoretical calculations estimate the partial width for (3770)  +- J/. (Lipkin, Yan, Lane, Kuang, Rosner) • Kuang obtained a partial width for (3770)  +- J/ in the range of 25 -113 keV. (Y.P. Kuang, PRD 65 (2002) 094024) 35

  36. BES first reported (3770) non-DD decay (3770)  +- J/ Open histogram is for e+e-, histogram in yellow is for +- The histogram is ’ error bars are ’+’’ data MC 27.7 pb-1 20 times large than the data mainly hep-ex/0307028 PLB 605 (2005) 63 36

  37. Anomalous LineShape of [e+e-Hadrons] in energy region from 3.650 to 3.872 GeV 1. Significances of the two amplitudes are more than 7 2. Significance of the interference between the two amplitudes is 3.6  3. The hypothesis of (3770) amplitude +G(3900) and interference does not significantly improve the fit from the one (3770) amplitude hypothesis A fine scan in this area at BESIII is needed! Two data sets taken in March and December 2003 Phys.Rev.Lett101,102004,2008

  38. R Measurement • Previous exps: R/R  15 % below 5 GeV • 1998-1999, BESII measured 6+85 points R values • in 2-5 GeV region. R/R  6 % 38 Phys. Rev. Lett., 88 (2002) 101802

  39. Phys. Rev. Lett., 97 (2006) 262001 In 2003, from a dedicated (3770) scan data, the R values at 68 energy points from 3.650-3.872 GeV were measured. stat. error:  3-4% syst. error:  4%

  40. R values at 2.6, 3.07 and 3.65 GeVmeasured • with the precision of about 3.5% at BESII in 2008. The running coupling constant s(s) was determined

  41. BEPCII/BESIII • In the 1990s, there was discussion of the future. The conclusion was to continue tau-charm physics with a major upgrade of the accelerator and detector (BEPCII/BESIII). Officially approved in 2003. • The physics window is precision charm physics and the search for new physics. • High statistics: high luminosity machine + high quality detector. • Small systematic error: high quality detector.

  42. BEPC II Storage ring: Large angle, double-ring RF SR RF Beam energy: 1.0-2 .3GeV Luminosity: 1×1033 cm-2s-1 Optimum energy: 1.89 GeV Energy spread: 5.16 ×10-4 No. of bunches: 93 Bunch length: 1.5 cm Total current: 0.91 A SR mode: 0.25A @ 2.5 GeV IP

  43. Main parameters achieved in collision mode 43

  44. BESIII @ BEPCII BESII @ BEPC acceptance ~ 93% 44

  45. The BESIII Collaboration Totally 42 institutions Europe (8) GSI, Germany University of Bochum, Germany University of Giessen, Germany KVI/University of Groningen, Netherland INFN, Laboratri Nazionali di Frascati University of Torino, Italy JINR, Dubna, Russia Budker institute of Nuclear Physics Russia   USA (6) University of Hawaii University of Washington Carnegie Mellon University Univ. of Minnesota University of Rochester Indiana University China (25) 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. , Huangshan College. Nanjing Univ., Nanjing Normal Univ. Guangxi Normal Univ., Guangxi Univ. Hong Kong University                 Chinese Univ. of Hong Kong           Others in Asia(3) Tokyo University Seoul National Univ. Univ. of Punjab, Lahore 45

  46. BESIII commissioning and data taking milestones Mar. 2008: first full cosmic-ray event April 30, 2008: Move the BESIII to IP July 20, 2008: First e+e- collision event in BESIII Nov. 2008: ~ 14M (2S) events collected April 14, 2009 ~100M (2S) events collected May 30, 2009 ~42 pb-1 at continuum collected (3.65 GeV) July 28, 2009 ~200M J/ events collected Machine luminosity Peak Lumi. @ Nov. 2008: 1.2 1032cm-2s-1 Peak Lumi. @ May 2009: 3.21032cm-2s-1

  47. First collision event on July 19, 2008

  48. Data accumulated at BESIII Mar. 6 – April 14 May 24 – June 2 100 M (2S) data 42 pb-1 data at 3.65 GeV June 12 – Jul. 28 200 M J/ data

  49. Statistics at BESIII at designed peak Luminosity (assuming 107s data taking time each year) 49

  50. ●Layer 7 ●Layer 22 Detector performance and calibration dE/dxreso.: 5.80% Design：6-8% Wire reso. Design: 130 mm CsI(Tl) energy reso. Design: 2.5%@ 1 GeV Barrel TOF reso.: 78ps Design：80-90ps Bhabha

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