(Representing BESIII Collaboration) Institute of High Energy Physics, Beijing. Workshop on Hadron Physics, July 27 31, 2010, Tsinghua University

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1 BESIII status and results Xiaoyan SHEN (Representing BESIII Collaboration) Institute of High Energy Physics, Beijing Workshop on Hadron Physics, July 27 31, 2010, Tsinghua University

2 Introduction Status of BESIII Outline Recent results from BESIII Summary

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

4 (BEPC/BES) beam energy: (2.5) GeV BES Physics goal 1 2.3GeV e+ e collisions produce charmonium states (J/ψ,ψ(2S), χ cj and ψ(3770) etc.), charm mesons and τ lepton. 4 4

5 We are unique now in τ-charm region Physics at BEPC/BES From PDG The Y s are here! In transition region between pqcd and non pqcd. 5

6 BEPCII/BESIII In the 1990s, there was discussion of the future. The conclusion was to continue tau charm physics witha major upgradeof theaccelerator and detector (BEPCII/BESIII). Officially approved in 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.

7 nsn2.5m8bepcii Storage Ring: Double ring RF 2 mrad822 SR RF 1..1Beam energy: GeV Luminosity: cm -2 s -1 O energy: 1.89 GeV 0.Optimum Energy spread: c5cm No. of bunches: 93 mbunch length: 1.5 cm Total current: 0.91 A SR mode: 2.5 GeV IP

9 BESIII collaboration: 46 Institutes US (6) Univ. of Hawaii Univ. of Washington Carnegie Mellon Univ. Univ. of Minnesota Univ. of Rochester Univ. of Indiana Europe (9) Germany: Univ. of Bochum, Univ..of Giessen, GSI Russia: Dubna; BINP, Novosibirsk Italy: Univ. of Torino,Frascati Lab Netherland:KVI/Univ. of Groningen JINR Korea (1) Seoul Nat. Univ. ~ 300 collaborators Pakistan (1) China(29) Univ. of Punjab IHEP, CCAST, Shandong Univ., Univ. of Sci. and Tech. of China Zhejiang Univ., Huangshan Coll. 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. Suzhou Univ., Hangzhou Normal Univ. LanzhouUniv., Henan Sci. and Tech. Univ. Hong Kong Univ., Hong Kong Chinese Univ. 9 Japan (1) Tokyo Univ.

10 Physics Topics at BES Study of Light hadron spectroscopy search for non qq or non qqq states meson spectroscopy baryon spectroscopy arxiv: Study of the production and decay mechanisms of charmonium states: J/ψ, ψ(2s), η C (1S), χ C{0,1,2}, η C (2S), h C ( 1 P 1 ), ψ(3770), etc. New Charmonium states above open charm threshold. Precise measurement of R values, τ mass,... Precise measurement of CKM matrix Search for DDbar mixing, CP violation, etc. 10

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

12 Motivation: Study of the spectroscopy a way of understanding the internal structure 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, isospin filter glueball spectrum from LQCD 12 Y. Chen et al., PRD 73 (2006)

13 Physics Topics at BES Study of Light hadron spectroscopy search for non qqbar or non qqq states meson spectroscopy baryon spectroscopy arxiv: Study of the production and decay mechanisms of charmonium states: J/ψ, ψ(2s), η C (1S), χ C{0,1,2}, η C (2S), h C ( 1 P 1 ), ψ(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. 13

14 Charmonium physics 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 Examples of interesting/long standing issues: ρπ puzzle Missing states? Mixing i states? New states above open charm thre.(x,y,z, )

15 Physics Topics at BES Study of Light hadron spectroscopy search for non-qqbar or non-qqq states meson spectroscopy baryon spectroscopy arxiv: Study of the production and decay mechanisms of charmonium states: J/ψ, ψ(2s), η C (1S), χ C{0,1,2}, η C (2S), h C ( 1 P 1 ), ψ(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. 15

16 R measurement R : one of the most important and fundamental quantities in particle physics. R σ σ e - e + e - q - q hadrons μ - e + μ + lowest order Why precise R important? Essential for precise tests of SM. the global fit of Higgs mass order anomalous μ magnetic 2 = ΣQ f moment from g 2 flavor color 16

1869 Study of the production and decay mechanisms of charmonium states: J/ψ, ψ(2s), η C (1S), χ C{0,1,2}, η C

17 Physics Topics at BES Study of Light hadron spectroscopy search for non qqbar or non qqq states meson spectroscopy baryon spectroscopy arxiv: Study of the production and decay mechanisms of charmonium states: J/ψ, ψ(2s), η C (1S), χ C{0,1,2}, η C (2S), h C ( 1 P 1 ), ψ(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. 17

18 Precise measurement of CKM elements Test EW theory CKM matrix elements are fundamental SM parameters that describe the mixing of quark fields due to weak interaction. d s b ' ' ' 5% precision 10% precision = V V V ud cd V V V Three generations of quark? td us cs ts V V V tb ub cb d s b Unitary matrix? CKM matrix Expect precision < 2% at BESIII Improve the precision at BESIII 18 Precision measurement of CKM matrix elements a precise test to SM model New physics beyond SM?

19 Decay constants vs LQCD f D 2.3 σ difference for f Ds. Real? BESIII may resolve this issue, reach the precision of LQCD. f Ds

CP violation is observed in K and B decays, but has never been in charm sector.

20 CP violation and 0 0 D D mixing CP violation is regarded as the origin of asymmetry of the matter and anti matter. CP violation predicted by theoretical models is not big enoughto describethe asymmetry. CP violation is observed in K and B decays, but has never been in charm sector. e + e - ψ(3770) D 0 D 0 0 In SM, the mixing is very small. At BESIII, the sensitivity of the mixing rate: D D 20 0 CP D D 0 mixing : a good place to search for CP violation

21 BESIII commissioning o and data taking milestones Mar. 2008: first full cosmic ray event April 30, 2008: Move the BESIII to IP July 19, 2008: First e + e collision event in BESIII Nov. 2008: ~ 14M ψ(2s) events April 14, 2009: ~106M ψ(2s) events May 30, 2009: ~42 pb 1 at continuum (3.65 GeV) July 28, 2009: ~226M J/ψ events Aug. Dec., 2009: summer maintenance, SR run Jan June : ~ 900 pb 11 at 3770 MeV June 2 15, 2010: scan at around 3770 MeV Peak May 2009: cm 2 s 1

22 Inclusive photon spectrum of ψ(2s) Excellent photon resolution χ c2 χ c1 χ co χ c1,2 γ J/ψ η c BESIII preliminary

23 Results from BESIII Confirm BESII results threshold enhancement in γpp, X(1835), New improved measurements h c, η c, χ cj,, New observations χ cj decays h c decays Light hadrons, ( ) J/ψ ψ(2s)

24 About h 1 c ( P 1 ) state The charmonium family has been studied for many years, the knowledge on h c ( 1 P 1 ) is limited. E835 made scans of p energy for the reaction pp h c γη c, η c γγ, 3σ level The results from the year 1997 scan and the year 2000 scan were combined to obtain M(hc)=3525.8±0.2±0.2 MeV. No evidence was found for hc in the previously reported reaction pp hc π 0 J/ψ (E760, 1992) The h c ( 1 P 1 ) state was observed by CLEO_c in For ψ(2s) only observed in ψ(2s) π 0 h For ψ(2s), only observed in ψ(2s) π 0 h c The main decay mode of h c : E1 transition h c γη c

25 h c at CLEOc (with whole data set)

26 h c at BESIII Inclusive analysis of ψ(2s) π 0 h c identify h c in the inclusive recoiling mass spectrum of π 0. E1 tagged analysis of ψ(2s) π 0 h c, h c γη c tag E1 photon (~503 MeV) in h c γη c h c significance improved in inclusive π 0 spectrum Exclusive analysis of ψ(2s) π 0 h c, h c γη c fully reconstruct the exclusive η c decays

27 Observation of h c : Inclusive ψ(2s) π 0 h c background subtracted Select inclusive π 0 A fit of D Gaussian signal + 4 th Poly. bkg Combined inclusive and E1 photon tagged tagged spectrum Br(ψ(2S) π 0 h c ) = (8.4 ± 1.3 ± 1.0) 10 4 (First measurement) Br(h c γη c ) = (54.3 ± 67± 6.7 ± 52)% 5.2) (First measurement) 27

28 Observation of h c : E1 tagged ψ(2s) π 0 h c,h c γη c BESIII PRL 104, (2010) background subtracted Select E1 photonto tag h c A fit of D Gaussian signal+ sideband M(h bkg. yield: 013± 018MeV/c 2 c ) = ± 0.13 ± 0.18 Γ(h c )= 0.73 ± 0.45 ± 0.28 MeV/c 2 (< 1.44 MeV/c 90% CL) (First measurement) Br(ψ(2S) π 0 h c ) Br(h c γη c ) = (4.58 ± 0.40 ± 0.50) 10 4

29 χ cj study at BESIII The χ cj decays provide good place to: study gluonium: χ c gg (qq)(qq) C. Amsler and F. E. Close,Phys. Rev. D 53, 295 (1996). test COM G. T. Bodwin et al., Phys Rev. Lett. D51, 1125 (1995). H. W. Huang and K. T. Chao, Phys. Rev. D54, 6850 (1996). J. Bolz et al., Eur. Phys. J. C 2, 705 (1998). Improved measurement of χ cj π 0 π 0, ηη, First measurement of χ cj ωφ First measurement of χ c1 ωω,, φφ χ c1 First measurement of χ cj γφ

30 Study of ψ(2s) γχ cj ; χ cj π 0 π 0, ηη (η, π 0 γγ ) ψ(2s) γπ 0 π 0 ψ(2s) γηη BESIII: PRD 81, (2010). χ c1 ππ, ηη not allowed by parity conservation. CLEOc: PRD 79, (2009). 30 Decay mode χ c0 (10 3 ) χ c2 (10 3 ) π 0 π 0 BESIII 3.23±0.03±0.23±0.14± ± ± 0.88±0.02±0.06±0.04± ± ± PDG ± ±0.08 CLEOc 2.94±0.07±0.32± ±0.03±0.07±0.04 ηη BESIII 3.44±0.10±0.24± ±0.04±0.05±0.03 PDG08 2.4±0.4 < 0.5 CLEOc 3.18±0.13±0.31± ±0.05±0.05±0.03 CLEOc used their own branching ratios for ψ γχ cj.

31 χ cj γv, V=φ,ρ,ω Events / ( 0.01 GeV/c 2 ) χ c1 γφ 140 χ c1 γρ 70 χ c1 γω BESIII preliminary Events / ( GeV/c BESIII preliminary Events / ( 0.01 GeV/c 2 2 ) ) BESIII preliminary M γ ω (GeV/c ) H M M γ ρ (GeV/c ) γ φ (GeV/c ) H B (10 6 ) BESIII CLEOc pqcd χ c0 γφ < 14.8 < χ c1 γφ 27.3 ± 5.5 stat < χ c2 γφ < 7.8 < χ c0 γρ 0 < 9.5 < χ c1 γρ ± 14 stat 243 ±19 ± χ c2 γρ 0 < 19.7 < χ c0 γω < 11.7 < χ c1 γω 73.5 ± stat 83 ±15 ± χ c2 γω < 5.8 < H χ c1 γφ observed for the first time. pqcd predictions too low. Difference may be explained by non perturbative QCD loop corrections. D.Y Chen et al, arxiv: v2. CLEOc: PRL 101, (2008) pqcd: Y.J. Gao et al., hep-ph/

32 Study of χ cj VV, V = ω,φ BR(10 3 ) χ c0 χ c2 φφ 0.94±0.21± ±0.30±0.25 ωω 2.29±0.58± ±0.47±0.36 BESII, PLB 642, 197 (2006) BESII, PLB 630, 7 (2005) χ c1 φφ(and ωω) should be highly suppressed because C parity requires L = 2. φφ χ c2 BESIII sees clear χ cj φφ 4K signals χ c0 χ BR(10 33 ) BESIII PDG08 c1 χ c0 φφ 0.80 ± ± 0.20 χ c1 φφ 0.42 ± 0.03 χ c2 φφ 1.15 ± ± 0.30 First observation of χ c1 φφ Errors: statistical only.

33 clear χ cj ωω 2(π + π π 0 ) ωω χ c 1 χ c 0 χ c 2 clear χ cj ωφ (π + π π 0 )(KK) χ c 0 χ c 1 ωφ χ c 2? First observation of χ c1 ωω. 33 Doubly OZI suppressed χ cj ωφ observed for the first time.

34 pp mass threshold study at BES J / ψ γ pp BESII theoretical speculation: p p bound state (baryonium) FSI effect M pp -2m p (GeV) Observation of an anomalous enhancement near the threshold of p p mass spectrum PRL 91 (2003)

35 pp massspectrum spectrum inother channels The narrow threshold enhancement is not observed in those channels ϒ(1S ) γ pp@cleo J / ψ ω pp@besii ψ γ pp@ BESII M pp (GeV) No significant narrow strong enhancement near threshold (~2σ if fitted with X(1860)) 35

36 pp threshold CLEOc fit with one resonance as BES did: QWG2010 Z. Metreveli agree with BESII results CLEO-c preliminary fit with three contributions: BES considered these (2) and (3) as systematic errors. 36

pp mass spectrum and Dalitz plot at BESIII ψ(2s) ππ J/ψ, J/ψ γpp BESII J / ψ γ pp 0 01 0.1 M 0. pp -2m 0.

37 pp mass spectrum and Dalitz plot at BESIII ψ(2s) ππ J/ψ, J/ψ γpp BESII J / ψ γ pp M 0. pp -2m 0. p (GeV) 2 3 M= MeV/c Γ < 30 MeV/c 2 (90% CL) M=1865±5MeV/c 2 Γ < 33 MeV/c 2 (90% CL) PRL 91 (2003)

38 J/ψ γpp BESIII preliminary BESII M= MeV/c Γ < 30 MeV/c 2 (90% CL) Fit result: Mass= ± 0.8 M ev / Γ< 8 MeV(90% CL) c 2 38

39 pp threshold odmass spectrum in ψ radiative decay BESII BESIII preliminary i ψ γ pp PRL 99 (2007) M pp (GeV) No significant narrow strong enhancement near threshold (~2σ if fitted with X(1860)) No significant narrow threshold enhancement pp FSI interpretation of the narrow and strong threshold enhancement is disfavored.

40 QWG2010 Z. Metreveli CLEO c preliminary BESIII preliminary Confirm the no observation of enhancement in ψ(2s) channel pure FSI effect unlikely

42 X(1835) BESIII + + J / ψ γπ π η ( η γρ, ρ π π ) BESIII 18σ preliminary BESIII preliminary + + J / ψ γππηη ( ππη) BESIII preliminary i 9σ BESIII preliminary i

43 Mass spectrum fit??? BESIII preliminary Whether there are two new resonances, further careful study is needed. F it result(statisticsignificant~21 σ ) : M = ± 2.8( stat) MeV Γ= 99.2 ± 9.2( stat ) MeV BESII BESII result(statisticsignificant ~ 7.7 σ ) : M = ± 6.1( stat) ± 2.7( syst) MeV Γ= 67.7 ± 20.3(stat) ± 7.7(syst)MeV Hadron 09

Study of a 0 0( (980) f 0 0( (980) mixing from J/ψ φf 0 φa 0 φηπ χ 0 0 + 0 c1 a 0 π f 0 π π π π Mixing intensity provides important information in understanding the nature of a 0

44 Study of a 0 0( (980) f 0 0( (980) mixing from J/ψ φf 0 φa 0 φηπ χ c1 a 0 π f 0 π π π π Mixing intensity provides important information in understanding the nature of a 0 (980) and f 0 (980). Narrow peak (8 MeV) at around 980 MeV can be expected in ηπ (J/ψ φfφ φa φηπ case) or π + π a π 0 f π 0 0 φ 0 (χ c1 0 0 π + π π 0 case) invariant mass spectra.

45 ξ fa = Br(J/ψ φf 0 (980) φa 0 (980) φηπ 0 ) / Br(J/ψ φf 0 (980) φππ) = (0.6 ±0.2(stat.) t t)±0.2(sys.))% ))%(<11%@90%C 1.1% C. L) L.) ξ af = (0.32 ±0.16(stat.) ±0.12(sys.))% (< 90% C. L.)

46 Comparison of BESIII results with others

47 Summary BEPCII/BESIII upgrade completed successfully: Peak Luminosity of 3.2*10 32 achieved. ~106 M ψ(2s) and ~226 M J/ψ events obtained in ~950 pb 1 at ψ(3770) so far in Nice results are obtained More results will come soon

49 First collision event on July 19, 2008 e + e - ψ(3770) D 0 D 0

50 MDC performance & data/mc Reso. 135 μm σ P =11.0 MeV/c P

51 Double-layer TOF Barrel Double Layer Time Resolution (ps) Z (cm) Time Resolution Design Bhabha Dimu (ps) Target Barrel Single 100~ Layer Barrel Double 80~ Layer Endcap 110~

52 EMC (CsI(Tl)) Barrel energy resolution energy deposit for e+e- γγ energy resolution for Bhabha events Position resolution for Bhabha 4.4 mm

53 First observation of ψ(2s) γγj/ ψ Two photon transitions are well known in excitations of molecules, atomic hydrogen, and positronium. A. Quattropani etal, PRA 25, 3079 (1982). F. Bassani etal, PRL 39, 1070 (1977). A. Quattropani etal, PRL 50, 1258 (1983). CLEO observed two photon transitions in Υ(3S) Υ(2S). F. Butler etal, PRD 49, 40 (1994). Never been observed in the charmonium system. Observation helpful to understand QCD. Theoretically: potential models give discrete spectra (ψ(2s) (2S) γχ cj,χ cj γj/ ψ) ) coupled channel models can give continuous spectra. theoretical work ongoing. 53

54 select ψ(2s) γγj/ψ, J/ψ l + l - events. J/ψ ee channel (μμ similar): RM γ 2 γ 1 - high energy gamma, γ 2 - low energy gamma ee ee M γ1γ2 data background MC + continuum continuum only signal (phase space; BR = 1 x 10 - select events in box to enhance signal. see clear excess over BG + continuum in M J/ ψ distribution. Significance > 10σ B(ψ(2S) γγj/ψ) [both ee and μμ] = (1.02 ± ) x 10-3 ee BESIII preliminary 54 M J/ψ

(Representing BESIII Collaboration) Institute of High Energy Physics, Beijing. QCD10, June 28 July 3, 2010, Montpellier, France

BESIII status and results Xiaoyan SHEN (Representing BESIII Collaboration) Institute of High Energy Physics, Beijing 0 QCD10, June 28 July 3, 2010, Montpellier, France Introduction Status of BESIII Outline