Latest Results from BESIII

Transcription

1 Latest Results from BESIII Guangshun Huang (For the BESIII Collaboration) University of Science and Technology of China (USTC) G.S. Huang SPCS2013, June 3-5 1

2 Outline Status of BEPCII/BESIII Selected Results from BESIII - XYZ meson study - Light Hadron Spectroscopy - Charmonium Transitions - Charm Decays - τmass Scan Summary G.S. Huang SPCS2013, June 3-5 2

3 Bird View of BEPCII /BESIII Storage ring Linac BESIII detector BSRF Beijing electron positron collider BEPCII Beam energy GeV Energy spread:. Design luminosity /cm 2 ψ(3770) Achieved luminosity ~ /cm 2 /s IHEP,Beijing 2004: start BEPCII construction 2008: test run of BEPCII 2009-now: BECPII/BESIII data taking G.S. Huang SPCS2013, June 3-5 3

4 BEPC II: Large Crossing Angle ngle, Double-ring 8ns 2.5m RF 22 mrad RF Compton back-scattering for high precision beam energy measurement BESIII is here 0.1cm 1.5cm Beam energy: GeV 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 SR mode: 0.25A@2.5GeV IP G.S. Huang SPCS2013, June 3-5 4

5 NIM A614, 345 (2010) The BESIII Detector Drift Chamber (MDC) σp/p ( 0 / 0 ) = 0.5%(1GeV) σ de/dx ( 0 / 0 ) = 6% Super-conducting magnet (1.0 Tesla) Time Of Flight (TOF) σ T : 90 ps Barrel 110 ps endcap μ Counter 8-9 layers RPC δrφ=1.4 cm~1.7 cm EMC: σe/ E( 0 / 0 ) = 2.5 % (1 GeV) (CsI) σ z,φ (cm) = cm/ E G.S. Huang SPCS2013, June 3-5 5

6 BESIII Data Taking July 19, 2008: first e + e - collision event in BESIII Nov. 2008: 14M ψ(2s) events for detector calibration 2009: 106M ψ(2s) 4 CLEO-c 225M J/ψ 4 BESII 2010: 0.9 fb -1 ψ(3770) 2011: 2.0 fb -1 ψ(3770) 0.5 fb 4.01 GeV 3.5 CLEO-c World s largest sample of J/ψ,ψ(2S) and ψ(3770) 2012: tau mass scan: 22 pb -1 ; ψ(2s): 0.4B; J/ψ: 1B; J/ψlineshape, R scan (2.23, 2.4, 2.8, 3.4 GeV) 2013: 1.0, 0.8, 0.5 fb 4.23, 4.26, 4.36 GeV and scan in vicinity Future plans: R scan, D s physics (E cm =4170 MeV), τ scan, 5-10 fb -1 ψ(3770) for DD physics, G.S. Huang SPCS2013, June 3-5 6

7 US(6) Univ. of Hawaii Univ. of Washington Carnegie Mellon Univ. Univ. of Minnesota Univ. of Rochester Univ. of Indiana ~350 physicists 52 institutions from 11 countries The BESIII Collaboration Europe (12) Germany: Univ. of Bochum, Univ. of Giessen, GSI Univ. of Johannes Gutenberg Helmholtz Ins. In Mainz Russia: JINR Dubna; BINP Novosibirsk Italy: Univ. of Torino,Frascati Lab Netherland:KVI/Univ. of Groningen Sweden: Uppsala Univ. Turkey: Turkey Accelerator Center Pakistan (2) Univ. of Punjab COMSAT CIIT G.S. Huang SPCS2013, June 3-5 China(30) Korea (1) Seoul Nat. Univ. Japan (1) Tokyo Univ. IHEP, CCAST, UCAS, Shandong Univ., Univ. of Sci. and Tech. of China Zhejiang Univ., HuangshanColl. Huazhong Normal Univ., Wuhan Univ. Zhengzhou Univ., Henan Normal Univ. Peking Univ., Tsinghua Univ., Zhongshan Univ.,Nankai Univ. Shanxi Univ., Sichuan Univ., Univ. of South China Hunan Univ., Liaoning Univ. Nanjing Univ., Nanjing Normal Univ. Guangxi Normal Univ., Guangxi Univ. Suzhou Univ., Hangzhou Normal Univ. Lanzhou Univ., Henan Sci. and Tech. Univ. Hong Kong Univ., Hong Kong Chinese Univ. 7

8 Physics BESIII XYZ meson physics: -Zc in Y(4260) π + π - J/ψ Light hardron physics -meson & baryon spectroscopy -threshold effects -multiquark states -glueballs & hybrids Charmonium physics: - precision spectroscopy - transitions and decays Charm physics: - (semi-)leptonic decays - f D & f D decay constants. s - CKM matrix: V cd, V cs - D 0 -D 0 mixing and CPV - strong phases QCD & τ -physics: - τ mass / τ decays - precision R-measurement - form-factors - two-photon physics G.S. Huang SPCS2013, June 3-5 8

9 The CharmoniumSystem G.S. Huang SPCS2013, June 3-5 9

10 Recent Results on XYZ meson Physics Observation of the Zc(3900) G.S. Huang SPCS2013, June

11 Z c± observed at BESIII Y(4260) π + π - J/ψ result agrees with BaBar & Belle, better precision; Zc significance > 8σ; Mass (3899.0±3.6±4.9) MeV; Width (46±10±20) MeV; Quickly confirmed by Belle & CLEO-c; arxiv: , accepted by PRL. 525 pb -1 G.S. Huang SPCS2013, June

12 Z b±, Z c± : Exotic Hadrons In Quark Model, hadron has 2 or 3 quarks; meson: baryon: 2 quarks 3 quarks QCD allows hadrons with N quarks 2, 3 glueball: N quarks = 0 (gg, ggg, ) hybrid: N quarks = 2 + excited gluon multiquark state: N quarks > 3 molecule: bound state of more than 2 hadrons Z b±, Z c± are special, because they apparently have 4 quarks ( / + 2 light quarks): π ± ϒ(nS), π ± ψ(ns). G.S. Huang SPCS2013, June

13 Recent Results on Light Hadron Physics ωφ threshold enhancement in J/ψ γωφ ηη system in J/ψ γηη J/ψ ΛΣ 0 + c.c. G.S. Huang SPCS2013, June

14 ωφthreshold enhancement in J/ψ γωφ G.S. Huang SPCS2013, June

15 PRD 87, (2013) J/ψ γωφat BESIII φ ω Is X(1810) the f 0 (1710)/f 0 (1790) or a new state? G.S. Huang SPCS2013, June

16 Study of ηηsystem G.S. Huang SPCS2013, June

17 J/ψ γηηat BESIII: PRD 87, (2013) LQCD: lowest mass glueball with 0 ++ is in GeV f 0 (1710) and f 0 (2100) are dominant scalars f 0 (1500) exists (8.2σ) f 2 (1525) is the dominant tensor G.S. Huang SPCS2013, June

18 PRD 86, (2012) J/ψ ΛΣ 0 + c.c. PDG2010: Br(J/ψ ΛΣ 0 )< First observation Study isospinbreaking mechanism in J/ψ ΛΣ 0 + c.c. Search for Λ(1520) γλ Measured η c ΛΛ (Only observed by Belle in B ΛΛ K before) M γλ M γλ M ΛΛ G.S. Huang SPCS2013, June

19 Recent Results on Charmonium Physics Observationof ψ(2s) γη c (2S) e + e - η GeV ψ(2s) ηj/ψ, π 0 J/ψ ψ(2s) K + K - π 0, K + K - η ψ(2s) pp π 0 χ cj ΛΛ π + π - χ cj ΛΛ, Σ 0 Σ 0, Σ + Σ - χ cj p π -, p π - π 0 G.S. Huang SPCS2013, June

20 η c (2S) First observation by Crystal Ball in 1982 (M=3.592, B=0.2%-1.3% from ψ(2s) γx, never confirmed by other experiments.) Published results about η c (2S) observation: Combined with the results based on two-photon processes from BaBarand Belle reported at ICHEP 2010, the world average Γ(η c (2S))=12±3 MeV The M1 transition ψ(2s) γη c (2S) has not been observed. (experimental challenge : search for real photons ~50MeV, ) Better chance to observe η c (2S) in ψ(2s) radiative transition with ~106M ψ(2s) data at BESIII. ψ(2s) γη c (2S) γkskπ / γκ + Κ π 0 observed (>10σ): PRL109, (2012). G.S. Huang SPCS2013, June

21 PRD87, (2013) ψ(2s) γη c (2S) γksk +- π -+ π + π - For η c (2S), only two measured decay Brsare available: KK πand K + K - π + π - π 0 ψ ɣη c (2S): M1 transition Search for more η c (2S) decay modes To measure the mass, width of η c (2S) The measured M, Γ are consistent with previous BESIII observation (PRL109, ). >4σ M=3646.9±1.6±3.6 MeV/c 2 Γ=9.2±4.8±2.9 MeV B(ψ(2S) ɣη c (2S))xB(KsK +- π -+ π + π - ) = (7.03±2.10±0.70)x10-6 G.S. Huang SPCS2013, June

22 e + e - PRD86, (R) (2012) Data sample: 478 pb First observation: e + e - ηj/ψ (significance > 10σ) Born cross section: (32.1±2.8 ±1.3) pb Assuming ηj/ψ from ψ(4040), Br(ψ(4040) η ηj/ψ)=(5.2±0.5±0.2±0.5) 10-3 Br(ψ(4040) π 0 J/ψ) < 2.8 CL Consistent with the theoretical calculation (Q.Wanget al., arxiv: ) Partial width of ψ(4040) η ηj/ψ: ~400keV (> two times ψ(4040) ππ ππj/ψ) Similar to the hadronic transition of Υ(4S) (admixture of a four-quark state in the wave function, M. B. Voloshin, Mod. Phys. Lett. A 26, 773 (2011)) J/ψ µ + µ - J/ψ e + e - G.S. Huang SPCS2013, June

23 PRD 86, (2012) Decay final states: γγµ + µ - or γγe + e - ψ π 0 J/ψisospinviolation QCD multipole-expansion + axial anomaly R = (G. A. Miller et al., Phys. Rep. 194, 1 (1990).) Charm-meson loops R = 0.11±0.06 (F. K. Guoet al., PRL 103, (2009)) ψ ηj/ψ, π 0 J/ψ G.S. Huang SPCS2013, June

24 Motivation Test 12% rule (Q h ) & Study ρπ puzzle in ψ VP decays Test HSR Search for excited φ, K* states PWA applied Measured ψ KK *, φη, φπ 0 (isospin violated) Q h in VP decays significantly deviate from 12% First observation: ψ K + K * 2(1430) - (HSR suppressed decay) ψ K + K - π 0, K + K - η φ (1850)? 3 PRD 86, (2012) φ (2170)? 3.1 σ 3.8σ G.S. Huang SPCS2013, June

25 PWA of ψ ppπ 0 PRL110, (2013) Non-relativistic quark model is successful in interpreting of the excited baryons Predicted more excited stated ( missing resonance problem ) J/ψ(ψ ) decays offers an window to search for the missing resonance Isospin conservation supressed Two new baryonic excited states are observed! G.S. Huang SPCS2013, June

26 Color-Octet contribution: Large effect in P-wave state. e.g. : χ cj pp, theoretical prediction consistentwith exp. (Wong, Nucl. Phys. A674, 185 (2000)) χ cj ΛΛ not consistent What about other baryon anti-baryon decays? Experiment measured NR: χ cj ΛΛ π + π - χ cj Σ(1385) + Λ π - +cc χ cj Σ(1385) - Λ π + +cc First evidence: χ cj Σ(1385) Σ (1385) Experiment consist with theoretical prediction χ cj ΛΛπ + π - M M π + π ΛΛ Σ*(1385) Λ M Σ - (1385) Λ π (1385) (1385) PRD 86, (2012) π M + (1385) - Σ Σ (1385) M Σ Σ M π π ΛΛ + G.S. Huang SPCS2013, June

27 χ cj ΛΛ, Σ 0 Σ 0, Σ + Σ - PRD 87, (2013) χ cj decay properties are essential to test pqcdmodels and QCDbased calculations. many decay modes of χ cj B have not been observed yet, or measured with poor precision. measurements of χ cj B are helpful for understanding the HSR, which prohibits χ c0 decays into baryon-antibaryon pairs. G.S. Huang SPCS2013, June

28 Color-Octet contribution: Large effect in P-wave state. Search for N* states Experiment measured Branching fractions for χ c0,1,2 p π - +c.c. χ c0,1,2 p π - π 0 +c.c. (most precise measurements) Intermediate states: N*(1400), N*(1700) in both pπand π Threshold enhancement of p, or N*(2190), N*(2220)? Further detailed PWA need to be done! χ cj p π -, p π - π 0 PRD 86, (2012) G.S. Huang SPCS2013, June

29 Charm Physics(all preliminary) D + µ + ν D 0 K /π e + ν Search for D 0 Ds tagging G.S. Huang SPCS2013, June

30 D - Tagging M = E p 2 2 BC beam D Resolution: 1.3 MeV for pure charged modes; 1.9 MeV for modes with one π 0. 9 singly tagged modes N D -= (1.57±0.2) x 10 6 G.S. Huang SPCS2013, June

31 D + µ + ν In the system recoiling against the tagged D -, select leptonic decay for D + µ + ν Signal selection: G.S. Huang SPCS2013, June

32 D + µ + ν G.S. Huang SPCS2013, June

33 Backgrounds for D + µ + ν G.S. Huang SPCS2013, June

34 D + µ + ν:preliminary Results N(D + µ + ν) = ±20.6 B(D + µ + ν) = (3.74 ±0.21 stat ±0.06 sys )x10-4 f D+ = ( ±5.72 stat ±1.97 sys ) MeV B(%) f D (MeV) G.S. Huang SPCS2013, June

35 D 0 Tagging 4 tag modes, 0.92 fb -1 (preliminary) G.S. Huang SPCS2013, June

36 D 0 K/πe ν BESIII preliminary, with 0.92 fb -1 data, will improve with full 2.9fb -1 soon. Form factor measurement ongoing. G.S. Huang SPCS2013, June

37 Search for D 0 γγ Forbidden FCNC transition (c u+γ); SM prediction: B(D 0 γγ) 10-8 or less; Results presented in B(D 0 γγ)/b(d 0 π 0 π 0 ) < 5.8 x % CL, or B(D 0 γγ) < 4.6 x % CL (preliminary, to be improved); PDG 2.7 x 10-5, CLEO-c preli x 10-6, BaBar2.2 x D 0 π 0 π 0 : 4081±117 events D 0 γγ: -2.9±7.1 events G.S. Huang SPCS2013, June

38 D s Tag (part of 4010 MeV) BESIII Preliminary BESIII Preliminary ~1.6 MeV ~1.4 MeV f (both and modes ) measurement underway Note: this data is at 4010 MeV: ~0.3 nbof We plan to run at 4170 MeV: ~0.9 nbof pro: higher cross-section; con: need transition photon ( ) G.S. Huang SPCS2013, June

39 τmass Scan G.S. Huang SPCS2013, June

40 τ Mass measurement 12 points, Lum.: 5 pb 1 M τ = MeV σm τ / M τ = PDG10: ±0.16 MeV E cm (GeV) BESI results: stat. err. (0.18 / 0.21) is compatible with syst. (0.25 / 0.17) G.S. Huang SPCS2013, June

41 τ Mass measurement in 2012 New beam energy measurement system with a precision of 5x10-5 ; Data at 4 energy points were taken, ~5 pb -1 at the τ threshold; Expect statistical precision is ±0.3 MeV, systematic error <0.1 MeV; More data expected later to reduce statistical precision to 0.1 MeV. G.S. Huang SPCS2013, June

42 Summary BESIII has been successfully operating since 2008: World largest data samples at J/ψ, ψ(2s), ψ(3770), Y(4260), Y(4360), Study of XYZ mesons: Observation of the Zc(3900). Light quark states: ωφ threshold enhancement in J/ψ γωφ. ηη system in J/ψ γηη. J/ψ Λ Σ 0 + c.c. Charmonium transitions and decays: Observation of η c (2S) in ψ(2s) γη c (2S) decay. e + e - η GeV. ψ(2s) ηj/ψ, π 0 J/ψ, ψ(2s) K + K - π 0, K + K - η New states in ψ(2s) p p π 0 χ cj Λ Λ π + π -, χ cj Λ Λ, Σ 0 Σ 0, Σ + Σ -, χ cj p π -, p π - π 0 Charm decays: D + µ + ν, D 0 K/π e ν, D 0 γγ. τ mass measurement. Lots of results published, more to come! G.S. Huang SPCS2013, June

43 Recent Results on Light Hadron Physics pp mass threshold structure in J/ψ γ ψ γpp η(1405) in J/ψ γf 0 (980)π 0, f 0 (980) 2π 3 Decays of J/ψand ψ 2S G.S. Huang SPCS2013, June

44 Enhancement at pp threshold in J/ψ γ γpp J/ψ γpp ψ J/ψ, J/ψ γpp Observed at BESII in 2003 (PRL,022001) agree with spin zero expectation M =1860 MeV, Γ< 38 MeV (90% CL) Confirmed at BESIII in 2010 (CPC 34,421 (2010)) M =1859 MeV, Γ< 30 MeV (90% CL) Many possibilities: normal meson/ ppbound state/multiquark/glueball/final state interaction effect(fsi) Spin-parity analysis is essential for determining place in the spectrum and possible nature. G.S. Huang SPCS2013, June

45 Spin-Parity analysis of J/ψ γ < 2.2GeV Spin-parity, mass, width and Br. of X pp : J 0 With < 2.2GeV With <50MeV M 1832 stat syst 19 model MeV/ ψ γpp ( < 2.2GeV) With <50MeV With <50MeV >6.8 σbetter than other J assignments. PRL 108, (2012) Four components: pp,f (1910),f (2100), and 0 phase space Include the FSI effect Fit features: The fit with BW and S- wave FSI(I=0) factor can well describe pp mass threshold structure. It is much better than that Without FSI effect (7.1σ) model: Model dependent uncertainty Γ stat syst 4 model MeV/ or Γ 76 90% C.L. (Different FSI models). syst 2.3 model 10 G.S. J/ψ γx pp X pp pp 9.0 Huang SPCS2013,.. June stat

46 ψ(2s) γ γpp ( < 2.2GeV) PRL 108, (2012) M,Γ and J of X pp are fixed to the results obtained from J/ψ decays. ψ 2 γx pp X pp pp stat model 10 The production ratio R: R J/ψ stat.. s 0.12 model % It is suppressed compared with 12% rule. G.S. Huang SPCS2013, June

47 η(1405) in J/ψ γ γf 0 (980)π 0, f 0 (980) 2π f 0 (980) π + π - PRL 108, (2012) f 0 (980) π 0 π 0 f 1 /η 3.7σ f 1 /η 1.2σ First observed: η(1405) f 0 (980)π 0 (isospinbreaking) Helicity analysis indicates the peak at 1400MeV is from η(1405), not from f (1420) Br(J / ψ γη(1405) = (1.50 ± 0.11( stat.) ± 0 γπ f Large Isospin-violating decay rate: γπ π π ) Br(J / ψ γη(1405) 0.11( syst.)) BR( η(1405) f (980) π π π π ) 0 (17.9 ± BR( η(1405) a (980) π π π η) 0 5 = (7.10 ± 0.82( stat.) ± 0 γπ f 4.2)% In general, magnitude of isospin violation in strong decay should be <1%. f mixing alone can not explain the branching ratio of η(1405) f 0 (980)π γπ π π ) 0.72( syst.)) 10 G.S. Huang SPCS2013, June

48 Anomalous Lineshapeof f 0 (980) in J/ψ γ γf 0 (980)π 0 f 0 (980) π + π - f 0 (980) π 0 π MeV/ Γ MeV/ MeV/ Γ MeV/ Surprising result: very narrow f 0 (980) width: C.L. much narrower than the world average (PDG 2010: MeV/ ) A possible explanation is loop, Triangle Singularity (TS) (J.J. Wu et al, PRL 108, (2012)) G.S. Huang SPCS2013, June

49 3 Decays of J/ψand ψ J/ψ decays are dramatically different from ψ 2S decays: PLB 710, 594 (2012) Dalitz plot with background subtracted and corrected for efficiency: J/ψis dominated by ψ 2S is strongly populated by higher mass state absent in J/ψ decay Precision measurement of branching fractions: Br(J/ψ ( Br(ψ 2S ( The ratio of these two branching fractions: ψ 2S J/ψ stat.. syst % puzzle: ψ ψ 12% J/ψ J/ψ G.S. Huang SPCS2013, June Cut to remove background

50 Recent Results on Charmonium Physics Properties of h c Mass and width of η c Observationof ψ(2s) γη c (2S) First evidence of ψ(2s) γγj/ψ χ c0,2 γγ G.S. Huang SPCS2013, June

51 Property of h c (1p1) First evidence: E835 in pp h c γη c (PRD72,092004(2005)) CLEO-c observed h c in ee ψ(2s) π 0 h c, h c γη c M hf (1P)=0.08±0.18±0.12 MeV/c 2 (PRL104,132002(2010)) Study isospin forbidden transition: ψ(2s) π 0 h c Measure as well the E1 transition: h c γη c M(h c ) gives access to hyperfine splitting of 1P states: M hf (1P) = M(h c ) 1/9(M(χ c0 ) + 3M(χ c1 )+5M(χ c2 )) G.S. Huang SPCS2013, June

52 Observation of h c at BESIII (inclusive) PRL104, (2010) E1-tagged E1-untagged Select inclusive π 0 (ψ(2s) π 0 h c ) Select E1-photon in h c γη c (E1 tagged) or not (E1 untagged) E1-tagged selection gives M(h c )= ±0.13 ±0.18MeV ( M hf (1P)=0.10±0.13±0.18MeV/c 2 ) Γ(h c )=0.73±0.45 ±0.28MeV(first measurement) (<1.44MeV at 90% CL) Br(ψ(2S) π 0 h c ) Br(h c γη c )= (4.58±0.40±0.50) 10-4 E1-untagged selection gives Br( ψ(2s) π 0 h c ) = (8.4±1.3±1.0) 10-4 Combining branching fractions leads to Br( h c γ η c ) = (54.3±6.7±5.2)% (first measurement) G.S. Huang SPCS2013, June

53 PRD86, (2012) Measurements of the h c properties at BESIII (exclusive) ψ(2s) π 0 h C, h C γη C, η C is reconstructed exclusively with 16 decay modes Summed π 0 recoil mass Simultaneous fit to π 0 recoiling mass: M(h c ) = ±0.11±0.14 MeV Γ(h c ) = 0.70±0.28±0.22 MeV N = 832±35 Consistent with BESIII inclusive results PRL104,132002(2010) CLEOc exlusive results M(h c )= ±0.27±0.14 MeV/c 2 N = 136±14 PRL101, (2008) G.S. Huang SPCS2013, June

54 η c lineshapefrom ψ(2s) π 0 h c, h c γη c Sum of 16 η C decay modes Background subtracted The η C lineshapeis not distorted in the h c γη C, non-resonant bkgis small. This channel will be best suited to determine the η C resonance parameters. Symmetric lineshape in γγ production Asymmetric lineshape in ψ decay G.S. Huang SPCS2013, June

55 η c (1S) Ground state of cc system, but its properties are not well known: J/ψ radiative transition: M ~2978.0MeV/c 2, Γ ~10MeV γγ process: M = ±1.0 MeV/c 2, Γ = 31.3±1.9 MeV CLEO-c found the distortion of the η c lineshapein ψ(2s)decays cchyperfine splitting: M(J/ )-M(η c ) is important experimental input to test the lattice QCD, but is dominated by error on M(η c ) G.S. Huang SPCS2013, June

56 ψ(2s) γη c, η c exclusive decays PRL108, (2012) KsKπ K + K π 0 π + π η KsK3π 2K2ππ 0 6π Interference with non-resonant is significant! Relative phase φ values from each mode are consistent within 3σ, use a common phase value in the simultaneous fit. Mass: ±0.6±0.6MeV/c 2 width: 32.0±1.2±1.0 MeV φ: 2.40±0.07±0.08 rad or 4.19 ±0.03±0.09 rad G.S. Huang SPCS2013, June

57 Comparison of the mass and width for η c The world average in PDG2010 was using earlier measurements Hyperfine splitting: M(1S) = ± 0.8 MeV Consistent with B factory results in other production mechanisms. Agree with lattice QCD calculations of the charmonium hyperfine splitting G.S. Huang SPCS2013, June

58 η c (2S) First observation by Crystal Ball in 1982 (M=3.592, B=0.2%-1.3% from ψ(2s) γx, never confirmed by other experiments.) Published results about η c (2S) observation: Combined with the results based on two-photon processes from BaBarand Belle reported at ICHEP 2010, the world average Γ(η c (2S))=12±3 MeV The M1 transition ψ(2s) γη c (2S) has not been observed. (experimental challenge : search for real photons ~50MeV, ) Better chance to observe η c (2S) in ψ(2s) radiative transition with ~106M ψ(2s) data at BESIII. Decay mode studied: ψ(2s) γη c (2S) γkskπ / γκ + Κ π 0. G.S. Huang SPCS2013, June

59 Observation of ψ(2s) γη c (2S) PRL109, (2012) η c (2S) KsKπ η c (2S) Κ + Κ π 0 Statistical significance > 10σ Simultaneous fit with: η c (2S) signal: modified BW (M1) with fixed width (Resolution extrapolated from χ cj ) χ cj signal: MC shape smeared with Gaussian BG from e + e - KKπ (ISR), ψ(2s) KKπ (FSR), ψ (2S) π 0 KKπ: 59 measured from data G.S. Huang SPCS2013, June

60 Results on ψ(2s) γη c (2S) γkkπ M(η c (2S)) = ±2.9±1.6 MeV/c 2 Γ(η c (2S)) = 16.9±6.4±4.8 MeV Br(ψ(2S) γη c (2S) γkkπ)=(1.30±0.20±0.30) 10-5 Br(η c (2S) KKπ)=(1.9±0.4±1.1)% from BaBar Br(ψ(2S) γη c (2S))=(6.8±1.1 stat ±4.5 sys ) 10-4 CLEO-c: < PRD81,052002(2010) Potential model: ( ) 10 4 PRL89,162002(2002) G.S. Huang SPCS2013, June

61 ψ(2s) γγj/ψ Two photon transitions are well known in excitations of molecules, atomic hydrogen, and positronium. [F. Bassani etal, PRL 39, 1070 (1977);A. Quattropani etal, PRL 50, 1258 (1983)] Never been observed in the quarkonium system. CLEO-c: upper limit of Br(ψ(2S) γγj/ψ) is 1 10 (PRD 78,011102(2008)) Observation helpful to understand heavy quarkoniumspectrum & strong interaction Theoretically: Potential models give discrete spectra (ψ(2s) γχ cj,χ cj γj/ψ) Possibility of testing the hadron-loop effect Coupled channel: the hadron-loop effect also may play a important role in the continuous spectra G.S. Huang SPCS2013, June

62 First evidence of ψ(2s) γγ J/ψ Select ψ(2s) γγj/ψ, J/ψ e + e - and µ + µ - events γ sm -low energy gamma ee µµ PRL109, (2012) the χ cj components:double E1 scaling yields of the two-photon events continuum(green) + ψ(2s) decay BG(yellow) Global fit of the two-photon process and cascade χ cj processes Seeclear excess over BG + continuum Br(ψ(2S) γγj/ψ) = ( ) x 10-4 (both eeand µµ) Significance : 3.8σ including systematics Br(ψ(2S) γχ cj,χ cj γj/ψ) are also measured ee 3.44<RM(γ sm )<3.48GeV G.S. Huang SPCS2013, June

63 PRD 85, (2012) χ c0,2 γγ In analogy to the 3 P positronium decays R Γ( 3 P 2 γγ)/ Γ( 3 P 0 γγ)=0.27 First-order QCD radiative correction R=0.116±0.010 (Voloshin, Prog. Part. Nucl. Phys. 61, 455 (2008)) First measurementof f 0/2 Γ λ=0 (χ c2 γγ) / Γ λ=2 (χ c2 γγ) Relativistic potential model f 0/2 < 0.5% (T. Barnes, in Proceedings of the IX International Workshop on Photon- Photon Collisions) G.S. Huang SPCS2013, June

64 R measurement and QCD study G.S. Huang SPCS2013, June

65 First R-QCD run J/ψ Data collected at 2.23, 2.4, 2.8 and 3.4 GeV in June, 2012.!data location, not R value! G.S. Huang SPCS2013, June

66 Detail scan in high mass charmonia region planned Whatare these broad resonances? Mass resgion where some X, Y, Z particles are found. Possible new resonance that not yet discovered? G.S. Huang SPCS2013, June