Shuangshi Fang (for the BESIII Collaboration ) Institute of High Energy Physics The 7 th International Chiral Dynamics Workshop, August 6-10, 2012, Jefferson Lab, USA Highlights from BESIII

Outline Status of BEPCII/BESIII Charmonium transitions Charmonium decays Light hadron spectroscopy Charm physics Summary 2

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

BEPCII storage rings 4 Beam energy: GeV Design Luminosity: 1×10 33 cm -2 s -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 Circumference ： 237m

μCounter 8- 9 layers RPC  R  =1.4 cm~1.7 cm Time Of Flight (TOF)  T : 90 ps Barrel 110 ps endcap Drift Chamber (MDC)  P/P ( 0 / 0 ) = 0.5%(1GeV ）  dE/dx ( 0 / 0 ) = 6% EMC ：  E/√E( 0 / 0 ) = 2.5 % (1 GeV) (CsI)  z,  (cm) = cm/√E Super-conducting magnet (1.0 tesla) The BESIII Detector NIM A614, 345 (2010) 5 Comparable capabilities to CLEO-c, plus muon ID The big advantage: BEPCII is a double-ring machine designed for charm –Design (achieved) luminosity at ψ(3770): 1 (0.65) x 10 33

BESIII Collaboration 6 300> physicists 52 institutes from 11 countries (2) (12)

BESIII – physics using “charm” 7 Charmonium physics: - Spectroscopy - transitions and decays Light hadron physics: - meson & baryon spectroscopy - glueball & hybrid - two-photon physics - e.m. form factors of nucleon Charm physics: - (semi)leptonic + hadronic decays - decay constant, form factors - CKM matrix: Vcd, Vcs - D 0 -D 0 bar mixing and CP violation - rare/forbidden decays Tau physics: - Tau decays near threshold - tau mass scan …and many more.

BESIII data set and future plans 8 World’s largest sample of J / ,  (2S) and  (3770) (and still growing) Tentative future running plans: 2013 E CM =4260 and 4360 MeV for “XYZ” studies (0.5 fb -1 each) 2014 E CM =4170 MeV for Ds (~2.4 fb-1) TBD Additional ψ(3770) data billion

Below Threshold Charmonium 9 Properties not well known Problems with mass measurements

Mass and width of  c (1S) 10 mass width

 C resonance parameters from  C 11 mass:  0.6 stat  0.6 sys MeV/c 2 width: 32.0  1.2 stat  1.0 sys MeV  : 2.40  0.07 stat  0.08 sys rad (constructive) or 4.19  0.03 stat  0.09 sys rad (desconstruct) The interference between  c and non-  c decays: KsK  KK  0   KsK3  2K2  0 3(  ) Relative phase  values from each mode are consistent within 3 ,  use a common phase value in the simultaneous fit. Phys.Rev.Lett. 108 (2012)

Comparison of the mass and width for  c 12 Hyperfine splitting:  M(1S) = ± 0.8 MeV Better agreement with LQCD calculations

Property of h c (1p1) 13

Observation of h c in inclusive reaction 14

Simultaneous fit to  0 recoiling mass: M(h c ) = ±0.11±0.15 MeV  (h c ) = 0.70±0.28±0.25 MeV N = 832±35  2 /d.o.f. = 32/46 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) BESIII preliminary Summed  0 recoil mass BESIII preliminary   0 h C, h C  C,  C is reconstructed exclusively with 16 decay modes 15 h c (1P1) in   0 h c, h c   c,  c  X i (exclusive)

Observation of  ’   c (2S)  First “observation” by Crystal Ball in 1982 (M=3.592, B=0.2%-1.3% from  X, never confirmed by other experiments.)  Published results about  c (2S) observation: Combined with the results based on two-photon processes from BaBar and Belle reported at ICHEP 2010, the world average  (  c (2S))=12±3 MeV  The M1 transition  c (2S) has not been observed. ( experimental challenge : search for real photons ~50MeV, )  Better chance to observe  c (2S) in  radiative transition with ~106M  data at BESIII.  Decay mode studied:  c (2S)   KsK       16

Observation of  c (2S) in  c (2S),  c (2S)  K s K , K + K -  0 M(  c (2S)) = (3637.6±2.9  1.6) MeV/c 2 G (  c (2S)) = 16.9±6.4±4.8 Statistical significance larger than 10.2  Br(  c (2S)   KK  ) =(1.30±0.20 stat ±0.30 sys ) × Br(  c (2S)  KK  )=(1.9±0.4±1.1)% From BABAR(PRD78,012006) Br(   c (2S)) =(6.8±1.1 stat ±4.5 sys ) ×10 -4 CLEO-c: <7.6  10  4 PRD81,052002(2010) Potential model: (0.1  6.2)  10  4 PRL89,162002(2002) With 106M  events: simultaneous fit results: Phys. Rev. Lett. 109, (2012) 17

Search for  c (2S)  VV No signals observed in  c (2S)  , K* 0 K* 0,  ; more stringent UL’s are set. Test for the ‘intermediate charmed meson loops’ :  c (2S)  VV is highly suppressed by the helicity selection rule. ‘intermediate charmed meson loops’ can increase the production rate of  c (2S)  VV. Br(    c (2S)   VV) (10 -7 ) Br(  c ’  VV) (10 -3 ) (using BESIII BF(    c (2S)) Br(  c ’  VV) (10 -3 ) Theory: (arXiv: )  <12.7< ~ 28.9 K* 0 <19.6< ~ 35.8  < 7.8< ~ 9.8 PRD84, R (2011) (PRD81, (2010))  K* 0  18

19 Coupled channel: the hadron-loop effect also may play an important in the continuous spectra

July 4, 2012Hai-Bo Li (IHEP) 20 Select  (2S)   J/ , J/   e + e - and  +  - events  sm - low energy gamma ee  the  cJ components: double E1 scaling yields of the two-photon events continuum(green)+  ’- decay BG(yellow) Global fit of the two-photon process and cascade  cJ processes See clear excess over BG + continuum 3.44<RM(  sm )<3.48GeV arXiv: Submit to PRL

Higher-order Multipole in  c2,  c2  +  -,K + K - Investigate the contribution from high-order multipole amplitudes PRD84, (2011)  c0  c2  +  -  K + K - 21

Higher-order Multipole in  c2,  c2  +  -,K + K  PRD84, (2011) Extract M2 using fit to full angular distribution Evidence of M2 contribution:  c2  +  -,  c2  K + K - 22

23 We are measuring BRs at PRL105, (2010) Evidence for  decays into   and 

Some surprises 24 PRL105, (2010) Q. Zhao, PLB697(2011)52

Evidence  cJ  VV First observation PRD (2010), PRD (2010)  (KK)  (3  )   PRL107, (2011) 25

 c0/2  PRD85, , (2012) f2f2 f0f0 Helicity configuration γ(λ1) γ(λ2) χ c2

 cJ → π+π+η c (η c → KKπ) Search for  cJ → π+π+η c (η c → KKπ) (Preliminary results) K S Kπ) M(K S Kπ)  c0  c1  c2 KKπ 0 ) M(KKπ 0 90% C.L.

→ Observation of e + e - → η GeV (Preliminary results) Data: 477pb GeV First observation of e+e- → ηJ/Ψ Assumption of ηJ/Ψ signal is from C.L. J/   e + e - J/    +  -

Charm as a tool to study light hadron spectroscopy 29

Observation of X(pp bar BESII 30 M=1859 MeV/c 2 Γ < 30 MeV/c 2 (90% CL)  10  25 PRL 91 (2003) Theoretical interpretation:  conventional meson?  ppbar bound state/multiquark  glueball  Final state interaction (FSI)  …

BESIII and CLEOc 31 M= MeV/c 2 Γ < 38 MeV/c 2 (90% CL) Chinese Physics C 34, 421 (2010) Fit with one resonance at BESII did: PRD 82, (2010) CLEOcBESIII

Several non-observations 32 PRD 73 (2006) PRL 99 (2007) PRD 82 (2010) EPJC 53 (2008) 15 Pure FSI interpretation is disfavored

Spin-parity, mass, width and B.R. of X(pp bar ): PWA 33 >6.8 σ better than other J pc assignments PWA of J/ψ  γpp bar was first performed The fit with a BW and S-wave FSI(I=0) factor can well describe ppb mass threshold structure. It is much better than that without FSI effect, and Δ2lnL=51 (7.1σ ) Different FSI models  Model dependent uncertainty PRL 108,112003(2012)

M ppbar threshold structure 34 Obviously different line shape of ppbar mass spectrum near threshold from that in J/ψ decays PWA Projection:PWA results: Significance of X(pp bar ) is > 6.9 σ. The production ratio R: It is suppressed compared with “12% rule”. first measurement PRL 108,112003(2012)

Confirmation of X(1835) and two new structures Resonance M( MeV/c 2 )  ( MeV/c 2 )Stat.Sig. X(1835)1836.5± ± >20σ X(2120)2122.4± ± σ X(2370)2376.3± ± σ 35 X(1835) consistent with 0  +, but the others are not excluded PRL 95,262001(2005) BESIII fit results: BESII PRL 106, (2011) f1(1510) two news! An amplitude analysis could help with interpretation for the additional new structures! J/   +     +     BESIII: 225M J/  events, new structures!

What’s the nature of new structures? 36 PRD73,014516(2006) Y.Chen et al 0  + : 2560(35)(120) 2 ++ : 2390(30)(120) It is the first time resonant structures are observed in the 2.3 GeV/c2 region, it is interesting since: LQCD predicts that the lowest lying pseudoscalar glueball: around 2.3 GeV/c 2. J/  -->    ' decay is a good channel for finding 0 -+ glueballs. Nature of X(2120)/X(2370) pseudoscalar glueball ?  /  excited states? PRD82,074026,2010 J.F. Liu, G.J. Ding and M.L.Yan PRD83:114007,2011 (J.S. Yu, Z.-F. Sun, X. Liu, Q. zhao),J.S. YuZ.-F. SunX. Liu zhao and more… For detail see Light meson session: Hongwei Liu’s talk on June 17

X(1870) in J/   X, X  a 0 (980)  37 M(a 0 (980)  )M(   +   ) non-a 0 (980) M(   +   )M(    ) a 0 (980) J/     +  , a 0 (980) reconstructed in    f 1 (1285)  (1405) BR(J/   X, X  ) Identification of X(1870): 0  + (?) It is X(1835)? Need PWA! X(1870): 7.2  PRL 107, (2011)

Anomalous line shape of f 0 (980) in J /  3  38 f 0 (980)  +  - f 0 (980)  0  0 PRL 108, (2012)

 (1405) in J /  f 0 (980)  0, f 0 (980)  2  39 f 0 (980)  +  - f 1 /  3.7  f 1 /  1.2  First observed:  (1405)  f 0 (980)  0 (Large isospin breaking): f 0 (980)  0  0 a 0 -f 0 mixing alone can not explain the branching ratio of  (1405) ∨ PRD, 83(2100) PRL 108, (2012)

Large isospin violation in  (1405) decay 40 In general, magnitude of isospin violation in strong decay should be less than 1% or at 0.1% level. For example: Triangle Singularity (TS) a 0 —f 0 mixing J.J.Wu et al, PRL 108, (2012) K*K pair in TS is almost on-shell, together with mixing explain the narrow f 0 (980), and large isospin violation. However:

First observed f 0 (1710) from J/  radiative decays to  by Crystal Ball in LQCD predicts: Study of  system 41 Crystal Barrel Collaboration (2002) analyzed the three final states  0  0  0,  0  0 and  0  with K matrix formalism. Found a 2 ++ (~1870MeV), but no f 0 (1710). E835 (2006): ppbar   0 , found f 0 (1500) and f 0 (1710). WA102 and GAMS all identified f 0 (1710) in .

Preliminary PWA results of J/ψ  42 f 0 (1710) and f 0 (2100) are dominant scalars. f 0 (1500) exists (8.2 σ ). f 2 ’(1525) is the dominant tensor.

M ωΦ threshold enhancement in J/ψ  γωφ 43 PRL 96(2006) For X(1810): J pc favors 0 ++ over 0 -+ and 2 ++ BESII

Preliminary PWA results of J/ψ  44 Is X(1810) the f0(1710)/f0(1790) or new state?

Observation of two N* baryons in  π 0 p  p decay arXiv: Non-relativistic quark model is successful in interpreting of the excited baryons Predicted more excited stated (“missing resonance problem”) J/  (  ’) decays offers an window to search for the missing resonance

46 Two new baryonic excited states are observed ! PWA results on N* baryons in  π 0 p  p

47 Preliminary results on N* baryon in  p  p decay Br(  '  pp  )=(6.6  0.2  0.6)  10  5 Br(  '  N(1535)p)  Br(N(1535)  p  +c.c.) PDG2010: (6.0  1.2)  10  5 = N(1535) M(p  ) M(pp) Dalitz plot data Dalitz plot MC fit A full PWA is performed. Background clean! N(1535) is 1/2  Mass: Width: GeV/C 2 GeV BESIII Preliminary

e + e  Good for charm flavor physics: Threshold production: clean Known initial energy and quantum numbers Both D and  D fully reconstructed (double tag) Absolute measurements 48 Charm physics at BESIII

 D + leptonic decays play an important role in understanding of the SM  Test LQCD calculation of f D 49 D+→μ+νD+→μ+ν  Precise measurement of |V cd |  Theoretical uncertainty will be reduced in determination of |V ud | If FF calculations can be validated with charm  Reduced width of band in triangle would lead to precisely test the SM, and search for new physics beyond the SM

In the system recoiling against the singly tagged D -, BES-III selected the purely leptonic decay events for D 0  μ + 50

51

D 0 tag e+e+ K-/π-K-/π- D 0  K  /   e + BESIII, ~2.93 fb-1 data taken at ψ(3770), ~923 pb-1 analyzed signal side: missing neutrino inferred 52 U k (GeV) U π (GeV) D 0  K  e + D 0    e + ν

53 D 0   B(D 0 →γγ)/B(D 0  π 0 π 0 )<5.8×10 CL, with PDG value: B(D 0  π 0 π 0 )=8×10 -4, BESIII: B(D 0  γγ))<4.6×10 CL. BaBar: B(D 0  γγ)<2.2×10 CL. B(D 0  γγ ) Theoretical predictions: SM (short distance)~ Long distance ~10 -8

Summary

Thank you ! 55

56 Sum of 16 of  C decay modes Background subtracted The  C lineshape is not distorted in the h C  C Detail analysis of  c parameters is ongoing! Asymmetric lineshape in  decay Symmetric lineshape in  production  C lineshape from   0 h C, h C  C