Study of New Hadron Spectroscopy at BESIII Liu Fang (IHEP) for BESIII Collaboration The 9th National Workshop for Heavy Flavors and CP Violation 2011.10.12-10.16 Hangzhou, Zhejiang, China

OUTLINE Latest results on new hadron spectroscopy Introduction pp mass threshold enhancement in J/ and ’ radiative decays Confirmation of X(1835) and observation of two new structures Observation X(1870) in J/(+-) Summary

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

BEPCII storage rings Beam energy: 1.0-2.3 GeV Design 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 Circumference： 237m

BES Detector

Data samples So far BESIII has collected : BESIII will also collect: 2009: 225 Million J/(4 BESII) 2009: 106 Million ’ (4 CLEOC) 2010-11: 2.9 fb1 (3770) (3.5  CLEO-c 0.818fb1) - May 2011: 0.5fb1 @4010 MeV (one month) for Ds and XYZ spectroscopy BESIII will also collect: more J/, ’, (3770) data at higher energies （for XYZ searches, R scan and Ds physics）

Light hadron QCD allows different type of hadrons:

Observation of pp mass threshold enhancement @BESIII @BESIII @BESIII

Observation of mass threshold enhancement @ BESII 3-body phase space BESII X(1860) theoretical speculation: bound state (baryonium) FSI effect …… 0.1 0.2 0.3 acceptance Mpp-2mp (GeV) +3 +5 -10 -25 M=1859 MeV/c2 G < 30 MeV/c2 (90% CL) PRL 91 (2003) 022001 10 10

Several non-observations PRD 73 (2006) 032001 EPJ C53 (2008) 15 No significant signal of X(1860) near threshold found (only 2 significance) PRL 99 (2007) 011802 Mpp (GeV) 11 11

Observation of pp mass threshold enhancement at BESIII 0.1 0.2 0.3 +3 +5 -10 -25 M=1861 +6 -13+7-26 MeV/c2 G < 38 MeV/c2 (90% CL) M=1859 MeV/c2 G < 30 MeV/c2 (90% CL) PRL 91 (2003) 022001 Chinese Physics C 34, 421 (2010)

PWA on the pp mass threshold structure in BESIII X(pp) Preliminary results ηc Evident narrow ppbar mass threshold enhancement Partial Wave Analysis (PWA): Concentrate on dealing with the mass threshold structure, especially to determine the JPC (M(pp)<2.3GeV) . Convariant tensor amplitudes (S. Dulat and B. S. Zou, Eur.Phys.J A 26:125, 2005). Include the Juich-FSI effect (A. Sirbirtsen et al. Phys.Rev.D 71:054010, 2005). 13

PWA results and projections in Preliminary results

Measurement for X(1860) >6.8σ better than other Jpc assignments. PWA results are carefully checked from different aspects: Contribution of additional resonances Solution with different combinations Different background levels and fitting mass ranges Different BW formula … … All uncertainties are considered as systematic errors Different FSI models Model dependent uncertainty Spin-parity, mass, width and B.R. of X(1860): Preliminary results >6.8σ better than other Jpc assignments.

PWA on the pp mass threshold structure in Preliminary results BESIII χcJ Obviously different line shape of ppbar mass spectrum near threshold from that in J/ψ decays ηc PWA results: PWA Projection: Significance of X(pp) is larger than 6.9σ. The production ratio R: It is suppressed compared with “12% rule”. first measurement

Confirmation of X(1835) in and observation of two new structures at BESIII

X(1835) at BESII PRL 95,262001(2005) LQCD predicts the 0-+ glueball mass is ~2.3GeV. A 0-+ glueball may have similar property as c (mainly decay into ). J/+- was studied with 58M J/@BESII Need to confirm X(1835) with BESIII ~225M J/ data !!! 18 18

Mass spectrum of X(1835) X(1835) and c are evident. BES III BES III Combination for  to +- and  X(1835) and c are evident. Two additional structures are observed at M~2.1GeV and 2.3GeV There maybe some f1(1510). X(2370) X(2120)

Fitting for the combined mass spectrum Fitting with four resonances (acceptance weighted BW gauss) Three background components: Contribution from non-h’ events estimated by h’ mass sideband Contribution from with re-weighting method Contribution from “PS background” Red line: estimated contribution of ①+ ② Black line: total background Stat. sig. is conservatively estimated: fit range, background shape, contribution of extra resonances BES III

X(1835) , X(2120), X(2370) at BESIII BESIII fit results: Resonance M( MeV/c2) ( MeV/c2) Stat.Sig. X(1835) 1836.5±3.0+5.6-2.1 190.1±9.0+38-36 >20σ X(2120) 2122.4±6.7+4.7-2.7 83±16+31-11 7.2σ X(2370) 2376.3±8.7+3.2-4.3 83±17+44-6 6.4σ For the X(1835): BESIII X(1835) consistent with 0+ PWA is needed to understand these structures. 21

Summary of X(1835), X(2120) & X(2370) in J/(’+-) X(1835) resonance is confirmed at BESIII, but the width is significantly larger than that measured at BESII with one resonance in the fit. Two new resonances, X(2120) and X(2370), are observed with significances larger than 7.2 and 6.4 respectively. PWA is needed not only to determine the spin-parities of above three resonances, but also to make more precise measurements on masses, widths and BRs by considering possible interferences among them.

Observation X(1870) in J/X, Xa0(980)(+-) X(1835) observed at BESII and then confirmed at BESIII in J/→γπ+π-η´ theoretical interpretations: pseudoscalar glueball, / excited states .. study of its production in hadronic decays to our surprise, we observed a new structure around 1.87 GeV

X(1870) in J/X, Xa0(980) a0(980) In addition to the well-known ’, f1(1285) and (1405), an unknown structure (denoted as X(1870)) around 1.87GeV/c2 is observed. The f1(1285), (1405) and X(1870) primarily decay via a0(980)± mode. M(+) M() With a0(980): Veto a0(980): M(+) non-a0(980) M(a0(980))

Fitting results of X(1870) Fitting with three resonances (acceptance weighted BW Gauss) Background component described by Polynomial function X(1870): 7.2 f1(1285) (1405) Contribution from non- and/or non-a0(980) BG events Contribution from J/b1(1235)a0(980) Contribution from “PS” process of J/a0(980) M(a0(980)) BR(J/X, X )

Summary of X(1870) in J/(+-) BESIII arxiv :1107.1806 Accepted by PRL.

Summary and Prospects Huge data samples collected for charmonium decays at BESIII. A lot of results have been obtained, The spin-parity of the pp mass threshold enhancement in J/γ pp was first determined as 0-+ Confirmation of X(1835) in J/  + and observation of two new structures X(2120) and X(2370) in J/   decays Observation of new structure X(1870) in J/ We expect more exciting results in the coming years from BESIII.

many thanks for your attention !