Recent BESII Hot Topics Kanglin He (for BES Collaboration) IHEP, Beijing hekl@ihep.ac.cn FPCP08, Taipei, 5—9 May, 2008

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

BESII Data Samples √s J/y y´ y´´ data ~58M ~14M ~30pb-1 The construction of new machine/detector, BEPCII/BESIII are almost ready, we’re expected to get beam in the beginning of this June (see Dr. Yangheng Zheng’s talk for detail)

I will talk about Y(2175) in J/yhff0(980) h(2225) in J/ygff Board 1– resonance in J/yK+K-p0 KL mass threshold enhancement in J/ypKL , nKsL y´radiative decays

The Y(2175) Y(2175) f0(980) Babar measured e+e-→ +- and f0(980) observed the Y(2175) f0(980). L=232 fb-1 Y(2175) f0(980) J/ M = 2175 ± 10 MeV  = 58 ± 16 MeV Phys. Rev. D 76, 012008 (2007)

Y(2175) in J/ f0(980) Final states: , K+K-, f0(980)+- 58 M J/ decays Define , , f0(980) signal regions and sideband regions.

Y(2175) in J/ f0(980) Clear enhancement at around 2.2 GeV in f0(980) invariant mass, band shows in Dalitz plot. About 50% background!

Y(2175) in J/ f0(980) Simultaneous fit to signal and sideband events with BW+p3 ~5 M = 2186 ± 10 ± 6 MeV = 65 ± 23 ± 17 MeV B(J/Yf0(980) ) =(3.23 ± 0.75 ± 0.73)x10-4 Nature of the Y? Very likely it is an excited  state, Yf0(980) is an OZI allowed decay. arXiv: 0712.1143; PRL100, 102003 (2008)

(2225) in J/   MarkIII, PRL65 (1990)

(2225) in J/   Final states: 1K+K-, 2KSKL Signal and background in data sample.

(2225) in J/   Signal is very different from phase space distribution, enhancement close to threshold. Fit with a pseudoscalar state is better than scalar or tensor. Phase space MC

(2225) in J/   In good agreement with Mark-III measurement. Resonance parameters of a pseudoscalar: In good agreement with Mark-III measurement. arXiv: 0801.3885; PLB (in press)

J/ K+K-0 0 background ? 0 sideband X(1580) PID and kinematic fit can significantly reduce the dominant background from J/  + - 0.

What is this broad structure? JPC should be 1--, 3--, …(Parity conservation) PWA results Following components are needed K*(892), K*(1410), (1700), X 1– is much better than 3— Pole position of X is Big destructive interference among X, (1700) and PS 1-- component

Observation of a strong enhancement near the threshold of mass spectrum at BES II NX* BES II PS, eff. corrected (Arbitrary normalization)

BESII preliminary Best PWA fit: (JP=½- is favored) Fitted as N(1535) (becomes worse by about 5  (2=28 with d.o.f.=2)). Big Br. BESII preliminary

Nx* is N(1535)? From BESII measurements: If Nx* is N(1535), its coupling to K is much stronger than that to p. Then N(1535) would have very large ssbar component (a 5-quark system).

Observation of  BES II Preliminary KS

More statistics and PWA are needed for the detail information BES II Preliminary N* * An enhancement near S threshold is evident N* and * found in the S and nS spectrum More statistics and PWA are needed for the detail information

’ radiative decays Only limited modes measured by BESI , ’ [PRD58, 097101 (1998)] KK,  [PRD67, 032004 (2003)] Try to measure more modes B(’+X) 2-prong: +-, K+K-, ppbar, +- 4-prong:2(+-), +-K+K-, +-ppbar, 2(K+K-), KSK+-+c.c. 6-prong: 3(+-), 2(+-)K+K- Published in PRL99, 011802 (2007) PRD74, 072001 (2006)

Observation of ’ radiative decays Expected 1% BR, but only 0.05% observed. Potential channels for hadron spectroscopy study, including search for non-qqbar states, provided statistics is enough (BESIII?). ~ 0.1% more observed in this analysis. Mode BR (10-5) [m<2.9 GeV/c2]  pp-bar 2.9 ± 0.4 ± 0.4  ’ 12.6 ± 2.9 ± 1.5  2(+-) 39.6 ± 2.8 ± 5.0  KSK+-+c.c. 25.6 ± 3.6 ± 3.6  +-K+K- 19.1 ± 2.7 ± 4.3  +-ppbar 2.8 ± 1.2 ± 0.7  2(K+K-) < 4.0  3(+-) < 17  2(+-)K+K- < 22 PRL99, 011802 (2007)

’ +- and K+K- arXiv: 0710.2324 M(+-) Fit with incoherent BWs Mode BR (10-5) f2(1270) +- 22 ± 1 ± 2 f0(1500) +- 1.5 ± 0.7 +0.9-0.4 f0(1710) +- 2.4 ± 0.6 +0.8-1.1 f4(2050) +- 2.8 ± 0.9 +0.8-0.6 f0(2200) +- 4.6 ± 1.0 +4.5-0.9 f2(1270) K+K- 1.9 ± 0.6 +1.0-0.6 f’2(1525) K+K- 0.69 ± 0.44 +0.41-0.21 f0(1710) K+K- 3.1 ± 0.6 +1.1-0.7 M(+-) Fit with incoherent BWs ISR produced  and  consistent with prediction f2(1270) +- helicity amplitudes J/: x=0.89 y=0.46 M(K+K-)

Summary Thanks a lot ! Observation of Y(2175) in J/ decays. Measurement of (2225) resonance parameters. Observation of a board 1– resonance state X(1580) Observation of KL mass threshold enhancement Observation of new ’ radiative decay modes. Thanks a lot !