N* Production from J/ decays at BES Ji Xiaobin IHEP, Beijing (Representing BES Collaboration) Sep.26 - 30, 2004 QCD and Light Hadrons (Beijing, China)

Outline Introduction Baryon program at BES N* in the decay of N* and * in the decay of and others Summary QCD and Light Hadrons

The Beijing Electron Positron Collider L ~ ~51030 /cm2s at J/ peak Ecm~2-5 GeV QCD and Light Hadrons

BESII Detector 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=1.78%(1+p2) z = 3.1 cm QCD and Light Hadrons

Study of Excited Baryon States Motivation Probe the internal structure of light quark baryons Search for missing baryons predicted by quark model Obtain a better understanding of the strong interaction force in the non-perturbative regime QCD and Light Hadrons

relatively large branching ratios (PDG2004) J/ decays relatively large branching ratios (PDG2004) processes branching ratios(10-3) N* decays 1.10.1 6.00.5 2.00.1 2.10.2 0.90.4 1.30.3 QCD and Light Hadrons

Pure isospin 1/2 For and , N Feynman diagram of the production of For and , N and N systems are limited to be pure isospin 1/2. QCD and Light Hadrons

from BES II data Events selection 2 good charged tracks Q1+Q2 = 0 |cos| < 0.8 PID: TOF and dE/dx Mp > 1.15 GeV 0.88<Mmiss<1.0 GeV QCD and Light Hadrons

Background Analysis Estimate the background from the fitting of the data The Monte Carlo of J/ inclusive decay is also used in the background analysis Background < 8% QCD and Light Hadrons

N* in ? L=0 limits it to be BES II Preliminary 3/2+ or 1/2+ N*(1520) QCD and Light Hadrons

N* in Dalitz Plot: BES II Preliminary Acceptance and other reasons make the plot asymmetry. QCD and Light Hadrons

N* in Fitting formular k : momentum of anti-neutron q : proton momentum in Mx frame BES II Preliminary QCD and Light Hadrons

N* in Preliminary results: Possible new N* resonance L=0 limits it to be 3/2+ or 1/2+ Detailed information need PWA QCD and Light Hadrons

N* in BES II Preliminary BES II Preliminary QCD and Light Hadrons

from BES II data Events selection 4 good charged tracks PID: kaon and at least 1 proton ID 2 (4C)<20 QCD and Light Hadrons

from BES II data BES II Preliminary *(1520) *(1690) PS, eff. corrected (Arbitrary normalization) BES II Preliminary Two clear peaks at 1520, 1690 MeV/c2 in pK mass N* in K mass PWA is being performed QCD and Light Hadrons

from BES II data BES II Preliminary PWA is being performed QCD and Light Hadrons

Summary BES II preliminary results: A possible “missing” N* is found PWA to BESII 58M data is in progress Clear two peaks around 1520, 1690 in pK mass N* in K mass PWA is being performed Similar structure with PWA is in progress QCD and Light Hadrons

Thank You! QCD and Light Hadrons

“Missing” N* Problem Capstick et al. QCD and Light Hadrons