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# N* Production from J/  decays at BES - PowerPoint PPT Presentation

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

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### N* Production from J/ decays at BES

Ji Xiaobin

IHEP, Beijing

(Representing BES Collaboration)

Sep.26 - 30, 2004

QCD and Light Hadrons (Beijing, China)

• Introduction

• Baryon program at BES

• N* in the decay of

• N* and * in the decay of and others

• Summary

L ~ ~51030 /cm2s at J/ peak

Ecm~2-5 GeV

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

Motivation

• Probe the internal structure of light quark baryons

• Search for missing baryonspredicted by quark model

• Obtain a better understanding of the strong interaction force in the non-perturbative regime

J/ decays

• relatively large branching ratios (PDG2004)

Feynman diagram of the production

of

For and , N

and N systems are limited to be pure isospin 1/2.

• 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

• 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%

N*(1535)

N*(1650)

N*(1675)

N*(1680)

N*(1440)

?

BES II Preliminary

N* in

L=0 limits it to be

3/2+ or 1/2+

BES II Preliminary

Dalitz Plot:

Acceptance and other

reasons make the plot

asymmetry.

Fitting formulark : momentum of anti-neutronq : proton momentum in Mx frame

BES II Preliminary

Preliminary results:

• Possible new N* resonance

• L=0 limits it to be 3/2+ or 1/2+

• Detailed information need PWA

BES II Preliminary

BES II Preliminary

Events selection

• 4 good charged tracks

• PID: kaon and at least 1 proton ID

• 2 (4C)<20

N*(1650)?

*(1520)

*(1690)

PS, eff. corrected

(Arbitrary normalization)

from BES II data

BES II Preliminary

• Two clear peaks at 1520, 1690 MeV/c2 in pK mass

• N* in K mass

• PWA is being performed

from BES II data

PWA is being performed

• A possible “missing” N* is found

• PWA to BESII 58M data is in progress

BES II preliminary results:

• Clear two peaks around 1520, 1690 in pK mass

• N*in K mass

• PWA is being performed

• Similar structure with

• PWA is in progress