N production from j decays at bes
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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). 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

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N production from j decays at bes

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

Outline

  • Introduction

  • Baryon program at BES

  • N* in the decay of

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

  • Summary

QCD and Light Hadrons


N production from j decays at bes

The Beijing Electron Positron Collider

L ~ ~51030 /cm2s at J/ peak

Ecm~2-5 GeV

QCD and Light Hadrons


N production from j decays at bes

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

Study of Excited Baryon States

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

QCD and Light Hadrons


N production from j decays at bes

J/ decays

  • relatively large branching ratios (PDG2004)

QCD and Light Hadrons


N production from j decays at bes

  • Pure isospin 1/2

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

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

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 production from j decays at bes

N*(1520)

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+

QCD and Light Hadrons


N production from j decays at bes

N* in

BES II Preliminary

Dalitz Plot:

Acceptance and other

reasons make the plot

asymmetry.

QCD and Light Hadrons


N production from j decays at bes

N* in

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

BES II Preliminary

QCD and Light Hadrons


N production from j decays at bes

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 production from j decays at bes

N* in

BES II Preliminary

BES II Preliminary

QCD and Light Hadrons


From bes ii data1

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 data2

N*(1535)?

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

QCD and Light Hadrons


From bes ii data3

BES II Preliminary

from BES II data

PWA is being performed

QCD and Light Hadrons


Summary

Summary

  • 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

QCD and Light Hadrons


N production from j decays at bes

Thank You!

QCD and Light Hadrons


N production from j decays at bes

“Missing” N* Problem Capstick et al.

QCD and Light Hadrons


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