Evidence for a new resonance *(1380) with JP =1/2

JiaJun WU

In collaboration with S. Dulat and B. S. ZOU

Introduction.First evidence from pat Plab

GeV.Second evidence from pat Plab

GeV.Summary.

Introduction

The classical constituent quark models are based on the assumption of three constituent quarks inside each baryon.

The lowest excitation of baryons is the orbital angular momentum L =1 excitation of a quark, resulting to spin parity 1/2.

There are many problems of these quark models. Next we will give two examples.

u /d asymmetry in the proton

The number of d is more thanu:

d u =0.12

This result demands its 5-quark components to be at least 12%.

meson cloudpenta-quark

u

du

SS

Su

uS

d

G. T. Garvey and J. C. Peng, Prog. Part. Nucl. Phys. 47,203 (2001),

N. Kaiser, P. B. Siegel, and W. Weise, PLB 362,23 (1995).

D. Jido, J. A. Oller, E. Oset, A. Ramos, and U. G.Meissner, NPA725, 181 (2003).

C. Helminen and D. O. Riska, NPA699, 624(2002).

S. L. Zhu, etc. High Energy Phys. Nucl. Phys. 29, 250(2005).

B. S. Zou, EPJA35, 325 (2008).

N*(1535) ~ [ud][us]s*(1405) ~ [ud][su]u

The mass order reverse problem

In the constituent quark models

N*(1535) ~ uud (L=1)*(1405) ~ uds (L=1)

In the penta-quark models

N*(1535) ~ *(1405) ~ KN

In the meson cloud models

The prediction of 5-quak model

* [us][ds]s ~ 1575 MeV

* [us][du]d ~ 1360 MeV

* [us][ds]u ~ 1520 MeV

Capstick 3q model

First evidence from pat Plab GeV.

1 2

2 2 2 2 21 ( )

ni

i i i i

dNp p

dm

a

m m m

D. O. Huwe, Phys. Rev. 181, 1824 (1969).

p1 is module of 3-momentum of in the C.M..

p2 is module of 3-momentum of in the rest system of *.

Jia-Jun Wu, S. Dulat and B. S. ZouPHYSICAL REVIEW D 80, 017503 (2009)

93% *(3/2+)+7% background

ndf=10.1 / 9)

58% *(3/2)+ 37% *(1/2)+ 5% background

(2/ndf=3.2 / 9)

1.For M in the range of 1340-1430 MeV.

2.The range of beam momen-tum is 1–1.45 GeV.

3.Cos(.K) > 0.95

For *(3/2+): (1+ 3cos2)/2

For *(1/2-) and background: 1Robert K. Adair, Phys. Rev. 100, 1540 (1955).

D. O. Huwe, PR 181, 1824 (1969).

Second evidence from pat Plab GeV.

T. S. Mast, and R. D. Tripp et al., PRD 7, 5 (1973).M. B. Watson and R. D. Tripp et al., PR 131, 2248 (1963).R. Armenteros et al., Nucl. Phys. B 21, 15 (1970).

The theoretical mechanisms

From the picture, the result of our calculation is very close to the experiment points at the range of *(1520).

Jia-Jun Wu, S. Dulat and B. S. ZouarXiv: 0909, 1380

100% *(3/2+)

60% *(3/2)+ 40% *(1/2)

Phase space

First reason: S-wave between the *3/2+) and but P-wave between the *(1/2) and .

Second reason: the width of *3/2+) is 35.5MeV; but that of *(1/2) is 118.6MeV from fit before.

T. S. Mast, and R. D. Tripp et al. PRD 7, 5 (1973).

Summary

We find some evidence that a new resonance *(1/2) exists in the K-p reaction.

Higher statistic data experiments are necessary to establish this new resonance and to understand its property.

Thank you