Charm Baryon Spectroscopy at J-PARC

Introduction

What are essential degrees of freedom in hadrons? This is a fundamental question in hadron physics. Quarks are thought to be the most fundamental building blocks to form hadrons. The principle to describe the dynamics of quarks is known as the Quantum Chronodynamics (QCD), althoguh it is difficult to solve the equation in low energy because of its non-perturbative nature. Due to their strong interaction, quarks are confined in hadrons.

The quark model well describes the properties of hadrons, where the model treats "dressed" quarks (constituent quark model: CQM). The CQM is successful particularly in ground state hadrons, explaining classification based on spin/flavor symmetry, mass relations, magnetic moments of baryons, and so on. But the CQM sometimes fails in excited states. There remain many undiscovered states, which is known as the so-called missing resonance problem in the CQM. The mass order of resonances, i.e. the N*(1440)1/2+, and/or \Lambda(1405)1/2- state, is not clearly explained.

Exotic states

These suggest new effective degrees of freedom to describe hadrons. Through studies of hadrons, we will attack a mystery of the origin to form the matter in the universe.

In order to answer the above-mentioned questions in hadron physics, we need to understand the interaction between quarks in hadrons further. In particular, quark-quark correlation, namely diquark correlation, in a baryon is of interest. In light baryons, where flavor SU(3) symmetry seems to work rather well, 3 quark-quark pairs are expected to be correlated each other on equal foot. Extraction of a diquark correlation may not be easy.

Baryons with a heavy quark provide unique opportunities to study diquark correlation. Magnitude of the color-spin interaction between quarks is proportional to the inverse of the quark mass. One expects that the

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