相关论文: Partners of the Theta^+ in Large N_c QCD

We estimate the mass of the pentaquark state with QCD sum rules and find that pentaquark states with isospin $I=0, 1, 2$ lie close to each other around $(1.55\pm 0.15)$ GeV. The experimentally observed baryon resonance $\Theta^+ (1540)$…

Recent experimental evidence for the Theta^+(1540) has given rise to much theoretical interest in exotic baryons. The Theta^+ is a baryon that has strangeness S=+1, meaning that it contains an anti-strange quark. Thus it cannot be…

Since LEPS collaboration reported the first evidence of $\Theta^+$ pentaquark in early 2003, eleven other experimental groups have confirmed this exotic state while many other groups didn't see any signal. If this state is further…

Exotic penta-quark baryon with strangeness +1, \Theta^+, is studied in the QCD sum rule approach. We derive sum rules for the positive and negative parity baryon states with J=1/2 and I=0. It is found that the standard values of the QCD…

Motivated by the recent discovery of the exotic S=+1 narrow baryon resonance Theta^+ at 1540 MeV, with quark content {uudd sbar}, we conjecture the existence of its anti-charmed analogue Theta_c, with quark content {uudd cbar}, and compute…

A narrow resonance peak was observed at 1.54 +/- 0.01 GeV as an exotic baryon with strangeness S = +1 in the gamma + n going to K^+ + K^- + n reaction on Carbon. The new state have a width smaller than 0.025 GeV and a Gaussian significance…

Predictions for a light collective $\Theta^+$ baryon state (with strangeness +1) based on the collective quantization of chiral soliton models are shown to be inconsistent with large $N_c$ QCD. The lightest strangeness +1 state to emerge…

There are experimental evidences for the existence of narrow states $\Theta^+$ and $\Theta_c$ with the same quantum numbers of $uudd\bar s$ and $uudd\bar c$ pentaquarks and also $NK^{(*)}$ and $ND^{(*)}$ molecular states. Their masses…

It has been ten years since the first report for a positive strangeness pentaquark-like baryon state. However the existence of the pentaquark state is still controversial. Some contradictions between the experiments are unsolved. In this…

Recently, the 1/Nc expansion has been applied to the study of exotic baryons containing both quarks and antiquarks. We extend this approach to exotic states with mixed symmetric spin-flavor symmetry, which correspond in the quark model to…

Evidence for the $\Theta^+$ pentaquark is still sketchy at the present time. This state, if it exists, has a small width and consequently a small production cross section. No single experiment has overwhelming evidence for the $\Theta^+$…

Exotic multi-quark states are examined in the quark model and in QCD. Current status of theoretical studies of the pentaquark Theta^+ is reported. We show recent analyses of multi-quark components of baryons. A novel method to extract a…

The 1/N expansion for exotic baryons is developed, and applied to the masses, meson couplings and decay widths. Masses and widths of the 27 and 35 pentaquark states in the same tower as the Theta+ are related by spin-flavor symmetry. The 27…

Motivated by the recent experimental evidence of the exotic B = S = +1 baryonic state Theta(1540), we examine the older existing data on K+ N elastic scattering through the time delay method. We find positive peaks in time delay around…

We extend the recently developed treatment of baryon resonances in large N_c QCD to describe resonance multiplets collected according to the SU(3) flavor symmetry that includes strange quarks. As an illustration we enumerate the SU(3)…

In view of the renewing experimental interest for searching strangeness $+1$ baryons at J-PARC, we study the existence of light baryon resonances with strangeness +1 generated in the $K$-$(N^*/\Delta^*)$ system, where $N^*$ represents…

A light collective theta+ baryon state (with strangeness +1) was predicted via rigid-rotor collective quantization of SU(3) chiral soliton models. This paper explores the validity of this treatment. A number of rather general analyses…

We examine several assignments of spin and parity for the pentaquark Theta+ state (J^P=1/2^{+,-}, 3/2^{+,-}) in connection with known baryon resonances. Assuming that the Theta+ belongs to an antidecuplet representation which mixes with an…

We examine several assignments of spin and parity for the pentaquark Theta+ state (J^P=1/2^{+,-}, 3/2^{+,-}) in connection with phenomenology of known baryon resonances, using a general framework based on the flavor symmetry. Assuming that…

The novel observation of an exotic strangeness S=+1 baryon state at 1.54 GeV will trigger an intensified search for this and other baryons with exotic quantum numbers. This state was predicted long ago in topological soliton models. We use…