Study Of Baryons Research Articles

Stringy excited baryons in holographic quantum chromodynamics

Abstract We analyze excited baryon states using a holographic dual of quantum chromodynamics that is defined on the basis of an intersecting D4/D8-brane system. Studies of baryons in this model have been made by regarding them as a topological soliton of a gauge theory on a five-dimensional curved spacetime. However, this allows one to obtain only a certain class of baryons. We attempt to present a framework such that a whole set of excited baryons can be treated in a systematic way. This is achieved by employing the original idea of Witten, which states that a baryon is described by a system composed of $N_c$ open strings emanating from a baryon vertex. We argue that this system can be formulated by an Atiyah–Drinfeld–Hitchin–Manin-type matrix model of Hashimoto–Iizuka–Yi together with an infinite tower of the open string massive modes. Using this setup, we work out the spectra of excited baryons and compare them with the experimental data. In particular, we derive a formula for the nucleon Regge trajectory assuming that the excited nucleons lying on the trajectory are characterized by the excitation of a single open string attached on the baryon vertex.

The Strong Three-body Weak Interaction Contribution in the Nonmesonic Weak Decay of p-shell Λ Hypernuclei

The fundamental motivation to study the non-mesonic weak decay (NMWD) of hypernuclei is that it provides the unique means for study of baryon–baryon weak interaction in SU3f symmetry group. The new channel of NMWD, namely the recently confirmed three-body channel, seems to have a surprisingly big branching ratio so that it makes its accurate measurement prerequisite of the baryon–baryon weak interaction study. We report a new result of \({\Gamma_{2N}(^{11}_{\Lambda} {\rm B})}\) from E508 experiment of KEK-PS, though preliminary yet, which agrees with the previous result of \({^{12}_{\Lambda}}\) C from the same experiment, those from FINUDA experiment and those of the recent theoretical predictions.

All you need isN: Baryon spectroscopy in two largeNlimits

The generalization of QCD to many colors is not unique; each distinct choice corresponds to a distinct $1/{N}_{c}$ expansion. The familiar 't Hooft ${N}_{c}\ensuremath{\rightarrow}\ensuremath{\infty}$ limit places quarks in the fundamental representation of $\mathrm{SU}({N}_{c})$, while an alternative approach places quarks in its two-index antisymmetric representation. At ${N}_{c}=3$ these two $1/{N}_{c}$ expansions coincide. We compare their predictions for certain observables in baryon spectroscopy, particularly mass combinations organized according to SU(3) flavor breaking. Each large ${N}_{c}$ limit generates an emergent spin-flavor symmetry that leads to the vanishing of particular linear combinations of baryon masses at specific orders in the expansions. Experimental evidence shows that these relations hold at the expected orders regardless of which large ${N}_{c}$ limit one uses, suggesting the validity of either limit in the study of baryons. We also consider a hybrid large ${N}_{c}$ limit in which one flavor is taken to transform in the two-index antisymmetric representation and the rest of the flavors are in the fundamental representation. While this hybrid large ${N}_{c}$ limit is theoretically attractive, we show that for a wide class of observables it faces some phenomenological difficulties.

BARYONS WITH HOLOGRAPHY

We perform the first study of baryons in holographic QCD with [Formula: see text] multi-D-brane system in type IIA superstring theory. The baryon is described as a chiral soliton solution in the four-dimensional meson effective action derived from holographic QCD. We also present a brief review of the holographic model from the viewpoints of recent hadron physics and QCD phenomenologies.

Study of baryon and search for dibaryon resonances by the $pp \rightarrow pp\pi^ + \pi^-$ reaction

Exclusive measurements of the two-pion production channel $pp \rightarrow pp\pi^ + \pi^-$ have been carried out near threshold at CELSIUS with the PROMICE/WASA detector. They reveal $pp \rightarrow pp^*(1440)\rightarrow pp\sigma \rightarrow pp(\pi^ + \pi^-)_{I = \ell = 0}$ as the dominant process at these energies, however, the data exhibit also significant contributions from $p^*(1440) \rightarrow \Delta \pi \rightarrow p(\pi^ + \pi^-)_{I = \ell = 0}$ . From the observed interference of these Roper decay routes their relative branching ratio is derived. The status on the search for NN-decoupled $NN\pi$ -resonances is reviewed with regard to recent experimental searches in the pionic double charge exchange in nuclei, the two-pion production in nucleon-nucleon collisions, the photo pion-production on the deuteron and the electro pion-production in nuclei.

Study of baryon and lepton violating two-proton annihilation in gauge theories

The baryon and lepton violation process ( A, Z) → ( A − 2, Z − 2) + e + + e + is investigated within the framework of two gauge models recently proposed. One is an SU L(2) × U(1) × SU C(3) model extended to include two isospin triplets which couple to quarks and leptons. The second is an extension of the minimal GUT SU(5) model to include a 45-plet and a 50-plet of Higgs scalars. With a reasonable choice of the parameters of these models and a proper treatment of nuclear physics, mean lifetimes of 10 33 yr may be expected.