0000000000306296
AUTHOR
Atsushi Hosaka
showing 19 related works from this author
Quantum loops in radiative decays of the a1 and b1 axial-vector mesons
2007
A previous model where the low-lying axial-vector mesons are dynamically generated, implementing unitarity in coupled channels in the vector-pseudoscalar (V P) meson interaction, is applied to evaluate the decay widths of the a1(1260) and b1(1235) axial-vector mesons into �. Unlike the case of the a1, the b1 radiative decay is systematically underestimated at tree level. In this work we evaluate for the first time the loop contribution coming from an initial V P vertex. Despite the large superficial divergence of the loops, the convergence of the relevant loops can be established by using arguments of gauge invariance. The partial decay widths obtained agree with the experimental values wit…
Hidden gauge formalism for the radiative decays of axial-vector mesons
2009
24 pages, 6 tables, 11 figures.--ISI article identifier:000262979700040 .-- ArXiv pre-print avaible at:http://arxiv.org/abs/0809.0943
Λ(1405)production in theπ−p→K0πΣreaction
2003
We discuss the mechanisms that lead to $\ensuremath{\Lambda}(1405)$ production in the ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}^{0}\ensuremath{\pi}\ensuremath{\Sigma}$ reaction. The problem has gained renewed interest after different works converge to the conclusion that there are two resonances around the region of $1400\phantom{\rule{0.3em}{0ex}}\text{MeV}$, rather than one, and that they couple differently to the $\ensuremath{\pi}\ensuremath{\Sigma}$ and $\overline{K}N$ channels. We look at the dynamics of that reaction and find two mechanisms which eventually filter each one of the resonances, leading to very different shapes of the $\ensuremath{\pi}\ensuremath{\S…
Magnetic moments of theΛ(1405)andΛ(1670)resonances
2002
By using techniques of unitarized chiral perturbation theory, where the $\ensuremath{\Lambda}(1405)$ and $\ensuremath{\Lambda}(1670)$ resonances are dynamically generated, we evaluate the magnetic moments of these resonances and their transition magnetic moment. The results obtained here differ appreciably from those obtained with existing quark models. The width for the $\ensuremath{\Lambda}(1670)\ensuremath{\rightarrow}\ensuremath{\Lambda}(1405)\ensuremath{\gamma}$ transition is also evaluated, leading to a branching ratio of the order of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}.$
Determination of the axial coupling constant $g_{A}$ in the linear representations of chiral symmetry
2001
If a baryon field belongs to a certain linear representation of chiral symmetry of $SU(2) \otimes SU(2)$, the axial coupling constant $g_{A}$ can be determined algebraically from the commutation relations derived from the superconvergence property of pion-nucleon scattering amplitudes. This establishes an algebraic explanation for the values of $g_{A}$ of such as the non-relativistic quark model, large-$N_{c}$ limit and the mirror assignment for two chiral partner nucleons. For the mirror assignment, the axial charges of the positive and negative parity nucleons have opposite signs. Experiments of eta and pion productions are proposed in which the sign difference of the axial charges can be…
Decay of vector-vector resonances into $\gamma$ and a pseudoscalar meson
2010
We study the decay of dynamically generated resonances from the interaction of two vectors into a $\ensuremath{\gamma}$ and a pseudoscalar meson. The dynamics requires anomalous terms involving vertices with two vectors and a pseudoscalar, which renders it special. We compare our result with data on ${K}_{2}^{*+}(1430)\ensuremath{\rightarrow}{K}^{+}\ensuremath{\gamma}$ and ${K}_{2}^{*0}(1430)\ensuremath{\rightarrow}{K}^{0}\ensuremath{\gamma}$ and find a good agreement with the data for the ${K}_{2}^{*+}(1430)$ case and a width considerably smaller than the upper bound measured for the ${K}_{2}^{*0}(1430)$ meson. We also investigate the decay into ${\ensuremath{\pi}}^{+}\ensuremath{\gamma}$ …
Chiral Symmetry of Baryons
2001
We study chiral symmetry aspects of the positive and negative parity baryons by identifying them with linear representations of the chiral group $SU(N_{f}) \otimes SU(N_{f})$. It is shown that there are two distinctive schemes: naive and mirror assignments. We construct linear sigma models for baryons in the two assignments and examine their physical implications. Then we investigate properties of the naive and mirror nucleons microscopically by using QCD interpolating fields. Finally, we propose experiments to distinguish the two chiral assignments for the nucleon.
Two-meson cloud contribution to the baryon antidecuplet self-energy
2005
We study the self-energy of the SU(3) antidecuplet coming from two-meson virtual clouds. Assuming that the exotic Theta+ belongs to an antidecuplet representation with N(1710) as nucleon partner, we derive effective Lagrangians that describe the decay of N(1710) into N pi pi with two pions in s- or p-wave. It is found that the self-energies for all members of the antidecuplet are attractive, and the larger strangeness particle is more bound. From two-meson cloud, we obtain about 20 % of the empirical mass splitting between states with different strangeness.
Two-meson cloud contribution to the baryon antidecuplet binding
2004
We study the two-meson virtual cloud contribution to the self-energy of the SU(3) antidecuplet, to which the Theta+ pentaquark is assumed to belong. This is motivated by the large branching ratio of the N(1710) decay into two pions and one nucleon. We derive effective Lagrangians that describe the N(1710) decay into N-pi-pi with two pions in s or p wave. We obtain increased binding for all members of the antidecuplet and a contribution to the mass splitting between states with different strangeness which is at least 20 % of the empirical one. We also provide predictions for three-body decays of the pentaquark antidecuplet.
Determining the Θ+ quantum numbers through the K+p→π+K+n reaction
2004
Abstract We study the K+p→π+K+n reaction with some kinematics suited to the production of the Θ+ resonance recently observed. We show that, independently of the quantum numbers of the Θ+, a resonance signal is always observed in the K+ forward direction. In addition, we also show how a combined consideration of the strength at the peak, and the angular dependence of polarization observables can help determine the Θ+ quantum numbers using the present reaction.
Probing Chiral Symmetry of Nucleons by Threshold Production
2001
Double meson production of eta and pi mesons in the threshold region is investigated in order to determine chiral properties of the nucleon. The eta can be used as a probe for the negative parity nucleon N ∗ ≡ N ∗ (1535), produced in the intermediate state. The coupling of the low energy pion in the final state is then used to extract the sign of the Yukawa coupling, gπN∗N ∗ , which distinguishes the two realizations of chiral symmetry, naive and mirror, for the nucleon.
SU(3) Chiral approach to meson and baryon dynamics
1999
We report on recent progress on the chiral unitary approach, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV and meson baryon interaction up to the first baryonic resonances. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, concretely the K^- p\to\Lambda(1405)\gamma reaction and the N^\ast (1535)N^\ast(1535)\pi and \eta couplings.
Strategies for an accurate determination of the X(3872) energy from QCD lattice simulations
2014
We develop a method to determine accurately the binding energy of the X(3872) from lattice data for the DD* interaction. We show that, because of the small difference between the neutral and charged components of the X(3872), it is necessary to distinguish them in the energy levels of the lattice spectrum if one wishes to have a precise determination of the the binding energy of the X(3872). The analysis of the data requires the use of coupled channels. Depending on the number of levels available and the size of the box we determine the precision needed in the lattice energies to finally obtain a desired accuracy in the binding energy.
Photoproduction of K∗ for the study of Λ(1405)
2004
Abstract The photo-induced K ∗ vector meson production is investigated for the study of the Λ(1405) resonance. This reaction is particularly suited to the isolation of the second pole in the Λ(1405) region which couples dominantly to the K N channel. We obtain the mass distribution of the Λ(1405) which peaks at 1420 MeV, and differs from the nominal one. Combined with several other reactions, like the π−p→K0πΣ which favours the first pole, this detailed study will reveal a novel structure of the Λ(1405) state.
Substructure of Multiquark Hadrons (Snowmass 2021 White Paper)
2022
In recent years there has been a rapidly growing body of experimental evidence for existence of exotic, multiquark hadrons, i.e. mesons which contain additional quarks, beyond the usual quark-antiquark pair and baryons which consist of more than three quarks. In all cases with robust evidence they contain at least one heavy quark Q=c or b, the majority including two heavy quarks. Two key theoretical questions have been triggered by these discoveries: (a) how are quarks organized inside these multiquark states -- as compact objects with all quarks within one confinement volume, interacting via color forces, perhaps with an important role played by diquarks, or as deuteron-like hadronic molec…
Lambda(1405) production in the pi-p -> K-0 pi Sigma reaction
2003
We discuss the mechanisms that lead to Lambda(1405) production in the pi(-)p-->K(0)piSigma reaction. The problem has gained renewed interest after different works converge to the conclusion that there are two resonances around the region of 1400 MeV, rather than one, and that they couple differently to the piSigma and (K) over barN channels. We look at the dynamics of that reaction and find two mechanisms which eventually filter each one of the resonances, leading to very different shapes of the piSigma invariant mass distributions. The combination of the two mechanisms leads to a shape of this distribution compatible with the experimental measurements.
Coupling of (K)over-bar(*)N to the Lambda(1520)
2006
We study the coupling of the Λ(1520)≡Λ* resonance to the K* vector meson and nucleon. This coupling is not directly measured from the resonance decay, but is expected to be important in hyperon production reactions, in particular for the exotic Θ+ production. We compute the coupling in two different schemes, one in the chiral unitary model where the Λ* is dominated by the quasibound state of mesons and baryons, and the other in the quark model where the resonance is a p-wave excitation in the three valence quarks. Although it is possible to construct both models such that they reproduce the KN and πΣ decays, there is a significant difference between the Λ*K*N couplings in the two models. In…
Chiral unitary approach to the pi N*N*, eta N*N* couplings for the N* (1535) resonance
2000
Using a chiral unitary model in which the negative parity nucleon resonance N∗≡N∗(1535) is generated dynamically by means of the Bethe Salpeter equation with coupled meson baryon channels in the S=0 sector, we have obtained the π0N∗N∗ and ηN∗N∗ couplings. The π0N∗N∗ coupling has smaller strength and the same sign as the π0NN coupling. This rules out the mirror assignment of chiral symmetry where the ground state nucleon N and the negative parity resonance N∗ are envisaged as chiral partners in the baryon sector.
Photoproduction of $K^*$ for the study of $\Lambda(1405)$
2004
The photo-induced $K^*$ vector meson production is investigated for the study of the $\Lambda(1405)$ resonance. This reaction is particularly suited to the isolation of the second pole in the $\Lambda(1405)$ region which couples dominantly to the $\bar K N$ channel. We obtain the mass distribution of the $\Lambda(1405)$ which peaks at 1420 MeV, and differs from the nominal one. Combined with several other reactions, like the $\pi^- p \to K^0 \pi \Sigma$ which favours the first pole, this detailed study will reveal a novel structure of the $\Lambda(1405)$ state.