arXiv subjects

Atsushi Hosaka

Publications and source records attributed to Atsushi Hosaka.

At least 91 records · Page 5Linked to original sources

arXiv2016

D-wave charmed and bottomed baryons from QCD sum rules

We study the $D$-wave charmed baryons of $SU(3)$ flavor $\mathbf{\bar3}_F$ using the method of QCD sum rule in the framework of heavy quark effective theory (HQET). We find that the $Λ_c(2880)$, $Ξ_c(3055)$ and $Ξ_c(3080)$ can be well described by the $D$-wave $SU(3)$ $\mathbf{\bar 3}_F$ charmed baryon multiplets of $J^P=3/2^+$ and $5/2^+$, which contain two $λ$-mode orbital excitations, i.e., the $Λ_c(2880)$ has $J^P=5/2^+$, and the $Ξ_c(3055)$ and $Ξ_c(3080)$ have $J^P = 3/2^+$ and $5/2^+$, respectively. Our results also suggest that the $Λ_c(2880)$ has a partner state, the $Λ_c(3/2^+)$ of $J^P=3/2^+$. Its mass is around $2.81 ^{+0.33}_{-0.18}$ GeV, and the mass difference between it and the $Λ_c(2880)$ is $28^{+45}_{-24}$ MeV. We also evaluate the masses of their bottom partners.

hep-ph↗

arXiv2016

Non-linear quantum dynamics in strong and short electromagnetic fields

In our contribution we give a brief overview of two widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.m.) (e.g.\ laser) wave field or generalized Breit-Wheeler process and a single a photon emission off an electron interacting with the laser pules, so-called non-linear Compton scattering. We show that at small and moderate laser field intensities the shape and duration of the pulse are very important for the probability of considered processes. However, at high intensities the multi-photon interactions of the fermions with laser field are decisive and completely determined all aspects of subthreshold electron-positron pairs and photon production

hep-ph↗

arXiv2016

Heavy pentaquark states $P_c(4380)$ and $P_c(4450)$ in the $J/ψ$ production induced by pion beams off the nucleon

In this study, we investigate the $J/ψ$ production induced by pion beams off the nucleon, particularly the heavy pentaquarks $P_c(4380)$ and $P_c(4450)$ in intermediate states, based on a hybridized Regge model. The process involving $ρ$ and $π$ meson exchange in the $t$ channel is considered as background, and the heavy pentaquark exchange is included in the $s$ channel. The coupling constants such as the $ρNN$ and $πNN$ vertices are taken from the $NN$ potentials, whereas those for the $J/ψρπ$ and $J/ψππ$ vertices are determined by using experimental data based on the branching ratios. In order to estimate the $P_c(4380)$ and $P_c(4450)$ coupling constants, we use the experimental upper limit on the total cross section as a guide for the $πN\to J/ψN$ reaction. The background total cross section is the order of $10^{-4}-10^{-3}$ nb. In the vicinity of the heavy pentaquark masses, the total cross section reaches about $1$ nb.

hep-ph↗

arXiv2016

Structure of charmed baryons studied by pionic decays

We investigate the decays of the charmed baryons aiming at the systematic understanding of hadron internal structures based on the quark model by paying attention to heavy quark symmetry. We evaluate the decay widths from the one pion emission for the known excited states, Λ_c^*(2595), Λ_c^*(2625), Λ_c^*(2765), Λ_c^*(2880) and Λ_c^*(2940), as well as for the ground states Σ_c(2455) and Σ_c^*(2520). The decay properties of the lower excited charmed baryons are well explained, and several important predictions for higher excited baryons are given. We find that the axial-vector type coupling of the pion to the light quarks is essential, which is expected from chiral symmetry, to reproduce the decay widths especially of the low lying Λ_c^* baryons. We emphasize the importance of the branching ratios of Γ(Σ_c^*π)/Γ(Σ_cπ) for the study of the nature of higher excited Λ_c^* baryons.

hep-ph↗

arXiv2016

$K^0 Λ$ and $D^- Λ_c^+$ production induced by pion beams off the nucleon

We present a comparative study of the pion induced production of $K^0 Λ$ and $D^- Λ_c^+$ off the nucleon. A hybrid framework is utilized by combining an effective Lagrangian method with a Regge approach. We consider the $t$-channel process in a plannar diagram by vector-meson Reggeon exchanges and the $u$-channel one in a non-planar diagram by baryon Reggeon exchanges. The present model reproduces the $K^0 Λ$ production data well with a few parameters. Having fixed them, we predict the $D^- Λ_c^+$ production, which turns out to be about $10^4-10^6$ times smaller than the strangeness one, depending on the kinematical regions.

hep-ph↗

arXiv2016

Kaon-Nucleon systems and their interactions in the Skyrme model

We study kaon-nucleon systems in the Skyrme model in a method based on the bound state approach of Callan-Klebanov but with the kaon around the physical nucleon of the rotating hedgehog. This corresponds to the variation after projection, reversing the order of semiclassical quantization of $1/N_c$ expansion. The method, however, is considered to be suited to the study of weakly interacting kaon-nucleon systems including loosely $\bar{K}N$ bound states such as $Λ(1405)$. We have found a bound state with binding energy of order ten MeV, consistent with the observed state. We also discuss the $\bar{K}N$ interaction and find that it consists of an attraction in the middle range and a repulsion in the short range.

nucl-th↗

arXiv2016

Exotic Hadrons with Heavy Flavors -X, Y, Z and Related States-

In the past decade, exotic hadrons with charm and bottom flavors have been extensively studied both in experiments and in theories. In this review, we provide topical discussions by selecting $X,Y,Z$ particles, to which Belle has made important contributions. These are $X(3872)$, $Y(4260)$, $Z_c(4430)^+$, $Z_c(3900)^+$, $Z_{b}(10610)^+$ and $Z_{b}(10650)^+$. Based on the current experimental observations, we discuss those states with emphasis on hadronic molecule whose dynamics is governed by chiral symmetry and heavy-quark symmetry of QCD. We also mention briefly various interpretations and some theoretical predictions for the yet undiscovered exotic hadrons.

hep-ph↗

arXiv2016

Charmed baryons and their interactions

In this proceedings report, we discuss unique features of charmed, or in general heavy, baryons with one heavy quark. A well and long-term known phenomena, the distinction of the two modes of the rho and lambda type of a three-quark system is revisited. The difference of these modes may be tested in the production and decay reactions of the baryons which may be tested in the future experiments at J-PARC.

hep-ph↗

arXiv2015

Quantum processes in short and intensive electromagnetic fields

This work provides an overview of our recent results in studying two most important and widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\ laser) wave field or generalized Breit-Wheeler process, and a single a photon emission off an electron interacting with the laser pules, so-called non-linear Compton scattering. We show that the probabilities of particle production in both processes are determined by interplay of two dynamical effects, where the first one is related to the shape and duration of the pulse and the second one is non-linear dynamics of the interaction of charged fermions with a strong electromagnetic field. We elaborate suitable expressions for the production probabilities and cross sections, convenient for studying evolution of the plasma in presence of strong electromagnetic fields

hep-ph↗

arXiv2015

Determination of the carrier envelope phase for short, circularly polarized laser pulses

We analyze the impact of the carrier envelope phase on the differential cross sections of the Breit-Wheeler and the generalized Compton scattering in the interaction of a charged electron (positron) with an intensive ultra-short electromagnetic (laser) pulse. The differential cross sections as a function of the azimuthal angle of the outgoing electron have a clear bump structure, where the bump position coincides with the value of the carrier phase. This effect can be used for the carrier envelope phase determination.

hep-ph↗

arXiv2015

Production of strange and charmed baryons in pion induced reactions

We study the strangeness and charm productions induced by the pion beam, i.e. the $π^-$p $\rightarrow$ $K^{*0}Λ$ and $π^-$p $\rightarrow$ $D^{*-}Λ_c^+$ reactions, based on two different theoretical frameworks: an effective Lagrangian method and a Regge approach. In order to estimate the magnitude of the charm production relative to that of the strangeness production, we assume that the coupling constants for the charmed meson and baryon vertices are the same as those for the strangeness channel. We found that the total cross section for the charm production was about $10^3 - 10^6$ times smaller than that for the strangeness production, depending on theoretical approaches and kinematical regions. We also discuss each contribution to observables for both reactions. In general, the Regge approach explains the experimental data very well over the whole energy region.

hep-ph↗

arXiv2015

Pion Induced Reactions for the Study of Charmed Baryons

In this talk, we report the study of $π^- p \to K^{*0} Λ$ and $π^- p \to D^{*-} Λ_c^+$ reactions by using an effective Lagrangian method and a hybrid Regge model. The total and differential cross sections for the $K^{*0} Λ$ production are first calculated and then those for the $D^{*-} Λ_c^+$ one are estimated. The two models yield different results, each exhibiting specific features. Our prediction for the charm production provides valuable information about the upcoming J-PARC experiment.

hep-ph↗

arXiv2015

QCD sum rule calculation for P-wave bottom baryons

We study the P-wave bottom baryons using the method of QCD sum rule and heavy quark effective theory. Our results suggest that Lambda_b(5912) and Lambda_b(5920) can be well described by the baryon doublet [3F_bar, 1, 1, rho], and they belong to the SU(3) 3F_bar multiplets of J(P)=1/2(-) and 3/2(-). Their SU(3) flavor partners, Xi_b(1/2-) and Xi_b(3/2-), have masses 6.06 \pm 0.13 GeV and 6.07 \pm 0.13 GeV, respectively, with mass splitting 9 \pm 4 MeV. The results obtained using baryon doublet [3F_bar, 1, 0, lambda] are similar and also consistent with the experimental data. We also study the SU(3) 6F multiplets by using the baryon multiplets [6F, 0, 1, lambda], [6_F, 1, 0, rho] and [6F, 2, 1, lambda], and our results suggest that the P-wave bottom baryons Sigma_b, Xi'_b and Omega_b have (averaged) masses about 6.0 GeV, 6.2 GeV and 6.4 GeV, respectively.

hep-ph↗

arXiv2015

Spectrum of heavy baryons in the quark model

Single- and double- heavy baryons are studied in the constituent quark model. The model Hamiltonian is chosen as a standard one with two exceptions : (1) The color-Coulomb term depend on quark masses, and (2) an antisymmetric $LS$ force is introduced. Model parameters are fixed by the strange baryon spectra, $Λ$ and $Σ$ baryons. The masses of the observed charmed and bottomed baryons are, then, fairly well reproduced. Our focus is on the low-lying negative-parity states, in which the heavy baryons show specific excitation modes reflecting the mass differences of heavy and light quarks. By changing quark masses from the SU(3) limit to the strange quark mass, further to the charm and bottom quark masses, we demonstrate that the spectra change from the SU(3) symmetry patterns to the heavy quark symmetry ones.

hep-ph↗

arXiv2015

P-wave charmed baryons from QCD sum rules

We study the P-wave charmed baryons using the method of QCD sum rule in the framework of heavy quark effective theory (HQET). We consider systematically all possible baryon currents with a derivative for internal rho- and lambda-mode excitations. We have found a good working window for the currents corresponding to the rho-mode excitations for Lambda_c(2595), Lambda_c(2625), Xi_c(2790) and Xi_c(2815) which complete two SU(3) 3F_bar multiplets of J(P)=1/2(-) and 3/2(-), while the currents corresponding to the lambda-mode excitations seem also consistent with the data. Our results also suggest that there are two Sigma_c(2800) states of J(P)=1/2(-) and 3/2(-) whose mass splitting is 14 \pm 7 MeV, and two Xi_c(2980) states whose mass splitting is 12 \pm 7 MeV. They have two Omega_c partners of J(P) = 1/2(-) and 3/2(-), whose masses are around 3.25 \pm 0.20 GeV with mass splitting 10 \pm 6 MeV. All of them together complete two SU(3) 6F multiplets of J(P)=1/2(-) and 3/2(-). They may also have J(P)=5/2(-) partners. Xi_c(3080) may be one of them, and the other two are Sigma_c(5/2(-)) and Omega_c(5/2(-)), whose masses are 85 \pm 23 and 50 \pm 27 MeV larger.

hep-ph↗

arXiv2014

Elementarity of composite systems

The "compositeness" or "elementarity" is investigated for s-wave composite states dynamically generated by energy-dependent and independent interactions. The bare mass of the corresponding fictitious elementary particle in an equivalent Yukawa model is shown to be infinite, indicating that the wave function renormalization constant Z is equal to zero. The idea can be equally applied to both resonant and bound states. In a special case of zero-energy bound states, the condition Z = 0 does not necessarily mean that the elementary particle has the infinite bare mass. We also emphasize arbitrariness in the "elementarity" leading to multiple interpretations of a physical state, which can be either a pure composite state with Z = 0 or an elementary particle with Z \ne 0. The arbitrariness is unavoidable because the renormalization constant Z is not a physical observable.

hep-ph↗

arXiv2014

Laser pulse-shape dependence of Compton scattering

Compton scattering of short and ultra short (sub-cycle) laser pulses off mildly relativistic electrons is considered within a QED framework. The temporal shape of the pulse is essential for the differential cross section as a function of the energy of the scattered photon at fixed observation angle. The partly integrated cross section is sensitive to the non-linear dynamics resulting in a large enhancement of the cross section for short and, in particular, for ultra-short flat-top pulse envelopes which can reach several orders of magnitude, as compared with the case of a long pulse. Such effects can be studied experimentally and must be taken into account in Monte-Carlo/transport simulations of %$e^+e^-$ pair production in the interaction of electrons and photons in a strong laser field.

hep-ph↗

arXiv2014

Effects of $N(2000)\, 5/2^+$, $N(2060)\,5/2^-$, $N(2120)\,3/2^-$, and $N(2190)\,7/2^-$ on $K^*Λ$ photoproduction

We reinvestigate $K^*Λ(1116)$ photoproduction off the nucleon target, based on an effective Lagrangian approach. We include higher nucleon resonances such as $N(2000)\, 5/2^+$, $N(2060)\,5/2^-$, $N(2120)\,3/2^-$, and $N(2190)\,7/2^-$, of which the data are taken from the 2012 edition of Review of Paritcle Physics, in addition to the $t$-channel diagrams ($K$, $K^*$, and $κ$), the $s$-channel nucleon, and $u$-channel hyperon($Λ$, $Σ$, and $Σ^*$) contributions. We find that the $N(2120)\,3/2^-$ and $N(2190)\,7/2^-$ resonances are essential in describing the new CLAS data for charged $K^*$ photoproduction. On the other hand, they rarely affect for neutral $K^*$ photoproduction.

hep-ph↗