0000000000144625
AUTHOR
Makoto Oka
showing 15 related works from this author
The negative-parity spin-1/2 Λ baryon spectrum from lattice QCD and effective theory
2021
The spectrum of the negative-parity spin-1/2 $\Lambda$ baryons is studied using lattice QCD and hadronic effective theory in a unitarized coupled-channel framework. A direct comparison between the two approaches is possible by considering the hadronic effective theory in a finite volume and with hadron masses and mesonic decay constants that correspond to the situation studied on the lattice. Comparing the energy level spectrum and $SU(3)$ flavor decompositions of the individual states, it is found that the lowest two states extracted from lattice QCD can be identified with one of the two $\Lambda(1405)$-poles and the $\Lambda(1670)$ resonance. The quark mass dependences of these two lattic…
Theoretical study of the Ξ(1620) and Ξ(1690) resonances in Ξc→π+MB decays
2017
Nonleptonic weak decays of ${\mathrm{\ensuremath{\Xi}}}_{c}$ into ${\ensuremath{\pi}}^{+}$ and a meson $(M)$-baryon $(B)$ final state, $MB$, are analyzed from the viewpoint of probing $S=\ensuremath{-}2$ baryon resonances, i.e., $\mathrm{\ensuremath{\Xi}}(1620)$ and $\mathrm{\ensuremath{\Xi}}(1690)$, of which spin-parity and other properties are not well known. We argue that the weak decay of ${\mathrm{\ensuremath{\Xi}}}_{c}$ is dominated by a single quark-line diagram, preferred by the Cabibbo-Kobayashi-Maskawa coefficient, color recombination factor, the diquark correlation, and the kinematical condition. The decay process has an advantage of being free from meson resonances in the ${\ens…
Resonances in QCD
2015
We report on the EMMI Rapid Reaction Task Force meeting 'Resonances in QCD', which took place at GSI October 12-14, 2015. A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions: What is needed to understand the physics of resonances in QCD? Where does QCD lead us to expect resonances with exotic quantum numbers? What experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with ${\it up}$, ${\it down}$ and ${\it strange}$ quark content were considered. For heavy-light and heavy-heavy meson systems, those with ${\it charm}$ quarks were the focus. This docum…
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…
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.
A narrow quasi-bound state of the DNN system
2013
Abstract We have investigated a charmed system of DNN (composed of two nucleons and a D meson) by a complementary study with a variational calculation and a Faddeev calculation with fixed-center approximation (Faddeev-FCA). In the present study, we employ a DN potential based on a vector–meson exchange picture in which a resonant Λ c ( 2595 ) is dynamically generated as a DN quasi-bound state, similarly to the Λ ( 1405 ) as a K ¯ N one in the strange sector. As a result of the study of variational calculation with an effective DN potential and three kinds of NN potentials, the D N N ( J π = 0 − , I = 1 / 2 ) is found to be a narrow quasi-bound state below Λ c ( 2595 ) N threshold: total bin…
Measurements of e+e− pairs from open heavy flavor in p+p and d+A collisions at sNN=200 GeV
2017
We report a measurement of e+e− pairs from semileptonic heavy-flavor decays in p+p collisions at sNN=200 GeV. The e+e− pair yield from bb¯ and cc¯ is separated by exploiting a double differential fit done simultaneously in dielectron invariant mass and pT. We used three different event generators, pythia, mc@nlo, and powheg, to simulate the e+e− spectra from cc¯ and bb¯ production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to 4π, significant differences are observed for the total cross section. These difference are less pronounced for bb¯ than for cc¯. The same model dependence was observed in alr…
Two-, Three-, Many-body Systems Involving Mesons. Multimeson Condensates
2015
In this talk we review results from studies with unconventional many hadron systems containing mesons: systems with two mesons and one baryon, three mesons, some novel systems with two baryons and one meson, and finally systems with many vector mesons, up to six, with their spins aligned forming states of increasing spin. We show that in many cases one has experimental counterparts for the states found, while in some other cases they remain as predictions, which we suggest to be searched in BESIII, Belle, LHCb, FAIR and other facilities.
Measurement of the higher-order anisotropic flow coefficients for identified hadrons in Au + Au collisions atsNN=200GeV
2016
Measurements of the anisotropic flow coefficients v2{Ψ2},v3{Ψ3},v4{Ψ4}, and v4{Ψ2} for identified particles (π±,K±, and p+p) at midrapidity, obtained relative to the event planes Ψm at forward rapidities in Au + Au collisions at sNN=200GeV, are presented as a function of collision centrality and particle transverse momenta pT. The vn coefficients show characteristic patterns consistent with hydrodynamical expansion of the matter produced in the collisions. For each harmonic n, a modified valence quark-number Nq scaling [plotting vn{Ψm}/(Nq)n/2 versus transverse kinetic energies (KET)/Nq] is observed to yield a single curve for all the measured particle species for a broad range of KET. A si…
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.
Measurement of jet-medium interactions via direct photon-hadron correlations in Au+Au and d+Au collisions at sNN=200 GeV
2020
We present direct photon-hadron correlations in 200 GeV/A Au+Au, d+Au, and p+p collisions, for direct photon pT from 5–12 GeV/c, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in d+Au collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in Au+Au compared to p+p and d+Au. As the momentum fraction decreases, the yield of hadrons in Au+Au increases to an excess over the yield in p+p collisions. The excess is at large angles and at low hadron pT and is most pronounced for hadrons associated with lower momentum direct …
Charged-pion cross sections and double-helicity asymmetries in polarizedp+pcollisions ats=200 GeV
2015
We present midrapidity charged-pion invariant cross sections, the ratio of the pi(-) to pi(+) cross sections and the charge-separated double-spin asymmetries in polarized p + p collisions at root s = p + 200 GeV. While the cross section measurements are consistent within the errors of next-to-leading-order (NLO) perturbative quantum chromodynamics predictions (pQCD), the same calculations overestimate the ratio of the charged-pion cross sections. This discrepancy arises from the cancellation of the substantial systematic errors associated with the NLO-pQCD predictions in the ratio and highlights the constraints these data will place on flavor-dependent pion fragmentation functions. The char…
Energy and width of a narrowI=1/2DNNquasibound state
2012
The energies and widths of $DNN$ quasi-bound states with isospin I=1/2 are evaluated in two methods, the fixed center approximation to the Faddeev equation and the variational method approach to the effective one-channel Hamiltonian. The $DN$ interactions are constructed so that they dynamically generate the $\Lambda_c(2595)$ (I=0, $J^{\pi} =1/2^-$) resonance state. We find that the system is bound by about 250 MeV from the $DNN$ threshold, $\sqrt{s} \sim 3500$ MeV. Its width including both the mesonic decay and the $D$ absorption, is estimated to be about 20-40 MeV. The I=0 $DN$ pair in the $DNN$ system is found to form a cluster that is similar to the $\Lambda_c(2595)$.
Narrow Bound States of the DNN System
2012
We report on a recent calculation of the properties of the $DNN$ system, a charmed meson with two nucleons. The system is analogous to the $\bar K NN$ system substituting a strange quark by a charm quark. Two different methods are used to evaluate the binding and width, the Fixed Center approximation to the Faddeev equations and a variational calculation. In both methods we find that the system is bound by about 200 MeV and the width is smaller than 40 MeV, a situation opposite to the one of the $\bar K NN$ system and which makes this state well suited for experimental observation.