122057407
Regularized determinants for quantum field theories with fermions
A new type of regularized determinant for the ratio of two Dirac operators is presented. Some of its properties with application to the chiral anomaly are given.
123591192
A Comment on Spontaneous Breaking of Chiral Symmetry
121660455
Propagation of a Dirac particle. A path integral approach
Rigorous path integral formulas are given which represent, in two space‐time dimensions, the fundamental solution of the Cauchy problem for the Dirac equation as well as the retarded and advanced propagators for the Dirac particle. It is also shown that the theory can be applied to a free particle and a particle in a central electric field in four space‐time dimensions and reveals some aspects of the path integral. Heuristically discussed is the connection with the phase space path integral or Hamiltonian path integral.
123696966
Measurement of Charged Pion Photoproduction at ELPH
We investigated the charged pion photoproduction on the deuteron in the energy region Eγ = 0.65− 1.1 GeV at Research Center for Electron Photon Science (ELPH), Tohoku University. The photon absorption by a nucleus mainly takes place on a single nucleon at energies above the first resonance region. The rest nucleons are called as the spectator and this process is called as the quasi-free process. The pion is emitted in the subsequent de-excitation process of the nucleon resonance excited through the absorption of the photon. The deuteron is the loosely bound system of the proton and the neutron and the photoreaction on it is considered to be dominated by the quasi-free process. However, significant contribution of the two nucleon absorption process in the π+π− photoproduction on the deuteron was measured in the energy region from 0.6 to 1.1 GeV[1, 2]. The importance of the nucleon resonances and the intermediate and final state interaction was suggested by the theoretical studies[3, 4]. For the detailed study of the intermediate states, precise experimental data, not only the total cross section but also the differential cross sections are required. The ABC effect [5] is a nuclear fusion reaction which is known to be related to the excitation of the two nucleon resonances (ΔΔ) in the intermediate state and their interaction. It is distinguished by a structure in the mass distribution of isoscalar pion pair[6, 7, 8]. One of our aim is the search for the ABC like effect in the photon induced double pion production reaction on the deuteron in the analysis of the similar final state with ABC effect (γd → π+π−d) and the explicit ΔΔ excitation (γd → ΔΔ → π+π−pn). The reactions d(γ, π+π−d) and d(γ, π+π−p)n were measured using the Neutral Kaon Spectrometer 2 (NKS2) at ELPH. The NKS2 is the magnetic spectrometer with the geometrical acceptance roughly 1/4 of the whole solid angle, dedicated for the multi-particle tracking. By refining the calibration of the detectors and the tracking procedures, the increased mass reconstruction resolution enabled us the efficient identification of these reactions with three charged particles in the final state. Simulation studies have been carried out for the extraction of the contributions of the intermediate states. We report on the current status of the analysis for the derivation of the cross sections of these reactions with the extraction of the intermediate states.
100878863
Study of Double Delta Photoproduction on the Deuteron in the Energy Region of Eγ = 0.65–1.1 GeV
We studied the reaction d(γ, π+π−p)n with the Neutral Kaon Spectrometer 2 (NKS2) in a photon energy region of Eγ = 0.65-1.1 GeV at Research Center for Electron Photon Science (ELPH), Tohoku University. In this reaction, existence of the process where two nucleons are excited to Delta particles in the intermediate state was found. It is suggested that the nuclear effects cannot be ignored. By exploring the double Delta photoproduction, we investigated the double pion photoproduction on the deuteron, and the N∗-N interaction which contributes to the intermediate state of this reaction. The cross section of double Delta photoproduction was measured by the TAGX[1] and the NKS[2] in the photon energy region of Eγ = 0.57-0.85 GeV and 0.8-1.1 GeV, respectively. The reported cross sections are not consisted at 0.8 GeV. The theoretical calculation[3] does not reproduce the data above 0.8 GeV. We aim to precise measure the double Delta photoproduction in the photon energy region of Eγ = 0.65-1.1 GeV. Charged particles were detected using the NKS2 which has the large acceptance. The mass of the charged particles was calculated from measurements of the β and their respective momentum, allowing for the identification of π, π− and proton events. The d(γ, π+π−p)n events were extracted with a kinematical cut on the missing momentum. Double Delta excitation in the intermediate state was shown using the invariant mass distributions for πp and π−n. In this presentation, I will report on the invariant mass distributions for πN and the cross section of the double Delta photoproduction.
120162764
Study of Strangeness Photoproduction on the Neutron in the Threshold Region
Photoproduction of the neutral kaon on the deuteron has been investigated at the Research Center for Electron Photon Science, Tohoku University. We constructed the Neutral Kaon Spectrometer-2 for the detection of charged particles from the decay of the neutral kaon and the hyperon. We obtained a momentum distribution of K0 with the inclusive measurement. It was consistent with the previous measurement. The total cross section of γ + d → K0 + Λ + p was estimated from the measured integral cross section of γ + d → Λ + X. The total cross section with respect to the photon energy was compared with the theoretical calculations. It favored the Saclay-Lyon A model calculation with the ratio of the neutral to charged coupling constants of the axial-vector meson, K1, as ~ −1.5. The energy dependence and the magnitude of the total cross section were similar to the total cross section of γ + p → K+ Λ.
124683607
Nuclear Matter in Neutron Stars. A Great Challenge in Nuclear Physics
Lack of our knowledge on the nuclear (hadronic) matter in the neutron star prevents us from understanding its internal structure. The elucidation of the neutron star matter is one of the most important and challenging subjects in nuclear physics today. The nuclear matter EOS (Equation Of State) which would describe pure neutron matter in the outer core of the neutron star is studied via various laboratory experiments particularly by using neutron-rich nuclei. Hyperons and/or kaons are expected to appear in the high density matter in the inner core, which is also experimentally investigated via hypernuclei and kaonic nuclei. Most of the EOS’s including hyperons or kaons lead to a serious discrepancy against the large mass (∼ 2M ) for the recently observed neutron stars, and resolution of this mystery requires new theoretical frameworks in nuclear physics which correctly describe high density matter, some of which may incorporate hadronic degrees of freedom with a deconfined quark matter phase.