119213142
Pairing fluctuations and gauge symmetry restoration in rotating superfluid nuclei
Rapidly rotating nuclei provide us good testing grounds to study the pairing correlations; in fact, the transition from the superfluid to the normal phase is realized at high-spin states. The role played by the pairing correlations is quite different in these two phases: The static (BCS like mean-field) contribution is dominant in the superfluid phase, while the dynamic fluctuations beyond the mean-field approximation are important in the normal phase. The influence of the pairing fluctuations on the high-spin rotational spectra and moments of inertia is discussed.
119187180
Microscopic study of tetrahedrally symmetric nuclei by an angular-momentum and parity projection method
We study the properties of the nuclear rotational excitations with hypothetical tetrahedral symmetry by employing the microscopic mean-field and residual-interaction Hamiltonians with angular-momentum and parity projection method; we focus on the deformed nuclei with tetrahedral doubly-closed shell configurations. We find that for pure tetrahedral deformation the obtained excitation patterns satisfy the characteristic features predicted by group-representation theory applied to the tetrahedral symmetry group. We find that a gradual transition from the approximately linear to the characteristic rigid-rotor, parabolic energy-vs.-spin dependence occurs as a function of the tetrahedral deformation parameter. The form of this transition is compared with the similar well-known transition in the case of quadrupole deformation.
199673909
Nuclear moments of inertia and wobbling motions in triaxial superdeformed nuclei
The wobbling motion excited on triaxial superdeformed nuclei is studied in terms of the cranked shell model plus random phase approximation. Firstly, by calculating at a low rotational frequency the \gamma-dependence of the three moments of inertia associated with the wobbling motion, the mechanism of the appearance of the wobbling motion in positive-\gamma nuclei is clarified theoretically -- the rotational alignment of the \pi i_{13/2} quasiparticle(s) is the essential condition. This indicates that the wobbling motion is a collective motion that is sensitive to the single-particle alignment. Secondly, we prove that the observed unexpected rotational-frequency dependence of the wobbling frequency is an outcome of the rotational-frequency dependent dynamical moments of inertia.
119426197
Nuclear wobbling motion and electromagnetic transitions
Abstract The nuclear wobbling motion is studied from a microscopic viewpoint. It is shown that the expressions not only of the excitation energy but also of the electromagnetic-transition rate in the microscopic RPA framework can be cast into the corresponding forms of the macroscopic rotor model. Criteria to identify the rotational band associated with the wobbling motion are given. Examples of realistic calculations are investigated and some theoretical predictions are presented.
121954152
The role of spin-orbit potential in nuclear prolate-shape dominance
Abstract It is confirmed, in terms of the Woods–Saxon–Strutinsky method, that the spin–orbit potential plays a decisive role in the predominance of prolate deformation, which has been a long standing problem in nuclear physics. It is originated from the combined effects of the spin–orbit coupling and the diffused surface of the potential, in agreement with the previous work based on a more schematic Nilsson–Strutinsky method. The degree of prolate-shape dominance exhibits an oscillatory behavior with respect to the strength of spin–orbit potential and, the prolate-shape dominance is realized at the proper strength of the spin–orbit potential together with the standard surface diffuseness; this oscillatory behavior disappears in case of small diffuseness corresponding to ellipsoidal cavity. The calculated energy differences between oblate and prolate minima in this Letter are consistent with those of our extensive self-consistent calculations of the Hartree–Fock + BCS method with the Skyrme interaction.
119098407
Microscopic Calculation of the Wobbling Excitations Employing the Woods-Saxon Potential as a Nuclear Mean-Field
The wobbling excitations of the triaxial superdeformed (TSD) bands in the Lu and Hf region are studied by the microscopic framework of the cranked mean-field and the randomphase approximation (RPA). In contrast to the previous works, where the Nilsson potential was used, the more realistic Woods-Saxon potential is employed as a nuclear mean-field. It is pointed out that the original formulation should be slightly modified for general meanfield like the Woods-Saxon potential. The wobbling-like RPA solutions have been found systematically in the nuclei studied and their characteristic properties are investigated in detail. This confirms the wobbling phonon excitations in TSD nuclei from the microscopic calculations. The result of B(E2) values indicates that the triaxial deformation is increasing as a function of spin in the observed TSD bands in 163 Lu. Subject Index: 210, 211, 212
123615884
Automation of loop amplitudes in numerical approach
Abstract An automatic calculating system GRACE-L1 of one-loop Feynman amplitude is reviewed. This system can be applied to 2 to 2-body one-loop processes. A sample calculation of 2 to 3-body one-loop amplitudes is also presented.
8136589
Deviation from tri-bimaximal mixing and flavor symmetry breaking in a seesaw type A(4) model
Abstract We have studied the contribution of higher order corrections of the flavor symmetry breaking in the A 4 seesaw model with the supersymmetry. Taking account of possible higher dimensional mass operators, we predict the deviation from the tri-bimaximal lepton mixing for both normal hierarchy and inverted hierarchy of neutrino masses. We have found that the value of sin 2 2 θ 23 is larger than 0.96 and the upper bound of sin 2 θ 13 is 0.01. We have also examined the flavor changing neutral current of leptons from the soft SUSY breaking in slepton masses and A-terms within the framework of supergravity theory. Those magnitudes are enough suppressed to be consistent with experimental constraints.
55566134
Current status of the LHCf experiment and future plan
The Large Hadron Collider forward (= LHCf) experiment has successfully finished the first phase of data taking at LHC √ s = 0.9 and 7 TeV proton-proton collisions in 2010. As current status, we concentrate on analyzing the obtained data. As the first result, the energy spectra of photon measured by LHCf during = 7 TeV p-p collision has been published recently. Also the study of the upgraded version of LHCf detector for future = 14TeV run scenario is developed with the GSO scintillator. Another possible plan of p-A(nuclear) collision in LHC is also studied. In this paper, as the current status of the experiment, analyses, and works for foreseen detector upgrade are summarized.
118837490
Minimal neutrino texture with neutrino mass ratio and Cabibbo angle
We present neutrino mass matrix textures in a minimal framework of the type-I seesaw mechanism, where two right-handed Majorana neutrinos are introduced in order to reproduce experimental results of neutrino oscillations. The textures can lead to experimentally favored leptonic mixing angles described by tri-bimaximal mixing with one additional rotation. We present minimal and next to minimal textures for the normal mass hierarchy case in the context of the texture zero. A minimal texture in the inverted hierarchy case is also constructed, which does not have any vanishing entries in a Dirac neutrino mass matrix. We also discuss some cases in which the model parameters in the textures are supposed to be a neutrino mass ratio and/or the Cabibbo angle. Predicted regions of mixing angles, a leptonic CP-violation parameter, and an effective mass for the neutrinoless double beta decay are presented in all textures.
1235737
Radioactive ion beam transportation for the fundamental symmetry study with laser-trapped atoms.
The search for the violation of the fundamental symmetry in a radioactive atom is the promising candidate for precision tests of the standard model and its possible extensions. The subtle signal arising from the symmetry violation is enhanced in heavy atoms, such as a francium (Fr). To realize high precision measurements, a large amount of radioactive isotopes is required. The Fr is produced via a nuclear fusion reaction using a melted gold target with a (18)O primary beam at Cyclotron and Radioisotope Center, Tohoku University. The maximum extraction efficiency of the Fr ion was achieved at approximately 35%. The beam line consists of an electrostatic deflector, three electrostatic quadrupole triplets to the measurement area at 10 m away from the reaction point, and several beam diagnosis systems. We optimized parameters of the beam line.