Yong Tang, National Center for Theoretical Sciences
Electroweak Vacuum Stability with Neutrino and Dark Matter
Meeting Room 1 , Kenkyu Honkan 1F
Motivated by the discovery of the Standard Model (SM) Higgs mass around 125 GeV at the LHC, we study the vacuum stability and perturbativity bounds on Higgs scalar of the SM extensions including neutrinos and dark matter (DM). Guided by the SM gauge symmetry and the minimal changes in the SM Higgs potential we consider two extensions of neutrino sector (Type-I and Type-III seesaw mechanisms) and DM sector (a real scalar singlet (darkon) and minimal dark matter (MDM)) respectively. The darkon contributes positively to the $beta$ function of the Higgs quartic coupling $lambda$ and can stabilize the SM vacuum up to high scale. Similar to the top quark in the SM, the cause of instability is sensitive to the size of new Yukawa couplings between heavy neutrinos and Higgs boson, namely, the scale of seesaw mechanism. MDM and Type-III seesaw fermion triplet, two nontrivial representations of $SU(2)_{L}$ group, will bring the additional positive contributions to the gauge coupling $g_{2}$ renormalization group (RG) evolution and would also help to stabilize the electroweak vacuum up to high scale. Reference: arXiv:1202.5717
Nobuhiro Maekawa, Nagoya U
Spontaneous CP violation in E6 GUT and flavor physics
Meeting Room 1, Kenkyu Honkan 1F
It is shown that the origin of Kobayashi-Maskawa phase can be understood by spontaneous CP violation in E6 GUT with family symmetry and moreover, it can solve the SUSY CP problem, especially the strong constraint for the effective SUSY type sfermion mass spectrum from CEDM can be satisfied in a non-trivial way. The naive problem for massless mu neutrino can be solved by considering the higher dimensional operators which are allowed by the symmetry. As the result, realistic neutrino masses iand mixings including large theta13 can be obtained. In the end of this talk, we will comment on the 125 GeV Higgs for this scenario.
Yasutaka Taniguchi, U Tsukuba
Cluster correlations in largely deformed states of nuclei
Seminar Room, Kenkyu Honkan 3F
Nuclear structure changes drastically by low-excitation energies. We discuss deformations and clustering effects, which play important roles in nuclear structures. Nuclei have various structures such as coexistence of various rotational bands, prolate-oblate shape coexistence, multi-cluster states, and so on. In order to understand those structures, both of deformations and clustering should be taken into account.
Laszlo Feher, Institute for Particle and Nuclear Physics, Wigner RCP, HAS
The Ruijsenaars self-duality map as a mapping class symplectomorphism
Seminar Room, Kenkyu Honkan 3F
We explain that the self-duality symplectomorphism of the completely integrable compactified trigonometric Ruijsenaars-Schneider system arises from the natural action of the mapping class group on the moduli space of flat SU(n) connections on the one-holed torus. The talk is based on joint work with C. Klimcik reviewed in arXiv:1203.3300.
Andrew G. Akeroyd, University of Southampton
Phenomenology of the Higgs Triplet Model at the LHC
Meeting Room 1, Kenkyu Honkan 1F
The Higgs Triplet Model is a model of neutrino mass generation which predicts the existence of a doubly charged scalar and a singly charged scalar. Such particles could enhance the branching ratio of a neutral Higgs boson decaying to two photons, a channel which has been observed recently at the LHC. I also discuss the phenomenology of the doubly/singly charged scalars at the LHC, as well as summarise their ongoing searches.
森田辰弥, 東京大
量子系の弱い測定による弱値について
Seminar Room, Kenkyu Honkan 3F
量子系の測定において量子系の始状態と終状態を指定して定まる弱値が注目さ れている。本講演では弱値とその測定である弱測定の手法、及び実験的に有用 とされる弱値の測定値に対する増幅効果について紹介する。また量子力学の基 礎的側面から見た弱値の意味についても議論する。
Koji Tsumura
RG improvements on the CEDM via CP violating four-Fermi operators
Meeting room 1, Kenkyu honkan 1F
The electric dipole moment (EDM) is known to be a good probe of CP violation. In this talk, we focus the CP violating four-Fermi operators, which can mix with the EDM and chromo-EDM (CEDM) operators at one loop level. We show the renormalization-group equations (RGEs) for the (flavor-conserving) CP-violating interaction are derived up to the dimension six. We apply them to the models with the neutral scalar boson or the color-octet scalar boson which have CP-violating Yukawa interactions with quarks. Using the RGEs, the evaluation of the Barr-Zee diagram and the dimension five Weinberg operator is improved.
Kyohei Mukaida, Tokyo U
Boltzmann equation for non-equilibrium particles and its application to non-thermal dark matter production
Meeting room 1, Kenkyu honkan 1F
We consider a scalar field which is very weakly interacting with the thermal bath, and study thermal effects on the evolution of its number density. We use the Boltzmann equation derived from the Kadanoff-Baym equation, assuming that the degrees of freedom in the thermal bath are well described as “quasi-particles” with thermally modified dispersion relations. The obtained Boltzmann equation differs from the conventional one since the collision term is thermally modified through “quasi-particles.” Then, we apply this equation to the Freeze-In dark matter production scenario. We show that thermal effects can change the resultant dark matter abundance by ${cal O} (10-100) %$ compared to the result without taking account of thermal effects.
Corneliu Sochichiu, Sung KyunKwan U
Dirac Lattice or Down to High Energy
Meeting room 1, Kenkyu honkan 1F
I consider the conditions for the emergence of Dirac/Weyl/Majorana fermions from a (nonrelativistic) Fermi system.
Soichiro Goda, Kyoto U
Chiral condensate in nuclear matter beyond linear density using chiral Ward identity
Seminar room, Kenkyu honkan 3F In low-energy Quantum ChromoDynamics, spontaneous breaking of chiral symmetry is one of the most important phenomenon because this is responsible for the generation of the constituent quark mass. We focus on partial restoration of chiral symmetry in a finite density environment such as inside of atomic nucleus. Partial restoration of chiral symmetry can be observed by investigating the modification of hadron properties in nuclear matter. To examine partial restoration of chiral symmetry in nucleus experimentally, binding energy and width of 1s state of deeply bound pionic atom are measured precisely [1]. This experiment suggests that the chiral condensate which is an order parameter of the chiral symmetry breaking is reduced by about 30 % at the nuclear density. In our work [2], we analyze density corrections of the chiral condensate up to Next to leading order (NLO) using the chiral Ward identity [3] and in-medium chiral perturbation theory [4,5]. The in-medium chiral condensate is calculated by a correlation function of the axial current and pseudoscalar density in nuclear matter as a consequence of the chiral Ward identity. The correlation function is evaluated using in-medium chiral perturbation theory with the hadronic quantities of pion and nucleon dynamics. We assume that all of the in-vacuum interaction vertices are known and in-vacuum loop corrections are supposed to be done by using the experimental values of the couplings in the calculation of the condensate. This procedure leads to a density (fermi momentum) expansion. Based on this density expansion approach, we analyze diagrammatic structure of the current Green function which gives density effects to the condensate. This analysis shows that medium effects to the chiral condensate beyond linear density come from interactions between pions and nuclear matter such as pion-exchange process. As a result, we find that NLO contribution is small.
