Tomohiro Abe

Reproduction is essential for life, but its regulatory mechanism is diverse. The analysis of this diversity should lead us to understand the evolutionary process of the regulation of reproduction. In mammals, the hypothalamic-pituitary-gonadal axis plays an essential role in such regulation, and each component, hypothalamic GnRH, and pituitary gonadotropins, LH, and FSH, is indispensable. However, the common principle of the hypothalamic-pituitary-gonadal axis regulation among vertebrates remains unclear. Here, we used a teleost medaka, which is phylogenetically distant from mammals, and analyzed phenotypes of gene knockouts (KOs) for GnRH, LH, and FSH. We showed that LH release, which we previously showed to be directly triggered by GnRH, is essential for ovulation in females, because KO medaka of GnRH and LH were anovulatory in spite of the full follicular growth and normal gonadosomatic index, and spawning could be induced by a medaka LH receptor agonist. On the other hand, we showed that FSH is necessary for the folliculogenesis, because the follicular growth of FSH KO medaka was halted at the previtellogenic stage, but FSH release does not necessarily require GnRH. By comparing these results with the previous studies in mammals that both GnRH and LH are necessary for folliculogenesis, we propose a hypothesis as follows. During evolution, LH was originally specialized for ovulation, and regulation of folliculogenesis by GnRH-LH (pulsatile release) was newly acquired in mammals, which enabled fine tuning of reproduction through hypothalamus.

We discuss the Type-X (lepton-specific) two Higgs doublet model as a solution of the anomaly of the muon g − 2. We consider various experimental constraints on the parameter space such as direct searches for extra Higgs bosons at the LEP II and the LHC Run-I, electroweak precision observables, the decay of B s → μ+μ−, and the leptonic decay of the tau lepton. We find that the measurement of the tau decay provides the most important constraint, which excludes the parameter region that can explain the muon g − 2 anomaly at the 1σ level. We then discuss the phenomenology of extra Higgs bosons and the standard model-like Higgs boson (h) to probe the scenario favored by the g − 2 data at the collider experiments. We find that the 4τ , 3τ and 4τ + W/Z signatures are expected as the main signal of the extra Higgs bosons at the LHC. In addition, we clarify that the value of the hττ coupling is predicted to be the standard model value times about −1.6 to −1.0, and the branching fraction of the h → γγ mode deviates from the standard model prediction by −30% to −15%. Furthermore, we find that the exotic decay mode, h decaying into the Z boson and a light CP-odd scalar boson, is allowed, and its branching fraction can be a few percent. These deviations in the property of h will be tested by the precision measurements at future collider experiments.

A bstract If dark matter (DM) is a fermion and its interactions with the standard model particles are mediated by pseudoscalar particles, the tree-level amplitude for the DM-nucleon elastic scattering is suppressed by the momentum transfer in the non-relativistic limit. At the loop level, on the other hand, the spin-independent contribution to the cross section appears without such suppression. Thus, the loop corrections are essential to discuss the sensitivities of the direct detection experiments for the model prediction. The one-loop corrections were investigated in the previous works. However, the two-loop diagrams give the leading order contribution to the DM-gluon effective operator $$ \left(\overline{\chi}\chi {G}_{\mu \nu}^{\alpha }{G}^{\alpha \mu \nu}\right) $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mfenced> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>χ</mml:mi> <mml:msubsup> <mml:mi>G</mml:mi> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mi>α</mml:mi> </mml:msubsup> <mml:msup> <mml:mi>G</mml:mi> <mml:mrow> <mml:mi>α</mml:mi> <mml:mi>μ</mml:mi> <mml:mi>ν</mml:mi> </mml:mrow> </mml:msup> </mml:mrow> </mml:mfenced> </mml:math> and have not been correctly evaluated yet. Moreover, some interaction terms which affect the scattering cross section were overlooked. In this paper, we show the cross section obtained by the improved analysis and discuss the region where the cross section becomes large.

Dark matter (DM) simplified models are by now commonly used by the ATLAS and CMS Collaborations to interpret searches for missing transverse energy (ETmiss). The coherent use of these models sharpened the LHC DM search program, especially in the presentation of its results and their comparison to DM direct-detection (DD) and indirect-detection (ID) experiments. However, the community has been aware of the limitations of the DM simplified models, in particular the lack of theoretical consistency of some of them and their restricted phenomenology leading to the relevance of only a small subset of ETmiss signatures. This document from the LHC Dark Matter Working Group identifies an example of a next-generation DM model, called 2HDM+a, that provides the simplest theoretically consistent extension of the DM pseudoscalar simplified model. A comprehensive study of the phenomenology of the 2HDM+a model is presented, including a discussion of the rich and intricate pattern of mono-X signatures and the relevance of other DM as well as non-DM experiments. Based on our discussions, a set of recommended scans are proposed to explore the parameter space of the 2HDM+a model through LHC searches. The exclusion limits obtained from the proposed scans can be consistently compared to the constraints on the 2HDM+a model that derive from DD, ID and the DM relic density.

We propose new backgrounds of extra dimensions to lead to four-dimensional chiral models with three generations of matter fermions, that is T 2 /Z N twisted orbifolds with magnetic fluxes. We consider gauge theory on six-dimensional space-time, which contains the T 2 /Z N orbifold with magnetic flux, Scherk-Schwarz phases and Wilson line phases. We classify all the possible Scherk-Schwarz and Wilson line phases on T 2 /Z N orbifolds with magnetic fluxes. The behavior of zero modes is studied. We derive the number of zero modes for each eigenvalue of the Z N twist, showing explicitly examples of wave functions. We also investigate Kaluza-Klein mode functions and mass spectra.