KEK Theory Meeting on Particle Physics Phenomenology (KEK-PH2025winter)

Session

parallel session B

Feb 18, 2025, 3:20 PM

seminar hall (Building 3)

Conveners

parallel session B: theory

• Yutaka Sakamura

parallel session B: theory

• Yutaka Sakamura

parallel session B: dark matter

• Volodymyr Takhistov

parallel session B: dark matter

• Volodymyr Takhistov

parallel session B: dark matter

• Volodymyr Takhistov

parallel session B: pheno

• Shohei Okawa

parallel session B: pheno

• Shohei Okawa

parallel session B: pheno

• Shohei Okawa

parallel session B: axion

• Ryutaro Matsudo

25. Evanescent contribution of the QCD theta angle

Naohiro Osamura

2/18/25, 3:20 PM

In this talk, we evaluate the QCD theta angle radiatively induced at the two-loop level using the dimensional regularization with the BMHV scheme in a simplified model. When the Lagrangian is promoted into d-dimensional space through the dimensional regularization, evanescent operators are introduced, which break the chiral symmetry. Consequently, a parity-odd fermion loop with the BMHV scheme...

26. Spontaneous CP violation in supersymmetric QCD

Yaoduo Wang

2/18/25, 3:40 PM

We investigate a composite model of spontaneous CP violation based on a new supersymmetric QCD as a solution to the strong CP problem. The scalar components of the meson chiral superfields obtain complex vacuum expectation values to break CP symmetry spontaneously. Then, wavefunction renormalization for the quark kinetic terms provides the Cabibbo-Kobayashi-Maskawa (CKM) phase, while the...

27. Does finetuning make D-term contributions smaller in natural grand unified theories with spontaneous supersymmetry breaking?

Taiju Tanii

2/18/25, 4:00 PM

We explore the natural grand unified theory (GUT) with spontaneous supersymmetry
(SUSY) breaking, focusing on the contribution to sfermion and Higgs masses. Natural GUTs, which introduce all terms allowed by SO(10) × U (1)A symmetry with O(1) coefficients, provide a solution to the problems in SUSY GUTs. Although it is also possible to introduce spontaneous SUSY breaking, it predicts D-term...

29. Wiggly dilaton: a landscape of spontaneously broken scale invariance

Yu-Cheng Qiu

2/18/25, 4:50 PM

The dilaton emerges as a pseudo-Nambu-Goldstone boson (pNGB) associated with the spontaneous breaking of scale invariance in a nearly conformal field theory (CFT). We show the existence of a wiggly dilaton potential that contains multiple vacuum solutions in a five-dimensional (5D) holographic formulation. The wiggly feature originates from boundary potentials of a 5D axion-like scalar field,...

28. Gauge symmetry breaking with two dimensional sphere as extra dimensions

Hiroki Ishikawa

2/18/25, 5:10 PM

In the grand unified theory, the Higgs mechanism is commonly used. However, as an alternative approach, extra dimensions with non-zero curvature can lead to gauge symmetry breaking.

We have constructed a Yang-Mills theory with extra dimensions as two-dimensional sphere(S^2). As a result, the curvature of the extra dimensions and the non-commutative nature of the gauge group lead to a...

30. Mass spectrum of the extra-dimensional components of gauge fields in Yang-Mills theory with extra dimensions of two-dimensional sphere

Yuki Honda

2/18/25, 5:30 PM

The theoretical origin of the Higgs boson remains unclear. Yang-Mills theories in higher dimensions are good candidates to address this issue.
We have constructed a Yang-Mills theory with extra dimensions of two-dimensional sphere. In this model, compared to conventional models such as those with S^1 and T^2, curvature of the extra dimensions and the non-commutative nature of the gauge group...

39. Photon Proliferation Effect from N-body ultralight DM annihilation

Shaoping Li

2/19/25, 1:30 PM

I will demonstrate a general photon proliferation effect from N-body ultralight dark matter (DM) annihilation in the early Universe, which can induce a drastic photon-temperature shift after neutrino decoupling. For pseudoscalar DM mass below the eV scale, I will show that the photon proliferation effect becomes significant as the mass approaches the ultralight end, presenting the leading...

40. Composite Dark Matter with Forbidden Annihilation

Takumu Yamanaka

2/19/25, 1:50 PM

A dark matter model with QCD-like SU(N) gauge symmetry and electroweakly interacting dark quarks is discussed. In this model, the lightest G-parity odd dark pion is a main component of dark matter. I will discuss the relation between the mass spectrum of dark pions and annihilation channels which mainly contribute to the relic abundance. When the masses of dark matter and heavier dark pions...

41. pseudo-Nambu-Goldstone-boson as a Dark Matter Candidate: A Model with Three Complex Scalars under Z3 Symmetry

Riasat Sheikh

2/19/25, 2:10 PM

This study explores a dark matter model where the pseudo-Nambu-Goldstone boson (pNGB) emerges as a viable candidate, resulting from the spontaneous breaking of a U(1) symmetry and stabilized by a Z3 discrete symmetry which naturally emerges as a residual symmetry. The model introduces three complex scalar fields invariant under Standard Model (SM) gauge symmetries, naturally suppressing direct...

42. Excited bound states and their role in dark matter production

Stefan Lederer

2/19/25, 3:00 PM

I explore the impact of highly excited bound states on the evolution of number densities of new physics particles, specifically dark matter, in the early Universe.

Higher excited states play a crucial role in non-Abelian interactions, going as far as preventing a complete decoupling in the early Universe and thus preventing the constituent particle from freezing out. Instead, a continuous...

43. Black String in the Standard Model

Hayate Kimura

2/19/25, 3:20 PM

We found black string solutions in the 4 dimensional standard model, whose existence is suggested by swampland conjecture. The well-known no-go theorem for topologies of horizon except two sphere is avoided by taking into account the Casimir energy, which violate the dominant energy condition, in the energy-momentum tensor.

44. Realising Dark Matter and PTA via Dark Branes

Fotis Koutroulis

2/19/25, 3:40 PM

In this work we propose a setup for the origin of dark matter based on spacetime with a warped extra dimension and three branes: the Planck brane, the TeV brane and a dark brane, at a (sub)-GeV scale. The Standard Model is localized in the TeV brane, thus solving the Higgs hierarchy problem, while the dark matter χ, a Dirac fermion, is localized in the dark brane. The dark matter has only...

45. Minimal dark matter in SU(5) grand unification

Takashi Toma

2/19/25, 4:30 PM

Minimal dark matter is an attractive candidate for dark matter because it is stabilized without the need to impose additional symmetries. It is known that the mass of the SU(2)L quintuplet fermion dark matter is predicted to be around 14 TeV, based on the thermal production mechanism. In this work, we embed the quintuplet dark matter within non-supersymmetric SU(5) grand unified theories. We...

46. Phenomenology of Neutrino-Dark Matter Interaction in DSNB and AGN

Po-Yen Tseng

2/19/25, 4:50 PM

We introduce a neutrino-scalar dark matter (DM) ν-ϕ interaction and consider Diffuse Supernova Neutrino Background (DSNB) and Active Galactic Nuclei (AGN) representing distinctive neutrino sources. We focus on interaction mediated by a heavy fermionic particle F and investigate the attenuation of neutrino fluxes from these sources. We model the unscattered neutrino flux from DSNB via...

47. Composite asymmetric dark matter with a dark photon portal: Multi-Messenger tests

Takumi Kuwahara

2/19/25, 5:10 PM

Composite asymmetric dark matter (ADM) is the framework that naturally explains the coincidence of the baryon density and the dark matter density of the Universe. Through a portal interaction sharing particle-antiparticle asymmetries in the Standard Model and dark sectors, dark matter particles, which are dark-sector counterparts of baryons, can decay into antineutrinos and dark-sector...

57. Lepton Flavor Violating Decay of True Muonium

Ryotaro Minato

2/20/25, 1:30 PM

Lepton Flavor Violation (LFV) serves as a crucial probe into physics beyond the Standard Model. To identify the new particles behind LFV, it is important to search for various types of LFV processes, because the LFV mediators indirectly appear in most of LFV processes.
In this study, we propose a new LFV process, the decay of a muon-antimuon bound state into an electron-antimuon (or...

58. Axion detection with quantum Hall effect

Aiichi Iwazaki

2/20/25, 1:50 PM

A detailed examination of the plateau transition in the quantum Hall effect reveals the presence of axion influence. In quantum Hall effect experiments, strong magnetic fields are used, and microwaves generated by axions from the surrounding metallic walls are emitted. These microwaves are absorbed by localized electrons, causing them to transition to a delocalized state and contribute to the...

59. High frequency gravitons from inflation

Kazunori Nakayama

2/20/25, 2:10 PM

We show that gravitons are efficiently produced through various processes during reheating. The detection of ultra high frequency stochastic gravitational waves can directly determine the inflaton mass, decay rate etc.

60. Impact of the Electroweak Weinberg Operator on the Electric Dipole Moment of Electron

Kiyoto Ogawa

2/20/25, 3:00 PM

The electric dipole moments (EDM) of electron, an observable sensitive to CP violation, is expected to plobe physics beyond the Standard Model (BSM) at TeV scale due to significant improvements in experimental precision. In this study, we evaluated the CP-violating dimension-6 operator for electroweak bosons (the electroweak Weinberg operator) generated at the two-loop level by CP-violating...

61. Constraints on Trilinear Higgs Couplings Including One-loop Correction in Nearly Aligned Higgs Models

Shuhei Ohzawa

2/20/25, 3:20 PM

Although the Higgs boson has been discovered, the couplings between the Higgs boson and Standard Model (SM) particles may deviate from the predictions of the SM. Such deviations can be realized by extending the SM. One possible extension involves the introduction of an extended Higgs model, which extends the Higgs sector. Among extended Higgs models, the nearly aligned Higgs model,...

62. New Constraints on Gauged U(1)Lμ-Lτ Models via Z-Z' Mixing

Coh Miyao

2/20/25, 3:40 PM

Models based on a U(1)$_{L_\mu-L_\tau}$ gauge symmetry can explain the discrepancy between the measured value and theoretical prediction of the muon anomalous magnetic moment. Based on the latest experimental results, we revisit the analysis of neutrino mass matrix structures in minimal U(1)$_{L_\mu-L_\tau}$ models where the U(1)$_{L_\mu-L_\tau}$ symmetry breaking is caused by a single scalar...

63. Effective field theory for type II seesaw model --symmetric phase v.s. broken phase--

Yoshiki Uchida

2/20/25, 4:30 PM

Effective field theory is an effective approach to parameterizing effects of high energy scale physics in low energy measurements. The two popular frameworks for physics beyond the standard model are the so-called Standard Model Effective Field Theory (SMEFT) and the Higgs Effective Field Theory (HEFT). While the description by the SMEFT deteriorates when the new physics scale is not so high...

64. The probability for chiral oscillation of Majorana neutrino in Quantum Field Theory

Tomoharu Tahara

2/20/25, 4:50 PM

We derive the probability for chiral oscillation of Majorana neutrinos based on quantum field theory. Since the Hamiltonian under the Majorana mass term does not conserve lepton number, the eigenstates of lepton number change continuously over time. Therefore, the transition amplitude is described by the inner product of the eigenstates of lepton number at the time of the neutrino production...

71. Two-sided story of sterile neutrinos: production under X-ray limits

Muping Chen

2/20/25, 5:10 PM

Sterile neutrinos are well-motivated and actively searched for hypothetical neutral particles that would mix with the Standard Model active neutrinos. They are considered prime warm dark matter (DM) candidates, typically when their mass is in the keV range, although they can also be hot or cold DM components.
We discuss in detail the characteristics and phenomenology of sterile neutrinos that...

68. QCD axion from chiral gauge theories

Shonosuke Takeshita

2/21/25, 9:50 AM

We present models of axion based on supersymmetric chiral gauge theories. In these models, the PQ symmetry is spontaneously broken by the non-perturbative dynamics of chiral gauge theory. Thanks to supersymmetry, IR dynamics of the models are calculable. We also present an example of a QCD axion model that is compatible with SU(5) grand unification. To avoid the proton decay constraint and a...

69. How viable is a QCD axion near 10 MeV?

Junxuan Xu

2/21/25, 10:10 AM

There has been an attempt to revive the visible QCD axion at the 10 MeV scale
assuming that it exclusively couples to the first-generation quarks and the electron.
This variant of the QCD axion is claimed to remain phenomenologically viable,
partly due to a clever model construction that induces tree-level pion-phobia and exploits uncertainties inherent in the chiral perturbation...

70. High Quality QCD axion via Electric-Magnetic Duality

Shota Nakagawa

2/21/25, 10:30 AM

Axion can solve the strong CP problem dynamically. However, since a global symmetry is expected to be broken explicitly in quantum gravity theory, any extra Peccei-Quinn (PQ) symmetry breaking operator must be suppressed, except for nonperturbative effects of QCD. In this talk, we propose a novel paradigm for the QCD axion with high-quality PQ symmetry on the basis of electric-magnetic duality...