New perspectives on flavor and symmetries in particle physics

4 Jun 2026, 09:00 → 5 Jun 2026, 20:00 Asia/Seoul

Room 512 (Asia Pacific Center for Theoretical Physics)

Shohei Okawa (APCTP)

This workshop aims to bring together a small group of experts working on all aspects of beyond the standard model physics and discuss recent topics in the field in a casual setting. The main subjects are flavor symmetries, including modular and non-invertible symmetries, and their applications to BSM. Phenomenological implications are also discussed. We plan a relaxed program with ample time for discussions and new collaborations.

This is the 2nd of APCTP New Physics Forums.

(Link to the 1st meeting is here: https://indico.global/event/17411/)

 

 

Speakers:

Mohammad Aghaie (Osaka)

Kento Asai (YITP)

Lorenzo Calibbi (Nankai)

Kwang Sik Jeong (Pusan Natl.)

Gurucharan Mohanta (APCTP)

Hajime Otsuka (Kyushu)

Yoshihiro Shigekami (Henan Normal)

Kei Yamamoto (Iwate)

Seokhoon Yun (Kyungpook Natl.)

 

Organizer:

Shohei Okawa (APCTP)

 

This workshop is supported by the JRG Program at the APCTP through the Science and Technology Promotion Fund and Lottery Fund of the Korean Government and by the Korean Local Governments – Gyeongsangbuk-do Province and Pohang City.

 

Thursday 4 June

1 Registration

2 Welcome

Speaker: Shohei Okawa (APCTP)

Welcome.pdf

Morning Session 1

Convener: Shohei Okawa (APCTP)

3 Gauge and Goldstone bosons from Flavour Symmetries

This seminar discusses models of fermion masses and mixing based on continuous flavour symmetries, emphasizing the phenomenology of the corresponding gauge bosons and — in the global symmetry case — the (pseudo) Nambu-Goldstone bosons arising from spontaneous symmetry breaking. Beginning with a brief overview of the Froggatt-Nielsen U(1) case, I will then focus on a realistic U(2) model. I will show how searches for the light particles associated with these symmetries — especially in flavour-violating decays of leptons and mesons at current and future experiments — can probe exceptionally weak couplings and, consequently, very high energy scales. The talk will also include a brief discussion on the interplay with other probes of high energies, including gravitational wave observatories.

Speaker: Lorenzo Calibbi (Nankai University)

calibbi-APCTP.pdf

4 Flavour Hierarchies and Strong CP

Speaker: Dr GURUCHARAN MOHANTA (Asia Pacific Center for Theoretical Physics)

Apctp_strong_CP_gurucharan.pdf

12:15 Lunch

Afternoon Session 1

Convener: Shohei Okawa (APCTP)

5 Flavor Physics and CP from Non-Invertible Selection Rules

In this talk, I will discuss the application of non-invertible selection rules to flavor physics and CP, in which matter fields are labeled by conjugacy classes of a finite group rather than its irreducible representations. We show that this framework leads to novel texture structures in the Yukawa couplings of quarks and leptons that cannot be realized by conventional group-theoretic (invertible) symmetries. Furthermore, when the fusion rules admit a Z2 symmetry identified with charge conjugation, a CP-invariant system can be consistently defined together with parity transformation. As a result, combining group-based flavor symmetries underlying non-invertible selection rules with CP symmetry naturally gives rise to a generalized CP transformation. We also demonstrate the possibility of spontaneous CP violation in this framework and discuss its implications for Yukawa textures. Finally, I will introduce top-down realizations of non-invertible selection rules arising from string compactifications, such as type IIB superstring theory on toroidal orbifolds and heterotic string theory on non-Abelian orbifolds.

Speaker: Hajime Otsuka (Kyushu University)

otsuka_APCTP_2026.pdf

14:45 Break

Afternoon Session 2

Convener: Shohei Okawa (APCTP)

6 The Minimal Supersymmetric Standard Model with Non-Invertible Selection Rules

We investigate a framework of the Minimal Supersymmetric Standard Model (MSSM) in which the quark and lepton flavor structure and suppression of flavor-changing neutral currents (FCNCs) are governed by non-invertible selection rules. By implementing such non-group-like fusion rules for matter fields, arising from gauging the outer automorphism $Z_2$ of a discrete $Z_N$ symmetry, we obtain realistic Yukawa textures that reproduce the observed quark and lepton masses and mixings while ensuring diagonal soft supersymmetry (SUSY) breaking masses and hence suppressing dangerous FCNC processes. We analyze mass insertion parameters under random O(1) coefficients and find that all flavor-violating effects are consistent with experimental limits on processes such as μ→eγ and meson mixings. We show that the Yukawa textures and soft terms remain stable under renormalization group evolution. Our results demonstrate that non-invertible selection rules provide a compelling new mechanism to address both the flavor structure and FCNC problems in supersymmetric models.

Speaker: Yoshihiro SHIGEKAMI (Tsung-Dao Lee Institute and School of Physics and Astronomy)

Pohang2026-Shigekami.pdf

7 Axion dark matter from heavy quarks

We propose simple scenarios where the observed dark matter abundance arises from decays and scatterings of heavy quarks through freeze-in of an axion-like particle with mass in the 10 keV − 1 MeV range. These models can be tested by future X-ray telescopes, and in some cases will be almost entirely probed by searches for two-body decays K → π + invis. at NA62. As a byproduct, we discuss the cancellation of IR divergencies in flavor-violating scattering processes relevant for thermal axion production, and derive the general contribution to axion-photon couplings from all three light quarks.

Speaker: Mohammad Aghaie

Presentation - Mohammad Aghaie.pdf

8 Free discussion

Dinner

Friday 5 June

Morning Session 1

Convener: Shohei Okawa (APCTP)

9 Electroweak phase transition triggered by hidden QCD

Speaker: Kwang Sik Jeong (Pusan National University)

10 Asymmetric mediator in scotogenic model

Speakers: Dr Kento Asai (YITP), Dr Kento Asai (Yukawa Institute for Theoretical Physics)

APCTPworkshop2026_KentoASAI.pdf

11 photo

10:45 Break

Morning Session 2

Convener: Shohei Okawa (APCTP)

12 Circumstellar Medium of Supernovae as New Probes for Feebly-interacting Particles

In this talk, I will discuss a new strategy to probe feebly interacting particles using the circumstellar medium (CSM) surrounding core-collapse supernovae. New particles produced in the proto-neutron star can escape the stellar interior and deposit visible energy in the dense CSM through decays before shock breakout. This energy injection heats and ionizes the CSM, forms a new particle-induced photosphere, and can generate a distinctive precursor blackbody emission. Taking kinetically mixed dark photons as a benchmark model, I will show how early-time observations of SN 2023ixf constrain such pre-breakout emission and exclude previously unexplored regions of MeV-scale dark photon parameter space. I will also discuss how particle-induced dust sublimation in the outer CSM provides a robust diagnostic for future nearby supernovae, opening a new observational window on dark-sector physics.

Speaker: Dr Seokhoon Yun (IBS-CTPU)

APCTP_S.Yun.pdf

13 Phenomenological implication of flavor symmetry

Speaker: Kei Yamamoto

12:40 Lunch

14 Free discussion

Dinner