FLASY 2025 - 11th Workshop on Flavour Symmetries and Consequences in Accelerators and Cosmology

30 Jun 2025, 00:30 → 4 Jul 2025, 18:00 Europe/Rome

Aula Magna Architettura "Adalberto Libera" (Roma Tre)

FLASY 2025 is the 11th Workshop on Flavour Symmetries and Consequences in Accelerators and Cosmology.

[ Update: Registration closes soon! (deadline extended to 15 Jun). ]
[ Update: Fee payment is available (see Conference Fee tab). ]
[ Update: Please beware of SCAM emails. Registration and fee payment are only possible via the indico webpage and links provided therein. There is no Hotel Booking service. ]

This workshop will bring together researchers in the fields of flavour symmetries, neutrino physics, Higgs physics, CP violation, accelerator physics, and cosmology to present new results and foster discussions that can lead to new and fruitful collaborations. 

FLASY 2025 will take place from June 30 to July 4 in Rome, Italy.

Confirmed plenary speakers include:   

• S. Antusch (University of Basel)
• F. Brizioli (U. Perugia and INFN Perugia) [for the NA62 Collab.]
• G. Burdman (U. São Paulo)
• P. W. Cattaneo (INFN Pavia) [for the MEGII Collab.]
• M.-C. Chen (UC, Irvine)
• S. C. Chuliá (Max Planck Inst., Heidelberg)
• C. Cornella (CERN)
• G.-J. Ding (USTC, Hefei)
• F. Feruglio (INFN Padova)
• M. Ghosh (Boskovic Inst., Zagreb)
• C. Hagedorn (València U., IFIC)
• P. Harrison (Warwick U.)
• J. Harz (Mainz U.)
• S. Jäger (University of Sussex)
• S. K. Kang (Seoul Natl. U.)
• T. Kephart (U. Vanderbilt)
• S. King (U. Southampton)
• E. Lisi (INFN Bari)
• E. Ma (University of California Riverside)
• A. Marrone (INFN Bari and U. Bari)
• G. Martinelli (U. Roma and INFN Roma)
• M. Mondragon (UNAM, Mexico)
• M. Nardecchia (U. Roma)
• E. Nardi (INFN, LNF and NICPB, Tallinn)
• H. Päs (T. U. Dortmund)
• S. Pascoli (INFN Bologna and U. Bologna)
• E. Peinado (Mexico U.)
• S. T. Petcov (Tokyo U., IPMU and SISSA Trieste)
• M. Ratz (UC, Irvine)
• G. Ricciardi (Naples U.)
• M. Tanimoto (Niigata U.)
• A. Titov (U. Pisa and INFN Pisa)
• A. Trautner (CFTP, IST Lisbon)
• J. Turner (Durham U., IPPP)
• I.dM. Varzielas (CFTP, IST Lisbon)
• Z.-z. Xing (IHEP, CAS and Peking U., CHEP)

Local Organising Committee:   

• D. Meloni (Chair, Roma Tre U.)
• F. Mescia (INFN, LNF)
• S. Morisi (Naples U.)
• M. Parriciatu (Roma Tre U.)
• J. Penedo (Co-chair, INFN Roma Tre)

 

FLASY 2025 is supported by:

Poster_FLASY2025_final.pdf

Monday, 30 June

08:00 Registration

Morning session

1 Opening

2 Unitarity triangle angles explained: a predictive new quark mass matrix texture

We propose a novel quark mass matrix texture-pair with five free parameters, which fits the four quark mass ratios $m_s/m_b$, $m_d/m_b$, $m_c/m_t$, $m_u/m_t$, and the four
CKM quark mixing observables. The matrices each have one texture zero, but the main innovation here is a ``geometric'' ansatz exploiting a pair of small complex expansion parameters, based on the geometry of the Unitarity Triangle. The fit to the observables is in good agreement with current experimental values renormalised to $\sim\!\!10^4$ TeV, and offers decisive tests against future high-precision measurements of the unitarity triangle angles at the weak scale. We identify two novel symmetries of these mass matrices which explain the phenomenologically-successful relations $\alpha\equiv\phi_2\simeq \pi/2$ and $\beta\equiv\phi_1\simeq\pi/8$.

Speaker: Paul Harrison (University of warwick)

3 The mu-tau reflection symmetry of Majorana neutrinos in a cross seesaw system

In the canonical seesaw framework flavor mixing and CP violation in weak charged current interactions of light and heavy Majorana neutrinos are correlated with each other and described respectively by the $3\times 3$ matrices $U$ and $R$. We show that the very possibility of $\big|U^{}_{\mu i}\big| = \big|U^{}_{\tau i}\big|$ (for $i = 1, 2, 3$), which is strongly indicated by current neutrino oscillation data as a good approximation, automatically leads to a novel relation $\big|R^{}_{\mu i}\big| = \big|R^{}_{\tau i}\big|$ (for $i = 1, 2, 3$). We show that behind these two sets of equalities and the experimental evidence for leptonic CP violation lies a minimal flavor symmetry: the overall neutrino mass term keeps invariant when the left-handed neutrino fields transform as $\nu^{}_{e \rm L} \to (\nu^{}_{e \rm L})^c$, $\nu^{}_{\mu \rm L} \to (\nu^{}_{\tau \rm L})^c$, $\nu^{}_{\tau \rm L} \to (\nu^{}_{\mu \rm L})^c$ and the right-handed neutrino fields undergo an arbitrary unitary CP transformation. Such a generalized $\mu$-$\tau$ reflection symmetry, together with the fact that all the active-sterile flavor mixing angles in $R$ are expected to be considerably smaller than the active flavor mixing angles in $U$, provides an intriguing illustration of the emergence of a cross seesaw system for both neutrino masses and flavor mixing effects of Majorana neutrinos.

Speaker: Zhi-zhong Xing (Institute of High Energy Physics, Chinese Academy of Sciences)

11:00 Coffee break

Morning session

4 Global neutrino analysis 2025: Knowns and Unknowns

Speaker: Eligio Lisi (Istituto Nazionale di Fisica Nucleare)

5 Past, Present and Future in Flavor Physics, the Unitary Triangle Fit, Anomalies and all that

Speaker: Guido Martinelli (Istituto Nazionale di Fisica Nucleare)

12:30 Free time for lunch

Afternoon session

6 Modular invariance and the strong CP problem

I discuss a set of conditions under which the strong CP problem is solved by spontaneous CP violation. Such conditions find their natural realization in anomaly-free modular invariant supersymmetric theories, suggesting a common solution to the strong CP problem and the flavor puzzle. In its minimal realization, this solution requires a single chiral multiplet, beyond those of the MSSM. If one of its spin-zero components is light, it provides a viable Dark Matter candidate.

Speaker: Ferruccio Feruglio (Istituto Nazionale di Fisica Nucleare)

7 TBA

Speaker: Eduardo Peinado

8 TBA

Speaker: Julia Harz (Technical University of Munich (TUM))

16:00 Coffee break

Afternoon session

9 Updated result from µ+→e+ γ search in MEGII and future projects

We report the result of the search for the decay µ+ → e+ γ undertaken at the Paul Scherrer
Institut in Switzerland with the MEG II experiment using the data collected in the 2021–2022
physics runs. The MEG II detector consists of a spectrometer built around a solenoidal
magnet delivering a gradient field, consisting of a large cylindrical drift chamber and a
highly segmented timing counter for positron detection, and a large liquid xenon detector
for gamma-ray detection.
The sensitivity of this search improves significantly that obtained with the full MEG dataset,
obtained in a data taking period of about one fourth that of MEG,
thanks to the superior performances of the new detector.
Additional improvements are expected with the data collected during the years 2023–2024.
The data-taking will continue in the coming years.
We report also on the ongoing activity for designing a future experiment for µ+ → e+ detection
with an expected improvement in sensitivity of an additional order of magnitude compared to the
full MEG II data set, based on gamma-ray converter and innovative technology for tracking.

Speaker: Paolo Walter Cattaneo (Istituto Nazionale di Fisica Nucleare)

10 Observation of the 𝐾⁺ → 𝜋⁺𝜈𝜈 decay and measurement of its branching ratio at NA62

Speaker: Francesco Brizioli (INFN Perugia (IT))

17:30 Welcome cocktail

Tuesday, 1 July

08:30 Registration

Morning session

11 TBA

Speaker: Serguey Petcov (Istituto Nazionale di Fisica Nucleare)

12 TBA

Speaker: Antonio Marrone (Istituto Nazionale di Fisica Nucleare)

13 TBA

Speaker: Michael Ratz (UC Irvine)

14 TBA

Speaker: Gui-Jun Ding (University of Science and Technology of China)

11:00 Coffee break

Morning session

15 TBA

Speaker: Mu-Chun Chen (University of California at Irvine)

16 CP violations of quarks and leptons in the setup with T^2/Z_3 orbifold compactification

CP invariance is a very attractive solution to the strong CP problem in QCD. This solution requires the vanishing phase of (det M_d det M_u) of the mass matrices for the down- and up-type quarks. It happens if we have several zeros in the quark mass matrices. We proceed a systematic construction of texture zeros for the quark sector in the T^2/Z3 orbifold compactification. We also extend the mass construction to the neutrino sector and derive predictions on the CP violating parameter in the neutrino oscillation and the mass parameter of neutrinoless double beta decay. We can naturally explain the positive sign of the baryon asymmetry in the present universe.

Speaker: Morimitsu Tanimoto (Niigata University)

12:30 Free time for lunch

Parallel session: 1-I

17 Neutrino mass sum rules from modular $A_4$ symmetry

In this talk, I will discuss a type-ii seesaw using the modular $A_4$ flavour symmetry. We propose a simple and minimalistic model that restricts the neutrino oscillation parameter space and, most importantly, introduces a sum rule in the physical neutrino masses. When combined with the mass squared differences observed in neutrino oscillations, this sum rule determines the absolute neutrino mass
scale. This has significant implications for cosmology, neutrinoless double beta decay experiments and direct neutrino mass measurements. In particular, the model predicts $\Sigma_i m_i \approx$ 0.1 eV for both normal and inverted ordering, and thus can be fully probed by the current generation of cosmological probes in the upcoming years.

Speaker: RANJEET KUMAR (Department of Physics, Indian Institute of Science Education and Research - Bhopal)

18 A SU(3)C x SU(3)L x U(1)X theory with A4 modular symmetry

A $SU(3)_C\times SU(3)_L \times U(1)_X$ extension of the gauge symmetry of the Standard Model with $A_4$ modular symmetry and radiative linear seesaw is proposed. The gauge extension of the SM offer an opportunity to add new scalar fields to the model that can be used in Yukawa interactions to construct the neutrino mass matrix. In addition, $A_4$ modular symmetry is used as a flavour symmetry to forbid some entries in the neutrino mass matrix at tree level but permitted at one-loop. This model can successfully accommodate the observables of the neutrino sector.

Speaker: Nicolás Andrés Pérez Julve (UTFSM)

19 Classification of Modular Symmetries in Type IIB Flux Landscape

In this work, we study modular symmetries in type IIB flux landscape by investigating symplectic basis transformations of period vectors on toroidal orbifolds.
To fix explicit cycles of a third-cohomology basis regarding the untwisted complex structure modulus, which is necessary to construct the period vectors, we find that the following two symmetries are required for the period vectors: (i) ``Scaling duality '' which is a generalized $S$-transformation of $PSL(2, \mathbb{Z})$ and (ii) the modular symmetries to be consistent with symmetries derived from mass spectra of the closed string in type IIB string theory.
Furthermore, by considering flux quanta on the cycles, we explore type IIB flux vacua on toroidal orientifolds and flux transformations under the modular symmetries of the period vectors.

Speaker: Takafumi Kai (Kyushu University)

20 Diffusion-model approach to flavor models: A case study for $S_{4}^\prime$ modular flavor model

We propose a numerical method of searching for parameters with experimental constraints in generic flavor models by utilizing diffusion models, which are classified as a type of generative artificial intelligence (generative AI). As a specific example, we consider the $S_{4}^\prime$ modular flavor model and construct a neural network that reproduces quark masses, the CKM matrix, and the Jarlskog invariant by treating free parameters in the flavor model as generating targets. By generating new parameters with the trained network, we find various phenomenologically interesting parameter regions where an analytical evaluation of the $S_{4}^\prime$ model is challenging. Additionally, we confirm that the spontaneous CP violation occurs in the $S_{4}^\prime$ model. The diffusion model enables an inverse problem approach, allowing the machine to provide a series of plausible model parameters from given experimental data. Moreover, it can serve as a versatile analytical tool for extracting new physical predictions from flavor models. References are arXiv:2503.21432 [hep-ph] and arXiv:2504.00944 [hep-ph].

Speaker: Satsuki Nishimura (Kyushu University)

Parallel session: 1-II

21 Dark Hypercharge Symmetry

The gauged $U(1)_X$ extensions of the Standard Model are some of the most popular and extensively studied new physics models. In most of these models the charges of SM fermions are fixed by gauge anomaly cancellations. While the literature extensively discusses anomaly cancellation solutions in which SM fermions are "vector-like" under new symmetry, chiral solutions in which SM fermions are chiral under new symmetry are not well explored. In this work, we explore a whole new class of gauged $U(1)_X$ models where the SM fermions are chiral under the new $U(1)_X$ symmetry which we call the Dark Hypercharge symmetry. We present a comprehensive set of solutions for gauge anomaly cancellation through the inclusion of three chiral dark sector fermions. We will focus on a particularly intriguing chiral solution and demonstrate, in a model-independent manner using only the $Z'$ interaction channel, that the lightest dark fermion, is a viable Dark Matter candidate, and it can meet all current Dark Matter constraints. We also discuss the related Dark Matter and collider phenomenology of such models.

Speaker: Rahul Srivastava (Indian Institute of Science Education and Research-Bhopal)

22 Lepton sector and dark matter phenomenology of a minimal two loop level inverse seesaw model

We propose a minimal extension of the SM where the tiny active neutrino masses arise from an inverse seesaw mechanism at two loop level. The phenomenological consequences of the proposed model in neutrino masses and mixings, charged lepton flavor violation and dark matter are analyzed in detail. We find that the current theory successfully complies with the constraints arising from neutrino oscillation experimental data, neutrinoless double beta decay, charged lepton flavor violating process, dark matter relic density and dark matter direct detection. The obtained rates for charged lepton flavor violating processes are within the reach of experimental sensitivity.

Speaker: Rocío Branada Balbontín (Universidad Técnica Federico Santa María)

23 Unifying Seesaw and Radiative Neutrino Mass Mechanisms with A₄ Symmetry: A Pathway to Dark Matter Stability

To address the smallness of neutrino masses and the observed large neutrino mixing, we propose a hybrid framework that synergistically combines the canonical seesaw mechanism with radiative mass generation. This model is embedded in the A₄ non-Abelian discrete flavor symmetry, whose spontaneous breaking generates correct neutrino mixing patterns and stabilizes dark matter through a conserved residual symmetry. We investigate the phenomenological consequences of this "discrete dark matter" paradigm, analyzing both Dirac and Majorana neutrino mass scenarios. The interplay between the seesaw and radiative mechanisms is shown to yield testable predictions for neutrinos (e.g., mixing angles, mass-squared differences) and dark matter (relic density, direct detection signatures). This work bridges high-scale symmetry-based models with low-energy observables, offering a unified approach to neutrino mass and dark matter stability.

Speaker: Biswajit Karmakar (University of Silesia in Katowice Poland)

24 Revisiting a Flavor Model with Dark Matter and Leptogenesis

We revisit a supersymmetric flavor model, where realistic lepton mass matrices arise from specific flavon vacuum alignments. The model accommodates both dark matter and baryogenesis: the lightest flavino acts as a dark matter candidate, and the observed baryon asymmetry is generated via thermal leptogenesis with next-to-leading order Yukawa interactions. We show that the model is consistent with neutrino oscillation data, relic abundance, and lepton flavor violation constraints. Implications for future experiments are also discussed.

Speaker: Yusuke Shimizu (Kaishi Professional U.)

Parallel session: 1-III

25 Anomalies in Hadronic B decays

In this paper, we perform fits to $B \to PP$ decays, where $B = \{B^0, B^+, B_s^0\}$ and the pseudoscalar $P = \{\pi, K\}$, under the assumption of flavor SU(3) symmetry [SU(3)$_F$]. Although the fits to $\Delta S=0$ or $\Delta S=1$ decays individually are good, the combined fit is very poor: there is a $3.6\sigma$ disagreement with the SU(3)$_F$ limit of the standard model (SM$_{\rm{SU(3)}_F}$). One can remove this discrepancy by adding SU(3)$_F$-breaking effects, but 1000\% SU(3)$_F$ breaking is required. The above results are rigorous, group-theoretically -- no dynamical assumptions have been made. When one adds an assumption motivated by QCD factorization, the discrepancy with the SM$_{\rm{SU(3)}_F}$ grows to $4.4\sigma$.

Speaker: Suman Kumbhakar

26 Probing light states in Flavor Experiments

I will describe how light states like a light sterile neutrino an an ALP( axion like particle) can be probed in various flavor experiments. I will discuss their signatures in B decays and also study the implications of these states in other sectors like rare Kaon decays and neutrino experiments. In particular I will discuss how these light states may resolve some of the existing $B$ anomalies.

Speaker: Prof. alakabha datta (University of Mississippi)

27 Tackling ALP searches in meson decays with ALPaca: a phenomenological approach

Part of the community has intensively searched for ALP signals, as well as conducted dedicated data analyses to identify potential evidence of New Physics compatible with an ALP, resulting in constraints on the ALP parameter space. Therefore, it is now the time to present a tool, ALPaca, that facilitates the combination among the different information on ALP physics.
The focus of this talk will be on a phenomenological analysis of the ALP theory using the most up-to-date data from flavour facilities, to show both the latest constraints and the potential of ALPaca to study the interplay between flavour and ALP physics.

Speaker: Marta Fuentes Zamoro (Universidad Autónoma de Madrid)

28 The role of nonperturbative dynamics in D-meson mixing

The theoretical predictions for the $D-\bar{D}$ mixing parameters fall significantly short of experimental measurements, with discrepancies spanning several orders of magnitude. This divergence is largely attributed to the Glashow–Iliopoulos–Maiani (GIM) mechanism, which suppresses leading-order contributions. However, higher-order corrections and nonperturbative effects have the potential to mitigate this suppression, particularly through flavor SU(3) symmetry breaking. In this work, we explore the long-distance contributions arising from nonlocal QCD condensates, incorporating for the first time the impact of mixed condensates within multiple models. Our results demonstrate an improvement in the predicted values of $D-\bar{D}$ mixing parameters by an order of magnitude, providing insights into the role of nonperturbative QCD dynamics. While the theoretical estimates remain below experimental values, this study represents a crucial step toward bridging the gap between theory and observation, highlighting the importance of nonlocal QCD effects in understanding $D-\bar{D}$ mixing.

Speaker: Lovro Dulibić (Boskovic Inst., Zagreb)

16:00 Coffee break

Parallel session: 2-I

29 Viable fit to neutrino observables in possible U(2) flavor models

The explanation of neutrino masses and mixing still represents one of the open questions of the so-called “SM flavor puzzle” today. The purpose of my work is to provide a possible explanation of this problem, introducing an extension of the Standard Model based on a continuous $U(2)$ flavor symmetry (which is locally isomorphic to $SU(2) \times U(1)$), indicated as $U(2)_F$. This symmetry is spontaneously broken by the VEVs of two scalar fields, called flavons. Since the flavon VEVs depend on small parameters $\epsilon_{\phi,\chi} \sim O(0.01)$, all hierarchies in fermion masses and mixings arise from powers of these small order parameters.
Assuming that neutrinos are Majorana particles and that the light neutrinos take mass via the type-I see-saw mechanism, we can obtain a list of possible structures for the neutrino mass matrix (which we call patterns), depending on the choice of the $U(2)_F$ quantum numbers for the three RH neutrino representations.
After a numerical fit of this matrices to the neutrino observables, we obtain 13 viable patterns, which provide us interesting predictions on neutrino observables, such as the effective electron neutrino mass $m_\beta$ and the effective Majorana neutrino mass $m_{\beta\beta}$, and also on BSM phenomena such as LFV decays.

Speaker: Mirko Rettaroli (Istituto Nazionale di Fisica Nucleare)

30 Lepton Flavor Violating decays in a realistic U(2) flavor model

Building on the realistic U(2) flavor model proposed a few years ago by Linster and Ziegler, we conduct a comprehensive study of possible neutrino mass textures arising from the seesaw mechanism. We identify a set of viable models that provide an excellent fit to low-energy Standard Model flavor observables including neutrinos. Additionally, within an Effective Field Theory framework, we analyze lepton flavor-violating decays in these models and examine their implications for the muon anomalous magnetic moment.

Speaker: Simone Marciano (IFIC - CSIC - University of Valencia)

31 Flavor-deconstructed neutrinos

A tentative approach to explain the flavor puzzle consists of embedding the Standard Model in a larger gauge symmetry that contains a separate gauge group for each fermion family. In such gauge non-universal (or flavor-deconstructed) theories, neutrinos pose some challenges. I will discuss existing ideas in the literature and present a simple model in which flavor deconstruction naturally leads to sequential dominance for both neutrinos and charged leptons, thus providing a viable explanation for the flavor structure of the lepton sector.

Speaker: Avelino Vicente (IFIC (CSIC - U. Valencia))

Parallel session: 2-II

32 Sterile neutrino DM production

The presence of a dark matter component in the Universe, together with the discovery of neutrino masses from the observation of the oscillation phenomenon, represents one of the most important open questions in particle physics today. A concurrent solution arises when one of the right-handed neutrinos, necessary for the generation of light neutrino masses, is itself the dark matter candidate. In this article, we study the generation of such a dark matter candidate relying solely on the presence of neutrino mixing. This tightly links the generation of dark matter with searches in laboratory experiments on top of the usual indirect dark matter probes. We find that the regions of parameter space producing the observed dark matter abundance can be probed indirectly with electroweak precision observables and charged lepton flavor violation searches. Given that the heavy neutrino masses need to lie at most around the TeV scale, probes at future colliders would further test this production mechanism.

Speaker: Salvador Rosauro Alcaraz (Istituto Nazionale di Fisica Nucleare)

33 Temperature evolution in the Early Universe and Freeze-in at stronger coupling

In this talk, I will discuss the freeze-in dark matter production mechanism at low reheating temperatures. The process is Boltzmann-suppressed if the dark matter mass is above the reheating temperature, and, in this case, the coupling to the thermal bath has to be significant to account for the observed dark matter relic density. As a result, the direct DM detection experiments can already probe such freeze-in models, excluding significant parts of parameter space. The forthcoming experiments will explore this framework further, extending to lower couplings and higher reheating temperatures.

Speaker: Catarina Cosme (U. Coimbra)

Parallel session: 2-III

34 Exploring Flavour Symmetries and Long-Lived Particles with the FASER Experiment

The FASER experiment at the LHC explores long-lived particles (LLPs) and their connections to flavour symmetries. Recent results include constraints on dark photons and axion-like particles (ALPs), which are often motivated by flavour-related dynamics, as well as the first detection of high-energy collider neutrinos, providing insights into neutrino flavour oscillations and constraints on heavy neutral leptons (HNLs). These findings offer complementary probes to other experiments, addressing key questions in flavour physics, particle interactions, and cosmology.

Speaker: Cristiano Sebastiani (CERN)

35 Is the NOVA-T2K tension pointing towards new physics beyond SM ?

The NOvA and T2K electron neutrino appearance data, show a persisting tension in the determination of the CP-phase delta_CP. We quantify the statistical level of the tension and point out that it may represent a hint of new physics BSM. In particular, we find a preference for flavor-changing non.standard neutrino interactions (NSI) at the non-negligible 2 sigma level. In addition, we point out that, in contrast to what happens within the standard 3-flavor scenario (where NOvA and T2K jointly prefer the inverted neutrino mass ordering), in the presence of NSI the two experiments jointly prefer the normal neutrino mass ordering, thus returning in agreement with all the remaining oscillation data, which favor the normal neutrino mass ordering.

Speaker: Antonio Palazzo (Istituto Nazionale di Fisica Nucleare)

36 Muon-decay parameters at COHERENT

We study the most general Lagrangian for muon decay at low energies, including light Dirac right-handed neutrinos ($\nu$WEFT), in the COHERENT experiment at the Spallation Neutron Source at Oak Ridge National Laboratory. Using the COHERENT data, we derive the first direct constraint on the Michel parameters governing the $\bar\nu_\mu$ energy distribution. We also discuss future sensitivities and assess the implications for the Lorentz structure of the interactions mediating muon decay.
We thus demonstrate that Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) measurements at spallation sources are valuable probes of muon decay physics.

Speaker: Sergio de la Cruz Alzaga (IFIC (CSIC-Universidad de Valencia))

Wednesday, 2 July

08:30 Registration

Morning session

37 MonoHiggsology

Flavor symmetry and other ideas beyond the standard model may be achieved using the dark sector, while keeping only the one SM Higgs doublet.

Speaker: Ernest Ma (University of California, Riverside)

38 TBA

Speaker: Salvador Centelles Chuliá (Instituto de Física Corpuscular (IFIC) / Universidad de Valencia (UV))

39 TBA

Speaker: Claudia Cornella (CERN)

40 TBA

Speaker: Sebastian Jaeger (University of Sussex)

11:00 Coffee break

11:30 Group photo

Morning session

41 TBA

Speaker: Enrico Nardi (Istituto Nazionale di Fisica Nucleare)

42 TBA

Speaker: Marco Nardecchia (Istituto Nazionale di Fisica Nucleare)

12:45 Free afternoon

20:00 Conference Dinner

Thursday, 3 July

08:30 Registration

Morning session

43 Quark and Lepton Mass Hierarchies from Modular Flavour Symmetry with Weightons

Speaker: Steve King (University of Southampton)

44 TBA

Speaker: Myriam Mondragon (Instituto de Fisica, UNAM)

45 TBA

Speaker: Thomas Kephart (Vanderbilt University)

46 TBA

Speaker: Giulia Ricciardi (Istituto Nazionale di Fisica Nucleare)

11:00 Coffee break

Morning session

47 TBA

Speaker: Silvia Pascoli (University of Bologna)

48 TBA

Speaker: Stefan Antusch (University of Basel)

12:30 Free time for lunch

Parallel session: 3-I

49 Leptogenesis with low-energy Dirac CP-violation

The present Baryon Asymmetry of the Universe (BAU) can be explained in the framework of the type-I seesaw mechanism for neutrino mass generation through leptogenesis (LG). The L-, C- and CP-violating processes involving the right-handed neutrinos can generate an early lepton asymmetry, which is later converted into the present BAU by sphalerons. Remarkably, all the necessary CP-violation necessary to explain the present BAU via LG can originate uniquely from the Dirac phase of the neutrino mixing matrix, thus providing a direct link to CP-violation in low-energy neutrino oscillations. I will review the state-of-the-art understanding of the LG mechanism and concentrate on the scenarios with low-energy Dirac CP-violation with either 2 or 3 right-handed neutrinos. Possibilities to test the discussed scenarios at low-energy neutrino experiments, at heavy neutral lepton searches and experiments looking at lepton flavour violation will also be presented.

Speaker: Alessandro Granelli (Istituto Nazionale di Fisica Nucleare)

50 Spontaneous CP violation, sterile neutrino dark matter and leptogenesis

We constructed a model for spontaneous CP symmetry breaking in five-dimensional space-time that solves the strong CP problem. To explain the nature of dark matter and the baryon asymmetry of the universe, three right-handed neutrinos and U(1) B−L gauge interaction are introduced in the bulk, in addition to the field contents of the Bento-Branco-Parada model. The wave-function profiles in the fifth dimension can suppress dangerous operators allowed by symmetries, and the scale of spontaneous CP symmetry breaking can be sufficiently large to be consistent with thermal leptogenesis. In this model, the lightest right-handed neutrino serves as dark matter with a mass of O(10) keV. This small mass and the necessarily small mixing are explained by the exponentially localized wave-function in the fifth dimension due to a bulk mass term. The correct relic abundance is achieved thanks to the U(1) B-L gauge interaction. The other heavy right-handed neutrinos explain the baryon asymmetry of the universe through leptogenesis.

Speaker: Norimi Yokozaki (Zhejiang University)

51 Vector-like quark doublets, weak-basis invariants and CP violation

Even though a fourth chiral generation of fermions is experimentally ruled out, the possibility of extending the SM with vector-like quarks (VLQs), where both chiral components transform the same way under SU(2)_L cannot be excluded. In particular, extensions of the SM involving isodoublet vector-like quarks with standard charges currently stand as the favoured candidate in explaining the Cabibbo Angle Anomalies. This stems primarily from the fact that they allow for both left-handed and right-handed charged currents. This feature of isodoublet VLQ models not only gives rise to a very rich phenomenology, but may also induce important new sources of CP violation. In turn, these sources are directly connected to the existence of additional CP-odd weak basis invariant (WBI) quantities, distinct from the single one present in the SM or those present in other VLQ models. In this talk we present these new WBI quantities and show how they may signal the presence of CP violation at extremely high energies. Moreover, we relate the structure and mass dimension of these WBIs to various types of effective rephasing invariant quantities arising from the interplay of LH and RH charged currents, thus inducing imprints on a variety of flavor observables that are unique to VLQ isodoublet extensions.

Speaker: José Bastos

52 Underpinnings of CP-Violation at the High-energy Frontier

I will present a general analysis for the discovery potential of CP-violation (CPV) searches in scattering processes at TeV-scale colliders in an effective field theory approach.
The CP-violating sector of the SMEFT framework will be examined in some well motivated limiting cases, based on flavour symmetries of the underlying heavy theory. In particular, we show that under naturality arguments of the underlying new physics (NP) and in the absence of (or suppressed) flavour-changing interactions, there is only a SINGLE operator which alters the top-Yukawa coupling, that can generate a non-negligible CPV effect from tree-level SMxNP interference terms. We find, however, that CPV from this operator is expected to be at best of O(1\%) and, therefore, very challenging if at all measurable at the LHC or other future high-energy colliders.
We then conclude that a potentially measurable CPV effect, of O(10\%), can arise in high-energy scattering processes ONLY if flavour-changing interactions are present in the underlying NP; in this case a sizable CPV effect can be generated at the tree-level by pure NPxNP effects and not from SMxNP interference. I will provide examples of CPV at the LHC and at a future e^+e^- collider to support these statements.

---

Based on:
e-Print: 2407.19021 (PLB 2025), e-Print: 2407.19021 (PRL 2023)

Speaker: Shaouly Bar-Shalom (Technion, Israel)

Parallel session: 3-II

53 Long live the heavy ALP!

We explore the viability of axion-like particle (ALP) effective field theories (EFTs) where the ALP mass $m_a$ is comparable to or larger than the symmetry-breaking scale $f_a$, challenging the conventional hierarchy $m_a < f_a$. Using a data-driven approach, we analise four key observables: the anomalous magnetic moments of the electron and muon, as well as decays ($\mu\to e\gamma$) and ($\mu\to 3e$), considering an ALP coupled only to the less massive charged leptons with both flavour conserving and violating possibilities. Focusing on high ALP masses ($m_a>1$ GeV), we find a viable parameter space where $m_a\geq f_a$ remains consistent with experimental data within 3$\sigma$. This study highlights the potential for non-traditional ALP mass hierarchies in EFT scenarios.

Speaker: Samuel Rosende Herrero (UAM)

54 Flavored Peccei-Quinn symmetries in the minimal νDFSZ model

In this talk, I will describe minimal DFSZ models extended with two right-handed neutrinos to realize the minimal type-I seesaw mechanism. The models incorporate flavored U(1) PQ symmetries that account for the observed pattern of quark and lepton masses and mixings. I will discuss the resulting phenomenology, including axion dark matter and cosmology, axion couplings to photons and fermions, highlighting the implications for flavor-violating axion interactions.

Speaker: José Rocha (CFTP-IST, Lisbon)

55 Axion framework with colour-mediated Dirac neutrino masses

I will discuss our recent paper arXiv:2501.13156 where we propose a KSVZ-type axion framework in which vector-like quarks (VLQ) and coloured scalars generate Dirac neutrino masses radiatively. The global Peccei-Quinn symmetry (under which the exotic fermions are charged) addresses the strong CP problem and ensures the Dirac nature of neutrinos. The axion also accounts for the observed cosmological dark matter. We systematically explore all viable VLQ representations. Depending on the specific scenario, the framework predicts distinct axion-to-photon couplings, testable through haloscope and helioscope experiments, as well as potentially significant flavor-violating quark-axion interactions.

Speaker: Aditya Batra (CFTP-IST, Lisbon)

56 QCD axion and inflation from modular flavor symmetry

We study the stabilization of an modulus by Coleman-Weinberg potential generated by coupling with matter fields, which is controlled by modular flavor symmetry. In this model we can not only regard the $\mathrm{Re}\,\tau$ direction as the QCD axion but also propose new potential model for inflation using the same potential.

Speaker: Komei Goto (Keio University)

Parallel session: 3-III

57 Flavor puzzle in three Higgs-doublet models: Insights from BGL and lessons from flavor data

We study a variant of the 3HDM, referred to as the BGL-3HDM, incorporating a U $(1)_1 \times U(1)_2$ symmetry, which can distinguish the primary sources of mass for different fermion generations. In the version considered here, the Yukawa matrices in the down-quark and charged lepton sectors are diagonal, thereby eliminating tree-level FCNCs in these sectors. FCNCs mediated by neutral nonstandard Higgses are confined to the up-quark sector only. No new BSM parameters are introduced by the Yukawa sector of the model, making it as economical as the NFC versions of 3HDM with a $U(1)_1 \times U(1)_2$ symmetry in terms of the number of free parameters. However, even in the down-quark and in the charged lepton sectors, flavor diagonal but nonuniversal Higgs couplings set this model apart from the NFC versions of the 3HDM.

Speaker: Miguel Levy (Basel University)

58 The Electric Dipole Moment of the electron in the decoupling limit of the aligned Two-Higgs Doublet Model

We present a discussion of model-independent contributions to the EDM of the electron.
We focus on those contributions that emerge from a heavy scalar sector that is linearly realized. In particular, we explore the decoupling limit of the aligned 2HDM.
In this model, Barr-Zee diagrams with a fermion loop produce logarithmically-enhanced contributions that are proportional to potentially large new sources of CP violation. In the decoupling limit these contributions are generated by effective dimension-6 operators via the mixing of four-fermion operators into electroweak dipole operators.
These logarithmic contributions are not present in more constrained versions of the 2HDM where a $\mathcal Z_2$ symmetry is imposed, since it controls the basis of effective operators needed to describe the new physics contributions to the electron EDM. Thus, the $\mathcal Z_2$ symmetry provides a suppression mechanism.
We then study how the experimental bounds on the electron EDM constrain the set of parameters of the aligned 2HDM.

Speaker: Juan Manuel Dávila Illán (IFIC (UV - CSIC))

59 Comparison between μ-μ+ and e-e+ colliders for charged Higgs production in the 2HDM

We study the phenomenology of the charged Higgs boson at future muon colliders. We investigate the pair production μ+μ-→H+H-, the single production μ+μ-→W±H∓, as well as the vector boson fusion (VBF) {e+e-,μ+μ-}→νν¯H+H-. We show that the neutral Higgs exchange diagrams in the muon collider case can lead to a significant boost in the cross sections through their Yukawa couplings. Our results for the muon collider are systematically compared to the corresponding ones at e+e- machines. It is demonstrated that the VBF e+e-→νν¯H+H- can compete with the mentioned 2→2 processes. We select benchmark points and perform signal-background analyses, taking into account detector simulations. We demonstrate the discovery region at 5σ and the excluded region at 2σ levels at a 3 TeV muon collider.

Speaker: Es-Said Ghourmin

60 Light states in real multi-Higgs models with spontaneous CP violation

In models with extended scalar sectors consisting of multiple Higgs doublets that trigger spontaneous electroweak symmetry breaking, one might expect that the abundance of dimensionful quadratic couplings in the scalar potential allows for a regime where, apart from the would-be Goldstone bosons and a neutral Higgs-like state, all new scalars have masses much larger than the electroweak scale. For models where CP invariance holds at the lagrangian level but is broken by the vacuum, one can show that such a reasonable expectation does not hold. When perturbativity requirements are placed on the dimensionless quartic couplings, the spectrum of the new scalars includes one charged and two additional neutral states whose masses cannot be much larger than the electroweak scale.

Speaker: Miguel Nebot (University of Valencia - IFIC)

16:00 Coffee break

Parallel session: 4-I

61 CP violation in $B_s\to \phi\mu^+\mu^-$ Decay at FCC-$ee$

The feasibility of the time-dependent $C\!P$ violation measurement $B_s^0 \to \phi(\to K^+K^-)\mu^+\mu^-$ at the FCC-$ee$ is discussed. Future $Z$-factories offer an ideal setting for measuring this decay due to the large statistics, clean environment, particle identification, and excellent vertexing capabilities. These precision measurements are interpreted in the Weak Effective Theory (WET), providing a comprehensive understanding of $C\!P$ properties of the potential New Physics (NP) in these rare decays.

Speaker: Jason Aebischer (CERN)

62 Vector boson fusion & associated production of Higgs bosons as an LHC signature of CP violation

A myriad of well-motivated beyond Standard Model (BSM) proposals encode new sources of CP violation (CPV) entirely within the bosonic sector. In such scenarios, it turns out that the simultaneous observation of several purely bosonic processes may expose this underlying CPV in an unambiguous fashion. The present study, which aims to provide a guiding framework for the upcoming HL-LHC era, explores the potential for observing such signatures within the economical complex two-Higgs doublet model (C2HDM). Specifically, we asses the observation prospects for promising combinations of gluon fusion, vector boson fusion and associated production processes which unequivocally signal the existence of CP violating bosonic couplings to the new scalar states.

Speaker: Álvaro Lozano Onrubia (IFT UAM-CSIC & Universidad Autónoma de Madrid)

63 Light Scalars in Custodial Symmetric Higgs Triplet Models

In the LHC regime, the mixing between doublet and triplet scalars enriches the phenomenology of the scalar sector. However, electroweak precision observables place stringent constraints on scalar multiplets larger than doublets under the SU(2)_L gauge group. Notable exceptions are the well-established Georgi-Machacek (GM) model and the recently proposed extended Georgi-Machacek (eGM) model – both of which are triplet scalar extensions of the Standard Model (SM) that preserve custodial symmetry at tree level. We investigate whether the GM and eGM models can accommodate a light Higgs boson, motivated by a series of results from the LHC and LEP suggesting the presence of a light scalar around 95 GeV. Taking into account the recently improved next-to-leading order (NLO) unitarity and positivity constraints, we perform a global fit to these LHC and LEP data on 95 GeV Higgs in addition to the flavor physics data, LHC data on the SM-like Higgs and on the direct searches of heavy Higgs bosons. The fit results indicate that NLO unitarity and vacuum stability place significant constraints on the allowed parameter regions for both models. Additionally, we find that recent flavor physics data, particularly the branching ratio of the $b \rightarrow s \gamma$ transition, impose stringent constraints on scenarios involving a light Higgs boson. In this talk, I will present the latest constraints on the model parameters in the presence of a 95 GeV scalar in both models. Finally, I will discuss the potential for studying new decay modes in the eGM model and present the bounds on their branching ratios from the global fit, which could be probed at the LHC and future colliders.

Speaker: Mr Subrata Samanta (Indian Institute of Technology Kanpur)

Parallel session: 4-II

64 Effective description of Nelson-Barr theories

In Nelson-Barr theories built to solve the strong CP problem, vector-like quarks (VLQs) transmit the spontaneous CP breaking from a scalar sector to the CP conserving version of the SM. We perform the full one-loop matching calculations at the CP breaking scale up to dimension five and partial matching calculations at the VLQ scale to track the relevant corrections to the theta parameter at low energy. We find that the additional dimension five operators indeed induce the RGE running of theta at one-loop. The effect is relevant when the separation between the CP breaking scale and the VLQ scale is large. We discuss some results for simple models, including a version based on non-conventional CP where the contribution at one-loop vanishes.

Speaker: Celso Nishi (Federal University of ABC)

65 Effective Operators and Abelian Mixing: Non-SUSY GUT with Superheavy Defects

We discuss an SO(10) model where a dimension five operator induces kinetic mixing between the abelian subgroups at the unification scale. We discuss gauge coupling unification and proton decay in this model, as well as the appearance of superheavy quasistable strings, which can explain the PTA data.

Speaker: Rinku Maji (Institute for Basic Science, CTPU-CGA)

Parallel session: 4-III

66 Searches for lepton-flavour violation in τ decays at Belle and Belle II

The Belle and Belle II experiments have collected a 1.6 ab$^{−1}$ sample of $e^+e^-$ collision data at center-of-mass energy near the $\Upsilon(nS)$ resonances. This sample contains approximately 1.5 billion $e^+e^- \to \tau^+ \tau^-$ events, which we use to search for lepton-flavour violating decays. We present searches for $\tau \to l \gamma$, tau decays into three leptons, $\tau^- \to K_S^0 l^- $ and $\tau^- \to l^- \alpha$ where $\alpha$ is an invisible scalar particle.

Speaker: Laura Salutari (Istituto Nazionale di Fisica Nucleare)

67 Lepton Mixing and charged Lepton Flavour Violation from Inverse Seesaw

We discuss Charged Lepton Flavour Violating (CLFV) signals in Inverse Seesaw (ISS) scenarios with 3+3 heavy sterile states and flavour and CP symmetries.

We distinguish between two options of these scenarios, each characterised by a different spectrum of the heavy sterile states and different forms of the couplings and mass matrices. For both options, different lepton mixing patterns are predicted depending on the choice of residual groups.

Compatibility of the scenario for both options with bounds on CLFV processes is studied, and bounds on the parameters are derived.

The possibility of distinguishing between the various choices of residual symmetries, as well as between the two different options, through such signals is also considered.

Speaker: Francesco Paolo Di Meglio (IFIC Valencia)

68 Charged Lepton Flavour Violating meson decays in seesaw models

The occurrence of neutrino oscillations demands the existence of flavour violation in the charged lepton sector. The relation between the branching ratios of different charged lepton flavour-violating (CLFV) decay modes depends on the details of the neutrino mass model. In this work, we consider the three types of simple seesaw mechanisms of neutrino masses and study the correlation between the radiative CLFV decays and the meson CLFV decays. We find that the meson CLFV decay branching ratios are negligibly small in the type-II seesaw mechanism, whereas they are constrained to be at least three (two) orders of magnitude smaller than the radiative CLFV decay branching ratios in the case of type-I (type-III) seesaw mechanism. Thus, the relationship between these two modes of CLFV decays helps in distinguishing between different types of seesaw mechanisms. If the branching ratios of CLFV decays of mesons are larger than those of radiative CLFV decays, it provides a strong hint that the neutrino mass-generating mechanism is more complicated than the simple seesaw.

Speaker: Pravesh Chndra Awasthi (Indian Institute of Technology Bombay, Mumbai, India)

Friday, 4 July

08:30 Registration

Morning session

69 Quantum Gravity and Flavor: Probing New Frontiers with Neutrinos

Quantum gravitational effects are expected to reveal themselves at extreme energies, cosmological distances, in a break-down of standard quantum mechanics, or in the breaking of global symmetries. Neutrinos offer a unique potential to probe such effects: they are perfect quantum probes, their masses may be related to lepton number or flavor and thus global symmetry breaking and extra-galactic neutrinos have been observed at energies up to the PeV scale. We discuss Lepton Number Violation, Quantum-Gravitational Decoherence, Altered Dispersion Relations, Holographic Scaling and Entanglement Measures and assess the future perspectives of such experimental probes of quantum gravity.

Speaker: Heinrich Päs

70 TBA

Speaker: Gustavo Burdman

71 TBA

Speaker: Jessica Turner (Durham University)

72 TBA

Speaker: Arsenii Titov (University of Padua and INFN)

11:00 Coffee break

Morning session

73 Selection rules for cLFV processes from residual flavour groups

We systematically investigate the possible phenomenological impact of residual flavour groups in the charged lepton sector. We consider all possible flavour charge assignments for abelian residual symmetries up to Z8. The allowed flavour structures of operators in Standard Model Effective Field Theory (up to dimension six) lead to distinctive and observable patterns of cLFV processes. We illustrate the relevance of such selection rules displaying the current bounds on and the future sensitivities to the new physics scale. These results demonstrate, in particular, the importance and discriminating power of searches for cLFV tau lepton decays and muonium to antimuonium conversion.

Speaker: Claudia Hagedorn (IFIC - UV/CSIC)

74 TBA

Speaker: Ivo de Medeiros Varzielas (CFTP, IST)

12:30 Free time for lunch

Afternoon session

75 TBA

Speaker: Monojit Ghosh (Ruđer Bošković Institute, Zagreb, Croatia)

76 Goofy Symmetries

Speaker: Andreas Trautner

77 Spontaneous CP Violation in an Axion Model: Implications for Leptonic Flavor and the Minimal Seesaw

We investigate an extension of the Dine–Fischler–Srednicki–Zhitnitsky (DFSZ) axion model that realizes spontaneous CP violation and explores its implications for leptonic flavor structure within the framework of the minimal seesaw mechanism. By introducing singlet heavy Majorana neutrinos and an additional complex singlet scalar, we construct the extended Yukawa and scalar sectors necessary for radiatively generating the CP-violating quartic couplings at the 1-loop level. We demonstrate that the CP phase arising from the spontaneous breaking of symmetry propagates into the lepton sector, influencing the Dirac neutrino mass matrix and, consequently, the CP-violating phases of the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix. A benchmark numerical analysis confirms the compatibility of the model with current neutrino oscillation data and illustrates how low-energy leptonic CP violation can originate from the extended scalar dynamics. This framework offers a coherent link between axion physics, spontaneous CP violation, and the flavor structure of neutrinos.

Speaker: Sin Kyu Kang (Seoul National University of Science and Technolofy)

16:00 Coffee break

16:30 End