In this talk, I will argue that the consistency of non-perturbative $\theta$-vacua in gauge theories and gravity predicts the presence of axion-like particles (ALPs) in the particle spectrum. This prediction also necessitates additional structures in these theories. Specifically, General Relativity incorporates Eguchi-Hanson instantons, which generate gravitational $\theta$-vacua. The...
The Quantum Technologies and Dark Matter research laboratory at the University of Western Australia has a rich history of developing precision tools for testing fundamental physics at low energies. This includes the efforts to discover “Beyond Standard Model” physics, including the nature of Dark Matter and the unification of Quantum Mechanics with General Relativity to help uncover a unified...
I will give an overview of recent theoretical developments in flavor physics.
In this talk I will present a general study of nucleon decay based on the SMEFT up to dimension 7. Our analysis takes into account RGE effects, and includes limits on the scale underlying each operator, an assessment of the possibility of flat directions, and correlations between decay modes assuming single-operator dominance. The talk is mainly based on 2312.13361.
A minimal scenario for the BSM physics, dubbed as the minimal cosmological standard model, will be introduced, and its key cosmological aspects will be discussed.
We are expecting high-precision observations from upcoming CMB surveys, such as the Simons Observatory, CMB-S4, and LiteBIRD, as well as from surveys of the large-scale structure, such as Rubin LSST, Euclid, DESI, PSF, SPHEREx, and Roman. Most of the observables from these independent surveys will be correlated due to their sky and redshift overlaps. Joint analysis of these surveys will be key...
The search for dark matter (DM) remains one of the most pressing challenges in modern physics. Detecting sub-GeV DM particles poses significant challenges for traditional Earth-based detectors due to their low collision energies. This talk presents a novel approach to overcome these limitations: blazar-boosted dark matter (BBDM). I will explore how active galactic nuclei (AGN) with jets...
We consider the capture of dark matter in neutron stars, and the heating caused by the subsequent thermalization and annihilation of that dark matter. We find that most of the dark matter’s kinetic energy is rapidly deposited in the star. We also discuss, for the first time, the annihilation of partially thermalized dark matter. We find that capture-annihilation equilibrium, and hence...
I discuss paradoxical situation in detection of the highest energy cosmic rays by Telescope Array and Pierre Auger experiments, in particular, a strong discrepancy between their results for cosmic ray fluxes at energies above the GZK cutoff. I also discuss ideas of new BSM physics and dark matter identity which could naturally resolve these paradoxes.
Capture and annihilation of WIMP-like dark matter in red giant stars can lead to faster-than-expected ignition of the helium core, and thus a lower tip of the red giant branch (TRGB) luminosity. We use Gaia data to place constraints on the dark matter-nucleon cross section using TRGB of 22 globular clusters with measured TRGB luminosities, and place projections on the sensitivity resulting...
We analytically calculate the spectrum of stochastic gravitational waves (GWs) emitted by expanding string loops on domain walls in the scenario where domain walls decay by nucleation of string loops. By introducing macroscopic parameters characterizing the nucleation of the loops, the stochastic GW spectrum is derived in a way that is independent of the details of particle physics models. In...
Mounting evidence suggests that planned and present gravitational-wave detectors may be sensitive to signatures from first-order phase transitions in the early universe. Here, we investigate the influence of heavy vector-like fermions on the phase transition. Specifically, we consider the recently-proposed "flavour transfer" model, where the SM flavour structure is augmented by a new...
I report the progress in the 5-loop QED computation of g-2. Currently, there seems to be discrepancy in the 5-loop results obtained by two groups. I am trying to get an independent result by using the lattice simulation on the FUGAKU supercomputer.
We study gravitational wave (GW) signatures from dark sector phase transitions as an explanation of the stochastic GW signal in the nHz range reported by the NANOGrav, Parkes and European Pulsar Timing Array (PTA) experiments. In contrast to earlier works, which have focused on fitting the PTA results with phenomenological phase transition parameters, we perform a detailed analysis of the GW...
Recently, there has been a lot of attention given to cosmological first-order phase transitions in various contexts. To achieve a strong first-order phase transition a flat symmetry-breaking potential is commonly required. For instance, a classically scale invariant potential can provide such a flat potential, $V \sim \phi^4 \log \phi$, albeit with a large dilution factor and run-away bubbles....
Current ton-scale direct detection experiments have begun observing solar neutrinos. We probe the weak mixing angle using existing direct detection data. Leveraging recent measurements of $^8$B solar neutrinos via coherent neutrino-nucleus scattering by PandaX-4T and XENONnT, we demonstrate that these experiments can probe the weak mixing angle in a region complementary to that of dedicated...
The standard model (SM) prediction of massless neutrinos is experimentally inconsistent. Introducing new high-energy physics allows for neutrino masses to be generated via effective operators in the SM. Naturally, the SM is therefore regarded as an effective field theory (EFT), namely the SMEFT, and calls for a complete EFT implementation of the new physics. This is especially poignant for so...
Several Pulsar Timing Array (PTA) collaboratiosn have recently announced strong evidence for a stochastic gravitational background (SGWB) at nanohertz frequencies. In the same frequency range, high precision astrometry with surveys like Gaia can offer complimentary constraints on SGWB by tracking the positions of a large number of distant sources. We review the astrometric response to SGWB...
The mass hierarchy problem is concerned with the large differences in scale present in our universe, namely between the Higgs mass ($125$ GeV) and the Planck mass ($10^{19}$ GeV). The Standard Model currently offers no explanation for this difference which prompts the investigation of other fundamental theories. It has been argued that scale invariance of physical laws may be a solution to...
It has been suggested for a long time that dark matter would form a density spike around a black hole. However, no promising evidence has been observed so far to verify this theoretical prediction. In this talk, I will report the evidence of showing the existence of a dark matter density spike surrounding each of the two nearby stellar-mass black holes (A0620-00 and XTE J1118+480) and in the...
We present a minimal framework that realises successful Dirac Leptogenesis through the Affleck-Dine mechanism. A single right-handed neutrino and a neutrinophillic Higgs doublet are introduced to the Standard Model, which couple via a Yukawa interaction. The inflationary setting is induced by a combination of the two Higgs doublets, with their global symmetry violating interactions leading to...
It has been recently proposed that the boosted dark matter (BDM) by supernova neutrinos (SN$\nu$) from SN1987a or from the next Galactic supernova (SN) can serve as a novel component to probe nonvanishing interaction between dark matter (DM) and the standard model leptons. In this talk, I will introduce the relevant concept and evaluate the present-day diffuse flux of SN$\nu$ BDM originated...
The question that what constitutes Dark Matter (DM) is one of the most pressing ones in contemporary physics, and one that has not been answered to any degree so far. Primordial Black Holes (PBHs) are one of the most well-motivated dark matter candidates. PBHs which are light enough that the Hawking radiation is substantial have been constrained by either the non-detection of the radiation...
Post-recombination cosmological probes offer some of the most stringent constraints on the properties of Dark Matter. The Cosmic Microwave Background (CMB), within the ΛCDM framework, has provided precise measurements of the Dark Matter density and its properties. Similarly, with upcoming 21cm experiments, the 21cm signal is a promising late-time cosmological probe, particularly sensitive to...
Composite Higgs Models offer an attractive solution to the hierarchy problem. We extend previously examined models based on a SO(5) → SO(4) symmetry breaking pattern and 3rd generation quarks, with two representations of the τ and its neutrino. We conduct Bayesian global fits of these models using a wide array of constraints in order to find regions in the parameter volume that best fit...
Is it possible to get leptogenesis to work in the Zee Model? Come to this talk and find out!
Several unified models that embed the SM elegantly have the possibility of domain wall formation according to Kibble mechanism. In models based on supersymmetric and non-supersymmetric left-right symmetric models, we discuss the emergence of such walls in the early universe and their signature in gravitational waves and the links to leptogenesis and EDM searches.
References...
BABAR performed the first two-dimensional unbinned angular analysis of the semileptonic decay $\bar B \rightarrow D \ell^- \bar \nu_\ell$ with the full data set, where $\ell$ is either an electron or a muon. The other $B$ meson is tagged via hadronic reconstruction. A novel data-driven signal-background separation procedure with minimal dependence on simulation has been developed that...
Irrefutable evidences from galaxy rotation curve, gravitational lensing and large scale structure of the Universe suggest that the present Universe is dominantly filled by an invisible matter, popularly called dark matter. In fact, the satellite based experiment PLANCK predicted that the relic density of dark matter, expressed in terms of Ω_Dm h^2=0.12±0.0012. However, the dark matter...
Minimal Flavor Violation (MFV) offers an appealing framework for exploring physics beyond the Standard Model. Interestingly, within the MFV framework, a new colorless field that transforms non-trivially under a global ${\rm SU}(3)^3$ quark flavor group can naturally be stable. Such a new field is thus a promising dark matter candidate, provided it is electrically neutral. We extend the MFV...
High statistics data sets collected in the region of the $\Upsilon(4S)$ resonance can provide extremely powerful tests of possible physics beyond the standard model. Searches with the BABAR experiment at the SLAC PEP-II $B$ factory have placed stringent constraints on possible dark-sector particles and interactions across a variety of models, for masses spanning the MeV - GeV range. Recent...
Metastable cosmic strings are gathering attention as potential progenitors of stochastic gravitational wave background. They result from a two-step symmetry breaking $G\to H\to 1$ with $\pi_1(G)=0$ and $\pi_1(H)\ne 0$, and decay via internal monopole-antimonopole pair creation.
Conventionally, the breaking rate has been estimated by an infinitely thin string approximation, which requires a...
We propose a class of dark matter models based on a chiral U(1) gauge symmetry acting on a dark sector. The chiral U(1) protects the masses of the dark sector fermions, and also guarantees the stability of the dark matter particle by virtue of an unbroken discrete Z_N gauge symmetry. We identify 38 such U(1) models which are descendants of a chiral SU(3)×SU(2) gauge symmetry, consisting of a...
Long Lived Particles (LLPs) are predicted in many models of possible physics beyond the Standard Model which seek to explain key questions in modern physics. The MATHUSLA experiment is a proposed LLP detection experiment for the CERN Large Hadron Collider (LHC). Consisting of a large decay volume instrumented with layers of scintillator tracking detectors positioned on the surface...
We study phenomenology of a light scalar dark matter (DM). In the model, there are an inert doublet scalar and a singlet Dirac fermion ψ, both charged under a global Z_2 symmetry. The mass of the lightest inert scalar H can be lighter than 10 GeV by imposing appropriate relations between three scalar quartic couplings. The lightest Z_2 odd particle is stable and DM. In this paper, focusing on...
Supersymmetry (SUSY) remains a leading candidate for physics beyond the Standard Model (SM). However, thus far, the LHC has not found any evidence of supersymmetry. The lower bound of the gluino mass exceeds 2 TeV and around 1 TeV for the stop in the bulk of parameter space. The fine-tuning of the electroweak symmetry breaking (EWSB) in the Minimal Supersymmetric Standard Model (MSSM) is...
We propose a scenario for cogenesis of baryon asymmetry and dark matter driven by Majoron. It can be achieved assuming either an initial kinetic motion or a conventional misalignment with symmetry non-restoration.
The talk consists of two parts:
(i) The recent excess in a rare decay of the Higgs boson $H\to Z \gamma$ can be interpreted using a light axion-like particle (ALP) in the mass range of $0.05 - 0.1$ GeV. The dominant decay of such a light ALP is into a pair of collimated photons, whose decay is required to happen before reaching the ECAL detector, such that it mimics a single photon in the...
The ultra-cold muon technology developed for the muon g − 2 experiment at J-PARC provides a low-emittance mu+ beam which can be accelerated and used for realistic collider experiments. We consider the possibility of new collider experiments by accelerating the mu+ beam up to 1 TeV. Allowing the mu+ beam to collide with a high-intensity e− beam at the TRISTAN energy, 30 GeV, in a storage ring...
Neutrinos are known to play crucial roles in core-collapse supernova explosions. The anticipated large amount of supernova neutrinos events from the next galactic explosion as well as the upcoming unambiguous detection of the diffuse supernova neutrino background are also expected to be important messengers to probe various important issues in astrophysical, nuclear, and particle physics....
The Hyper-Kamiokande project in Japan envisions a broad experimental program, including the discovery of charge-parity violation in neutrino oscillation, the search for nucleon decay and (indirectly) dark matter, and supernova neutrinos. This talk will describe the current status and efforts towards realizing this next generation experiment.
The observation of neutrino oscillations has shown that neutrinos are massive and hence that the Standard Model of particle physics has to be extended. In this talk I will discuss recent developments in neutrino theory which can guide experimental explorations of the neutrino sector.
Probing Seesaw Scale at a Cosmological Neutrino Collider
The Migdal effect describes the ionization rate of atoms during the scattering of heavy particles off atomic nuclei. It offers a new avenue for the search for dark matter particles with sub-GeV masses in liquid noble gas detectors. We propose a novel mechanism for atomic ionization, involving the complete absorption of dark matter particles upon interaction with atomic nuclei. Unlike inelastic...
Axions are an increasingly popular dark matter candidate with a flourishing experimental campaign now poised to discover them if they exist. However, there is a potential crisis lurking within this model which could make a discovery impossible, even if the axion does turn out to be the correct dark matter candidate. In one of the general classes of cosmological production scenarios—namely the...
The Belle II collaboration recently announced that they observed the B→ Kνν decay process for the first time. However, their result encounters a 2.7σ deviation from the Standard Model calculation. Additionally, Fermilab released new data on muon g − 2 away from the SM expectation with 5.1σ. In this talk, I would like to talk about the simplest UV-complete U(1)Lµ−Lτ-charged complex scalar Dark...
One of the exciting mysteries uncovered by the James Webb Space Telescope is the discovery of very high redshift supermassive black holes (SMBH). Such early formation of SMBH challenges conventional formation mechanisms---one possible explanation is that these black holes formed from the direct collapse of massive dust clouds. However, it has long been understood that the onset of cooling from...
The kinetic mixing can transfer the supersymmetry breaking from the hidden sector to the visible sector. We study dark gauge mediation supersymmetry breaking (dark GMSB) with large kinetic mixing. The massless dark photon allows such a large kinetic mixing, so the effect of the dark GMSB can become significant in the soft mass terms. For the neutralino sector, the dominant components in the...
Long-lived configurations of massive scalar fields around black holes may form if the coupling between the mass of the scalar field and the mass of the black hole is very small. In this work, we analyse the effect of self-interaction in the distribution of the long-lived cloud surrounding a stationary black hole. We consider both attractive and repulsive self-interactions.
As an elegant solution to the strong CP problem and promising dark matter candidate, the QCD axion is one of the best motivated particles beyond the SM. On the phenomenological side, it is extremely predictive as all its couplings to SM particles as well as its mass is determined by a single scale, the axion decay constant. The hunt for the QCD axion, both with terrestrial experiments as well...
From the perspective of Particle Physics, Dark Energy is a low energy phenomenon. Thus, our expectation is that field theory in curved space time should be sufficient to understand the physics of Dark Energy. However, in the context of the Standard Model of Particle Physics obtaining fields with sufficiently low masses that can be protected technically and be relevant for Dark Energy physics...
Radiative symmetry breaking (i.e. classically conformal) theories provide an appealing explanation for electroweak symmetry breaking and address the hierarchy problem. Such theories also imply one or more first-order phase transitions (FOPTs) in the early Universe, deeply affecting the thermal history and potentially providing novel solutions to puzzles of dark matter and baryon asymmetry....
Axions and Axion-Like-Particles (ALPs) are theoretically well-motivated candidates for dark matter that, due to their large occupation number, can be described as oscillating classical fields. At low energies, canonical QCD axions have a model-independent quadratic interaction with nucleons that can be extended to gluon-coupled ALPs. Nucleon densities modify the axion’s and ALP’s field...
Dark matter with mass in the crossover range between wave dark matter and particle dark matter, around $(10^{-3}, 10^3)$ eV, remains relatively unexplored by terrestrial experiments. In this mass regime, dark matter scatters coherently with macroscopic objects. The effect of the coherent scattering greatly enhances the accelerations of the targets that the dark matter collisions cause by a...
The present talk will cover an extension of a scotogenic and its modular $\mathcal{A}_4$ variation a step forward and demonstrates scotogenic modular $\mathcal{A}_4$ non-supersymmetric realization. To achieve this non-holomorphic modular symmetries come to rescue. Advantage of the current construction is the compactness of the model content and absence of the supersymmetric fields. Neutrino...
We propose a novel and comprehensive particle physics framework that addresses multiple cosmological tensions observed in recent measurements of the Hubble parameter, $S_8$, and Lyman-$\alpha$ forest data. Our model, termed `{\bf SIDR$+{z_t}$}' (Self Interacting Dark Radiation with transition redshift), is based on an inelastic dark matter (IDM) scenario coupled with dark radiation, governed...
The Strong CP Problem is solved elegantly and economically by endowing the Standard Model of Particle Physics with a new complex scalar, and a spontaneously broken, anomalous global Peccei-Quinn (PQ) symmetry whose Goldstone boson is called the axion. Unfortunately, this solution may be spoiled by the global symmetry-breaking effects generically expected to arise in any effective theory of...
We explore the $511$~keV emission associated to sub-GeV dark matter (DM) particles that can produce electron-positron pairs and form positronium after thermalizing. We use $\sim16$~yr of SPI data from INTEGRAL to constrain DM properties, including the full positron propagation and losses, and the free electron density suppression away from the Galactic plane. We show that the predicted...
We will discuss the models beyond the Standard Model (BSM) consisting of inverse seesaw (ISS) neutrinos and singly charged Higgs bosons, which accommodate all the data of neutrino oscillation, the (g-2)_{e_a} anomalies of muon and electron, and the lepton flavor violating (LFV) decays. We will show that one-loop contribution related to ISS neutrino exchanges can lead to large LFV decay rates...
During the last few decades, many experimental anomalies were reported and then most of them eventually disappeared. Very often they employ simplified or phenomenological models in order to interpret anomalous data. I will show a few examples where this common approach largely fails, and emphasize that it is important to interpret the anomalous data in mathematically consistent models.
The cosmic gravitational focusing (CGF) is the 3rd cosmological way of measuring the neutrino masses. Different from the existing methods with CMB and large scale structure that have linear dependence on the neutrino mass sum, CGF is sensitive to the fourth power of the neutrino masses and hence can provide an independent measurement of the neutrino mass. We thoroughly explore the cosmic...
False vacuum decay plays an important role in many branches of physics. In many systems, the initial state is in local thermodynamic equilibrium around the metastable minimum. For such systems the Euclidean path integral is a powerful tool to compute the decay rate or the shape of the true vacuum bubble. On the other hand, the Euclidean approach does not capture real-time dynamics of the phase...
The prospect of detecting/constraining deviations from general relativity by studying gravitational waves (GWs) from merging black holes has been one of the primary motivations of GW interferometers like LIGO/Virgo. Within pure gravity, the only possible way deviations can arise is from the existence of higher order derivative corrections, namely higher powers of the Riemann curvature tensor,...
The diffeomorphism invariance of a compactified five-dimensional theory of gravity is spontaneously broken by the background space-time geometry. In this talk we discuss the surprising properties of the scattering amplitudes of the massive spin-2 Kaluza-Klein modes of these theories, and explain the origin of these properties in terms of underlying hidden symmetries.
We revisit...
The diffeomorphism invariance of a compactified five-dimensional theory of gravity is spontaneously broken by the background space-time geometry. In this talk we discuss the surprising properties of the scattering amplitudes of the massive spin-2 Kaluza-Klein modes of these theories, and explain the origin of these properties in terms of underlying hidden symmetries.
