Understanding gravity in the framework of quantum mechanics is one of the great challenges in modern physics. Along this line, a prime question is to find whether gravity is a quantum entity subject to the rules of quantum mechanics. It is fair to say that there are no feasible ideas yet to test the quantum coherent behaviour of gravity directly in a laboratory experiment. Here, I will introduce an idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator.

I discuss the construction of Grand Unified Theories (GUTs) featuring an accidental Peccei-Quinn symmetry. The emphasis is put on the possibility of predicting the axion mass.

Results will be presented on a recent search for the rare Higgs boson decay into a pair of muons by the CMS Collaboration (arXiv:2009.04363), using proton-proton collision data collected from the CERN Large Hadron Collider at a center-of-mass energy of 13 TeV. An excess of events is observed in data with a significance of 3.0 standard deviations compared to the null hypothesis, with an expected significance of 2.5 for the standard model Higgs boson, leading to the first evidence for a coupling of the Higgs boson to second generation fermions.

The excess in electron recoil events reported recently by the XENON1T experiment may be interpreted as evidence for a sizable transition magnetic moment µeµ of Majorana neutrinos. We show the consistency of this scenario when a single component transition magnetic moment takes values µeµ ϵ (1.65 - 3.42) × 10-11 µB. Such a large value typically leads to unacceptably large neutrino masses. In this paper, we show that new leptonic symmetries can solve this problem and demonstrate this with several examples. We first revive and then propose a simplified model based on SU(2)H horizontal symmetry.

The observation of neutrino oscillation implies that neutrinos have mass. The quest to understand the origin of the neutrino mass lies at the forefront of particle and nuclear physics. Search for neutrinoless double beta decay is one of the primary probes to understand the neutrino nature. Its discovery implies lepton-number violation, confirming the Majorana neutrino mass which is realized by introducing sterile neutrinos. The theoretical approach requires somewhat complicated processes connecting fundamental interactions to those at hadronic and nuclear levels.

I will introduce arguably the simplest extension of the Standard Model that leads to renormalizable long-range vector-mediated neutrino self-interactions. Discussing bounds on the parameter space, we will see that there are unconstrained regions with four-neutrino interactions of a strength similar to effective models that have been suggested to resolve the cosmological Hubble tension. In a different region of parameter space, the excess in electron recoil events recently observed by XENON1T could be explained by the solar neutrino flux.

Uniaxial anisotropic impurity immersed in liquid Helium 3 strongly influences the scattering properties of quasiparticles as well as the symmetry breaking scheme. When the temperature of the system continuously decreased, the symmetry of normal phase Helium-3 is broken sequentially into polar phase and polar-distorted B-phase. The Kibble-Lazarides-Shafi(KLS) domain wall attached on a cosmic string-like defect was observed in this process. By using the relative homotopy group, we find the KLS wall-strings in Helium-3 form a network.

Neutrino non-standard interactions (NSIs), possible sub-leading effects originating from new physics beyond the Standard Model may affect the propagation of neutrinos and eventually contribute to the measurements of neutrino oscillation parameters. In this talk, we shall discuss how NSIs will affect the determination of neutrino mass hierarchy and the Dirac CP phase. Considering the light (e.g., U(1)^\prime ) and heavy (e.g., \nu2HDM) mediator models, we shall discuss here how one can find a few sizable NSI parameters in these models.

The deficit of muons in the simulation of extensive air showers is a long-standing problem and the origin of large uncertainties in the reconstruction of the mass of the high energy primary cosmic rays. Hadronic interaction models re-tuned after early LHC data have a more consistent description of the muon content among them but still disagree with data.