Particle Physics

The axion solution to the strong CP problem has many virtues but it suffers from the so-called quality problem. This problem is avoided in heavy axion realizations which, however, are harder to probe experimentally. I will show how generic heavy axion models can be tested in current and future gravitational wave (GW) observatories, due to the cosmological GW background produced by the axionic topological defects. Moreover, the resulting GW signal is correlated with a sizable strong CP phase, within reach of upcoming neutron electric dipole moment measurements.

Zoom link:  https://pitp.zoom.us/j/99150077172?pwd=UWhkZVdzV2lCQittWXVtMnludXBkUT09

Any consistent regularization scheme induces an apparent violation of gauge invariance in non-anomalous chiral gauge theories. This violation shows up in perturbative calculations, and can be removed by including appropriate finite counterterms. In this talk I will discuss the derivation of such counterterms for a renormalizable chiral gauge theory.  I will use the background field method, which ensures background gauge invariance in the quantized theory. As a concrete application, I will show the finite counterterm at one loop in the Standard Model, within dimensional regularization and the Breitenlohner-Maison-'t Hooft-Veltman prescription for gamma5. 

Zoom Link: https://pitp.zoom.us/j/95507223984?pwd=Y0FDTEJpNDlVaE9Ba1ZNMURXeS9rdz09

New massive "dark" vector bosons are ubiquitous in BSM physics.  I'll discuss the effective theories, interactions, and applications of theories with a (single) massive vector boson with a Stückelberg mass, with the goal of providing a clear and self-consistent approach to the (sometimes confusing) subject.  The critical role of possible couplings of the longitudinal mode will be emphasized, demarcating when theories have amplitudes that grow with energy.  In such theories, I'll identify the cutoff scale, as well as show the potential of longitudinally-enhanced observables given specific couplings of the vector boson.  The Stückelbergian approach to massive vectors also provides insight into generalized dark vector boson theories; I'll demonstrate a specific application to an "electrophobic" vector field that can evade many terrestrial experiment constraints that would otherwise apply to a dark photon.

Zoom Link: https://pitp.zoom.us/j/96937794653?pwd=cjIvM0hxQmo2ZEhuamhxeWx3cVdoZz09

The cosmic radio background (CRB) contains diffuse, discrete and cosmological emission sources from the universe. In this talk, I will discuss  wether an additional contribution coming from low frequency photons is produced by free-free emission during the recombination era of the univers. These photons do not readily thermalise with the electron-proton plasma and therefore might  survive as a small non-thermal relic in the current universe.  Inclusion of such a contribution can alleviate the observed tension between existing CRB models and explain radio source counts between $100 MHz$ to $10 GHz$ to a very high degree of precision.  I will also discuss the challenges and future work we must considere in order to establish wether the signal is created or not.

Zoom Link: https://pitp.zoom.us/j/99032512514?pwd=eldocVA2VHhoUGVudmtFN3F4NHNEQT09

In this talk, I will present MicroBooNE's first results probing the nature of the excess of low-energy interactions observed by the MiniBooNE collaboration. The talk will cover all four electron neutrino analyses that comprise MicroBooNE's first results, with a particular focus on the exclusive search for CCQE-like electron neutrino interactions containing one electron and one proton in the final state (1e1p). The result of the 1e1p analysis, along with results from the other electron analyses and the single-photon analysis, will be discussed in terms of their implications for the MiniBooNE excess. Specifically, I will examine the viability of the single sterile neutrino explanation of the MiniBooNE excess in light of the MicroBooNE electron neutrino results. Additionally, I will introduce the Coherent CAPTAIN-Mills (CCM) experiment at Los Alamos National Laboratory. CCM has unique sensitivity to a number of exotic BSM models, including leptophobic vector-portal dark matter and axion-like particles, some of which may be able to explain the MiniBooNE anomaly.

Zoom Link: https://pitp.zoom.us/j/93290406752?pwd=ajIvZkhvVU5YMW90WjVpU3IySUphdz09

Muons are the archetypal ‘who ordered that?’ surprise discovered in cosmic rays and fittingly, recent muon measurements including g–2 could be challenging standard paradigms again. Remarkably, tau g–2 remains poorly constrained but can be 280 times more sensitive to new physics than the muon. Recently, ATLAS and CMS announced groundbreaking measurements of tau g–2 using the landmark observation of tau pairs created via photon collisions in LHC heavy-ion data. Beyond colliders, quantum sensing progress enables next-generation haloscopes to illuminate axion-like origins of dark matter above microwave frequencies. This motivates the Broadband Reflector Experiment for Axion Detection (BREAD) proposal at Fermilab and its interdisciplinary science program bridging astronomy, particle physics, and quantum technology.

Zoom Link: https://pitp.zoom.us/j/95937524952?pwd=eFVaTXVXOHBiNE9TZk9oMGNxRUwyQT09

Direct detection searches for dark matter are typically optimized to search for weakly interacting particles with masses on the ~GeV scale. But these experiments are, in principle, sensitive to masses as large as approximately the Planck mass, for cross sections much larger than typical Weak-scale cross sections. However, certain assumptions typically made in direct detection analyses break down at such large cross sections, and must be reexamined. In my talk, I will discuss the theoretical considerations that become important for heavy, strongly interacting dark matter, as well as new types of dark matter search that become possible at such high masses and cross sections.

Zoom Link: https://pitp.zoom.us/j/98807962972?pwd=UXFWLzA0N2dPQ3JrVUo4TStmSGtWUT09

I review the main mechanisms that convert fundamental CP-violating parameters (theta_QCD and Kobayashi-Maskawa phase) to the observable electric dipole moments (EDMs). Given recent progress, the EDMs connected to electron spin (paramagnetic EDMs) are calculated. The limit on QCD theta angle is 3 * 10^(-8) and  somewhat subdominant to neutron EDM, but can be improved. The Kobayashi-Maskawa phase contributes to paramagnetic EDMs at the level of 10^{-35} e cm in units of equivalent electron EDM, which is much larger than what was previously expected.  

Zoom Link: https://pitp.zoom.us/j/96502704646?pwd=ZThQWGU2dEZPWjdPQnp2ZEpPVXRIdz09

The possibility of having DM (or a fraction of it) charged under a dark U(1) which mixes with the U(1)EM has been of interest for many years. Many different experiments search for such a millicharged DM (MCDM), under the assumption that its velocity would be distributed according to MB. However, our galaxy and local environment have a variety of effects that make this assumption highly non trivial. In this talk, I will discuss the effects of galactic magnetic fields, collisions with Cosmic rays, acceleration from Supernovae remnants, and energy losses due collisions with particles in the interstellar medium on the velocity distribution of MCDM outside the solar system. Furthermore, to arrive at an underground detector, the MCDM would need to pass through the solar wind, not be deflected by earth's magnetic field, and pass through earth's crust to reach the underground lab. We will discuss these effects as well. I will end the talk by discussing the importance of these effects on Direct Detection experiments, and whether MCDM could explain the XENON excess.

Zoom Link: https://pitp.zoom.us/j/92701168758?pwd=UlY5Smlrd1MzWmI4ZkNyNVI5d3JIUT09

Quasi-sterile neutrinos are a natural consequence of dark sectors interacting with the Standard Model (SM) sector via neutrino- and vector-portals. Essentially, quasi-sterile neutrinos are light dark sector fermions with two generic properties: (i) they mix with the active neutrinos of the SM, and (ii) they are charged under a vector mediator that couples feebly to SM matter. Various interesting phenomenological consequences result from this class of particles. In this talk, I will discuss one such consequence: new, beyond the SM matter effects that can alter in-medium neutrino oscillations. In particular, for special windows of energy and matter densities, active neutrinos can resonantly oscillate into sterile neutrinos. I will discuss how this feature could be exploited to build a quasi-sterile neutrino model that can explain the MiniBooNE and LSND anomalies, while remaining compatible with observations from long-baseline reactor- and accelerator-based neutrino experiments. I will also discuss the implications to this model from the recent MicroBooNE results, and, time permitting, from solar neutrino measurements.

Zoom Link: https://pitp.zoom.us/j/95362454210?pwd=RzNCeDRkMjJXb2xNbHNkcEc1ZTdkUT09

Solar neutrinos are an inevitable background to any dark matter direct detection experiment as they closely mimic the signature of dark matter. In this talk, I will discuss the effects of solar neutrinos on the reach of dark matter-electron scattering experiments, with a focus on semiconductor and xenon-based detectors. In addition, I will present the prospects of measuring and understanding the various solar neutrino components using the same detectors, as well as the effects of non-standard neutrino interactions, thus turning solar neutrinos from a background to an interesting signal in their own right.

I will discuss electromagnetic signals generated by gravitational waves (GWs) in resonant cavity experiments.  Experiments designed for the detection of axion dark matter only need to reanalyze existing data to search for GWs in the GHz range with strains as small as h ∼ 10^{−22} − 10^{−21}. This is still far from the BBN bound on primordial sources, but it is the best direct constraint that we can currently obtain in the laboratory. To get to this result I will correct some long standing misconceptions present in the literature.

Zoom Link: https://pitp.zoom.us/j/94313100053?pwd=bWk1eHh3NWM3NnB1TjR5d0xrY3BIUT09