Particle Physics

If dark energy evolves in time its dynamical component could be dominated by a bath of dark radiation. Since dark energy was subdominant in the early universe, the dark energy radiation evades the usual stringent constraints on extra relativistic species from the cosmic microwave background, allowing for an O(1) fraction of the energy density today to be dark radiation. In this talk, I will discuss how dark energy radiation can emerge from a fundamental theory, its predictions for cosmological observables, as well as discovery potential and constraints with existing and future precision cosmological datasets including measurements of the cosmic microwave background, baryon acoustic oscillations, and supernova data. I’ll conclude with the prospects of measuring the particle content of the dark energy radiation in direct-detection experiments in the presence of interactions between the Standard Model and the dark radiation sector, focusing on neutrinos, axions and dark photons.

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Zoom link https://pitp.zoom.us/j/97180285756?pwd=aEtlYmFSRzFSZVBvY3lnMmtPYWc3Zz09

Higgs coupling deviations from Standard Model predictions contain information about two scales of Nature: that of new physics responsible for the deviation, and the scale where new bosons must appear. The two can coincide, but they do not have to. The scale of new bosons can be calculated by going beyond an effective field theory description of the coupling deviation. I will discuss model-independent upper bounds on the scale of new bosons for deviations in Higgs to WW and ZZ couplings, and explain how any measured deviation at present or future colliders requires the existence of new bosons within experimental reach. This has potentially interesting implications for naturalness.

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Zoom link https://pitp.zoom.us/j/97203814123?pwd=U3F3N2xxTmJSQmxIQ0Rib3ZwN3Fldz09

The QUEST-DMC experiment, aimed at detecting sub-GeV dark matter, utilizes a unique approach by employing superfluid Helium-3 (He-3) in conjunction with quantum sensors. Superfluid He-3 stands out as an ideal target medium for sub-GeV dark matter searches, especially in the context of spin-dependent interactions. This choice aligns seamlessly with a wide array of theoretically motivated dark matter models. The experiment's projected sensitivity to various dark matter models, as well as its potential to set upper limits on dark matter interactions, will be presented.

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Zoom link https://pitp.zoom.us/j/99386484623?pwd=dGVQdFJKbEpPMUcrRUNLbHdIR2p3Zz09

The rich EM phenomenology in the seconds, minutes, and hours just before, during, and after a compact object merger encodes the magnetization of the binary components, the nature of the post-merger remnant, the neutron star equation of state, the free neutron abundance, and a wide array of other compelling physics. Unfortunately, the requirement to search, find, and classify an electromagnetic counterpart within the large GW localization regions before targeted follow-up with sensitive instruments can begin, excludes access to these earliest times, even for the most well localized GW sources. The ability to promptly localize a GW source to within the field-of-view of a narrow-field sensitive facility, would enable extraordinary science. I will discuss the science cases that require extremely early time observations, and the coordination, instruments, and analyses necessary to achieve it. These include gamma-ray imaging, novel data analysis techniques, pre-merger GW detection, faster space telescopes, and new experiments.

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Zoom link https://pitp.zoom.us/j/96186614241?pwd=R0xpT0dDZVZzek5RT0x4Q1c3Z1RuUT09

The Callan Rubakov Effect describes the interaction between (massless) fermions and a smooth monopole in 4d gauge theory. In this scenario, the fermions can probe the UV physics inside the monopole core which leads to interesting effects such as proton decay in GUT models. However, the monopole-fermion scattering appears to lead to out-states that are not in the perturbative Hilbert space. In this talk, we will review this issue and propose a new physical mechanism that resolves this long-standing confusion.

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Zoom link: https://pitp.zoom.us/j/93551249905?pwd=REJvOUtTMlh6RU0vRjZnRVdZckgyZz09

SNOLAB is a laboratory two kilometers underground in Sudbury, Ontario, Canada. This laboratory boasts the lowest muon flux on Earth. This low muon flux is utilized for a variety of research on Quantum computing and the nature of dark matter, which are some of the highest priority research topics in fundamental and applied physics. New sensors are required for light dark matter searches that extend current capabilities by three orders of magnitude in energy. The required energy scales overlap with the energy scale of environmental disturbances that limit the coherence time of many candidate qubit systems, like superconducting circuits. I will give a short overview of SNOLAB. I will then focus on the requirements and alignment of light dark matter searches and cutting-edge qubit performance. Finally, I will say a few words on how future experiments can leverage these maturing quantum computing technologies for fundamental physics searches.

Zoom Link:  https://pitp.zoom.us/j/95345167872?pwd=eDhYREd2Q04yV21DUC84NnVEcHRmUT09

Despite first observing cosmic rays with energies above an EeV (10^18 eV) in the 1960s, the source of these particles remains an open question. Modern observatories, in particular the Pierre Auger Observatory and Telescope Array, have firmly established that the cosmic ray spectrum continues up to ~10^20.3 eV and have significantly advanced our understanding of these particles. However, limited statistics, uncertainties in particle physics, and significant deflections in the Galactic magnetic field have made progress towards discovering their astrophysical source extremely challenging. One key astrophysical input needed to understand ultrahigh energy cosmic ray data is the distribution of their sources, or the source evolution. In this talk, I will focus on multimessenger observations which have the potential to pin down the source evolution for the very first time.

Zoom Link:  https://pitp.zoom.us/j/94054513261?pwd=aHRNWE04VDI2cDA2RmRYQmtNRnd3dz09

Getting the strongest physics conclusions from collider particle physics experiments regarding the (in)consistency of the Standard Model with actual measurements requires Effective Field Theory techniques. This approach (known as the SMEFT) has been rapidly advanced in recent years, leading to new analyses of the data being executed by Atlas and CMS. The current state of the theoretical art is not precise enough as such EXP studies are continued into the future, as the measurements continue to become more precise. We need to be able to calculate more precisely in the SMEFT to keep up. After an intro to this area of research, I will discuss some recent calculations that have pushed things to the two loop level in precision for higgs production/decay in the SMEFT, and how thinking geometrically (in terms of field space connections and the resulting Higgs geometries) in EFT is the key to keep advancing the theoretical state of the art.

Zoom link:  https://pitp.zoom.us/j/99931154202?pwd=SUMzK2JIS0prNk5KaGZWakphckZhdz09

We study the low-energy effective action for relativistic superfluids obtained by integrating out the heavy fields of a UV theory. A careful renormalization procedure is required if one is interested in deriving the EFT to all orders in the light fields (at a fixed order of derivatives per field). The result suggests a general relation between finite density and spontaneous symmetry breaking for QFTs of interacting scalars with an internal global symmetry. The ground state at finite chemical potential of these systems is usually associated with a superfluid phase, in which the global symmetry is spontaneously broken along with Lorentz boosts and time translations. We show that this expectation is always realized at one loop for complex scalar fields with arbitrary UV potential in d > 2 spacetime dimensions. The physically distinct phenomena of finite charge density and spontaneous symmetry breaking occur simultaneously. We quantify this result by deriving universal scaling relations for the symmetry breaking scale as a function of the charge density, at low and high density. Moreover, we show that the critical value of μ coincides with the pole mass. The same conclusions hold non-perturbatively for an O(N) theory with quartic interactions in d = 3, at leading order in the 1/N expansion. In order to do this we compute analytically the one-loop effective potential at finite μ and zero temperature. As an application we derive in closed form the one-loop EFT for superfluid phonons for arbitrary UV scalar potentials in d > 2. From this we obtain analytically the one-loop scaling dimension of the lightest charge n operator in the $\phi^6$ conformal superfluid in d=3, at leading order in 1/n, reproducing a numerical result of Badel et al. 

Zoom Link:  https://pitp.zoom.us/j/97727675289?pwd=TWJyNzRucEhkM0JNM0NWeEdMM0xTQT09

The mixing angles of the quark sectors are constrained by unitarity in the standard model. However, recent data indicates a about 3 sigma deviation from unitarity in the mixing angle between the 1st and 2nd generation down-type quarks, known as the Cabibbo angle anomaly. The observations include the charged-current weak decays of neutrons, nuclei, kaons, and the hadronic decay of tau leptons. Although the issue appears to lie in the quark sector, modifying the neutrino sector may offer a solution. In this talk, we discuss recent findings that suggest a sterile neutrino of MeV mass mixing with the electron-type neutrino can resolve the Cabibbo angle anomaly. We also examine the current bounds and future prospects of this scenario.

Zoom Link:  https://pitp.zoom.us/j/98083942792?pwd=eHFRUmJUVGNJcVpTSHZXVXFKQm95QT09

I will discuss a novel search for axions using spectropolarimetric observations of magnetic white dwarfs (MWDs). Photons produced as thermal radiation at the MWD surface may convert into an axion as they traverse the magnetosphere, but only the component polarized parallel to the MWD magnetic field. Therefore the MWD radiation at Earth is linearly polarized perpendicular to the magnetic field direction. I detail the analysis of archival linear polarization spectra of a few nearby MWDs that excludes the axion interpretation of the TeV gamma-ray transparency anomalies. I briefly discuss the sensitivity of ongoing and future searches using dedicated data at the Lick Observatory.

Zoom Link:  https://pitp.zoom.us/j/97657182582?pwd=ZlFYWWtoYXhQZUtnOUxsZFpqMUo1Zz09

Precision measurements of primordial correlators in the CMB, Large Scale Structure, and 21-cm cosmology may contain “on-shell" imprints of extremely heavy particle physics, with masses comparable to the inflationary Hubble scale, via the remarkable inflationary mechanism known as “cosmological collider physics”. I will describe my research in (a) finding new robust mechanisms for extending the energy range and strength of such signals, (b) identifying motivated particle physics targets that may be discoverable, (c) showing how cosmological collider physics can probe the mechanism of inflation itself, and (d) demonstrating variants of the mechanism that may be observable in new cosmological “maps”, such as stochastic gravitational wave backgrounds with significant anisotropies. While this is an ambitious program of research, there are major challenges to bring it to fruition, on the experimental, phenomenological and theoretical fronts, which I will sketch. 

Zoom Link:  https://pitp.zoom.us/j/98923687484?pwd=cjgweEhoejVCeHAvc0RBSDEvVkZldz09