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Gao, Christina

Publications and source records attributed to Gao, Christina.

Tripling down on the W boson mass

A new precision measurement of the W boson mass has been announced by the CDF collaboration, which strongly deviates from the Standard Model prediction. In this article, we study the implications of this measurement on the parameter space of the SU(2) L triplet extension (with hypercharge Y=1) of the Standard Model Higgs sector, focusing on a limit where the new triplet is approximate Z 2 -odd while the SM is Z 2 -even. We study the compatibility of the triplet spectrum preferred by the W boson mass measured by the CDF-II experiment with other electroweak precision observables and Higgs precision data. We comprehensively consider the signals of new Higgs states at the LHC and highlighted the promising search channels. In addition, we also investigate the cosmological implications of the case in which the lightest new Higgs particle is either late decaying or cosmologically stable.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Searches for New Particles, Dark Matter, and Gravitational Waves with SRF Cavities

This is a Snowmass white paper on the utility of existing and future superconducting cavities to probe fundamental physics. Superconducting radio frequency (SRF) cavity technology has seen tremendous progress in the past decades, as a tool for accelerator science. With advances spear-headed by the SQMS center at Fermilab, they are now being brought to the quantum regime becoming a tool in quantum science thanks to the high degree of coherence. The same high quality factor can be leveraged in the search for new physics, including searches for new particles, dark matter, including the QCD axion, and gravitational waves. We survey some of the physics opportunities and the required directions of R&D. Given the already demonstrated integration of SRF cavities in large accelerator systems, this R&D may enable larger scale searches by dedicated experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Structure of Stellar Remnants with Coupling to a Light Scalar

In this paper we study how a Yukawa coupling of the Standard Model fermions to a light scalar field effects the stellar structure of cold stellar remnants such as neutron stars. We elucidate the stellar structure phenomenology using a simple model of a massive scalar coupled to a single dominant fermion with no other interactions. For a broad scalar mass range ($10^{-10}\,\mathrm{eV}\ll m_\phi\ll10^3\,\mathrm{eV}$ for neutron stars) we show that the equation-of-state and stellar structure depends only the effective coupling $\mathfrak{g}=\frac{g_f\,m_f}{m_\phi}$, where $g_f$ is the Yukawa coupling, $m_f$ the fermion mass and $m_\phi$ is the scalar kinematic mass at nuclear densities. If $\mathfrak{g}>\mathcal{O}(1)$ the Yukawa coupled matter exhibits various anomalous behaviors including hydrodynamic instability, negative pressure, distinct phases (soft and hard) of matter with sharp phase boundaries between them and with vacuum. These anomalies can lead to stars consisting of only soft, only hard or hybrid of soft and hard matter. These stars can have varying signs of the slope of the mass-radius relation, anomalously large and small masses, gaps in allowed radii, multiple radii for the same mass, very thin crusts and radiate anomalously large amounts of energy when they form (in the form of neutrinos for neutron stars). To the extent that these anomalies have not and/or will not be observed limits the effective coupling to $\mathfrak{g}<\mathcal{O}(1)$. We argue this phenomenology is generic to realistic models of stars with Yukawa coupled matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Axion searches with two superconducting radio-frequency cavities

We propose an experimental setup to search for Axion-like particles (ALPs) using two superconducting radio-frequency cavities. In this light-shining-through-wall setup the axion is sourced by two modes with large fields and nonzero $_E^→$∙$_B^→$ in an emitter cavity. In a nearby identical cavity only one of these modes, the spectator, is populated while the other is a quiet signal mode. Axions can up-convert off the spectator mode into signal photons. We discuss the physics reach of this setup finding potential to explore new ALP parameter space. Enhanced sensitivity can be achieved if high-level modes can be used, thanks to improved phase matching between the excited modes and the generated axion field. We also discuss the potential leakage noise effects and their mitigation, which is aided by O(GHz) separation between the spectator and signal frequencies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗