High Energy Physics Seminars This Term

The snowball chamber is analogous to the bubble and cloud chambers in that it relies on a phase transition, but it is new to high-energy particle physics. The concept of the snowball chamber relies on supercooled water, which can remain metastable for long time periods in a sufficiently clean and smooth container (on the level of the critical radius for nucleation). The results gleaned from the first prototype setup (20 grams) will be reviewed, as well as plans for the future, with an eye to future deployment of a larger (kg-scale) device underground for direct detection of dark matter WIMPs (Weakly Interacting Massive Particles), with a special focus on low-mass (GeV-scale) WIMPs, capitalizing on the presence of Hydrogen, which could potentially also lead to world-leading sensitivity to spin-dependent-proton interactions for O(1 GeV/c^2)-mass WIMPs and coherent neutrino scattering. Supercooled water also has the potential advantage of a sub-keV energy threshold for nuclear recoils, but this remains an atmospheric chemistry prediction that must be verified by careful measurements.

The Cryogenic Underground Observatory for Rare Events (CUORE) is a world leading cryogenic experiment searching for neutrinoless double beta decay (0vBB). CUORE is a one-tonne mass scale experiment, has been running since 2017, and has achieved statistics of one tonne-year worth of data taking. While no evidence of double beta decay has yet been found (with limit: T1/2 > 3.6 × 10^24 yr), CUORE can also be used to search for more exotic decay processes such as a triple proton decay. This talk will show how a data analysis framework built around machine learning can be used to classify different kinds of energy depositing events for counting experiments. A methodology which combines Poisson counting statistics with supervised classification machine learning tools is presented. Additionally, a sensitivity calculation is provided which uses the classification counting likelihood. Using the new analysis framework, we can achieve a preliminary lower 2σ half-life bound of 7.4×10^24yr for triple-proton decay of 130Te.

In this talk, I will briefly review the global effort in searching for axions, a hypothetical particle that can potentially address the strong CP problem, explain the nature of dark matter, and has deep connections with string theories. I will focus on a new resonance in the axion-photon system, axion magnetic resonance (AMR), that can greatly enhance the conversion rate between axions and photons. A series of axion search experiments rely on converting axions into photons inside a constant magnetic field background. A common bottleneck of such experiments is the conversion amplitude being suppressed by the axion mass when ma≳10−4 eV. I will show that a spatial or temporal variation in the magnetic field can cancel the difference between the photon dispersion relation and that of the axion, hence greatly enhancing the conversion probability. I will demonstrate that the enhancement can be achieved by both a helical magnetic field profile and a harmonic oscillation of the magnitude. Our approach can extend the projected ALPS II reach in the axion-photon coupling (gaγ) by two orders of magnitude at ma=10−3eV with moderate assumptions.

TBA

TBA

TBA

The MEG experiment, conducted at the Paul Scherrer Institut in Zurich, Switzerland, achieved a significant milestone in 2016 by establishing the best current upper limit of 4.2 × 10⁻¹³ for the branching ratio of the µ− > eγ decay process. The search for this decay holds tremendous potential for uncovering extensions to the Standard Model, as its existence would unequivocally signify the presence of new physics. To further amplify our sensitivity by an order of magnitude, we embarked on the development and construction of an upgraded apparatus known as MEG II in subsequent years. After conducting an engineering run in 2020 with a reduced set of electronic channels, MEG II officially commenced physics data collection in the summer of 2021 and is currently opertional. In this presentation, I will offer an overview of the subdetectors' performances and share our analysis results from the initial data set gathered in 2021. MEG II is commited to maintaining data acquisition until 2026 as we strive to atain our ultimate goal. This seminar will also shed light on the current status and future prospects of MEG II, including our investigations into other exotic phenomena, such as the exploration of a potential 17.6 MeV/c² particle originating from the 7Li(p,e+e-)7Be reaction.

TBA