Session HH02: V: Particle Physics I

Upper Limits on WIMP Annihilation Cross Sections with IceCube DeepCore

Dark matter is approximately five times more abundant than baryonic matter, but its particle nature continues to elude physicists. One proposed candidate is a Weakly-Interacting Massive Particle (WIMP), which is predicted by supersymmetry and expected to have many of the observed properties of dark matter, including no electromagnetic interactions and interacting primarily via gravity and weak-scale forces. These weak-scale interactions open up the possibility of WIMPs annihilating into Standard Model particles like neutrinos, which are observable by neutrino detectors like IceCube. Under this hypothesis, IceCube can search for signals of neutrinos coming from WIMP annihilation, or set upper limits on the WIMP annihilation cross section in the event of a non-detection. One prime location for WIMP annihilation is a dwarf galaxy, which is relatively rich in dark matter and has a relatively low neutrino background compared to a Milky Way-sized galaxy. We present upper limits on the annihilation cross section for GeV-scale WIMPs annihilating in dwarf galaxies, highlighting a substantial improvement in the limits for WIMP annihilation into quarks.   

ADMX-G2 Run 2A: A Multi-Cavity QCD Axion Search

The QCD axion is among the best motivated particle dark matter (DM) candidates. Cavity haloscopes like ADMX (Axion Dark Matter eXperiment) resonantly detect conversion of DM axions to photons under a strong magnetic field in a high-Q resonant cavity. Recent ADMX runs with a single cavity excluded most of the QCD axion parameter range between 2.7µeV and 4.2µeV and are set to cover the range until about 5.4µeV. However, at higher masses the wavelength of the generated photons shrinks, generally leading to a smaller cavity volume and reduced sensitivity. In this talk we present an array of four cavities, tuning in sync to scan a broad mass range from 5.4µeV to 7.6µeV with QCD axion sensitivity. We discuss experimental measurements of the quality factor and other important electromagnetic characteristics at room temperature and 4K. We show recent R&D and experimental improvements, and outline the path towards commissioning and run of the full axion search experiment.   

Opening up baryon number violating operators

Baryon number violation is our most sensitive probe of physics beyond the

Standard Model. Its realization through heavy new particles can be conveniently encoded

in higher-dimensional operators that allow for a model-agnostic analysis. The unparalleled

sensitivity of nuclear decays to baryon number violation makes it possible to probe effective

operators of very high mass dimension, far beyond the commonly discussed dimension-six

operators. To facilitate studies of this ginormous and scarcely explored testable operator

landscape we provide the exhaustive set of baryon-number-violating operators up to mass

dimension 15, which corresponds roughly to the border of sensitivity, as well as their

explicit UV completions. In addition to the known Standard Model fields we also include

right-handed neutrinos in our operators.   

Constraining CP-odd contributions in the Higgs-strahlung process at FCC-ee using kinematic observables

Prospects to constrain CP-odd contributions in the Higgs-strahlung process at a future electron-positron collider e+e- => ZH are presented. A realistic study is performed in the framework of the FCC-ee collider at the center-of-mass energy of 240 GeV, with reconstruction of the IDEA detector performed using the DELPHES framework. A matrix-element package, MELA, is implemented that uses event weights to the Standard Model in order to optimally constrain the CP-odd contributions based on kinematic observables.   

Optimizing Observables for Experimental Measurements at the LHC

We present a framework for modeling processes with anomalous interactions at the LHC. One application of this framework is the modeling of the EFT in both on-shell and off-shell Higgs boson production and decay. We use this framework to illustrate the matrix-element approach in calculation of the observables optimal for EFT application and how most of the relevant information can be stored in an optimal way for data analysis.   

Probing the parameter space of two-dimensional QCD with eLCQ

Recently, exhaustively-symmetrized discretized light-cone quantization (eLCQ) has been applied to two-dimensional QCD with adjoint fermions (QCD_2A)

in the large N_c limit. The continuous method is complementary to discretized approximations of field theories. It is more suitable to adequately treat singularities

in bound-state equations, but so far limited to low parton numbers. The low-lying bound-state spectra of both massive and massless QCD_2A

have been computed and agree with previous results. This means that discretized approaches are not fundamentally flawed, even when tackling singular kernels. 

We show that eLCQ naturally generalizes to finite N_c, can be used to probe higher excited bound states in the large mass limit, and discuss application to other theories.   

Einstein's basement - A model of dark matter and dark energy?

The energy-momentum relationship (EMR) of a free particle in special relativity is regarded as the upper branch of an avoided crossing between the mass of the particle and its momentum. The corresponding EMR for the lower branch - a regime dubbed as Einstein's basement - is derived. From the associated Lagrangian and the conventional gravitational interaction a new kinematics in Einstein's basement is determined. It is shown that this can lead to a repulsion of the basement particles and a modified interaction with regular matter. The model suggests the identification of the basement particles with dark matter accompanied with a missing interaction with light. The expansion of the basement particles and the regular mass that is carried along could be interpreted as an expansion of the universe. Tests of the model by astronomical observations are suggested.