Session P01: Dark Sector

Light Dark Matter eXperiment: A Missing-Momentum Search

The constituents of dark matter are still unknown, and the viable possibilities span a very large mass range. Specific scenarios for the origin of dark matter sharpen the focus on a narrower range of masses: the natural scenario where dark matter originates from thermal contact with familiar matter in the early Universe requires the DM mass to lie within about an MeV to 100 TeV. Considerable experimental attention has been given to exploring Weakly Interacting Massive Particles in the upper end of this range (few GeV – ~TeV), while the region ~MeV to ~GeV is largely unexplored. If there is an interaction between light DM and ordinary matter, as there must be in the case of a thermal origin, then there necessarily is a production mechanism in accelerator-based experiments. The most sensitive way, (if the interaction is not electron-phobic) to search for this production is to use a primary electron beam to produce DM in ?xed-target collisions. The Light Dark Matter eXperiment (LDMX) is a planned electron-beam fixed-target missing-momentum experiment that has unique sensitivity to light DM in the sub-GeV range. This contribution will give an overview of the theoretical motivation, the main experimental challenges and how they are addressed, as well as projected sensitivities in comparison to other experiments.   

Light Dark Matter eXperiment: The Search for Visible Decays

The particle nature of dark matter is still unknown, yet there are dark particle candidates spanning a large mass range. One of the simplest possibilities of dark matter's origin is one in which dark matter arose as a thermal relic from the hot early universe. In this case, its mass range is expected to be between 1 MeV to 100 TeV. Below 1GeV is not readily available to direct-detection experiments and is therefore largely unexplored in dark matter experiments. LDMX (Light Dark Matter Experiment) allows us to search for these dark particles. It will use the fact that the thermal freeze-out scenario requires that there be an interaction between dark matter and ordinary matter. If such an interaction exists, an electron beam might produce a dark photon through a fixed target collision. A significant loss of beam energy with no other observable particles could signal the production of one such dark particle. However, the dark photon can also decay back into a visible pair of particles: an event that would go unflagged in the current LDMX design. We investigate how well we could detect these visible events with slight modifications to the LDMX trigger and analysis strategy.   

Design and Construction of HV Cables and Splitter Boxes for the MilliQan Experiment

The MilliQan experiment seeks to further understanding of physics beyond the Standard Model via the detection of millicharged particles. These millicharged particles are thought to be attributable to dark particles, which come from a theory of dark matter and dark energy as a collection of dark particles and their interactions. The MilliQan experiment features two detectors: a bar detector and a slab detector. In total, 264 photmultiplier tubes (PMTs) used in the two detectors must be powered with high voltage (HV) cables. Splitter box design and construction was needed to split the 1 mA current emerging from 72 outputs of 6 CAEN HV source modules into 264 0.25 mA currents. HV cable construction was needed to connect the HV source modules to the splitter boxes and the PMTs. Successful development of the splitter boxes and HV cables will power the detectors needed to detect millicharged particles.   

Gravitational Wave Signatures of Asymmetric Dark Matter

Theories of asymmetric dark matter offer a simultaneous solution to two of the most intriguing open questions in particle physics: the nature of dark matter and the origin of the matter-antimatter asymmetry of the Universe. In this talk, I will discuss the prospects for probing this class of models using gravitational wave detectors. I will focus on a concrete theory in which the Standard Model gauge group is extended by an extra SU(2) symmetry, with the leptons forming doublets with new fermionic partners. One of those new fermions serves as a good candidate for particle dark matter. The extra SU(2) symmetry is broken at a high scale, leading to a successful baryogenesis mechanism through a strong first order phase transition in the early Universe. This results in the production of gravitational waves whose signatures can be searched for in upcoming gravitational wave experiments.   

Dark Matter Search in the Muon g-2 Experiment at Fermilab

Dark matter is one of the most interesting research topics in physics. Many particle physicists are trying to identify if because we know that dark matter could be a major component of a complete fundamental description of nature. The Muon g-2 Experiment at Fermilab measures the anomalous precession frequency of the muon. Oscillations of this precession frequency could be produced by dark matter coupling to muons. This talk will describe how we could observe DM signals in the Muon g-2 data. I will explain how we determine the Muon g-2 DM mass range sensitivity, and analysis strategies throughout the mass range. Finally, I will present the expected Muon g-2 experiment discovery/exclusion research in selected DM model-dependent scenarios.   

Vector boson dark matter in a classically conformal U(1) extension of the standard model

We consider a classically conformal U(1) extension of the Standard Model (SM). The U(1) symmetry is radiatively broken by the Coleman-Weinberg mechanism, after which the U(1) Higgs field Φ drives electroweak symmetry breaking via a mixed quartic coupling with the SM Higgs doublet with coupling constant λ_mix. The conformal system features a suppressed coupling g_h1h2h2 ~ λ_mix v_h (v_h= 246 GeV), likely due to the unique nature of the classically conformal potential, leading to a suppressed h→ΦΦ process which may evade future experimental limits. We consider the gauge boson of the new U(1) gauge sector, Z’, to be the dark matter candidate in the absence of kinetic mixing, and interpret constraints on the conformal model in the context of observed values for dark matter abundance.