arXiv subjects

James B. Dent

Publications and source records attributed to James B. Dent.

At least 37 records · Page 2Linked to original sources

arXiv2021

Pathfinder for a High Statistics Search for Missing Energy In Gamma Cascades

We investigate the feasibility of a high statistics experiment to search for invisible decay modes in nuclear gamma cascades using 200 kg of %36 Cs(Tl) scintillators that are presently available at Texas A\&M. The experiment aims to search for missing energy by robustly establishing the absence of a photon in a well identified gamma cascade. We report on the experimental demonstration of the energy resolution necessary for this search. Prior explorations of this detector concept focused on baryonically coupled physics that could be emitted in $E_2$ transitions. We point out that this protocol can also search for particles that are coupled to photons by searching for the conversion of a photon produced in a gamma cascade into a hidden particle. Examples of these processes include the oscillation of a photon into a hidden photon and the conversion of a photon into an axion-like-particle either in the presence of a magnetic field or via the Primakoff process. This proof-of-concept apparatus appears to have the ability to search for hitherto unconstrained baryonically coupled scalars and pseudoscalars produced in $E_0$ and $M_0$ transitions. If successfully implemented, this experiment serves as a pathfinder for a larger detector with greater containment that can thoroughly probe the existence of new particles with mass below 4 MeV that lie in the poorly constrained supernova ``trapping window'' that exists between 100 keV and 30 MeV.

hep-ph↗

arXiv2021

Inverse Primakoff Scattering as a Probe of Solar Axions at Liquid Xenon Direct Detection Experiments

We show that XENON1T and future liquid xenon (LXe) direct detection experiments are sensitive to axions through the standard $g_{aγ}aF\tilde{F}$ operators due to inverse-Primakoff scattering. This previously neglected channel significantly improves the sensitivity to the axion-photon coupling, with a reach extending to $g_{aγ} \sim 10^{-10}$ GeV$^{-1}$ for axion masses up to a keV, thereby extending into the region of heavier QCD axion models. This result modifies the couplings required to explain the XENON1T excess in terms of solar axions, opening a large region of $g_{aγ}$ - $m_a$ parameter space which is not ruled out by the CAST helioscope experiment and reducing the tension with the astrophysical constraints. We explore the sensitivity to solar axions for future generations of LXe detectors which can exceed future helioscope experiments, such as IAXO, for a large region of parameter space.

hep-ph↗

arXiv2020

Gamma Ray Signals from Cosmic Ray Scattering on Axion-Like Particles

Dark Matter (DM) may be comprised of axion-like particles (ALPs) with couplings to photons and the standard model fermions. In this paper we study photon signals arising from cosmic ray (CR) electron scattering on background ALPs. For a range of masses we find that these bounds can place competitive new constraints on the ALP-electron coupling, although in many models lifetime constraints may supersede these bounds. In addition to current Fermi constraints, we also consider future e-Astrogram bounds which will have greater sensitivity to ALP-CR induced gamma-rays.

hep-ph↗

arXiv2020

Present and future status of light dark matter models from cosmic-ray electron upscattering

Non-relativistic Dark Matter (DM) can be accelerated by scattering on high-energy cosmic-ray (CR) electrons. This process leads to a sub-population of relativistic or semi-relativistic DM which extends the experimental reach for direct detection in the sub-GeV mass regime. In this paper we examine the current and future potential of this mechanism for constraining models of light dark matter. In particular, we find that Super-Kamiokande and XENON1T data can already provide leading constraints on the flux of dark matter that has been accelerated to high energies from cosmic ray electrons. We also examine future projected sensitivities for DUNE and Hyper-K, and contrary to previous findings, conclude that DUNE will be able supersede Super-K bounds on cosmic-ray upscattered DM for a variety of DM models.

hep-ph↗

arXiv2020

Explaining the XENON1T excess with Luminous Dark Matter

We show that the excess in electron recoil events seen by the XENON1T experiment can be explained by relatively low-mass Luminous Dark Matter candidate. The dark matter scatters inelastically in the detector (or the surrounding rock), to produce a heavier dark state with a ~2.75 keV mass splitting. This heavier state then decays within the detector, producing a peak in the electron recoil spectrum which is a good fit to the observed excess. We comment on the ability of future direct detection datasets to differentiate this model from other Beyond the Standard Model scenarios, and from possible tritium backgrounds, including the use of diurnal modulation, multi-channel signals etc.,~as possible distinguishing features of this scenario.

hep-ph↗

arXiv2020

A Physics Modeling Study of SARS-CoV-2 Transport in Air

The health threat from SARS-CoV-2 airborne infection has become a public emergency of international concern. During the ongoing coronavirus pandemic, people have been advised by the Centers for Disease Control and Prevention to maintain social distancing of at least 2 m to limit the risk of exposure to the coronavirus. Experimental data, however, show that infected aerosols and droplets trapped inside a turbulent puff cloud can travel up to 7 to 8 m. We propose a nuclear physics analogy-based modeling of the complex gas cloud and its payload of pathogen-virions. We show that the cloud stopping range is proportional to the product of the puff's diameter and its density. We use our puff model to determine the average density of the buoyant fluid in the turbulent cloud. A fit to the experimental data yields $1.8 < ρ_P/ρ_{\rm air} < 4.0$, where $ρ_P$ and $ρ_{\rm air}$ are the average density of the puff and the air. We demonstrate that temperature variation could cause an ${\cal O}(\pm 8\%)$ effect in the puff stopping range for extreme ambient cold or warmth. We also demonstrate that aerosols and droplets can remain suspended for hours in the air. Therefore, once the puff slows down sufficiently, and its coherence is lost, the eventual spreading of the infected aerosols becomes dependent on the ambient air currents and turbulence.

physics.bio-ph↗

arXiv2020

Flipped Quartification and a composite $b$-quark

An alternative "flipped" version of the quartification model is obtained by rearrangement of the particle assignments. The model has two standard (trinification) families and one flipped quartification family. An interesting phenomenological implication is that the model allows for a composite $b$-quark.

hep-ph↗

arXiv2020

The Sound of Clearing the Throat: Gravitational Waves from a Black Hole Orbiting in a Wormhole Geometry

Current ground-based gravitational wave detectors are tuned to capture the collision of compact objects such as stellar origin black holes and neutron stars; over 20 such events have been published to date. Theoretically, however, more exotic compact objects may exist, collisions of which should also generate copious gravitational waves. In this paper, we model the inspiral of a stellar mass black hole into a stable, non-spinning, traversable wormhole, and find a characteristic waveform -- an anti-chirp and/or burst -- as the black hole emerges, i.e., outspirals, into our region of the Universe. This novel waveform signature may be useful in searches for wormholes in future gravitational wave data or used to constrain possible wormhole geometries in our Universe.

gr-qc↗

arXiv2020

New Directions for Axion Searches via Scattering at Reactor Neutrino Experiments

Searches for pseudoscalar axion-like-particles (ALPs) typically rely on their decay in beam dumps or their conversion into photons in haloscopes and helioscopes. We point out a new experimental direction for ALP probes through their production via the Primakoff process or Compton-like scattering off of electrons or nuclei. We consider ALPs produced by the intense gamma ray flux available from megawatt-scale nuclear reactors at neutrino experiments through Primakoff-like or Compton-like channels. Low-threshold detectors in close proximity to the core will have visibility to ALP decays and inverse Primakoff and Compton scattering, providing sensitivity to the ALP-photon and ALP-electron couplings. We find that the sensitivity to these couplings at the ongoing MINER neutrino experiment exceeds existing limits set by laboratory experiments and, for the ALP-electron coupling, we forecast the world's best laboratory-based constraints over a large portion of the sub-MeV ALP mass range.

hep-ph↗

arXiv2020

The Migdal Effect and Photon Bremsstrahlung in effective field theories of dark matter direct detection and coherent elastic neutrino-nucleus scattering

Dark matter direct detection experiments have limited sensitivity to light dark matter (below a few GeV), due to the challenges of lowering energy thresholds for the detection of nuclear recoil to below $\mathcal{O}(\mathrm{keV})$. While impressive progress has been made on this front, light dark matter remains the least constrained region of dark-matter parameter space. It has been shown that both ionization and excitation due to the Migdal effect and coherently-emitted photon bremsstrahlung from the recoiling atom can provide observable channels for light dark matter that would otherwise have been missed owing to the resulting nuclear recoil falling below the detector threshold. In this paper we extend previous work by calculating the Migdal effect and photon bremmstrahlung rates for a general set of interaction types, including those that are momentum-independent or -dependent, spin-independent or -dependent, as well as examining the rates for a variety of target materials, allowing us to place new experimental limits on some of these interaction types. Additionally, we include a calculation of these effects induced by the coherent scattering on nuclei of solar or atmospheric neutrinos. We demonstrate that the Migdal effect dominates over the bremsstrahlung effect for all targets considered for interactions induced by either dark matter or neutrinos. This reduces photon bremsstrahlung to irrelevancy for future direct detection experiments.

hep-ph↗

arXiv2019

Bounds on Cosmic Ray-Boosted Dark Matter in Simplified Models and its Corresponding Neutrino-Floor

We study direct detection bounds on cosmic ray-upscattered dark matter in simplified models including light mediators. We find that the energy dependence in the scattering cross section is significant, and produces stronger bounds than previously found (which assumed constant cross sections) by many orders of magnitude at low DM mass. Finally, we compute the "neutrino-floor" that will limit future direct detection searches for cosmic ray-upscattered dark matter. While we focus on vector interactions for illustration, we emphasize that the energy dependence is critical in determining accurate bounds on any particle physics model of Dark Matter-CR interactions from experimental data on this scenario.

hep-ph↗

arXiv2019

Catching p via s wave with indirect detection

For many dark matter models, the annihilation cross section to two-body final states is difficult to probe with current experiments because the dominant annihilation channel is velocity or helicity suppressed. The inclusion of gauge boson radiation for three-body final states can lift the helicity suppression, allowing a velocity-independent cross section to dominate the annihilation process, and providing an avenue to constrain these models. Here we examine experimental constraints on dark matter that annihilates to two leptons plus a bremsstrahlung boson, $\bar{\ell}+\ell+γ/W/Z$. We consider experimental constraints on photon final states from Fermi-LAT using both diffuse photon data and data from dwarf spheroidal galaxies, and compare to the implied constraints from 21 cm measurements. Diffuse photon line searches are generally the strongest over the entire mass regime. We in particular highlight the model in which dark matter annihilates to two neutrinos and a photon, and show that these models are more strongly constrained through photon measurements than through existing neutrino bounds.

hep-ph↗

arXiv2018

Coherent Elastic Neutrino Nucleus Scattering (CE$ν$NS) as a probe of $Z'$ through kinetic and mass mixing effects

We examine the current constraints and future sensitivity of Coherent Elastic Neutrino-Nucleus Scattering (CE$ν$NS) experiments to mixing scenarios involving a $Z^\prime$ which interacts via portals with the Standard Model. We contrast the results against those from fixed target, atomic parity violation, and solar neutrino experiments. We demonstrate a significant dependence of the experimental reach on the $Z'$ coupling non-universality and the complementarity of CE$ν$NS to existing searches.

hep-ph↗

arXiv2018

Non-thermal Production of Dark Matter from Primordial Black Holes

We present a scenario for non-thermal production of dark matter from evaporation of primordial black holes. A period of very early matter domination leads to formation of black holes with a maximum mass of $\simeq 2 \times 10^8$ g, whose subsequent evaporation prior to big bang nucleosynthesis can produce all of the dark matter in the universe. We show that the correct relic abundance can be obtained in this way for thermally underproduced dark matter in the 100 GeV-10 TeV mass range. To achieve this, the scalar power spectrum at small scales relevant for black hole formation should be enhanced by a factor of ${\cal O}(10^5)$ relative to the scales accessible by the cosmic microwave background experiments.

astro-ph.CO↗

arXiv2017

Accelerator and reactor complementarity in coherent neutrino scattering

We study the complementarity between accelerator and reactor coherent elastic neutrino-nucleus elastic scattering (CE$ν$NS) experiments for constraining new physics in the form of non-standard neutrino interactions (NSI). Firstly, considering just data from the recent observation by the COHERENT experiment, we explore interpretive degeneracies that emerge when activating either two or four unknown NSI parameters. Next, we demonstrate that simultaneous treatment of reactor and accelerator experiments, each employing at least two distinct target materials, can break a degeneracy between up and down flavor-diagonal NSI terms that survives analysis of neutrino oscillation experiments. Considering four flavor-diagonal ($ee/μμ$) up and down-type NSI parameters, we find that all terms can be measured with high local precision (to a width as small as $\sim$5\% in Fermi units) by next-generation experiments, although discrete reflection ambiguities persist.

hep-ph↗

arXiv2017

Enhancing Dark Matter Annihilation Rates with Dark Bremsstrahlung

Many dark matter interaction types lead to annihilation processes which suffer from p-wave suppression or helicity suppression, rendering them subdominant to unsuppressed s-wave processes. We demonstrate that the natural inclusion of dark initial state radiation can open an unsuppressed s-wave annihilation channel, and thus provide the dominant dark matter annihilation process for particular interaction types. We illustrate this effect with the bremsstrahlung of a dark spin-0 or dark spin-1 particle from fermionic dark matter, $\overlineχχ\rightarrow \overline{f}fϕ$ or $\overline{f}fZ'$. The dark initial state radiation process, despite having a 3-body final state, proceeds at the same order in the new physics scale $Λ$ as the annihilation to the 2-body final state $\overlineχχ\rightarrow \overline{f}f$. This is lower order in $Λ$ than the well-studied lifting of helicity suppression via Standard Model final state radiation, or virtual internal bremsstrahlung. This dark bremsstrahlung process should influence LHC and indirect detection searches for dark matter.

hep-ph↗

arXiv2016

Probing light mediators at ultra-low threshold energies with coherent elastic neutrino-nucleus scattering

Light neutral mediators, with mass $\lesssim 1$ GeV, are common features of extensions to the Standard Model (SM). Current astrophysical and terrestrial experiments have constrained the model parameter space, and planned experiments around the world promise continued improvement in sensitivity. In this paper we study the prospects for probing light neutral mediators using terrestrial stopped pion and reactor sources in combination with ultra-low threshold nuclear and electron recoil detectors. We show that the coherent neutrino-nucleus and neutrino-electron scattering channels provide complementary sensitivity to light mediators. With low threshold detectors, we show that most stringent bounds on models arise from the nuclear scattering process, improving upon previous bounds from electron scattering of solar neutrinos by nearly an order of magnitude for mediator masses $\gtrsim 0.1$ GeV.

hep-ph↗

arXiv2016

Stability Aspects of Wormholes in $R^2$ Gravity

We study radial perturbations of a wormhole in $R^2$ gravity to determine regions of stability. We also investigate massive and massless particle orbits and tidal forces in this space-time for a radially infalling observer.

gr-qc↗