arXiv subjects

Ryan Plestid

Publications and source records attributed to Ryan Plestid.

At least 37 records · Page 2Linked to original sources

arXiv2024

Long-lived vectors from electromagnetic cascades at SHiP

We simulate dark-vector, $V$, production from electromagnetic cascades at the recently approved SHiP experiment. The cascades (initiated by photons from $π^0\rightarrow γγ$) can lead to 3-4 orders of magnitude increase of the event rate relative to using primary production alone. We provide new SHiP sensitivity projections for dark photons and electrophilic gauge bosons, which are significantly improved compared to previous literature. The main gain in sensitivity occurs for long-lived dark vectors with masses below $\sim 50-300~{\rm MeV}$. The dominant production mode in this parameter space is low-energy annihilation $e^+ e^- \rightarrow V(γ)$. This motivates a detailed study of backgrounds and efficiencies in the SHiP experiment for sub-GeV signals.

hep-ph↗

arXiv2024

Coleman-Weinberg dynamics of ultralight scalar dark matter and GeV-scale right-handed neutrinos

We consider an extension of the Standard Model by three singlet fermions and one singlet real scalar field. The scalar is an ultralight dark matter candidate whose abundance is set by dynamically induced misalignment from the Higgs portal. We focus on parameter space where the Coleman-Weinberg potential both fixes the dark matter relic abundance, and predicts the mass scale of right-handed neutrinos. The model prefers scalar masses in the range of $10 ~{\rm μeV} \lesssim m_ϕ \lesssim 10 ~{\rm meV}$, and can be tested via direct searches for a light scalar (e.g. fifth force tests), or by searching for right-handed neutrinos in laboratory experiments.

hep-ph↗

arXiv2024

Atomic binding corrections for high energy fixed target experiments

High energy beams incident on a fixed target may scatter against atomic electrons. To a first approximation, one can treat these electrons as at rest. For precision experiments, however, it is important to be able to estimate the size of, and when necessary calculate, sub-leading corrections. We discuss atomic binding corrections to relativistic lepton-electron scattering. We analyze hydrogen in detail, before generalizing our analysis to multi-electron atoms. Using the virial theorem, and many-body sum rules, we find that the corrections can be reduced to measured binding energies, and the expectation value of a single one-body operator. We comment on the phenomenological impact for neutrino flux normalization and an extraction of hadronic vacuum polarization from elastic muon electron scattering at MUonE.

hep-ph↗

arXiv2024

Coherent collisional decoherence

We study the decoherence of a system of $N$ non-interacting heavy particles (atoms) due to coherent scattering with a background gas. We introduce a framework for computing the induced phase shift and loss of contrast for arbitrary preparations of $N$-particle quantum states. We find phase shifts that are inherently $(N\geq 2)$-body effects and may be searched for in future experiments. We analyze simple setups, including a two-mode approximation of an interferometer. We study fully entangled $N00N$ states, which resemble the correlated positions in a matter interferometer, as well as totally uncorrelated product states that are representative of a typical state in an atom interferometer. We find that the extent to which coherent enhancements increase the rate of decoherence depends on the observable of interest, state preparation, and details of the experimental design. In the context of future ultralow-recoil (e.g., light dark matter) searches with atom interferometers we conclude that: {\it i}) there exists a coherently enhanced scattering phase which can be searched for using standard (i.e., contrast/visibility and phase) interferometer observables; {\it ii}) although decoherence rates of one-body observables are {\it not} coherently enhanced, a coherently enhanced loss of contrast can still arise from dephasing; and {\it iii}) higher statistical moments (which are immediately accessible in a counting experiment) {\it are} coherently enhanced and may offer a new tool with which to probe the soft scattering of otherwise undetectable particles in the laboratory.

quant-ph↗

arXiv2024

Generalized eikonal identities for charged currents

We discuss QED radiative corrections to contact operators coupling two heavy fields and one light field. New eikonal identities are derived in the static limit that demonstrate the equivalence of a class of ladder graphs to an equivalent theory with a single heavy-light vertex and a background Coulomb field which communicates exclusively with the light field. We apply these new identities to nuclear beta decays and demonstrates that the "independent particle model" used by Jaus, Rasche, Sirlin \& Zucchini is closely related, though not identical, to a model independent EFT calculation.

hep-ph↗

arXiv2024

Neutrino Portals, Terrestrial Upscattering, and Atmospheric Neutrinos

We consider the upscattering of atmospheric neutrinos in the interior of the Earth producing heavy neutral leptons (HNLs) which subsequently decay inside large volume detectors (e.g. Super-Kamiokande or DUNE). We compute the flux of upscattered HNLs arriving at a detector, and the resultant event rate of visible decay products. Using Super-Kamiokande's atmospheric neutrino dataset we find new leading constraints for dipole couplings to any flavor with HNL masses between roughly 10 MeV and 100 MeV. For mass mixing with tau neutrinos, we probe new parameter space near HNL masses of $\sim 20$ MeV with prospects for substantial future improvements. We also discuss prospects at future experiments such as DUNE, JUNO, and Hyper-Kamiokande.

hep-ph↗

arXiv2024

Searching for new physics at $μ\rightarrow e$ facilities with $μ^+$ and $π^+$ decays at rest

We investigate the ability of $μ\rightarrow e$ facilities, Mu2e and COMET, to probe, or discover, new physics with their detector validation datasets. The validation of the detector response may be performed using a dedicated run with $μ^+$, collecting data below the Michel edge, $E_e\lesssim 52$ MeV; an alternative strategy using $π^+\rightarrow e^+ ν_e$ may also be considered. We focus primarily on a search for a monoenergetic $e^+$ produced via two-body decays $μ^+ \rightarrow e^+ X$ or $π^+\rightarrow e^+X$, with $X$ a light new physics particle. Mu2e can potentially explore new parameter space beyond present astrophysical and laboratory constraints for a set of well motivated models including: axion like particles with flavor violating couplings ($μ^+ \rightarrow e^+ a$), massive $Z'$ bosons ($μ^+ \rightarrow Z' e^+$), and heavy neutral leptons ($π^+\rightarrow e^+N$). The projected sensitivities presented herein can be achieved in a matter of days.

hep-ph↗

arXiv2024

All orders factorization and the Coulomb problem

In the limit of large nuclear charge, $Z\gg 1$, or small lepton velocity, $β\ll 1$, Coulomb corrections to nuclear beta decay and related processes are enhanced as $Zα/β$ and become large or even non-perturbative (with $α$ the QED fine structure constant). We provide a constructive demonstration of factorization to all orders in perturbation theory for these processes and compute the all-orders hard and soft functions appearing in the factorization formula. We clarify the relationship between effective field theory amplitudes and historical treatments of beta decay in terms of a Fermi function.

hep-ph↗

arXiv2024

Renormalization of beta decay at three loops and beyond

The anomalous dimension for heavy-heavy-light effective theory operators describing nuclear beta decay is computed through three-loop order in the static limit. The result at order $Z^2α^3$ corrects a previous result in the literature. An all-orders symmetry is shown to relate the anomalous dimensions at leading and subleading powers of $Z$ at a given order of $α$. The first unknown coefficient for the anomalous dimension now appears at $O(Z^2α^4)$.

hep-ph↗

arXiv2024

Searching for axions with kaon decay at rest

We describe a novel search strategy for axions (or hadronically coupled axion-like particles) in the mass range of $m_a \lesssim 350\,{\rm MeV}$. The search relies on kaon decay at rest, which produces a mono-energetic signal in a large volume detector (e.g.\ a tank of liquid scintillator) from axion decays $a\rightarrow γγ$ or $a\rightarrow e^+e^-$. The decay modes $K^+\to π^+ a$ and $a \to γγ$ are induced by the axion's coupling to gluons, which is generic to any model which addresses the strong CP problem. We recast a recent search from MicroBooNE for $e^+e^-$ pairs, and study prospects at JSNS$^2$ and other near-term facilities. We find that JSNS$^2$ will have world-leading sensitivity to hadronically coupled axions in the mass range of $40\,\mathrm{MeV} \lesssim m_a \lesssim 350\,\mathrm{MeV}$.

hep-ph↗

arXiv2024

Field Theory of the Fermi Function

The Fermi function $F(Z,E)$ accounts for QED corrections to beta decays that are enhanced at either small electron velocity $β$ or large nuclear charge $Z$. For precision applications, the Fermi function must be combined with other radiative corrections and with scale- and scheme-dependent hadronic matrix elements. We formulate the Fermi function as a field theory object and present a new factorization formula for QED radiative corrections to beta decays. We provide new results for the anomalous dimension of the corresponding effective operator complete through three loops, and resum perturbative logarithms and $π$-enhancements with renormalization group methods. Our results are important for tests of fundamental physics with precision beta decay and related processes.

hep-ph↗

arXiv2024

Long-Lived Particles and the Quiet Sun

The nuclear reaction network within the interior of the Sun is an efficient MeV physics factory, and can produce long-lived particles generic to dark sector models. In this work we consider the sensitivity of satellite instruments, primarily the RHESSI Spectrometer, that observe the Quiet Sun in the MeV regime where backgrounds are low. We find that Quiet Sun observations offer a powerful and complementary probe in regions of parameter space where the long-lived particle decay length is longer than the radius of the Sun, and shorter than the distance between the Sun and Earth. We comment on connections to recent model-building work on heavy neutral leptons coupled to neutrinos and high-quality axions from mirror symmetries.

hep-ph↗

arXiv2024

Final state interactions for high energy scattering off atomic electrons

We consider the scattering of high energy leptons off bound atomic electrons focusing primarily on final state interactions i.e., the exchange of virtual photons between the outgoing energetic electron, and the heavy residual charged "debris" in the final state. These effects are inherently absent from calculations for a free electron at rest. Coulomb exchanges are enhanced by the large number of electrons in the atomic debris, and are unsuppressed by non-relativistic velocities in the debris. We find that these exchanges can be resummed using operator methods, and cancel at the level of the cross section until at least $O(α^3)$. Furthermore, we argue that both final {\it and} initial state Coulomb exchanges (enhanced by the number of electrons in the atom) do not affect the cross section until at least $O(α^3)$. Transverse photon couplings to non relativistic electrons are proportional to their small velocities, and rotational invariance suppresses their contribution to $O(α^3)$. Our results are relevant for precision experiments involving neutrinos, electrons, positrons, and muons scattering off of atomic electrons in a fixed target.

hep-ph↗

arXiv2024

The effective field theory of extended Wilson lines

We construct the effective theory of electrically charged, spatially extended, infinitely heavy objects at leading power. The theory may be viewed as a generalization of NRQED for particles with a finite charge distribution where the charge radius and higher moments of the charge distribution are counted as $O(1)$ rather than $O(1/M)$. We show this is equivalent to a Wilson line traced by the worldline of an extended charge distribution. Our canonical use case is atomic nuclei with large charge $Z\gg 1$. The theory allows for the insertion of external operators and is sufficiently general to allow a treatment of both electromagnetic and weak mediated lepton-nucleus scattering including charged-current processes. This provides a first step towards the factorization of Coulomb regions, including structure dependence arising from a finite charge distribution, for scattering with nuclei.

hep-ph↗

arXiv2024

ACE Science Workshop Report

We summarize the Fermilab Accelerator Complex Evolution (ACE) Science Workshop, held on June 14-15, 2023. The workshop presented the strategy for the ACE program in two phases: ACE Main Injector Ramp and Target (MIRT) upgrade and ACE Booster Replacement (BR) upgrade. Four plenary sessions covered the primary experimental physics thrusts: Muon Collider, Neutrinos, Charged Lepton Flavor Violation, and Dark Sectors. Additional physics and technology ideas were presented from the community that could expand or augment the ACE science program. Given the physics framing, a parallel session at the workshop was dedicated to discussing priorities for accelerator R\&D. Finally, physics discussion sessions concluded the workshop where experts from the different experimental physics thrusts were brought together to begin understanding the synergies between the different physics drivers and technologies. In December of 2023, the P5 report was released setting the physics priorities for the field in the next decade and beyond, and identified ACE as an important component of the future US accelerator-based program. Given the presentations and discussions at the ACE Science Workshop and the findings of the P5 report, we lay out the topics for study to determine the physics priorities and design goals of the Fermilab ACE project in the near-term.

hep-ex↗

arXiv2024

Dark fluxes from electromagnetic cascades

We study dark sector production in electromagnetic (EM) cascades. This problem requires accurate simulations of Standard Model (SM) and dark sector processes, both of which impact angular and energy distributions of emitted particles that ultimately determine flux predictions in a downstream detector. We describe the minimal set of QED processes which must be included to faithfully reproduce a SM cascade, and identify a universal algorithm to generate a dark sector flux given a Monte-Carlo simulation of a SM shower. We provide a new tool, $\texttt{PETITE}$, which simulates EM cascades with associated dark vector production, and compare it against existing literature and "off the shelf" tools. The signal predictions at downstream detectors can strongly depend on the nontrivial interplay (and modelling) of SM and dark sector processes, in particular multiple Coulomb scattering and positron annihilation. We comment on potential impacts of these effects for realistic experimental setups.

hep-ph↗

arXiv2023

A New Probe of Relic Neutrino Clustering using Cosmogenic Neutrinos

We propose a new probe of cosmic relic neutrinos (C$ν$B) using their resonant scattering against cosmogenic neutrinos. Depending on the lightest neutrino mass and the energy spectrum of the cosmogenic neutrino flux, a Standard Model vector meson (such as a hadronic $ρ$) resonance can be produced via $ν\barν$ annihilation. This leads to a distinct absorption feature in the cosmogenic neutrino flux at an energy solely determined by the meson mass and the neutrino mass, apart from redshift. By numerical coincidence, the position of the $ρ$-resonance overlaps with the originally predicted peak of the Greisen-Zatsepin-Kuzmin (GZK) neutrino flux, which offers an enhanced absorption effect at higher redshifts. We show that this absorption feature in the GZK neutrino flux may be observable in future radio-based neutrino observatories, such as IceCube-Gen2 radio, provided there exists a large overdensity in the C$ν$B distribution. This therefore provides a new probe of C$ν$B clustering at large redshifts, complementary to the laboratory probes (such as KATRIN) at zero redshift.

hep-ph↗

arXiv2023

SENSEI: Search for Millicharged Particles produced in the NuMI Beam

Millicharged particles appear in several extensions of the Standard Model, but have not yet been detected. These hypothetical particles could be produced by an intense proton beam striking a fixed target. We use data collected in 2020 by the SENSEI experiment in the MINOS cavern at the Fermi National Accelerator Laboratory to search for ultra-relativistic millicharged particles produced in collisions of protons in the NuMI beam with a fixed graphite target. The absence of any ionization events with 3 to 6 electrons in the SENSEI data allow us to place world-leading constraints on millicharged particles for masses between 30 MeV to 380 MeV. This work also demonstrates the potential of utilizing low-threshold detectors to investigate new particles in beam-dump experiments, and motivates a future experiment designed specifically for this purpose.

hep-ex↗