arXiv subjects

Ian M. Shoemaker

Publications and source records attributed to Ian M. Shoemaker.

At least 73 records · Page 4Linked to original sources

arXiv2018

Mapping The Neutrino Floor For Dark Matter-Electron Direct Detection Experiments

We study the discovery reach of future Dark Matter (DM) Direct Detection experiments using DM-electron scattering in the presence of the solar neutrino background. At these low energies traditional methods for nuclear and electronic recoil discrimination fail, implying that the neutrino-{\it nucleus} scattering background can be sizable. We calculate discovery limits based on ionization values of signal and background, and quantify the dependence on the ionization model. Moreover, we explore how the dependence of the DM cross section discovery limits vary with exposure, electronic/nuclear recoil discrimination, DM form factors, and DM astrophysical uncertainties.

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arXiv2017

Double Bangs from New Physics in IceCube

A variety of new physics models allows for neutrinos to up-scatter into heavier states. If the incident neutrino is energetic enough, the heavy neutrino may travel some distance before decaying. In this work, we consider the atmospheric neutrino flux as a source of such events. At IceCube, this would lead to a "double-bang" (DB) event topology, similar to what is predicted to occur for tau neutrinos at ultra-high energies. The DB event topology has an extremely low background rate from coincident atmospheric cascades, making this a distinctive signature of new physics. Our results indicate that IceCube should already be able to derive new competitive constraints on models with GeV-scale sterile neutrinos using existing data.

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arXiv2017

Terrestrial Effects on Dark Matter-Electron Scattering Experiments

A well-studied possibility is that dark matter may reside in a sector secluded from the Standard Model, except for the so-called photon portal: kinetic mixing between the ordinary and dark photons. Such interactions can be probed at dark matter direct detection experiments, and new experimental techniques involving detection of dark matter-electron scattering offer new sensitivity to sub-GeV dark matter. Typically however it is implicitly assumed that the dark matter is not altered as it traverses the Earth to arrive at the detector. In this paper we study in detail the effects of terrestrial stopping on dark photon models of dark matter, and find that they significantly reduce the sensitivity of XENON10 and DAMIC. In particular we find that XENON10 only excludes masses in the range (5-3000) MeV while DAMIC only probes (20-50) MeV. Their corresponding cross section sensitivity is reduced to a window of cross sections between $(5\times 10^{-38}-10^{-30})~{\rm cm}^{2}$ for XENON10 and a small window around $\sim 10^{-31}~{\rm cm}^{2}$ for DAMIC. We also examine implications for a future DAMIC run.

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arXiv2017

Solar Neutrinos as a Probe of Dark Matter-Neutrino Interactions

Sterile neutrinos at the eV scale have long been studied in the context of anomalies in short baseline neutrino experiments. Their cosmology can be made compatible with our understanding of the early Universe provided the sterile neutrino sector enjoys a nontrivial dynamics with exotic interactions, possibly providing a link to the Dark Matter (DM) puzzle. Interactions between DM and neutrinos have also been proposed to address the long-standing "missing satellites" problem in the field of large scale structure formation. Motivated by these considerations, in this paper we discuss realistic scenarios with light steriles coupled to DM. We point out that within this framework active neutrinos acquire an effective coupling to DM that manifests itself as a new matter potential in the propagation within a medium of asymmetric DM. Assuming that at least a small fraction of asymmetric DM has been captured by the Sun, we show that a sizable region of the parameter space of these scenarios can be probed by solar neutrino experiments, especially in the regime of small couplings and light mediators where all other probes become inefficient. In the latter regime these scenarios behave as familiar $3+1$ models in all channels except for solar data, where a Solar Dark MSW effect takes place. Solar Dark MSW is characterized by modifications of the most energetic $^8$B and CNO neutrinos, whereas the other fluxes remain largely unaffected.

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arXiv2017

A COHERENT Search Strategy for Beyond Standard Model Neutrino Interactions

We study the sensitivity of the stopped pion source of neutrinos at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory to neutrino non-standard interactions (NSI). In particular, we find that simple event counting above threshold can improve constraints on NSI for electron- and muon- flavored NSI, with the strongest constraints arising for flavor-diagonal NSI coupling to $μ$ neutrinos. However, if the detector resolution is sufficient to all for even a coarse spectral study of events, COHERENT will also be sensitive to the mass scale of NSI. We demonstrate that this can yield new limits on $Z'$ completions of NSI if the gauge boson mass is $\lesssim 1$ GeV.

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arXiv2016

Detecting Asymmetric Dark Matter in the Sun with Neutrinos

Dark Matter (DM) may have a relic density that is in part determined by a particle/antiparticle asymmetry, much like baryons. If this is the case, it can accumulate in stars like the Sun to sizable number densities and annihilate to Standard Model (SM) particles including neutrinos. We show that the combination of neutrino telescope and direct detection data can be used in conjunction to determine or constrain the DM asymmetry from data. Depending on the DM mass, the current neutrino data from Super-K and IceCube give powerful constraints on asymmetric DM unless its fractional asymmetry is $\lesssim 10^{-2}$. Future neutrino telescopes and detectors like Hyper-K and KM3NeT can search for the resulting signal of high-energy neutrinos from the center of the Sun. The observation of such a flux yields information on both the DM-nucleus cross section but also on the relative abundances of DM and anti-DM.

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arXiv2016

Short-baseline neutrino oscillations, Planck, and IceCube

We examine a framework with light new physics, which couples to the Standard Model only via neutrino mixing. Taking the hints from the short-baseline anomalies seriously and combining them with modern cosmological data and recent IceCube measurements, we obtain surprisingly effective constraints on the hidden force: keV $\lesssim M \lesssim0.3$ GeV for the mediator mass and $g_{h}>10^{-6}-10^{-3}$ for the coupling constant. Flavor equilibration between the hidden and active neutrinos can be delayed until temperatures of $\sim 1$ MeV, but not below $\sim 100$ keV. This scenario can be tested with next-generation Cosmic Microwave Background, IceCube, and oscillation experiments.

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arXiv2016

Lepton Flavor Violating Non-Standard Interactions via Light Mediators

Non-Standard neutral current Interactions (NSIs) of neutrinos with matter can alter the pattern of neutrino oscillation due to the coherent forward scattering of neutrinos on the medium. This effect makes long-baseline neutrino experiments such as NO$ν$A and DUNE a sensitive probe of beyond standard model (BSM) physics. We construct light mediator models that can give rise to both lepton flavor conserving as well as Lepton Flavor Violating (LFV) neutral current NSI. We outline the present phenomenological viability of these models and future prospects to test them. We predict a lower bound on Br$(H\to μτ)$ in terms of the parameters that can be measured by DUNE and NO$ν$A, and show that the hint for $H\to μτ$ in current LHC data can be accommodated in our model. A large part of the parameter space of the model is already constrained by the bounds on Br$(τ\to Z^\prime μ)$ and rare meson decays and can in principle fully tested by improving these bounds.

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arXiv2016

Asymmetric Dark Matter Models and the LHC Diphoton Excess

The existence of dark matter (DM) and the origin of the baryon asymmetry are persistent indications that the SM is incomplete. More recently, the ATLAS and CMS experiments have observed an excess of diphoton events with invariant mass of about 750 GeV. One interpretation of this excess is decays of a new spin-0 particle with a sizable diphoton partial width, e.g. induced by new heavy weakly charged particles. These are also key ingredients in models cogenerating asymmetric DM and baryons via sphaleron interactions and an initial particle asymmetry. We explore what consequences the new scalar may have for models of asymmetric DM that attempt to account for the similarity of the dark and visible matter abundances.

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arXiv2016

Probing BSM Neutrino Physics with Flavor and Spectral Distortions: Prospects for Future High-Energy Neutrino Telescopes

The flavor of cosmic neutrinos may help unveil their sources and could reveal the presence of new physics in the neutrino sector. We consider the impacts of next-generation neutrino detectors, including the planned upgrade to neutrino detector--IceCube-Gen2, which is well-positioned to make dramatic improvements in both flavor and spectral measurements. We show that various models in neutrino physics beyond the Standard Model, such as neutrino decay, pseudo-Dirac states, and neutrino self-scattering, may be found or strongly constrained at IceCube-Gen2 and KM3NeT. We find that the additional flavor discriminants given by Glashow resonance events and so-called "double-bang" topologies improve the ability to access the flavor of the cosmic high-energy neutrinos and probe the BSM physics. In addition, although the details depend on source properties, Glashow resonance events have the additional feature of being able to inform us of the relative strengths of neutrino and antineutrino emission, which may help us discriminate astrophysical scenarios.

astro-ph.HE↗

arXiv2015

Asymptotically Safe Dark Matter

We introduce a new paradigm for dark matter (DM) interactions in which the interaction strength is asymptotically safe. In models of this type, the coupling strength is small at low energies but increases at higher energies, and asymptotically approaches a finite constant value. The resulting phenomenology of this "asymptotically safe DM" is quite distinct. One interesting effect of this is to partially offset the low-energy constraints from direct detection experiments without affecting thermal freeze-out processes which occur at higher energies. High-energy collider and indirect annihilation searches are the primary ways to constrain or discover asymptotically safe dark matter.

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arXiv2015

New or $ν$ Missing Energy? Discriminating Dark Matter from Neutrino Interactions at the LHC

Missing energy signals such as monojets are a possible signature of Dark Matter (DM) at colliders. However, neutrino interactions beyond the Standard Model may also produce missing energy signals. In order to conclude that new "missing particles" are observed the hypothesis of BSM neutrino interactions must be rejected. In this paper, we first derive new limits on these Non-Standard neutrino Interactions (NSIs) from LHC monojet data. For heavy NSI mediators, these limits are much stronger than those coming from traditional low-energy $ν$ scattering or $ν$ oscillation experiments for some flavor structures. Monojet data alone can be used to infer the mass of the "missing particle" from the shape of the missing energy distribution. In particular, 13 TeV LHC data will have sensitivity to DM masses greater than $\sim$ 1 TeV. In addition to the monojet channel, NSI can be probed in multi-lepton searches which we find to yield stronger limits at heavy mediator masses. The sensitivity offered by these multi-lepton channels provide a method to reject or confirm the DM hypothesis in missing energy searches.

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arXiv2015

On the Direct Detection of Dark Matter Annihilation

We investigate the direct detection phenomenology of a class of dark matter (DM) models in which DM does not directly interact with nuclei, {but rather} the products of its annihilation do. When these annihilation products are very light compared to the DM mass, the scattering in direct detection experiments is controlled by relativistic kinematics. This results in a distinctive recoil spectrum, a non-standard and or even absent annual modulation, and the ability to probe DM masses as low as a $\sim$10 MeV. We use current LUX data to show that experimental sensitivity to thermal relic annihilation cross sections has already been reached in a class of models. Moreover, the compatibility of dark matter direct detection experiments can be compared directly in $E_{\rm min}$ space without making assumptions about DM astrophysics, mass, or scattering form factors. Lastly, when DM has direct couplings to nuclei, the limit from annihilation to relativistic particles in the Sun can be stronger than that of conventional non-relativistic direct detection by more than three orders of magnitude for masses in a 2-7 GeV window.

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arXiv2015

Daily Modulation as a Smoking Gun of Dark Matter with Significant Stopping

We point out that for a range of parameters, the flux of DM may be stopped significantly by its interactions with the Earth. This can significantly degrade the sensitivity of direct detection experiments to DM candidates with large interactions with terrestrial nuclei. We find that a significant region of parameter space remains unconstrained for DM $\lesssim $ a few GeV. For DM candidates with moderate levels of stopping power, the flux of DM may be blocked from below but not above a detector thereby producing a novel daily modulation. This can be explored by low threshold detectors placed on the surface or in shallow sites in the south hemisphere.

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arXiv2014

Self-Interacting Dark Matter through the Higgs Portal

We study self-interacting dark matter coupled to the Standard Model via the Higgs portal. We consider a scenario where dark matter is a thermal relic with strong enough self interactions that can alleviate the problems of collisionless cold dark matter. We study constraints from direct detection searches, the LHC, and Big Bang nucleosynthesis. We show that the tension between these constraints and the need for sufficiently strong self-interactions with light mediators can be alleviated by coupling the mediator to either active or sterile neutrinos. Future direct detection data offers great potential and can be used to find evidence of a light mediator and verify that dark matter scatters via long-range self-interactions.

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arXiv2014

Neutrino Portal Dark Matter: From Dwarf Galaxies to IceCube

It has been suggested that the baseline scenario of collisionless cold dark matter over-predicts the numbers of satellite galaxies, as well as the dark matter (DM) densities in galactic centers. This apparent lack of structure at small scales can be accounted for if one postulates neutrino-DM and DM-DM interactions mediated by light O(MeV) force carriers. In this letter, we consider a simple, consistent model of neutrinophilic DM with these features where DM and a "secluded" SM-singlet neutrino species are charged under a new $U(1)$ gauge symmetry. An important ingredient of this model is that the secluded sector couples to the Standard Model fields only through neutrino mixing. We observe that the secluded and active neutrinos recouple, leading to a large relic secluded neutrino population. This relic population can prevent small-scale halos from collapsing, while at same time significantly modifying the optical depth of ultra-high-energy neutrinos recently observed at Icecube. We find that the bulk of the parameter space accommodating an (a)symmetric thermal relic has potentially observable consequences for the IceCube high energy signal, with some of the parameter ranges already ruled out by the existing data. Future data may confirm this mechanism if either spectral absorption features or correlations with nearby sources are observed.

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arXiv2014

Halo Independent Direct Detection of Momentum-Dependent Dark Matter

We show that the momentum dependence of dark matter interactions with nuclei can be probed in direct detection experiments without knowledge of the dark matter velocity distribution. This is one of the few properties of DM microphysics that can be determined with direct detection alone, given a signal of dark matter in multiple direct detection experiments with different targets. Long-range interactions arising from the exchange of a light mediator are one example of momentum-dependent DM. For data produced from the exchange of a massless mediator we find for example that the mediator mass can be constrained to be $\lesssim 10$ MeV for DM in the 20-1000 GeV range in a halo-independent manner.

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arXiv2014

Annihilating Asymmetric Dark Matter

The relic abundance of particle and antiparticle dark matter (DM) need not be vastly different in thermal asymmetric dark matter (ADM) models. By considering the effect of a primordial asymmetry on the thermal Boltzmann evolution of coupled DM and anti-DM, we derive the requisite annihilation cross section. This is used in conjunction with CMB and Fermi-LAT gamma-ray data to impose a limit on the number density of anti-DM particles surviving thermal freeze-out. When the extended gamma-ray emission from the Galactic Center is reanalyzed in a thermal ADM framework, we find that annihilation into $τ$ leptons prefer anti-DM number densities 1-4$\%$ that of DM while the $b$-quark channel prefers 50-100$\%$.

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