Ian M. Shoemaker - Los Alamos

Ian M. Shoemaker
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Ian M. Shoemaker
Los Alamos
Los Alamos
United States

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Pub Categories

High Energy Physics - Phenomenology (35)
Cosmology and Nongalactic Astrophysics (17)
High Energy Physics - Experiment (11)
High Energy Astrophysical Phenomena (5)
High Energy Physics - Theory (2)
Nuclear Experiment (2)
Astrophysics of Galaxies (2)
Solar and Stellar Astrophysics (2)
General Relativity and Quantum Cosmology (1)
Nuclear Theory (1)

Publications Authored By Ian M. Shoemaker

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 $\mu$ 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. Read More

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. Read More

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. Read More

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. Read More

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. Read More

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. Read More

Recently, the direct detection of gravitational waves from black hole (BH) mergers was announced by the Advanced LIGO Collaboration. Multi-messenger counterparts of stellar-mass BH mergers are of interest, and it had been suggested that a small disk or celestial body may be involved in the binary of two BHs. To test such possibilities, we consider the fate of a wind powered by an active mini-disk in a relatively short, super-Eddington accretion episode onto a BH with ~10-100 solar masses. Read More

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$\nu$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. Read More

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. Read More

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. Read More

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. Read More

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. Read More

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. Read More

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. Read More

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. Read More

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. Read More

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. Read More

We consider three classes of dark matter (DM) models to account for the recently observed 3.5 keV line: metastable excited state DM, annihilating DM, and decaying DM. We study two examples of metastable excited state DM. Read More

We study dark matter that inelastically scatters and de-excites in direct detection experiments, as an interpretation of the CDMS-Si events in light of the recent LUX data. The constraints from LUX and XENON10 require the mass-splitting between the DM excited and de-excited states to be $|\delta| \gtrsim 50$ keV. At the same time, the CDMS-Si data itself do not allow for a consistent DM interpretation for mass splittings larger than $|\delta| \sim $200 keV. Read More

We study phenomenological constraints in a simple $S\bar{E} \chi$y extension of the Standard Model (SM) with a 125 GeV Higgs, a vector-like heavy electron $(E)$, a complex scalar electron $(S)$ and a standard model singlet Dirac fermion $(\chi)$. The interactions among the dark matter candidate $\chi$ and the standard model particles occur via loop-induced processes involving the Yukawa interaction $S\bar{E} \chi$y. The model is an explicit perturbative realization of so-called magnetic dark matter. Read More

Isospin-violating dark matter (IVDM) has been proposed as a viable scenario to reconcile conflicting positive and null results from direct detection dark matter experiments. We show that the lowest-order dark matter-nucleus scattering rate can receive large and nucleus-dependent corrections at next-to-leading order (NLO) in the chiral expansion. The size of these corrections depends on the specific couplings of dark matter to quark flavors and gluons. Read More

The mass of primordial dark matter (DM) protohalos remains unknown. However, the missing satellites problem may be an indication that they are quite large. In this paper, we use effective field theory to map constraints on dark matter-SM interactions into limits on the mass of DM protohalos. Read More

We study the capabilities of the MAJORANA DEMONSTRATOR, a neutrinoless double-beta decay experiment currently under construction at the Sanford Underground Laboratory, as a light WIMP detector. For a cross section near the current experimental bound, the MAJORANA DEMONSTRATOR should collect hundreds or even thousands of recoil events. This opens up the possibility of simultaneously determining the physical properties of the dark matter and its local velocity distribution, directly from the data. Read More

We examine the prospects of probing nonstandard interactions (NSI) of neutrinos in the e-tau sector with upcoming long-baseline nu_mu -> nu_e oscillation experiments. First conjectured decades ago, neutrino NSI remain of great interest, especially in light of the recent 8B solar neutrino measurements by SNO, Super-Kamiokande, and Borexino. We observe that the recent discovery of large theta_13 implies that long-baseline experiments have considerable NSI sensitivity, thanks to the interference of the standard and new physics conversion amplitudes. Read More

If dark matter interacts with quarks or gluons, the mediator of these interactions is either directly accessible at the LHC or is so heavy that its effects are encoded in contact operators. We find that the self-consistency of a contact operator description at the LHC implies bounds on the mediator scale stronger than those found from missing energy searches. This translates into spin-independent elastic scattering cross-sections at a level < 10^-41 cm^2, with direct implications for the DAMA, CoGeNT, and CRESST-II anomalies. Read More

Monojet events at colliders have been used to probe models of dark matter and extra dimensions. We point out that these events also probe extensions of the Standard Model modifying neutrino-quark interactions. Such nonstandard interactions (NSI) have been discussed in connection with neutrino oscillation experiments. Read More

We suggest the existence of a fundamental connection between baryonic and dark matter. This is motivated by both the stability of these two types of matter as well as the observed similarity of their present-day densities. A unified genesis of baryonic and dark matter is natural in models in which the baryon number is promoted to a spontaneously broken local gauge symmetry. Read More

The similarity of the visible and dark matter abundances indicates that they may originate via the same mechanism. If both the dark and the visible matter are charged under a generalized baryon number which remains always conserved, then the asymmetry of the visible sector may be compensated by an asymmetry in the dark sector. We show how the separation of baryonic and antibaryonic charge can originate in the vacuum, via the Affleck-Dine mechanism, due to the breaking of a symmetry orthogonal to the baryon number. Read More

In existing dark matter models with global symmetries the relic abundance of dark matter is either equal to that of anti-dark matter (thermal WIMP), or vastly larger, with essentially no remaining anti-dark matter (asymmetric dark matter). By exploring the consequences of a primordial asymmetry on the coupled dark matter and anti-dark matter Boltzmann equations we find large regions of parameter space that interpolate between these two extremes. Interestingly, this new asymmetric WIMP framework can accommodate a wide range of dark matter masses and annihilation cross sections. Read More

Although inflationary models generically predict a flat spectrum of gravitational waves, we point out a general process that produces a sharply peaked spectrum of gravitational radiation. This process is generic for inflationary models with a complex inflaton field which couples to fermions. In particular, for chaotic models these may be the most extreme gravitational waves in the Universe with a very large energy density fraction 10^-9 and ultra-high frequency, 10^10 Hz. Read More

Sterile neutrinos have been invoked to explain the observed neutrino masses, but they can also have significant implications for cosmology and accelerator experiments. We explore the collider signatures of a simple extension of the Standard Model, where sterile neutrinos acquire their mass after electroweak symmetry breaking, via their coupling to a real singlet Higgs. In this model, heavy sterile neutrinos can be produced in accelerators from decays of the Higgs bosons. Read More

Affleck-Dine baryogenesis, accompanied by the formation and subsequent decay of Q-balls, can generate both the baryon asymmetry of the universe and dark matter in the form of gravitinos. The gravitinos from Q-ball decay dominate over the thermally produced population if the reheat temperature is less than 10^7 GeV. We show that a gravitino with mass around 1 GeV is consistent with all observational bounds and can explain the baryon-to-dark-matter ratio in the gauge-mediated models of supersymmetry breaking for a wide range of cosmological and Q-ball parameters. Read More

The gauge-mediated model of supersymmetry breaking implies that stable non-topological solitons, Q-balls, could form in the early universe and comprise the dark matter. It is shown that the inclusion of the effects from gravity-mediation set an upper limit on the size of Q-balls. When in a dense baryonic environment Q-balls grow until reaching this limiting size at which point they fragment into two equal-sized Q-balls. Read More

Gauge-mediated models of supersymmetry-breaking imply that stable Q-balls can form in the early universe and act as dark matter. All stable Q-balls in the MSSM are associated with one or more flat directions. We show that while Q-balls are produced from the fragmentation of a flat direction condensate, they quickly evolve to a ground state that is slightly away from this flat direction. Read More

Supersymmetry implies that stable non-topological solitons, Q-balls, could form in the early universe and could make up all or part of dark matter. We show that the relic Q-balls passing through Earth can produce a detectable neutrino flux. The peculiar zenith angle dependence and a small annual modulation of this flux can be used as signatures of dark-matter Q-balls. Read More

In supersymmetric generalizations of the Standard Model, all stable Q-balls are associated with some flat directions. We show that, if the flat direction has both the baryon number and the lepton number, the scalar field inside the Q-ball can deviate slightly from the flat direction in the ground state. We identify the true ground states of such nontopological solitons, including the electrically neutral and electrically charged Q-balls. Read More