Search

Motivated by the recent search for a Higgs portal scalar decaying inside the MicroBooNE detector, we demonstrate that the same search can be used to constrain heavy neutral leptons. These are gauge-singlet fermions that interact with the Standard Model by mixing with neutrinos only and could be related to the origin of neutrino masses. By recasting the results of the MicroBooNE Collaboration's analysis, we show that, for a heavy neutral lepton that mixes predominantly with muon-flavored neutrinos, previously unexplored parameter space can be excluded for masses between 30 and 150 MeV. Additionally, we make our Monte Carlo tools publicly available. [ABSTRACT FROM AUTHOR]

We inspect recently updated neutrino oscillation data--specifically coming from the Tokai to Kamioka and NuMI Off-axis νe Appearance experiments--and how they are analyzed to determine whether the neutrino mass ordering is normal (m1

Simple symmetry arguments applied to the third generation lead to a prediction: there exist new sequential Higgs doublets with masses of order <5.5TeV, with approximately universal Higgs-Yukawa coupling constants, g~1. This is calibrated by the known Higgs boson mass, the top quark Higgs-Yukawa coupling, and the b-quark mass. A new massive weak-isodoublet, Hb, coupled to the b-quark with g~1 is predicted. It may be accessible at the 13 TeV LHC, and definitively at an energy upgraded 26 TeV LHC. The extension to leptons generates a new Hτ and a possible Hντ doublet. The accessibility of the latter depends upon whether the mass of the τ-neutrino is Dirac or Majorana. The new physics of the model is technically natural, and overall the model is no less natural than the Standard Model. [ABSTRACT FROM AUTHOR]

We conjecture that there exists a scalar bound state for every pair of fundamental fermions at a UV ("composite") scale, Λ ≫ v weak. This implies a large number of universally coupled, subcritical Higgs doublets. All but the standard model Higgs are "dormant," with large positive squared masses, and each receives a small vacuum expectation value via mixing with the standard model Higgs. Universal couplings, modulo renormalization group running effects, flip the flavor problem into the masses and mixings of the Higgs system. Doublets associated with heavy fermion masses, b, c, τ, likely lie in the multi-tera electron volt range but may be observable at the current LHC, or a high-luminosity and/or an energy-upgraded LHC. In the lepton sector, we are led to a Higgs seesaw for neutrino masses and corollary processes of observable flavor violation. The observation of the first sequential doublet coupled to ¯ b b with mass less than 3.5 TeV would lend credence to the hypothesis. [ABSTRACT FROM AUTHOR]

Cold, ultralight (≪eV) bosonic fields can induce fast temporal variation in neutrino couplings, thereby distorting neutrino oscillations. In this paper, we exploit this effect to introduce a novel probe of neutrino time variation and dark matter at long-baseline experiments. We study several representative observables and find that current and future experiments, including DUNE and JUNO, are sensitive to a wide range of model parameters over many decades in mass reach and time-variation periodicity. [ABSTRACT FROM AUTHOR]

We study the contributions of colorless vectorlike fermions to the triple gauge couplings W+W-γ and W+W-Z0. We consider models in which their coupling to the Standard Model Higgs boson is allowed or forbidden by quantum numbers. We assess the sensitivity of the future accelerators FCC-ee, ILC, and CLIC to the parameters of these models, assuming they will be able to constrain the anomalous triple gauge couplings with precision δκV~O(10-4), V=γ,Z0. We show that the combination of measurements at different center-of-mass energies helps to improve the sensitivity to the contribution of vectorlike fermions, in particular when they couple to the Higgs. In fact, the measurements at the FCC-ee and, especially, the ILC and the CLIC, may turn the triple gauge couplings into a new set of precision parameters able to constrain the models better than the oblique parameters or the H→γγ decay, even assuming the considerable improvement of the latter measurements achievable at the new machines. [ABSTRACT FROM AUTHOR]

Simplified dark matter models have been recently advocated as a powerful tool to exploit the complementarity between dark matter direct detection, indirect detection and LHC experimental probes. Focusing on pseudoscalar mediators between the dark and visible sectors, we show that the simplified dark matter model phenomenology departs significantly from that of consistent SU (2)L × U(1)Y gauge invariant completions. We discuss the key physics that simplified models fail to capture, and its impact on LHC searches. Notably, we show that resonant mono-Z searches provide competitive sensitivities to standard mono-jet analyses at 13 TeV LHC. [ABSTRACT FROM AUTHOR]

In December 2015, the ATLAS and CMS collaborations presented a possible signal in the diphoton channel. Although more data have shown that the signal was likely to be only a statistical fluctuation, it is interesting to ask what can be learned if any diphoton excess would show up in future data. Here we challenge the interpretation of any possible diphoton excess in a two-Higgs-doublet framework and find results that are valid whenever a large number of colored and charged vectorlike fermions are needed to boost the production cross section. In a broad region of parameter space, the one-loop effects of these fermions abruptly drive the scalar potential to instability even before the hypercharge gauge coupling becomes nonperturbative. [ABSTRACT FROM AUTHOR]

In addition to the next generation of beam-based neutrino experiments and their associated detectors, a number of intense, low-energy neutrino production sources from decays at rest will be in operation. In this work, we explore the physics opportunities with decay-at-rest neutrinos for complementary measurements of oscillation parameters at long baselines. The J-PARC Spallation Neutron Source, for example, will generate neutrinos from a variety of decay-at-rest (DAR) processes, specifically those of pions, muons, and kaons. Other proposed sources will produce large numbers of stopped pions and muons. We demonstrate the ability of the upcoming Hyper-Kamiokande experiment to detect the monochromatic kaon decay-at-rest neutrinos from J-PARC after they have traveled several hundred kilometers and undergone oscillations. This measurement will serve as a valuable cross-check in constraining our understanding of neutrino oscillations in a new regime of neutrino energy and baseline length. We also study the expected event rates from pion and muon DAR neutrinos in liquid argon and water detectors and their sensitivities to the charge-parity- (CP) violating phase dCP. [ABSTRACT FROM AUTHOR]

We explore the sensitivity of the Deep Underground Neutrino Experiment (DUNE) near detector and the proposed DUNE-PRISM movable near detector to sub-GeV dark matter, specifically scalar dark matter coupled to the standard model via a sub-GeV dark photon. We consider dark matter produced in the DUNE target that travels to the detector and scatters off electrons. By combining searches for dark matter at many off-axis positions with DUNE-PRISM, sensitivity to this scenario can be much stronger than when performing a measurement at one on-axis position. [ABSTRACT FROM AUTHOR]

We generalize the scalar triplet neutrino mass model, the type II seesaw. Our model displays compelling theoretical and experimental features. First, lepton number violation is dynamically generated, without introducing a naturalness problem, nor relying on arbitrarily small parameters. Second, we identify a smoking gun signature at the LHC that both probes the triplet structure of our seesaw mechanism and allows to disentangle it from the usual type II scenario. Additionally, we discuss other interesting phenomenological aspects of the model such as the presence of a massless Goldstone boson and deviations of standard model Higgs couplings. [ABSTRACT FROM AUTHOR]

We examine the recently reported low-energy electron recoil spectrum observed at the XENON1T underground dark matter direct detection experiment, in the context of new interactions with solar neutrinos. In particular we show that scalar and vector mediators with masses ≲50  keV coupled to leptons could already leave a visible signature in the XENON1T experiment, similar to the observed peak below 7 keV. This signals that dark matter detectors are already competing with neutrino scattering experiments such as GEMMA, CHARM-II and Borexino. If these results from XENON1T are interpreted as a new signal of such physics, the parameters which fit the excess face challenges from astrophysics which seem very difficult to overcome. If they are rather viewed as a constraint on new couplings, they herald the start of an era of novel precise probes of physics beyond the Standard Model with dark matter detectors. [ABSTRACT FROM AUTHOR]

We show that, in the presence of bulk masses, sterile neutrinos propagating in large extra dimensions (LED) can induce electron-neutrino appearance effects. This is in contrast to what happens in the standard LED scenario, and hence LED models with explicit bulk masses have the potential to address the MiniBooNE and LSND appearance results as well as the reactor and Gallium anomalies. A special feature in our scenario is that the mixing of the first Kaluza-Klein modes to active neutrinos can be suppressed, making the contribution of heavier sterile neutrinos to oscillations relatively more important. We study the implications of this neutrino mass generation mechanism for current and future neutrino oscillation experiments and show that the Short Baseline Neutrino Program at Fermilab will be able to efficiently probe such a scenario. In addition, this framework leads to massive Dirac neutrinos and thus precludes any signal in neutrinoless double beta decay experiments. [ABSTRACT FROM AUTHOR]