Brian Shuve

A facility to search for hidden particles at the CERN SPS: the SHiP physics case.

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (search for hidden particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, [Formula: see text] and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the standard model and describe interactions between new particles and four different portals-scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the standard model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation.

The Galactic Center Excess from the Bottom Up

It has recently been shown that dark-matter annihilation to bottom quarks provides a good fit to the galactic-center gamma-ray excess identified in the Fermi-LAT data. In the favored dark matter mass range m ∼ 30− 40 GeV, achieving the best-fit annihilation rate σv ∼ 5× 10−26 cm s−1 with perturbative couplings requires a sub-TeV mediator particle that interacts with both dark matter and bottom quarks. In this paper, we consider the minimal viable scenarios in which a Standard Model singlet mediates s-channel interactions only between dark matter and bottom quarks, focusing on axial-vector, vector, and pseudoscalar couplings. Using simulations that include on-shell mediator production, we show that existing sbottom searches currently offer the strongest sensitivity over a large region of the favored parameter space explaining the gamma-ray excess, particularly for axialvector interactions. The 13 TeV LHC will be even more sensitive; however, it may not be sufficient to fully cover the favored parameter space, and the pseudoscalar scenario will remain unconstrained by these searches. We also find that direct-detection constraints, induced through loops of bottom quarks, complement collider bounds to disfavor the vector-current interaction when the mediator is heavier than twice the dark matter mass. We also present some simple models that generate pseudoscalar-mediated annihilation predominantly to bottom quarks.

Multilepton and Lepton Jet Probes of Sub-Weak-Scale Right-Handed Neutrinos

We propose new searches that exploit the unique signatures of decaying sterile neutrinos with masses below

A WIMPy Baryogenesis Miracle

{M}_{W}

Baryogenesis through Neutrino Oscillations: A Unified Perspective

at the LHC, where they can be produced in rare decays of Standard Model gauge bosons. We show that, for few-GeV-scale sterile neutrinos, the LHC experiments can probe mixing angles at the level of

Probing baryogenesis with displaced vertices at the LHC

{10}^{\ensuremath{-}4}\char21{}{10}^{\ensuremath{-}3}

LHC searches for non-chiral weakly charged multiplets

through powerful searches that look for a prompt lepton in association with a displaced lepton jet. For higher-mass sterile neutrinos, i.e.,

Shedding light on neutrino masses with dark forces

{M}_{N}\ensuremath{\gtrsim}15\text{ }\text{ }\mathrm{GeV}

Looking for new charged states at the LHC: signatures of magnetic and Rayleigh dark matter

, run II can explore similarly small mixing angles in prompt multilepton final states. This represents an improvement of up to 2 orders of magnitude in sensitivity to the sterile neutrino production rate.

Discovering Inelastic Thermal-Relic Dark Matter at Colliders

A bstractWe explore models in which weakly interacting massive particle (WIMP) dark matter annihilation is directly responsible for baryogenesis, thereby connecting dark matter with baryogenesis. We call this process “WIMPy baryogenesis”. The dark matter relic density in these models, as with conventional WIMP models, is obtained with only order one couplings and TeV-scale masses according to the WIMP miracle. Thus, WIMPy baryo-genesis models naturally accommodate weak-scale dark matter. Furthermore, an extension of the WIMP miracle simultaneously explains the observed baryon asymmetry and the correct dark matter abundance. The models we present have the further feature that they create the baryon number asymmetry at the weak scale, thereby avoiding the problems in some models of baryogenesis associated with high reheat temperatures in supersymmetric theories. Some of these models yield observable consequences in ongoing and future experiments.