arXiv subjects

Brian Shuve

Publications and source records attributed to Brian Shuve.

42 records · Page 3Linked to original sources

arXiv2014

Baryogenesis through Neutrino Oscillations: A Unified Perspective

Baryogenesis through neutrino oscillations is an elegant mechanism which has found several realizations in the literature corresponding to different parts of the model parameter space. Its appeal stems from its minimality and dependence only on physics below the weak scale. In this work we show that, by focusing on the physical time scales of leptogenesis instead of the model parameters, a more comprehensive picture emerges. The different regimes previously identified can be understood as different relative orderings of these time scales. This approach also shows that all regimes require a coincidence of time scales and this in turn translates to a certain tuning of the parameters, whether in mass terms or Yukawa couplings. Indeed, we show that the amount of tuning involved in the minimal model is never less than one part in 10^5. Finally, we explore an extended model where the tuning can be removed in exchange for the introduction of a new degree of freedom in the form of a leptophilic Higgs with a vacuum expectation value of the order of GeV.

hep-ph↗

arXiv2013

Boosted Multijet Resonances and New Color-Flow Variables

We use modern jet-substructure techniques to propose LHC searches for multijet-resonance signals without leptons or missing energy. We focus on three-jet resonances produced by R-parity-violating decays of boosted gluinos, showing that shape analyses searching for a mass peak can probe such gluinos up to masses of ~ 750 GeV (650 GeV) with 20/fb (5/fb) at the LHC at 8 TeV. This complements existing search strategies, which also include counting methods that are inherently more prone to systematic uncertainties. Since R-parity-violating gluinos lighter than all squarks hadronize before decaying, we introduce new color-flow variables, "radial pull" and "axis contraction", which are sensitive to the color structure of the R-hadron's decay. The former measures the inward pull of subjets in a fat jet, while the latter quantifies the inward drift of the $N$-subjettiness axes when changing the distance measure. We show that they can dramatically improve the discrimination of a boosted gluino signal versus QCD, ttbar and combinatoric background for m_gluino ~ m_top. Cuts on axis contraction also noticeably improve the resonance shape for heavy gluinos with m_gluino > ~500 GeV. With minor adaptations, these variables could find application in substructure searches for particles in different color representations or with other decay topologies. We also compare how several different Monte Carlo generators model the high-multiplicity QCD background. This provides evidence that the discriminating power of our color-flow observables are robust, and provides useful guidance for future substructure studies.

hep-ph↗

arXiv2012

A WIMPy Baryogenesis Miracle

We 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 baryogenesis 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.

hep-ph↗

arXiv2011

Emergent Dark Matter, Baryon, and Lepton Numbers

We present a new mechanism for transferring a pre-existing lepton or baryon asymmetry to a dark matter asymmetry that relies on mass mixing which is dynamically induced in the early universe. Such mixing can succeed with only generic scales and operators and can give rise to distinctive relationships between the asymmetries in the two sectors. The mixing eliminates the need for the type of additional higher-dimensional operators that are inherent to many current asymmetric dark matter models. We consider several implementations of this idea. In one model, mass mixing is temporarily induced during a two-stage electroweak phase transition in a two Higgs doublet model. In the other class of models, mass mixing is induced by large field vacuum expectation values at high temperatures - either moduli fields or even more generic kinetic terms. Mass mixing models of this type can readily accommodate asymmetric dark matter masses ranging from 1 GeV to 100 TeV and expand the scope of possible relationships between the dark and visible sectors in such models.

hep-ph↗

arXiv2010

Early (and Later) LHC Search Strategies for Broad Dimuon Resonances

Resonance searches generally focus on narrow states that would produce a sharp peak rising over background. Early LHC running will, however, be sensitive primarily to broad resonances. In this paper we demonstrate that statistical methods should suffice to find broad resonances and distinguish them from both background and contact interactions over a large range of previously unexplored parameter space. We furthermore introduce an angular measure we call ellipticity, which measures how forward (or backward) the muon is in eta, and allows for discrimination between models with different parity violation early in the LHC running. We contrast this with existing angular observables and demonstrate that ellipticity is superior for discrimination based on parity violation, while others are better at spin determination.

hep-ph↗

arXiv2009

LHC Searches for Non-Chiral Weakly Charged Multiplets

Because the TeV-scale to be probed at the Large Hadron Collider should shed light on the naturalness, hierarchy, and dark matter problems, most searches to date have focused on new physics signatures motivated by possible solutions to these puzzles. In this paper, we consider some candidates for new states that although not well-motivated from this standpoint are obvious possibilities that current search strategies would miss. In particular we consider vector representations of fermions in multiplets of $SU(2)_L$ with a lightest neutral state. Standard search strategies would fail to find such particles because of the expected small one-loop-level splitting between charged and neutral states.

hep-ph↗