We consider an extension of the Standard Model by three singlet fermions and one singlet real scalar field. The scalar is an ultralight dark matter candidate whose abundance is set by dynamically induced misalignment from the Higgs portal. We focus on parameter space where the Coleman-Weinberg potential both fixes the dark matter relic abundance, and predicts the mass scale of right-handed neutrinos. The model prefers scalar masses in the range of 10 μeV ≲ m  ϕ  ≲ 10 meV, and can be tested via direct searches for a light scalar (e.g. fifth force tests), or by searching for right-handed neutrinos in laboratory experiments.

United States

Clara Murgui

Ryan Plestid

Coleman-Weinberg dynamics of ultralight scalar dark matter and GeV-scale right-handed neutrinos

We propose a novel technique to search for axions with an optomechanical cavity filled with a material such as superfluid helium. Axion absorption converts a pump laser photon to a photon plus a phonon. The axion absorption rate is enhanced by the high occupation number of coherent photons or phonons in the cavity, allowing our proposal to largely overcome the extremely small axion coupling. The axion mass probed is set by the relative frequency of the photon produced in the final state and the Stokes mode. Because neither the axion mass nor momentum need to be matched to the physical size of the cavity, we can scale up the cavity size while maintaining access to a wide range of axion masses (up to a meV) complementary to other cavity proposals.

Yikun Wang

Kathryn M. Zurek

Axion detection with optomechanical cavities

We study the implications of finite naturalness in Pati-Salam models where <math><mi>SU</mi><mo>(</mo><mn>3</mn><msub><mo>)</mo><mi>C</mi></msub></math> is embedded in SU(4). For the minimal realization at low scale of quark-lepton unification, which employs the inverse seesaw for neutrino masses, we find that radiative corrections to the Higgs boson mass are at least <math><mi>δ</mi><msubsup><mi>m</mi><mi>h</mi><mn>2</mn></msubsup><mo>/</mo><msubsup><mi>m</mi><mi>h</mi><mn>2</mn></msubsup><mo>∼</mo><mi>O</mi><mo>(</mo><msup><mn>10</mn><mn>4</mn></msup><mo>)</mo></math>. The one-loop contributions to the Higgs mass are suppressed by four powers of the hypercharge gauge coupling. We find that for the vector leptoquarks the naively leading part of the two-loop corrections cancel. We assume the Dirac Yukawa couplings for neutrinos are equal to the up-type quark Yukawa couplings as predicted in the minimal theory for quark-lepton unification. Despite these findings, the two-loop corrections still dominate the finite naturalness bound. We mention a way to relax the lower bound on the vector leptoquark mass and have <math><mi>δ</mi><msubsup><mi>m</mi><mi>h</mi><mn>2</mn></msubsup><mo>/</mo><msubsup><mi>m</mi><mi>h</mi><mn>2</mn></msubsup><mo>∼</mo><mi>O</mi><mo>(</mo><msup><mn>10</mn><mn>2</mn></msup><mo>)</mo></math>.

Pavel Fileviez Pérez

Samuel Patrone

Adriano Testa

Mark B. Wise

Finite naturalness and quark-lepton unification

We discuss a simple model, based on the gauge group <math><mi>SU</mi><mo>(</mo><mn>3</mn><msub><mo>)</mo><mi>C</mi></msub><mo>⊗</mo><mi>SU</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>L</mi></msub><mo>⊗</mo><mi>U</mi><mo>(</mo><mn>1</mn><msub><mo>)</mo><mi>Y</mi></msub><mo>⊗</mo><mi>U</mi><mo>(</mo><mn>1</mn><msub><mo>)</mo><mi>R</mi></msub></math>, where the Nelson-Barr solution to the strong <math><mrow><mi>C</mi><mi>P</mi></mrow></math> problem is implemented. This model automatically provides a high quality solution to the strong <math><mrow><mi>C</mi><mi>P</mi></mrow></math> puzzle. Weak <math><mrow><mi>C</mi><mi>P</mi></mrow></math> violation in the lepton sector arises in the same fashion as in the quark sector. We derive explicit expressions for the flavor changing couplings of the electroweak and Higgs bosons. These expressions are more general than the particular model considered. Constraints from finite naturalness are briefly discussed. We also briefly discuss related models based on the gauge group B-L.

Automatic Nelson-Barr solutions to the strong <math><mi>C</mi><mi>P</mi></math> puzzle

Direct detection experiments for dark matter are increasingly ruling out large parameter spaces. However, light dark matter models with particle masses <math><mrow><mo>&lt;</mo><mi>GeV</mi></mrow></math> are still largely unconstrained. Here we examine a proposal to use atom interferometers to detect a light dark matter subcomponent at sub-GeV masses. We describe the decoherence and phase shifts caused by dark matter scattering off of one “arm” of an atom interferometer using a generalized dark matter direct detection framework. This allows us to consider multiple channels: nuclear recoils, hidden photon processes, and axion interactions. We apply this framework to several proposed atom interferometer experiments. Because atom interferometers are sensitive to extremely low momentum deposition and their coherent atoms give them a boost in sensitivity, these experiments will be highly competitive and complementary to other direct detection methods. In particular, atom interferometers are uniquely able to probe a dark matter subcomponent with <math><msub><mi>m</mi><mi>χ</mi></msub><mo>≲</mo><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>keV</mi></math>. We find that, for a mediator mass <math><msub><mi>m</mi><mi>ϕ</mi></msub><mo>=</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup><msub><mi>m</mi><mi>χ</mi></msub></math>, future atom interferometers could close a gap in the existing constraints on nuclear recoils down to <math><mrow><msub><mrow><mover><mrow><mi>σ</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mi>n</mi></mrow></msub><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>50</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>cm</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math> for <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>χ</mi></mrow></msub><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math> dark matter masses.

Yufeng Du

Kris Pardo

Atom interferometer tests of dark matter

We show that one can explain the neutral and charged anomalies in <math><mi>B</mi></math>-meson decays in the minimal theory for quark-lepton unification. The implications for flavor violating processes are discussed in detail. Strikingly, experimental observations suggest that the unification of quarks and leptons could be realized at the <math><mi>O</mi><mo>(</mo><msup><mn>10</mn><mn>2</mn></msup><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> scale.

Flavor anomalies and quark-lepton unification

Motivated by the observed ratio of dark matter to baryon mass densities, <math><msub><mi>ρ</mi><mi>D</mi></msub><mo>/</mo><msub><mi>ρ</mi><mi>B</mi></msub><mo>≃</mo><mn>5</mn></math>, we propose a theory of dark-color unification. In this theory, the dark to visible baryon masses are fixed by the ratio of dark to visible confinement scales, which are determined to be nearby in mass through the unification of the dark and visible gauge theories at a high scale. Together with a mechanism for dark baryogenesis, which arises naturally from the grand unification sector, the mass densities of the two sectors must be nearby, explaining the observed mass density of dark matter. We focus on the simplest possible example of such a theory, where the Standard Model color <math><mi>SU</mi><mo>(</mo><mn>3</mn><msub><mo>)</mo><mi>C</mi></msub></math> is unified with the dark color <math><mi>SU</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>D</mi></msub></math> into SU(5) at an intermediate scale of around <math><msup><mn>10</mn><mn>8</mn></msup><mo>–</mo><msup><mn>10</mn><mn>9</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. The dark baryon consists of two dark quarks in an isotriplet configuration. There are a range of important cosmological, astrophysical, and collider signatures to explore, including dark matter self-interactions, early matter domination from the dark hadrons, gravitational wave signatures from the hidden sector phase transition, contributions to flavor observables, as well as Hidden-Valley-like signatures at colliders.

Dark unification: A UV-complete theory of asymmetric dark matter

In order to address the baryon asymmetry in the Universe one needs to understand the origin of baryon and lepton number violation. In this article, we discuss the mechanism of baryogenesis via leptogenesis to explain the matter-antimatter asymmetry in theories with spontaneous breaking of baryon and lepton number. In this context, a lepton asymmetry is generated through the out-of-equilibrium decays of right-handed neutrinos at the high-scale, while local baryon number must be broken below the multi-TeV scale to satisfy the cosmological bounds on the dark matter relic density. We demonstrate how the lepton asymmetry generated via leptogenesis can be converted in two different ways: (a) in the theory predicting Majorana dark matter the lepton asymmetry is converted into a baryon asymmetry, and (b) in the theory with Dirac dark matter the decays of right-handed neutrinos can generate lepton and dark matter asymmetries that are then partially converted into a baryon asymmetry. Consequently, we show how to explain the matter-antimatter asymmetry, the dark matter relic density and neutrino masses in theories for local baryon and lepton number.

Alexis D. Plascencia

Baryogenesis via leptogenesis: Spontaneous <math><mi>B</mi></math> and <math><mi>L</mi></math> violation

We discuss the minimal theory for quark-lepton unification at the low scale. In this context, the quarks and leptons are unified in the same representations and neutrino masses are generated through the inverse seesaw mechanism. The properties of the leptoquarks predicted in this theory are discussed in detail, and we investigate the predictions for the leptonic and semileptonic decays of mesons. We study the possibility to explain the current value of <math><msub><mi>R</mi><mi>K</mi></msub></math> reported by the LHCb Collaboration and the value of the muon anomalous magnetic moment reported by the Muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> experiment at Fermilab.

Leptoquarks and matter unification: Flavor anomalies and the muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math>

One or more scalar leptoquarks with masses around a few TeV may provide a solution to some of the flavor anomalies that have been observed. We discuss the impact of such new degrees on baryon number violation when the theory is embedded in a Pati-Salam model. The Pati-Salam embedding can suppress renormalizable and dimension-five baryon number violation in some cases. Our work extends the results of Assad, Grinstein, and Fornal who considered the same issue for vector leptoquarks.