Finding the Strong CP problem at the LHC

We show that a class of parity based solutions to the strong CP problem predicts new colored particles with mass at the TeV scale, due to constraints from Planck suppressed operators. The new particles are copies of the Standard Model quarks and leptons. The new quarks can be produced at the LHC and are either collider stable or decay into Standard Model quarks through a Higgs, a W or a Z boson. We discuss some simple but generic predictions of the models for the LHC and find signatures not related to the traditional solutions of the hierarchy problem. We thus provide alternative motivation for new physics searches at the weak scale. We also briefly discuss the cosmological history of these models and how to obtain successful baryogenesis.Comment: 6 pages, 1 figur

Forbidden Dark Matter

Dark Matter (DM) may be a thermal relic that annihilates into heavier states in the early Universe. This Forbidden DM framework accommodates a wide range of DM masses from keV to weak scales. An exponential hierarchy between the DM mass and the weak scale follows from the exponential suppression of the thermally averaged cross section. Stringent constraints from the cosmic microwave background are evaded because annihilations turn off at late times. We provide an example where DM annihilates into dark photons, which is testable through large DM self-interactions and direct detection.Comment: 6 Pages, 3 Figures; Version published in PR

Naturalness at the LHC

Particle physics is confronted by deep questions at the weak scale and the LHC can shed light on them. In this work we propose strategies to understand from its data if electroweak symmetry breaking is natural. We describe a search performed with the CMS detector in a yet unexplored area of natural LHC parameter space and we propose measurements in the Higgs boson sector that can discriminate between natural and unnatural theorie

Marginal Deformations and Rotating Horizons

Motivated by the near-horizon geometry of four-dimensional extremal black holes, we study a disordered quantum mechanical system invariant under a global $SU(2)$ symmetry. As in the Sachdev-Ye-Kitaev model, this system exhibits an approximate $SL(2,\mathbb{R})$ symmetry at low energies, but also allows for a continuous family of $SU(2)$ breaking marginal deformations. Beyond a certain critical value for the marginal coupling, the model exhibits a quantum phase transition from the gapless phase to a gapped one and we calculate the critical exponents of this transition. We also show that charged, rotating extremal black holes exhibit a transition when the angular velocity of the horizon is tuned to a certain critical value. Where possible we draw parallels between the disordered quantum mechanics and charged, rotating black holes.Comment: 29 pages, 5 figure

A Fourth Exception in the Calculation of Relic Abundances

We propose that the dark matter abundance is set by the decoupling of inelastic scattering instead of annihilations. This coscattering mechanism is generically realized if dark matter scatters against states of comparable mass from the thermal bath. Coscattering points to dark matter that is exponentially lighter than the weak scale and has a suppressed annihilation rate, avoiding stringent constraints from indirect detection. Dark matter upscatters into states whose late decays can lead to observable distortions to the blackbody spectrum of the cosmic microwave background.Comment: 8 pages, 6 figures. V3: figure adde

Disorder and Mimesis at Hadron Colliders

We discuss how systems with a large number of degrees of freedom and disorder in their mass matrix can play a role in particle physics. We derive results on their mass spectra using, where applicable, QFT techniques. We study concrete realizations of these scenarios in the context of the LHC and HL-LHC, showing that collider events with a large number of soft b-quark jets can be common. Such final states can hide these models from current searches at the LHC. This motivates the ongoing effort aimed at lowering trigger thresholds and expanding data scouting.Comment: 34 pages, 19 figures, v2: minor changes, added reference

Constraining Axion Dark Matter with Big Bang Nucleosynthesis

We show that Big Bang Nucleosynthesis (BBN) significantly constrains axion-like dark matter. The axion acts like an oscillating QCD $\theta$ angle that redshifts in the early universe, increasing the neutron-proton mass difference at neutron freeze-out. An axion-like particle that couples too strongly to QCD results in the underproduction of 4He during BBN and is thus excluded. The BBN bound overlaps with much of the parameter space that would be covered by proposed searches for time-varying neutron EDMs. The QCD axion does not couple strongly enough to affect BBN.Comment: 5 pages, 2 figures; v2 typos corrected, numerical values for quark masses update