588 research outputs found
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
symmetry. As in the Sachdev-Ye-Kitaev model, this system exhibits an
approximate symmetry at low energies, but also allows for a
continuous family of 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 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
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