This series consists of talks in the areas of Particle Physics, High Energy Physics & Quantum Field Theory.
If the dark matter is made up of a bosonic particle, it can be ultralight, with a mass potentially much below 1 eV. Well-known DM candidates of this type include pseudoscalars like the QCD axion, and vectors such as hidden photons kinetically mixed with the Standard Model. Moduli, even-parity scalars with nonderivative couplings to the SM, can also be light dark matter. I will show that they cause tiny fractional oscillations of SM parameters, such as the electron mass and the fine-structure constant, in turn modulating length and time scales of atoms.
A simple way to trivially satisfy precision-electroweak and flavor constraints in composite Higgs models is to require a large global symmetry breaking scale, f > 10 TeV. This leads to a tuning of order 10^-4 to obtain the observed Higgs mass, but gives rise to a 'split' spectrum where the strong-sector resonances with masses greater than 10 TeV are separated from the pseudo Nambu-Goldstone bosons, which remain near the electroweak scale. To preserve gauge-coupling unification (due to a composite top quark), the symmetry breaking scale satisfies an upper bound f
The LHCb detector was designed to be the dedicated heavy-flavor physics experiment at the LHC, and has been the world's premier lab for studying processes where the net quark content changes for several years. These studies permit observing virtual contributions from beyond the SM particles up to very high mass scales, potentially (greatly) exceeding the direct reach of the LHC. I will summarize the constraints placed on high-mass BSM physics by such studies, and also highlight a few interesting anomalies.
The vacuum energy changes when cosmological phase transitions take place, or in environments with high temperatures or chemical potentials. The propagation of primordial gravity waves is affected through the trace anomaly, and eras where the vacuum energy dominates can lead tofeatures in the gravity wave spectrum.
I discuss a new proposal for nonperturbatively defining chiral gauge theories, something that has resisted previous attempts.
We argue that solutions to the strong CP problem motivate different searches for TeV scale physics at the LHC than are currently being emphasized. We present two solutions to the strong CP problem that require the existence of new colored particles with masses below 10 TeV. New motivated searches at the LHC would provide a strong constraint on these solutions to the strong CP problem.
I consider the Standard Model as an effective field theory (EFT) at the electroweak scale $v$. At the scale $f\geq v$ I assume a new, strong interaction that breaks the electroweak symmetry dynamically. The Higgs boson arises as a composite pseudo-Nambu-Goldstone boson in these scenarios and is therefore naturally light $(m_{h}\sim v)$. Based on these assumptions and the value of $\xi=v^{2}/f^{2}$, I explain the systematics that governs the effective expansion:\\
It has been known for a long time that quadratic gravity, which generalizes Einstein gravity with quadratic curvature terms, is renormalizable and asymptotically free in the UV. However the theory is afflicted with a ghost problem if the perturbative spectrum is taken seriously. We explore the possibility that the dimensional scale of Einstein-Hilbert term is far smaller than the scale where the dimensionless gravitational couplings become strong. The propagation of the gravitational degrees of freedom can change character at this strong interaction scale.
Quantum superpositions of matter are unusually sensitive to decoherence by tiny momentum transfers, in a way that can be made precise with a new diffusion standard quantum limit. Upcoming matter interferometers will produce unprecedented spatial superpositions of over a million nucleons. What sorts of dark matter scattering events could be seen in these experiments as anomalous decoherence? We show that it is extremely weak but medium range interaction between matter and dark matter that would be most visible, such as scattering through a Yukawa potential.