# Particle Physics

This series consists of talks in the areas of Particle Physics, High Energy Physics & Quantum Field Theory.

## Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

## Effective theories and nucleons: implications for neutrinos, dark matter and atoms

Thursday Mar 31, 2016

The venerable proton continues to play a central role in fundamental particle physics. Neutrinos scatter from protons in neutrino oscillation experiments, Weakly Interacting Massive Particles (WIMPs) are expected to scatter from protons in dark matter searches, and electrons or muons are bound by protons in precision atomic spectroscopy.

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## What is the gamma gamma resonance at 750 GeV?

Tuesday Mar 29, 2016
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I will discuss the recent LHC excess in the di-photon distribution at an invariant mass of 750 GeV. Various explanations in terms of weakly coupled and strongly coupled physics will be presented. Possible connection with Dark Matter will also be discussed.

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## A dark-matter hunter’s guide to the Galaxy (and beyond)

Friday Mar 18, 2016
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Understanding the microscopic nature of dark matter (DM) is one of the most outstanding problems facing modern physics. There is to-date no evidence for non-gravitational interactions of DM with the rest of the Standard Model and also no hint for any particular DM mass. My talk with focus on new techniques to search for GeV-TeV scale weakly-interacting DM by looking for DM annihilating in the cosmos into cosmic rays such as gamma-rays and neutrinos.

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## S-Duality and Helicity Amplitudes

Friday Mar 11, 2016
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I will demonstrate that SL(2,Z) duality is a property of all low-energy effective Abelian theories with electric or magnetic charges The duality will be verified at one loop by comparing the amplitudes in the case of an electron and the dyon that is its SL(2,Z) image, and I will show that it can be extended order by order in perturbation theory. I will discuss how the duality generically breaks down at high energies, and show how the results apply to the Seiberg-Witten theory.

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## Boundary-Bulk Relation in Topological Orders

Thursday Mar 10, 2016
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## Phenomenology of semileptonic B-meson decays with form factors from lattice QCD

Tuesday Mar 08, 2016
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In this talk, I discuss several application of semileptonic B-meson form factors. Topics include the determination of $|V_{ub}|$ and $|V_{cb}|$, hints for new physics in semitauonic decays, and Standard-Model predictions for flavor-changing-neutral-current processes: $B\to P\nu\bar{\nu}$ and $B\to P\ell^+\ell^-$, where $P$ denotes a pion or kaon.

I will also cover some details of the underlying lattice-QCD calculations at a nontechnical level.

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## Exploring the Weak Gravity Conjecture

Friday Mar 04, 2016
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The Weak Gravity Conjecture (WGC), in its original form, says that given an abelian gauge theory there should be at least one charged particle whose charge is bigger than its mass in Planck units. This has surprisingly powerful implications for the possibility of large-field inflation. In this talk I will explore some of the arguments linking the WGC to inflation before taking a closer look at a different question: which version of the WGC should we be trying to prove?

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## Ultralight Axions

Tuesday Mar 01, 2016
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Axions, having a perturbative shift symmetry, can have masses much smaller than other types of particles in a technically natural way. Ultralight axions (ULAs) with m~10^{-22} eV are attractive dark matter candidates with novel properties that distinguish them from cold dark matter (CDM). A single ULA with a GUT scale decay constant provides the correct relic density without fine-tuning. Quantum gravitational effects are expected to break continuous global symmetries, and may spoil the axion potential.

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Tuesday Feb 16, 2016
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Asymptotically AdS spacetimes with reflecting boundary conditions represent a natural setting for studying superradiant instabilities of rotating or charged black holes. In the first part of this talk, I prove that all asymptotically AdS black holes with ergoregions in dimension d ≥ 4 are linearly unstable to gravitational perturbations. This proof uses the canonical energy method of Hollands and Wald in a WKB limit.

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## Electroweak Monopole - Yongmin Cho

Tuesday Feb 09, 2016

We propose the discovery of the electroweak monopole as the final test of the standard model. Unlike the Dirac's monopole in electrodynamics which is optional, the electroweak monopole must exist within the framework of the standard model because the $U(1)_{em}$ becomes non-trivial. We estimate the mass of the monopole to be around 4 to 7 TeV, and expect the production rate to be relatively large, $(1/\alpha_{em})^2$ times bigger than the WW production rate. This implies that the MoEDAL detector at LHC could have a real chance to detect it.

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## LECTURES ON-DEMAND

### Roger Melko: Perimeter Institute and University of Waterloo

Speaker: Roger Melko