Theory Seminars Archive

Thursday, October 6, 2016

Speaker: David  Curtin

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: The Lifetime Frontier

Abstract: Searches for long-lived particles (LLPs) at the LHC are broadly motivated in almost any BSM scenario that addresses one or more of the long-standing puzzles of high energy physics. I will focus on some recent theory developments in Neutral Naturalness to motivate study of exotic Higgs decays to LLPs, the production and annihilation of quirkonia into Emerging-Jet-like final states, and additional cosmological probes. The LLP signature space is as big as the space of prompt searches, and is just starting to be explored. In particular, very long and very short lifetimes have not yet been adequately studied. I outline how such signatures can be looked for at the LHC, and advocate for the construction of a dedicated surface detector called MATHUSLA for the HL-LHC upgrade.

Thursday, September 15, 2016

Speaker: Prateek Agrawal

Time: 3:30PM -- 4:30PM

Location: HP5345

Title: The cosmological constant problem in scalar gravity


I will discuss a toy theory of gravity where the gravitational force is mediated by a scalar particle. This theory can be understood as the low-energy limit of a spontaneously broken Conformal Field Theory, and serves as an intriguing analog to General Relativity, capturing many qualitative features. In fact, it exhibits a fine-tuning problem closely resembling the cosmological constant problem. A solution to this cosmological constant problem in scalar gravity has been proposed. I will discuss an explicit realization of this solution and its connections with the cosmological constant problem in our universe.

Thursday, April 7, 2016

Speaker: Ian Low

Time: 3:30PM -- 4:30PM

Location: PA 234

Title: "The LHC Awakens: Signs of Hope (and Despair)"


I will summarize findings from Run 1 and early Run 2 of the LHC, focusing on signs of (non)deviations from the standard model of particle physics.

Thursday, March 24, 2016

Speaker: David Shih

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Dark Matter, the Higgs and Natural SUSY

Abstract: The natural MSSM is looking increasingly disfavored by the 125 GeV Higgs mass and dark matter direct detection. In this talk, I will present a simple, economical extension of the MSSM that generates the required Higgs mass and includes thermal WIMP dark matter consistent with all existing constraints, all while greatly reducing the fine-tuning. I will discuss prospects for future direct detection experiments and the LHC. 

Thursday, March 10, 2016

Speaker: Eder Izaguirre

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: The vector portal: a window to a dark sector


An emerging paradigm in particle physics is the possibility that new matter resides in its own sector — a Dark Sector (DS) — connected to the Standard Model via a portal. In this talk I will focus on a well-motivated example of such a scenario: the vector portal. I will discuss two distinct phases of the theory. In one, matter in the DS is uncharged under the known forces and is a viable candidate for light Dark Matter. In the other phase of this framework, matter in the DS can instead acquire a non-quantized electromagnetic charge. I will describe proposals for new small-scale experiments to sharply test the different phases of the vector portal.

Thursday, February 25, 2016

Speaker: Matthew Baumgart

Time:  3:30PM -- 4:30PM

Location:  101 PA

Title:   Effective Field Theory of Heavy WIMP Annihilation


We systematically compute the annihilation rate for winos and higgsinos into the final state gamma + X.  The radiative corrections to this process receive enhancement from the large Bloch-Nordsieck-Violating Sudakov logarithm, log(2 M_\chi/M_W).  We resum the double logs and include single logs to fixed order using a formalism that combines nonrelativistic and soft-collinear effective field theories.  For the wino case, we adapt an exclusion curve using results of the HESS experiment.  At the thermal relic mass of 3 TeV, LL' corrections result in a ~30% reduction in rate relative to LL.  Nonetheless, single logs do not save the wino, and it is still excluded by an order of magnitude.  Experimental cuts produce an endpoint region which, our results show, significantly effects the higgsino rate at its thermal relic mass near 1 TeV and is deserving of further study.