Theory Seminars Archive

Thursday, November 10, 2016

Speaker: Harri Waltari

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Collider signatures of sneutrino dark matter in left-right symmetric supersymmetry

Abstract:

A right-handed sneutrino is a viable dark matter candidate in supersymmetry in addition to the more conventional neutralino option. Right-handed sneutrinos are a natural part of left-right symmetric supersymmetric models, where the gauge sector is extended with right-handed weak interactions. We studied the sneutrino dark matter option in left-right supersymmetry and its signatures at the LHC. We find that we may satisfy the constraints from relic density, low-energy observables and direct SUSY searches. The easiest way to produce the sneutrino would be via the right-handed gauge sector, where the decays of W_R to sleptons lead to multilepton final states. We compare some benchmarks to the case of a neutralino LSP. We may get a detectable signal with high luminosities even with the right-handed W-boson being around 3.5 TeV.

Thursday, November 3, 2016

Speaker: Matthew Reece

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Exploring the Weak Gravity Conjecture

Abstract: 

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 discuss some of the arguments linking the conjecture to cosmology, and present some new evidence that strong versions of the conjecture are likely to be true.

Thursday, October 20, 2016

Speaker: Csaba Csaki

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Twin phenomenology

Abstract: 

I discuss three aspects of phenomenology of twin Higgs models. First I argue that some versions of these models will produce displaced Higgs decays and examine in detail the feasibility of discovering such displaced decays in the tracker of the LHC experiments. Second I will examine flavor bounds on composite twin Higgs models. Finally I investigate how feasible identical twin Higgs models are: the number of relativistic degrees of freedom depends strongly on the decoupling temperature which can be dialed via the structure of the twin neutrino sector.

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

Abstract: 

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)"

Abstract: 

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

Abstract:
 

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

Abstract:  

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.