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Events on Tuesday, April 5th, 2016

Chaos & Complex Systems Seminar
Toward an atlas of the physical internet
Time: 12:05 pm
Place: 4274 Chamberlin Hall (refreshments will be served)
Speaker: Paul Barford, UW Department of Computer Sciences
Abstract: The availability of accurate and timely maps of the Internet would be a compelling starting point for diverse research topics such as assessing infrastructure vulnerabilities, understanding routing behavior, and analyzing application performance. However, despite the many and varied efforts over the years, there remains no central repository of accurate Internet maps. In this talk, I will describe the challenges in assembling maps of Internet topology based on standard data sources. I will also describes Internet Atlas, a repository and visualization portal of the physical interconnection structure of the Internet that has been under construction at the University of Wisconsin for four years. Atlas currently contains PoP/colo and link location data for over 1K networks (including all tier 1 providers) around the world. The Atlas repository was the starting point for our recent study of Internet long haul infrastructure. I will describe key results from that study on deployment characteristics and risks in US long haul infrastructure, and opportunities to improve performance and robustness.
Host: Clint Sprott
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Theory Seminar (High Energy/Cosmology)
Lepton Jets from Radiating Dark Matter
Time: 3:30 pm
Place: 5280
Speaker: Malte Buschmann, Fermilab
Abstract: The idea that dark matter forms part of a larger dark sector is very intriguing, given the high degree of complexity of the visible sector. We discuss lepton jets as a promising signature of an extended dark sector. As a simple toy model, we consider an O(GeV) DM fermion coupled to a new U(1)' gauge boson (dark photon) with a mass of order GeV and kinetically mixed with the Standard Model photon. Dark matter production at the LHC in this model is typically accompanied by collinear radiation of dark photons whose decay products can form lepton jets. We analyze the dynamics of collinear dark photon emission both analytically and numerically. In particular, we derive the dark photon energy spectrum using recursive analytic expressions, using Monte Carlo simulations in Pythia, and using an inverse Mellin transform to obtain the spectrum from its moments. In the second part, we simulate the expected lepton jet signatures from radiating dark matter at the LHC, carefully taking into account the various dark photon decay modes and allowing for both prompt and displaced decays. Using these simulations, we recast two existing ATLAS lepton jet searches to significantly restrict the parameter space of extended dark sector models, and we compute the expected sensitivity of future LHC searches.
Host: Yang Bai
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