particle phenomenology

Today Josh Ruderman (NYU) gave a great Physics Colloquium, about particle physics phenomenology, from measuring important standard-model parameters with colliders to finding new particles in cosmology experiments. It was very wide-ranging and filled with nice insights about (among other things) thermal-relic dark matter and intuitions about (among other things) observability of different kinds of dark-sector activity. One theme of the dark-matter talks I have seen recently is that most sensible, zeroth-order bounds (like on mass and cross section for a thermal-relic WIMP) can be modified by slightly complexifying the problem (like by adding a dark photon or another dark state). Ruderman navigated a bunch of that for us nicely, and convinced us that there is lots to do in particle theory, even if the LHC remains in a standard-model desert.

#astrohackny, candidate Heinrich, LHC

In the morning, I got a great email from Ness, showing that we can separate red-clump and non-red-clump red-giant stars at huge confidence, using APOGEE spectra and The Cannon. I also read and gave comments on Malz's first attempt at doing inference with probabilistic redshifts.

At #astrohackny Price-Whelan and I started on the crazy Gaussian-Process blind source separation plan. We also pitched a linear version too and divided up tasks among the various hackers interested in working on the Planck data. We didn't get very far, because we spent most of our hacking time understanding this Lawrence paper (PDF).

In the afternoon, I had the pleasure of being on a committee for the oral candidacy exam of Lukas Heinrich (NYU). He spoke about RECAST, which is a system to permit outsiders to re-interpret LHC ATLAS searches in terms of new or different physics models. The idea is: If a search has been done and it is relevant to some new or different physics, there is no need to do new searches ab initio until the existing searches have been checked for the relevant physics. This all also ties into ideas of preserving workflow and reproducibility and open science, all of which are very relevant to the Moore-Sloan Data Science Environments.

probabilistic cosmology

I spent time working through some inference problems in the future of cosmology, including how you use probabilistic redshift information, how you marginalize out beliefs about the density field and galaxy formation within that density field, and how you might get probabilistic information about the 2-pt function. I am confused about how much this all matters for different kinds of projects.

At lunch, Andy Haas (NYU) told us about searches for milli-charged particles at the LHC. He has a plan that would rule out a huge class of models.

Dr Lewis

George Lewis (NYU) gave an absolutely wonderful defense of his thesis today, on top-quark physics with ATLAS at the LHC. He ruled out a range of new physics in the top mass range, and measured the top pair-production cross section more accurately than it can even be predicted in the standard model. A very nice talk and a very well-deserved PhD.