Paper Explainer: Applying Liouville's Theorem to Gaia Data

Paper Explainer: Applying Liouville's Theorem to Gaia Data

This is an explainer for my recent paper with David Hogg and Adrian Price-Whelan. This is a very different kind of paper for me, as evidenced by the fact that it is coming out on arXiv’s astro-ph (astrophysics) list and not even cross-listed to hep-ph (high energy phenomenology). In the end, the goal of the research that produced this paper is to learn about dark matter, but this paper by itself barely mentions the subject. There is a connection though.

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Paper Explainer: Direct Detection Anomalies in light of Gaia Data

Paper Explainer: Direct Detection Anomalies in light of Gaia Data

This is an explainer for my recent paper with Gopolang (Gopi) Mohlabeng and Chris Murphy on the implications of recent surveys of dark matter velocity distributions from the Gaia mission on dark matter direct detection. There are a bunch of moving parts in this paper, as we’re trying to tie together some new directions from astrophysics with a long-standing problem in particle dark matter, so let me go through them.

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Paper Explainer: Gravitational probes of dark matter physics

Paper Explainer: Gravitational probes of dark matter physics

The central thesis of the paper is that there is a huge potential to learn about the properties of dark matter: things like mass, interactions, production, etc using measurements from astronomy. This is not a completely novel idea: we know a great deal about dark matter from astronomy and cosmology (for example: dark matter is "cold" and not "hot"). However, there is an immense opportunity in the near future to do far more, thanks to improvements in simulation and some powerful new astronomical surveys which will be occurring. 

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Workshop talk: Mining LHC Data

Workshop talk: Mining LHC Data

I'm at Fermilab for an LPC (LHC Physics Center) workshop on new ideas for LHC dark matter searches. I have been working with my fellow professor David Shih, postdocs Anthony DiFranzo and Angelo Monteux, and grad student Pouya Asadi at Rutgers on new ways to look for interesting anomalies in LHC data (see our paper and my blog post about it). Though not specifically about dark matter, it is a new idea, and so I have a talk about it. Here are the slides.

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TRISEP Summer School Lectures

TRISEP Summer School Lectures

I'm up in Laurentian University in Sudbury, Ontario, giving three hours of lectures on "Beyond the Standard Model physics and the LHC" for the TRISEP Summer School.

TRISEP this year is mostly experimental grad students, and mostly experimental grad students working on experiments in the underground labs (such as SNOLAB in Sudbury). I'm the only lecturer who's talking about Beyond the Standard Model physics in general (though specific topics like dark matter and neutrino physics are being covered in more detail by other lecturers), and the only one talking about the LHC. Given that, and the audience, I ended up giving a broad overview: first on the sort of things we theorists have reason to think must exist beyond the Standard Model, then how the LHC works (always entertaining to have a theorist speak on how experiments work), and then lastly on how we look for new physics at the LHC. The slides are below.

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Paper Explainer: Collapsed Dark Matter Structures

Paper Explainer: Collapsed Dark Matter Structures

This is a description of a paper I’ve written with my postdoc, Anthony DiFranzo. In our paper, we consider the possibility that dark matter could form gravitationally collapsed objects, evolving from an initial state of nearly uniform distribution across the Universe into one where it forms compact objects, analogous to have the regular matter that you and I are made of eventually formed stars and galaxies. Usually, we think this is not possible for dark matter, due to evidence that, on the largest scales, dark matter forms gravitationally bound structures that are much "fluffier" than the collapsed stars and galaxies. 

However, as we show in the paper, there is a way for dark matter to evolve into compact objects on small scales (say, a thousandth the size of the Milky Way), while still satisfying the constraints we've observed at larger scales. In demonstrating that it is possible for dark matter to do this, I think our paper makes an important point about some open questions in the field of dark matter research.

To explain why I started thinking about this particular project, I want to motivate it with a somewhat whimsical question.

Can there be planets and stars made of dark matter?

 

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Paper Explainer: Hiding Thermal Dark Matter with Leptons

Paper Explainer: Hiding Thermal Dark Matter with Leptons

This is a description of my recent paper with my student David Feld. 

Dark matter is a problem. We know that there is a gravitational anomaly in galaxies: the stuff we can see is moving far too fast to be held together by its own gravity. Add to this the precision measurements of the echoes of the Big Bang (the Cosmic Microwave Background), which tells us that the way the Universe was expanding and matter was clumping cannot be explained without some new stuff that didn’t interact with light, and you have very solid evidence for the existence of dark matter. Then of course, there is the Bullet Cluster, where we can see the gravitational imprint of dark matter directly.

So we know it exists. We just don’t know what it is.

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Paper Explainer: Two is not always better than one: Single Top Quarks and Dark Matter

Paper Explainer: Two is not always better than one: Single Top Quarks and Dark Matter

A few months ago, I was lucky enough to be contacted by an experimental student in the CMS collaboration, Deborah Pinna. Deborah had a question for me: in a certain set of dark matter models that I had written one of the early papers on, we only considered one particular class of final states, namely production of dark matter at the LHC along with a pair of top quarks. Why, she asked, did we not also consider the production of a single top quark, along with dark matter?

The answer was that everyone, including myself, just assumed that this channel didn’t matter. I’ll explain why in a bit, but I had just assumed that the rate at which this sort of event could occur would be so low that I never actually bothered to check. It turned out that my intuition was wrong. Deborah did check, and upon finding out that this single-top channel mattered, contacted me, assuming perhaps there was a good reason for ignoring it. There wasn’t.

I was really happy to contribute to Deborah’s project, and I want to emphasize that she and a postdoc, Alberto Zucchetta, did all of the heavy lifting on this paper.

So what was the idea? What is single versus pair production of tops, and why does it matter?

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Paper Explainer: Vector Boson Fusion Searches for Dark Matter at the LHC

Paper Explainer: Vector Boson Fusion Searches for Dark Matter at the LHC

Here, I describe a recent paper I wrote with a group of experimentalists (Jim Brooke, Patrick Dunne, Bjoern Penning, and Miha Zgubic) and a Rutgers undergrad, John Tamanas. We investigated the ability of the Large Hadron Collider (LHC) to find dark matter using a particular type of event, one called “vector boson fusion,” or VBF.

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Paper Explainer: Assessing Astrophysical Uncertainties in Direct Detection with Galaxy Simulations

Paper Explainer: Assessing Astrophysical Uncertainties in Direct Detection with Galaxy Simulations

This is a description of a recent paper of mine, with Jonathan Sloane (a graduate student in the astro group here at Rutgers), Alyson Brooks (also a professor at Rutgers), and Fabio Governato (faculty at U Washington). We took high resolution simulations of galaxies like the Milky Way, and looked at what that can tell us about how dark matter is moving near the Earth, and what that means for how direct detection experiments look for dark matter.

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Recent Paper: Constraining the Strength and CP Structure of Dark Production at the LHC: the Associated Top-Pair Channel

Recent Paper: Constraining the Strength and CP Structure of Dark Production at the LHC: the Associated Top-Pair Channel

I'm going to describe my most recent paper, written with my now-frequent collaborator, Dorival Gonçalves, postdoc at the IPPP at Durham University. This paper is closely related to Dorival and my previous paper together, which I wrote about here. In fact, this was the project we were working on when we realized what we were doing had application to Higgs physics. When that happened, we decided to drop what we were currently working on and rush out the Higgs-related paper. Then we returned to the original idea, which was to find ways to study dark matter production at the LHC.

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Recent Paper: Dark Matter in Leptophilic Higgs Models After the LHC Run-I

Recent Paper: Dark Matter in Leptophilic Higgs Models After the LHC Run-I

In this post, I'll talk about my recent paper, written with my graduate student, David Feld.

This paper is interested in leptophilic Higgs models, and their possible connection to dark matter. I'll explain what those are in a bit. Such models have been considered before, but looking around at the literature, we didn't see a lot that had been updated after the discovery in 2012 of the Higgs boson at 125 GeV. We wanted to see what changed once we folded these new results in to the mix.

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