Dark Matter

At a Workshop on Hidden Particles at the LHC

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Cutting edge particle physics today:

I’ve been spending the week at an inspiring and thought-provoking scientific workshop. (Well, “at” means “via Zoom”, which has been fun since I’m in the US and the workshop is in Zurich; I’ve been up every morning this week before the birds.) The workshop brings together a terrific array of particle theorists and Large Hadron Collider [LHC] experimenters from the ATLAS and CMS experiments, and is aimed at “Semi-Visible Jets”, a phenomenon that could reveal so-far-undiscovered types of particles in a context where they could easily be hiding. [Earlier this week I described why its so easy for new particles to hide from us; the Higgs boson itself hid for almost 25 years.]

After a great set of kick-off talks, including a brand new result on the subject from ATLAS (here’s an earlier one from CMS) we moved into the presentation and discussion stage, and I’ve been learning a lot. The challenges of the subject are truly daunting, not only because the range of possible semi-visible jets is huge, but also because the scientific expertise that has to be gathered in order to design searches for semi-visible jets is exceptionally wide, and often lies at or beyond the cutting edge of research.

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Long Live LLPs!

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Particle physics news today… I’ve been spending my mornings this week at the 11th Long-Lived Particle Workshop, a Zoom-based gathering of experts on the subject.  A “long-lived particle” (LLP), in this context, is either a detectable particle that might exist forever, or a particle that, after traveling a macroscopic, measurable distance — something between 0.1 … Read more

LIGO detects a second merger of black holes

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There’s additional news from LIGO (the Laser Interferometry Gravitational Observatory) about gravitational waves today. What was a giant discovery just a few months ago will soon become almost routine… but for now it is still very exciting… LIGO got a Christmas (US) present: Dec 25th/26th 2015, two more black holes were detected coalescing 1.4 billion … Read more

LHC Starts Collisions; and a Radio Interview Tonight

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In the long and careful process of restarting the Large Hadron Collider [LHC] after its two-year nap for upgrades and repairs, another milestone has been reached: protons have once again collided inside the LHC’s experimental detectors (named ATLAS, CMS, LHCb and ALICE). This is good news, but don’t get excited yet. It’s just one small step. … Read more

More on Dark Matter and the Large Hadron Collider

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As promised in my last post, I’ve now written the answer to the second of the three questions I posed about how the Large Hadron Collider [LHC] can search for dark matter.  You can read the answers to the first two questions here. The first question was about how scientists can possibly look for something … Read more

Dark Matter: How Could the Large Hadron Collider Discover It?

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Dark Matter. Its existence is still not 100% certain, but if it exists, it is exceedingly dark, both in the usual sense — it doesn’t emit light or reflect light or scatter light — and in a more general sense — it doesn’t interact much, in any way, with ordinary stuff, like tables or floors … Read more

The LHC restarts — in a manner of speaking —

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As many of you will have already read, the Large Hadron Collider [LHC], located at the CERN laboratory in Geneva, Switzerland, has “restarted”. Well, a restart of such a machine, after two years of upgrades, is not a simple matter, and perhaps we should say that the LHC has “begun to restart”. The process of … Read more

Dark Matter Debates

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Last week I attended the Eighth Harvard-Smithsonian Conference on Theoretical Astrophysics, entitled “Debates on the Nature of Dark Matter”, which brought together leading figures in astronomy, astrophysics, cosmology and particle physics. Although there wasn’t much that was particularly new, it was a very useful conference for taking stock of where we are. I thought I’d bring you a few selected highlights that particularly caught my eye.

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