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Hidden Valley Workshop May 11, 2009

Posted by gordonwatts in Conference, Hidden Valley, physics.

IMG_1332I spent a very enjoyable week attending a workshop here at UW – Workshop on Signatures of Long-Lived Exotic Particles at the LHC. These workshops are funded by the DOE – and allow us to fly in a small list of experts to discuss a particular topic for a week. As you might imagine, things can get pretty intense (in a good way!).

The point about long lived particles is they are long lived! And not much else in the standard model is long lived the way these guys can be. Sure, a bottom quark might travel a few millimeters – and most of us tend to call that long-lived. But the things considered at this workshop can go much furthers – meters even. All sorts of models can generate these particles – like SUSY or Hidden Valley.

Nothing in a particle physics experiment is really designed for these things – not the hardware and not the software, certainly. Not clear our brains are thinking about them too well either! This is part of what makes them so fascinating!

Take the hardware, for example. Just about everything in the Standard Model decays very quickly after it is created in a collider. Millimeters:

Exploded CDF Event DisplayThat is an exploded schematic view of what happens in our detector (this is a CDF event, I’ve stolen, from Fermilab). The inner circle on the left is about 2 inches in diameter. You see the exploded view on the right? The distance between the vertex and the secondary vertex is about a millimeter or so. That is normal long lived particle for particle physics. All of our code and the design of our detectors are built to discover exactly those kinds of long lived particles.

That picture is from the small conference dinner we set up at Anthony’s, a local nice fish place here in Seattle. I’ve got more pictures from the dinner posted on my flickr account.



1. Long Lived Particles Break HEP « Life as a Physicist - May 13, 2009

[…] Particles Break HEP May 13, 2009 Posted by gordonwatts in Conference, physics. trackback In my last post I mentioned that long lived particles break some basic assumptions that we make in the way we […]

2. Mefisto - May 14, 2009

What about those HUGE detectors at LHC, such as CMS or ATLAS, where they have calorimeters (I think these can be called detectors) meters away from the “collision point”? Im really new into this kind of physics, but how does this relates or compares to this long-lived particles travelling 1 milimeter. Im asking because this calorimeters are meters away so there are particles travelling that far, what about those?

3. Gordon Watts - May 15, 2009

Yeah — that is the thing. If they are very short lived – 1 or 2 mm for example, then the detector doesn’t matter. If they are very long – meters or similar, then it does matter. The calorimeters are on the order of meters – so the particles could definately decay in the calorimeter. This requires a real difference in how we detect the particles. They will tend to leave signals that we normally don’t see – ones that may be discarded as noise by the normal analysis software! Ops!

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