The final panel discussion at the Maryland SEARCH workshop — six theoretical particle physicists talking about the 2011 experimental results from the Large Hadron Collider [LHC] and looking ahead to the 2012 data — has finally been posted online, along with the rest of the presentations at the workshop. I wrote about the workshop, which took place in mid-March, here and here. In the latter post, I wrote:
The workshop concluded with a panel discussion — the only point during the entire workshop when theorists were formally asked to say something. The panel consisted of Michael Peskin (senior statesman [and my Ph.D. advisor] famous for many reasons, including fundamental work on the implications of highly precise measurements ), Nima Arkani-Hamed (junior statesman, and famous for helping develop several revolutionary new ways of approaching the hierarchy problem), Riccardo Rattazzi (also famous for conceptual advances in dealing with the hierarchy problem), Gavin Salam (famous for his work advancing the applications of the theory of quarks and gluons, including revolutionary methods for dealing with jets), and myself (famous for talking too much… though come to think of it, that was true of the whole panel, except Gavin.) And Raman Sundrum, one of the organizers (and famous for his collaboration with Lisa Randall in introducing “warped” extra dimensions, and also anomaly-mediated supersymmetry breaking [which was competitive with a paper by Rattazzi and his colleagues]) informally participated too.
What I like most about this discussion is that it captures a historic moment, as we are still mulling over the field-altering implications of the 2011 LHC data, but before we have enough data to really figure out what it’s telling us. It is interesting to see where the panelists largely agree with one another and where they don’t. And it will be fascinating to look back at this video even as soon as a year from now; the same panel, if it were to be held in March 2013, would surely have very different things to say. Maybe when we get there I’ll ask the panelists to write about how their views have changed over the year.
I feel I should say something about the fact that all the members of this panel are male. You should not conclude that the leading figures in the field are all male. Certainly if Lisa Randall [Harvard University] or Ann Nelson [University of Washington], two of the greatest theoretical particle physicists working today (and with whom I was fortunate to write papers in the 90s), had attended this conference, I am sure they would have been sitting on this panel, in place of less eminent panelists (me, for instance).
Now on to the video:
Left to right (from the viewer’s point of view):
- Raman Sundrum [University of Maryland], (initially standing and speaking off camera),
- Michael Peskin [SLAC and Stanford University],
- Nima Arkani-Hamed [Institute for Advanced Study],
- Gavin Salam [CERN (the LHC lab), Paris and Princeton],
- Me [Rutgers University],
- Riccardo Rattazzi [Ecole Polytechnique Federale de Lausanne]
Questions are asked off-camera by professor Patrick Meade of the State University of New York at Stonybrook. (Meade, Sundrum and Michele Papucci of Berkeley organized the workshop.)
If you’re a particle physicist, you’ll have no trouble following the panel, but for those of you who aren’t, I’m afraid this is a high-level discussion which often lapses into jargon (see the limited glossary below). And it can get a little slow, so I think it unlikely that many non-experts will want to listen to the whole thing. So let me give you a few pointers (in both senses of the word).
- The discussion is 1 hour 23 minutes long.
- There are about two minutes of intro. Then from about 3:25 to 4:07 there’s a technical glitch which they didn’t edit out; skip til the video returns.
- From there, Professor Peskin presents his Four Slogans for 2012, which I described in an earlier post; now you can see them for yourself, though the language is quite technical.
Then the questions start (times listed):
- What would you personally most like the experimentalists at ATLAS and CMS [the two general-purpose experiments at the LHC] to look for in 2012? (0:09:00 – 0:30:00) [fairly technical answers]
- Do you think the excess seen at around a mass of 125 GeV/c2 in the search for the Standard Model Higgs particle is really a Higgs? (0:30:00 – 0:35:00) [less technical; this regards the hints in the data that I have written about here, here and here.]
- Where do you think supersymmetry stands right now, given that no sign of superpartner particles were seen in 2011, and given that there might be a Standard-Model-like Higgs at 125 GeV/c2?(0:35:00 – 1:05:00) [fairly technical; see the articles linked from this one for relevant background information, and this article for my detailed answer to this question.]
- What is the one experimental result that would give you the most insight into BSM (see glossary below) physics? (1:05:00-1:11:00) [fairly technical]
- What do you see as the role of theorists who think about BSM physics going into the coming year(s)? (1:14:00-end) [less technical]
At a minimum I recommend non-experts listen to a little of what the brilliant, entertaining, and famously long-winded Nima Arkani-Hamed, of the Institute for Advanced Study, has to say; he’s larger than life and a lot of fun to watch. He waxes poetic a few times, and in some cases reviews moments in scientific history in an interesting way; see examples at 0:14:45, 0:40:00 [over ten minutes!], 1:14:55.
If you are curious about my own views, I suggest 0:20:00 (Higgs and 2012), 0:32:00 (is there a Higgs particle appearing in current data?) and 1:20:00 (more general philosophy about doing physics at the LHC).
Finally, a short glossary to help the non-experts, and even the younger grad students, through the jargon.
- “QCD” = Quantum ChromoDynamics, the highly-developed theory of quark and gluons whose equations are crucial for predicting anything and everything at the LHC
- “BSM” = Beyond-the-Standard-Model (i.e. something from new particles and/or forces)
- “RS” = Randall-Sundrum version of extra-dimensions ideas.
- “hierarchy problem”; click here for an explanation.
- “theoretical prior” = strong expectation based on a combination of past experiments and the current theoretical framework of quantum field theory
- “SUSY” = supersymmetry
- “stop”= top squark, “sbottom” = bottom squark — superpartner particles of the top and bottom quarks
- “gluino” = superpartner particle of the gluon
- “flavor” = relating to the various types of quarks, charged leptons and neutrinos, mainly regarding their masses and their decay modes
- “WIMP” = Weakly-Interacting Massive Particle (i.e. a particle that feels the weak nuclear force) that might or might not make up the dark matter of the universe
- sequential z prime, – a heavy version of a Z particle
- vector like single top quark – a heavy version of a top quark, see https://profmattstrassler.com/2012/02/02/lhc-as-juggernaut-and-behemoth/
- TDR – technical design report for an experiment
- b tags – see https://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-apparently-elementary-particles/jets-the-manifestation-of-quarks-and-gluons/b-tagging-identifying-jets-from-bottom-quarks/
- Rpp decay = RPV decay = R-Parity-Violating decay = violation of assumption 1 in https://profmattstrassler.com/articles-and-posts/some-speculative-theoretical-ideas-for-the-lhc/supersymmetry/how-to-look-for-supersymmetry-at-the-lhc/
- maximally natural solution to heirachy problem = see https://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-hierarchy-problem/ first, then a natural solution is a theory that accomodates the hierarchy readily, for many possible values of its parameters, i.e. without the need to adjust the parameters of the theory to very precise values.
- long lived colour particles (color –> colored) = a heavy quark-like particle that lives much longer than a trillionth of a second and may travel some distance through (or all the way through) the ATLAS or CMS detectors before it decays
- relic abundance of DM = how much dark matter is left over after the Big Bang
- sigma term(time) branching ratio = sigma times branching ratio = production rate times the probability for a certain type of decay.
- natural theory at weak scale = see “natural solution to hierarchy problem” above; “weak scale” is around 1 TeV, meaning accessible to the LHC
- t/tbar/MET = top quark + top antiquark + missing tranverse momentum, as would arise from producing a top squark and antisquark pair, where the top squark decays to a top quark and an undetectable particle, and the top antisquark decays to a top antiquark and an undetectable particle
- sleuth type approaches = technique for simultaneously looking at all the data for deviations from predictions; sounds great but very dificult to carry out in practise
- top prime, bottom prime = heavy versions of a top quark and bottom quark
- natural v’s unnatural = the issue is whether a theory’s parameters must be precisely adjusted in order to get physics similar to our world (unnatural) or whether a wide range of parameters will typically lead to physics similar to our world (natural)
- 5/3 charge particles = just what it sounds like: particles with charge 5/3 times larger than that of a proton (compare with a top quark that has charge 2/3
- top squark = moderately likely (but by no means certain) to be the first superparticle discovered, IF supersymmetry exists of course!