Science

Mars Science Laboratory Touches Down Tonight

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Nowadays everyone calls it the “Curiosity rover,” but I got to know it as the Mars Science Laboratory, and I’m too old and set in my ways to switch. Launched on November 26, 2011, the mission is scheduled to land on Mars’s Gale Crater tonight/tomorrow morning: 5:31 UTC, which translates to 1:30 a.m. Eastern time or 10:20 p.m. Pacific. See here and here for info about where to watch. Between this and the Higgs boson, the universe is clearly conspiring to keep science enthusiasts on the East Coast from getting a proper night’s sleep.

NASA has done a great job getting people excited about the event, and one of their big successes has been this video, “Seven Minutes of Terror.” Love the ominous soundtrack.

7 Minutes of Terror: The Challenges of Getting to Mars

Mars is about fourteen light-minutes away from Earth, so scientists at the Jet Propulsion Laboratory aren’t actually able to fine-tune the spacecraft’s approach, like you used to do playing Lunar Lander in the arcade back in the day. Everything has to be carefully programmed well ahead of time, setting up an elaborately choreographed series of events that guides the lander through the seven-minute journey from the top of the Martian atmosphere to eventual touchdown. I still struggle with parallel parking, which is why I’m a theoretical physicist and not a JPL engineer.

This isn’t NASA’s first rodeo, of course. …

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Higgs Papers Out

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We were all transfixed by the Higgs seminars on July 4, but the work was nowhere near over for the experimentalists — they had to actually write up papers describing the results. And of course taking the opportunity to do a little more analysis along the way.

Now the papers have appeared on the arxiv. (Via lots of places, e.g. symmetry breaking and Matt Strassler.) Here’s ATLAS:

Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC

The ATLAS Collaboration
(Submitted on 31 Jul 2012)

A search for the Standard Model Higgs boson in proton-proton collisions with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities of approximately 4.8 fb^-1 collected at sqrt(s) = 7 TeV in 2011 and 5.8 fb^-1 at sqrt(s) = 8 TeV in 2012. Individual searches in the channels H->ZZ^(*)->llll, H->gamma gamma and H->WW->e nu mu nu in the 8 TeV data are combined with previously published results of searches for H->ZZ^(*), WW^(*), bbbar and tau^+tau^- in the 7 TeV data and results from improved analyses of the H->ZZ^(*)->llll and H->gamma gamma channels in the 7 TeV data. Clear evidence for the production of a neutral boson with a measured mass of 126.0 +/- 0.4(stat) +/- 0.4(sys) GeV is presented. This observation, which has a significance of 5.9 standard deviations, corresponding to a background fluctuation probability of 1.7×10^-9, is compatible with the production and decay of the Standard Model Higgs boson.

And here’s CMS:

Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC

The CMS Collaboration
(Submitted on 31 Jul 2012)
Results are presented from searches for the standard model Higgs boson in proton-proton collisions at sqrt(s)=7 and 8 TeV in the CMS experiment at the LHC, using data samples corresponding to integrated luminosities of up to 5.1 inverse femtobarns at 7 TeV and 5.3 inverse femtobarns at 8 TeV. The search is performed in five decay modes: gamma gamma, ZZ, WW, tau tau, and b b-bar. An excess of events is observed above the expected background, a local significance of 5.0 standard deviations, at a mass near 125 GeV, signalling the production of a new particle. The expected significance for a standard model Higgs boson of that mass is 5.8 standard deviations. The excess is most significant in the two decay modes with the best mass resolution, gamma gamma and ZZ; a fit to these signals gives a mass of 125.3 +/- 0.4 (stat.) +/- 0.5 (syst.) GeV. The decay to two photons indicates that the new particle is a boson with spin different from one.

…

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Music Was Better in the Sixties, Man

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Actually, popular music is arguably “better” today. But in the Sixties it was more creative — or at least more experimental. So says science. (Via Kevin Drum.)

The science under consideration was carried out by a group of Spanish scientists led by Joan Serrà, and appeared in Scientific Reports, an open-access journal published by Nature. They looked at something called the Million Song Dataset, which is pretty amazing in its own right. The MSD collects data from over a million songs recorded since 1955, including tempo and volume and some information about the pitches of the actual notes (seems unclear to me exactly how detailed this data is).

And the answer is … popular music is in many ways unchanged over the years. The basic frequencies of different notes and so forth haven’t changed that much. But in certain crucial ways they have: in particular, they’ve become more homogeneous. This chart shows “timbral variety” over the years — a way of measuring how diverse the different kinds of sounds appearing in songs are. Nobody should really be surprised that the late 1960’s was the peak of different kinds of instrumentation being used in pop music. On the other hand, one could I suppose argue that this is because back then we didn’t know how to do it right, and there was a lot of experimental crap, whereas we’ve now figured it out. I suppose.

On the other hand, songs have gotten louder! So you get more volume for your money.

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Cosmology and Philosophy at La Pietra

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I’ve traded off my reasons for not blogging much of late. Last week and before it was The Particle at the End of the Universe (in stores November 13!), but that’s now been handed in and I can kick back and catch up on my martini-drinking. Except that instead of doing that, I instantly hopped on a plane for Europe, where I’m now participating in a workshop on philosophy and cosmology. Not that you should feel sorry for me — the workshop is being held at the La Pietra conference center, a beautiful facility owned by NYU in Florence. I’m not sure why NYU owns a conference center in Florence; it could have been a targeted purchase, but it could easily have just been a gift. (Caltech for a while owned an abandoned gold mine. Universities get all sorts of crazy gifts.) But at least temporarily, martinis have been put aside for Chianti and limoncello.

And work, of course. This is my favorite kind of workshop: less than twenty people, gathered around a table, with no fixed agenda, talking about issues of mutual interest as they come up. This group has both scientists and philosophers, although probably more of the latter. So far each day has featured a scientist — Joel Primack, me, Brian Greene, Scott Aaronson — giving some very general remarks, while everyone else takes turns whacking them with (metaphorical) sticks. My own talk started at 11 a.m. and didn’t finish until 5:30 p.m., with breaks for lunch and coffee. So it’s exhausting both intellectually and physically, but very rewarding to have the chance to dig very deeply into difficult issues.

My talk was about — you guessed it — the arrow of time. Most people in the room are already familiar with the basic story that time’s arrow is (at least mostly) a consequence of the increase of entropy over time, and that our current universe has low entropy, but the entropy was even much lower in the past, and that last fact demands cosmological explanation. The central question concerned what would count as an “explanation.” …

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Dark Matter Still Hiding

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After a few provocative hints over the last few years, new results in the search for weakly-interacting dark matter have come up empty. The latest is from XENON100, a liquid-xenon scintillation detector under the mountain in Gran Sasso, Italy. Here are the talk slides by Elena Aprile (pdf) from the Dark Attack conference in Switzerland (via Flip Tanedo).

And here’s the money plot; dark matter mass is on the horizontal axis, interaction cross section between dark matter and nucleons is on the vertical axis. The colorful bands represent the exclusion limits; anything above that is ruled out.

A couple things to note. The blobs scattered around the plot represent those provocative hints I referred to — the tentative evidence from previous experiments that they might actually be seeing something. XENON seems inconsistent with all of them. However, you can only make a plot like this under certain theoretical assumptions. Even if those assumptions are quite likely to be true, it’s hard to be completely definitive about one experiment ruling out another one, unless they’re really using identical techniques (which none of these are). It’s possible, although maybe hard to imagine, that some complicated dark-matter physics can make everything consistent.

The second point is the dark grey area at the bottom right. That represents a bunch of theoretical predictions in supersymmetric models. As Flip cautions, we don’t have a sensible measure on the space of all models, so the blob should be taken as suggestive rather than definitive. But the suggestion is clear: we’ve ruled out some models, but there are plenty that we haven’t yet reached.

Progress continues. XENON100 used 150kg of liquid xenon; the plan is to upgrade to one ton. Once that happens, they should be able to improve the limits on the cross section by a factor of 1000, which will swipe into a much larger region of parameter space. We’ll see what happens.

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Science Friday

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Back in Los Angeles, after my brief action-packed jaunt to Geneva. Higgsteria continues, and I’ll be on NPR’s Science Friday later today to talk about it. That’s 2pm Eastern, 11am Pacific time. Hope to do justice to the palpable air of excitement at CERN and around the world.

After that, I think certain parts of my book are going to need some re-writes…

One thing I don’t want to get lost in all the hubbub. Amidst all the many impressive aspects of the work the physicists and machine-builders did to make the LHC happen and achieve this fantastic discovery, I was very struck by how eager people were to give credit to other people. In their main talks, both Fabiola Gianotti and Joe Incandela went out of their way to give credit to the machine builders, the technicians who worked on their experiments, and the thousands of colleagues within each collaboration who contributed to the result. But that eagerness to share credit went well beyond the official announcements — everyone we talked to was quick to point out how far-reaching and international the project really was. The very quintessence of a group effort.

Unfortunately, at least in the sciences, large groups can’t win the Nobel Prize. There will be much discussion in days to come about who deserves a prize for inventing the theory behind the Higgs; I think it’s complicated, and I’m not going to push for any particular set of people. When it comes to the experiments, the matter is easier: there’s no fair way to give it to anyone, really. There was a lot of Nobel-quality effort, without question, but I can’t see how it’s possible to narrow it down to just three people, which is the strict Nobel rule. What we really need to do is change that rule, but the folks in charge are (probably correctly) very conservative about such things, so I don’t see it happening soon.

So let me throw out one name that should at least be in the conversation: Lyn Evans, “the man who built the LHC.” Evans was in charge of the project for many years, and it was his dedication and ability that brought it to successful completion. He is now officially retired as a CERN staff member, although he’s still working as a member of the CMS collaboration and the leader of the effort to build a linear collider. He didn’t play a central role in the actual experimental effort to find the Higgs, but there’s no person who deserves more credit for enabling the conditions under which it could be found. People who are much more informed about the detailed history of the LHC and the ATLAS/CMS experiments will be in a better position that I to render such judgments, but I think the Nobel committee could do a lot worse.

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Live-Blogging the Higgs Seminar

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A couple of us are going to try to live-blog the July 4 Higgs update seminars from CERN. This effort will be subject to the whims of internet connectivity, of course, but we’ll do our best. At the moment we have correspondents on at least three different continents (I [Sean] am at CERN, JoAnne is in Melbourne for ICHEP, and I think John is in California…), so hopefully at least one of us will be able to get through. We’ll just be updating this post, so keep refreshing. You are also welcome to try the CERN webcast.

Seminars proper start at 9am Geneva time (3am Eastern time, midnight Pacific time, 5pm Melbourne time). One from ATLAS, by Fabiola Giannoti, and one from CMS, by Joe Incandela. Then a press conference after. Remember what we’re looking for: how significant is the signal, do the two experiments agree with each other, does the rate agree with the Standard Model prediction, are different channels mutually consistent with each other.

If people ask questions in the comments there is some chance that we will try to answer them.

Has there ever been a scientific discovery (if indeed we will be able to call it that) that has been anticipated so far ahead of time? Can’t think of any off the top of my head. Fasten your seatbelts!

11:38 pm Geneva time (Sean): Preliminary thought #1: There is a “nightmare scenario” that particle physicists have worried about for years. Namely: find exactly the Standard Model Higgs and nothing else at the LHC. I personally assign the nightmare scenario very low probability. Not on the basis of any inside info, just on the basis of physics. We know the Standard Model is not right; there is dark matter, there is dark energy, there is baryogenesis, there are the hierarchy and cosmological constant and strong-CP problems. It can’t be the final answer. Seems to me much more likely that there is interesting physics at the weak scale above and beyond the Higgs, than we just get stuck with a vanilla Standard Model. Beyond this physics-informed prediction, there is the wishful hope that the Higgs itself leads directly to new physics. Most obvious example: in many (most?) models of dark matter as weakly-interacting massive particles, the dominant way that dark matter and ordinary matter interact is through exchange of Higgs bosons. If that’s how nature works, the Higgs is literally a portal from our world to another. This isn’t the end of the show, it’s merely an act break (as we say in the movie biz).

11:44 pm Geneva time (Sean): Preliminary thought #2: I am a mere theorist, and let me be as legitimately humble as I can be right here. Beyond the details of whatever may or may not be found, the LHC is a gargantuan effort undertaken by literally thousands of people over the course of years and in many cases decades. This moment, we hope, is something of a payoff for their perseverance. My hat is off to the experimentalists and engineers and technicians who really made it happen.

…

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Live-Blogging the Higgs Seminar Read More »

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Hunting for Higgses

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Update: There’s a slightly expanded version of this post on the NOVA website, where I fill in some background on what the Higgs is and why we care.

Greetings from Geneva, where I’m visiting CERN to attend the much-anticipated Higgs update seminars on Wednesday, July 4. We’re all wondering whether they will say the magic words “We’ve discovered the Higgs,” but there’s more detailed information to watch out for. Hoping for some good book fodder, at the very least. (I personally am not hunting for Higgses, any more than someone who eats at a seafood restaurant has “gone fishing,” but you know what I mean.) Remember Higgs 101, and why we need it.

If at all possible, I’ll try to live-blog here at CV during the seminars. They will start at 9am Geneva time, a slot chosen to enable a simulcast in Melbourne for people attending the ICHEP Conference. For folks in the U.S., not so convenient: it’s 3am Eastern time, Midnight (July 3/4) Pacific time. Here is the seminar announcement, and of course CERN will have a live webcast. Or try to, anyway; last time something like this was arranged, back in December, the live feed collapsed pretty quickly under the load. I’m sure I won’t be the only one live-blogging: here’s Aidan Randle-Conde and Tommaso Dorigo.

So what are we looking for? …

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Hunting for Higgses Read More »

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