Signs of life

Posted on April 26, 2013 by

I’m back in Vancouver. I’m about to start writing my PhD thesis soon. The last 4 months have been rather intense, but very rewarding. I can’t tell the whole story just yet, because it hasn’t ended yet. I don’t know how it will end. All I can say is that we have worked very hard to open a new chapter on the Higgs boson, and we are just about to succeed. This required a bit of a paradigm shift in the way we do analysis. It was met with a lot of healthy skepticism, but a relentless stream of proofs of concept and studies eventually convinced the upper management at ATLAS that this was the way to go. We’re in good shape.

I haven’t abandoned the blog. I will come back to writing as soon as things quiet down a bit. I had the itch to write many times, but I couldn’t find the time and energy to write well thought out pieces. The analysis I am working on is superseding everything. It’s a rare thing to be that dedicated to something. I kind of enjoy it.

Being back in Vancouver means that I get back my recording equipment. I felt like dusting off my two condenser mikes and quickly recording something. It’s the first time I record a cover song. It’s the first song I’ve ever learned on the guitar. You may recognize it, even if I took some liberty over the original. Enjoy!

** Edit **: Turns out I still had a bit of motivation to do another recording this week-end. Innocent by Our Lady Peace. Gosh I’m happy to get my recording equipment back!

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Explaining the Higgs boson discovery on the Up-Goer Five Text Editor

Posted on February 10, 2013 by

The Up-Goer Five Text Editor will check every word you type and make sure it is part of the 10,000 most common words used. It’s fun and frustrating to play with.

I took a crack at explaining the Higgs boson discovery in it. It’s very difficult when you can’t use words like “mass”, “energy”, “particle” or “interaction”. So what do you think? Does it make sense?

We think we found the smallest bits that make the world we live in. Matter can be broken down no further. These bits have four different ways of playing with each other. Let’s call these games. One of these games is not our focus because bits start playing it only when they are in very large numbers. We are interested in the games one bit can play with only a few others bits. We only know of three of those games. It turns out two games out of these three are one and the same, but they don’t appear that way in every day life.

The games are pretty much just the smallest bits of matter throwing other bits at each other. The bits being thrown around are different from the bits doing the throwing. The bits being thrown should all be very easy to push around if the two games we are talking about are to appear the same. But we know they don’t appear to be the same. So what’s going on? Maybe there is a field  that is all over the place that makes it hard for bits to move through. The field would make it harder to throw some kinds of bits around, but only some kinds. There are four kinds of bits that make our two games. Maybe only three of them feel the field. The one bit that wouldn’t feel it would appear to play its own game, while the other three would appear to play a different game.

It is possible to kick a field so hard that bits of it come off. We have been trying to kick the field for years just to know if the field is there at all. Last year, we finally managed to see some bits of it coming off, leading us to believe that the field is really there. This also means that the two games we were talking about really are the same. The field can also make all the kinds of small bits of matter harder to push around. We are checking this right now.

Here’s the text in the actual editor, so that you can check that I haven’t cheated :)

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Opposing reviews of Opposites

Posted on January 27, 2013 by

A rant is always entertaining, so here’s one.

I’m a big fan of Biffy Clyro. They grew on me with their last two albums, Puzzle and Only Revolutions. They are just about to release a double-album called Opposites, and I got the chance to listen to it prematurely, many times.

I think Opposites surpasses the last two albums in many ways. I fell in love with it at the first listen. It’s been a while since I sat through an entire album just listening and reading the lyrics. I thought it was so good that I went on the Internet looking for reviews. This is when I got pissed.

What I saw was two 3-star reviews (the Telegraph, the Guardian), and one 2-star review (the Independent). I think none of the three reviewers are rock music fans to begin with, and some of the points they make are just stupid.

The most charitable review is from Neil McCormick of the Telegraph, but even he says a few things that reveals that he is not very well equipped to appreciate Biffy’s latest album:

Biffy don’t have the swaggering adventurousness of Muse or the arty pretensions of Coldplay but they’ve certainly got something.

That may not sound too bad, but it’s just stupid to compare Biffy Clyro to Muse or Cold Play. Is that the only bands you can think of? Indeed not, as he later mentions Snow Patrol and Nirvana… Really? You can’t find any better comparison than these? How about Foo Fighters? Billy Talent? Breaking Benjamin? Even All-American Rejects, Third Eye Blind or Blink 182 make for better comparisons. Well, your post-grunge rock credentials are not that impressive sir.

Interestingly, it’s when you compare Biffy’s music to its closer genre neighbourhood that you realize how original it actually is. I listen to a lot of music and I tend to stick to the music that manages to surprise me. There are a lot of moments in Opposites that surprised the hell out of me. Sounds like Balloons is just one big surprise in itself, containing the boldest contrasts I’ve heard in the last 2 years. I find simple melodic lines like the opening phrase of Biblical so beautiful that they do surprise me, and the whole album contains tons of these. Here’s the closing phrases of Neil’s review:

The problem is it doesn’t leave you longing for more, or pull you back in to savour a favourite moment. If you’re already a Biffy Clyro fan, Opposites might be your idea of a masterpiece. If you’re new to Biffy, it’ll just give you a headache.

The first sentence is completely wrong. I’m listening to the double-album on loop right now. I can’t quit, even if the excellent new Foals album (Holy Fire) is also fighting for my attention. And Neil should have added in the second sentence that he is definitely not a Biffy Clyro fan, and not even a fan of the genre. It would have excused the 3-star review.

Alex Petridis of The Guardian wrote a less forgiving piece on Biffy’s new album, but also more interesting. He definitely tries to prove that he has better rock credentials than Neil from the Telegraph. His review however, can be boiled down to this: I’m judging the book by its cover and I’m expecting to be disappointed. And I am, but not as much as expected, so 3 stars.

I concede that the combination of the Pink Floyd-esque album cover and the double-album concept looks very pretentious. But still, the album covers for Puzzle and Only Revolutions are just as crazy-looking. I don’t see Opposites as having the pretention of being a masterpiece. It’s the author’s inability to clean the slate that’s talking.

A recurring criticism is that the album is too long. I’m pretty sure this is just because Biffy is releasing it all at once. It’s too much Biffy for what non-initiated critics can handle; they’re simply biting more than they can chew. This goes along with the criticism that it doesn’t sound varied enough:

[...] the trio have included a couple of deeply boring songs where they play things straight, sanding away their sound’s angularity to the point where they could be anyone. They’re rare lowpoints. If there’s a problem with Opposites, it’s not one of quality, so much as profusion: the impact of Biffy Clyro’s sound is gradually dulled by just how much of it there is here.

Am I the only one seeing the contradiction between the first and second part of this statement? The songs he is referring to are not low points to me, and count as genuine diversity brought in the album.

Finally, the review from The Independent is just stupid. In a pathetic reflection of the double-album concept, the review contains only two paragraphs. It looks like someone listened to the album with two ears for the first couple of tracks, decided he didn’t like it, and listened to the rest with only one ear. It says there’s little experimentation in the album, which is only half-true. Then again, here’s another critic who thinks that double-album = crazy shit.

The double-album concept seems to be confusing critics a lot. They expect the music in there to contain some world-shattering experimental concept, and they are disappointed when they don’t find it. For my part, I was only expecting some new Biffy Clyro music and I’ve been very well served. To be fair, the album does have a few weak moments, like the couple of songs in the middle. But it’s certainly not enough of a drag to lower my opinion of it. To me, Opposites is a masterpiece.

Here’s a very interesting interview with the guys from Biffy Clyro by The Guardian about Opposites.

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Holiday break project : CDER

Posted on January 21, 2013 by

CDER_logo

This post is rather technical. All you need to know is that I created a rather pretty piece of software which allows me to take a good look at the collisions we record at the ATLAS experiment. This project made me enjoy programming like never before.

Turns out I had so much momentum to kill this year after the crazy 2012 fall period that I managed to bring a complete software project to completion. Actually, this is my first ever big software project that is not directly work-related. Or at least, this is my first software project that has nothing to do with attaining specific research goals, or obtaining a passing grade in a boring computer science class.

Initially, I was looking for an excuse to enjoy programming. I found that excuse in pyglet, a python framework to create games that handles openGL graphics. I first made an Asteroids game out of it, but then I moved on to something a little more serious.

CDER (pronounced like seeder, means C-olli-DER) is the fruit of my efforts. It’s a very simple event display for particle physics events. I was looking into existing event displays for ATLAS, and they were all much too complicated and slow for what I was trying to do. I was only trying to get a feel for the meaning of some rather weird event shape variables, so I was trying to look at a lot of events with specific values of these variables.

CDER is light, so light in fact that you can spin around the events in real time and get a full grasp of their configuration in three-dimensional space. Of course, the events aren’t shown in too much details. Only very high-level objects are shown like jets, electrons, taus and missing transverse energy.

I ended up making a full project page for CDER with a wiki. CDER is technically capable of reading from any ROOT file, as long as you tell it how to access basic kinematics for high-level objects. You have to write a bit of code, but it should be very easy.

I’ll let the interested people visit the CDER website. Let me know if there are any questions. There are two known issues, the first being that pyglet will not cooperate easily with Ubuntu. Pyglet takes care of generating windows, so it has a certain amount of  platform-dependent code. The other issue is that CDER will only work in 32-bit mode for now.

Here’s an introduction video. I never made such a thing before. Don’t underestimate how much of a pain it can be to get something like that right :)

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Exolife: an interesting picture is emerging

Posted on January 17, 2013 by

Protoplanetary disk (NASA).

There have a been a number of interesting articles coming out recently about alien solar systems. When you consider three articles in particular, the sense that the conditions necessary for life are widespread in our own galaxy gets very strong. The three articles I am talking about are:

Once again, astronomy is revealing how litte special we are. We first thought the Earth was flat and made the entire Universe. Then, we thought the Earth was at the core of some vast space containing the sun, the moon and the planets. Then, we learned the Earth circumnavigates an astral body immensely more impressive than the Earth itself, on which all life on Earth depends. Then, we learned that this sun is one among many, a small dot in a galaxy of stars. We eventually learned that galaxies are also incredibly abundant, and that the Universe is vast way beyond imagination.

One of the last hiding place for our ego was the special configuration of our solar system. Now that we are gathering more and more data on other star systems, we are discovering that our solar system is not so special after all. Here is the thing that strikes me the most about these 3 articles.

It is an interesting fact of our solar system that with the exception of the Earth, the inner solar system is exceedingly dry. This can easily be explained by looking at the history of the formation of the solar system, according to the nebular hypothesis.

In the nebular hypothesis, planets are a natural result of star formation. You have a large cloud of gases and dust which starts collapsing under its own gravity. Eventually, matter piles up more at one particular point, creating an agglomeration of hydrogen so dense that it starts a reaction of nuclear fusion. The star is born, and it warms up the rest of the gases and dust surrounding it.

Of course, the closer you get to the star, the warmer it becomes. Close to the sun, gases like water vapour will remain in gaseous form and will not be able to condense. Beyond a certain distance from the star which is called the snow line, it gets colder and water vapour condenses and agglomerates. If you ever wondered where that cloud of comets and all those icy moons orbiting the gas giants came from, ask no more. It’s simply water that is given the freedom to agglomerate beyond the snow line, and there can be a lot of water in a forming solar system.

So what happens inside the snow line? The sun does not only warm up its proximity, it bombards it with light and other particles, which we call the solar wind. Gases like water vapour that do not manage to agglomerate are pushed away, beyond the snow line. According to this model, the inner solar system should be entirely dry. So why is there so much water on Earth?

The leading hypothesis is that comets placed on funny orbits eventually brought that water back into the inner solar system. Venus eventually lost all its water, poisoned by heavy gases that caused a runaway greenhouse effect. Most of the water of Mars was also lost, although large quantities remained, frozen. The Earth’s story is obviously different, and the reasons for this are numerous. But the point is, if you have comets, you can bring back water in the Goldilocks zone where rocky planets can have water in liquid form for long periods of time.

And now this is also possible with moons of gas giants, making even more solar systems potentially habitable. It looks pretty clear to me from the current science that the astronomical conditions necessary for the emergence of life are easily met in our galaxy. These conditions might happen with an astonishing frequency. We are even less special than we thought.

Is there life elsewhere in the Universe? This is one of the deeper questions driven by pure human curiosity that is in the process of being answered by science. We are investigating the specifics of that question which are well illustrated by the Drake equation. Now, it seems like the focus is shifting away from astronomy to biology. The big mystery of whether other planets can harbour life is being answered. It’s just a matter of time before we have telescopes powerful enough to inspect the atmospheres of rocky exoplanets. The deeper mysteries now are the emergence of life and the evolution of complex life. There are a few places for our ego to hide, but they are going away. They are going away fast, and a Universe that leaves our ego in the dust turns out to be extremely fascinating.

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Asteroids

Posted on December 8, 2012 by

Don’t ask me how I choose my priorities in life. I just don’t know. All I know is that my work at ATLAS is the top priority most of the time. But every once in a while, I just get sick of all the responsibilities, the politics and the professionalism of it all, and I indulge myself in some creative endeavour. I love what I do in ATLAS, I love the collaboration. In fact, I’m really proud to be part of it. But I am an emotional being that needs to experience a full spectrum of emotions to stay balanced and happy. What fulfills me more  than anything else is to create things. I do create things in my work, but these creations take so much time to complete and share that I don’t experience the satisfaction of achieving results very often. Achieving results is my drug. And nothing gives me satisfying results faster than art.

For the past 3 weeks, I have been learning to use pyglet, py-lepton and by consequence OpenGL. I have been following this fantastic tutorial to create an Asteroids game, and I have been expanding on the tutorial for 2 weeks now. I have a fairly mature game, and today I worked on adding sound effects. I started fiddling around to make a simple background music track, and I got carried away…

I am working with Logic Pro 9 to make my music. What I haven’t really explored before are the extensive sound libraries that come with the software. I have mostly been recording my own instruments in the past. So you can imagine my surprise when after two hours, I came up with something in a style I have never done before, that sounds more professional that anything I’ve done before. Naturally, I call the track Asteroids.

Here are a few screenshots from the game. I don’t know if I will be able to distribute this at some point. Distributing python games is not easy, but possible. If I get a creative commons license for it, then I can distribute the source code… I’ll think about it.

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What to make of the HCP ATLAS and CMS Higgs results

Posted on November 22, 2012 by

Kyoto, where HCP was held. Via Wikipedia.

The HCP conference that ended about a week ago turned out to be a bit disappointing/unsettling. Just before I start, let me say that all that follows here is my own opinion: it has absolutely nothing to do with the stance of the ATLAS collaboration on anything. Of course, being part of the collaboration myself, I do have inside information. But I assure you that what is being written here could easily have been written by someone without that information. This is the only thing that I can and should do, because any finding that hasn’t made it outside the collaboration hasn’t been thoroughly checked yet. I cannot be certain of anything that hasn’t passed the rigorous verification of our editorial board, just like someone outside the collaboration.

In any case, here’s what went down at HCP concerning the Higgs boson. Both ATLAS and CMS did present new results for one specific mode of decay of the Higgs boson: Higgs to two taus. ATLAS didn’t manage to update their own ditau result back in July, but CMS did. Interestingly, CMS had a change of heart for their ditau analysis: they changed the method and ended up with very little improvement in sensitivity with respect to their July result, despite several technical improvements and some more data. They haven’t been very open on exactly why that is, and the credibility of their result from July have been called into question.

The new ATLAS result presented at HCP is quite comparable to the new CMS result for the ditau search. It is just a little bit less sensitive. Both experiments are not able to exclude the existence of the ditau decay for the new Higgs-like particle, but they are not able to confirm it exists either despite seeing a small excess.

I have to admit to a bit of schadenfreude towards the situation. I’m particularly happy to know that ATLAS isn’t so far behind in the search for pairs of taus coming from Higgs bosons. We can catch up with CMS for the next conference.

I may have made that point before, but observing a new decay mode for the new Higgs-like particle is a big deal. That means we have a new handle to characterize it, and we can learn more about its interactions with other particles. This is a crucial step in establishing if the particle actually is the Higgs boson.

Now, there are three decay modes that have been observed: two photons, two Z bosons and two W bosons. The diphoton result leads the sensitivity and the mass measurement in both collaborations. The ZZ result also provides a good mass resolution, but that decay mode is more rare. The WW decay mode doesn’t have a good mass resolution because of neutrinos in the decays of the W bosons. It is however, quite abundant and can provide polarization measurements. I should mention that the simplest analyses are the diphoton search and the ZZ search, especially when both Z decay to pairs of light leptons. By light leptons, I mean electrons and muons. Electrons and muons are really easy to reconstruct in the detector (compared to other objects like taus for example), so ZZ to four light leptons is the easiest way to look for that particular decay mode.

What is a bit weird is that neither ATLAS or CMS have updated their diphoton result, and only CMS updated their ZZ result. Given that these are the easiest analyses to update, why haven’t they been updated? There are several possible answers. The first is that the groups doing these analyses have made a radical change in methodology and they haven’t manage to iron out everything on time. It is also possible that they see something suspicious that they can’t quite explain. The first case would probably mean that the next results for these analyses are going to see strong improvement in sensitivity, while the second case may result in either a very exciting outcome or a very boring one.

This is very little to go on though. I don’t want to start rumours. It seems that every time the Internet gets excited about a new scientific announcement, the story ends up in harsh disappointment. Remember the arsenic-based lifeforms? Or the faster-than-light neutrinos? And now there’s the Curiosity rumour? Curb your enthusiasm Internet. I know you are quite young, but you will grow to be a very bitter adult if you don’t stop reading too much into things.

Of course, I really should mention, if only briefly, that there was one very exciting result presented at HCP. LHCb observed a really rare b-meson decay for the first time, and it turns out that this decay is produced just the right amount to be compatible with the Standard Model and incompatible with supersymmetry. This is a big deal, and I will try to talk about it more in a future post.

I know that some people think that the most exciting part is over with the new particle being discovered at the LHC. But what I am trying to say in this post is that it is truly only the beginning. It is worth staying excited about it. We are learning about the most fundamental aspects of the Universe, and no one on Earth before us has ever been able to claim to know these things. Not getting too excited and staying rational when finding unexpected things is part of the process that led us here. It is only then that we can assert the reality of these unexpected things. Let’s keep it up, and let’s try to make it a more common human trait.

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