Monday, June 25, 2012

The Higgs: To be, or not to be?

[Note from Shaun: The following is a guest post from Higgs Hunter, Mikko Voutilainen. Mikko is a colleague of mine here in Helsinki. He is a postdoc working on the CMS experiment at the LHC in CERN. Below, he rhetorically asks the Higgs boson whether it exists or not. The irony of this is that Mikko asks this question, non-rhetorically, for a living and it is quite possible that he has already received an answer. He cannot (unfortunately) tell us this answer, yet. You should consider the following a teaser for what will follow next Wednesday when CERN unveils its latest results to the world. On that date, Mikko has promised to give us another guest post where he will reveal everything he knows about, The Higgs... (I've even heard rumours that this follow-up post has already been written)]

To be, or not to be?

That's a question for the Higgs boson to answer, and we might know soon enough. CERN just (well, three days ago really, but everybody here was out in the countryside celebrating Midsummer) published a press release about having a seminar on the new results on Wednesday 4th of July.

Coincidence that it's also Independence Day for the folks in the US? Probably yes, although my collaboration, the Compact Muon Solenoid (CMS) experiment at CERN, does have a strong representation from the States, including our spokesperson Joe Incandela.

The real reason, though, is that the 4th of July is also the eve of a major particle physics conference, ICHEP, starting in Melbourne. The ATLAS and CMS experiments will deliver the preliminary results of their 2012 data analysis there, and the seminar will be a kickoff for these presentations (you can see the live broadcast at

The experiments at the Large Hadron Collider stopped collecting data only on the 18th of June, and everybody is now busily analysing this dataset. We actually collected quite a nice bunch of data, just over 6/fb, which is a bit better than last year. The collision energy was also raised from 7 TeV to 8 TeV, which should increase the production rate of possible Higgs bosons by 20--30%.

The amount of data collected in 2010, 2011 and 2012. One fb-1 amounts to almost 100 trillion proton-proton collisions.

People are really eager to see the new results, and for a reason. The data collected in 2011 showed some hints of a Higgs boson in the 124-126 GeV range. The amount of data collected this year is nearly equal to that collected last year so the results are directly comparable. We should be able to see whether the earlier trends are still there, or whether they've gone away. Either way, it should be pretty exciting.

The predictions made earlier indicate that a combination of the 2011 and 2012 datasets should get pretty close to five sigma, the traditional standard for a discovery in the field. Or, we should be able to rule the existence of the Higgs boson out at a 95% confidence level from the whole remaining mass window.

Predictions for the significance of a Higgs signal as a function of the boson mass. The combination of 2011 (5 fb-1, 7 TeV) and 2012 (5 fb-1, 8 TeV) data will correspond to roughly the average of the two red lines.

What happens in a week depends both on the hard work of the physicists, who are improving the sensitivity of their analysis, and, due to statistical fluctuations, pure luck. If we're unlucky, the existence of the Higgs boson may still remain a mystery, but if we're lucky, we might end the quest earlier than expected.

So, what if we find the Higgs or not? Is it the answer to Life, the Universe, and Everything? Or a piece in the puzzle of the origin of mass for the elementary particles? The latter, more likely.

If we find that the Higgs boson lacks existence, much of the theoretical work done in particle physics for the past few decades will end up in the dustbin. It's not all that bad, really, because it will allow the theorists to start from a clean slate, and that's often been a very fruitful thing. The experimentalists will continue to hunt for other particles that could replace the Higgs boson.

If the Higgs boson is found, it's properties will have to be scrutinized carefully. There are many theories out there besides the Standard Model of particle physics that predict the Higgs boson (or bosons) so determining it's precise identity might take a while. Many of the alternative theories also predict other particles, leaving plenty of work to be done for the experimentalists.

[Note: Mikko writes for a Finnish language blog, Higgs Hunters. This post is an English translation of his latest post at Higgs Hunters.]

Monday, June 18, 2012

The human machine: pistons and ratchets

The previous post in this series can be found here.

In my last post I talked about how we are all powered by tiny spinning motors that work tirelessly to convert the chemical energy of our food into electrical potential energy, and then back into chemical energy in the form of the cellular energy currency, ATP . This week, I thought it would be interesting to look at how that ATP gets used up in a process that will be very familiar to you but that you probably know little about: muscle contraction.

As I mentioned last time, ATP is used by just about every active process that takes place in your cells. Most of these processes siphon only tiny amounts of ATP from the ever-replenished pool that is available in your cells – as far as they’re concerned there is an infinite amount of ATP available because they could never use is all up on their own. For this reason, a lot of our cellular machinery is, frankly, wasteful. The mechanisms that regulate DNA repair, movement of organelles within cells, and many other processes consume ATP with gay abandon because their impact is so miniscule on the total energy consumed by your body as a whole. There has been no need to evolve more cost-efficient mechanisms, such as those employed by our single-celled relatives for whom every ATP counts!

For some components of the human machine, however, their impact on total ATP consumption is far from insignificant. One often overlooked example is neural transmission, which is why the brain consumes around 20% of your total calories on an average day, and why you may find yourself famished after a tough exam even though you’ve just been sat down for three hours! Nonetheless, the clear winner in the ATP-expenditure competition is muscle contraction. Your muscles are responsible for using nearly 60% of your total calories on an average day – potentially far more if you’re very active (or very muscular!). Motile animals have to consume far more energy to survive than non-motile animals or plants, and this is primarily down to their muscles. Fortunately, this is very much worth it because being able to move gives you far broader options in terms of finding food in the first place. Moreover, because of its huge significance in terms of total energy consumption, the molecular basis of muscle contraction has evolved to be a highly efficient affair. In fact, in terms of work achieved per ATP used, muscle contraction is one of the most efficient processes in your body – it’s simply the fact that it’s used on a huge scale that makes it such an ATP-hungry mechanism. 

Monday, June 11, 2012

3 Quarks Daily's science writing prize. (Vote for us)

I nominated my favourite of James' posts (The War of the Immune Worlds) for the science writing prize at 3 Quarks Daily. If you want to support the blog, it would be great if you would go and vote for it!

To vote, click this link, scroll down to "The Trenches of Discovery" and click away! 

If you're super cool, you'll also try to convince your friends and family to vote for James' post. This first round will basically be a popularity contest. There are 100 odd entries and nobody is going to read them all. The top 20 in this round go through to the next round where the 3 Quarks Daily editors actually read and vote on every entry. So, by helping James' post get to this next round you help us to compete against the bigger, more established blogs who've been around much longer than us.

In any case, it is actually a really cool post, so, while you'll clearly be doing us a favour by sharing this post with others, you'll also be doing a favour to anyone who ends up reading it too. In that vein, if you haven't read the post yet yourself, go check it out, it's really cool.

Voting closes June 15 so vote now!

Monday, June 4, 2012

The 2012 Transit of Venus

David Peck Todd, photograph of the 1882 Transit of Venus
 The last Transit of Venus of the 21st century will happen in the coming days, June 5 or 6, 2012, depending on where you are in the world. This is a phenomena in which Venus passes directly between Earth and the Sun, and is observable as a small black dot gliding over the face of the Sun over a six hour period. Transits occur in pairs separated by 8 years (2004/2012) followed by gap of about 110 years (the next one is in December 11, 2117!). Only six have been observed since the invention of the telescope:
  • 1631 (not witnessed) & 1639
  • 1761 & 1769
  • 1874 & 1882
  • 2004 & 2012
Those dates provide some sense of historical scale involved in this phenomena, which is partly the point I'm getting to ...  The Transit of Venus has been a historically significant astronomical event because alignment of the Sun, the Earth, and Venus has allowed astronomers to calculate distances between the Earth and the Sun, and from that to estimate the scale of the solar system. As this blog post by Karen Masters, an astronomer, explains: 
Basically when Venus crosses the Sun we know that [Venus], the Sun and the Earth are all in a straight line. Very slight differences in the viewing angle from two observers on the Earth can then be used along with our basic knowledge of trigometry to measure the distance to the Sun. For over 100 years, the distance to the Sun measured this way was the most accurate measurement we had.