Large Hadron Collider provides 1 inverse femtobarn for CMS and ATLAS, already!

June 13, 2011

Today at 21:10 hours European Time the Large Hadron Collider passed an important milestone when it reached 1/fb of integrated luminosity delivered to each of the large experiments CMS and ATLAS. The third major proton experiment LHCb which limits its luminosity has around 0.35/fb. These figures include the 47/pb delivered in 2010, but after another one or two good runs the total for 2011 alone will also surpass the one inverse femtobarn milestone.

Update 14-Jun-2011: With another good run today the total delivered for CMS passed the 1/fb mark for 2011 data alone at about 20:25.

This is an impressive achievement for the worlds most powerful particle accelerator at CERN which had originally expected to collect this amount of data only by the end of 2011. Better than expected performance now means that it records about 30/pb worth of collision data each day on average. With about 120 days of proton physics left this year, the beam operations team can expect to deliver at least 4.4/fb this year if they continue at this rate.

Potential luminosity increases

There is still some potential to increase this figure if they can continue to increase the number of protons circulating in the rings. The current quantity of 1092 proton bunches circulating in each direction will shortly be increased to 1236 and then finally 1380 once they overcome difficulties with power to the RF systems. This will increase the luminsity by 25%. Another goal will be to increase the efficiency by keeping the collider in Stable Beams for longer. Recent figures show that this state is only achieved for around 40% of the time due to a variety of technical issues. As these are sorted the figure may go up to 60% or even higher to give 50% more data. If this can be done quickly it would bring the expected total for 2011 up to around 7/fb. At 1380 bunches the rings are full to capacity with current bunch spacing so further improvements this year are only possible if the bunch intensity can also be increased, but this is not yet planned. 5/fb to 7/fb is already a spectacular number to aim for and they may not want to put these numbers in danger by taking such risks.

Expected conference announcements

The amounts of useful data recorded by the experiments is typically 90% to 95% of the amounts delivered. In a few days these figures will also pass 1/fb and this should be in time for the next big particle physics conference EPS-HEP2011 at the end of July. At last weeks PLHC2011 conference we already saw a few results using 200/pb, one fifth of the current standing. However, there are many standard searches for which we have still only seen plots using the 40/pb collected last year. For example the classic dimuon resonance curve has not yet been shown in updated form for either ATLAS or CMS. This could be because it was too dull to show. The dimuon signal is very clean but it is not expected to be the first place where new physics will appear. On the other hand, it may not have been shown for the opposite reason. If it had an inconclusive signal of a new resonance then they would surely want to wait for more data before showing it.

When will the Higgs be seen?

To get a better impression of just how significant the quantities of data now being collected are, it is useful to look at the projected Higgs Limits as shown in this figure.

With 1/fb of data there will either be a signal or an exclusion for the Higgs boson above 130 GeV. If it is excluded then it will be known to lie between the 115 GeV limit previously set by LEP and a new limit of 130 GeV. This is highly significant because the standard model on its own predicts that the vacuum would be unstable if the Higgs has a mass less than 135 GeV. New particles such as those predicted by supersymmetry would be needed to restore stability. In other words, this exclusion expected from 1/fb would be indirect evidence of physics beyond the standard model at the electro-weak scale. The EPS-HEP conference is likely to be a historic event where they will either describe the first signals for the Higgs Boson or the first good evidence for new BSM physics. If you want to attend today is the last day to register at the standard fee or 350 Euro!

If EPS-HEP is an anti-climax, the next big particle physics conference is Lepton-Photon 2011 during the last week of August. Another femtobarn of data will be available for analysis in time for that. There are smaller workshops and seminar opportunities going on all the time so a new discovery can come at any moment, but the physicists do like to time their results for these big events.

By the end of the year the situation will be even more dramatic. About 5/fb should be available, enough to exclude the Higgs boson at all masses, or more likely to discover it. If it is indeed a light Higgs there is a good chance that some other new particles will be discovered too.

What if it does not show up?

The calculations that are used to calculate the exclusion limits are themselves based on assumptions that the Higgs will decay according to the predictions of the standard model. If the standard model is ruled out by not seeing the Higgs then these calculations will themselves be invalid. For example, a possibility is that there are heavy unknown particles into which the Higgs could decay. If these new particles produce jets that are hidden in the sea of background QCD it may be much harder to detect it. Another even weirder possibility is that the Higgs boson just isn’t there. If nature is devious enough we could still see no new particles this year.

Wednesday Eclipse of Moon on Live Webcam

June 13, 2011

On 15th June 2011 you can watch a total eclipse of the moon. Total lunar eclipses are not very rare, they come on average once a year, but this one is exceptionally long. Firstly,  the moon will pass through the centre of the Earth’s shadow which last happened about 11 years ago, but also because the sun is more distant at this time of year and the Earth is a little closer to the moon. This makes the Sun look smaller and the Earth look bigger from the moon’s surface. In fact the eclipse will be total for 1 hour and 41 minutes. That is only five minutes short of the longest possible.

The Eclipse will be visible over most of Asia, Africa, Europe, Australia and South America, leaving only North America and a few other corners of the world with no chance to see it. About 90% of the world’s population can view at least part of it directly, weather permitting. For the rest the internet saves the day with some live webcasts of the event. So far three organisations are planning webcasts so it is unlikely that they will all be clouded out.

Sky Watchers Association of North Bengal: here or here

Eclipse Chaser Athaenium New Delhi: here here

Google/Slooh: here

From first contact to last, the eclipse is visible from 17:23 to 23:02 GMT on Wednesday

D0 sees no bump

June 10, 2011

Sadly the D0 experiment sees no bump in boson+dijet at Fermilab, dismissing the 4.1 sigma result of CDF.

This has already been reported here, here, here, and here. The original paper is here.

Now the two experiments need to get together to work out which is wrong and why. It is not a sure conclusion that D0 is right but it seems more likely that someone would see an effect that isn’t there by mistake than that someone would fail to see an effect that is there. This gives D0 a strong psychological advantage.

To find out what went wrong they have to compare the raw plots and the background as seen in these plots

The differences are too subtle to see from just the visual image, and it does not help that they used different bins. There does appear to be significant differences in the backgrounds while the data look quite similar. If that is the case then the problem is purely theoretical and they just need to compare their background calculations. However, the detectors are different so perhaps the backgrounds should not look exactly the same. Only the people directly involved have enough details to get to the bottom of it.

I hope they will work it out and let us know because it would be nice to see that their understanding of their results can be improved to give better confidence in any similar future results.

By the way, you can still vote for us on 3QuarksDaily

Another LHC Update

June 9, 2011

For the past 11 days the Large Hadron Collider has been running with a 1092 bunch filling scheme adding 325/pb to the total data delivered. Based on an average peak luminosity of 1.13/nb/s this gives a Hübner Factor of 0.3 which is very respectable for this early stage of the run.

During this time the beams have been dumped frequently by problems such as software errors that are being rapidly fixed. UFOs have been another major headache. These are thought to be dust particles that fall into the beam. There is so far no sign of their numbers dropping as the beam zaps them up, but the dump thresholds can be changed in the worst hit areas to reduce the number of UFOs that cause a run to be aborted. This means that overall the run efficiency should improve and the expectation should be for a somewhat better Hübner Factor once they settle into the longer run.

The first successful fill with 144 bunch injection ran last night. The longer train length means a few more bunches can be fitted into the ring. They just need two long fills with this filling scheme before they can step up to 1226 bunches in each beam, so higher luminosities should be with us soon.

The schedule for the rest of the year has been modified to replace the four planned maintenance breaks with just three breaks, but slightly longer in duration. The immediate effect is that the next stop moves back from 16th June to 29th June, allowing more data to be collected in time for the big HEP-EPS conference at the end of July.

This week it has been the Physics at LHC conference in Perugia that has been grabbing most attention. There have already been some new limits shown, such as seen on these plots from a talk today on ATLAS top physics by Marina Cobal.

The talks on the final day tomorrow are the ones most likely to declare any new observations rather than just exclusions using the 240/pb on offer. Indications from conference notes already released suggest that we should not expect too much. A lot of the talks have not explored beyond the 40/pb dataset from 2010.

A pessimist would say that they have concentrated on the best-hope channels for presentations at this conference so the absence of new observations beyond the standard model here means that nothing new is showing up yet. An optimist, however, might say that they have only been able to approve the less interesting searches in the time available. All the best results may be in the places where no new data was shown this week because they will want to wait a little longer for more data to get conclusive results. We wont have long to wait until the EPS-HEP conference where 1000/pb of data should be on the table.

Meanwhile the main buzz is about the CDF bump at 150 GeV. Tomorrow there should be a seminar at Fermilab from the D0 group to tell us whether or not they also see the bump. It will be webcast here. Another version of the talk will be seen at PLHC on Saturday. Woit has already passed on a rumour that says the answer will be negative. Even if he is right, this will leave open the question of how the bump seen by CDF can be explained. The results should be consistent so the two groups will need to compare their analysis methods to find out what went wrong.

Update 9-Jun-2011: I have checked all of the talks at PLHC 2011. There are 10 talks from ATLAS and one from CMS where new searches using 2011 data up to 236/pb are presented. They all correspond to notes already published last week so we know that only new exclusions limits are found. No new physics is forthcoming this week from the LHC, unless they slip in an extra last minute talk.

Don’t Say I Didn’t Warn You

June 8, 2011

Just so you have some advanced warning of predictable events that are likely to feature on this blog, I have added a Science Calendar at the bottom of the right hand column. Suggestions for additions are welcome, but may be ignored.

Best science blog post?

June 7, 2011

viXra Log is nominated for best science blog post at 3QuarksDaily. Voting end tomorrow.

Update: Currently in about 28th position, needing to be in top 20 to make final round.

Update: We didn’t quite make the cut but thanks for all the votes, I think we were about 28th position out of 70

Shaw Prizes for Enrico Costa, Gerald Fishman, Jules Hoffmann, Ruslan Medzhitov, Bruce Beutler, Demetrios Christodoulou and Richard Hamilton

June 7, 2011

Today seven scientists are up to $500,000 minus tax richer for having won this years Shaw Prizes.


First up are Enrico Costa and Gerald J Fishman for leading the NASA mission that resolved the origin of gamma ray bursts. It does not seem to many years ago since gamma-ray bursts were regarded as one of the great unsolved mysteries of science. They had first been detected in 1967 by the Vela satellites which had been placed in orbit by the US military to check that the USSR was not detonating nuclear weapons in contravention of the 1963 partial test ban treaty. Nuclear explosions would send gamma rays into space where the satellites would detect them. Instead they observed gamma ray bursts coming from space.

From 1973 when their existence was declassified until 1997, these events were so mysterious that astronomers could not even tell if they came from nearby in our galaxy or billions of years away across the universe. NASA launched the BeppoSAX satellite to try to resolve the question, In 1997 it observed a powerful gamma ray burst which left an afterglow long enough for Earth based telescopes to lock onto its location just 8 hours later. Now they could see that it came from a very distant galaxy.

The gamma rays are so bright at that distance that it is inconceivable that they are being radiated equally in all directions in such a short space of time. The amount of energy that would have to be concentrated into a small volume is juts not possible. It is thought that they come from energetic supernovae with a rapidly rotating remnant that focuses the gamma rays into a tight beam. we only see the burst for the small fraction of events where we happen to lie in the direction of the ray.

Life Science and Medicine

Next were Jules A Hoffmann, Ruslan M Medzhitov and Bruce Beutler for uncovering the biological mechanisms for innate immunity. When an animal or plant is infected it deploys a number of mechanisms to defend itself. One of the first is the innate immune system, thought to be one of the earliest mechanisms to evolve because it is so widespread across diverse forms of life. In plants it remains the dominant immune system, but advanced animals have developed more effective systems of adaptive immunity that can change to attack specific viruses or other contagents.

Understanding all forms of immunity is vital to medicine because it provides the knowledge needed to find drugs that help us fight diseases.


Finally, Demetrios Christodoulou and Richard S Hamilton won the mathematics prize for work on differential manifolds with implications for general relativity and the Poincaré conjecture.

When Grigori Perelman famously turned down the Fields medal and the million dollar Clay prize for resolving the Poincaré conjecture, he said that his reason was that other mathematicians such as Richard Hamilton has contributed just as much to the proof. He need not have been so concerned since Hamilton has now himself been recognized with a lucrative award.

It was Hamilton who discovered the theory of Ricci flow on differential manifolds that lead Perelman to his proof of the Thurston geometrization conjecture that was known to imply the truth of the Poincaré conjecture, a mathematical problem that had remained unsolved for a hundred years.

Demetrios Christodoulou is a mathematical physicist who worked for his doctorate at Princeton under the direction of John Wheeler. He is known for his extraordinarily difficult proof of the unsurprising fact that flat empty Minkowski space is stable under the action of nonlinear gravitational dynamics as described by general relativity.


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