Analysis of Tevatron Data Favors Low-Mass Higgs Boson; Confirms LHC Observations

A full analysis of the Tevatron data collected over ten years – a mind boggling 500 trillion proton-antiproton collision events – yields a narrower range for the Higgs mass. A new statistical fluctuation, seen with a confidence level of 2.2 sigma, narrows the range of the particle causing the fluctuation to between 115 GeV to 135 GeV. A GeV is a Giga electron Volts or a billion electron volts. These are pretty strong bounds on the mass. Furthermore, the entire regions between 147 to 179 GeV can be safely eliminated. This analysis confirms what the LHC data says – the Higgs is a low mass Higgs with a mass of about 125-126 GeV and the mass range above 141 GeV is eliminated with 95% confidence.

The local significances of the Higgs signature, both from the LHC and the Tevatron. Notice the continuous black line rising way above the dotted black line within the 115 to 127 GeV range. The horizontal light across the graph is the Standard Model prediction probability. The actual observed probability has to be greater than this line.

Excluded ranges and the range to look out for

The data, collected from CDF and DZero detectors of the now-deceased Tevatron, combines well with the LHC data, specifically with that supplied by the ATLAS detector, to restrict the Higgs mass between 115 GeV and 129 GeV. This also provides more confidence to the 3.6 sigma peak announced during the 13th December 2011 CERN broadcast. Kindly check the link here for very specific details of the seminar:

However, this result shows that the LHC and the Tevatron results match and that’s great, but it doesn’t get us any closer to actually finding the Higgs. Of course, if the Tevatron had disagreed, then we would’ve been in serious trouble.

Bottom line

Two things come out of this confirmation: The Higgs is most probably a low mass Higgs, having a mass of about 125-126 GeV. This is pretty interesting in itself, since this is not just the boring Standard Model Higgs, but gives an inkling of the success of supersymmetric theories. Secondly, the “look elsewhere” effect may not be as significant as was previously thought, now that the bounds are tighter. The “look elsewhere effect” takes into account the probability of finding the Higgs at every point within a certain range and not just at a very small interval. This considerably reduces the significance of the observed bump in general. Since the “look elsewhere effect” may decrease its contribution, concentrating on local significances may be quite the right thing to do!

Of course, the game will only be decided by the LHC. We expect to have enough data to pinpoint the Higgs by the end of this year, before the LHC goes into hibernation for 15 months. The game is heating up and getting interesting. Stay tuned…

With Upgrades, LHC Will Be More Energetic And Be Able To Handle More Collisions

The LHC is taking a vacation right now, but it promise to return with a bang! The LHC is due to run very soon, but instead of the usual 7 TeV (1TeV = 1 Trillion electron volts) total energy, it will try and go a bit higher and reach 8 TeV. Also the luminosity (basically number of collisions per second) will increase, but the increase won’t be substantial and there are reasons for that. Physicists promise enough data to pinpoint the Higgs and to verify the tantalizing 125 GeV peak that was reported earlier(here). Furthermore, after a packed 2012 schedule, the LHC will hibernate for a longer time and will wake up in 2014. During this time, the LHC will be fitted with newer instruments.

More work: ATLAS detector


The hardware upgrade will have to wait till end of 2012, when the LHC will shut down for an extended period of 14 months, waking up again in 2014. The hardware upgrade will allow the LHC to run at a huge energy of 14 TeV and much higher luminosity. This is crucial, since it is not only the energy, but the number of collisions that makes a lot of difference in the experimental data. More luminosity means lower uncertainty in the measured values. The current electronics won’t be able to handle the rate of data acquisition that the LHC is planning to achieve.

Higher luminosity

The LHC currently runs at 3.5 TeV per beam, giving 7 TeV on a two-beam collision. They plan to upgrade it to 4 TeV per beam, giving a total energy of 8 TeV. Each beam of protons is made up of bunches of protons, with each bunch being separated by a certain amount of time. Each bunch has a certain number of protons. The team will also look to increase the number of protons per bunch, but keep the number of bunches constant, thereby increasing the luminosity. The current bunch spacing is 50 nanoseconds. The LHC electronics is built so as to handle bunches separated by 25 ns. The LHC team might look at this small deadtime when it resumes in 2014.

All in all, the full blown search for Higgs might end soon, but the LHC is poised for more daring adventures!

Faster-Than-Light Results Debunked by Computer Glitch? Hold On, Not So Fast!

The neutrino story is still not an open and shut case. You’ve probably read about the supposed computer glitch by now. If you haven’t, we have it right here. However, as more details pour in, more surprises tumble out! It turns out that there wasn’t just one computer error, there were, in fact, two!! And this complicates matters

Twin Glitches

Error #1

New York Times reports that one source of error is the GPS measurement system, or more precisely, the optical cable connecting the GPS receiver to the detector. This is a five mile long cable and the faulty wiring could’ve easily put the measurements back by 60 nanoseconds, which was the exact amount of time by which the neutrinos beat the speed of light. This is the story we reported earlier.

Error #2

However, it seems that there was yet another unaccounted systematic error! There is a piece of equipment that marks the exact time for the GPS measurements, taking into account all sorts of relativistic corrections.

However, this would speed up the neutrinos even more, making the case for the violation of relativity even stronger.

The first error has been corrected, but the second error is yet to be taken care of.

Add and subtract the errors? No? What’s wrong?

As any student of physics would know, errors like these cannot simply be added or subtracted. For extreme precision experiments, like the OPERA  experiment, one cannot tweak the experimental data in order to do take into account all technical glitches. The only way to resolve this would be to fix the systematics and run the experiment again!

The experiment would definitely need an independent test to be refuted, now more than ever, since these unexpected question marks have been put up against it.

BREAKING NEWS: Simple Computer Glitch To Blame For Faster-Than-Light Neutrino Results

The supposedly greatest anomaly ever detected in physics, capable of undoing a hundred years of physics, may turn out to be a mere computer glitch. There are rumours that the anomaly may be due to a faulty connection between a GPS unit and a computer receiving signals from it.

We had reported the faster-than-light neutrino results in great detail in several posts earlier. The physics group at Gran Sasso laboratory, near CERN, had detected that neutrinos arrives 60 nanoseconds before they are expected to, if they travelled at light speed. This means that they travelled faster than light, violating the cosmic speed limit imposed by Einstein’s Special Theory of Relativity, by a factor of full one-ten thousandth, which is a huge number when it comes to Lorentz violations.

The rumour is that sources inside Gran Sasso say that when a connection between a GPS receiver and the optic fibre was adjusted, the time of flight comes out exactly 60 seconds longer than measured, exactly cancelling the seen anomaly.

New data from independent experiments is still needed to confirm the non-violation of the cosmic speed limit. If this rumour is true, it is face-saving time for the Gran Sasso scientists.

Higgs Search Becomes More Promising With More Data Analysis; CERN Increases Confidence Level

The Higgs search gets hotter and hotter. Recent analysis of old data have raised the confidence level of the Higgs detection from the older value of 3.8-sigma overall to a much healthier 4.3-sigma, as indicated by the two papers sent for publication, one by CMS and the other by ATLAS. The Compact Muon Solenoid (CMS) detector group had given the confidence level of 2.5-sigma. Now, with the analysis of more data, they have pushed it up to 3.1-sigma. Remember that a 5-sigma confidence level is what you need for tagging something as a discovery – so 4.3-sigma, though exciting, is not momentous.

A Higgs simulation at CMS

There – but not quite there

The results overwhelmingly predict a Higgs mass in the range of 124-126 GeV, which is exactly what scientists had reported on December 13th.

A 5-sigma means that one is 99.99997% sure, while a 4.3-sigma result means that scientists are 99.996% sure that the identified peak is the Higgs peak.

Just a joke!

This is just an improvement over the ‘initial’ December announcements by CERN. The data is not new, since the LHC hasn’t been taking any since November, but a more thorough analysis has been done and this is what it says. I suspect that this is as far as CERN can go at the moment with the Higgs confidence levels, and they will require much more data to be completely sure.

The 3.8-sigma confidence levels shouldn’t be taken too seriously. There have been peaks of this confidence level, but they had vanished. Fortunately, this hasn’t.

A new chapter

We should have to wait another year or so before the LHC can give something definite on the Higgs search. Now that the LHC is temporarily closed down for mandatory maintenance efforts, the big bosses, meeting at Charminox, France, are discussing the energy and the luminosity it will be tuned to when it opens later this year. The scale up to 8 TeV in energy is expected, but the luminosity is not yet revealed.

Don’t Blink: Physicists Break Data Network Speed Record at 186Gbps

High-energy physicists have pushed the limits of network data transfer to mind boggling speeds. Researchers attending the Super Computing 2011 conference, held in Seattle Convention Center, transferred data in opposite directions to eventually reach a combined rate of 186Gbps over a Wide Area Network. For those of you not quite familiar with the terminology, a Wide Area Network is typically defined as a network that is separated by long geographic distances such as, between a main office and a branch office in another state. The typical Wide Area Network usually ranges from 1.54Mbps T1 or DSL connections to 10Mbps fiber or cable. As you can see, 186Gbps speeds blows the standard network speeds away.

The small team of researchers consisted of members from Caltech and University of Victoria. In  the first demonstration the team transferred data from hard disks located at University of Victoria down to the show room floor at more than 60Gbps. This is thought to be a record all its own, but then they transferred data from memory to memory at 98Gbps. They were able to sustain this transfer reaching bidirectional speeds of 186Gbps.  University of Victoria Professor and LHC physicist Randall Sobie said:

The 100Gb/s demo at SC11 is pushing the limits of network technology by  showing that it is possible to transfer peta-scale particle physics data sample in a  matter of hours to anywhere around the world.

Canada’s Advanced Research and Innovation Network (CANARIE) and BCNET, a non-profit, shared IT services organization constructed the production grade network to transmit the data. The data transfer was done using an open source application developed by Caltech called FDT. One of the amazing accomplishments in this was that all of the data transmitted was received on only 4 pieces of equipment on the show room floor. This type of data transfer would have required dozens of servers just a few years ago. The video below describes the type of technology used to make this landmark data transfer happen.

One of the factors driving the need for this kind of speed is the Large Hadron Collider (LHC) at CERN. The amount of data being collected at the LHC is growing rapidly so it is becoming increasingly important to find avenues of transporting this data worldwide at faster speeds. “Enabling scientists anywhere in the world to work on the LHC data is a key objective, bringing the best minds together to work on the mysteries of the universe,” says David Foster, the deputy IT department head at CERN.  Hopefully this new technology will lead to innovations to make data sharing in the scientific community a little easier.

According to the Caltech press release, “the key to discovery, the researchers say, is in picking out the rare signals that may indicate new physics discoveries from a sea of potentially overwhelming background noise caused by already understood particle interactions. To do this, individual physicists and small groups located around the world must repeatedly access—and sometimes extract and transport—multiterabyte data sets on demand from petabyte data stores.” In case you’re wondering, that amount of data is  equivalent to hundreds of Blu-ray movies.

More information can be found at You may also want to read more about CERN’s research at the following:

Higgs Boson Definitely ‘Observed’, But Not ‘Discovered’ As Yet: Official Word From CERN

The Higgs search is not yet over and is all set to go on at LHC, CERN. This is the natural consequence of the CERN official seminar.

The Higgs has been definitely observed at the energy 126 GeV at a 3.6  2.3-sigma confidence level at ATLAS, combining all decay channels!

The data presented at ATLAS, by ATLAS boss Fabiola Gianotti, is more-or-less in line with Standard Model expectations.

Result from ATLAS:

The Higgs officially lies between 114 GeV to 141 GeV. The rest of the mass range has been eliminated with 95% confidence level.Several channels like the Higgs-> WW* has been excluded.

The mass range between 113 t0 115.5 GeV has been excluded, as has been the range from 131-453 GeV, with the exception of a window from 237-251 GeV at 95% confidence.

The Higgs-> gamma-gamma is a very promising channel and this suggests the 126 GeV figure for the mass of the Higgs. This suggests the presence of a ‘low-mass’ Higgs, which is quite in line with the Standard Model.  More data in 2012 will help CERN make a more definitive statement.

  • Bottom Line: Local Significance – 3.6-sigma; Global Significance – 2.3-sigma  at 126 GeV

Result from CMS:

The CMS results ruled out a high mass Higgs, much like the ATLAS results. 270-440 GeV was excluded and the Higgs->gamma-gamma channel gave very clear results. This low mass Higgs is very consistent with the previously announced ATLAS results, which is extremely good news.  There were excess events noticed between 110-130 GeV, in the tau-tau and bottom-bottom decay channels; this eliminates 134-158 GeV mass range.

A curious 4-lepton excess was noticed at 125 GeV, which is bang on target, if you take the ATLAS results (above) at face-value. This is again, very good news. The Higgs-> WW and Higgs-> ZZ excludes 129-270 GeV mass range. Multiple channel “modest excess” was noticed just below 129 GeV!

  • Bottom Line: Local Significance – 2.6-sigma; Global Significance – 1.9-sigma  at 124 GeV  
One of the key slides from today's seminar. Look at the excess in each of the channels at 126 GeV! (Courtesy: CERN live webcast)

The global results take into account the so-called ‘look elsewhere’ effect, which means that it factors in the chances of observing this same local excess at any point within a certain range and also in all channels.

The CERN announcement

CERN announced today that the Higgs has been observed’, but not detected’. The subtle difference between these two words lies in mathematics. When CERN says that they have observed the Higgs, it means that they are 99.73% sure that the Higgs is there. This is, however, not enough to guarantee the tag of a discovery. For that, the confidence level has to go up to 5-sigma, which gives a 99.99994% surety. This is very important, since 3-sigma effects have been known to go away in the past.

The non-discovery of the Higgs, as yet

The only reasonable explanation for the less-than-discovery tag at the moment is because LHC still doesn’t have enough data or rather, not enough data has been crunched.

This is surely great news for the particle physics community. The Higgs may be there in this and there are strong indications from both ATLAS and CMS that it is there and this means that the Standard Model has passed its stringent test yet! However, the mass is still to be ascertained exactly. The error bars haven’t been fully established.

So, the wait continues.

The Super Symmetric Models

This mass of the Higgs Boson, if actually true, is extremely exciting. It lends credibility to the cMSSM models, which is one of the basic Super Symmetric Models. There were widespread news reports that LHC has ruled out super-symmetric models or at least the simplest ones. Not quite! The cMSSM can accommodate a Higgs of 121 GeV mass and no higher. However, a small tweaking of the parameters yield a different version of the theory, which can very well accommodate a 125 GeV Higgs.

Another revolution may be just around the corner! Watch out!

Rumors Of A 125-126 GeV Higgs Observation

The Higgs seems to be playing the game better than ever, peeking out once in a while, but not for long enough time! Initial analysis of the data from both ATLAS and CMS indicate an excess in the gamma-gamma channel for the Higgs at about 125-126 GeV. ATLAS detects this at a high 3.5 sigma confidence level and CMS comes in at a more tentative 2 sigma confidence level. This is good enough to tag it as a proper observation. None is good enough to warrant the tag of a discoveryof the Higgs, which requires 5 sigma confidence levels.

More info here:

Both ATLAS and CMS observations are in the gamma-gamma or diphoton channel.

A simulated Higgs Event at LHC, CERN

We had told you about the Higgs search coming to an end here and also that there is a joint seminar in CERN on the 13th of this month. The announcement at this seminar is expected to be the definitive on the Higgs search. It will make or break the Higgs, and, thus, a part of the Standard Model as well.

125 GeV Higgs more interesting than a 140 GeV one!

In a way, a 125-GeV Higgs would be awesome news for physicists, since this mass would require corrections to the Standard Model, since the vacuum becomes unstable at high energies. A 140 GeV Higgs would’ve been more mundane, and would’ve been the simplest of all the scenarios.

The situation is a bit ironic really. The Tevatron had almost eliminated the Higgs gamma-gamma channel decay process. Many scientists were convinced that the gamma-gamma channel was no good, and if the Higgs is found, it will be via the ZZ or WW channels. Though this is not incorrect, the gamma-gamma channel has given one of the strongest signals of the Higgs till date and right before the big announcement at the seminar.

It is unlikely that CERN will say anything about this before the 13th December announcement. Fingers crossed!

More info here:

Revealing the God Particle: CERN To Hold Joint Higgs Boson Seminar On Tuesday!

There is palpable tension at CERN for sure people might not sleep till Tuesday, the 13th. The premier particle physics laboratory is all set to hold a special seminar that day, possibly to announce latest in the search for the Higgs boson. The search is nearing an end and this is expected to be a landmark announcement, possibly one that can either confirm or rule out the Higgs boson.

The 13th  December joint announcement might be the last one on the Higgs. We are hoping for either a confirmation or nullification.  

A 125-126 GeV peak for the Higgs? Tantalizing:
The tunnel - to the final answer?

We had covered a seminar given jointly by the ATLAS and CMS collaborations last month here and we had told you that the search was nearing an end.

The latest news yet!

The mass ranges for finding the Higgs has been narrowed down to just 30 GeV between 114 to 144 GeV, as per the simplest version of the Standard Model. The finding of the Higgs boson is a crucial step, as it would be the final confirmation of the tremendous success of the Standard Model.

Get your camera out! Or maybe not!

The Standard Model

The Standard Model of particle physics is a framework based on very fundamental principles of physics. It describes the interaction between different particles and the three forces electromagnetism, weak and strong. Although there are a number of freely adjustable parameters, the Standard Model has been the most successful theory of physics ever. The progress of physics in this direction has been extremely rapid, especially in the 1950’s to the 1990’s. Each of the particles predicted by the Standard Model has been detected, giving both theorists and experimentalists enormous confidence that this is the correct model. Theory has always been immediately confirmed by experiments, and they have invariably confirmed the Standard Model predictions! All that remains is finding the Higgs and this one last piece is playing hard-to-get.


Many physicists are tensed about the prospect of there being no Higgs! Many others, among them notably Nobel Prize winner Steven Weinberg, feels that it would be exciting if the Standard Model Higgs is not found! There are many alternative models and these would then gain center stage.

All in all, it is safe to say that this one announcement may be the fork in the path for physics going forward. Higgs or no Higgs – that is the question. The answer comes on the 13th!

A 125-126 GeV peak for the Higgs? Tantalizing:

UFOs Invade Large Hadron Collider

Physicists working at CERN’s Large Hadron Collider, LHC for short, have encountered some unexpected guests in their quest to find the “God Particle“. UFOs are interfering with this high-powered research, according to a report by Live Science. These UFOs are not the extraterrestrial kind, however. They are unidentified falling objects.

Photo Courtesy Wikimedia Commons

The LHC is a 17-mile-long particle accelerator designed to slam opposing beams of protons into each other at near-light speed. Once these protons collide, they produce a brilliant display of subatomic particles. Scientists hope to use this method to find the ever elusive “God Particle” which is thought to be what gives elements their mass.

Lately, researchers have discovered that something is getting in the way of these collisions, essentially dampening the blow between the protons. These UFOs are thought to be some type of microscopic dust particle and, as long as they are around to interfere, scientists will likely never find the results they’re looking for.  Tobias Baer, a physicist working at the LHC, wrote that UFOs are “one of the major known limitations for the  performance  of the Large Hadron Collider”. Apparently, between April and August of this year, there were 10,000 UFO events. Some even caused “beam dumps” which is when the beam actually shuts down.

Scientists will continue to research the cause of these UFOs in hopes of devising a plan to eliminate them. In the meantime, you might want to read more about the LHC. Enjoy these great articles by our own Debjyoti Bardhan.

Higgs Search At LHC Nears End Has The Higgs Already Been Found?


Hint Of New Physics At LHC Explaining the LHCb Results