Tag Archives: CMS

WordPress 3.7 Will Come With Automatic, Background Updating

Today, blogging and content management software WordPress released the first beta for its upcoming 3.7 version of the software. Among several bug fixes and feature updates, the biggest apple in the bucket is the ability of the software to update itself – overnight, without any manual input.

wordpress-logoWordPress has had this feature since antiquity, but always via plugins. It is only now that the WordPress core can boast of it. “3.7 Beta 1 will keep itself updated. That’s right — you’ll be updated each night to the newest development build, and eventually to Beta 2. ” — says  Andrew Nacin, WordPress Lead Developer.

There will be situations where “WordPress can’t reliably and securely update itself” — Nacin mentions, and for these you’ll be alerted via email. The automatic updates will also work for official translations, in case you’re running WordPress in a language other than English.

The 3.7 Beta 1 for WordPress is nowhere near a complete, stable offering and you should be wary of installing it on websites you don’t want to risk the working of. In any case, if you’re one of the hard ones, the link to the beta is right here →

LHC Collaborations Present The Historic $9 Billion Higgs Boson Paper

The publicized $9 billion papers on the Higgs Boson are out! Both the CMS and the ATLAS collaboration at the LHC, CERN have been working against the clock for the last two months to churn out the result that the world was looking forward to – finding the Higgs Boson. Having found the Higgs Boson and announcing it on the 4th of July at Geneva, the CMS and ATLAS collaborations have now released two papers, both reporting that they have improved upon their earlier presented results.

The iconic Higgs image – a diphoton event

Stating the Obvious

The 4th July conference had already stated that both the CMS and the ATLAS detectors at LHC have found the Higgs Boson, the long sought after particle responsible for endowing all massive particles with mass. The search has been on since the LHC started running more than two years ago. The long time required just goes to show the magnitude of the search – finding the Higgs Boson wasn’t easy. But make no mistake – the Higgs Boson is definitely there!

Now, these two papers, one by CMS and the other by ATLAS, do something on expected lines – they bump up the significance of the result. This simply means that they make the result more concrete.

Improving the Results

CMS

To put in the numbers, the CMS collaboration had quoted a significance of 4.9 sigma or 99.99995% surety of the presence of the Higgs at a mass of 125.3 GeV. They have just bumped up to 5.0 sigma, which means that the surety is not 99.99997% but at a mass of 125.5 GeV. The error bars stay as they are. The decay channels of highest significance are the diphoton (or the gamma-gamma) channel, where the Higgs decaying to two photons, or the ZZ channel, where the Higgs boson decays into two Z-bosons.

ATLAS

The ATLAS collaboration publish a more adventurous result. They have bumped up their significance from the 5.0 sigma announced on 4th July, to the 5.9 sigma! That is a huge improvement, but this also raises a few questions about the analysis of data. How is it that the ATLAS collaboration can bump up their significance so very quickly?

Both collaborations have gracefully dedicated their papers to all those who were associated with the Higgs search, but have passed away and couldn’t see the remarkable results.

December ahoy!

All of the questions – and there are many – will be answered in an expected conference in December, when the data collected the LHC in the next three months will be analysed and presented. The LHC is set to go into a period of hibernation after that for about 14 months and expected to resume in 2014.

Higgs Boson Discovered: What Today’s CERN Conference Really Meant

To be proved wrong has never felt so good!

If you’ve been following our blog for the last few days and been interested in the science posts and those on the Higgs, you’ll know that I was very skeptical about the discovery of the Higgs Boson by the time this presentation comes about. And boy, am I proved wrong! And I am elated about it.

Found!

Let’s be honest – it isn’t the Higgs

Okay, to be honest, the exactly correct statement would be this: There is a particle, hitherto unknown, having mass between 125 and 126.5 GeV (giga electronvolt), which has been discovered with 99.999997% certainty. We still don’t know whether this is the Higgs Boson or not – it could just be another particle.

It’s not the Standard Model Higgs

In fact, to make things interesting, this is really not the Standard Model Higgs. So people claiming that this ‘completes’ the Standard Model are, at least partially, incorrect. While the Standard Model predicts – and requires – the Higgs Boson, there is nothing that we know right now that says that this discovered particle is the Higgs.

Forget the details. Look at the red peak. Look at what it means in the legends. Appreciate and bask in the glory.

Furthermore, the Standard Model predicts a Higgs with the mass of about 140 GeV or thereabout. What we have got is something with a mass in the ballpark of 125-126 GeV. Even if this is the Higgs, this is NOT the Standard Model Higgs.

What we really have!

So what have we really got on our plates? What we do know is that there is a particle whose mass is 125 GeV or so and how it decays. We also know how much it decays through the various decay channels – the so-called ‘branching ratios’. We are yet to know the charge of this particle and its parity. We do not know whether this is a fundamental particle (like the electron, with no ‘sub-parts’) or a composite one (i.e. made up of more elementary particles like quarks).

As Fabiola Gianotti, ATLAS spokesperson, said:

We are entering an era of Higgs measurement.

That is a lot of work left. We need to figure out what we are looking at really.

Rolf Heuer, CERN Director General, said that this is like looking at someone from far away and recognizing him/her immediately to be your best friend. But you’re not quite sure. You want that person to be closer to you so that you can make sure that it is indeed your best friend and not his/her twin.

Quite true. We need to take a better look. Translated into the language of high energy physics, that means ‘We need more data’. The saga will continue till the end of this year, then there will be a break and will continue again in 2014.

So, what can it be, if it’s not the Higgs Boson? It can be one of the supersymmetric partners of some already known particle. We don’t really know anything about the energy scale at which super-symmetry sets in or when supersymmetry breaks, but there is a fair possibility that the LHC might be detecting tantalizing hints in the next three months. When it comes back in full force in 2014, running at a higher energy of 14 TeV, compared to 8 TeV currently, we will definitely rule out or embrace supersymmetry at the 5 TeV energy scale.

Don’t worry, if you don’t get this – it’s futuristic talk. We want to talk more about today’s conference and that is what we will do!

Today’s conference: what they really said!

So this particle we are seeing today – let’s just call it Particle X till CERN says that it is indeed the Higgs boson – decays via different modes. A particle decays if it is heavy and there is no law or conservation principle preventing it from decaying. And it can decay via different end products – two Z-bosons, W-bosons, photons, four leptons etc – and all of the decay channels have some probability. One can be more probable than the other, and some channels can have more background noise than others. This happens if, say, a decay product can come from more than one source.

For example, bottom quarks can be produced from a lot of different sources, like all the so-called QCD processes. This masks the signal coming from the Higgs decay. The subtraction of background often leads to subtraction of the signal itself.

Notice the broken yellow lines emerging out of the detector. Those are photon lines. Actually the broken line is a way to represent the fact that photons are invisible and not caught in the tracker. Then they are detected in the electromagnetic calorimeter, where green lines represent energy dumps.

Clean channels

In order to cut through this mess, it is imperative that one identifies ‘clean channels’. Two such channels for this particle X are lepton channels and the di-photon channels. Particle X can decay into two muons or two electrons accompanied by the respective anti-neutrinos (don’t bother about those) through the lepton channel and, as the name suggests, into two photons in the di-photon channel. And lo, the signal is the strongest in these two channels. CMS and ATLAS (the two detectors at LHC searching for the Higgs) both have been extremely diligent and successful in looking for signals in these two channels. Both have scored grand success.

The Higgs decay modes and how they contribute to the total cross-section

Look at the green squiggle dipping down right above the black continuous squiggle. That, the legend on the left reveals, is the signal from the di-photon channel. Look how strong that signal is! This immediately suggests that the particle is a boson (otherwise, if it were a fermion, it would violate fermion number conservation) and that the particle cannot be a spin-1 particle (as the photon is a spin-1 particle and we can either have spin-0 or spin-2 for the initial particle). The Standard Model Higgs is a spin-0 object.

What about the charged lepton channel? The two lepton channel is an indirect way to infer the presence of the ZZ or the WW channel. The neutral Z-boson or charged W-bosons are formed from the decay of the Higgs boson. These then decay into muons and electrons, which are then detected. It turns out that our particle X mimics the Higgs Boson quite closely.

What does CMS say about the different channels?

For the gamma-gamma channel (another name for the diphoton channel), the surety is about 4.1 sigma for the particle X having a mass of 125 GeV.What about Z-channel? It spits out 3.2-sigma confidence level for X having a mass near 125 GeV.

Add these two in quadrature (square each, then add and then take the square root of the sum) and you get 5.2-sigma!! This is winning, as the confidence level required for announcing a discovery is 5-sigma!

More data is expected to bump up the confidence level even further. Particle X could be as certain as 7-sigma by the end of December.

It’s not worth repeating the story for ATLAS as it is very similar.

Being cautious, still

CMS hit it just right when they cautiously put this up as the defining slide, saying “We have observed a new boson with a mass of 125.3 +/- 0.6 GeV at 4.9-sigma significance”.

Yep, it’s that simple.

The conservative 4.9-sigma, instead of a two-channel combined 5.2-sigma is typical amongst high energy physicists. This takes into account other channels and the so-called ‘look-elsewhere effect’. We need not get into that for our purposes here.

Point of disagreement – a potential for trouble?

Now let’s come to the discrepancy between the two collaborations – CMS says that the boson is at 125.3 +/- 0.6 GeV, while ATLAS says that it is at 126.5 GeV. The ATLAS collaboration hasn’t put in the error bars. So what are we supposed to make of this? What about the 1 GeV discrepancy?

We don’t know right now. Rolf Heuer made light of the incident:

We have the Higgs, but which one?

Rolf Heuer’s bag of quotes doesn’t end there, and so we would like to end with one of his gems – one signifying finality:

I said we will have a discovery this year. DONE!

Done, indeed. Congrats to everyone on the CERN team and the worldwide collaborations!

Don’t Believe The Rumors – The Higgs Boson Has NOT Been Discovered! Really!

In a few days, the floodgates will open and you’ll hear about the Higgs Boson being already found. The Holy Grail of particle physics will have been found and only CERN will need to confirm it in their press release. When CERN will deliver the promised press release, they will inevitably say that the Higgs is still far from being discovered and that they have only see a ‘statistically significant fluctuation’ about some energy range. The whole non-high energy physics world will breathe out a collective sigh and, defeated, ask ‘How much longer?’

Not quite yet! (A Higgs to four muon event)

 Higgs Not Discovered!

In order to spare at least our readers from being part of this international collective gasping team, I would like to mention this: The Higgs Boson’s status on its road to being discovered hasn’t changed since the December CERN update. It hasn’t been discovered as yet!

I predict that this is the line that CERN will adopt when it gives the Higgs Boson status update during the International Conference on High Energy Physics (ICHEP) that will be held in Melbourne from the 4th of July to the 11th of July.

The Last Six Months at the LHC

But then what has changed in the last six months? Has the LHC been doing nothing?

The LHC is now operating at a new energy scale. The LHC had been colliding beams at 7 TeV energy last year, and, beginning this year, it has been colliding beams at 8 TeV energy. The good news is that they still see the 125 GeV bump in the 8 TeV data they saw in the 7 TeV data, which has been attributed to the Higgs Boson. This means that the 125 GeV bump is not some random fluctuation, but an actual particle – probably the Higgs.

Why Is It Still Not A Discovery?

However, the data collected is not enough to guarantee a discovery, not even when integrated with the 7 TeV data. The 7 TeV data had yielded a confidence level of 1.9 sigma from the CMS detector and a confidence level of 2.3 sigma from the ATLAS detector. Both numbers are far from the 5 sigma confidence level needed to guarantee a discovery. However, the coincidence of the mass range for the fluctuation in the two detectors is heartening.

As I have explained here, ‘confidence level’ is a quantitative measure which tells physicist how unlikely it is that a certain signal is a mere fluctuation. So 3 sigma means that the chances that a signal is a fluke are less than 0.13%. High Energy physics demands very high rigour at 5-sigma confidence level – that’s the doubts reducing from 0.13% to less than .00007%.

What To Expect From ICHEP

The ICHEP announcement will say that the Higgs has been seen in the same energy range – 125 to 126 GeV mass range – and that the amount of data is not enough to say that it is really there. The 8 TeV data is far too small – giving at most a 1.5 sigma confidence level and no more. Integrated with the 7 TeV data, the confidence levels for both detectors might swell up to 2.5 to 3-sigma (taking into account the look-elsewhere effect), which, though significant, is still not a discovery. Sorry for the disappointment!

The good news is that this is exactly what is to be expected. The Higgs search is expected to end by the end of this year. That is when you will REALLY get to know whether the Higgs actually exists or not.

As for ICHEP and Higgs announcements by CERN, you can rely on us for the information. We will post them as they are announced. Not before!

LHCb Detects Decays of B-Mesons Which Hints At New Physics

The most promising signatures of something beyond what we know have been coming consistently from an experiment in LHC, CERN that has received the least public attention. While the CMS and ATLAS detectors (and collaborations) at the LHC are running their proton beams day and night in search of several things, primary among them being the Higgs Boson, the other big experiment, the LHCb, has been quietly chugging along with its own set of measurements.

Part of the LHCb detector

The latest from the LHCb detector, housed in the same compound as the CMS and ATLAS, is a result that just might signal physics from Beyond the Standard Model (BSM), fashionably titled New Physics. BSM has been a devoutly investigated area of interest for both CMS and ATLAS, but the LHCb focusses on very specific types of particles and observes their modes of decay.

‘Exotic’ Physics

The types of particles LHCb is interested in contains a very exotic type of quark – the bottom quark. Protons and neutrons don’t contain that quark; they are entirely made up of ‘up’ and ‘down’ quarks. The Standard Model accurately predicts the decay rates and lifetimes of particles and, so far, experiments and theory have always matched. The recent LHCb result, adding to a few other ‘anomalous’ results of the past, show deviation from the theoretical values. Of course, no one is jumping into the BSM bandwagon just yet, but there is clearly excitement.

The Result

The LHCb collaboration found that a specific decay – a B-meson (i.e. a particle containing the bottom quark) becoming a kaon (another short-lived ‘exotic’ particle) along with a muon-antimuon pair. Muons are like heavy electrons. The LHCb collaboration observed that there is a difference in the decay rates between a neutral B-meson going to a neutral Kaon-muon-anti-muon and a positive B-meson going to a positive Kaon-muon-antimuon. This difference – called ‘isospin asymmetry’ – is not predicted by the Standard Model and this is what is interesting.

More data is required to confirm whether this is really a BSM signal.

The CERN bulletin: https://cdsweb.cern.ch/journal/CERNBulletin/2012/21/News%20Articles/1451542?ln=en
The LHCb detector website: http://lhcb-public.web.cern.ch/lhcb-public/

 

Data From LHC and Tevatron Shows No Signs of the Existence Of Extra Dimensions

Negative results are important and the LHC just shows that. While the LHC hasn’t been able to find the Higgs Boson with absolute certainty as yet, it has done physics great service by eliminating a lot of different possibilities and put stringent bounds on existing theories. The CMS collaboration at LHC has just released a paper reporting their findings related to the existence of hidden extra dimensions. This is crucial to the very fabric of string theory.

The CMS detector at LHC

The CMS hasn’t found anything in their data that indicates that extra dimensions exist. The team has looked at the energy range of 2.3 to 3.8 TeV, which is the typical collision energy of protons, when the LHC runs at 7 TeV beam energy. The LHC recently upgraded to 8 TeV, 1 TeV up from the usual, but there is little hope of finding things at that energy. We can only wait till the LHC resumes its run after the break it is scheduled to take in a few days. It will be back at 14 TeV and maybe then we can get something on extra dimensions.

And the Tevatron adds to the misery…

Not only the LHC, even the Tevatron data eliminates the presence of extra dimensions, at least at low energies. The Tevatron is dead, but the data is still there and the D-Zero detector team is looking at the energy range around 260 GeV and have found nothing.

So far, the theoretical bounds on the energies at which particles might couple to extra dimensions have large errors. So this result really tells us what the lower limit for any experiment searching for extra dimensions should be.

The LHC is continuing to negate anything beyond the Standard Model. It has got good data to verify the one last piece of the Standard Model – the Higgs Boson – and the search is in its last few days. It seems that the emergence of physics beyond the Standard Model, except in the neutrino sector, isn’t happening at the moment.

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.

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:  http://blog.vixra.org/2011/12/02/higgs-rumour-anaylsis-points-to-125-gev/

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:  http://blog.vixra.org/2011/12/02/higgs-rumour-anaylsis-points-to-125-gev/

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

The Higgs Boson may have finally have been caught or, may be, not! Only a clutch of scientists with direct access to latest LHC data knows whether the Higgs has been found or not! Whatever the result be, one thing is for sure the Higgs hunt is nearly over. CERN researchers have restricted the Higgs mass to a window of only 30 GeV, taking into results from the Large Electron Positron (LEP) collider, the Tevatron and, of course, from the LHC itself.

A simulated Higgs event at LHC

The Higgs, if present in Nature, has got extremely little energy space to hide in. At a conference in Paris, held today (18th November), ATLAS and CMS researchers got together and erased out a HUGE range for the possible mass of the Higgs. A large swathe from 141 to 476 GeV was wiped out in one fell swoop. Says Guido Tonelli, the spokesman for CMS

We’ll know the outcome within weeks.

This is surely going to increase the pulse rate of any particle physicist in the world.

The mass range as it looks now (Courtesy: Nature)

What if…

What happens if the Higgs is not found? A lot of problems for the Standard Model. The Higgs boson is the simplest way to generate masses for fermions (like electrons and protons) and bosons (like W and Z bosons). There are other possibilities, but this one Higgs model is the simplest and most beautiful of all the possible models. However, as Feynman would say, if theory disagrees with experiment, then it’s wrong and it doesn’t matter how beautiful the theory might be.

For long, has the Higgs mass been pinned at about 140 GeV. There is still a strong possibility that the Higgs, if found, will be of this mass. We may be on the brink of history.

More Info:  http://www.nature.com/news/higgs-hunt-enters-endgame-1.9399