Tag Archives: ATLAS

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

Get The LHC On Your Android Phone, Thanks to Oxford University

Now, you can participate in the unraveling of the greatest mysteries ever on your Android phone. Oxford University has come up with a Large Hadron Collider (LHC) app for Android mobiles. The app is nicely named LHSee’ and gives the user a nice chance to explore the Large Hadron Collider in full 3D glory and detail. You can download the app here.

So, the Higgs Boson particle is still elusive and the LHC is hot in pursuit of the mysterious Boson. Not that you can do much about that sitting at home (or maybe you can donate you’re your computer’s processing power to CERN), but you can certainly get a sense of what is going on at the LHC on a regular basis.

Not as easy as Angry Birds

The bad news is that the details are really involved and you’ll probably take some time to take in everything. The Oxford bundle comes with a host of educational resources, besides the simulation. You’ll be able to learn more about ATLAS, one of the premier detectors at the LHC. It even has a game Hunt the Higgs, which we hope will become as popular as Angry Birds. So, while the LHC is busy colliding protons at monumental energies, you’ll be challenged with picking up the different proton-proton collisions from the jumbled mess. If you spot the Higgs, do give yourself a pat on the back.

Check out the official Oxford University site here:  http://www2.physics.ox.ac.uk/about-us/outreach/public/lhsee

CERN’s huge LHC now comes in your phone. That’s another reason for a physicist to buy an Android phone, if you don’t already have one.  The biggest search in the history of humanity now occurs on your phone. Feel proud about that! High energy physics has never been this much fun!

Download link from Android market again:  https://market.android.com/details?id=com.lhsee

New Physics Should Be Around The Corner, Says Rolf Heuer, Director of CERN; Charts Future After LHC

It was just yesterday, yet we have come so far! The first proton beams at a respectable 7 TeV energy was started only on 30th March, 2010. It has been hardly a year and a half and so much has already been achieved. This was the basic message sent out by CERN speakers Frederick Bordry and Rolf Heuer, also the Director of CERN at the Lepton Photon Conference, 2011, being held at Tata Institute of Fundamental Research, Mumbai, India.

Projects! Projects!

There are a lot of projects on the horizon, both short time and long time. Obviously, the long term projects are ambitious and a bit ambiguous as of now. However, as Heuer said, they are practical. We should not be afraid that it is not easy, he said.

Rolf Heuer, Director General of CERN, speaking at the Lepton Photon Conference, 2011, at TIFR, Mumbai

Among the many new developments happening or proposed at LHC is the development of magnets that can generate extremely high magnetic fields, called high-field magnets. These will be required to increase the energy of a beam, without lengthening the collider tunnel. Prof. Michael Peskin of SLAC, who was in the audience, asked if this is a dream or a programamidst chuckles, to which Bordry replied that it was certainly a realistic program.

The CMS detector at LHC

The LHC is expected to have a long shutdown period from 2013 to mid 2014 for repairs and maintenance work.

New physics and monster accelerators

A number of new projects are upcoming, even though they haven’t been officially sanctioned. Yesterday’ it was the synergy of the Tevatron, HERA and SLAC that led to the discovery of the Standard Model, said Heuer, adding that the LHC results will guide the way at the energy frontier.

About the Higgs search, Heuer said that while finding the Higgs will be a discovery, not finding the Higgs and ruling it out will also be a major discovery. People should not say that these scientists are searching for nothing, he quipped. Not finding the Higgs will be a major result, since it will completely destroy the Standard Model, allowing other models of physics to come into the limelight.

Among a plethora of futuristic plans announced, the most spectacular was the announcement of a hadron-lepton collider the LHeC. The LHC is a hadron-hadron collider. It can collide protons together or lead/silver nuclei etc. A hadron-lepton collider will be able to collide a proton, and say an electron. The energy per beam of the LHeC will be 16.5 TeV, combining to give a massive 33 TeV in total. The LHeC design is on my desk right now, but I shouldn’t be mentioning that here, he remarked drawing loud laughter from the global audience. As far as LHC physics is concerned, he said that 2012 will be a decisive year. The TeV results will either lead to the discovery of new particles and some new physics will be known or it will be a reformulation of the physics we already know. Both will be progressive steps for particle physics.

Heuer spoke at length on the building of the linear accelerators International Linear Collider (ILC) and the Compact LInear Collider (CLIC). Today, we need to keep our choices openwas Heuer’s advice.

International Collaboration

On the question of collaboration, Heuer said that CERN was throwing its doors open to non-European countries. The E’ in CERN is going from European’ to Everybody’. We’re not changing our name, however, said Heuer.

Exciting times in particle physics beckon us! As usual this sentiment was put emphatically in Heuer’s own words -We are just beginning to explore 95% of the universe.

I’ll let the scientist in Heuer have the final word on this report. When asked if he’ll be bothered if the next big accelerator is located in the US, instead of at CERN, Heuer put it beautifully, I don’t care where the collider is! I only care about the science coming out of it.

The scientific enterprise is a greater binding factor than anything else. It’s a silent messenger of world peace, uniting the world in the pursuit of truth and never advertising that facet.

Latest Results of Higgs Search Presented Jointly By ATLAS and CMS, LHC, CERN at Lepton Photon ’11, Mumbai

The latest results on the Higgs search are out. Results were presented separately by ATLAS and CMS detectors of LHC, CERN today(i.e. 22st August, 2011) at the Lepton-Photon Conference, 2011. In this semi-technical article, we present the most important results in a systematic form. The verdict is, however, out the Higgs hasn’t been found as yet.

Check out our first (non-technical) post on this discovery here. A countdown to the Lepton Photon Conference itself is here.

Higgs Production and Decay channels

There are a few things that should be kept in mind right throughout the article. The Higgs boson is primarily produced by interaction of two gluons. (A gluon is what keeps protons and neutrons in an atomic nucleus together.) This is called gluon-gluon production of the Higgs boson.

Next, the Higgs, being highly massive (i.e. having a high mass) decays into lighter particles. This is what massive particles always do they decay into lighter particles. The only thing is that different particles decay at different rates. Heavier particles will decay much faster than comparatively lighter particles.

Higgs event

The Higgs can decay into a number of lighter products. Each of these products leaves a distinctive signature on the detectors and the different modes of decay are called different decay channels’. The Higgs primarily has a gamma-gamma (Higgs decaying into two gamma ray photons.) channel, a WW and a ZZ channel. These are the main channels of interest. The gamma-gamma channel will be the preferred channel if the Higgs is a comparatively light particle about 100 GeV in mass. If the Higgs decays by producing two Z-bosons (the ZZ channel) or two W-bosons (WW channel) then its mass is above 130 GeV.   In other words, the gamma-gamma channel fixes the upper limit of the Higgs mass at 130 GeV, while the WW and ZZ channels fix the lower energy bound at 130 GeV.

Now, here is the interesting part. The WW or ZZ bosons are themselves quite heavy and decay into a number of products. These decay channels produce characteristic detection patterns in the detectors. Comparing the observed rate of decay into these channels with that of the expected value, the data is reconstructed to see if this indeed was a Higgs event.

Now for more technical details

ATLAS Results

The ATLAS detector found no significant excess in the gamma-gamma channel. The bottom-bottombar (b-bbar) channel (this is what the WW bosons break down into bottom and anti-bottom quarks) gave big excess of Higgs event above the theoretically expected Standard Model(SM) production rates. Even though the excess was nearly 10 times the SM predictions, the sensitivity needs to be improved. Furthermore, Tevatron has a much greater say in the b-bbar channel than the LHC, given that it has recorded much higher number of events and has a higher luminosity at that energy range. The tau-tau (tau is a lepton, an electron like particle) channel gave a 4 to 5 times excess.

The ATLAS detector at LHC, CERN

Overall, there was no significant excess in any of the channels to warrant a discovery. There was no significant excess number of events noticed for the Higgs in the mass range of 110 GeV to 160 GeV. This mass range is tentatively excluded with 95% confidence level. However, at 99% confidence level, there is a window about 142 GeV, which can be a possible detection window. Further experiments will probe this window more thoroughly.

CMS results

CMS detected no excess in the gamma-gamma channel. A slight excess was noticed in the tau-tau channel and this is expected to be an important channel for further investigation, owing to the fact that data reconstruction from this channel points to a Higgs mass of about 140 GeV.

Excess of events in the WW going to lepton-lepton channel suggests a mass range of 130 GeV to 200 GeV. Three pairs of events have been notices at three mass ranges 122, 142 and 165 GeV for the ZZ channel. Only the 142 GeV event is consistent with Standard Model predictions. Happily, this is the very window that wasn’t excluded earlier with 99% confidence level.

Out of theoretically expected mass range exclusion of 145 to 440 GeV, three ranges have been excluded 145 to 216 GeV, 226 to 288 GeV and 310 to 400 GeV. Anything above 400 GeV is unlikely and the crucial 130 to 145 GeV window is still open. These mass ranges have been excluded with 98% confidence level.

Higgs search continues with full force. LHC will provide a lot more data samples in the coming months and this might ultimately lead us to achieve the Holy Grail of Particle Physics.

Higgs Boson Still Not Found: Huge Official Announcement from LHC, CERN


This is the joint announcement made by the ATLAS and CMS teams, LHC, CERN at the Lepton-Photon Conference, 2011 being held at Tata Institute of Fundamental Research (TIFR), Mumbai, India. This is likely to be a disappointment for many around the world, both within and without the particle physics community. The search is however on!

A warmup countdown post to this Lepton Photon Conference, 2011 is here. Semi-technical post showing all relevant results and figures can be found here.

The Higgs Boson

The Higgs Boson, predicted from considerations of symmetry in Quantum Field Theory by Peter Higgs, is the particle theoretically responsible for endowing every other massive particle with mass. It’s a boson with spin zero, with positive parity and charge.

Weak Signals

There were a number of weak signals noticed that preceded the event. These Higgs signatures’ included the W-W or the Z-Z decay channel for the Higgs as the primary decay channel. This means that the Higgs once produced will decay into two W or Z-bosons, which will in turn break up into electron-positron pairs or muon-antimuon pairs. Unfortunately, none of these events could stand up to the rigors of analysis and survive till the 5 sigma confidence level was reached in both ATLAS and CMS detectors, as yet.

No such significant excess has been observed in the lower mass gamma-gamma channel. Also, more exotic branches like the tau-tau and b-bbar (bottom-bottombar quarks) have not offered anything promising.

The results of Tevatron, Fermilab are similarly blank, with no significant excess noticed in any channel.

The Future

This is also an exciting opportunity it opens up new possible physical theories. Spontaneous symmetry breaking, at least what we know of it now, may not be the whole story. There are many rival’ theories of the Standard Model, many requiring no Higgs boson to achieve mass. These Higgless models may become the focus of mainstream research and the LHC may be next used to test the predictions of such theories.

However, it is too early to make such claims. The Higgs search is going on at full blast.

And a Promise

We will bring more articles soon, explaining what this means for the Standard Model and particle physics in general. We will also run an article elucidating the jargon of particle physics. Hold on for that it’ll come sooner that you think.


Actual results from the ATLAS and CMS joint announcement on the Higgs Boson search can be found here. All relevant facts and figures present.

Countdown to Lepton-Photon Conference, 2011: ATLAS To Make Major Announcement on Higgs Search

Some big news is just around the corner. The ATLAS collaboration at LHC, CERN is all set to announce the status of the Higgs Boson search at the giant collider in the upcoming week at the Lepton-Photon Conference 2011, being held in Mumbai from 22-27 August, 2011. The announcement is one of particular importance since it is rumored to be the definitive one in the quest for the Higgs Boson. Whether the Standard Model of Physics, one of the most beautiful and successful edifices of physics ever constructed, will stand or need revision will hinge crucially on this one announcement.

The Lepton Photon 2011 Logo

The Lepton-Photon Conference, 2011

The Conference The XXV International Symposium on Lepton-Photon Interactions at High Energy will take place in Tata Institute of Fundamental Research, Mumbai, India and will attract prominent personalities from the world of high-energy physics. The coming week is expected to be a hectic one for both students and physicists at the Institute, with the who’s who of particle physics presenting and discussing current progress, while also charting the road ahead. Preparations are on at full swing within the Institute premises.

We at Techie-Buzz will be covering the huge scientific event from Ground Zero and presenting all the major announcements in real time from it.  You might want to bookmark the website and visit it frequently or subscribe to our newsletter, if you aren’t already on the subscription list.

Some exciting developments precede the event

The watch-word is Higgs’ for everyone and with certain encouraging signs noticed in the last few months, everyone is excited. Particularly stunning are the two results graphed below. Explanations follow the graphs.

The CMS (above) and ATLAS (below) Results for Higgs event, July, 2011

Look at the two graphs (don’t get scared!). The thick black line in each graph represents the Higgs signals. The dashed line represents the predicted Higgs production rate by Standard Model Calculations. A proper signature is said to be found when the observed signal overtakes the predicted signal. Look at the region marked, just between 130 to 150 MeV, where the production rate far exceeds the predicted rate. This coincides with the predicted mass range for the Higgs. This in itself proves nothing, as this might be due to something completely different. What is exciting is the fact that this weaksignal is being noticed in both the LHC detectors, ALICE and CMS. Concurrent results have a better chance of surviving thorough data analysis.

For clarity let me reiterate the two important takeaway points: First, both detectors, ATLAS and CMS, agree on the Higgs signature. Second, the signals have been noticed in the theoretically expected mass range (about 130-150 GeV).

The results are now quoted at a 95% confidence level (or 2 sigma) and do not warrant the label of a discovery’. For that, you’ll require 99.997% confidence (or 5 sigma) from both detectors. We might be onto that.

At the risk of being repetitive, let me again emphasize that the announcement at the Conference in the coming week will nearly finalise the fate of the search for the Higgs Boson. If not found, it may be the beginning of new physics.

Hope to see you here through next week.

Update: The CERN Announcement on the ATLAS and CMS results on the Higgs Search is here. Check it out, its big news.