Tag Archives: LHC

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.

LHC At Home: Now, You Can Help CERN Find The Higgs Boson Sitting At Home

The greatest science project ever designed by man is now calling out to you, dear average Joe or hotshot scientist, for helping it find the elusive Higgs Boson. CERN has launched an extended version of its LHC@home campaign, naming it unimaginatively as LHC@home 2.0, in which CERN wants you to share a part of your computer’s processing power to do science.

The Colossal Collider Comes Computer Hunting

The Large Hadron Collider (LHC) has been actively looking for the Higgs Boson particle, constantly eliminating mass ranges and probing higher and higher energies. Tantalizing signs have been seen, only to be later refuted by CERN itself. The Higgs particle, dubbed The God Particle’ by the popular media, is so far living up to the given divine billing. The Higgs is the ultimate piece of the puzzle of the Standard Model, with all the other particles discovered. No one said that finding the final piece would be easy.

The ALICE Detector at LHC

LHC@home 2.0 is a volunteer computing platform. It aims to use a part of the computing power of your computer, so that CERN can simulate more data. This is the best implementation of the notion of GRID computing, in which computers around the world, linked to a network, can donate a part of the processor’s facilities, which would have otherwise remained unused anyway. The result is a massive increase in processing speed for the central computing facility.

Simulations: Why So Serious?

The most important aspect of a collider experiment, other than building the machine itself, is the collision simulation. Simulations are a vital part because solving multi-particle dynamics is a stressful, often impossible, job. Several particles interacting with several other particles through different interactions at relativistic energies can give physicists nightmares. The way out is to prepare plausible models for the collision and then use computers to simulate the result, should such a collision take place. Important results are noted from the simulation data, like tell-tale signs of new particles, decay channels and sensitive hidden parameters. After documenting the actual collision, data is compared, especially the most conspicuous simulation results.

Simulated Decay of the Higgs

Reconstruction helps refine the model and unexpected bumps occasionally produce excitement. These bumps can be due to a number of causes, but careful analysis helps scientists rule out experimental causes or error. If the bump survives, it’s a new discovery. So far, no Higgs bump has survived.

… And You Can Join In!

CERN gives a detailed instruction manual to anyone interested to join here. Currently, the LHC@home 2.0 is in its test phase and is testing a program Test4Theory@Home.

Learn more about the CERN projects and how you can help here.

Here’s your dream come true: Have a virtual atom smasher at your home, revealing the greatest mysteries of the Universe.

[Editorial] How The US Fund Cuts Due to War Affect Science and All Of Us

Lost jobs, growing fuel prices and rising public discontent is the scene in the US as far as the economy is concerned. Funds are short in all aspects of life, whether it concerns fuel prices (government subsidy), the education sector or business. The dollar falling against the Euro, or even the Indian Rupee, mirrors the sorry state of affairs. The worst hit, it seems, is the science sector, which has been left crippled by a spate of fund cuts across almost all disciplines. The reason for this: War.

The “War On Terror”

Yes, the American long drawn War on Terror’ is acting like a very effective pipe draining monetary resources from all other aspects of governance and life. An estimated $4 trillion has been spent on the war in Afghanistan and Iraq (sorry for not using the label War on Terror’). The achievements have been few and too far apart in time. The most significant achievement in the eyes of the public is the assassination of Osama Bin Laden, who, experts believe, wasn’t very active anyway in the terror network and the success was little more than symbolic. Al Qaeda has the same reach and structure as it had just before Bin Laden’s death. If anything, the martyrdom’ of Bin Laden (as it is viewed in many parts of the Islamic world) has helped Al Qaeda gain more recruits without resorting to covert recruitment procedures. Not to mention, the operation has undermined the relations between Pakistan and the US.

Victims No. 1

Science has had to suffer a lot, as this foolish carnage was unfolding. The most notable victim has been the James Webb Space Telescope. Recently, we reported the plans to scrap the successor of Hubble the James Webb Space Telescope (JWST) and once Hubble completes its lifetime in 2014, there will be no eye in space in the visible range of the spectrum with which we will be able to peer deep into the cosmos.

What Next : Hubble to the left. James Webb on the right. Or is it?

The giant telescope, which would make Hubble look like a pair of binoculars, was set to replace both Hubble and Spitzer in one stroke. Spitzer, which observes in the infra-red frequencies, is still operational and is expected to outlast Hubble. The fund cut by the Appropriations Sub-committee is bound to render astrophysics blind for, at least, the decade.

Victim No. 2

There has been other victims with lower profiles. We had also told you about the ATA (Allen Telescope Array) of SETI put out of operation due to the lack of funds. It is a widespread misconception that SETI’s only job is the search for extra-terrestrials. The ATA was being used for much more than intercepting intelligent radio signals from space, like looking at radio signals originating from very strong radio-sources like Active Galactic Nuclei (AGN’s) and looking at transient radio-sources. This would be extremely useful for studying how quasars truly operate. Further, looking at any active radiation source in many wavelengths is of the utmost essence in observational astronomy.

Victim No. 3

Arguably, the best telescope is The Chandra X-Ray Telescope (no, it’s not the Hubble). Orbiting the Earth, high above the atmosphere, it captures stunning images in the X-Ray band. The X-Ray band of radiation is notoriously difficult to capture on film. The primary reason for this is the extremely high penetrating power of X-Rays; lenses made of glass are useless. The mirrors used to focus a parallel beam of X-Ray radiation need to be at glancing angles (about a degree or so) to the direction of radiation. Further, the mirrors need to be coated with pure gold. Both these factors contribute to increased expenses, the former being responsible for the need of large mirror sheets and the latter being responsible for the obvious reasons. The question is what next? What after Chandra? With the recent spate, there is real worry about the maintenance and succession to the premier X-Ray Telescope.

Victim No. 4

The search for exotic gravitational waves is also expected to take a hit. The existing detector, Laser Interferometer Space Antenna or LISA, is capable of detecting a gravitational wave emanating from a powerful astronomical event in the cosmological vicinity the moment it passes Earth. The problem is the back-up observations. This needs to be followed up by observations in the electromagnetic spectrum, which will be impossible given that Hubble will not have a successor and radio telescopes on land are also in trouble. In other words, a goldmine of observations (say, LISA detects gravitational wave after gravitational wave) will be going to waste given that there is no back-up observation. LISA will be effectively out of operation.

News from LHC, CERN: CMS Results Rule Out Large Mass Range for Higgs Boson Particle

Last year’s run of the LHC has set a cutoff for the expected mass of the Higgs boson. This important result came out of the recently concluded Europhysics Conference 2011.

CMS has excluded the mass ranges of 149-206 GeV and 300-440 GeV for the Higgs with a confidence level of 95%. It has also excluded the masses from 145-480 GeV with a lower confidence level of 90%. This excludes a huge part of the expected mass range, and has gotten particle physicists both excited and demoralised.

Read about the Quark Conference 2011 here, rumour of a Higgs being detected at ATLAS, LHC, CERN here and that news being rejected here. We covered a very recent discovery by Fermilab  here.

The Higgs Boson, also called ‘God Particle’ is the only particle predicted by the Standard Model but has not been detected in any collider. It has been assigned the function of endowing all particles in the Universe with mass. Any particle interacting with the Higgs field, mediated by the Higgs boson, is said to have mass. The boson is named after physicist Peter Higgs, the person who came up with the idea. Unfortunately, the Standard Model says little more than the lower limit of the mass of the Higgs Boson. CERN has given itself till 2012 for proving the existence of the Higgs.

Higgs Event

Further news is that is the results of the 2010 and 2011 runs are interpreted in the light of a Standard Model having four generation of fermions (SM4), instead of just three, scientists put a 95% confidence level on the exclusion of the Higgs boson in the mass range of 120-600 GeV.

There are also many particle physics theories not involving any Higgs boson called Higgless theories and they may now come to the forefront, if the Higgs remains elusive.

CMS is carrying on the search using decays of different particles. It is trying to produce the Higgs using two photons, two tau leptons, two W bosons and two Z bosons.

CERN ALICE Collaboration Sets Up First Center In India at VECC, Kolkata

The very first ALICE center in India was setup in the Variable Energy Cyclotron Center, Kolkata and was inaugurated on 16th June, 2011. CERN hopes that this will be a small step in improving the capability of their Tier-II and Tier-III grid computing facilities and will go a long way in analysis of the huge amounts of data generated by LHC and, in particular, the ALICE detector. The 16th of June happens to be VECC’s foundation day.

Hopes and aspirations for the ALICE Indian Center

VECC for its part hopes to be a more integral part of the global collaboration at the LHC, CERN. It further hopes that this will give students valuable exposure in handling data and in communicating with physics groups around the world. VECC was already equipped with a 80 TB data storage facility receiving data from CERN, which is a part of the grid computing facility.

The Alice Control Room (ACR), part of the whole facility at VECC, will have good conferencing facilities, making it easier for research scholars and faculties alike to have more involved interactions with other groups around the globe and also directly with people working at CERN.

The ACR will be managed by staff, all of whom will be compelled to serve shift duties. CERN and VECC both hope that the establishment of the ACR will help in making plans in the coming future. The ACR currently monitors two workstations for Detector Control System and Data Acquisition.

The who's who showed up. Bikash Sinha at the center (pointing). On his left is Srikumar Banerjee (green shirt). R.K. Bhandari is on the right most, front row.

Personalities

The inauguration was attended by the who’s who of the Indian physics community and by members from CERN. Among the prominent personalities present were Prof. Srikumar Banerjee, the Chairman of the Atomic Energy Commission (AEC) and Secretary of the Department of Atomic Energy (DAE), Govt. Of India, Prof. Rakesh Bhandari, current Director of VECC and Dr. Bikash Sinha, the former director of Saha Institute of Nuclear Physics (SINP) and the current Homi Bhabha Professor, DAE. Paolo Giubellino and Jurgen Schukraft represented CERN from Geneva with their virtual presence via Skype. They briefly reiterated the need for the center in India and outlined the plans for the ALICE collaboration.

Gone are the days when geniuses would come up with theories working in isolation behind closed doors. This is the age of information and knowing the ultimate answer in Physics will take the whole world working together. This is another small step in the long journey.

Eureka Moment Claims Rejected: No New Particle Discovered At Fermilab

It is disappointing news for the particle physics community coming out of Fermilab, we’re afraid. Fermilab has confirmed that the earlier bump seen in the data, presumed to be a new particle, is not significant enough to be considered a detection. We broke the news in emphatic fashion of a new particle discovered in Fermilab in an earlier post.

Story So Far

We had reported that there was a bump found at about 145 GeV with a 5 GeV spread. Data acquired from proton-antiproton collisions with semi-leptonic dijet emissions showed a peak at 145 GeV. The curve was Gaussian in nature with a spread of 5 GeV on either side of the peak. Initial analysis showed that the curve had a three-sigma confidence level (More on confidence levels later). There was thus a strong possibility that a new particle was on the way, since no boson is known having a mass of 145 GeV. The new particle was named as the Z’ or the W’ (Z-primed or W-primed) boson. The Standard Model, wildly successful in particle physics, did not predict this and to fit this in would have required a serious rethinking of known physics. Physicists were naturally excited.

This detection was made at Fermilab at their CDF detector.

The CDF detector

Fermilab was the biggest particle accelerator till the Large Hadron Collider came onto the scene. It has been a major progressive force for particle physics over the last three decades, also serving to etch the American superiority in the particle physics arena. It is however expected to be closed down forever late this year. Data recovered from it over the years is still being analysed, and as such will continue for the next five years. One of the two detectors at Fermilab the CDF had detected the anomalous bump of our present interest.

So What’s Wrong?

There are two problems with the CDF data it cannot be corroborated and it falls outside the required confidence levels.

Problem 1:

The DZero Detector

The other detector at Fermilab, named DZero, repeated the experiment, but failed to come up with any conclusive evidence of detection. The negative DZero result would definitely cast shadows over the CDF discovery. Scientists are now baffled as to how the two detectors extremely alike could give such widely varying results under the same experimental conditions. However this is a very good safeguard.

 

Problem 2: Remember that earlier we had said something about a three-sigma confidence level? It means that the data is reliable and the chances of it being wrong are one-in-a-thousand (99.9% accurate). Confidence levels measure reliability of data. For a discovery to be accepted by the scientific community, the event must have at least a five-sigma confidence level or higher, which means that doubts must reduce to less than one-in-a-million. The problem with the current bump is that it lies just below the five-sigma confidence level.

Graph for the DZero Results.

Take a look at the above graph. Never mind the mathematics and abstruse symbols. Know that the horizontal axis represents the mass of the particles and the vertical axis represents the number of particles detected. At the 145-150 GeV range (point 145 GeV on the horizontal axis), you’d have expected a curve if the previous CDF results were replicated. This is marked with the dotted curve. There is nothing there as far as DZero is concerned. The red regions represent detections and these are in complete agreement with the Standard Model. There is no anomaly to be seen anywhere.

On both counts, the bump is rejected as a new discovery.

What changes then?

Practically nothing changes. The 145 GeV particle, if discovered, would have been interesting, as the Standard Model doesn’t predict it. Further, it could have provided a mechanism for particles acquiring mass without the need of the Higgs boson (essentially becoming the new God particle’). With it being ruled out, the Standard Model stands as it is with the Higgs mechanism being the most favoured mechanism for mass generation.

The discovery would have been exciting, but the field’s exciting even without it. After all, science is like this. DZero spokesperson Stefan Soldner-Rembold  put it approproiately in a Fermilab press conference:

This is exactly how science works. Independent verification of any new observation is the key principle of scientific research.

So very true!

News from LHC, CERN: Released Results from Quark Conference 2011 Exciting

The results of the three experiments conducted by the LHC till the end of last year, during which lead ions were collided, was released by CERN yesterday, i.e. 23rd May, at the Quark Conference 2011, and there is plenty to be really excited about. In the last two weeks of 2010, LHC switched from colliding protons to colliding beams of lead ions. (For news of recent records of beam intensity and beam bunches from LHC, CERN, see here)

Peter Steinberg of Brookhaven, co-convener of the collaboration said:

The first LHC heavy-ion run was a great success for ATLAS.

Why Lead Ions?

Lead ions being heavier carry a lot more energy than protons and thus their collisions produce new heavier and exotic particles and new forms of matter, not seen in proton-proton collisions. Lead ions are produced by stripping lead atoms of all their electrons. In these collisions, scientists have detected traces of Quark Gluon Plasma, the stuff that was present in the primordial Universe.

The early universe, a few hundred microseconds old, was a soup of extreme energy density, in which quarks, gluons and leptons moved around. Quarks and gluons were believed to form a plasma like substance, called ‘Quark Gluon Plasma’. In colliding lead ions, scientists hope to recreate the plasma and study the very early universe.

What is QGP?

QGP can be theoretically made in the laboratory by heating matter upto 2×1012 K, which is roughly a hundred thousand (100,000) times hotter than the Sun’s core temperature and about a billion (1,000,000,000) times hotter than the surface of the Sun. This can only be achieved by colliding heavy ions at ultra-relativistic speeds(speeds close to that of light, or more technically, having a high Lorentz factor). Lead and gold ions have been selected by LHC. Most collisions don’t happen head on, but a few do. If enough of these head-on collisions are produced at a certain small region, they may form the exotic matter QGP, which has densities higher than those found on neutron stars. (Just a layman’s comparison: One teaspoonful of neutron star matter outweighs all the cars of the Earth put together!!) By studying the flow of this material, scientists can fit data into theory and also verify theoretical predictions.

Detectors and Achievements

QGP was first produced by the Relativistic Heavy Ion Collider (RHIC), Brookhaven, demonstrating for the first time that such dense exotic forms of matter can indeed be produced in a laboratory. ALICE, a detector at LHC, specifically designed and calibrated for very high energy collisions and for studying Quark Gluon Plasma, has confirmed the fact and has been able to study the properties of the plasma. It has verified theoretical predictions than QGP is an ideal fluid.

The ALICE detector at LHC

CMS, another detector in LHC, designed as a general purpose detector for high energy particles, have also detected the production of the W and Z boson, both critical components in the electroweak theory. CMS has also detected a marked suppression of the weakly bound states of the bottom (or, as some people prefer, beauty) quark, which scientists believe has great importance in further study of QGP.

ATLAS, one of the general purpose detectors for high energy particles alongwith CMS, has studied the macroscopic properties of the plasma, like the number and density of charged particles emerging out of it. It has also mapped out the energy and matter density, elaborating on the collision mechanisms and transport properties of the plasma.

As CERN’s director, General Rolf Heuer says:

These results from the LHC lead ion programme are already starting to bring new understanding of the primordial universe. The subtleties they are already seeing are very impressive.

LHC is now setting a benchmark in high energy physics, going where no collider has dared to go before. It would thus be appropriate to close with the following words from CMS spokesperson Guido Tonelli:

We are entering a new era of high precision studies of strongly interacting matter at the highest energies ever. By deploying the full potential of the CMS detector we are producing unambiguous signatures of this new state of matter and unravelling many of its properties.

An exciting future in high energy physics awaits us.

News From LHC, CERN: Record Beam Bunch, Record Beam Intensity

News of new records seem to be tumbling out of CERN in the past two days, with both the number of bunches per beam and the beam luminosity in the Large Hadron Collider (LHC) hitting a record high. Though this is still a long way away from the theoretical maximum predicted by the engineers for LHC, this is a significant step.

In this post, we discuss about the records only. In a subsequent post, we shall discuss what LHC has managed to uncover about quarks the basic building block for all almost matter you see around you.

First: bunches per beam

Yesterday, i.e. on 22nd May, 2011, CERN announced that the LHC had crossed the mark of 900 bunches per beam, creating a new record for itself with 912 bunches. This betters the previous count of 480 bunches, which was achieved only a month back. But exactly what is a bunch?

What is a bunch?

The particles in a beam in LHC is not a continuous stream, as you’d have thought. They are broken down into small collections each containing the same number of particles. These collections are called ‘bunches’. So each beam is made up of a number of bunches, each bunch being made up of a huge number of particles. Bunches arrive with a certain time delay. The present time delay between two bunches is 50 nanoseconds, while the theoretical upper limit (the one permitted by the detector) is 25 nanoseconds. Also, the number of bunches in a beam, currently 912, will also increase. The theoretical upper limit is 2808 bunches per beam.

Upgrading the LHC to a higher number of bunches per beam is a delicate process, since increase in the number of bunches dramatically increases the beam energy. Engineers have to be sure that not only is the LHC under no danger from the increased energy, the detectors function properly and the calibration remains true.

Take a bunch of protons. This may consist of a hundred billion protons (that’s one followed by 11 zeros), each separated by a distance much greater than the theoretical radius of protons. When such beams from opposite sides collide, the number of collisions is really small owing to the huge separations (the beams pass through each other mostly as ghosts). It’s the relatively small number of collisions that happen that are important.

Next, luminosity of a beam:

The next milestone achieved by the LHC early today was the attainment of a huge luminosity of 1033. But what does this really mean? Roughly, this corresponds to the collision rate, but it is not exactly so! It refers to the probability of collisions rather than the rate of actual collisions happening. The difference is a subtle and important one. Physicists call this the ‘cross-section’ of the process. Think of cross-section as an area (in fact, this is where the name comes from). The bigger the cross-section, the bigger the probability of a collisions happening. (Think of a door and a small slit in a postbox. If you randomly throw small rocks at each one from a good distance, the probability of hitting the door is much higher than that for hitting the mailbox slit. The door is said to have a higher ‘cross-section’.)

A Higgs event simulated at CMS, a detector at LHC, CERN

Each process has its own cross-section. For example, the cross-section for the production of a muon from an electron-positron collision is much higher that the same for the production of a Higgs from a proton-antiproton collision. Multiplying the cross-section with the luminosity gives the number of events to expect (call it, ‘expectation’) at that luminosity. (This is indeed different from cross-section, if you’re wondering. Cross-section is an inherent quantity, fixed for a certain process. Expectation depends on the number of particles in the beam being fired.)

Most protons in the LHC beams, as mentioned above, don’t collide at all and some collide only at glancing angles. The head-on collisions are the ones that produce the most exotic phenomenon (utilizing their full energy in the collision), and this is what interests scientists the most.

The highest luminosity, set last year, was 1032, with the theoretical highest being 1034. Currently, there is predicted about a 100 million collisions.

The LHC is expected to operate at 3.5 TeV this entire year set to hit 7 TeV in the next couple of years. Exciting physics is round the corner. Watch this space for more…

The “God Particle”: Higgs Boson Mystery Might Be Solved by 2012, Says CERN

The mystery of the Higgs boson, the so called God Particle, will be solved by 2012. This claim came from CERN a couple of days back. CERN spokesperson, Fabiola Gianotti, said:

By the end of 2012 we will either discover the Standard Model Higgs Boson, if it exists, or we will rule it out

Make or (almost) break:

This has caused quite a bit of excitement in the physics quarters, with people betting both ways, but leaning towards a successful search. The Higgs boson is supposed to endow all particles in the universe with mass. The mass of a particle depends on the strength of interaction with the Higgs field. Whereas a photon (particle of light) doesn’t interact with the field at all, an electron neutrino (a very light particle) interacts very weakly, while a proton (comparatively heavy) interacts much more strongly. The mechanism by which an interacting particle gets mass is called the Higgs mechanism, after the British physicist Peter Higgs, who first proposed it. Since then, the Higgs has been hot property in the particle physics arena, and has evoked strong interest outside it too. Probably, it is the most popular boson after the photon. The Higgs fits in nicely with the present Standard Model. The only problem is that it hasn’t been detected as yet.

A Simulated Higss event at LHC

If the Higgs boson were found, it would put an everlasting stamp of approval on the Standard Model. However, an unsuccessful search will not invalidate the Standard Model, as some people believe. There are many less known mechanisms not involving the Higgs, which describes how particles get mass.

The LHC:

The LHC was built with a primary aim of detecting the Higgs, especially with the Tevatron at Fermilab, the biggest collider before the LHC, shutting down in 2011. The enthusiasm to get at the Higgs is palpable within the science community and the desperation can be felt by the leakage of a memo at CERN a few days back. ATLAS, CERN has however invalidated the memo, which stated that a Higgs signature has been found.

The CMS Detector at the LHC, CERN

Smashing protons (and heavier nuclei) travelling at velocities close to that of light, scientists hope to recreate the conditions that supposedly existed right after the Big Bang. The LHC recently crossed the 7 TeV energy limit and also set a new record for beam intensity. This is, however, just half of its maximum capability. Scientists are busy acquiring and sifting through data of the order of terabytes, looking for a sign of the elusive Higgs and any of its heavier super-symmetric partners that the Standard Model predicts will have to exist, if the Higgs exists.

There will be an answer. Whether that answer will please Standard Model physicists is another question, and we will have to wait till 2012 for that.

Watch this space for more…

‘God Particle’ Rumor Dispelled: No Higgs Detected at LHC, CERN, Says ATLAS Report

The confirmation of the negative is finally here. A report has been released from ATLAS, CERN, which, after extensive analysis, has put to rest all rumors about any detection of the Higgs Boson the God Particle, which is supposed to endow all particles in the Universe with mass. We covered the news of the rumor here, urging readers to take the rumor with a healthy pinch of salt. The aforementioned report, surely enough and as we predicted, hasn’t found any Higgs.

The ATLAS Detector

The bottom line: The Higgs remains as elusive as ever, and physicists remain hopeful.

The news of this negative report was greeted with a little disappointment and lot of relief from the physics community, the latter emotion stemming from the fact that the Higgs was never expected at the position it was reported to have been found by the leaked memo. Many physicists were also appalled by the way a confidential memo was leaked a violation of both the ethical code of conduct and a personal breach of innate scientific spirit.

The present report (about the di-photon mass spectrum) from ATLAS has a lot more data points than the memo, and the data has been thoroughly analyzed. Find the report here. The key diagram in the report is given below.

Forget all the complications and the different plots. Note the monotonic step-like appearance of the plot. If the Higgs were detected, you’d find bumps in the graph (or at least one bump) localized at particular energies. If the memo were really right about the detection, there would have been a bump at 115 GeV (on the yellow band above the number 115′ marked on the horizontal axis), as the memo had reported the detection at this temperature. No irregularity is found, as is plainly visible to the naked eye.

There’s no real ambiguity anymore. At the risk of sounding repetitive, let’s say it once more: The Higgs has not been found.

If the Standard Model is correct, however, you should expect news of detection soon enough, especially when higher energy ranges are being probed. Watch this space…

Eureka Moment: New Particle Discovered At Tevatron?

This is big, really big! This may be the biggest news to hit the particle physics world in the the last 50 years. Scientists, analyzing the data collected at the Tevatron, Fermilab, have detected an anomaly that could well usher in a new dawn in theoretical physics and change the Standard Model as we know it now. The observation was a bump in the data, but in the ‘wrong’ place.

Tevatron
Tevatron

Scientists are excited about a Gaussian peak that has been observed on Wednesday, 6th April, centered at about 150 GeV with a spread of 2.5 GeV, corresponding to nearly 300 events.

Data Analysis:

Physicists are generally quite skeptical about any news of big breakthroughs. This ensures that the discoveries are really authentic. Most ‘discoveries’ are just mistakes in the code being used for data-analysis, or some human error or plain background fluctuations. All of these have to be ruled out. Coding errors can be ruled out by using many orthogonal samples of data, called ‘control sets’. Background fluctuations take a bit more effort, but routine analysis can eliminate it almost completely. A peak left after background elimination cannot be discarded.

Notwithstanding the fact that physicists are extremely skeptical, almost all major discoveries in high energy physics have been accidental. The key to such a discovery is rigorous analysis of data.

Is this the Higgs Boson?

The knee-jerk reaction was to suspect the discovery of the Higgs, the bosonic particle that is believed to endow all fundamental particles with mass. The Higgs boson, however, is ruled out, because if the Higgs could be produced at 140 GeV at a non-negligible rate, then we expect to see the characteristic decay jets, which would consist, mainly, of bottom quarks. However, such jets have not been observed, ruling out this possibility.

Higgs Event at CMS
Higgs Event at CMS, LHC

Is this a new force of nature?

It is too early to comment. The discovery of a new particle – a new boson – has to be confirmed. Only further investigation can answer this question.

What could fit the fill?

A new particle, which was coincidentally proposed in a paper a few days back, could fit the bill. The particle is called the Z’ boson, as compared to the Z boson. The Z’ boson is expected to decay via semi-leptonic (i.e. a mixture of hadrons and leptons) channels. Semi-leptonic jets have been observed. So, maybe, the Z’ is the ‘new’ particle.

Decay event for the Higgs
Higgs Decay

Confidence Levels:

The result now stands with a 3-sigma confidence level. This means that the possibility of ruling out the observation as a statistical fluctuation is less than 1 percent. Physicists look for a 6-sigma confidence level, which means that the doubts should reduce to less than 0.003%. To attain this level of confidence, scientists will need more sets of data and rigorous analysis of the same.

More data is on the way. As Prof. Nima Arkani-Hamed of the Institute for Advanced Studies, Princeton, notes, LHC should come up with much more data and copious events, if this is indeed a real discovery.

An Event at the Large Hadron Collider
A Collision Event at the Large Hadron Collider

One thing is for sure: this is exciting. If this is true, this is pure gold for particle physicists.

UPDATE: Fermilab rejects new particle discovery after extensive data analysis. Read here.