Beyond Higgs Boson





Technology, 24 Apr - 2015 ,

Beyond Higgs Boson
Credit: nanonewsnet.ru

The Large Hadron Collider (LHC) is the world's largest and most powerful particle collider, and the largest single machine in the world, built to test the predictions of different theories of particle physics and high-energy physics. First experimental ru

The Large Hadron Collider (LHC) is the world's largest and most powerful particle collider, and the largest single machine in the world, built to test the predictions of different theories of particle physics and high-energy physics. First experimental run of this machine has been successful in discovering Higgs Boson or GOD particle very much meeting the theoretical predictions of Standard Model of particle physics.  After a gap of almost two years, LHC is again has restarted with an aim to find answers to many unsolved problems beyond Higgs Boson or Standard Model like existence of dark matter, dark energy, dimension, many other elementary particles,  weak gravitation force etc.  towards super symmetry.  This article presents a brief introduction to LHC, finding of Higgs Boson, limitations of Standard model and possibilities beyond Higgs Boson.

Large Hadron Collider

The Large Hadron Collider (LHC) is the world's largest and most powerful particle collider, and the largest single machine in the world, built by the European Organization for Nuclear Research (CERN) from 1998 to 2008. The LHC was built in collaboration with over 10,000 scientists and engineers from over 100 countries, as well as hundreds of universities and laboratories. It lies in a tunnel 27 kilometres (17 mi) in circumference, as deep as 175 metres (574 ft) beneath the Franco-Swiss border near Geneva, Switzerland. It is also the longest machine ever built. Its aim is to allow physicists to test the predictions of different theories of particle physics and high-energy physics like the Standard Model, and particularly prove or disprove the existence of the theorized Higgs boson and of the large family of new particles predicted by supersymmetric theories. The discovery of a particle matching the Higgs boson was confirmed by data from the LHC in 2013. The LHC is expected to address some of the unsolved questions of physics, advancing human understanding of physical laws. It contains seven detectors, each designed for certain kinds of research. As of 2015, the LHC remains the largest and most complex experimental facility ever built.

Standard Model

The Standard Model describes how the basic building blocks that make up atoms and the forces of nature interact. The aim of the various theories of physics is to explain how the Universe was formed and how the bits that make it up work. One of the most successful of these theories is called the "Standard Model". It explains how the world of the very, very small works. Physicists have found things are quite different when they study the goings on at scales that are even smaller than the size of an atom. By doubling the energy of the LHC, it will enable them to discover new characters in the wonderful and mysterious tale of how the Universe works and came to be. Scientists want a glimpse into a world never seen before. By smashing atoms harder than they have been smashed before physicists hope to peel back another veil of reality.  With the discovery of the sub-atomic world's biggest celeb of all, the Higgs boson, scientists have now detected all the particles predicted by the Standard Model: a theory that beautifully explains how the Universe works in intricate detail.

Discovery of Higgs Boson

Physicists hope that the LHC will help answer some of the fundamental open questions in physics, concerning the basic laws governing the interactions and forces among the elementary objects, the deep structure of space and time, and in particular the interrelation between quantum mechanics and general relativity, where current theories and knowledge are unclear or break down altogether. Data is also needed from high energy particle experiments to suggest which versions of current scientific models are more likely to be correct – in particular to choose between the Standard Model and Higgsless models and to validate their predictions and allow further theoretical development. Many theorists expect new physics beyond the Standard Model to emerge at the TeV energy level, as the Standard Model appears to be unsatisfactory. CERN scientists estimated that, if the Standard Model is correct, several Higgs bosons would be produced every minute, and that over a few years enough data to confirm or disprove the Higgs boson unambiguously and to obtain sufficient results concerning supersymmetric particles would be gathered to draw meaningful conclusions. Some extensions of the Standard Model predict additional particles, such as the heavy W' and Z' gauge bosons, which may also lie within reach of the LHC to discover.

 

The first physics results from the LHC, involving 284 collisions which took place in the ALICE detector, were reported on 15 December 2009. The results of the first proton–proton collisions at energies higher than Fermilab's Tevatron proton–antiproton collisions were published by the CMS collaboration in early February 2010, yielding greater-than-predicted charged-hadron production. After the first year of data collection, the LHC experimental collaborations started to release their preliminary results concerning searches for new physics beyond the Standard Model in proton-proton collisions. No evidence of new particles was detected in the 2010 data. As a result, bounds were set on the allowed parameter space of various extensions of the Standard Model, such as models with large extra dimensions, constrained versions of the Minimal Supersymmetric Standard Model, and others. On 24 May 2011, it was reported that quark–gluon plasma (the densest matter besides black holes) has been created in the LHC. Between July and August 2011, results of searches for the Higgs boson and for exotic particles, based on the data collected during the first half of the 2011 run, were presented in conferences.  In a conference it was reported that, despite hints of a Higgs signal in earlier data, ATLAS and CMS exclude with 95% confidence level (using the CLs method) the existence of a Higgs boson with the properties predicted by the Standard Model over most of the mass region between 145 and 466 GeV. The searches for new particles did not yield signals either, allowing to further constrain the parameter space of various extensions of the Standard Model, including its supersymmetric extensions. On 13 December 2011, CERN reported that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 115–130 GeV. Both the CMS and ATLAS detectors have also shown intensity peaks in the 124–125 GeV range, consistent with either background noise or the observation of the Higgs boson. On 22 December 2011, it was reported that a new particle had been observed, the χb (3P) bottomonium state. On 4 July 2012, both the CMS and ATLAS teams announced the discovery of a boson in the mass region around 125–126 GeV, with a statistical significance at the level of 5 sigma. This meets the formal level required to announce a new particle which is consistent with the Higgs boson, but scientists were cautious as to whether it is formally identified as actually being the Higgs boson, pending further analysis. On 8 November 2012, the LHCb team reported on an experiment seen as a "golden" test of supersymmetry theories in physics by measuring the very rare decay of the Bs meson into two muons (Bs0 → μ+μ). The results, which match those predicted by the non-supersymmetrical Standard Model rather than the predictions of many branches of supersymmetry, show the decays are less common than some forms of supersymmetry predict, though could still match the predictions of other versions of supersymmetry theory. The results as initially drafted are stated to be short of proof but at a relatively high 3.5 sigma level of significance. The result was later confirmed by the CMS collaboration.

Limitations of Standard Model

Physicists hope it could lead to discoveries that could potentially represent the biggest revolution in physics since Einstein's theories of relativity. Physicists are frustrated by the existing Standard Model of particle physics as shown in figure. It describes 17 subatomic particles, including 12 building blocks of matter and 5 "force carriers" - the last of which, the Higgs boson, was finally detected by the LHC in 2012. LHC's four big experiments will soon recommence their work, slamming protons together and quantifying the fallout to make a big, unknown discovery. For a long time physicists thought that their Standard Model theory could explain almost everything. Then came two phenomena that showed that it explained hardly anything. First was the observation that galaxies are rotating much more quickly than they should. The faster a galaxy rotates the more material it contains. The observations suggested that they contain five times more material than could be detected. This invisible material has been called "dark matter" which physicists believe accounts for a quarter of the Universe. Second was the observation that galaxies were accelerating apart from each other driven by an even more mysterious force that the researchers who discovered it called "dark energy". So all in all the Standard Model, brilliant though it is at explaining how our tiny corner of the cosmos works can't account for how the remaining 95% of the Universe works.

It's become particularly pressing, because with Run One and the discovery of the Higgs, they've discovered everything that the existing theory predicts. In order to explain several baffling properties of the universe, things beyond the Standard Model have been proposed - but never directly detected. These include dark energy, the all-pervading force suggested accounting for the universe expanding faster and faster. And dark matter - the "web" that holds all visible matter in place, and would explain why galaxies spin much faster than they should, based on what we can see. A theory called super symmetry proposes additional particles, as yet unseen, that might fill in some of these gaps. But no experiment, including the LHC, has yet found evidence for anything "supersymmetrical". Even the familiar and crucial force of gravity is nowhere in the Standard Model. By taking matter to states we have never observed before - the LHC's collisions create temperatures not seen since moments after the Big Bang - physicists hope to find something unexpected that addresses some of these questions. Debris from the tiny but history-making smash-ups might contain new particles, or tell-tale gaps betraying the presence of dark matter or even hidden dimensions. That is what physicists are hoping for. With the Large Hadron Collider set to double its energy, physicists hope that they will discover weirder and even more wonderful particles that will point the way to a new more complete theory of sub-atomic physics. Researchers will also be looking to find particles that are manifestations of extra-dimensions that we cannot detect but are predicted in some theories that extend the Standard Model to incorporate gravity.

Beyond Higgs Boson

The Large Hadron Collider has restarted recently in 2015 after a gap of two years, with protons circling the machine's 27km tunnel for the first time since 2013. Particle beams have now travelled in both directions, inside parallel pipes, at a whisker below the speed of light. Actual collisions will not begin for at least another month, but they will take place with nearly double the energy the LHC reached during its first run. Scientists hope to glimpse a "new physics" beyond the Standard Model. But the most important step is still to come when to increase the energy of the beams to new record levels. The protons are injected at a relatively low energy to begin with. But over the coming months, engineers hope to gradually increase the beams' energy to 13 trillion electronvolts: double what it was during the LHC's first operating run. The experiment teams have already detected "splashes" of particles, which occur when stray protons hit one of the shutters used to keep the beam on-track. If this happens in part of the pipe near one of the experiments, the detectors can pick up some of the debris.

Issues possibly to be explored by LHC collisions include:

·         Are the masses of elementary particles actually generated by the Higgs mechanism via electroweak symmetry breaking? That is the existence of the elusive Higgs boson.

·         Is supersymmetry, an extension of the Standard Model and Poincaré symmetry, realized in nature, implying that all known particles have supersymmetric partners?

·         Are there extra dimensions, as predicted by various models based on string theory, and can we detect them?

·         What is the nature of the dark matter that appears to account for 27% of the mass-energy of the universe?

·         It is already known that electromagnetism and the weak nuclear force are different manifestations of a single force called the electroweak force. The LHC may clarify whether the electroweak force and the strong nuclear force are similarly just different manifestations of one universal unified force, as predicted by various Grand Unification Theories.

·         Why is the fourth fundamental force (gravity) so many orders of magnitude weaker than the other three fundamental forces?

·         Are there additional sources of quark flavour mixing, beyond those already present within the Standard Model?

·         Why are there apparent violations of the symmetry between matter and antimatter?

·         What are the nature and properties of quark–gluon plasma, believed to have existed in the early universe and in certain compact and strange astronomical objects today?

Conclusion

When LHC discovered the famous Higgs boson, and confirmed its position in the Standard Model of physics, that was an extraordinary achievement in its own right. It proved the existence of an invisible process that performs the fundamentally important role of giving all other particles their mass or substance. It is with the restart of LHC experiment i.e., the mother of all physics experiments, ready after its two-year upgrade to explore uncharted corners of the sub-atomic realm. It will be a huge step on a journey towards understanding how the universe works, and there is much more to come. The next collisions of protons may reveal something about the majority of matter that exists but has yet to be seen - the stuff known as dark matter. They may uncover evidence for the weird notion that there are extra dimensions, or hordes of previously unseen particles that form pairs with the ones we know about. Any of this would open our eyes to a new way of perceiving the fabric of everything we see and touch - how it is made and what holds it together.  A new insight can open a door and it's then up to other researchers to choose whether to venture through it, sometimes decades later, to develop practical applications.

Acknowledgement: The use of information retrieved through various references/sources of internet in this article is highly acknowledged.

 


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