Posts Tagged‘lhc’

Beyond the LHC: AWAKE.

The Large Hadron Collider has proven to be the boon to particle physics that everyone had imagined to be but it’s far from done yet. We’ll likely be getting great data out of the LHC for a couple decades to come, especially with the current and future upgrades that are planned. However it has its limit and considering the time it took to build the LHC many are looking towards what will replace it when the time comes. Trouble is that current colliders like the LHC can only get more powerful by being longer, something which the LHC struggled with at its 27KM length. However there are alternatives to current particle acceleration technologies and one of them is set to be trialled at the LHC next year.

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The experiment is called AWAKE and was approved by the CERN board back in 2013. Recently however it was granted additional funding in order to pursue its goal. At its core the AWAKE experiment is a fundamentally different approach to particle acceleration, one that could dramatically reduce the size of accelerators. It won’t be the first accelerator of this type to ever be built, indeed proof of concept machines already exist at over a dozen facilities around the world, however it will be the first time CERN has experimented with the technology. All going well the experiment is slated to see first light sometime towards the end of next year with their proof of concept device.

Traditional particle colliders work on alternating electric fields to propel particles forward, much like a rail gun does with magnetic fields. Such fields place a lot of engineering constraints on the containment vessels with more powerful fields requiring more energy which can cause arcing if driven too high. To get around this particle accelerators typically favour length over field strength, allowing the particles a much longer time to accelerate before collision. AWAKE however works on a different principle, one called Plasma Wakefield Acceleration.

In a Wakefield accelerator instead of particles being directly accelerated by an electric field they’re instead injected into a specially constructed plasma. First a set of charged particles, or laser light, is sent through the plasma. This then sets off an oscillation within the plasma creating alternating regions of positive and negative charge. Then when electrons are injected into this oscillating plasma they’re accelerated, chasing the positive regions which are quickly collapsing and reforming in front of them. In essence the electrons surf on the oscillating wave, allowing them to achieve much greater velocities in a much quicker time. The AWAKE project has a great animation of the experiment here.

The results of this experiment will be key to the construction of future accelerators as there’s only so much further we can go with current technology. Wakefield based accelerators have the potential to push us beyond the current energy collision limits, opening up the possibility of understanding physics beyond our current standard model. Such information is key to understanding our universe as it stands today as there is so much beauty and knowledge still out there, just waiting for us to discover it.

 

Latest LHC Results Suggest Non-Standard Model Physics Afoot.

If you cast your mind back to your high school science days you’ll likely remember being taught certain things about atoms and what they’re made up of. The theories you were taught, things like the strong/weak forces and electromagnetism, form part of what’s called the Standard Model of particle physics. This model was born out of an international collaboration of many scientists who were looking to unify the world of subatomic physics and, for the most part, has proved extremely useful in guiding research. However it has its limitations and the Large Hadron Collider was built in order to test them. Whilst the current results have largely supported the Standard Model there is a growing cache of evidence that runs contrary to it, and the latest findings are quite interesting.

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The data comes out of the LHCb detector from the previous run that was conducted from 2011 to 2012. The process that they were looking into is called B meson decay, notable for the fact that it creates a whole host of lighter particles including 2 leptons (called the tau lepton and the muon). These particles are of interest to researchers as the Standard Model makes a prediction about them called Lepton Universality. Essentially this theory states that, once you’ve corrected for mass, all leptons are treated equally by all the fundamental forces. This means that they should all decay at the same rate however the team investigating this principle found a small but significant difference in the rate in which these leptons decayed. Put simply should this phenomena be confirmed with further data it would point towards non-Standard Model particle physics.

The reason why scientists aren’t decrying the Standard Model’s death just yet is due to the confidence level at which this discovery has been made. Right now the data can only point to a 2σ (95%) confidence that their data isn’t a statistical aberration. Whilst that sounds like a pretty sure bet the standard required for a discovery is the much more difficult 5σ level (the level at which CERN attained before announcing the Higgs-Boson discovery). The current higher luminosity run that the LHC is conducting should hopefully provide the level of data required although I did read that it still might not be sufficient.

The results have gotten increased attention because they’re actually not the first experiment to bring the lepton universality principle into question. Indeed previous research out of the Stanford Linear Accelerator Center’s (SLAC) BaBar experiment produced similar results when investigating lepton decay. What’s quite interesting about that experiment though is that it found the same discrepancy through electron collisions whilst the LHC uses higher energy protons. The difference in method with similar results means that this discrepancy is likely universal, requiring either a new model or a reworking of the current one.

Whilst it’s still far too early to start ringing the death bell for the Standard Model there’s a growing mountain of evidence that suggests it’s not the universal theory of everything it was once hoped to be. That might sound like a bad thing however it’s anything but as it would open up numerous new avenues for scientific research. Indeed this is what science is built on, forming hypothesis and then testing them in the real world so we can better understand the mechanics of the universe we live in. The day when everything matches our models will be a boring day indeed as it will mean there’s nothing left to research.

Although I honestly cannot fathom that every occurring.

Creating Dark Matter in the Large Hadron Collider.

It’s hard to understate the significance of the science that has been done because of the Large Hadron Collider. Whilst it’s famously known for discovering the Higgs-Boson, the particle which gives all other particles mass, it has a long list of achievements outside of that singular event. What makes these discoveries even more interesting is that the LHC has been operating at something of a disadvantage since it was first turned on over 6 years ago, operating at around half the potential energy it was capable of. Shortly after the discovery of the Higgs Boson the scientists and engineers at CERN have been working to bring it up to full capacity and with it the potential for some even more radical discoveries.

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The doubling of the collision energy increases the potential for the LHC to generate even more exotic particles than it has previously, ones which can give us insights into some of the most perplexing mysteries in particle physics to date. One such source of intrigue is how our universe, which is composed of nearly entirely matter, came to be that way. Another seeks to explain why the universe seems to be riddled with matter that’s not directly observable but is seen through its gravitational effects throughout the universe. These, and many other questions, have potential to find answers in the newly upgraded LHC which is slated to come online this year.

In the beginning, the beginning of everything according to scientific theory, there existed both equal quantities of matter and antimatter. Upon annihilation these two entities should have completely destroyed each other, leaving behind a wake of energy with no matter to speak of. However casual observation will show that our world, and the rest of the universe, is dominated by matter. This strange preference for matter (dubbed the CP Violation) has perplexed scientists for decades however the newly upgraded LHC has the potential to shed some light on where the Universe’s strange preference comes from. The LHCb detector focuses on the decay of the Beauty Quark, a fundamental particle that decays in all manner of strange ways when created in a collider. Studying these decays could grant us insight into where the CP violation comes from and why we live in a matter dominated universe.

However what’s far more interesting (for me at least) is that the LHC could have the potential to generate dark matter, the highly pervasive as-of-yet unobserved substance that binds galaxies together via its gravitational influence. There’s numerous theories that posit dark matter being made up of WIMPs (Weakly Interacting Massive Particles) which could potentially be generated in the LHC. It’s highly unlikely that we’ll be able to detect them directly, their very nature means that they’re far more likely to simply pass through the detectors, however should we generate them their signature will be left on the reactions. Essentially we’ll be looking for a reaction that’s missing energy and then seeing if that can be explained by a WIMP being generated. Should we find that we’ll have a solid basis to further investigate this elusive form of matter, furthering our understanding of just what makes up our universe.

It’ll likely be another few years before we hear any further news from the LHC as it’s going to take time to generate the data and even longer to sift through it to find the reactions we’re looking for. However I’m very confident that the results will forever change the scientific landscape as either confirmation of current theories or evidence against them will provide dozens of more avenues for further research. That, to me, is the beauty of science, the never ending search for answers that inevitably lead to more questions, starting the process of discovery all over again.

LHC Powers Up, Earth Still Here.

Yesterday marked a huge achievement for CERN and the team working on the Large Hadron Collider. After almost a year of delays after a catastrophic incident that damaged 2 sectors and caused 6 tons of helium to be lost they have successfully circulated 2 beams around the LHC. This of course let them test the entire reason they built the thing in the first place, smashing things together:

Geneva, 23 November 2009. Today the LHC circulated two beams simultaneously for the first time, allowing the operators to test the synchronization of the beams and giving the experiments their first chance to look for proton-proton collisions. With just one bunch of particles circulating in each direction, the beams can be made to cross in up to two places in the ring. From early in the afternoon, the beams were made to cross at points 1 and 5, home to the ATLAS and CMS detectors, both of which were on the look out for collisions. Later, beams crossed at points 2 and 8, ALICE and LHCb.

“It’s a great achievement to have come this far in so short a time,” said CERN1Director General Rolf Heuer. “But we need to keep a sense of perspective – there’s still much to do before we can start the LHC physics programme.”

Now we all know the hype around the LHC and how it has the “potential” to create a black hole that will destroy the earth. Whilst its been debunked many times over I’d just like to re-iterate it here, we’re not in any danger from the LHC or the particles it may create. Even though the energy in these collisions seems huge it is in fact quite small, about that of clapping your hands or a flying mosquito, concentrated into a very tiny space. Even if a black hole were to be created it would either evaporate almost instantly due to hawking radition or blaze through the earth where it would then take about 10 octillion (that’s a 1 followed by 28 zeros) to consume the entire earth. I’d be worried about the universe spontaneously collapsing in on itself than a small black hole created by the LHC consuming the earth.

So many people know what the LHC is but not what it was designed for. It does have several goals listed although there’s really only one that gets me all giddy:

  • Is the Higgs mechanism for generating elementary particle masses via electroweak symmetry breaking indeed realised in nature? It is anticipated that the collider will either demonstrate or rule out the existence of the elusive Higgs boson(s), completing the Standard Model.
  • Is supersymmetry, an extension of the Standard Model and Poincaré symmetry, realised in nature, implying that all known particles have supersymmetric partners? These may clear up the mystery of dark matter.
  • Are there extra dimensions, as predicted by various models inspired by string theory, and can we detect them?

The Higgs-Boson is an elusive beast as its the only particle in the standard model that has only been inferred theoretically, it has never been observed. Its discovery would round out the model and serve as a solid basis for the holy grail of physics, a theory for everything. Although this would be all well and good (and really, it is to be expected that we will see a Higgs-Boson) it would probably be more significant if the exact opposite happened. The greatest moments in science have stemmed from carefully prepared experiments behaving in ways that no one predicted, challenging our current thinking and forcing us to look back at our previous work. Whilst I will sing the LHCs praises from the rooftops should they find the Higgs-Boson you can be sure that I’ll be cackling with a mad sense of glee if they prove it does not exist.

While we’re still a ways off from doing real hard science with the LHC it’s great to see them hitting such a significant milestone. It’s hard to believe that the project, which has been going for over 15 years, is on the cusp of performing some of the most radical science to date. Really its a testament to what humanity is capable of and how far we’re willing to go just to satisfy our curiosity.