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Roger's Equations

This blog is all about science and technology (with occasional math thrown in for fun). The goal of this blog is to try and pass on the sense of excitement and wonder I feel when I read about these topics. I hope you enjoy the posts.

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The Annoyingly Accurate Standard Model

Posted May 19, 2015 2:31 PM by Bayes

A Little Too Perfect

Several years ago, when the LHC was just (finally) starting up, there was a lot of excitement in the particle physics community with regards to what it might find. New unexpected particles? New unexpected particle decays? Particle decays not behaving exactly as predicted? All would point to theories beyond the Standard Model.

A few years later, no new unexpected particles, no new unexpected particle decays, and not even particle decays behaving oddly. In fact, if anything, the surprise delivered by the LHC so far is that the Standard Model is far more robust than expected. Bad news for Supersymmetry (SUSY) and other extensions of the theory.

Although the Standard Model is theoretically self-consistent and has demonstrated huge and continued successes in providing experimental predictions, it does leave some phenomena unexplained and it falls short of being a complete theory of fundamental interactions. It does not incorporate the full theory of gravitation as described by general relativity, or account for the accelerating expansion of the universe (as possibly described by dark energy). The model does not contain any viable dark matter particle that possesses all of the required properties deduced from observational cosmology. It also does not incorporate neutrino oscillations (and their non-zero masses).

So you see, the robustness of the Standard Model is a bit of a let down for physicists looking for clues how to expand upon it.

What is the Standard Model?

Here is a basic overview (5 min in length)***Since this video has been made the Higgs Boson has been verified by the LHC***

Basically the Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, as well as classifying all the subatomic particles known. It was developed throughout the latter half of the 20th century, as a collaborative effort of scientists around the world. The current formulation was finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, discoveries of the top quark (1995), the tau neutrino (2000), and more recently the Higgs boson (2013), have given further credence to the Standard Model. Because of its success in explaining a wide variety of experimental results, the Standard Model is sometimes regarded as a "theory of almost everything".

Here is a basic overview of the Standard Model

Here is a more detailed explanation of the Standard Model

***Some recent Articles Regarding Further Verifications of the Standard Model***

Two Large Hadron Collider experiments first to observe rare subatomic process

Two experiments at the Large Hadron Collider at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, have combined their results and observed a previously unseen subatomic process. As published in the journal Nature this week, a joint analysis by the CMS and LHCb collaborations has established a new and extremely rare decay of the Bs particle (a heavy composite particle consisting of a bottom antiquark and a strange quark) into two muons. Theorists had predicted that this decay would only occur about four times out of a billion, and that is roughly what the two experiments observed.

"It's amazing that this theoretical prediction is so accurate and even more amazing that we can actually observe it at all," said Syracuse University Professor Sheldon Stone, a member of the LHCb collaboration. "This is a great triumph for the LHC and both experiments." LHCb and CMS both study the properties of particles to search for cracks in the Standard Model, our best description so far of the behavior of all directly observable matter in the universe. The Standard Model is known to be incomplete since it does not address issues such as the presence of dark matter or the abundance of matter over antimatter in our universe. Any deviations from this model could be evidence of new physics at play, such as new particles or forces that could provide answers to these mysteries.

Article Continues Here

IceCube neutrinos do come in three flavours after all

High-energy neutrinos detected by the IceCube experiment in Antarctica are equally distributed among the three possible neutrino flavours, according to two independent teams of physicists. Their analyses overturn a preliminary study of data, which suggested that the majority of the particles detected were electron neutrinos. The latest result is in line with our current understanding of neutrinos, and appears to dash hopes that early IceCube data point to "exotic physics" beyond the Standard Model.

Located at the Amundsen-Scott South Pole Station, the IceCube Neutrino Observatory is a large array of photodetectors buried in ice. In late 2013 IceCube revealed that it had captured the first signals from neutrinos with extremely high energies, which suggests that the particles came from outside of our galaxy. While neutrinos generated inside the Sun and by cosmic rays colliding with the Earth's atmosphere have been detected for many years, neutrinos from much farther away had remained elusive. As a result, the discovery was named the Physics World Breakthrough of the Year in 2013.

Article Continues Here

***Here's an article on how a possible extension of the Standard Model, Supersymmetry, is failing to show up in the LHC experimental results.***

Natural SUSY's last stand

Either Supersymmetry will be found in the next years of research at the Large Hadron Collider, or it isn't exactly what theorists hoped it was.

One of the big questions scientists are asking with experiments at the Large Hadron Collider is this: Does every fundamental particle we know about have a hidden partner that we have yet to meet? A popular set of theories predict that they do.The first run of the LHC came and went without any of these partner particles turning up. But a recent paper shows that the real test of the theories that predict their existence could happen during the next run, when particles will collide at higher energies than ever before.

These theoretical partner particles come from the idea of Supersymmetry, or SUSY, a mathematical framework developed over the past 40 years that could answers questions such as: Are all of the forces we know just parts of a single, unified force? How is the Higgs boson so light? What is dark matter? Is the world made up of the tiny, vibrating strings described by string theory? A key aspect of SUSY is that each of the dozens of particles in the Standard Model of particle physics must have a partner, called a superparticle or sparticle. Scientists think all of these sparticles must ultimately decay into a light, stable particle. If they are light enough, supersymmetric particles that interact through the strong force, such as supersymmetric quarks (squarks) or supersymmetric gluons (gluinos), could be produced at large rates at the LHC.

Article Continues Here


The Standard Model is a robust theory, but it fails to explain a number of phenomenon and therefore will need to be extended. Up until now the LHC has failed to find any clues with regard to how it should be extended. Certain strong theoretical candidates, such as Supersymmetry are failing to deliver, with their predictions of new particles or decays not turning up in the LHC data. If the LHC doesn't turn something up soon, theoretical particle physicists need to go back to the drawing board and rethink how to extend the Standard Model.


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Re: The Annoyingly Accurate Standard Model

05/20/2015 10:12 AM

Hi Roger,

Great article and great links. It's exciting stuff. The Higgs boson discovery seemed a little "muddy" but they ultimateley declared it found. It would be great to find some real proof of dark matter or some viable alternative that could be proven.


“I would rather have questions that can't be answered than answers that can't be questioned.” - Richard Feynman
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Re: The Annoyingly Accurate Standard Model

05/21/2015 4:15 AM

I am aware that I exist? Is it a biological structure? Or is it a part of the essence of what matter is? Should we be part of the standard model?

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