Showing category "Particle Physics" (Show all posts)

Sterile Neutrinos

Posted by on Tuesday, July 10, 2018, In : Particle Physics 
There has been a lot of discussion lately of the possible existence of sterile neutrinos in the Universe, due in large part to a few papers in the recent weeks making claims of possible signs of detection in one of the bigger neutrino observatories. And although these results are preliminary, with the formal announcements coming later this week, and may show no clear sign of anything other than a statistical fluctuation, the theory of sterile neutrinos is still quite interesting to the theore...
Continue reading ...
 

Feynman Diagrams

Posted by on Friday, May 11, 2018, In : Particle Physics 
Among physicists, there is a popular story told and retold about a pair of lectures that were given at a conference in 1948 that demonstrates the brilliance of Richard Feynman. How much of it is true and how much has been embellished to build up the legend is unknown, but it is still an entertaining and information anecdote.

Since the development of quantum mechanics in the 1920s and 1930s there had been an unsolved problem regarding the proper treatment of particle interactions. The laws of q...
Continue reading ...
 

Path Integrals

Posted by on Friday, May 11, 2018, In : Particle Physics 
In honour of the 100th anniversary of the birth of Richard Feynman, I will today present a very basic overview of one of the great ideas of modern physics which was developed and popularized by Feynman. And the first part of that theory is the path integral formulation of quantum mechanics.

By now quantum mechanics is firmly established as a confirmed and proven theory of nature. Even popular society has come to embrace some of the stranger aspects of quantum theory (though unfortunately they ...

Continue reading ...
 

Constraining the Seesaw

Posted by on Friday, September 29, 2017, In : Particle Physics 
A few days ago I wrote a brief review of the Seesaw Model of particle physics. Being a theorist, I forgot to mention that the motivation for that review was a new set of results from the experimental community that constrains such models. And so I thought that today I would give a few details on these new results.

In the model I reviewed, known as a Type-I model, each of the species of neutrino that are part of the Standard Model are partnered with a second, very heavy neutrino that provides a...
Continue reading ...
 

The Seesaw Model

Posted by on Tuesday, September 26, 2017, In : Particle Physics 
Neutrinos are very mysterious particles. They do not carry electric or magnetic charge, and so they do not interact very much with anything else. In fact we are constantly being showered with neutrinos from space that fly straight through us without interaction, and in fact straight through the entire Earth without even being slowed down. They are so difficult to detect that the weak nuclear decays that generate them were at first thought to be violating energy and momentum conservation since...
Continue reading ...
 

The HL-LHC

Posted by on Thursday, September 14, 2017, In : Particle Physics 
As students around the world return to school, or start college, or begin new coursework and training of other kinds, particle physicists are also starting new things in the form of new data runs from the Large Hadron Collider. The LHC has already produced evidence of the Higgs boson, and added further constraints to many other theories of nature. The next data run could easily find evidence of dark matter, dark energy, or even hidden higher dimensions in the Universe.

However the topic of tod...
Continue reading ...
 

The Antihydrogen Spectrum

Posted by on Thursday, August 3, 2017, In : Particle Physics 
Another interesting result from the Canadian led team at the ALPHA collaboration, with a paper publish today in Nature in which they present the hyperfine spectrum of anti-hydrogen.

Anyone who has the least interest in either physics or astronomy is aware of atomic spectra. Over a century ago scientists discovered that each chemical element emits a signature series of wavelengths of light, which is unique to that element. From the colour of emitted light we can identify each element that is p...
Continue reading ...
 

Just A Blip

Posted by on Friday, August 5, 2016, In : Particle Physics 
More disappointing news from the experimental physics community today as the teams that operate the Large Hadron Collider have formally announced that there is no new particle at 750 GeV.

Many people will remember that at the end of last year the particle physics community was buzzing over a new and unexpected result from the LHC. Their data showed something being produced at 750 GeV and decaying primarily into two photons. This did not match with any known particles, and immediately produced ...
Continue reading ...
 

No Luck For LUX

Posted by on Friday, July 22, 2016, In : Particle Physics 
There is some disappointing news for the particle physics/astrophysics/cosmology research community this week as the Large Underground Xenon experiment has completed its data run and found no clear signals of any new particles. Due to its long run and its sensitivity, many had hoped for a significant dark matter detection, but it simply isn't there.

As many of my readers already know, our best models of the Universe include a mysterious form of matter known as dark matter. In fact it is believ...
Continue reading ...
 

Three Families of Fermions

Posted by on Saturday, January 9, 2016, In : Particle Physics 
In my end of year review article a couple of weeks ago I made reference to the possible discovery of a Weyl fermion. Since then a few people have asked me what a Weyl fermion is and how it differs from a regular fermion. In fact there are three common types of fermions, and I thought I would give a brief review of them today.

Let me begin by explaining what fermions are. When quantum mechanics was being developed in the early 20th century, it was discovered that particles could exist in two po...
Continue reading ...
 

The Diphoton Excess

Posted by on Tuesday, December 22, 2015, In : Particle Physics 
The latest data from the Large Hadron Collider has now been released, and it contains a most interesting new result. Perhaps not on par with the Higgs boson discovery, or any of the hundreds of predictions of the theoretical physics community, but still enough to make the research community sit up and take notice.

While most of the data is little more than a confirmation of existing knowledge, there is a new result at 750 GeV. The two detectors at the LHC - CMS and Atlas - have both found an e...
Continue reading ...
 

Nobel Prize 2015

Posted by on Tuesday, October 6, 2015, In : Particle Physics 
The Nobel Prize committee has spoken, and the recipient for the 2015 Nobel Prize in Physics is Takaaki Kajita and Arthur B. McDonald for their discovery of neutrino oscillations! Congratulations to both the winners themselves and to their teams who made it possible.

By now the story of the neutrino oscillation is well known, at least in academic circles, and so it is fitting that the actual discovery should receive an award. 

The story begins in 1930, when physicists were puzzled at beta decays...
Continue reading ...
 

Hints of a New Force?

Posted by on Monday, September 14, 2015, In : Particle Physics 
A friend of mine forwarded a popular physics article to me this morning titled "A Crack In The Standard Model". My first thought was that it was either a crackpot article that wasn't worth reading, or that it was the biggest breakthrough of the last thirty years. As it turned out, it was neither.

The Standard Model of Particle Physics was developed through the 20th century, as new particles and new forces were discovered. However the last new particle discovered in an experiment was the top qu...
Continue reading ...
 

ALICE's Antinuclei

Posted by on Monday, August 17, 2015, In : Particle Physics 
The ALICE experiment has released some interesting new data today, and while there are no great new discoveries in these latest results, they have improved our knowledge of a basic symmetry of nature. 

Nearly a century ago physicists were excited by the early success of quantum mechanics and were trying to construct a relativistic theory of quantum mechanics. In the midst of this work, British physicist Paul Dirac developed a new equation that described the properties of atoms and smaller part...

Continue reading ...
 

Pentaquarks

Posted by on Tuesday, July 14, 2015, In : Particle Physics 
On the same day that the New Horizon probe makes history as the first man-made object to do a fly-by of the planet Pluto, the LHCb experiment is claiming a fascinating new discovery on the subatomic scales. According to results announced today, they seem to have produced and detected a pentaquark system.

Allow me to begin by (briefly) reviewing the theory of quarks. According to the Standard Model of particle physics, there are six flavours of quark as well as a matching set of six anti-quark ...
Continue reading ...
 

Monopole Quest

Posted by on Wednesday, July 1, 2015, In : Particle Physics 
Over the past few years there have been many opportunities for average citizens to participate in scientific research, whether by classifying galaxies or hunting for supernovae, or watching the oceans and the grasslands for wildlife. However until recently there have been few opportunities to work with the particle physics community.

However a new project has just started through the zooniverse website, in which users can help the MoEDaL (Monopole and Exotics Detector at LHC) team to hunt for...
Continue reading ...
 

Koide Formula

Posted by on Friday, May 8, 2015, In : Particle Physics 
A few months ago I wrote an article on the Standard Model of particle physics, and made passing reference to the little know Koide relationship of lepton masses. A few of you wrote to ask me about this formula - which proves that some of you did not read the detailed review of it that I wrote a few years ago :-)    (In fairness though, that article was on another website which may have since been de-activated by its managers.)

Let me begin by reviewing the leptons. One of the first subatomic p...
Continue reading ...
 

Project X

Posted by on Sunday, April 19, 2015, In : Particle Physics 
With the LHC coming back on line, and starting on its next run of data collection, it seems like a good time to review another particle accelerator that is still in the developmental stage, and to advocate for more investment in the fundamental sciences.

Most people with a serious interest in science in general and particle physics in particular have heard of Fermilab. They were the lab that discovered many of the fundamental particles of nature. And they came close to discovering the Higgs bo...
Continue reading ...
 

The LHC Is Resurrected!

Posted by on Sunday, April 5, 2015, In : Particle Physics 
Today is the day when the greatest we have ever known has been resurrected, to bring us into a bright new world and new understanding. That's right - the Large Hadron Collider has been successfully restarted after a two year upgrade, and is once more ready to explore the world of subatomic particle physics!

The LHC was built through the 2000s, and started up in 2008 only to have a major meltdown almost immediately. It was repaired and restarted the following year, and started hunting the Higgs...
Continue reading ...
 

The Three Generations...

Posted by on Friday, March 20, 2015, In : Particle Physics 
Earlier this week I wrote an opinion piece about the difficulty and possible impossibility of a dedicated but untrained physicist discovering a revolutionary new theory or phenomenon in modern physics. In that article I made reference to several interesting open problems in modern physics, and since then several people have asked me to explain these in more detail. Today's article is the second in this mini-series, and is actually a collection of problems.

For at least thirty years, all of par...
Continue reading ...
 

Two New Baryons

Posted by on Wednesday, November 19, 2014, In : Particle Physics 
More news from the particle physics community with the announcement by physicists at the Large Hadron Collider that they have produced and detected two new particles which have never been seen before. (It should be noted though that these particles have existed before in nature, produced by high energy cosmic rays in the atmosphere, but they decay too quickly to be observed and studied)

However before the news media starts writing headlines, it should also be made clear that this is a minor an...
Continue reading ...
 

A Comment on the Higgs

Posted by on Thursday, November 13, 2014, In : Particle Physics 
In the last few days, there have been several news articles in the popular media suggesting that the LHC did not discover the Higgs boson and that what they saw might be something else. This is unlikely to be true, but it has lead to several people asking me for my opinions on the issue. And so for those who have been asking, here is a very brief summary of these claims.

The simplest model of the Higgs boson involves a single particle, relatively heavy compared to other fundamental particles, ...
Continue reading ...
 

A Higgs Boson Armageddon?

Posted by on Tuesday, September 9, 2014, In : Particle Physics 
With that headline, I suppose I should begin this article with a definitive and categorical NO!

So then why is this question even being asked? Because Stephen Hawking likes selling books and is mischievous enough to give doomsday scenarios that the media revels in. He knows that making a wild statements about how the world will end will get his new book a lot of publicity, and perhaps if the publicity leads to people learning about modern particle physics and discussing the latest theories, it...
Continue reading ...
 

Is Lepton Universality Broken?

Posted by on Tuesday, June 3, 2014, In : Particle Physics 
There is interesting news from Switzerland as the LHCb experiment team has announced evidence of a violation of lepton universality, which would be the first experimental evidence of a difference in the interactions of different leptons.

Let me begin with a quick review of leptons and their properties. At the start of the twentieth century, it was discovered that electricity was carried by sub-atomic particles known as electrons. In the following decades, it was proven that these electrons are...
Continue reading ...
 

The Higgs Machine-Learning Challenge

Posted by on Monday, May 19, 2014, In : Particle Physics 
For anyone looking for something fun to do over the summer months, while classes are out and many research projects are stalled for a variety of reasons, the people at Kaggle are hosting an interesting competition this summer.

The Higgs Boson Machine Learning Challenge is a contest to develop better methods of using machine learning methods, such as decision trees and neural networks, to improve the signal-to-noise ratio of particle physics experiments. Competitors will be provided with simula...
Continue reading ...
 

An Exotic Particle at LHCb

Posted by on Wednesday, April 9, 2014, In : Particle Physics 
There is interesting news for the particle physics community today, courtesy of the LHCb (Large Hadron Collider beauty) experiment. They are now claiming that the hint of a new particle that they saw a few years ago has now been confirmed as existing, and the interesting part of the story is that it is not a traditional quark-based particle. This is the first piece of matter to be produced in the lab that is neither a meson nor a baryon, but something completely different. (The original annou...
Continue reading ...
 

Hyperfine Antihydrogen

Posted by on Tuesday, January 28, 2014, In : Particle Physics 
In the previous article, I discussed the claim by the ASACUSA experiment at CERN that they had produced the first man-made beam of anti-hydrogren atoms. Now comes the question of what to do with the beam...

Antimatter, first predicted to exist in the 1928 in a research paper by Paul Dirac and experimentally verified in 1932 by Carl Anderson, is in a sense a mirror image of ordinary matter. Antiparticles have the same mass, but opposite electric charge of their ordinary partners. And fundamenta...
Continue reading ...
 

The First Antihydrogen Beam

Posted by on Tuesday, January 28, 2014, In : Particle Physics 
Exciting new results have been announced by the ASACUSA Experiment at CERN today. The team has been reviewing data they collected in 2012 in the Antiproton Decelerator facility, and have confirmed that they had produced a beam of antihydrogen. If this holds up under peer review and academic scrutiny, it will be the first anti-matter beam of atoms ever produced by mankind. 

In the late 1920s, work by Paul Dirac to understand relativistic quantum mechanics lead to an odd result - his equations p...
Continue reading ...
 

Thirty Years of Z-Bosons

Posted by on Saturday, June 1, 2013, In : Particle Physics 
It was on this day, June 1, 1983, that physicists at the CERN facility in Switzerland first confirmed the existence of the Z-boson and provided full confirmation of the GWS model of weak nuclear forces (also known as electroweak theory) first predicted twenty years earlier. Although it had been inferred from other experiments in the 1970s, this was the first direct observations of its existence. (The CERN press release can be viewed here.)

As I have written in past articles, the Universe is kn...
Continue reading ...
 

The Standard Model in Review: Part 2

Posted by on Friday, August 24, 2012, In : Particle Physics 
In the last post, I introduced the now complete Standard Model of particle physics and the three fundamental forces it contains. In this post, we move on to the actual matter.

The matter in the Standard Model is divided up into three generations of two classes of particles, each with two sub-classes. To date no one has been able to provide a concrete explanation of why there are exactly three generations, but it will likely be discovered in the coming decades. 

The first class is the Leptons.  ...

Continue reading ...
 

The Standard Model in Review: Part 1

Posted by on Friday, August 24, 2012, In : Particle Physics 

Now that the Standard Model has been completed with the Higgs discovery, I have had several requests to explain the Standard Model of physics in laymen's terms, for those who are interested in the current state of particle physics. I have written about this in the past, but since some people are still asking I will re-post it here.

The Standard Model of physics describes all of the known particles and forces, but we also know that it is incomplete as 95% of the energy in the Universe is still...


Continue reading ...
 

FAQs of Higgs, Part II

Posted by on Thursday, July 19, 2012, In : Particle Physics 
As most of you are aware by now, two weeks ago the Large Hadron Collider detected signs of the elusive Higgs boson and confirmed its existence. Yesterday I answered some of the technical questions around the Higgs mechanism, and so today I will try to answer some of the more general questions that readers have been asking.

What use is it to the average person?

This question has been asked of every scientific discovery since the dawn of time. Unfortunately the answer often involves technology ...
Continue reading ...
 

FAQs of Higgs

Posted by on Thursday, July 19, 2012, In : Particle Physics 
As most of you are aware by now, two weeks ago the elusive Higgs boson was detected at the Large Hadron Collider. Since that time I have been sent several questions about this great discovery, which I will try to answer in this and subsequent blog entries. 

What is the Higgs mechanism/field/particle/boson?

I have written about this in several previous entries, so I won't repeat the details here.   Suffice it to say, that the Standard Model of particle physics only works if all matter started ou...

Continue reading ...
 
 

About Me


Dr. Chris Bird I am a theoretical physicist & mathematician, with training in electronics, programming, robotics, and a number of other related fields.

   


Make a free website with Yola