standard model of physics


Antimatter measured for the first time!!!

Scientists have managed to trap and measure antimatter for the first time. Physicists at CERN successfully managed to create and maintain antihydrogen for 15 minutes by combining positrons and antiprotons in a vacuum tube using extremely strong magnetic fields to prevent the antimatter from colliding with the regular matter of the container and annihilating. Positrons occupy different energy levels just like electrons in regular atoms. A laser was used to excite the antihydrogen causing the positrons to move to a higher energy level. Just like in regular atoms, when the positrons are shifting back to their original energy levels electromagnetic radiation in the form of light is given off. The results of the experiment show that antihydrogen absorbs and then reflects the same wavelengths of light as regular Hydrogen as predicted by the standard model. They are hoping to run more precise experiments but so far it looks like we won’t have to change our understanding of physics yet.

Top left image is antihydrogen atoms coming into consideration contact with the sides of the container, annihilating and giving of energy in the form of light.

Here is a link to the pdf of the experiment.


Could No New Particles At The LHC Be Exactly What Physics Needs?

“That’s why I’d love it if the bump goes away. Because it would be a clear signal that we’ve been doing something seriously wrong, that our experience from constructing the standard model is no longer a promising direction to continue.

We already know we’ve been doing something wrong – bump or no bump – because naturalness has gone out the window. But if the bump stays, chances are we’d try to absorb it into the mathematics we already have rather than look for something really new. Sometimes things have to get really bad before they can get better. That’s why for me no-bump is the most hopeful outcome.”

At the end of its second, high-energy run, the Large Hadron Collider appeared to display evidence that perhaps a new particle existed at an energy of 750 GeV. The excess of twin photons produced at that energy appeared in both the ATLAS and CMS detectors, and might indicate the first particle beyond the standard model. It might also be a little-understood feature of the standard model itself, or — perhaps most likely — it may be merely statistical noise. But perhaps the ‘nightmare scenario’ of no new particles is exactly what physics needs, to divert us away from the dead ends of naturalness, elegance, unification and greater and greater symmetries, which have borne no experimental fruits in more than 40 years.

Flavour vs Family vs Generation 

You have your quarks and leptons: 

There are 12 flavours. You can think of it as 12 types since the word flavour doesn’t have a significant meaning, it’s just refering to the 12 different types of quarks and leptons. There’s 6 quark flavours, 6 lepton flavours, for a total of 12 flavours. You can also refer to the neutrinos as 3 neutrino flavours, since there’s 3 types of neutrinos. 

Then you got your generations, aka families. They mean the same thing. See the top quarks is just a heavier version of the charm quark which is just a heavier up quark, so the up quark is part of the 1st generation (orange background), the charm is part of the 2nd generation (green background), the top is part of the 3rd generation (blue background). 

Same with the other ones, the bottom quark is a heavier strange quark is a heavier down quark; the tau is a heavier muon is a heavier electron (as for the neutrinos, we’re not too sure about neutrino masses yet). There’s no difference in interaction (again with exceptions) or properties like charge or spin between generations, they’re just heavier and less stable (ie. will easily decay) versions of the first generation. Because the 2nd and 3rd generations tend to decay into the 1st generation, protons and neutrons are made of up and down quarks, with an electron orbiting it (as oposed to a muon or tau) (again the neutrinos are weird). 


“To see a World in a grain of sand,

And Heaven in a wildflower,

Hold Infinity in the palm of your hand,

And Eternity in an hour”

-William Blake, “Auguries of Innocence”

Doing this was pretty important to me… I pretty much threw my heart and soul into it. I used to draw stuff like this all the time, because when my technical skills lacked I would focus on impact; I’ve wanted to try and replicate that again for a while. 


Why is it so hard to find a new particle?

“The success of the Standard Model is both a blessing and a curse. It’s a blessing that we’ve uncovered a theory that describes nature so well, and that appears to work for all the particle decays and interactions we’ve ever seen so far. But it’s a curse, in that we know there must be more Universe out there, as there are questions the Standard Model can’t answer.”

When it comes to physics, there are a tremendous number of unsolved problems that seem to mandate the existence of a new particle. These include the dark matter problem, the matter-antimatter asymmetry problem, the massive neutrino problem and the strong-CP problem. Moreover, these particles required cannot be part of the Standard Model: they must lie beyond it. Yet not only have detectors and colliders failed to turn up anything new despite 50 years of searches, but most models that would solve these problems are theoretically doomed from the start. Constraints on what new physics could do from big bang nucleosynthesis and the lack of observed flavor-changing neutral currents forbid almost all of the theoretical models we can build.


Science: Where Finding Nothing Is The Biggest Victory Of All

“There are lots of stories out there about how physics is broken, and how we need a massive new breakthrough or a paradigm shift to keep the enterprise of new discoveries going. What nonsense! The truth is that the laws of physics we have in place are the most successful sets of laws we’ve ever come up with. They’ve been tested more robustly than any other set of laws ever, and they’ve passed every single one.”

Over the past month, four big experiments looking for new physics have announced their latest results, and all four have come up empty. At the LHC, ATLAS and CMS failed to confirm the existence of a new particle, leaving us with only the Standard Model. At LUX, the most sensitive dark matter search failed to detect anything new. At IceCube, evidence for a sterile neutrino evaporated. And at CERN’s MoEDAL experiment, magnetic monopoles failed to show up. This might seem like a defeat for physicists, but it’s anything but! The Standard Model and General Relativity emerged victorious again, making them the most successful physical theories of all time, having passed test after test robustly and rigorously. There are still mysteries out there waiting to be uncovered, but we’re going to have to dig a lot deeper if we want to do it.

Find out how far we’ve come, and why each new null result is a victory for exactly where we are today!


Will the LHC be the end of experimental particle physics?

“It’s no stretch to predict that you’re going to see a flurry of articles, presentations and talks over the coming few years on the topic of, “Have we found the first signs of particle physics beyond the Standard Model?”

And if the answer is, “not definitively,” have this be the takeaway: the Standard Model might be all our particle colliders can access in our lifetime. ”

At the end of the 19th century, Lord Kelvin famously said, “There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.” He was talking about how Newtonian gravity and Maxwell’s electromagnetism seemed to account for all the known phenomena in the Universe. Of course, nuclear physics, quantum mechanics, general relativity and more made that prediction look silly in hindsight. But in the 21st century, the physics of the Standard Model describes our Universe so well that there truly may be nothing else new to find not only at the LHC, but at any high-energy particle collider we could build here on Earth.


Ask Ethan: Did the LHC just discover a new particle?

“In the quest to advance our knowledge of the Universe, the biggest advances always seem to come when an experiment or measurement indicates something new: something our best theories to that date hadn’t predicted before. We all know that the LHC is looking for fundamental particles beyond the Standard Model, including hints of supersymmetry, technicolor, extra dimensions and more. Is it possible that the LHC just discovered a new type of particle, and the results just got buried in the news?”

The Standard Model is great at describing all the known particles we’ve ever observed and how they interact, but there are a number of important hints that it isn’t all there is in the Universe. The existence of dark matter, dark energy, neutrino masses, the matter-antimatter asymmetry, the strong-CP and hierarchy problems all tell us that this collection of quarks, leptons, their antiparticles and the bosons we know are only part of the story. The LHC at CERN is currently producing the highest energy collisions at the largest rate ever seen on Earth, making it the best tool to discover new, never-before-seen particles. In a news release just a few days ago, they announced the discovery of multiple new particles – tetraquarks – that had never been seen before.

Could this be the long-awaited new physics? Find out on this week’s Ask Ethan!

The Large Hadron Collider is Back

After two years of work, the LHC under the French-Swiss border is back.

It’s been updated to run with twice as much power as it had when it revealed the Higgs Boson particle.

Scientists are hoping that with this new power it could take us beyond the predictions of the standard model and into a world of entirely new physics.

Among the list of things they hope to find, researchers are looking for signs of mysterious antimatter interactions, dark matter and extra dimensions to name a few.

(Image credit: Maximilien Brice and CERN)



The universe is expanding uniformly according to research led by UCL which reports that space isn’t stretching in a preferred direction or spinning.

The new study, published today in Physical Review Letters, studied the cosmic microwave background (CMB) which is the remnant radiation from the Big Bang. It shows the universe expands the same way in all directions, supporting the assumptions made in cosmologists’ standard model of the universe.

First author, Daniela Saadeh (UCL Physics & Astronomy), said: “The finding is the best evidence yet that the universe is the same in all directions. Our current understanding of the universe is built on the assumption that it doesn’t prefer one direction over another, but there are actually a huge number of ways that Einstein’s theory of relativity would allow for space to be imbalanced. Universes that spin and stretch are entirely possible, so it’s important that we’ve shown ours is fair to all its directions.”

The team from UCL and Imperial College London used measurements of the CMB taken between 2009 and 2013 by the European Space Agency’s Planck satellite. The spacecraft recently released information about the polarisation of CMB across the whole sky for the first time, providing a complementary view of the early universe that the team was able to exploit.

The researchers modeled a comprehensive variety of spinning and stretching scenarios and how these might manifest in the CMB, including its polarisation. They then compared their findings with the real map of the cosmos from Planck, searching for specific signs in the data.

Daniela Saadeh, explained: “We calculated the different patterns that would be seen in the cosmic microwave background if space has different properties in different directions. Signs might include hot and cold spots from stretching along a particular axis, or even spiral distortions.”

Collaborating author Dr. Stephen Feeney (Imperial College London) added: “We then compare these predictions to reality. This is a serious challenge, as we found an enormous number of ways the universe can be anisotropic. It’s extremely easy to become lost in this myriad of possible universes – we need to tune 32 dials to find the correct one.”

Previous studies only looked at how the universe might rotate, whereas this study is the first to test the widest possible range of geometries of space. Additionally, using the wealth of new data collected from Planck allowed the team to achieve vastly tighter bounds than the previous study. “You can never rule it out completely, but we now calculate the odds that the universe prefers one direction over another at just 1 in 121,000,” said Daniela Saadeh.

Most current cosmological studies assume that the universe behaves identically in every direction. If this assumption were to fail, a large number of analyses of the cosmos and its content would be flawed.

Daniela Saadeh, added: “We’re very glad that our work vindicates what most cosmologists assume. For now, cosmology is safe.”


Is That ‘Bump’ a New Particle?

David Kaplan explains how a curious signal in the Large Hadron Collider’s latest data could upset the Standard Model of physics — or mean nothing at all.

Tech Predictions

It is difficult to specify tech predictions accurately and concisely. Here are some possibilities we could consider:

 - Humans walk on Mars.

 - Probes reach another star.

 - Discovery of non-Earth life forms.

 - First contact with intelligent non-Earth life forms.

 - Successful communication with an emulated brain scan.

 - Successful communication with a person who has undergone cryopreservation or plasticization or a similar process and then been scanned or revived.

 - IVF routinely boosts IQ of embryos via gene splicing or some other form of genetic modification.

 - A quantum computer successfully factors RSA-2048 using Shor’s algorithm or another algorithm which cannot be efficiently executed on a classical computer.

 - AI capable of passing the Turing test and learning by instruction.

 - New fundamental theory of physics supplants standard model.

Suggestions would be appreciated! Suitable topics include science, technology, and other geeky non-political events that may or may not happen at some point over the next hundred years or so.

Tagging slartibartfastibast for quantum ideas.