Insight into the physics of the Higgs particle

This is Corinna Kollath from the Helmholtz-Institut für Strahlen- und Kernphysik at the University of Bonn.

Physicists at the University of Bonn have succeeded in putting a superconducting gas into an exotic state. Their experiments allow new insights into the properties of the Higgs particle, but also into fundamental characteristics of superconductors. The publication, which is already available online, will soon appear in the journal Nature Physics.

For their experiments, scientists at the University of Bonn used a gas made of lithium atoms, which they cooled down significantly. At a certain temperature, the state of the gas changes abruptly: It becomes a superconductor that conducts a current without any resistance. Physicists also speak of a phase transition. A similar sudden change occurs with water when it freezes.

The lithium gas changes to a more orderly state at its phase transition. This includes the formation of so-called Cooper pairs, which are combinations of two atoms that behave like a single particle to the outside.

Partner-dancing atoms

These pairs behave fundamentally differently from individual atoms: They move together and can do so without scattering on other atoms or pairs. This is the reason for the superconductivity. But what happens when you try to excite the pairs?

"We illuminated the gas with microwave radiation," explains Prof. Dr. Michael Köhl from the Physics Institute at the University of Bonn. "This allowed us to create a state in which the pairs start to vibrate and the quality of the superconductivity therefore oscillated very quickly: One moment the gas was a good superconductor, the next a bad one."

This common oscillation of the Cooper pairs corresponds to the Higgs boson discovered at the CERN Accelerator in 2013. As this state is very unstable, only a handful of working groups worldwide have succeeded in producing it.

The experiments allow an insight into certain physical properties of the Higgs boson. For example, the physicists hope that studies like these will enable them to better understand the decay of this extremely short-lived particle in the medium term.

Fast-switchable superconductors

But the experiments are also interesting for another reason: They show a way to switch superconductivity on and off very quickly. Superconductors normally try to remain in their conductive state for as long as possible. They can be dissuaded by heating, but this is a very slow process. The experiments show that in principle this can also be over a thousand times faster. This insight may open up completely new applications for superconductors.

Read more at Science Daily

The Higgs Boson Particle Isn’t So Godlike After All

Computer simulation of particle traces from an Large Hadron Collider collision in which a Higgs Boson is produced.

Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI science center. Sutter is also host of Ask a Spaceman, RealSpace and COSI Science Now. He contributed this article to Space.com's Expert Voices: Op-Ed & Insights.

Let's be perfectly honest. The Higgs boson and its role in the universe are not the easiest things to explain. It doesn't help that the Higgs has the horrible nickname of "the God Particle" and is often described as being "responsible for mass in the universe" or something like that.

The Higgs boson is indeed an important part of modern physics, but elevating it to the status of a deity seems a bit of a stretch, and the whole "making mass" thing isn't even this particle's most important job.

Oh, and physicists don't really care about the particle.

Don't worry — I'll explain in a bit.

What's in a Name?

First, I want to talk about the particle's name. It has a perfectly acceptable name: the Higgs boson. Physicist Leon Lederman coined the nickname "God Particle" in the early '90s and used it as the title of his book on the subject. I'm sure he thought it was just a cute name (especially since Lederman claims his publisher rejected his original idea of the "Goddamn Particle"), but the media went crazy with the name, and now it's hard to disentangle the real physics of the Higgs from the hype.

The particle's real name, the Higgs boson, is actually quite informative. Indeed, it references two people, further highlighting the particle's importance: Peter Higgs, who with a bunch of colleagues first proposed the particle back in the 1960s, and Satyendra Nath Bose, who was a pioneering figure in the early days of particle physics.

"Boson" is the term for one of the two kinds of particles in the universe, with the other called a "fermion" (after Enrico Fermi). Very, very loosely, you can think of fermions as the building blocks of the everyday world. Think electrons, quarks, protons, neutrinos and all their friends. Meanwhile, the bosons are the forces between them: photons, gluons and so on.

So right there, the name gives you a hint: Because this particle is called a "boson," it must have something to do with forces.

Field of Dreams

But modern particle physics isn't really about the particles themselves, and that goes for the Higgs boson, too. No, in the contemporary view of the rules of the universe, the primary physical object is the field, an entity that permeates all of space and time. This field can take different values at different points in space-time, and each value corresponds to the average number of particles observers see in that patch. In this view (and indeed, in reality), particles can be created and destroyed at will, simply by adding or removing energy from the field.

In other words, you can slap a field and make some particles. A single particle is just the minimum possible amount of energy that a field can support. Every kind of particle that scientists know of, from the electron to a photon, is associated with its own space-time-filling vibrating field.

I'm spending a couple of paragraphs making this distinction clear because the hunt for the Higgs boson isn't about the particle itself. Machines like the Large Hadron Collider are trying to study the Higgs field, but the only way to do so is to make some Higgs particles (i.e., some slaps in the field) and see how they work.

Speaking of work: It's the Higgs field, not the Higgs particle, that's doing interesting things in the universe.

A Broken Universe

The "interesting thing" that the Higgs boson does in the universe relates to a fundamental question of modern physics. Physicists observe four forces of nature: electromagnetic, strong nuclear, weak nuclear and gravity. The photon carries the electromagnetic force, while the W+, W-and Z bosons carry the weak nuclear force and a set of gluons carries the strong nuclear force. And gravity is carried by … well, perhaps that's a subject for another day.

These four forces of nature are, as you may have noticed, radically different from one another. It's nothing at all like the families of fermions: In that realm, a simple change of charge or different measure of mass will get you a new kind of particle. In the boson world, the electromagnetic force is completely different from the weak nuclear force in terms of mass, range, and interactions, and their respective force carriers aren't even on speaking terms, let alone related to each other.

But why? Really, why? Why are the forces of nature so dang different?

One clue to this perplexing mystery is that, at high enough energy densities — like, say, in the business end of a particle collider — there are only three forces of nature. You read that right: three, not four! There's strong nuclear, gravity, and a strange hybrid of electromagnetic and weak nuclear called, appropriately enough, the electroweak force.

This force appears only at high energies, and a quartet of massless particles carry it. Mathematically, these particles and their associated force are in a highly symmetric state. But at low (read: normal, everyday) energies, that unified symmetric force breaks apart to become the awkwardly-split-but-still-have-to-live-together electromagnetic force (carried by the still-massless photon) and weak nuclear force (carried by a much heavier trio of particles).

And the cause of the split is the good ol' Higgs (which you may have guessed, because that's the focus of this article).

Making the Split

At that high-energy, symmetric state, not only are there four massless carries of the electroweak force, but there are also four Higgs fields. The reason there are precisely four isn't that there's a rigged matching game; the same deep symmetries that lead to the electroweak unification also provide the mathematical machinery for constructing four Higgs fields. In other words, if you're going to propose the existence of a Higgs field at high energies, you don't get any choice but to construct four – it's baked into the fundamental symmetries of our universe.

I haven't seen anyone name these four high-energy Higgs fields "the higglets" yet, so I'll just go ahead and make that a thing.

At high temperatures, the four carries of the electroweak force do their thing (carry the electroweak force) and the four higglets do their thing (not much of anything). But at low temperatures, the higglets get disrupted. Three of them "glue" (for lack of a better term) to three of the electroweak carriers. These hybrid creatures become massive, and physicists know them as the W, Z+, and Z- bosons — and, voilà, the weak force is born.

But the fourth higglet gets "stuck" (again, for lack of a better term) in an asymmetrical state that prevents it from matching up with the remaining electroweak carrier. That carrier then gets to remain massless — and, aha, you get the photon, carrying the now-familiar electromagnetic force.

Read more at Discovery News

Scientists predict the existence of a new boson

Real CMS proton-proton collisions events in which 2 high energy electrons and two high energy muons are observed.

Scientists at the High Energy Physics Group (HEP) of the University of the Witwatersrand in Johannesburg predict the existence of a new boson that might aid in the understanding of Dark Matter in the Universe.

Using data from a series of experiments that led to the discovery and first exploration of the Higgs boson at the European Organization for Nuclear Research (CERN) in 2012, the group established what they call the Madala hypothesis, in describing a new boson, named as the Madala boson. The experiment was repeated in 2015 and 2016, after a two-and-a-half year shut-down of the Large Hadron Collider (LHC) at CERN. The data reported by the LHC experiments in 2016 have corroborated the features in the data that triggered the Madala hypothesis in the first place.

"Based on a number of features and peculiarities of the data reported by the experiments at the LHC and collected up to the end of 2012, the Wits HEP group in collaboration with scientists in India and Sweden formulated the Madala hypothesis," says Professor Bruce Mellado, team leader of the HEP group at Wits.

The Wits Madala project team consists of approximately 35 young South African and African students and researchers who are currently contributing to the understanding of the data coming out of the LHC experiments, along with phenomenological investigations from theorists such as Prof. Alan Cornell and Dr. Mukesh Kumar and support in the area of detector instrumentation from Prof. Elias Sideras-Haddad (all from Wits University).

The hypothesis describes the existence of a new boson and field, similar to the Higgs boson. However, where the Higgs boson in the Standard Model of Physics only interacts with known matter, the Madala boson interacts with Dark Matter, which makes about 27% of the Universe.

"Physics today is at a crossroads similar to the times of Einstein and the fathers of Quantum Mechanics," says Mellado. "Classical physics failed to explain a number of phenomena and, as a result, it needed to be revolutionised with new concepts, such as relativity and quantum physics, leading to the creation of what we know now as modern physics."

The theory that underpins the understanding of fundamental interactions in nature in modern physics is referred to as the Standard Model of Physics. With the discovery of the Higgs boson at the LHC in 2012, for which the Nobel Prize in Physics was awarded in 2013, the Standard Model of Physics is now complete. However, this model is insufficient to describe a number of phenomena such as Dark Matter.

The universe is made of mass and energy. The mass that we can touch, smell and see, the mass that can be explained by the Higgs boson, makes up only 4% of the mas-energy budget of the Universe. The rest of the mass in the Universe is simply unknown, yet it makes about 27% of the world around us. The next big step for the physics of fundamental interactions now is to understand the nature of Dark Matter in the Universe: what is it made of? How many different types of particles are there? How do they interact among each other? How does it interact with the known matter? What can it tell us about the evolution of the Universe?

The discovery of the Higgs boson at the LHC at CERN has opened the door into making even more ground-breaking discoveries, such as the observation of new bosons that are linked to forces and particles unknown before. These new particles can explain where the unknown matter in the Universe comes from.

Read more at Science Daily

Atom Smasher Probes Highest Energies Yet

Scientists at the world’s largest atom smasher have made a precise tally of the jumbled cascade of particles produced when two proton beams are smashed together. The results could help researchers discover new types of particles, akin to the now-famous Higgs boson.

Researchers at the Large Hadron Collider (LHC) in Switzerland sent two beams of protons hurtling in opposite directions and crashed them together at the highest energy level yet achieved at the LHC. The research is part of the CMS experiment, which stands for Compact MuonSolenoid. For each of the 150,000 proton-proton collisions the researchers identified, about 22 charged particles (hadrons) were produced.

The scientists wanted to create a snapshot of a “typical” collision between two proton beams, which could help the researchers sift through background noise for signs of new effects. Previous models to make predictions for detecting new particles rely on estimates with an uncertainty of 30 to 40 percent, which could be problematic for detecting rare particles, the researchers said.

To get a precise count of the number of particles produced in an average proton collision, the team analyzed data with the LHC’s magnet turned off. This meant the scientists could accurately count the number of charged particles, because they arrive at the CMS detector itself rather bending from the magnetic field and ending up in the main collider’s beam pipe, Yen-Jie Lee, an assistant professor of physics at the Massachusetts Institute of Technology and one of the study’s lead researchers, said in a statement.

The LHC is an underground ring measuring about 16 miles (27 kilometers) in circumference. It accelerates particles to nearly the speed of light using powerful magnets. The CMS experiment is one of a handful of detectors built into the LHC machine.

The energy intensity at the atom smasher has increased by 60 percent — from about 7 teraelectronvolts (TeV) to 13 TeV — since its first run, which lasted from 2010 to 2013. This is still a tiny amount of energy; 1 TeV is about the energy of motion of a flying mosquito. Within a proton though, this is squeezed into a space about a million, million times smaller than a mosquito, according to the European Organization for Nuclear Research (CERN), which operates the LHC.

The LHC’s energy boost means that 30 percent more particles are produced per collision, the researchers found.

“At this high intensity, we will observe hundreds of millions of collisions each second,” Lee said.

The increased energy also gives physicists a better chance of discovering new particles like the Higgs boson, which was first detected in 2012. According to Albert Einstein’s equation e = mc2, the higher the energy (e) of the experiment, the higher the mass (m) of the new particles could be.

“We are opening up a new region of these collisions that we have never opened up before,” said Daniela Bortoletto, a physicist who was previously involved with the CMS collaboration but now works on ATLAS, a rival experiment at the LHC. “We are really exploring terra incognita!”

The ATLAS group also observes collisions between a set of two proton beams and is in the process of replicating the CMS experiment to count the number of hadrons produced.

Bortoletto said that these measurements are fundamental to physics because they help “get to the diamond in a terrain full of dirt.”

“It’s part of the mankind desire to understand where we came from,” Bortoletto told Live Science. “And we’ve done really remarkably well in explaining a lot of the phenomena.”

Bortoletto says the measurements described in this paper are necessary to discover new particles in the higher energy regime. While she said the theories behind the building blocks of the universe are impressively accurate so far, there is still something missing.

The Standard Model, the reigning theory of particle physics, is based on the idea that all matter is made of particles of two basic types, called quarks and leptons, and the forces that act on them.

However, it is not a flawless design, and there are gaps to fill in. Discovering unknown — and sometimes invisible — particles could help physicists, like Bortoletto, see the bigger picture.

Read more at Discovery News

After Higgs, Supercharged LHC to Probe Physics Frontier

Don Lincoln is a senior scientist at the U.S. Department of Energy's Fermilab, America's largest Large Hadron Collider research institution. He also writes about science for the public, including his recent "The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Things That Will Blow Your Mind" (Johns Hopkins University Press, 2014). You can follow him on Facebook. Lincoln contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

Somewhere under the French-Swiss border, two protons have a date with destiny. Trapped inside the Large Hadron Collider (LHC), the world's largest and most powerful particle accelerator, they follow a circular path in opposite directions with velocities very near the speed of light.

As they approach each other, their fate is clear: A collision is inevitable. One could imagine that an impact between two protons might look like a collision between subatomic billiard balls. But the rules of the microrealm are quite different from what familiar intuition developed in the corner pub would suggest.

Colliding with Success

After a hiatus of more than two years, the LHC is up and running again. After a broad program of refurbishments, retrofits and upgrades, the accelerator is essentially an entirely new facility. Operating at nearly double the energy and triple the number of collisions per second, the LHC will create collisions within the centers of four huge experiments, each ready to make the discovery of the century.

Since Einstein's 1905 papers on relativity, physicists have known of the equivalence between energy and mass. As described by Einstein's famous equation (E=mc2), energy can be converted into matter and vice versa. And that's one of the big things that happens inside a particle accelerator. The huge kinetic (i.e., moving) energy of the two incoming beam particles is converted into the mass of particles that didn't exist before the collision.

It is in this manner that two protons, each having a low mass (about 1 billion electron volts for the techno-crowd), can collide and make the Higgs boson, which is a particle with a mass about 125 times heavier than that of a proton. The motion energy of the protons is literally transformed into a very heavy particle.

When the LHC began operations in 2010, it had a clear mission. Two large experiments, each comprised of around 3,000 scientists, were focused predominantly on finding the Higgs boson. Predicted in 1964, the Higgs boson is connected to the Higgs field, which is thought to give the mass to fundamental (i.e., pointlike) subatomic particles. Finding the Higgs boson meant that the idea of the Higgs field was validated.

Prior to its discovery, the Higgs boson was the last missing component of the wildly successful Standard Model of particle physics. When combined with Einstein's theory of general relativity, the Standard Model can describe the behavior all of the matter ever observed — from the matter in you and me, to majestic galaxies careening through the cosmos.

While the discovery of the Higgs boson in 2012 was indeed an enormous success for the scientific community, the triumph came with a disappointment. Explaining this is simple: Essentially, the Higgs boson was like a final piece that completed the Standard Model puzzle. However, as any puzzle enthusiast will tell you, it is the tabs and blanks of pieces that allow one to build a puzzle. The hanging tab gives you a hint as to what the next piece will be. But a completed puzzle is silent on what to do next.

The Mysteries That Remain

It's not like we don't have mysteries in the world of physics. From our observation of galaxies, we know that they rotate faster than can be explained by the known laws of gravity and the matter we can detect. To explain that mystery, we invented an unobserved form of matter called dark matter. The fundamental nature of dark matter is certainly a big mystery.

Another mystery stems from that famous Einstein equation, E=mc2. It actually says that when energy is converted into matter, an equal amount of antimatter will be made. During the Big Bang, the universe was full of energy, and this energy transformed into equal amounts of matter and antimatter. Yet when scientists look at the universe, they see only matter. So where did the antimatter go? While physicists have had a few hints from previous experiments, we don't really know the answer. This is another mystery.

There are other mysteries, too, like wondering if there are smaller building blocks of the universe than those with which we are now familiar. Following the history of investigations into that question, we have learned of molecules and then atoms. Research in the early 1900s revealed protons, neutrons and electrons, and the 1960s brought to light the quarks and leptons that are currently considered the smallest particles of nature. However, it is natural to ask if there might be even smaller building blocks. While scientists don't know the answer, there must be some sort of deeper and more fundamental physics that can explain the patterns seen in the quarks and leptons. The answer to that question is yet another mystery.

The Curious Higgs boson Mass

Physicists don't know the answer to any of those fundamental questions, and, to be honest, it is possible that the LHC won't teach us about any of those secrets of nature. But there is one question for which LHC data is a surer bet.

It stems from mysteries that arise in calculations of the Higgs boson's mass. When scientists try to calculate this value directly from the theory, the result is much higher than the LHC data suggest.

Because of the laws of quantum mechanics, the Higgs boson can fluctuate into other types of particles (e.g., the top quark, the W and Z bosons, and even pairs of Higgs bosons). This behavior leads to predictions of the mass of the Higgs boson that are closer to the Planck mass which is a hundred quadrillion times heavier than the mass that scientists have measured. (The Planck mass is the highest mass our current theories could possibly apply and marks a frontier beyond which we are certain that we will have to rethink everything.)

Obviously, this is a problem, and physicists have spent several decades imagining possible explanations, even before the Higgs boson's discovery. (After all, it was clear even early on that this problem would exist if the Higgs boson had a mass that could be discovered.)

Supersymmetry
The most popular theoretical explanation is a principle called supersymmetry. This idea essentially postulates that the force-carrying bosons (particles with a subatomic spin that is integer multiple of ?, which is the natural unit for spin in the quantum world). For example, photons of spin 1 × ? and the matter-carrying fermions (particles with half integer subatomic spin, e.g. electrons of spin 1/2 x ?) should appear in the theory in a symmetric way. That means if you swap all the fermion and boson symbols, the equation will remain unchanged. Essentially this puts forces and matter on equal footing, making them conceptually interchangeable.

And in theories with supersymmetry, a new set of particles emerge, cousins of the familiar particles of the Standard Model. Supersymmetry says that the familiar quarks and leptons must come with new, related particles physicists now call squarks and sleptons. Similarly, supersymmetric analogs of the photon and gluon, called photinos and gluinos, must exist.

Mind you, no direct evidence for the existence of these supersymmetric particles has ever been found. However, if they do exist, scientists can use these particles' quantum mechanical properties to cancel the contribution of the familiar particles in calculations of the mass of the Higgs boson. With supersymmetry accounting for the other particles, the calculations result in a predicted mass of the Higgs boson that is small, in accordance with measurements.

Some scientists' enthusiasm for supersymmetry has been dampened by the fact that supersymmetric particles haven't been observed. Thus, researchers are exploring other possibilities, for example, the ideas that there might exist additional dimensions of space or that the Higgs boson might contain smaller particles within it. These ideas and others are alternative approaches for taming the unruly predictions of the mass of the Higgs boson.

Read more at Discovery News