like a physicist

the-star-stuff:

Is the New Physics Here? Atom Smashers Get an Antimatter Surprise

(November 18, 2011)

The world’s largest atom smasher, designed as a portal to a new view of physics, has produced its first peek at the unexpected: bits of matter that don’t mirror the behavior of their antimatter counterparts.

The discovery, if confirmed, could rewrite the known laws of particle physics and help explain why our universe is made mostly of matter and not antimatter.

Scientists at the Large Hadron Collider, the 17-mile (27 km) circular particle accelerator underground near Geneva, Switzerland, have been colliding protons at high speeds to create explosions of energy. From this energy many subatomic particles are produced.

Now researchers at the accelerator’s LHCb experiment are reporting that some matter particles produced inside the machine appear to be behaving differently from their antimatter counterparts, which might provide a partial explanation to the mystery of antimatter. [The Coolest Little Particles in Nature] (continue reading)

quantumaniac:

Antimatter 

All objects that we can see on and from Earth are composed of regular, everyday matter. This matter is composed of atoms, which are composed of particles; protons, neutrons, electrons and the like. Similarly, antimatter is composed of antiparticles; such as positrons, antiprotons and antineutrons. These antiparticles are, of course, composed of antiquarks. Antiparticles can even collect together to form antiatoms! Thus, all of our matter-composed elements are possible with antimatter - antihydrogen for example. 

In an antiparticle, charge must be opposite, and mass must be basically exactly the same. Electrically neutral particles aren’t identical to their anti-counterparts, since they are still composed of antiquarks and antiparticles. 

In 1928, Paul Dirac paved the first path to antimatter when he predicted positrons. Antimatter is not just a theoretical mathematical anomaly - it exists in nature. Antiparticles are created during beta decay, and in the interaction of cosmic rays (most notably gamma rays) and Earth’s atmosphere. Due to our universe’s conservation of charge, it is not possible to create an antiparticle without creating a particle of opposite charge or destroying a particle of the same charge. However, some (typically near or exactly massless) particles are their own antiparticles, such as photons, the theorized gravitons and some WIMPs.

Interestingly, when matter and antimatter collide - annihilation occurs. The collision can produce such emissions as high-energy photons (gamma rays,) or even other particle-antiparticle pairs. The particles that are their own antiparticles, such as gravitons and photons, can even annihilate with themselves! One of the greatest mysteries in Physics today is that, since this collision occurs, why the universe seems to be composed of mostly matter. In a process called baryogenesis, an asymmetry has occurred in the universe between matter and antimatter - and scientists are working hard as we speak to figure out why that is.  

sayitwithscience:

Antiprotonic Helium

Antiprotonic helium consists of an electron and antiproton that orbit around a helium nucleus. The hyperfine structure of this exotic type of matter is studied very closely by a CERN experiment in Japan called ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) using laser spectroscopy.

To create antiprotonic helium, antiprotons are mixed with helium gas so that they spontaneously remove one of the electrons that orbit around each of the helium atoms and take their places. However, this reaction will only occur for 3% of the gas.

From the time that antiprotonic helium is created, the antiprotons orbiting the helium nucleus will only remain in orbit for a few micro seconds until they fall rapidly into the nucleus, causing a proton-antiproton annihilation. Surprisingly, antiprotonic helium has the longest lifetime of all the other antiprotonic atoms.

Laser Spectroscopy

ASACUSA physicists used a laser pulse (that if tuned correctly) will let the atom of antiprotonic helium absorb just enough energy so that the antiproton can jump from one energy level (aka orbit) to the other. Thus allowing physicists to determine the energy between orbits of an atom. Currently, laser and microwave precision spectroscopy of antiprotonic helium atoms is ASACUSA’s top priority. (Which is basically using two laser beams and pulsed microwave beams to further explore the ‘hyperfine energy levels’ of antiprotonic helium.)

ALPHA experiment. Particle physics FTW!