Neutrinos Probe Antimatter in Japan

Neutrinos are nearly massless elementary particles that interact extremely weakly with matter. As you read this sentence, trillions of neutrinos are streaming through your body at nearly the speed of light, yet you don't feel a thing. It has been said that a neutrino could easily pass through light years of lead before disturbing even one atom - quite the feat for a particle that may hold the key to understanding the dearth of antimatter in our Universe! Not only are these subatomic speed ninjas extremely difficult to detect, but they actually possess a kind of quantum mechanical ADD as well. Neutrinos are known to spontaneously change between three distinct types, or flavors, during the course of their travels. Two of these so-called flavor oscillations have already been observed, leaving just one unaccounted for... until now.

Just a few days ago, scientists from the T2K experiment in Japan released data that suggests they may have witnessed the third flavor oscillation. At the T2K experiment, a beam of muon neutrinos is isolated from a proton stream at J-PARC in Tokai, and sent to the Super-Kamiokande detector in Kamioka, 295 kilometers away. The goal of the experiment is to see how many muon neutrinos change into electrons neutrinos along the way by detecting the number of electron events at the far detector. In an experiment of this nature, approximately 1.5 electron events that have nothing to do with neutrino flavor oscillations are to be expected. But when the background noise and other rogue neutrino events were filtered out of the data, 6 solid events remained: 6 events that suggest the appearance of electron neutrinos with 99.3% confidence, a 2.5 sigma result.

Due to the earthquake that struck Japan back in March, the T2K experiment has only been able to gather 2% of the total data it was designed to. So with 98% of the data still forthcoming, a 2.5 sigma is a pretty promising result. Physicists are hoping that understanding this last flavor oscillation will allow them to probe the differences between neutrinos and their anti-particles, anti-neutrinos. If the mechanism of flavor oscillation differs between the two sets, it may lead scientists to a better understanding of CP violation, the phenomenon believed to be responsible for the abundance of matter over anti-matter in our universe.

Antigravity Could Replace Dark Energy as Cause of Universe’s Expansion

Since the late 20th century, astronomers have been aware of data that suggest the universe is not only expanding, but expanding at an accelerating rate. According to the currently accepted model, this accelerated expansion is due to dark energy, a mysterious repulsive force that makes up about 73% of the energy density of the universe. Now, a new study reveals an alternative theory: that the expansion of the universe is actually due to the relationship between matter and antimatter. According to this study, matter and antimatter gravitationally repel each other and create a kind of “antigravity” that could do away with the need for dark energy in the universe.
Read more...

Full story at Universe Today.

Particle physics theory plays God, creates the universe.

For eons, human beings have wondered how we came to be. Physics provides a simple answer: in the early universe, there was more matter than antimatter. You see, when equal parts matter and antimatter meet, they annihilate each other. The slight overabundance of the former 13.7 billion years ago explains why there is a universe at all, and why all the "stuff" we see in it is made out of matter instead of antimatter. Although this is a fairly agreed-upon theory, it begs yet another question: why was there an excess of matter? For years, scientists have cited a phenomenon called CP violation that predicts such an excess; however, CP violation does not predict enough of an excess to match present-day observations. Now, a group at Fermilab's Tevatron claims that they have found yet another instance of CP violation that could help to fill the observational gap.


Fermilab, home of the Tevatron. Image courtesy of Renzo Borgatti.

CP violation postulates that certain particles can transform into both their associated antiparticles and particles that exhibit a mirror-image symmetry, or an opposite "handedness". The former type of inversion is called charge conjugation violation, while the latter is called parity violation. CP violation is one of the Sakharov conditions, three rules that detail what must have occurred during the first short moments following the Big Bang in order for the universe to appear as it does today. The new instance of CP violation was found during an experiment involving a type of neutral B meson. These B mesons each consist of two quarks: an anti-bottom quark and a strange quark. During the experiment, B mesons transformed into anti-B mesons, which consist of a bottom quark and either an anti-strange quark or an anti-down quark. Each of these different "flavors" of quark is unstable in isolation, and decays into a different kind of particle.

The Tevatron experiment yielded an excess of positively charged muons, which only result from the decay of anti-bottom quarks. Since anti-bottom quarks are only found in B mesons and not anti-B mesons, this particular instance of CP violation seems to indicate an excess of matter over antimatter: the exact result the team was seeking. The results of this experiment will soon be retested at multiple detectors around the world, including CDF at Fermilab and the ATLAS and LHC-b detectors at CERN. Until then, the jury is out on whether CP violation can account for the very small matter of our human existence.