New Subatomic Particle Detected

The BESIII collaboration have reported the observation of an anomalous line shape around ppbar mass threshold in the J/ψ→γ3(π+π-) decay, which indicates the existence of a ppbar bound state. The paper was published online in Physical Review Letters.

The proximity in mass to 2mp is suggestive of nucleon-antinucleon bound states, an idea that has a long history. Before the birth of Quark Model, a nucleon-antinucleon bound state was already proposed by Prof. E. Fermi and Prof. C. N. Yang.

There is an accumulation of evidence for anomalous behavior in the proton-antiproton system near the ppbar mass threshold, e.g., J/ψ→γppabr , J/ψ→γπ+π-η' and the proton's effective form factor determined from e+e-→ppbar, exhibiting a narrow peak or a very steep falloff around the ppbar mass threshold, which inspired many speculations and renewed the interests on the nucleon-antinucleon bound state.     READ MORE...

From the Dawn of Time

The particle was produced inside the Large Hadron Collider at CERN. (Image credit: Shutterstock)

Physicists at the world's largest atom smasher have detected a mysterious, primordial particle from the dawn of time.

About 100 of the short-lived "X" particles — so named because of their unknown structures — were spotted for the first time amid trillions of other particles inside the Large Hadron Collider (LHC), the world's largest particle accelerator, located near Geneva at CERN (the European Organization for Nuclear Research).

These X particles, which likely existed in the tiniest fractions of a second after the Big Bang, were detected inside a roiling broth of elementary particles called a quark-gluon plasma, formed in the LHC by smashing together lead ions. By studying the primordial X particles in more detail, scientists hope to build the most accurate picture yet of the origins of the universe. They published their findings Jan. 19 in the journal Physical Review Letters.
wie X particle's internal structure, which could change our view of what kind of material the universe should produce."

Scientists trace the origins of X particles to just a few millionths of a second after the Big Bang, back when the universe was a superheated trillion-degree plasma soup teeming with quarks and gluons — elementary particles that soon cooled and combined into the more stable protons and neutrons we know today.

Just before this rapid cooling, a tiny fraction of the gluons and the quarks collided, sticking together to form very short-lived X particles. The researchers don't know how elementary particles configure themselves to form the X particle's structure. But if the scientists can figure that out, they will have a much better understanding of the types of particles that were abundant during the universe's earliest moments.  READ MORE...