Enlarge / A visibly emotional Peter Higgs was present when CERN announced Higgs boson discovery in July 2012. (credit: University of Edinburgh )

Peter Higgs , the shy, somewhat reclusive physicist who won a Nobel Prize for his theoretical work on how the Higgs boson gives elementary particles their mass, has died at the age of 94 . According to a statement from the University of Edinburgh, the physicist passed "peacefully at home on Monday 8 April following a short illness."

“Besides his outstanding contributions to particle physics, Peter was a very special person, a man of rare modesty, a great teacher and someone who explained physics in a very simple and profound way," Fabiola Gianotti, director general at CERN and former leader of one of the experiments that helped discover the Higgs particle in 2012, told The Guardian . "An important piece of CERN’s history and accomplishments is linked to him. I am very saddened, and I will miss him sorely.”

The Higgs boson is a manifestation of the Higgs field, an invisible entity that pervades the Universe. Interactions between the Higgs field and particles help provide particles with mass, with particles that interact more strongly having larger masses. The Standard Model of Particle Physics describes the fundamental particles that make up all matter, like quarks and electrons, as well as the particles that mediate their interactions through forces like electromagnetism and the weak force. Back in the 1960s, theorists extended the model to incorporate what has become known as the Higgs mechanism, which provides many of the particles with mass. One consequence of the Standard Model's version of the Higgs boson is that there should be a force-carrying particle, called a boson, associated with the Higgs field.

Enlarge / An artist's conceptual rendering of antihydrogen atoms falling out the bottom of the magnetic trap of the ALPHA-g apparatus. (credit: Keyi )

CERN physicists have shown that antimatter falls downward due to gravity, just like regular matter, according to a new paper published in the journal Nature. It's not a particularly surprising result—it would have been huge news had antimatter been found to be repulsed by gravity and "fall" upward—but it does tell us a bit but more about antimatter and brings physicists one step closer to resolving one of the most elusive mysteries surrounding the earliest moments of our universe.

As the name implies, antimatter is the exact opposite of ordinary matter, as it is made of antiparticles instead of ordinary particles. These antiparticles are identical in mass to their regular counterparts. But just like looking in a mirror reverses left and right, the electrical charges of antiparticles are reversed. So an anti-electron would have a positive instead of a negative charge while an antiproton would have a negative instead of a positive charge. When antimatter meets matter, both particles are annihilated and their combined masses are converted into pure energy. (It's what fuels the fictional USS Enterprise , as any Star Trek fan can tell you.)

As far as we know, antimatter doesn’t exist naturally in the known universe, although we can now create small amounts at places like CERN's Antimatter Factory . But scientists believe that ten billionths of a second after the Big Bang, there was an abundance of antimatter. The nascent universe was incredibly hot and infinitely dense, so much so that energy and mass were virtually interchangeable. New particles and antiparticles were constantly being created and hurling themselves, kamikaze-like, at their nearest polar opposites, thereby annihilating both matter and antimatter back into energy in a great cosmic war of attrition.

Enlarge / Event display of a W-boson candidate decaying into a muon and a muon neutrino inside the ATLAS experiment. The blue line shows the reconstructed track of the muon, and the red arrow denotes the energy of the undetected muon neutrino. (credit: ATLAS Collaboration/CERN)

It's often said in science that extraordinary claims require extraordinary evidence. Recent measurements of the mass of the elementary particle known as the W boson provide a useful case study as to why. Last year , Fermilab physicists caused a stir when they reported a W boson mass measurement that deviated rather significantly from theoretical predictions of the so-called Standard Model of Particle Physics —a tantalizing hint of new physics. Others advised caution, since the measurement contradicted prior measurements.

That caution appears to have been warranted. The ATLAS collaboration at CERN's Large Hadron Collider (LHC) has announced a new, improved analysis of their own W boson data and found the measured value for its mass was still consistent with Standard Model. Caveat: It's a preliminary result. But it lessens the likelihood of Fermilab's 2022 measurement being correct.

"The W mass measurement is among the most challenging precision measurements performed at hadron colliders," said ATLAS spokesperson Andreas Hoecker . "It requires extremely accurate calibration of the measured particle energies and momenta, and a careful assessment and excellent control of modeling uncertainties. This updated result from ATLAS provides a stringent test, and confirms the consistency of our theoretical understanding of electroweak interactions.”