Elusive Higgs decay channel spotted; particle looks ever more standard

[n2doc]

by John Timmer - Nov 27 2013, 2:50pm EST

The Standard Model in physics seems to have split personalities. It's very obviously incomplete since it has no mechanism to give neutrinos mass, and it has no particles that correspond to dark matter. But it handles the phenomena it does include with a precision that seems to frustrate some physicists, who are anxious for signs of a new physics.

This was clearly demonstrated by the discovery of the Higgs boson, which showed up pretty much exactly as predicted. There were a couple of potential discrepancies between prediction and reality, but the researchers behind the ATLAS detector have now slammed the door shut on one of those.

The Higgs is a massive, unstable particle that decays almost as soon as it pops into existence. But it can decay down a number of different pathways, referred to as "channels" by the physicists who were searching them. When its discovery was announced, researchers had spotted the Higgs in two channels: decay into two high-energy gamma rays and decay into pairs of W or Z bosons, which would then decay into a total of four leptons.

What seemed to be missing was a decay into pairs of particles called taus (sometimes tauons). These particles are members of a group that includes the familiar electron and its heavier relative, the muon. Muons are also negatively charged, weigh nearly as much as a proton, and decay in about 10^-6 seconds. Taus weigh over 10 times more and decay in about 10^-13 seconds. Typically, these heavier particles decay down to the next-lighter version, releasing some energy in the process.

more

http://arstechnica.com/science/2013/11/elusive-higgs-decay-channel-spotted-particle-looks-ever-more-standard/

[longship]

1. That's got to be frustrating.

Particle physicists hate being proved right. It means that there's nothing new there. The standard model has resisted "new" for decades.

That's an amazing story by itself.