CERN spots strange Higgs boson decay behavior:
Evidence discovered at CERN of a rare form of Higgs boson decay may be just what scientists need to prove the existence of particles beyond those predicted by the Standard Model of particle physics – indirectly, at least.
[R]esearchers working on a pair of CERN experiments – ATLAS and CMS – said their combined datasets offer the first evidence of a Higgs boson decaying into a Z boson (an electrically neutral carrier of the weak force) and a photon.
Higgs bosons decay in various ways. They can split into four electrons, for example, or a pair of the electron's heavier cousin, muons. It's also possible for a Higgs boson to decay into two photons, but here's where things start to get tricky and weird: a Higgs boson doesn't decay directly into two photons.
Instead of going from Higgs directly to photons, "the decays proceed via an intermediate 'loop' of 'virtual' particles that pop in and out of existence and cannot be directly detected. These virtual particles could include new, as yet undiscovered particles that interact with the Higgs boson," CERN said.
According to said Standard Model and CERN, around 0.15 percent of Higgs bosons should decay into a Z boson and photon, but the data indicates it's actually happening in around 6.6 percent of decays picked up by the Large Hadron Collider. In theoretical models that extend the Standard Model to include other particles the Higgs' Z boson/photon decay rate varies from the 0.15 percent predicted by the standard Standard Model. In other words, something interesting and potentially undiscovered is going on.
"Through a meticulous combination of the individual results of ATLAS and CMS, we have made a step forward towards unraveling yet another riddle of the Higgs boson," said ATLAS physics coordinator Pamela Ferrari.
Of course, there's also the certainty of this discovery to assess, and it's not as sure a thing as the discovery of the Higgs boson itself by CERN scientists in 2012. While the Higgs boson's evidence was given a statistical significance of 5-Sigma (roughly equivalent to a one in 3.5 million chance that its discovery was an error), the Z boson/photon decay discovery only rates 3.4-Sigma – still a pretty low chance of being a mistaken observation, but greater than the discovery of the Higgs boson itself.
In other words, the science continues with hopes more Higgs observations will help clear things up. "This study is a powerful test of the Standard Model. With the ongoing third run of the LHC and the future High-Luminosity LHC, we will be able to improve the precision of this test and probe ever rarer Higgs decays," said CMS physics coordinator Florencia Canelli.
(Score: 2) by Immerman on Thursday June 01 2023, @03:14PM
Okay, am I missing something? My understanding was that in the wacky world of quantum particle transmutation/decay all the fundamental properties like electric charge, color charge, and (I think) spin, were conserved. E.g. electrons and positrons generally spawn together because their various properties all sum to zero, though other combinations can spawn so long as the sum remains zero (or in case of a decay, equal to whatever the original particle had). Mass-energy conservation is sufficiently complicated that it's probably best for non-experts to just assume it's not conserved (e.g. virtual particle pairs spawning from nothing, etc.)
So the Higgs has both charge 0, color charge 0, and spin 0.
Decaying into photons - okay, they also have 0 charge or color charge. They do have spin 1, but I think spin is just a magnitude (e.g. usually either 1 or 1/2), so two spin 1 particles can still have a net spin of zero.
Into two W bosons - sure, again 0 color charge, and while they have an electric charge it can have either polarity, and a W+ and W- boson will have no net charge
Into four electrons though? Suddenly you have a net charge of -4, where did that come from?
And two muons? Net charge of -2
So am I missing something, or is this just bad reporting? Most of the "normal" decays aren't even mentioned on the Hiigs wikipedia page - e.g. there is no decay into electrons mentioned, and while you can get a muon, it's as part of a muon/anti-muon pair, not two muons. In the same vein perhaps "4 electrons" should be two electrons-positron pairs - but that's still not listed on Wikipedia as one of the common decay paths.
(Score: 2) by Immerman on Thursday June 01 2023, @03:26PM
I seem to recall that anything under 4 sigma should generally be considered "potentially interesting, but probably wrong". E.g. if you look at all the particles "discovered" at 4 sigma or less, just shy of 100% never made it to 5-sigma confidence - a.k.a. they were never really anything more than a statistical anomaly in the data.
As much fun as it can be following the newest cutting-edge science, I really wish more articles would make clear that such "discoveries" almost certainly aren't.
Any new "discovery" will have a higher confidence than the initial "discovery" of particles that were eventually proven to (almost certainly) exist, but that's not saying much. *Every* uncommon particle "discovery" started as a probably-wrong anomaly whose existence was only confirmed through a long and exhaustive confirmation process.