The Higgs boson reveals its affinity for the top quark
New results from the ATLAS and CMS experiments at the LHC reveal how strongly the Higgs boson interacts with the heaviest known elementary particle, the top quark, corroborating our understanding of the Higgs and setting constraints on new physics.
The Higgs boson interacts only with massive particles, yet it was discovered in its decay to two massless photons. Quantum mechanics allows the Higgs to fluctuate for a very short time into a top quark and a top anti-quark, which promptly annihilate each other into a photon pair. The probability of this process occurring varies with the strength of the interaction (known as coupling) between the Higgs boson and top quarks. Its measurement allows us to indirectly infer the value of the Higgs-top coupling. However, undiscovered heavy new-physics particles could likewise participate in this type of decay and alter the result. This is why the Higgs boson is seen as a portal to new physics.
A more direct manifestation of the Higgs-top coupling is the emission of a Higgs boson by a top-antitop quark pair. Results presented today, at the LHCP conference in Bologna, describe the observation of this so-called "ttH production" process. Results from the CMS collaboration, with a significance exceeding five standard deviations (considered the gold standard) for the first time, have just been published in the journal Physical Review Letters [open, DOI: 10.1103/PhysRevLett.120.231801]; including more data from the ongoing LHC-run, the ATLAS collaboration just submitted new results for publication, with a larger significance.
Also at ZME Science.
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MIT News reports that the particle discovered in 2012 and thought to be the elusive Higgs Boson is indeed that particle.
The findings, published in the journal Nature Physics, confirm that the bosons decay to fermions, a group of particles that includes all leptons and quarks, as predicted by the Standard Model of particle physics.
"This is an enormous breakthrough," says Markus Klute, an assistant professor of physics at MIT and leader of the international effort. "Now we know that particles like electrons get their mass by coupling to the Higgs field, which is really exciting."
Higgs factory a 'must for big physics'
A top physicist says the construction of a "factory" to produce Higgs boson particles is a priority for the science community. In an exclusive interview, Nigel Lockyer, head of America's premier particle physics lab, said studying the Higgs could hasten major discoveries. He said momentum in the physics community was gathering for a machine to be built either in Europe or Asia. "Our field uniformly agrees that would be a good thing," he told the BBC. The Fermilab director added: "The Higgs is such an interesting particle - a unique particle."
[...] Physicists had hoped that the LHC would turn up evidence of physics phenomena not explained by the Standard Model. So far, efforts to detect new physics have come away empty-handed, but studying the Higgs in more detail might break the impasse.
A successor to the Large Hadron Collider would be designed in a way that allows scientists to zero in on the Higgs boson. The LHC works by smashing beams of proton particles together, but the collisions that produce the Higgs also produce many other particles. This makes it complicated to work out which collisions produce the Higgs boson. A different type of particle smasher, called an electron-positron collider, should produce only a Higgs and another particle called a Z boson.
This makes it more suitable for detailed study of the Higgs' properties. Dr Lockyer said there were currently discussions over a new electron-positron collider in China, and a linear collider that could function as a Higgs factory in Japan. Alternatively, it could be housed at Cern after the Large Hadron Collider comes to the end of its operating lifetime. [...] But he stressed that there was still plenty to come from the LHC, which will undergo a major upgrade in the 2020s.
(Score: 1, Funny) by Anonymous Coward on Wednesday June 06 2018, @02:57PM
Does this mean Higgs bosons can be bottoms when created with a top quark? This is going to make physics porn more diverse.