Tag Archive | decay

The Higgs boson Part 3: Exotic Higgs decays

The Standard Model predicts that the Higgs boson is unstable and falls apart (decays) only 10-22 s (0.0000000000000000000001 seconds) after it is created. Theoretically, it can decay to a quark-anti quark pair (except for top, anti-top), a lepton anti-lepton pair or to two bosons (like photons or gluons).

However, there is also the possibility that it could decay to new particles that have not been observed until now, so-called long-lived scalar particles (scalar means they are spinless just like the Higgs boson). Some theories beyond the Standard Model (e.g. http://arxiv.org/abs/1312.4992) predict that these particles would be unique in that only the Higgs boson would decay to them, meaning it would have been impossible to study them until now – these are one example of what we call ‘exotic particles‘.

An exotic Higgs decay producing two off-centre vertices

An exotic Higgs decay producing two off-centre vertices

The diagram above shows a Higgs boson decaying into two exotic particles, which then themselves decay into many more particles – this is how an off-centre vertex could be produced. In fact, looking for off-centre vertices was proposed way back in 2006 as a way of detecting the Higgs boson, before it had been discovered (http://arxiv.org/abs/hep-ph/0605193)!

Since this process is not predicted by the Standard Model, if we see these in our detector then we will finally be able to realise the dream of obtaining direct evidence for a new theory of nature – opening our eyes to an entirely new realm of physics.

If these exotic decays are real, then they have already happened at the LHC and are sitting in the data we have right now, just waiting to be found by a keen pair of eyes. By helping with this project, you can take us one step closer to a deeper understanding of reality – to answering some of the greatest unsolved mysteries in the universe.

(Next time: ATLAS: How do particle detectors work?)