The Higgs boson lives for an extremely short time before it transforms into other particles. It is through the detection of some of these decay products which are the unique particle has first been spotted in particle collisions at the Large Hadron Collider.
But what if the Higgs boson also decayed into unexpected. New particles that were invisible to the LHC detectors. This includes particles that may constitute the dark matter permeating the universe. The ATLAS and CMS collaborations at the LHC have explored this possibility in two recent studies. They set stringent new upper bounds on the fraction of Higgs bosons decaying into invisible particles.
The Higgs boson decays indirectly into known invisible particles, according to the Standard Model of particle physics. The massless particles called neutrinos. Dark matter is made up of particles interacting too weakly to be detected. It is suspected by many physicists. The dark-matter particle could interact with the Higgs boson. It allows the Higgs boson to decay into it. It will increase the fraction of invisible Higgs-boson decays.
The ATLAS and CMS collaborations searched for invisible Higgs-boson decays in proton-proton collision data collected during the second run of the LHC, in their latest independent investigations. Both teams looked for a particular type of collision event. A Higgs boson is produced by a process known as vector-boson fusion. Then it decays into invisible particles.
These vector-boson-fusion events contain additional sprays of particles emitted towards either end of the particle detectors. It made this mode of Higgs-boson production easier to spot than the other modes. Together with the “missing energy” in the collision products that the invisible particles would carry away. These sprays and their properties provide distinctive signatures of such invisible Higgs-boson events.
The ATLAS and CMS searches revealed no instances of these invisible Higgs-boson events. It would exceed the expected number of background events mimicking the desired events. They also showed that the Higgs boson cannot decay into invisible particles more often than a certain percentage of time. It is 15% for ATLAS and 18% for CMS. It is compared to an expected percentage of 10% for both ATLAS and CMS. It was based on Standard Model computer simulations.
