Synopsis: No Hint of Exotic Higgs Particles
In 2012, the ATLAS and CMS collaborations at the Large Hadron Collider (LHC) in Geneva discovered a Higgs boson that was consistent with the standard model of particle physics. However, some theories propose that other Higgs-like particles with different properties may exist alongside the standard model Higgs. A new analysis of data from Fermilab’s Tevatron outside of Chicago sets limits on some of these “exotic Higgs” particles.
The standard model predicts that the Higgs boson is a scalar particle, which means it has zero spin and even parity (describing how it behaves in a mirror reflection). The Higgs discovered at the LHC is a scalar particle, as verified in data where the particle decays into other bosons (W and Z bosons, as well as photons). It’s still possible, however, that an exotic Higgs boson of similar mass exists but decays preferentially through other channels.
The Tevatron, which shut down in 2011, studied proton-antiproton collisions at energies of tera-electron-volts, about a factor of below the LHC’s collision energy in 2012. In spite of this, the two Tevatron-based experiments, CDF and D0, uncovered evidence in 2012 of a Higgs boson decaying into fermions, specifically, a pair of bottom quarks. The two collaborations have again combined their data to check for exoticness in this fermion decay channel. The Tevatron data show no signal consistent with a Higgs boson having spin zero and odd parity (a so-called pseudoscalar) or spin and even parity (gravitonlike). The results are important for building the case that the Higgs boson seen in particle colliders is indeed the standard model Higgs.
This research is published in Physical Review Letters.