Looking for additional Higgs-like particles

Distribution of events, in the signal region. The horizontal axis shows bb invariant mass. The figure shows the data, the signal and four different backgrounds. The signal hypothesis is: a total cross section of 250 femtobarns, a heavy neutral Higgs boson of mass 500 GeV/c2 and lighter charged Higgs boson H± of mass 300 GeV/c2 along with the Standard Model Higgs boson.

An exciting part of the much-celebrated particle discovery recently made at the Large Hadron Collider is that it is only the first step on the road to understanding the Higgs boson. Much remains to be discovered about the particle and its properties; knowing its mass is just the beginning. The next step is to study how the particle behaves and how it fits into the big picture of physics as a whole. One of the biggest questions is whether the Higgs boson theorized by the Standard Model (SM) is the only Higgs boson, or rather whether the SM Higgs boson is part of a larger family of particles.

In this analysis CDF physicists investigate a phenomenological model. We assume a heavy neutral Higgs boson decays into a lighter charged intermediate Higgs boson and a charged W, and that the charged intermediate Higgs boson then decays into the SM Higgs and a charged W. The net result of this cascade decay is a final state consisting of two bottom quarks and two W bosons. This model, called a two-Higgs boson doublet, involves four Higgs boson particles: a new neutral heavy Higgs boson, a neutral SM Higgs boson (having a mass of 126 GeV/c2), and two intermediate charged Higgs bosons.

By careful comparison to a SM background-only theory (see above figure), we set the world’s first upper limits on a two-Higgs-doublet cascade decay. Using a data sample corresponding to an integrated luminosity of 8.7 inverse femtobarns, we find that the observed data are consistent with SM backgrounds. While our analysis does not explicitly exclude this model from the realm of possibility, it does offer the first look and upper limit on the possible contributions from this process. It is hoped that this process will be examined in more detail at the LHC.

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edited by Andy Beretvas

The CDF physicists responsible for this analysis are all from the University of California, Irvine. Top row from left: Adam Johnstone, Kanishka Rao. Bottom row, from left: Alan Truong, Daniel Whiteson.