Abstract
We report on a search for a spin-zero non-standard-model particle in proton-antiproton collisions collected by the Collider Detector at Fermilab at a center-of-mass-energy of 1.96 TeV. This particle, the $\phi$ boson, is expected to decay into a bottom-antibottom quark pair and to be produced in association with at least one bottom quark. The data sample consists of events with three jets identified as initiated by bottom quarks and corresponds to $5.4~\text{fb}^{-1}$ of integrated luminosity. In each event, the invariant mass of the two most energetic jets is studied by looking for deviations from the multijet background, which is modeled using data. No evidence is found for such particle. Exclusion upper limits ranging from 20 to 2 pb are set for the product of production cross sections times branching fraction for hypothetical $\phi$ boson with mass between 100 and 300 GeV/$c^2$. These are the most stringent constraints to date.
Highlights
The discovery of a Higgs boson [1,2] completes the standard model (SM), but does not exclude the existence of yet-unknown particles that could provide direct indication of non-SM physics
The low-energy quantum chromodynamics (QCD) calculations that would be needed for reliable rate predictions of these events are intractable, it is not possible to rely on direct theoretical predictions
The two-dimensional distribution in the variables m12 and xtags for the 5616 triple-tagged events is fitted under the hypothesis that no signal is present
Summary
The discovery of a Higgs boson [1,2] completes the standard model (SM), but does not exclude the existence of yet-unknown particles that could provide direct indication of non-SM physics. Non-SM spin-0 resonances with SM Yukawa-like [3] couplings would decay predominantly to heavy quarks and, if their masses do not exceed twice the top-quark mass, mostly to bottomantibottom (bb ) quark pairs Such particles are foreseen, e.g., in minimal supersymmetric extensions of the SM (MSSM) [4], where two scalar Higgs doublets exist, leading to five physical Higgs bosons, of which three are electrically neutral and collectively denoted as φ. Because of the higher collision energy, which leads to a larger multijet production rate, searches for a particle with mass smaller than 200 GeV=c2 at the LHC are limited by the difficulties in selecting online low-energy jets This analysis investigates the reported 2σ deviation using completely independent data with the same ppinitial state in the low-mass range of 100 to 300 GeV=c2.
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