CMS Search for New Physics in Four-Jet Events with Bottom
The CMS collaboration reports a search for new particles decaying into pairs of jets containing bottom quarks, using 13 TeV proton-proton collision data.
The CMS collaboration has conducted a novel search for new physics in events containing four jets, two of which must originate from bottom quarks. The analysis uses a data sample corresponding to an integrated luminosity of 136 inverse femtobarns, collected by the CMS detector in proton-proton collisions at a center-of-mass energy of 13 TeV. Results are presented for both nonresonant production and for scenarios involving an intermediate resonant state.
This is the first search at the Large Hadron Collider for the resonant production of pairs of fully resolved dijet resonances where the final state includes bottom quark jets. All resonances considered in the search correspond to hypothetical particles not predicted by the Standard Model of particle physics.
Search Strategy and Observed Excesses
The team looked for pair-produced dijet resonances of identical mass, with each resonance decaying into a bottom quark and a light-flavor quark. For the nonresonant production channel, the most significant excess in the data occurs at an average dijet mass of 1.0 TeV. The local statistical significance of this excess is 2.1 standard deviations.
In the search for resonant production, where the four-jet system originates from a single, heavier particle, the most notable excess is found at a four-jet resonance mass of 3.1 TeV and a dijet resonance mass of 1.3 TeV. This feature has a local significance of 2.6 standard deviations. The CMS collaboration notes that such fluctuations are consistent with expected background variations.
Exclusion Limits on New Particles
The results are used to set upper limits on the production cross-sections for these hypothetical processes. For nonresonant production, the analysis excludes the pair production of top squarks-the supersymmetric partners of top quarks-with masses between 0.5 and 0.8 TeV. This extends previous searches for R-parity-violating supersymmetric decays that produce strange and bottom quarks.
For the resonant production model, interpreted through a diquark-to-diquarks theoretical framework, the results set limits at a 95% confidence level. The analysis excludes the existence of the heavier diquark state for masses between 2 and 7 TeV, assuming a specific coupling strength.
Implications for Physics Beyond the Standard Model
The search probes specific signatures predicted by various theories of physics beyond the Standard Model. The requirement of bottom quarks in the final state helps target models where new particles have a preferential coupling to the third generation of fermions. While no definitive evidence of new particles is found, the established exclusion limits provide key guidance for refining theoretical models and planning future searches at higher luminosities and energies.
The collaboration has reported upper limits on the production of both four-jet and dijet resonances featuring bottom jets. The full details of the statistical analysis and the exclusion contours are provided in the CMS paper, which has been submitted to the arXiv preprint server.
