Search for pair-production of new heavy colored particles \\ decaying to pairs of jets in p p̅ collisions at {\bf √s=1.96 TeV}

Daniel Whiteson, Eric Albin, UC Irvine
Ankush Mitra, Academia Sinica

Abstract:
We present a search for the pair-production of a heavy colored particle Y which decays to a pair of quarks or gluons, leading to a final state with four hadronic jets. We consider both non-resonant production via an intermediate gluon as well as resonant production via a heavy intermediate colored particle X. In data collected by the CDFII experiment in p̅p collisions at √s=1.96 TeV corresponding to integrated luminosity of 6.6 fb^-1, we find the data to be consistent with standard model predictions. We report limits on σ (p̅p→ YY → jjjj) versus m_Y and σ(p p̅→ X→ YY → jjjj) versus m_X and m_Y. In the context of non-resonant coloron C production, we exclude m_C between 50 and 125 GeV/c²; in an R-parity-violating stop quark t˜ hypothesis we exclude m_t˜ between 50 and 100 GeV/c². In the context of hyperpions produced via an axi-gluon resonance A, we exclude m_A between 100 and 400 GeV/² for coupling values preferred by the CDF top A_fb anomaly.

The Conference note.

Feynman diagram for non-resonant pair-production of Y, with subsequent decays to pairs of gluons.
Feynman diagram for resonant pair-production via X of Y, with subsequent decays to pairs of gluons.
Overall efficiency, including trigger and selection requirements. Efficiency for several simulated non-resonant YY→ jj jj samples with varying m_Y. The shaded band shows the uncertainty.
Overall efficiency, including trigger and selection requirements. Efficiency for several simulated resonant X→ YY→ jj jj samples with varying m_Y. Uncertainties, not shown, are similar to those in the non-resonant case.
Reconstructed mean di-jet mass in events with four jets. Top pane shows the events, with a parametric fit and several signal hypotheses overlaid. Bottom pane shows the relative difference between the observed data and the fit in each bin.
Reconstructed mean four-jet mass in events with four jets. Top pane shows the events, with a parametric fit and several signal hypotheses overlaid. Bottom pane shows the relative difference between the observed data and the fit in each bin.
Upper limits at 95\% CL on σ (p p̅→ YY → jjjj) versus m_Y in the non-resonant analysis. Two signal hypotheses are shown, see text for details.
Upper limits at 95\% CL on σ (p p̅→ X→ YY → jjjj) versus m_X and m_Y. Circles indicate the grid of simulated samples where limits are evaluated; intervening values are interpolated.
Reconstructed average di-jet mass for several simulated non-resonant YY→ jj jj samples with varying m_Y.
Reconstructed four-jet mass for several simulated resonant X→ YY→ jj jj samples with varying m_X for m_Y=50 GeV/c².
Upper limits at 95\% CL on σ (p p̅→ YY → jjjj) versus m_X with m_Y=50 GeV/c² in the resonant analysis. An axi-gluon signal hypothesis is shown, see text for details.
Observed and expected 95% CL upper limits on σ(p p̅→ YY → jjjj) for several values of m_Y. Also shown are theoretical predictions for coloron pair production or stop-quark pair production with R-parity violating decay t ˜ → qq
Observed and expected 95% CL upper limits on σ(p p̅ → X→ YY → jjjj) for several values of m_Y and m_X. Also shown are theoretical predictions for axi-gluon production assuming coupling to quarks of C_q=0.4