Search for Resonances in the Dijet Mass Spectrum from 7 TeV pp Collisions at CMS

Abstract

A search for narrow resonances with a mass of at least 1 TeV in the dijet mass spectrum is performed using pp collisions at sqrt(s)=7 TeV corresponding to an integrated luminosity of 1 inverse femtobarn, collected by the CMS experiment at the LHC. No resonances are observed. Upper limits at the 95% confidence level are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, and gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% confidence level: string resonances with mass less than 4.00 TeV, E6 diquarks with mass less than 3.52 TeV, excited quarks with mass less than 2.49 TeV, axigluons and colorons with mass less than 2.47 TeV, and W' bosons with mass less than 1.51 TeV.

Figures (6)

• Figure 1: The number of events observed versus dijet mass for wide jets (solid circles), particle flow AK7 jets (open boxes), and calorimeter AK7 jets (X symbols).
• Figure 2: Dijet mass spectrum from wide jets (points) compared to a smooth fit (solid) and to predictions refPYTHIA including detector simulation of QCD (short-dashed), excited quark signals (dot-dashed), and string resonance signals (long-dashed). The QCD prediction has been normalized to the data (see text). The error bars are statistical only. The shaded band shows the systematic uncertainty in the jet energy scale (JES). The bin-by-bin significance of the data-fit difference (see text) is shown at bottom.
• Figure 3: Ratio (points) between the dijet mass data from wide jets and the smooth fit, compared to the simulated ratios for excited quark signals (dot-dashed) in the CMS detector. The error bars represent statistical uncertainties only.
• Figure 4: Simulation of the expected dijet mass distributions in the CMS detector from a narrow 2.0 TeV resonance of type quark-quark (solid), quark-gluon (dashed), and gluon-gluon (dotted) using wide jet reconstruction, and of type gluon-gluon using anti-$k_T$ jet reconstruction with distance parameter $R=0.7$ (dot-dash).
• Figure 5: The 95% CL upper limits on $\sigma\times B\times A$ for dijet resonances of type gluon-gluon (open circles), quark-gluon (solid circles), and quark-quark (open boxes), compared to theoretical predictions for string resonances Anchordoqui:2008di, $\hbox{E}_6$ diquarks ref_diquark, excited quarks ref_qstar, axigluons ref_axi, colorons ref_coloron, new gauge bosons $\hbox{W}^{\prime}$ and $\hbox{Z}^{\prime}$ref_gauge, and Randall-Sundrum gravitons ref_rsg.