The run 2 dijet mass spectrum ( eps, ps, gif) begins at 180 GeV and falls steeply. The highest mass event ( pdf, ppt) has a dijet mass of 1364 GeV. Comparing the spectrum in run 1 and run 2 on a log scale ( eps, ps, gif) we see that the run 2 cross section at sqrt(s)=1.96 TeV is everywhere above the run 1 spectrum at sqrt(s)=1.80 TeV. The ratio of the cross section in run 2 to that in run 1 ( eps, ps, gif) compares favorably with a lowest order parton level calculation. From the same plot with an expanded scale ( eps, ps, gif) we see the cross section for the highest mass dijet events is up to 10 times higher in run 2 than in run 1.
To search for new particles ( eps, ps, gif) we fit the mass spectrum with a simple background parameterization and search for bumps comparable with our mass resolution. The fit on a log scale ( eps, ps, gif), the fractional difference between the data and the fit ( eps, ps, gif), and the statistical residuals between the data and the fit ( eps, ps, gif), show there is no significant evidence for a new particle signal. We set 95% CL upper limits on the cross section times branching ratio for narrow dijet resonances and compare them with the predictions for axigluons, flavor universal colorons, excited quarks, Color Octet Technirhos, E6 diquarks, W' and Z'. The limit plot is availale in black and white ( eps, ps, jpeg) and color . ( eps, ps, jpeg)
In run 2 we exclude axigluons or flavor universal colorons for masses
between 200 and 1130 GeV.
The published run 1 exclusion was of mass between
200 and 980 GeV.
In run 2 we exclude excited quarks with mass between 200 and 760 GeV.
The published run 1 exclusion was of mass between 200 and 570 GeV and
between 580 and 760 GeV.
In run2 we exclude color octet technirhos between 260 and 640 GeV.
The pulished run 1 exclusion was of mass between 260 and 480 GeV.
In run 2 we exclude E6 diquarks with mass between 280 and 420 GeV.
The published run 1 exclusion was of mass between 290 and 420 GeV.
In run 2 we exclude W' with mass between 300 and 410 GeV.
The published run 1 exclusion was of mass between 300 and 420 GeV.
We do not exclude a Z' in dijet decays in run 2, and there was no exclusion from run 1 either.
