Primary authors:
A. Annovi^{a}, P. Catastini^{b},
V. Cavaliere^{c}, L. Ristori^{d}

a: INFN Frascati, Italy; b: Harvard University; c: University of Illinois at Urbana-Champaign; d: INFN Pisa, Italy and Fermilab

a: INFN Frascati, Italy; b: Harvard University; c: University of Illinois at Urbana-Champaign; d: INFN Pisa, Italy and Fermilab

Here we update this previous result and present further studies of the excess using additional data collected through to November 2010 corresponding to an integrated luminosity of 7.3 fb

In evaluating the significance of the excess we assume that the excess can be modeled with an additional Gaussian component. The Gaussian assumption is a simplified model since any dijet resonance is expected to have an asymmetric distribution with a more pronounced tail for masses below the peak due for example to QCD radiation and out-of-cone jet energy. Moreover, the exact shape of a dijet resonance depends on the specific physics process and the heavy flavor content of the decay products. To retain model independence and due to the relatively low statistics of the excess, we assume a simple Gaussian model for evaluating the significance of the excess.

The p-value with only statistical uncertainties is 9.49 x
10^{-7}, corresponding to 4.76 standard deviations.

A comparison of SHERPA and ALPGEN M_{JJ} distributions is
shown in Fig. 6.
The (statistical-only) significance of the excess when the W+jets
shape is modeled by SHERPA
is 3.8 standard deviations compared to 4.8 with ALPGEN. Further comparisons of
kinematics distributions between the two generators are here.

- 0 T : neither of the two jets has a positive SECVTX Tight tag.
- 1 T : at least one of the two jets has a positive SECVTX Tight tag.
- 2 T : both jets have a positive SECVTX Tight tag.
- 0 L : neither of the two jets has a positive SECVTX Loose tag.
- 1 L : at least one of the two jets has a positive SECVTX Loose tag.
- 2 L : both jets have a positive SECVTX Loose tag.

We have considered alternate models and varied cuts to enhance backgrounds to demonstrate the integrity of our background estimates.

We a sub-samples that are enriched in t-tbar by selecting events with at compare their kinematic properties to predictions.

We compare NLO to LO predictions for the top background and determine the significance when the t-tbar background is increased by 50%.

We apply different Δφ

The ratio of the leading-jet E

In our original publication we studied the ΔR

We have studied the dijet mass spectrum as a function of time and instantaneous luminosity. The excess appears in all data sub-samples and, within statistical uncertainties, the corresponding number of events scales with the integrated luminosity. The charged track multiplicity of the jets is not characterised by low multiplicities as would be expected from τ leptons. Furthermore the EM fraction of the jets does not support the hypothesis that the jets are due to misidentified electrons.