Invariant-mass distribution of jet pairs produced in association with aWboson inpp¯collisions at

Abstract

We report on a study of the dijet invariant-mass distribution in events with one identified lepton, a significant imbalance in the total event transverse momentum, and two jets. This distribution is sensitive to the possible production of a new particle in association with a W boson, where the boson decays leptonically. We use the full data set of proton-antiproton collisions at 1.96 TeV center-of-mass energy collected by the Collider Detector at the Fermilab Tevatron, corresponding to an integrated luminosity of 8.9 fb −1 . The data are found to be consistent with standard model expectations, and a 95% confidence level upper limit is set on the production cross section of a W boson in association with a new particle decaying into two jets.

Cautionary tale of mismeasured tails fromq/gbias

“…In this subsection we attempt to understand the effect of a relative mis-measurement between q and g initiated jets. The reasons for this study are twofold: first, while Delphes includes tower-by tower resolution functions, these may be insufficient to capture quark vs. gluon jet differences at the substructure level; second, differences between quark and gluon jets have explained excesses in the past [39] and are therefore worth exploring. The analyses in this section may appear to be rather naive.…”

“…and may be insufficient for detailed substructure variables. Also, given that the inability of Monte Carlo programs to adequately describe the different detector response to quark vs. gluon jets has been used in the past to explain excesses -most notably the W + jj excess observed by CDF in 2011 [39,40] -it is worth investigating the robustness of the ATLAS analysis in the presence of slight relative q/g mismeasurement.…”

Extraordinary claims: the 0.000029% solution

“…In the same year the CDF collaboration showed a large, 4σ signal at 145 GeV in the mass distribution of jet pairs produced in association with leptonic W boson decays in the Tevatron 1.96 TeV proton-antiproton collisions [17]. The effect grew with data size and was clearly systematical in nature; the collaboration investigated it for over two years before finally understanding it as due to the combination of background contaminations and energy response differences in quark and gluon jets [18]. In light of the above information, one might be tempted to see an intriguing pattern in the correspondence between the parity of claimed significances of the effects and their genuinity, as shown in Table 1.…”