Enhancing the sensitivity to new physics in the t(t)over-bar invariant mass distribution

We propose selection cuts on the LHC t (t) over bar production sample which should enhance the sensitivity to new physics signals in the study of the t (t) over bar invariant mass distribution. We show that selecting events in which the t (t) over bar object has little transverse and large longitudinal momentum enlarges the quark-fusion fraction of the sample and therefore increases its sensitivity to new physics which couples to quarks and not to gluons. We find that systematic error bars play a fundamental role and assume a simple model for them. We check how a non-visible new particle would become visible after the selection cuts enhance its resonance bump. A final realistic analysis should be done by the experimental groups with a correct evaluation of the systematic error bars.