Abstract
Several searches for new physics at the LHC require a fixed number of signal jets, vetoing events with additional jets from QCD radiation. As the probed scale of new physics gets much larger than the jet-veto scale, such jet vetoes strongly impact the QCD perturbative series, causing nontrivial theoretical uncertainties. We consider slepton pair production with 0 signal jets, for which we perform the resummation of jet-veto logarithms and study its impact. Currently, the experimental exclusion limits take the jet-veto cut into account by extrapolating to the inclusive cross section using parton shower Monte Carlos. Our results indicate that the associated theoretical uncertainties can be large, and when taken into account have a sizeable impact already on present exclusion limits. This is improved by performing the resummation to higher order, which allows us to obtain accurate predictions even for high slepton masses. For the interpretation of the experimental results to benefit from improved theory predictions, it would be useful for the experimental analyses to also provide limits on the unfolded visible 0-jet cross section.
Highlights
With jets in the final state are more complicated, as the jet transverse momenta introduce additional kinematic scales in the cross section, and are left for future work
We have evaluated the parametric parton distribution functions (PDFs) uncertainty for the resummed 0-jet cross section, which is explained in the discussion of figure 10 in section 3 below
We discuss our results for the 0-jet cross section, σ0, for slepton production at 8 and 13 TeV and discuss the implications on current slepton exclusion limits, using the ATLAS analysis in ref. [5] as a representative example
Summary
We discuss the calculation in some detail. We utilize the jet-pT resummation of ref. [25] using soft-collinear effective theory (SCET) [47,48,49,50,51,52]. The hard function Hqqdescribes the short-distance scattering process, qq → ̃ ̃ → χ01 χ01 It contains all the analysis cuts applied on the slepton final state but not the jet veto. The key to obtaining a resummed prediction for the cross section is that each individual term can be made small by an appropriate choice of the renormalization scale μ and rapidity renormalization scale ν, namely μH ∼ Q ∼ 2m, μB ∼ μS ∼ pcTut , νB ∼ Q ∼ 2m, νS ∼ pcTut. By evaluating each of the hard, beam, and soft functions at their natural scale, they contain no large logarithms. The RGE is illustrated in figure 3 and the formulae needed for carrying it out are collected in appendix B
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