Effective field theory in the top sector: Do multijets help?

Christoph Englert,Michael Russell,Chris D White

doi:10.1103/physrevd.99.035019

Christoph Englert, Michael Russell + Show 1 more

Open Access

https://doi.org/10.1103/physrevd.99.035019

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Abstract

Many studies of possible new physics employ effective field theory (EFT), whereby corrections to the Standard Model take the form of higher-dimensional operators, suppressed by a large energy scale. Fits of such a theory to data typically use parton level observables, which limits the datasets one can use. In order to theoretically model search channels involving many additional jets, it is important to include tree-level matrix elements matched to a parton shower algorithm, and a suitable matching procedure to remove the double counting of additional radiation. There are then two potential problems: (i) EFT corrections are absent in the shower, leading to an extra source of discontinuities in the matching procedure; (ii) the uncertainty in the matching procedure may be such that no additional constraints are obtained from observables sensitive to radiation. In this paper, we review why the first of these is not a problem in practice, and perform a detailed study of the second. In particular, we quantify the additional constraints on EFT expected from top pair plus multijet events, relative to inclusive top pair production alone.

Highlights

The search for physics beyond the Standard Model (BSM) is the most pressing problem in particle physics, especially given the ongoing experimental program at the Large Hadron Collider
The lack of clear evidence for BSM physics far motivates the use of effective field theory [1,2,3,4,5,6], in which one characterizes corrections to the SM Lagrangian by gauge-invariant higher-dimensional operators built from the SM fields
We have considered the issue of whether observables relating to additional jet radiation in top pair production provide a useful input to global fits of effective field theory (EFT) in the top sector

Summary

Introduction

The search for physics beyond the Standard Model (BSM) is the most pressing problem in particle physics, especially given the ongoing experimental program at the Large Hadron Collider. The lack of clear evidence for BSM physics far motivates the use of effective field theory [1,2,3,4,5,6] (for a comprehensive review see [7]), in which one characterizes corrections to the SM Lagrangian by gauge-invariant higher-dimensional operators built from the SM fields. This has the advantage of being manifestly model independent, but is only applicable if the lowest energy scale associated with the new physics is above the typical energies probed by the collider of interest.

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