Abstract
A “Higgs factory”, an electron-positron collider with center-of-mass energy of about 250 GeV, will measure the cross section of the Higgsstrahlung process, e + e − → hZ, with sub-percent precision. This measurement is sensitive to a variety of new physics scenarios. In this paper, we study two examples. First, we compute corrections to the e + e − → hZ differential cross section in the effective field theory (EFT) approach, including the complete set of dimension-6 operators contributing to this process. These results are applicable to any model where the new physics mass scale is significantly above the weak scale. Second, we present a complete one-loop calculation of the effect of third-generation squarks, with arbitrary soft masses and mixing, on this cross section. This is expected to be the leading correction in natural supersymmetric models. We demonstrate the agreement between the full one-loop calculation and the EFT result in the limit of large stop masses. Finally, we estimate the discovery reach of the e + e − → hZ cross section measurement in the two models.
Highlights
We investigate the potential sensitivity of this measurement to new physics, assuming that precision of O(0.1–0.5%) can be reached at a Higgs factory
A very precise measurement of the Higgsstrahlung cross section can be performed at a future Higgs factory
We considered the potential of this measurement to search for new physics
Summary
The effects of any new physics appearing at a mass scale Λ on the Higgsstrahlung cross section can be described in terms compared to the center-of-mass eonfearngyE√ffesctaivned. Ldt ≈ 4500 fb−1, which would probably require combining data from multiple detectors as envisioned, for example, in the TLEP proposal.) Table 3 and figure 1 show the exclusion and discovery reaches in a new physics scenario where a single dim.-6 operator dominates For this estimate, we only used the total cross section measurement, and assumed that it is in exact agreement with the reference value computed in the (mZ, GF , α) basis. (ATLAS constraints on this vertex are very similar [39].) For most operators, the sensitivity of the Higgs factory is well in excess of the current bounds, the only exceptions being OBB and, for the conservative luminosity assumptions, OW B Another relevant question is how the Higgsstrahlung cross section will compare, in terms of new physics sensitivity, to various other observables that can be measured at. We emphasize that the relative size of dimension-6 operators depends on the details of new physics at the scale Λ, and the Higgsstrahlung cross section gives access to several operators not accessible to other measurements
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