Scattering unitarity with effective dimension-6 operators. (5th December 2017)

• Record Type: Journal Article
• Authors: Ghosh, Swagata; Islam, Rashidul; Kundu, Anirban
• Is Part Of: Journal of physics. Volume 45:Number 1(2018:Jan.)
• Publication Date: 2017-12-05
• Subjects: Higgs physics -- unitarity bound -- beyond the Standard Model; Nuclear physics -- Periodicals; Particles (Nuclear physics) -- Periodicals; Physique nucléaire -- Périodiques; Particules (Physique nucléaire) -- Périodiques; Kernfysica; Elementaire deeltjes; 539.7
• DOI: 10.1088/1361-6471/aa9873
• Languages: English
• ISSNs: 0954-3899

Abstract

Abstract: The effects of physics beyond the Standard Model (SM) may be parametrized by a set of higher-dimensional operators leading to an effective theory. The introduction of these operators makes the theory nonrenormalizable, and one may reasonably expect a violation of unitarity in 2 → 2 scattering processes, depending on the values of the Wilson coefficients (WC) of the higher dimensional operators. Bounds on these coefficients may be obtained from demanding that there be no such unitarity violation below the scale of the effective theory. We show, at the lowest level, how the new operators affect the scattering amplitudes with longitudinal gauge bosons, scalars, and t t ̄ in the final state, and find that one may expect a violation of unitarity even at the LHC energies with small values of some of the new WC. For most of the others, such a violation needs large coefficients, indicating nonperturbative physics for the ultraviolet-complete theory, although a proper treatment necessitates the inclusion of even higher-dimensional operators. However, deviations from the SM expectations may be observed with even smaller values for these coefficients. We find that WW → WW, WW → ZZ, and ZZ → hh scatterings are the best possible channels to probe unitarity violations.