Journal Article

A case study of SMEFT O 1 / Λ 4 $$ \\mathcal{O}\\left(1/{\\Lambda}^4\\right) $$ effects in diboson processes: pp → W ±(ℓ ± ν)γ

Adam Martin

2024

Overview

Abstract In this paper we explore pp → W ± (ℓ ± ν)γ to O 1 / Λ 4 $$ \\mathcal{O}\\left(1/{\\Lambda}^4\\right) $$ in the SMEFT expansion. Calculations to this order are necessary to properly capture SMEFT contributions that grow with energy, as the interference between energy-enhanced SMEFT effects at O 1 / Λ 2 $$ \\mathcal{O}\\left(1/{\\Lambda}^2\\right) $$ and the Standard Model is suppressed. We find that there are several dimension eight operators that interfere with the Standard Model and lead to the same energy growth, ~ O E 4 / Λ 4 $$ \\mathcal{O}\\left({E}^4/{\\Lambda}^4\\right) $$ , as dimension six squared. While energy-enhanced SMEFT contributions are a main focus, our calculation includes the complete set of O 1 / Λ 4 $$ \\mathcal{O}\\left(1/{\\Lambda}^4\\right) $$ SMEFT effects consistent with U(3)5 flavor symmetry. Additionally, we include the decay of the W ± → ℓ ± ν, making the calculation actually q ¯ q ′ → ℓ ± νγ $$ \\overline{q}{q}^{\\prime}\\to {\\ell}^{\\pm}\\nu \\gamma $$ . As such, we are able to study the impact of non-resonant SMEFT operators, such as L † σ ¯ μ τ I L Q † σ ¯ ν τ I Q $$ \\left({L}^{\\dagger }{\\overline{\\sigma}}^{\\mu }{\\tau}^IL\\right)\\left({Q}^{\\dagger }{\\overline{\\sigma}}^{\\nu }{\\tau}^IQ\\right) $$ B μν , which contribute to q ¯ q ′ → ℓ ± νγ $$ \\overline{q}{q}^{\\prime}\\to {\\ell}^{\\pm}\\nu \\gamma $$ directly and not to q ¯ q ′ → W ± γ $$ \\overline{q}{q}^{\\prime}\\to {W}^{\\pm}\\gamma $$ . We show several distributions to illustrate the shape differences of the different contributions.

• Publisher: SpringerOpen
• Subject: Electroweak Precision Physics / SMEFT