A bstract We calculate pp → ℓ + ν, ℓ − $$ \overline{\nu} $$ ν ¯ to $$ \mathcal{O} $$ O (1 / Λ 4 ) within the Standard Model Effective Field Theory (SMEFT) framework. In particular, we calculate the four-fermion contribution from dimension six and eight operators, which dominates at large center of mass energy. We explore the relative size of the $$ \mathcal{O} $$ O (1 / Λ 4 ) and $$ \mathcal{O} $$ O (1 / Λ 2 ) results for various kinematic regimes and assumptions about the Wilson coefficients. Results for Drell-Yan production pp → ℓ + ℓ − at $$ \mathcal{O} $$ O (1 / Λ 4 ) are also provided. Additionally, we develop the form for four fermion contact term contributions to pp → ℓ + ν, ℓ − $$ \overline{\nu} $$ ν ¯ , pp → ℓ + ℓ − of arbitrary mass dimension. This allows us to estimate the effects from even higher dimensional (dimension > 8) terms in the SMEFT framework.
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This content will become publicly available on June 1, 2024
Opportunistic CP violation
A bstract In the electroweak sector of the Standard Model, CP violation arises through a very particular interplay between the three quark generations, as described by the Cabibbo-Kobayashi-Maskawa (CKM) mechanism and the single Jarlskog invariant J 4 . Once generalized to the Standard Model Effective Field Theory (SMEFT), this peculiar pattern gets modified by higher-dimensional operators, whose associated Wilson coefficients are usually split into CP-even and odd parts. However, CP violation at dimension four, i.e., at the lowest order in the EFT expansion, blurs this distinction: any Wilson coefficient can interfere with J 4 and mediate CP violation. In this paper, we study such interferences at first order in the SMEFT expansion, 𝒪(1 / Λ 2 ), and we capture their associated parameter space via a set of 1551 linear CP-odd flavor invariants. This construction describes both new, genuinely CP-violating quantities as well as the interference between J 4 and CP-conserving ones. We call this latter possibility opportunistic CP violation . Relying on an appropriate extension of the matrix rank to Taylor expansions, which we dub Taylor rank , we define a procedure to organize the invariants in terms of their magnitude, so as to retain only the relevant ones at a given precision. We explore how this characterization changes when different assumptions are made on the flavor structure of the SMEFT coefficients. Interestingly, some of the CP-odd invariants turn out to be less suppressed than J 4 , even when they capture opportunistic CPV, demonstrating that CP-violation in the SM, at dimension 4, is accidentally small.
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- Award ID(s):
- 2210498
- NSF-PAR ID:
- 10437887
- Date Published:
- Journal Name:
- Journal of High Energy Physics
- Volume:
- 2023
- Issue:
- 6
- ISSN:
- 1029-8479
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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