skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: 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, π’ͺ(1 / Ξ› 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.  more » « less
Award ID(s):
2210498 1915409
PAR ID:
10437887
Author(s) / Creator(s):
; ; ;
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
More Like this
  1. ; (, Journal of High Energy Physics)
    A bstract We calculate pp β†’ β„“ + Ξ½, β„“ βˆ’ $$ \overline{\nu} $$ Ξ½ Β― to $$ \mathcal{O} $$ O (1 / Ξ› 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 / Ξ› 4 ) and $$ \mathcal{O} $$ O (1 / Ξ› 2 ) results for various kinematic regimes and assumptions about the Wilson coefficients. Results for Drell-Yan production pp β†’ β„“ + β„“ βˆ’ at $$ \mathcal{O} $$ O (1 / Ξ› 4 ) are also provided. Additionally, we develop the form for four fermion contact term contributions to pp β†’ β„“ + Ξ½, β„“ βˆ’ $$ \overline{\nu} $$ Ξ½ Β― , pp β†’ β„“ + β„“ βˆ’ of arbitrary mass dimension. This allows us to estimate the effects from even higher dimensional (dimension > 8) terms in the SMEFT framework. 
    more » « less
  2. ; ; (, Journal of High Energy Physics)
    A bstract We introduce a systematic method to classify the Standard Model Effective Field Theory (SMEFT) operators based on their CP properties with the Hilbert series techniques. Our method makes it possible to enumerate operators violating CP symmetry in a few seconds. We present the complete classification of dimension eight operators under CP transformation, and the number of CP-odd or CP-violating operators are listed up to dimension 14. We also provide a companion code in Form that allows anybody to reproduce our results. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Journal of High Energy Physics)
    A<sc>bstract</sc> A standard model effective field theory (SMEFT) analysis with dimension-six operators probing nonresonant new physics effects is performed in the Higgs-strahlung process, where the Higgs boson is produced in association with a W or Z boson, in proton-proton collisions at a center-of-mass energy of 13 TeV. The final states in which the W or Z boson decays leptonically and the Higgs boson decays to a pair of bottom quarks are considered. The analyzed data were collected by the CMS experiment between 2016 and 2018 and correspond to an integrated luminosity of 138 fbβˆ’1. An approach designed to simultaneously optimize the sensitivity to Wilson coefficients of multiple SMEFT operators is employed. Likelihood scans as functions of the Wilson coefficients that carry SMEFT sensitivity in this final state are performed for different expansions in SMEFT. The results are consistent with the predictions of the standard model. 
    more » « less
  4. ; ; ; (, Journal of High Energy Physics)
    null (Ed.)
    A bstract The Standard Model Effective Field Theory (SMEFT) theoretical framework is increasingly used to interpret particle physics measurements and constrain physics beyond the Standard Model. We investigate the truncation of the effective-operator expansion using the geometric formulation of the SMEFT, which allows exact solutions, up to mass-dimension eight. Using this construction, we compare the exact solution to the expansion at $$ \mathcal{O} $$ O ( v 2 / Ξ› 2 ), partial $$ \mathcal{O} $$ O ( v 4 / Ξ› 4 ) using a subset of terms with dimension-6 operators, and full $$ \mathcal{O} $$ O ( v 4 / Ξ› 4 ), where v is the vacuum expectation value and Ξ› is the scale of new physics. This comparison is performed for general values of the coefficients, and for the specific model of a heavy U(1) gauge field kinetically mixed with the Standard Model. We additionally determine the input-parameter scheme dependence at all orders in v/ Ξ›, and show that this dependence increases at higher orders in v/ Ξ›. 
    more » « less
  5. ; ; ; (, Journal of High Energy Physics)
    NA (Ed.)
    A<sc>bstract</sc> Observation of lepton number violation would represent a groundbreaking discovery with profound consequences for fundamental physics and as such, it has motivated an extensive experimental program searching for neutrinoless double beta decay. However, the violation of lepton number can be also tested by a variety of other observables. We focus on the possibilities of probing this fundamental symmetry within the framework of the Standard Model Effective Field Theory (SMEFT) beyond the minimal dimension-5. Specifically, we study the bounds on βˆ†L= 2 dimension-7 effective operators beyond the electron flavor imposed by all relevant low-energy observables and confront them with derived high-energy collider limits. We also discuss how the synergy of the analyzed multi-frontier observables can play a crucial role in distinguishing among different dimension-7 SMEFT operators. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email