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Minimal model for the WW-boson mass, (g−2)μ(g−2)μ​, h→μ+μ−h→μ+μ− and quark-mixing-matrix unitarity


Crivellin, Andreas; Kirk, Matthew; Thapa, Anil (2023). Minimal model for the WW-boson mass, (g−2)μ(g−2)μ​, h→μ+μ−h→μ+μ− and quark-mixing-matrix unitarity. Physical review D, 108(3):L031702.

Abstract

The SU(2)L triplet scalar with hypercharge Y=0 predicts a positive definite shift in the W mass, with respect to the Standard Model prediction, if it acquires a vacuum expectation value. As this new field cannot couple directly to Standard Model fermions (on its own), it has no significant impact on other low-energy precision observables and is weakly constrained by collider searches. In fact, the multilepton anomalies at the LHC even point toward new scalars that decay dominantly to W bosons, as the neutral component of the triplet naturally does. In this article, we show that with a minimal extension of the scalar triplet model by a heavy vectorlike lepton, being either (I) an SU(2)L doublet with Y=−1/2 or (II) an SU(2)L triplet with Y=−1, couplings of the triplet to Standard Model leptons are possible. This minimal extension can then provide, in addition to the desired positive shift in the W mass, a chirally enhanced contribution to (g−2)μ. In addition, versions (I) and (II) can improve on Z→μ+μ− and alleviate the tension in first-row Cabibbo-Kobayashi-Maskawa unitarity (known as the Cabibbo angle anomaly), respectively. Finally, both options, in general, predict sizable changes of h→μ+μ−, i.e., much larger than most other (g−2)μ explanations where only O(%) effects are expected, making this channel a smoking gun signature of our model.

Abstract

The SU(2)L triplet scalar with hypercharge Y=0 predicts a positive definite shift in the W mass, with respect to the Standard Model prediction, if it acquires a vacuum expectation value. As this new field cannot couple directly to Standard Model fermions (on its own), it has no significant impact on other low-energy precision observables and is weakly constrained by collider searches. In fact, the multilepton anomalies at the LHC even point toward new scalars that decay dominantly to W bosons, as the neutral component of the triplet naturally does. In this article, we show that with a minimal extension of the scalar triplet model by a heavy vectorlike lepton, being either (I) an SU(2)L doublet with Y=−1/2 or (II) an SU(2)L triplet with Y=−1, couplings of the triplet to Standard Model leptons are possible. This minimal extension can then provide, in addition to the desired positive shift in the W mass, a chirally enhanced contribution to (g−2)μ. In addition, versions (I) and (II) can improve on Z→μ+μ− and alleviate the tension in first-row Cabibbo-Kobayashi-Maskawa unitarity (known as the Cabibbo angle anomaly), respectively. Finally, both options, in general, predict sizable changes of h→μ+μ−, i.e., much larger than most other (g−2)μ explanations where only O(%) effects are expected, making this channel a smoking gun signature of our model.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Scopus Subject Areas:Physical Sciences > Nuclear and High Energy Physics
Language:English
Date:25 August 2023
Deposited On:29 Dec 2023 09:59
Last Modified:28 Jun 2024 03:31
Publisher:American Physical Society
ISSN:2470-0010
OA Status:Hybrid
Publisher DOI:https://doi.org/10.1103/physrevd.108.l031702
  • Content: Published Version
  • Language: English
  • Licence: Creative Commons: Attribution 4.0 International (CC BY 4.0)