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2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Andreas Crivellin ◽  
Martin Hoferichter ◽  
Matthew Kirk ◽  
Claudio Andrea Manzari ◽  
Luc Schnell

Abstract New-physics (NP) constraints on first-generation quark-lepton interactions are particularly interesting given the large number of complementary processes and observables that have been measured. Recently, first hints for such NP effects have been observed as an apparent deficit in first-row CKM unitarity, known as the Cabibbo angle anomaly, and the CMS excess in $$ q\overline{q} $$ q q ¯ → e+e−. Since the same NP would inevitably enter in searches for low-energy parity violation, such as atomic parity violation, parity-violating electron scattering, and coherent neutrino-nucleus scattering, as well as electroweak precision observables, a combined analysis is required to assess the viability of potential NP interpretations. In this article we investigate the interplay between LHC searches, the Cabibbo angle anomaly, electroweak precision observables, and low-energy parity violation by studying all simplified models that give rise to tree-level effects related to interactions between first-generation quarks and leptons. Matching these models onto Standard Model effective field theory, we derive master formulae in terms of the respective Wilson coefficients, perform a complete phenomenological analysis of all available constraints, point out how parity violation can in the future be used to disentangle different NP scenarios, and project the constraints achievable with forthcoming experiments.


2021 ◽  
Vol 136 (9) ◽  
Author(s):  
S. Heinemeyer ◽  
S. Jadach ◽  
J. Reuter

AbstractHigh-precision experimental measurements of the properties of the Higgs boson at $$\sim 125$$ ∼ 125  GeV as well as electroweak precision observables such as the W-boson mass or the effective weak leptonic mixing angle are expected at future $$e^+e^-$$ e + e - colliders such as the FCC-ee. This high anticipated precision has to be matched with theory predictions for the measured quantities at the same level of accuracy. We briefly summarize the status of these predictions within the standard model and of the tools that are used for their determination. We outline how the theory predictions will have to be improved in order to reach the required accuracy, and also comment on the simulation frameworks for the Higgs and EW precision program.


2021 ◽  
Vol 81 (8) ◽  
Author(s):  
B. C. Allanach ◽  
J. Eliel Camargo-Molina ◽  
Joe Davighi

AbstractWhile it is known that third family hypercharge models can explain the neutral current B-anomalies, it was hitherto unclear whether the $$Z-Z^\prime $$ Z - Z ′ mixing predicted by such models could simultaneously fit electroweak precision observables. Here, we perform global fits of several third family hypercharge models to a combination of electroweak data and those data pertinent to the neutral current B-anomalies. While the Standard Model is in tension with this combined data set with a p-value of .0007, simple versions of the models (fitting two additional parameters each) provide much improved fits. The original Third Family Hypercharge Model, for example, has a p-value of $${.065}$$ . 065 , with $$\sqrt{\Delta \chi ^2}=6.5\sigma $$ Δ χ 2 = 6.5 σ .


2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Víctor Bresó-Pla ◽  
Adam Falkowski ◽  
Martín González-Alonso

Abstract We study the forward-backward asymmetry AFB in pp → ℓ+ℓ− at the Z peak within the Standard Model Effective Field Theory (SMEFT). We find that this observable provides per mille level constraints on the vertex corrections of the Z boson to quarks, which close a flat direction in the electroweak precision SMEFT fit. Moreover, we show that current AFB data is precise enough so that its inclusion in the fit improves significantly LEP bounds even in simple New Physics setups. This demonstrates that the LHC can compete with and complement LEP when it comes to precision measurements of the Z boson properties.


2021 ◽  
Vol 81 (7) ◽  
Author(s):  
A. Accardi ◽  
T. J. Hobbs ◽  
X. Jing ◽  
P. M. Nadolsky

AbstractExperimental measurements in deep-inelastic scattering and lepton-pair production on deuterium targets play an important role in the flavor separation of u and d (anti)quarks in global QCD analyses of the parton distribution functions (PDFs) of the nucleon. We investigate the impact of theoretical corrections accounting for the light-nuclear structure of the deuteron upon the fitted u, d-quark, gluon, and other PDFs in the CJ15 and CT18 families of next-to-leading order CTEQ global analyses. The investigation is done using the $$L_2$$ L 2 sensitivity statistical method, which provides a common metric to quantify the strength of experimental constraints on various PDFs and ratios of PDFs in the two distinct fitting frameworks. Using the $$L_2$$ L 2 sensitivity and other approaches, we examine the compatibility of deuteron data sets with other fitted experiments under varied implementations of the deuteron corrections. We find that freely-fitted deuteron corrections modify the PDF uncertainty at large momentum fractions and will be relevant for future PDFs affecting electroweak precision measurements.


2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Quentin Bonnefoy ◽  
Luca Di Luzio ◽  
Christophe Grojean ◽  
Ayan Paul ◽  
Alejo N. Rossia

Abstract We study axion effective field theories (EFTs), with a focus on axion couplings to massive chiral gauge fields. We investigate the EFT interactions that participate in processes with an axion and two gauge bosons, and we show that, when massive chiral gauge fields are present, such interactions do not entirely originate from the usual anomalous EFT terms. We illustrate this both at the EFT level and by matching to UV-complete theories. In order to assess the consistency of the Peccei-Quinn (PQ) anomaly matching, it is useful to introduce an auxiliary, non-dynamical gauge field associated to the PQ symmetry. When applied to the case of the Standard Model (SM) electroweak sector, our results imply that anomaly-based sum rules between EFT interactions are violated when chiral matter is integrated out, which constitutes a smoking gun of the latter. As an illustration, we study a UV-complete chiral extension of the SM, containing an axion arising from an extended Higgs sector and heavy fermionic matter that obtains most of its mass by coupling to the Higgs doublets. We assess the viability of such a SM extension through electroweak precision tests, bounds on Higgs rates and direct searches for heavy charged matter. At energies below the mass of the new chiral fermions, the model matches onto an EFT where the electroweak gauge symmetry is non-linearly realised.


2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Ankit Beniwal ◽  
Juan Herrero-García ◽  
Nicholas Leerdam ◽  
Martin White ◽  
Anthony G. Williams

Abstract The Scotogenic Model is one of the most minimal models to account for both neutrino masses and dark matter (DM). In this model, neutrino masses are generated at the one-loop level, and in principle, both the lightest fermion singlet and the lightest neutral component of the scalar doublet can be viable DM candidates. However, the correct DM relic abundance can only be obtained in somewhat small regions of the parameter space, as there are strong constraints stemming from lepton flavour violation, neutrino masses, electroweak precision tests and direct detection. For the case of scalar DM, a sufficiently large lepton-number-violating coupling is required, whereas for fermionic DM, coannihilations are typically necessary. In this work, we study how the new scalar singlet modifies the phenomenology of the Scotogenic Model, particularly in the case of scalar DM. We find that the new singlet modifies both the phenomenology of neutrino masses and scalar DM, and opens up a large portion of the parameter space of the original model.


2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Anne Mareike Galda ◽  
Matthias Neubert ◽  
Sophie Renner

Abstract The Standard Model Effective Field Theory (SMEFT) offers a powerful theoretical framework for parameterizing the low-energy effects of heavy new particles with masses far above the scale of electroweak symmetry breaking. Additional light degrees of freedom extend the effective theory. We show that light new particles that are weakly coupled to the SM via non-renormalizable interactions induce non-zero Wilson coefficients in the SMEFT Lagrangian via renormalization-group evolution. For the well-motivated example of axions and axion-like particles (ALPs) interacting with the SM via classically shift-invariant dimension-5 interactions, we calculate how these interactions contribute to the one-loop renormalization of the dimension-6 SMEFT operators, and how this running sources additional contributions to the Wilson coefficients on top of those expected from heavy new states. As an application, we study the ALP contributions to the magnetic dipole moment of the top quark and comment on implications of electroweak precision constraints on ALP couplings.


2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Andrzej J. Buras ◽  
Andreas Crivellin ◽  
Fiona Kirk ◽  
Claudio Andrea Manzari ◽  
Marc Montull

Abstract New neutral heavy gauge bosons (Z′) are predicted within many extensions of the Standard Model. While in case they couple to quarks the LHC bounds are very stringent, leptophilic Z′ bosons (even with sizable couplings) can be much lighter and therefore lead to interesting quantum effects in precision observables (like (g − 2)μ) and generate flavour violating decays of charged leptons. In particular, $$ \mathrm{\ell}\to \mathrm{\ell}^{\prime }v\overline{v} $$ ℓ → ℓ ′ v v ¯ decays, anomalous magnetic moments of charged leptons, ℓ → ℓ′γ and ℓ → 3ℓ′ decays place stringent limits on leptophilic Z′ bosons. Furthermore, in case of mixing Z′ with the SM Z, Z pole observables are affected. In light of these many observables we perform a global fit to leptophilic Z′ models with the main goal of finding the bounds for the Z′ couplings to leptons. To this end we consider a number of scenarios for these couplings. While in generic scenarios correlations are weak, this changes once additional constraints on the couplings are imposed. In particular, if one considers an Lμ− Lτ symmetry broken only by left-handed rotations, or considers the case of τ − μ couplings only. In the latter setup, on can explain the (g − 2)μ anomaly and the hint for lepton flavour universality violation in $$ \tau \to \mu v\overline{v}/\tau \to ev\overline{v} $$ τ → μv v ¯ / τ → ev v ¯ without violating bounds from electroweak precision observables.


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