A
bstract
We present
ν
DoBe, a Python tool for the computation of neutrinoless double beta decay (0
νββ
) rates in terms of lepton-number-violating operators in the Standard Model Effective Field ...Theory (SMEFT). The tool can be used for automated calculations of 0
νββ
rates, electron spectra and angular correlations for all isotopes of experimental interest, for lepton-number-violating operators up to and including dimension 9. The tool takes care of renormalization-group running to lower energies and provides the matching to the low-energy effective field theory and, at lower scales, to a chiral effective field theory description of 0
νββ
rates. The user can specify different sets of nuclear matrix elements from various many-body methods and hadronic low-energy constants. The tool can be used to quickly generate analytical and numerical expressions for 0
νββ
rates and to generate a large variety of plots. In this work, we provide examples of possible use along with a detailed code documentation. The code can be accessed through:
GitHub:
https://github.com/OScholer/nudobe
Online User-Interface:
https://oscholer-nudobe-streamlit-4foz22.streamlit.app/
A
bstract
Recent developments in the Standard Model analysis of semileptonic charged-current processes involving light quarks have revealed ~ 3
σ
tensions in Cabibbo universality tests involving ...meson, neutron, and nuclear beta decays. In this paper, we explore beyond the Standard Model explanations of this so-called Cabibbo Angle Anomaly in the framework of the Standard Model Effective Field Theory (SMEFT), including not only low-energy charged current processes (‘L’), but also electroweak precision observables (‘EW’) and Drell-Yan collider processes (‘C’) that probe the same underlying physics across a broad range of energy scales. The resulting ‘CLEW’ framework not only allows one to test explanations of the Cabibbo Angle Anomaly, but is set up to provide near model-independent analyses with minimal assumptions on the flavor structure of the SMEFT operators. Besides the global analysis, we consider a large number of simpler scenarios, each with a subset of SMEFT operators, and investigate how much they improve upon the Standard Model fit. We find that the most favored scenarios, as judged by the Akaike Information Criterion, are those that involve right-handed charged currents. Additional interactions, namely oblique operators, terms modifying the Fermi constant, and operators involving right-handed neutral currents, play a role if the CDF determination of the
W
mass is included in the analysis.
The interpretation of nuclear electric dipole moment (EDM) experiments is clouded by large theoretical uncertainties associated with nonperturbative matrix elements. In various beyond-the-Standard ...Model scenarios nuclear and diamagnetic atomic EDMs are expected to be dominated by CP-violating pion–nucleon interactions that arise from quark chromo-electric dipole moments. The corresponding CP-violating pion–nucleon coupling strengths are, however, poorly known.
In this work we propose a strategy to calculate these couplings by using spectroscopic lattice QCD techniques. Instead of directly calculating the pion–nucleon coupling constants, a challenging task, we use chiral symmetry relations that link the pion–nucleon couplings to nucleon sigma terms and mass splittings that are significantly easier to calculate. In this work, we show that these relations are reliable up to next-to-next-to-leading order in the chiral expansion in both SU(2) and SU(3) chiral perturbation theory. We conclude with a brief discussion about practical details regarding the required lattice QCD calculations and the phenomenological impact of an improved understanding of CP-violating matrix elements.
A
bstract
Large numbers of
τ
leptons are produced at Belle II. These could potentially decay into sterile neutrinos that, for the mass range under consideration, are typically long-lived, leading to ...displaced-vertex signatures. Here, we study a displaced-vertex search in the context of the sterile-neutrino-extended Standard Model Effective Field Theory. The production and decay of the sterile neutrinos can be realized via either the standard active-sterile neutrino mixing or higher-dimensional operators in the effective Lagrangian. We perform Monte-Carlo simulations to estimate the Belle II sensitivities to such interactions. We find that Belle II can probe non-renormalizable dimension-six operators involving a single sterile neutrino up to a few TeV in the new-physics scale.
We utilize the gradient flow to define and calculate electric dipole moments induced by the strong QCD
θ
-term and the dimension-6 Weinberg operator. The gradient flow is a promising tool to simplify ...the renormalization pattern of local operators. The results of the nucleon electric dipole moments are calculated on PACS-CS gauge fields (available from the ILDG) using
N
f
= 2+1, of discrete size 32
3
×64 and spacing
a
≃ 0.09 fm. These gauge fields use a renormalization-group improved gauge action and a nonperturbatively
O
(
a
) improved clover quark action at
β
= 1.90, with
c
SW
= 1.715. The calculation is performed at pion masses of
m
π
≃ 411, 701 MeV.
A
bstract
We investigate neutrinoless double beta (0
νββ
) decay rates in minimal left-right symmetric models in presence of relatively light right-handed neutrinos. By use of an effective field ...theory approach, we systematically include all contributions in the model as well as the dependence of the decay amplitude on the masses of right-handed neutrinos. In type-I and type-II seesaw scenarios, we analyze the impact of right-handed neutrinos heavier than about 10 MeV, showing that this effect can lead to a detection of 0
νββ
decay in the next-generation experiments even for the normal hierarchy and a relatively large right-handed scale set by the mass of hypothetical right-handed gauge bosons. Finally, we comment on a possible connection between light right-handed neutrinos and the strong CP problem.
In the standard model, the renormalization of the QCD vacuum angle θ is extremely tiny, and small θ is technically natural. In the general standard model effective field theory (SMEFT), however, Δθ ...is quadratically divergent, reflecting the fact that new sources of hadronic CP-violation typically produce Oð1Þ threshold corrections to θ. The observation of such CP-violating interactions would therefore be in tension with solutions to the strong CP problem in which θ ¼ 0 is an ultraviolet boundary condition, pointing to the Peccei-Quinn mechanism as the explanation for why θ is small in the infrared. We study the quadratic divergences in θ arising from dimension-6 SMEFT operators and discuss the discovery prospects for these operators at electric dipole moment experiments, the LHC, and future proton-proton colliders.
A
bstract
At the Deep Underground Neutrino Experiment (DUNE), a proton beam hits a fixed target leading to large production rates of mesons. These mesons can decay and potentially provide a source of ...long-lived neutral fermions. Examples of such long-lived fermions are heavy neutral leptons which can mix with the standard-model active neutrinos, and the bino-like lightest neutralino in R-parity-violating supersymmetry. We show that the Standard Model Effective Field Theory extended with right-handed singlet neutrinos can simultaneously describe heavy neutral leptons and bino-like neutralinos in a unified manner. We use the effective-field-theory framework to determine the sensitivity reach of the DUNE near detector in probing various scenarios of long-lived neutral fermions.
CP-violating interactions at quark level generate CP-violating nuclear interactions and currents, which could be revealed by looking at the presence of a permanent nuclear electric dipole moment. ...Within the framework of chiral effective field theory, we discuss the derivation of the CP-violating nuclear potential up to next-to-next-to leading order (N
2
LO) and the preliminary results for the charge operator up to next-to leading order (NLO). Moreover, we introduce some renormalization argument which indicates that we need to promote the short-distance operator to the leading order (LO) in order to reabsorb the divergences generated by the one pion exchange. Finally, we present some selected numerical results for the electric dipole moments of
2
H,
3
He and
3
H discussing the systematic errors introduced by the truncation of the chiral expansion.
The isovector time-reversal- and parity-violating pion–nucleon coupling g¯π(1) is uniquely sensitive to dimension-six interactions between right-handed light quarks and the Standard Model Higgs ...doublet that naturally arises in left-right symmetric models. Recent work has used the g¯π(1)-induced one-loop contribution to the neutron electric dipole moment dn, together with the present experimental dn bound, to constrain the CP-violating parameters of the left-right symmetric model. We show that this and related analyses are based on an earlier meson theory dn computation that is not consistent with the power-counting appropriate for an effective field theory. We repeat the one-loop calculation using heavy baryon chiral perturbation theory and find that the resulting dn sensitivity to g¯π(1) is suppressed, implying more relaxed constraints on the parameter space of the left-right symmetric model. Assuming no cancellations between this loop contribution and other contributions, such as the leading order EDM low-energy constant, the present limit on dn implies |g¯π(1)|≲1.1×10−10.
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