Anomalous Magnetic Moment Of Electron Research Articles

Fermion mass hierarchy in an extended left-right symmetric model

We present a Left-Right symmetric model that provides an explanation for the mass hierarchy of the charged fermions within the framework of the Standard Model. This explanation is achieved through the utilization of both tree-level and radiative seesaw mechanisms. In this model, the tiny masses of the light active neutrinos are generated via a three-loop radiative inverse seesaw mechanism, with Dirac and Majorana submatrices arising at one-loop level. To the best of our knowledge, this is the first example of the inverse seesaw mechanism being implemented with both submatrices generated at one- loop level. The model contains a global U(1)X symmetry which, after its spontaneous breaking, allows for the stabilization of the Dark Matter (DM) candidates. We show that the electroweak precision observables, the electron and muon anomalous magnetic moments as well as the Charged Lepton Flavor Violating decays, μ → eγ, are consistent with the current experimental limits. In addition, we analyze the implications of the model for the 95 GeV diphoton excess recently reported by the CMS collaboration and demonstrate that such anomaly could be easily accommodated. Finally, we discuss qualitative aspects of DM in the considered model.

Dark matter and [formula omitted] in ISS(2,3) based Gauged [formula omitted] symmetric model

We proposed a model which can explain the neutrino phenomenology, dark matter and anomalous magnetic moment (g−2) in a common framework. The inverted seasaw (ISS)(2,3) mechanism has been incorporated, in which we get an extra sterile state and this state act as a viable dark matter candidate. The right handed neutrino mass is obtained in TeV scale, which is accessible at LHC. The anomaly free U(1)Le−Lμ gauge symmetry is introduced to explain the anomalous magnetic moment of electron and muon because it provides a natural origin of (g−2) in a very minimal setup. The corresponding MeV scale gauge boson successfully explain the anomalous magnetic moment of electron and muon (g−2)e,μ, simultaneously. Thus obtained neutrino phenomenology and relic abundance of dark matter are compatible with experimental results.

Lifetime of the 4s24pP3/22 metastable level in galliumlike Mo11+

The lifetime of the galliumlike ${\mathrm{Mo}}^{11+}$ ion $4{s}^{2}4p\phantom{\rule{0.16em}{0ex}}^{2}P_{3/2}$ metastable level was measured at an electron-beam ion trap. The lifetime was inferred from the temporal behavior of its associated $4{s}^{2}4p\phantom{\rule{0.16em}{0ex}}^{2}P_{3/2}\ensuremath{-}^{2}P_{1/2}$ transition. Particular effort was devoted to reducing the systematic errors and the obtained lifetime value was $4.813(9){(}_{\ensuremath{-}5}^{+2})$ (stat)(syst) ms. Most of the predictions without the electron anomalous magnetic moment correction are consistent with our measurement results. However, all the available, theoretical, effect-corrected results show an unexpected discrepancy with the measured results.

Muon g−2 anomaly in a left-right model with an inverse seesaw mechanism

We investigate the possibility of explanation for the muon anomalous magnetic moment ${g}_{\ensuremath{\mu}}\ensuremath{-}2$ in a left-right model with an inverse seesaw mechanism. We emphasize that the observed deviation from the Standard Model predictions can be accommodated in a large part of the parameter space of this class of models, where loops with massive neutrinos and charged Higgs boson as well as the weak $W$ boson contribute significantly to ${g}_{\ensuremath{\mu}}\ensuremath{-}2$. Stringent constraints due to lepton flavor violation $\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}$, $\ensuremath{\mu}\text{\ensuremath{-}}e$ conversion and the electron anomalous magnetic moment ${g}_{e}\ensuremath{-}2$ are considered, and the results are compatible.

Heavy singly charged Higgs bosons and inverse seesaw neutrinos as origins of large (g−2)e,μ in two Higgs doublet models

We show that simple extensions of two Higgs doublet models consisting of new heavy neutrinos and a singly charged Higgs boson singlet can successfully explain the experimental data on muon and electron anomalous magnetic moments thanks to large chirally-enhanced one-loop level contributions. These contributions arise from the large couplings of inverse seesaw neutrinos with singly charged Higgs bosons and right-handed charged leptons. The regions of parameter space satisfying the experimental data on (g−2)e,μ anomalies allow heavy singly charged Higgs boson masses above the TeV scale, provided that heavy neutrino masses are above few hundred GeV, the non-unitary part of the active neutrino mixing matrix must be large enough, two singly charged Higgs bosons are non degenerate, and the mixing between singly charged Higgs bosons must be non-zero.

Dark Matter and (g - 2) μ,e in radiative Dirac neutrino mass models

The origin of neutrino mass is a mystery, so is its nature, namely, whether neutrinos are Dirac or Majorana particles. On top of that, hints of large deviations of the muon and the electron anomalous magnetic moments (AMMs) are strong evidence for physics beyond the Standard Model. In this work, piecing these puzzles together, we propose a class of radiative Dirac neutrino mass models to reconcile (g - 2) μ,e anomalies with neutrino oscillation data. In this framework, a common set of new physics (NP) states run through the loops that generate non-zero neutrino mass and, due to chiral enhancement, provide substantial NP contributions to lepton AMMs. In addition, one of the three models studied in this work offers a Dark Matter candidate automatically stabilized by the residual symmetry, whose phenomenology is non-trivially connected to the other two puzzles mentioned above. Finally, our detailed numerical analysis reveals a successful resolution to these mysteries while being consistent with all colliders and cosmological constraints.

Isodoublet vector leptoquark solution to the muon g−2 , RK,K* , RD,D* , and W -mass anomalies

We investigate the isodoublet vector leptoquark ${V}_{2}$ as a solution to the $B$ anomalies ${R}_{K,{K}^{*}}$ and ${R}_{D,{D}^{*}}$, as well as explaining the muon and electron anomalous magnetic moments and the very recent $W$-mass anomaly.

Probing an intrinsically flavorful ALP via tau-lepton flavor physics

Any axionlike particle (ALP) intrinsically possesses flavorful couplings to the standard model (SM) fermions arising as a consequence of the right-handed flavor rotation within the SM. In this paper we discuss this intrinsically flavored ALP, and explore the correlation of a minimal set of the couplings in a view of coherence in flavor physics observables. We focus particularly on the tau-lepton flavor violation (LFV). The ALP is assumed to be tau-philic on a current-eigenstate basis, a la Pecci-Quinn. The ALP has the intrinsic flavorful coupling structure for fermions, which allows coupling also to muon and electron only in a right-handed specific manner. Several LFV processes are generated including radiative tau decays and also anomalous magnetic moments of electron and muon. We first pay attention to two separated limits: electron scenario with the ALP coupled to tau which mixes only with right-handed electron, and muon scenario as the muonic counterpart of the electron scenario. It turns out that those scenarios are highly constrained by experimental limits, to require a mu or electron - tau flipped feature in the mass eigenbasis when coupled to the ALP. We then examine a hybrid scenario, and find a fully viable parameter space on the ALP mass-photon coupling plane, which limits the ALP mass to be (1.7 - 10) GeV and the ALP decay constant $f_a$ to be (12.8 - 67.9) GeV. We find that the same-sign multilepton signal at Belle II is a smoking-gun to probe the present ALP signal, and the polarization asymmetry in LFV radiative $\tau$ decay is a punchline, which definitely predicts preference of the right-handed polarization, in sharp contrast to the SM plus massive Dirac neutrinos having the highly left-handed preference, and also other light-new physics candidates. Possible model-building to underlie the present third-generation specific ALP is also briefly addressed.

Helicity Transfer in Strong Laser Fields via the Electron Anomalous Magnetic Moment.

Electron beam longitudinal polarization during the interaction with counterpropagating circularly polarized ultraintense laser pulses is investigated, while accounting for the anomalous magnetic moment of the electron. Although it is known that the helicity transfer from the laser photons to the electron beam is suppressed in linear and nonlinear Compton scattering processes, we show that the helicity transfer nevertheless can happen via an intermediate step of the electron radiative transverse polarization, phase matched with the driving field, followed up by spin rotation into the longitudinal direction as induced by the anomalous magnetic moment of the electron. With spin-resolved QED MonteCarlo simulations, we demonstrate the consequent helicity transfer from laser photons to the electron beam with a degree up to 10%, along with an electron radial polarization up to 65% after multiple photon emissions in a femtosecond timescale. This effect is detectable with currently achievable laser facilities, evidencing the role of the leading QED vertex correction to the electron anomalous magnetic moment in the polarization dynamics in ultrastrong laser fields.

Neutrino masses and magnetic moments of electron and muon in the Zee Model

We explore parameter space in the Zee Model to resolve the long-standing tension of the electron and muon anomalous magnetic moment (AMM). The model comprises a second Higgs doublet and a charged singlet at electroweak scale and generates Majorana neutrino masses at one-loop level; the neutral partner of the SU(2)L doublet contributes to the AMM of electron and muon via one loop and two-loop corrections. We propose two minimal flavor structures that can explain these anomalies while fitting the neutrino oscillation data. We find that the neutral Higgs resides in the mass range of roughly 10–300 GeV or 1–30 GeV, depending on the flavor structures. The model is consistent with constraints from colliders, electroweak precision data, and lepton flavor violation. To be comprehensive, we examine the constraints from the electric dipole moment (EDM) and find a region of parameter space that gives a sizable contribution to muon EDM while simultaneously giving corrections to muon AMM. In addition to the light scalar, the two charged scalars with masses as low as 100 GeV can induce nonstandard neutrino interactions εee as large as 8%, potentially hinting at new physics. We also investigate the projected capability of future lepton colliders to probe the currently allowed parameter space consistent with both electron and muon AMMs via direct searches in the ℓ+ℓ− → ℓ+ℓ−(H → ℓ+ℓ−) channel.

A renormalizable left-right symmetric model with low scale seesaw mechanisms

We propose a low scale renormalizable left-right symmetric theory that successfully explains the observed SM fermion mass hierarchy, the tiny values for the light active neutrino masses and is consistent with the lepton and baryon asymmetries of the Universe, the muon and electron anomalous magnetic moments as well as with the constraints arising from the meson oscillations. In the proposed model the top and exotic quarks obtain masses at tree level, whereas the masses of the bottom, charm and strange quarks, tau and muon leptons are generated from a tree level Universal Seesaw mechanism, thanks to their mixings with the charged exotic vector like fermions. The masses for the first generation SM charged fermions arise from a radiative seesaw mechanism at one loop level, mediated by charged vector like fermions and electrically neutral scalars. The light active neutrino masses are produced from a one-loop level inverse seesaw mechanism mediated by electrically neutral scalar singlets and right handed Majorana neutrinos. Our model is also consistent with the experimental constraints arising from the Higgs diphoton decay rate as well as with the constraints arising from charged lepton flavor violation. We also discuss the Z′ and heavy scalar production at a proton-proton collider.

Universal inverse seesaw mechanism as a source of the SM fermion mass hierarchy

We build a renormalizable theory where the inverse seesaw mechanism explains the pattern of SM fermion masses. To the best of our knowledge, our model corresponds to the first implementation of the inverse seesaw mechanism for the charged fermion sector. In our theory, the inverse seesaw mechanism is implemented at the tree and one-loop levels in order to generate the masses for the second and first families of the SM charged fermions, respectively. The third family of SM charged fermions obtain tree-level masses from the Higgs doublets phi _{1} (for the top quark) and phi _{2} (for the bottom quark and tau lepton). The masses of the active light neutrinos are generated from a two-loop level inverse seesaw mechanism. Our model successfully explains the observed SM fermion mass hierarchy, the tiny masses of the active light neutrinos, contains the necessary means for efficient leptogenesis and is in accordance with the constraints resulting from meson oscillations, as well as with the measured values of the observed dark matter relic density and of the muon and electron anomalous magnetic moments.

Type-X two-Higgs-doublet model in light of the muon g−2 : Confronting Higgs boson and collider data

The recent Fermilab measurement of the muon anomalous magnetic moment yields $4.2 \sigma$ deviations from the SM prediction when combined with the BNL E821 experiment results. In the Type-X two Higgs doublet model, we study the consequence of imposing the observed muon $g-2$, along with the constraints from theoretical stabilities, electroweak oblique parameters, Higgs precision data, and direct searches. For a comprehensive study, we scan the whole parameter space in two scenarios, the normal scenario where $h_{\rm SM} = h$ and the inverted scenario where $h_{\rm SM}=H$, where $h$ ($H$) is the light (heavy) CP-even Higgs boson. We found that large $\tan\beta$ (above 100) and light pseudoscalar mass $M_A$ are required to explain the muon $g-2$ anomaly. This breaks the theoretical stability unless the scalar masses satisfy $M_A^2 \simeq M_{H^\pm}^2 \simeq m_{12}^2 \tan\beta \approx M_{H/h}^2$. The direct search bounds at the LEP and LHC exclude the light $A$ window with $M_A \lesssim 62.5~$GeV. We also show that the observed electron anomalous magnetic moment is consistent with the model prediction, but the lepton flavor universality data in the $\tau$ and $Z$ decays are not. For a separate exploration of the model, we propose the golden mode $pp \to A h/AH \to 4 \tau$ at the HL-LHC.

Electron mass shift in an intense plane wave

Upcoming experiments on the interaction of electrons with intense laser fields are envisaged to become more and more accurate, which calls for theoretical computations of rates and probabilities with correspondingly higher precision. In strong-field QED this requires the knowledge of radiative corrections to be added to leading-order results. Here, we first derive the mass operator in momentum space of an off-shell electron in the presence of an arbitrary plane wave. By taking the average of the mass operator in momentum space over an on-shell electron state, we obtain a new representation, equivalent to but more compact than the known one computed in [Sov. Phys. JETP \textbf{42}, 400 (1975)]. Moreover, we use the obtained mass operator to determine the electron mass shift in an arbitrary plane wave, which generalizes the already known expression in a constant crossed field. The spin-dependent part of the electron mass shift can be related to the anomalous magnetic moment of the electron in the plane wave. We show that within the locally constant field approximation it is possible to conveniently define a local expression of the electron anomalous magnetic moment, which reduces to the known expression in a constant crossed field. Beyond the locally constant field approximation, however, the interaction between the electron and the plane wave is non-local such that it is not possible to conveniently introduce an electron anomalous magnetic moment.

Fermion mass hierarchy and g \u2212 2 anomalies in an extended 3HDM Model

We propose an extension of the three-Higgs-doublet model (3HDM), where the Standard Model (SM) particle content is enlarged by the inclusion of two inert SU2L scalar doublets, three inert and two active electrically neutral gauge singlet scalars, charged vector like fermions and Majorana neutrinos. These additional particles are introduced to generate the SM fermion mass hierarchy from a sequential loop suppression mechanism. In our model the top and exotic fermion masses appear at tree level, whereas the remaining fermions get their masses radiatively. Specifically, bottom, charm, tau and muon masses appear at 1-loop; the masses for the light up, down and strange quarks as well as for the electron at 2-loop and masses for the light active neutrinos at 3-loop. Our model successfully accounts for SM fermion masses and mixings and accommodates the observed Dark Matter relic density, the electron and muon anomalous magnetic moments, as well the constraints arising from charged Lepton Flavor Violating (LFV) processes. The proposed model predicts charged LFV decays within the reach of forthcoming experiments.

Electron and muon magnetic moments and implications for dark matter and model characterisation in non-universal U(1)\u2032 supersymmetric models

We attribute deviations of the muon and electron magnetic moments from the theoretical predictions to the presence of an additional U(1)′ supersymmetric model. We interpret the discrepancies between the muon and electron anomalous magnetic moments to be due to the presence of non-universal U(1)′ charges. In a minimally extended model, we show that requiring both deviations to be satisfied imposes constraints on the spectrum of the model, in particular on dark matter candidates and slepton masses and ordering. Choosing three benchmarks with distinct dark matter features, we study implications of the model at colliders, concentrating on variables that can distinguish our non-universal scenario from other U(1)′ implementations.

Axionlike particles resolve the B→πK and g−2 anomalies

We offer a new solution to an old puzzle in the penguin-dominated $B\ensuremath{\rightarrow}\ensuremath{\pi}K$ decays. The puzzle is the inconsistency among the measurements of the branching ratios and $CP$ asymmetries of the four $B\ensuremath{\rightarrow}\ensuremath{\pi}K$ decays: ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}^{0}$, ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{K}^{+}$, ${B}_{d}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{K}^{+}$, ${B}_{d}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{K}^{0}$. We solve the $B\ensuremath{\rightarrow}\ensuremath{\pi}K$ puzzle by considering the effect of an axionlike particle (ALP) that mixes with the ${\ensuremath{\pi}}^{0}$ and has mass close to the ${\ensuremath{\pi}}^{0}$ mass. We show that the ALP can also explain the anomalies in the electron and muon anomalous magnetic moments.

Muon and electron g−2 and proton and cesium weak charges implications on dark Zd models

Theories beyond the standard model involving a sub-GeV-scale vector ${Z}_{d}$ mediator have been largely studied as a possible explanation of the experimental values of the muon and electron anomalous magnetic moments. Motivated by the recent determination of the anomalous muon magnetic moment performed at Fermilab, we derive the constraints on such a model obtained from the magnetic moment determinations and the measurements of the proton and cesium weak charge, ${Q}_{W}$, performed at low-energy transfer. In order to do so, we revisit the determination of the cesium ${Q}_{W}$ from the atomic parity violation experiment, which depends critically on the value of the average neutron rms radius of $^{133}\mathrm{Cs}$, by determining the latter from a practically model-independent extrapolation from the recent average neutron rms radius of $^{208}\mathrm{Pb}$ performed by the PREX-2 Collaboration. From a combined fit of all the aforementioned experimental results, we obtain rather precise limits on the mass and the kinetic mixing parameter of the ${Z}_{d}$ boson, namely ${m}_{{Z}_{d}}={47}_{\ensuremath{-}16}^{+61}\text{ }\text{ }\mathrm{MeV}$ and $ϵ={2.3}_{\ensuremath{-}0.4}^{+1.1}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, when marginalizing over the $Z\ensuremath{-}{Z}_{d}$ mass mixing parameter $\ensuremath{\delta}$.

Probing Lμ−Lτ models with CEνNS : A new look at the combined COHERENT CsI and Ar data

The minimal gauged $U(1)_{L_\mu-L_\tau}$ model has long been known to be able to explain the tension between the theoretical and experimental values of the muon magnetic moment. It has been explored and tested extensively, pushing the viable parameter space into a very tight corner. Further, embedding the $U(1)_{L_\mu-L_\tau}$ model in a supersymmetric (SUSY) framework has been shown to relax some of these constraints and has recently been shown to explain the electron anomalous magnetic moment as well. In this model, the logarithm of the mass ratio of third to second generation (s)leptons control the non-negligible kinetic mixing and may crucially alter many of the constraints. We confront both the non-SUSY and SUSY versions of this class of models with the CsI(2017), the recently released CENNS10 data from the liquid Argon detector as well as the updated CsI(2020) data of the COHERENT experiment. We use the recoil energy and timing binned data from CsI(2017) and the energy, time, and Pulse Shape Discriminator binned data from CENNS10 to find estimates for the model parameters in a likelihood maximization test. We also show updated exclusions using all of the above data from the COHERENT Collaboration, as well as projected exclusions from the ongoing Coherent CAPTAIN-Mills experiment. The $(g-2)_\mu$ favored values of the $U(1)_{L_\mu-L_\tau}$ gauge coupling that are still unconstrained overlap with the estimates from COHERENT data within $1\sigma$. The combined COHERENT data is found to prefer the presence of the $U(1)_{L_\mu-L_\tau}$ gauge boson over the Standard Model at $\sim1.4\sigma$. The global minima of a chi-square deviation function using CsI(2020) as well as CENNS10 total counts has significant overlap with the $(g-2)_{\mu}$ favored parameter space in the context of the SUSY and non-SUSY $L_{\mu}-L_{\tau}$ models with a mediator mass in the $20-100$ MeV range.

Fermion mass hierarchies from vectorlike families with an extended 2HDM and a possible explanation for the electron and muon anomalous magnetic moments

We study an extended 2 Higgs doublet model (2HDM) in which the Standard Model (SM) Yukawa interactions are forbidden due to a global $U(1{)}^{\ensuremath{'}}$ symmetry, but may arise via mixing with vectorlike families. In this model, the hierarchical structure of Yukawa couplings of quarks and leptons in the SM arises from the heavy masses of the fourth and fifth vectorlike families. Within this model, we consider various nonstandard contributions to the electron and muon anomalous magnetic moments. We first consider the $W$ exchange at one-loop level, consistent with the $\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}$ constraint, and show that it yields a negligible contribution to both electron and muon anomalous magnetic moments. We then consider Higgs scalar exchange, together with vectorlike leptons, at one-loop level and show that it is possible to have nonstandard contributions to the electron and muon anomalous magnetic moments within the $1\ensuremath{\sigma}$ constraint of certain experiments. We present some benchmark points for both the muon and the electron anomalies, together with some numerical scans around these points, which indicate the mass regions of the Higgs scalars of the 2HDM in this scenario.