Using the new results on coherent elastic neutrino-nucleus scattering data in cesium-iodide provided by the COHERENT experiment, we determine a new measurement of the average neutron rms radius of $^{133}\text{Cs}$ and $^{127}\text{I}$. In combination with the atomic parity violation (APV) experimental result, we derive the most precise measurement of the neutron rms radii of $^{133}\text{Cs}$ and $^{127}\text{I}$, disentangling for the first time the contributions of the two nuclei. By exploiting these measurements we determine the corresponding neutron skin values for $^{133}\text{Cs}$ and $^{127}\text{I}$. These results suggest a preference for models which predict large neutron skin values, as corroborated by the only other electroweak measurements of the neutron skin of $^{208}\text{Pb}$ performed by PREX experiments. Moreover, for the first time, we obtain a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of $^{133}\text{Cs}$ and $^{127}\text{I}$, that is allowed to vary freely in the fit. The value of the low-energy weak mixing angle that we found is slightly larger than the standard model prediction.
I review the description of the electroweak nuclear response at large momentum transfer within nonrelativistic many-body theory. Special consideration is given to the effects of final state interactions, which are known to be large in both inclusive and semi-inclusive processes. The results of theoretical calculations of electron-nucleus scattering observables are compared to the data, and the generalization to charged current neutrino-nucleus interactions is discussed.
Quasielastic electromagnetic and parity-violating electron scattering response functions of relativistic nuclear matter are reviewed. The roles played by the Hartree-Fock field and by nuclear correlations in the Random Phase Approximation (treated within the continued fraction scheme) are illustrated. The parity-violating responses of nuclei to polarized electrons are also revisited, stressing in particular the crucial role played by the pion in the nuclear dynamics. Finally, some issues surrounding scaling and sum rules are addressed.
The Quasi-Elastic (QE) contribution of the nuclear inclusive electron model developed in reference \cite{GNO97} is extended to the study of electroweak Charged Current (CC) induced nuclear reactions at intermediate energies of interest for future neutrino oscillation experiments. Long range nuclear (RPA) correlations, Final State Interaction (FSI) and Coulomb corrections are included within the model. RPA correlations are shown to play a crucial role in the whole range of neutrino energies, up to 500 MeV, studied in this work. Predictions for inclusive muon capture for different nuclei through…
We consider feasibility of electroweak baryogenesis in gauge mediated supersymmetry breaking models with messenger-matter mixing. We present a class of models where electroweak baryogenesis produces sufficient amount of baryon asymmetry. The main features of these models are ({\it i}) large mixing between messengers and right stop and ({\it ii}) fairly narrow region of viable $\tanβ$.
We present the results for the full electroweak two-loop bosonic contributions to the effective leptonic mixing angle of the $Z$ boson, $\sin^2θ_{\rm eff}$, in the Standard Model. A method applied to extract collinear divergences from two-loop vertex-functions is described. Comparisons of our results with those from a recent previous calculation show complete agreement.
The availability of the double-differential charged-current neutrino cross section, measured by the MiniBooNE collaboration using a carbon target, allows for a systematic comparison of nuclear effects in quasi-elastic electron and neutrino scattering. The results of our study, based on the impulse approximation scheme and a state-of-the-art model of the nuclear spectral functions, suggest that the electron cross section and the flux averaged neutrino cross sections, corresponding to the same target and comparable kinematical conditions, cannot be described within the same theoretical approach …
High-precision calculations of electroweak processes in light nuclei are of great importance for multiple reasons. Gerry Brown together with Dan-Olof Riska published in 1972 a famous calculation on radiative capture of a thermal neutron on a proton, and their work was a precursor of subsequent great developments in high-precision calculations of electroweak processes in light nuclei. The application of effective field theory to nuclear systems is a prominent example of these developments. We present an overview of it with main emphasis placed on those topics in which we ourselves have been inv…
Kaon electroweak properties in symmetric nuclear matter are studied in the Nambu--Jona-Lasinio model using the proper-time regularization. The valence quark properties in symmetric nuclear matter are calculated in the quark-meson coupling model, and they are used as inputs for studying the in-medium kaon properties in the NJL model. We evaluate the kaon decay constant, kaon-quark coupling constant, and $K^+$ electromagnetic form factor by two different approaches. Namely, by two different ways of calculating the in-medium constituent quark masses of the light quarks. We predict that, in both a…
Over the last decade, numerical solutions of Quantum Chromodynamics (QCD) using the technique of lattice QCD have developed to a point where they are beginning to connect fundamental aspects of nuclear physics to the underlying degrees of freedom of the Standard Model. In this review, the progress of lattice QCD studies of nuclear matrix elements of electroweak currents and beyond-Standard-Model operators is summarized, and connections with effective field theories and nuclear models are outlined. Lattice QCD calculations of nuclear matrix elements can provide guidance for low-energy nuclear r…
The result for the Higgs-dependent electroweak two-loop bosonic contributions to the effective leptonic mixing angle of the $Z$-boson in the Standard Model is presented. Together with the previously calculated fermionic contributions it yields the complete dependence of $\sin^2θ_{\rm eff}$ on the Higgs-boson mass $M_H$. Compared to the fermionic contributions, the bosonic contributions are found to be smaller and have the opposite sign, compensating part of the fermionic contributions.
We present the results from a calculation of the full electroweak two-loop fermionic contributions to the effective leptonic mixing angle of the $Z$ boson, $\sin^2θ_{eff}$, in the Standard Model. On-shell renormalization and analytic calculations are performed for the three-point vertex functions at zero external momenta, whereas irreducible three-point integrals for non-vanishing external momenta are evaluated semi-analytically applying two different methods. Comparisons with a previous calculation show complete agreement.
The effects of flavor mixing in electroweak baryogenesis is investigated in a generalized semiclassical WKB approach. Through calculating the nonadiabatic corrections to the particle currents it is shown that extra CP violation sources arise from the off-diagonal part of the equation of motion of particles moving inside the bubble wall. The numerical importance of the mixing-induced source is discussed in the Minimal Supersymmetric Standard Model and compared with the source term induced by semiclassical force.
We show that, unlike mass matrices, the fermionic gauge currents of the Standard Model exhibit, at the quantum level, remarkable SU(2)_f flavor properties at the observed values of the mixing angles. They accommodate all measured mixing for three families of quarks, and, for neutrinos, maximal theta_{23}, quark-lepton complementarity tan(2 theta_c)=1/2 <--> \tan (2 theta_{12})=2, and a not so small sin^2(2 theta_{13}) = .267 within the present 90% c.l. interval of the T2K experiment.
We enumerate various effective couplings that contribute to the mixings between an exotic vector boson $Z^{\prime}$ and the neutral electroweak vector bosons. The miscellaneous mixing patterns can be evaluated perturbatively. The effective oblique parameters $S^{\prime}$, $T^{\prime}$, and $U^{\prime}$ are calculated to compare with the electroweak precision test results. With the contributions to the non-negligible $U^{\prime}$ parameter from the $ε_{B,W}$ parameters and the aid of some other parameters to cancel the negative $T^{\prime}$, the recent CDF $W$-mass anomaly can therefore be expl…
It is found that in presence of electroweak interactions the gauge covariant diagonalization of the axial-vector -- pseudoscalar mixing in the effective meson Lagrangian leads to a deviation from the vector meson and the axial-vector meson dominance of the entire hadronic electroweak current. The essential features of such a modification of the theory are investigated in the framework of the extended Nambu-Jona-Lasinio model with explicit breaking of chiral $U(2) \times U(2)$ symmetry. The Schwinger-DeWitt method is used as a major tool in our study of the real part of the relevant effective a…
Taking into account the mixing effects between left- and right-handed top-squarks, we calculate the genuine supersymmetric eletroweak correction to top quark production at the Tevatron in the minimal supersymmetric model. The analytic expressions of the corrections to both the parton level cross section and the total hadronic cross section are presented. Some numerical examples are also given to show the size of the corrections.
The effects of flavor mixing in electroweak baryogenesis is investigated in a generalized semiclassical WKB approach. Through calculating the nonadiabatic corrections to the particle currents it is shown that extra CP violation sources arise from the off-diagonal part of the equation of motion of particles moving inside the bubble wall. This type of mixing-induced source is of the first order in derivative expansion of the Higgs condensate, but is oscillation suppressed. The numerical importance of the mixing-induced source is discussed in the Minimal Supersymmetric Standard Model and compared…
We give some details of the recently completed calculation of the full two-loop fermionic corrections to the effective leptonic weak mixing angle. Among others, we describe the C++ library DiaGen/IdSolver, which was used to reduce the two-loop light fermion vertex diagrams to linear combinations of master integrals with rational function coefficients.
We present a global $χ^2$ analysis of electroweak data, including fermion masses and mixing angles, in SO(10) SUSY GUTs. Just as precision electroweak data is used to test the Standard Model, the well determined Standard Model parameters are the precision electroweak data for testing theories beyond the Standard Model. In this talk we use the latest experimentally measured values for these parameters. We study several models discussed in the literature. One of these models provides an excellent fit to the low energy data with $χ^2 \sim 1$ for 3 degrees of freedom. We present our predictions fo…
We compute analytically the complete electroweak two-loop corrections to the $B^0-{\bar B}^0$ mixing. These corrections fix the normalization of the electroweak coupling employed in the extraction of $|V_{td}|$ and reduce the theoretical uncertainty due to higher order electroweak effects from several percent to a few parts in a thousand. If the LO result is expressed in terms of $G_μ$ or of the $\bar{MS}$ coupling $\hat{g}(M_Z)$, the two-loop corrections are $O(1%)$, the exact value depending on the mass of the Higgs boson. We discuss in detail the renormalization procedure and the scheme and…
We construct a phenomenological model of electroweak-scale inflation that is in accordance with recent cosmic microwave background observations by WMAP, while setting the stage for a zero-temperature electroweak transition as assumed in recent models of baryogenesis. We find that the scalar spectral index especially poses tight constraints for low-scale inflation models. The inflaton-Higgs coupling leads to substantial mixing of the scalar degrees of freedom. Two types of scalar particles emerge with decay widths similar to that of the Standard Model Higgs particle.
Recently exact results for the complete electroweak two-loop contributions to the effective weak mixing angle were published. This paper illustrates the techniques used for this computation, in particular the methods for evaluating the loop diagrams and the proper definition of Z-pole observables at next-to-next-to-leading order. Numerical results are presented in terms of simple parametrization formulae and compared in detail with a previous result of an expansion up to next-to-leading order in the top-quark mass. Finally, an estimate of the remaining theoretical uncertainties from unknown hi…
We lay out a novel formalism to connect the isospin-symmetry breaking correction to the rates of superallowed nuclear beta decays, $δ_\text{C}$, to the isospin-breaking sensitive combinations of electroweak nuclear radii that can be accessed experimentally. We individuate transitions in the superallowed decay chart where a measurement of the neutron skin of a stable daughter even at a moderate precision could already help discriminating between models used to compute $δ_\text{C}$. We review the existing experimental situation and make connection to the existing and future experimental programs…
Using a purely hadronic model, we study the charge-symmetry-breaking $ρ$-$ω$, $σ$-$δ$, $σ$-$ρ$ and $δ$-$ω$ mixing amplitudes in isospin asymmetric nuclear matter. The basic assumption of the model is that the mixing amplitude is generated by nucleon and anti-nucleon loops and hence driven entirely by the difference between proton and neutron Fermi momenta and the proton-neutron mass difference. We find that the behavior of the mixing amplitude is very complicated in the spacelike region and quite sensitive to the proton fraction of nuclear medium and nuclear density. In particular, in neutron …
We demonstrate that in the process of deducing the constraint on the electroweak mixing angle $θ_{W}$ in our paper, we have indeed been working with three mass scales while implementing (331) model.
We estimate exclusive density and asymmetry parameter dependent dispersion relations of various charged states of pions in asymmetric nuclear matter. The possibility of matter induced mixing of $π^0$ with $η$ is clearly exposed with the further mass modification of $π^0$ meson due to mixing. Asymmetry driven mass splitting and mixing amplitude are of the same order as the corresponding values in vacuum. Closed form analytic results for the mass shifts and dispersion relations with and without mixing are presented. Furthermore, we discuss the sensitivity of our results on the scalar mean field …
A new general parameterization with eight mixing parameters among Z, gamma and an extra neutral gauge boson Z' is proposed and subjected to phenomenological analysis. We show that in addition to the conventional Weinberg angle theta_W, there are seven other phenomenological parameters G', xi, eta, theta_l, theta_r, r, l for the most general Z-gamma-Z' mixings, in which parameter G' arises due to the presence of an extra Stueckelberg-type mass coupling. Combined with the conventional Z-Z' mass mixing angle theta', the remaining six parameters xi, eta, theta_l-theta', theta_r-theta', r, l are ca…
In this proceeding I briefly review current status of the construction of nuclear electro-weak currents within chiral effective field theory. I show that gauge and chiral symmetry requirements lead to the well-known continuity equations for the current and charge operators which, however, get modified at higher orders. Regularization of the current will be also discussed. I demonstrate that implementation of a cutoff regulator in a naive way leads to violation of chiral symmetry. To respect the underlying symmetries I propose to use higher derivative regularization in the nuclear forces and cu…
We make use of the formalism developed in Ref. [1], and calculate the chargino mediated baryogenesis in the Minimal Supersymmetric Standard Model. The formalism makes use of a gradient expansion of the Kadanoff-Baym equations for mixing fermions. For illustrative purposes, we first discuss the semiclassical transport equations for mixing bosons in a space-time dependent Higgs background. To calculate the baryon asymmetry, we solve a standard set of diffusion equations, according to which the chargino asymmetry is transported to the top sector, where it biases sphaleron transitions. At the end …
We present the general ansatz, the energy density and the Chern-Simons charge for static axially symmetric configurations in the bosonic sector of the electroweak theory. Containing the sphaleron, the multisphalerons and the sphaleron-antisphaleron pair at finite mixing angle, the ansatz further allows the construction of the sphaleron and multisphaleron barriers and of the bisphalerons at finite mixing angle. We conjecture that further solutions exist.
We propose to study the mass spectrum of the heavy-light mesons to probe the structure of the spin-isospin correlation in the nuclear medium. We point out that the spin-isospin correlation in the nuclear medium generates a mixing among the heavy-light mesons carrying different spins and isospins such as $D^+$, $D^0$, $D^{\ast +}$, and $D^{\ast 0}$ mesons. We use two types of correlations motivated by the skyrmion crystal and the chiral density wave as typical examples to obtain the mass splitting caused by the mixing. Our result shows that the structure of the mixing reflects the pattern of th…
If the electroweak symmetry is broken by some unspecified strong dynamics, composite fermions may exist with definite transformation properties under SU(2)_L x SU(2)_R/SU(2)_{L+R} and may play a role in giving masses by mixing to all the standard quarks and leptons. Assuming this to be the case, we analyze the role of Singlets, Doublets and Triplets in the ElectroWeak Precision Tests and in Flavour Physics. Doublets and Triplets are generically disfavoured. In the Singlet case, we specify the breaking patterns of the flavour group that allow to keep the CKM picture of flavour physics and we di…
We calculate the oblique electroweak corrections and confront with the experiments in an extension of the Standard Model. The new fields added are a vector-like weak doublet and a singlet fermion. After electroweak symmetry breaking there is a mixing between the components of the new fields, but no mixing allowed with the standard fermions. Four electroweak parameters, $\hat{S}$, $\hat{T}$, W, Y are presented in the formalism of Barbieri et al., these are the generalization of the Peskin-Takeuchi S, T, U's. The vector-like extension is slightly constrained, $\hat{T}$ requires the new neutral f…
We present results for Delta I=3/2 and Delta S=2 matrix elements relevant for CP violation in K->Pi Pi decays and for the K_S-K_L mass difference in the standard model and beyond. They were obtained with Neuberger fermions on quenched gauge configurations generated with the Wilson plaquette action at beta=6.0 on an 18^3x64 lattice.
A possible mechanism for the formation of heavy-mass elements in supernovae is the rapid neutron-capture-mechanism (r-process). It depends upon the electron-fraction $Y_e$, a quantity which is determined by beta-decay-rates. In this paper, we focus on the calculation of electroweak decay-rates in presence of massive neutrinos. The resulting expressions are then used to calculate nuclear reactions entering the rapid-neutron capture. We fix the astrophysical parameters to the case of a core-collapse supernova. The neutrino sector includes a mass scheme and mixing angles for active neutrinos, and…
Cross sections for the concurrent production of pairs of quarkonia (J/psi, Upsilon) and/or gauge bosons (W, Z) from double-parton scatterings (DPS) in high-energy proton-nucleus and nucleus-nucleus collisions at the LHC are calculated. The estimates are based on next-to-leading-order perturbative QCD predictions, including nuclear modifications of the parton densities, for the corresponding single-scattering cross sections. Expected event rates for J/psi+J/psi, J/psi+Upsilon, J/psi+W, J/psi+Z, Upsilon+Upsilon, Upsilon+W, Upsilon+Z, and same-sign W+W production in their (di)leptonic decay modes…
It happens that $s^2$ and $\hat s^2$ are equal with 0.1% accuracy, though they are split by radiative corrections and a natural estimate for their difference is 1%. This degeneracy occurs only for $m_t$ value close to $170\GeV$, so no deep physical reason can be attributed to it. However, another puzzle of the Standard Model, the degeneracy of $s_\Eff^2$ and $s^2$, is not independent of the previous one since a good physical reason exists for $s_\Eff^2$ and $\hat s^2$ degeneracy. We present explicit formulas which relate these three angles.
The charge form factor and weak decay constant of the pion as well as the pion-quark coupling constant in symmetric nuclear matter are explored in the framework of the Nambu--Jona-Lasinio model, where the pion is described as a bound state of dressed quark-antiquark pair obtained by the Bethe-Salpeter equation. For the in-medium current quark properties, we adopt the quark-meson coupling model, which describes successfully many hadron properties in a nuclear medium. The pion decay constant and the pion-quark coupling constant are found to decrease with increasing density as well as the magnitu…
We study the constraints from updated electroweak data on the three leptophobic Z' models, the $η$ model with an appropriate $U(1)'-U(1)_Y$ kinetic mixing, a Z' model motivated by the flipped SU(5) \times U(1) unification, and the phenomenological Z' model of Agashe, Graesser, and Hinchliffe. The $Z-Z'$ mixing effects are parametrized in terms of a positive contribution to the $T$ parameter, $T_{new}$, and the effective mass mixing parameter, $\barξ$. All the theoretical predictions for the $Z$ boson parameters, the $W$ boson mass and the observables in low-energy neutral current experiments a…
The effect of mixing of the vector and axial vector correlation functions in the nuclear medium arising from the interaction of nuclear pions with corresponding interpolating currents is considered. It is shown that the mass difference between $ρ$ and $a_1$ meson gets smaller with the increase of the nuclear density reflecting the phenomena of partial restoration of chiral symmetry whereas the absolute values of meson masses may both decrease and increase in nuclear medium depending on the model used for the phenomenological spectral density.
In the Standard Model (SM), the Higgs mass around 125 GeV implies that the electroweak vacuum is metastable since the quartic Higgs coupling turns negative at high energies. I point out that a tiny mixing of the Higgs with a heavy singlet can make the electroweak vacuum completely stable. This is due to a tree level correction to the Higgs mass-coupling relation, which survives in the zero-mixing/heavy-singlet limit. Such a situation is experimentally indistinguishable from the SM, unless the Higgs self-coupling can be measured. As a result, Higgs inflation and its variants can still be viable…
We present new sets of nuclear parton distribution functions (nPDFs) at next-to-leading order and next-to-next-to-leading order in perturbative QCD. Our analyses are based on deeply inelastic scattering data with charged-lepton and neutrino beams on nuclear targets, and experimental data from measurements of $W^{\pm},\,Z$ boson production in p+Pb collisions at the LHC. In addition, a set of proton baseline PDFs is fitted within the same framework and with the same theoretical assumptions. The results of our global QCD analysis are compared to existing nPDF sets and to the previous nPDF set TUJ…
Topcolor--assisted technicolor provides a dynamical explanation for electroweak and flavor symmetry breaking and for the large mass of the top quark without unnatural fine tuning. A major challenge is to generate the observed mixing between heavy and light generations while breaking the strong topcolor interactions near~$1\,\tev$. I argue that these phenomena, as well as electroweak symmetry breaking, are intimately connected and I present a scenario for them based on nontrivial patterns of technifermion condensation. I also exhibit a class of models realizing this scenario. This picture leads…
We propose an alternative mechanism for leptogenesis at the electroweak scale, through the decays of a left-handed sneutrino. This scenario may be realized in supersymmetric models with non-zero Majorana masses for the neutrino superfield that lead to mixing and mass splitting between the left-handed sneutrino and the corresponding antisneutrino. Soft supersymmetry breaking provides new sources of CP violation in sneutrino-antisneutrino mixing that can generate a lepton asymmetry in decays of the left-handed sneutrino. We show how the three Sakharov conditions for generating the observed baryo…
The electroweak mixing angle is a fundamental parameter of the theory of electroweak interactions. Its value has been measured precisely at the $\mathrm{Z}$-pole at colliders. In this contribution, we propose to exploit measurements of Neutral-Current Drell-Yan production at the Large Hadron Collider at large invariant dilepton masses to determine the energy scale dependence (running) of the electroweak mixing angle in the $\bar{\text{MS}}$ renormalisation scheme, $\sin^2θ_{W,\ell}^{\bar{\text{MS}}}(μ)$. Such a measurement can be used to confirm the Standard Model predictions for the $\bar{\te…
We construct the most general effective Lagrangian of the matter sector of the Standard Model, including mixing and CP violating terms. The Lagrangian contains the effective operators that give the leading contribution in theories where the physics beyond the Standard Model shows at a scale $Λ>>M_{W}$. We perform the diagonalization and passage to the physical basis in full generality. We determine the contribution to the different observables and discuss the possible new sources of CP violation, the idea being to be able to gain some knowledge about new physics beyond the Standard Model from …
We present a model of neutrino masses within the framework of the EW-$ν_R$ model in which the experimentally desired form of the PMNS matrix is obtained by applying an $A_4$ symmetry to the \emph{Higgs singlet sector} responsible for the neutrino Dirac mass matrix. This mechanism naturally avoids potential conflict with the LHC data which severely constrains the Higgs sector, in particular the Higgs doublets. Moreover, by making a simple $ans\ddot{a}tz$ we extract $\mathcal{M}_l {\mathcal{M}_l}^\dagger$ for the charged lepton sector. A similar $ans\ddot{a}tz$ is proposed for the quark sector. …
Nuclear parton distribution functions (nPDFs) can be determined in a global QCD analysis using a wide range of experimental data. In addition to older fixed-target deep inelastic scattering and Drell-Yan (DY) dilepton production data, several analyses from p+Pb collisions at the LHC provide further constraints and extend the kinematic reach of applicable data. Here we present an update of our previous TUJU19 analysis where we now include also electroweak-boson production data recently measured by ATLAS and CMS. For the first time, LHC data are included in a nPDF analysis performed at next-to-n…
Current neutrino experimental data on neutrino mixing are well describes by Tri-bi-maximal mixing, which is predicts sin^{2}θ_{12}=1/3,zero U_{e3} and θ_{23}=45^{o}. We consider the planck scale operator on neutrino mixing. We assume that the neutrino masses and mixing arise through physics at a scale intrimediate between planck scale and the electroweak braking scale. We also assume, that just above the electroweak breaking scale neutrino mass are nearly degenerate and the mixing is tri-bi-maximal. Quantum gravity (Planck scale) effects lead to an effective SU(2)_{L}\times U(1) invariant dime…
A systematic error in the extraction of $\sin^2 θ_W$ from nuclear deep inelastic scattering of neutrinos and antineutrinos arises from higher-twist effects arising from nuclear shadowing. We explain that these effects cause a correction to the results of the recently reported significant deviation from the Standard Model that is potentially as large as the deviation claimed, and of a sign that cannot be determined without an extremely careful study of the data set used to model the input parton distribution functions.
We will explore the consequences on the electroweak breaking condition, the mass of supersymmetric partners and the scale at which supersymmetry is broken, for arbitrary values of the supersymmetric parameters tan(beta) and the stop mixing X_t, which follow from the Higgs discovery with a mass m_H\simeq 126 GeV at the LHC. Within the present uncertainty on the top quark mass we deduce that radiative breaking requires tan(beta) \gtrsim 7 for maximal mixing X_t\simeq \sqrt{6}, and tan(beta) \gtrsim 20 for small mixing X_t\lesssim 1. The scale at which supersymmetry is broken \mathcal M can be of…
We consider, in the context of the minimal supersymmetric standard model, the case where the gravitino weighs 10^6 GeV or more, which is preferred by various cosmological difficulties associated with unstable gravitinos. Despite the large Higgs mixing parameter B together with the little hierarchy to other soft supersymmetry breaking masses, a light higgsino with an electroweak scale mass leads to successful electroweak symmetry breaking, at the price of fine-tuning the higgsino mixing mu parameter. Furthermore the light higgsinos produced at the decays of gravitinos can constitute the dark ma…
Little Higgs Models have been introduced to resolve the fine-tuning problems associated with the stability of the electroweak scale and the constraints imposed by the precision electroweak analysis of experiments testing the Standard Model of particle physics. Flavor physics provides a sensitive probe of the new physics contained in these models at next-to-leading order.
We present results for the ΔS=2 matrix elements which are required to study neutral kaon mixing in the standard model (SM) and beyond (BSM). We also provide leading chiral order results for the matrix elements of the electroweak penguin operators which give the dominant ΔI=3/2 contribution to direct CP violation in K->ππdecays. Our calculations were performed with Neuberger fermions on two sets of quenched Wilson gauge configurations at inverse lattice spacings of approximately 2.2 GeV and 1.5 GeV. All renormalizations were implemented non-perturbatively in the RI/MOM scheme, where we accounte…
The radiative corrections involved in the precise determination of the electroweak mixing angle measured at the Z-peak are reviewed in detail, with particular emphasis on the new calculation of two-loop heavy top effects. This example serves as a brief pedagogical introduction to the problems and techniques of higher order electroweak calculations.
