Right-handed W-boson Research Articles

Testing quark mixing in minimal left–right symmetric models with b-tags at the LHC

Motivated by a hint in a CMS search for right-handed W-bosons in eejj final states, we propose an experimental test of quark-mixing matrices in a general left–right symmetric model, based on counting the numbers of b-tags from right-handed W-boson hadronic decays. We find that, with our test, differences between left- and right-handed quark-mixing matrices could be detected at the LHC with s=14 TeV. With an integrated luminosity of about 20/fb, our test is sensitive to right-handed quark-mixing angles as small as about 30° and with 3000/fb, our test's sensitivity improves to right-handed mixing angles as small as about 7.5°. Our test's sensitivity might be further enhanced by tuning b-tagging efficiency against purity.

Neutron electric dipole moment constraint on scale of minimal left-right symmetric model

Using an effective field theory approach, we calculate the neutron electric dipole moment (nEDM) in the minimal left-right symmetric model with both explicit and spontaneous CP violations. We integrate out heavy particles to obtain flavor-neutral CPviolating effective Lagrangian. We run the Wilson coefficients from the electroweak scale to the hadronic scale using one-loop renormalization group equations. Using the state-of-theart hadronic matrix elements, we obtain the nEDM as a function of right-handed W-boson mass and CP-violating parameters. We use the current limit on nEDM combined with the kaon-decay parameter ϵ to provide the most stringent constraint yet on the left-right symmetric scale $$M_{w_{R}}> (10 \pm 3) {\rm TeV} $$ .

High energy neutrino in a nuclear environment: mirror asymmetry of the shadowing effect

The parity non-conservation effect in diffractive charged current deep inelastic scattering is quantified in terms of colour dipole sizes of left-handed and right-handed electroweak bosons. We identify the origin and estimate the strength of the left–right asymmetry effect and present comparison with experimental data on the parity-odd structure function . We study the shadowing effect in absorption of left-handed and right-handed W-bosons by atomic nuclei. The target nucleus is found to be quite transparent for the charmed-strange Fock component of the light-cone W+ in the helicity state λ = +1 and rather opaque for the -dipole with λ = −1.

Left–right asymmetry of nuclear shadowing in charged current DIS

We study the shadowing effect in highly asymmetric diffractive interactions of left- and right-handed W-bosons with atomic nuclei. The target nucleus is found to be quite transparent for the charmed-strange Fock component of the light-cone W+ in the helicity state λ=+1 and rather opaque for the cs¯ dipole with λ=−1. The shadowing correction to the structure function ΔxF3=xF3νN−xF3ν¯N extracted from νFe and ν¯Fe data is shown to make up about 20% in the kinematical range of CCFR/NuTeV.

Michel parameters averages and interpretation

The new measurements of Michel parameters in τ decays are combined to world averages. From these measurements model independent limits on non-standard model couplings are derived and interpretations in the framework of specific models are given. A lower limit of 2.5 tan β GeV on the mass of a charged Higgs boson in models with two Higgs doublets can be set and a 229 GeV limit on a right-handed W-boson in left-right symmetric models (95% c.l.).

A large scale double beta and dark matter experiment: On the physics potential of GENIUS

The physics potential of GENIUS, a recently proposed double beta decay and dark matter experiment is discussed. The experiment will allow to probe neutrino masses down to 10−(2–3) eV. GENIUS will test the structure of the neutrino mass matrix, and therefore implicitly neutrino oscillation parameters comparable or superior in sensitivity to the best proposed dedicated terrestrial neutrino oscillation experiments. If the 10-3 eV level is reached, GENIUS will even allow to test the large angle MSW solution of the solar neutrino problem. Even in its first stage GENIUS will confirm or rule out degenerate or inverted neutrino mass scenarios, which have been widely discussed in the literature as a possible solution to current hints on finite neutrino masses and also test the νe ↔ νμ hypothesis of the atmospheric neutrino problem. GENIUS would contribute to the search for R-parity violating SUSY and right-handed W-bosons on a scale similar or superior to LHC. In addition, GENIUS would largely improve the current 0νββ decay searches for R-parity conserving SUSY and leptoquarks.

A large scale double beta and dark matter experiment: GENIUS

The recent results from the HEIDELBERG-MOSCOW experiment have demonstrated the large potential of double beta decay to search for new physics beyond the Standard Model. To increase by a major step the present sensitivity for double beta decay and dark matter search much bigger source strengths and much lower backgrounds are needed than used in experiments under operation at present or under construction. We present here a study of a project proposed recently [1], which would operate one ton of ‘naked’ enriched GErmanium-detectorsinliquid NItrogenas shielding in an Underground Setup (GENIUS). It improves the sensitivity to neutrino masses to 0.01 eV. A ten ton version would probe neutrino masses even down to 10−3 eV. The first version would allow to test the atmospheric neutrino problem, the second at least part of the solar neutrino problem. Both versions would allow in addition significant contributions to testing several classes of GUT models. These are especially tests of R-parity breaking supersymmetry models, leptoquark masses and mechanism and right-handed W-boson masses comparable to LHC. The second issue of the experiment is the search for dark matter in the universe. The entire MSSM parameter space for prediction of neutralinos as dark matter particles could be covered already in a first step of the full experiment with the same purity requirements, but using only 100 kg of 76Ge or even of natural Ge making the experiment competitive to LHC in the search for supersymmetry. The layout ofthe proposed experiment is discussed and the shielding and purity requirements are studied using GEANT Monte Carlo simulations. As a demonstration of the feasibility of the experiment first results of operating a ‘naked’ Ge detector in liquid nitrogen are presented.

MAJOR 1.5 — A Monte Carlo generator for heavy Majorana neutrinos in ep collisions

The Monte Carlo generator Major simulates the production and decay of heavy Majorana neutrinos via lepton mixing or exchange of ‘light’ right-handed W-bosons in deep inelastic scattering, i.e. e ± p → NX → e ± W ± X or ν e ZX. Physics and programming aspects are described in this manual.

Testing the Lorentz structure of the charged weak current in $\tau$ -decays

We review the current experimental situation on the determination of the Lorentz structure of the charged weak current in τ decays. We propose a method to extent these studies to decays of τ leptons to righthanded daughter leptons which are forbidden in the standard model. We reanalyse the available data in the framework of specific models and derive limits on the mass of charged Higgs bosons of m(H±) > 1.5 tan β GeV at 90 % c.l. and on righthanded W-bosons of m(W2) > 230 GeV at 90 % c.l., valid if the righthanded neutrinos associated with it are light compared to the τ.

Double beta decay in left-right symmetric models

Left-right symmetric models provide a natural framework for neutrinoless double beta (0νββ) decay. In the analysis of 0νββ decay in left-right symmetric models, however, it is usually assumed that all neutrinos are light. On the other hand, heavy right-handed neutrinos appear quite naturally in left-right symmetric models and should therefore not be neglected. Assuming the existence of at least one right-handed heavy neutrino, absence of 0νββ decay of 76Ge currently provides the following limits on the mass and mixing angle of right-handed W-bosons: m W R ≥ 1.1 TeV and tan(ζ) ≤ 4.7 × 10 −3 for a particular value of the effective right-handed neutrino mass, 〈 m N ( V) 〉 = 1 TeV, and in the limit of infinitely massive doubly charged Higgs ( Δ −−). The effects of the inclusion of the Higgs triplet on 0νββ decay are also discussed.

Low energy restrictions for a flipped left-right symmetric model

I consider some low energy restrictions for a “flipped” left-right symmetric model containing exotic fermions ofE6 and a right-handedW-boson, all with oddR-parity. The new interactions due toWR-exchange have no significant impact on rare kaon decays, because theWR does not couple tod,s,b quarks. On the other hand,WR exchanges might induce rare processes like\(D - \bar D\) mixing,\(D^0 \to \mu \bar \mu ,D^0 \to \mu \bar e,\mu \to e\gamma ,\mu \to 3e\), and μN→eN. It turns out that the strongest bound is obtained from\(D - \bar D\) mixing. With reasonable extra assumptions, it is found that the exotic right-handed W-boson is likely to be heavier than 500 to 1500 GeV.

Left-right symmetry and CP violation in the B system

We have reanalyzed a version of LR-symmetric models in which the right-handed W-boson could be light. Excluding several fine-tunings, it is shown that, due to constraints from ϵ, M W R ⪆ 5 TeV , which would render its effects in heavy quark systems small. If fine-tuning is allowed, there are interesting effects in the B system - in particular, B s 0- B s 0 mixing can be small, the CP asymmetry in B d→ ψK s may be negative, and there is CP violation in Cabibbo allowed B s decays.