1,870 research outputs found

    Electroweak Radiative Corrections To Polarized M{\o}ller Scattering Asymmetries

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    One loop electroweak radiative corrections to left-right parity violating M{\o}ller scattering (e−e−→e−e−e^-e^-\to e^-e^-) asymmetries are presented. They reduce the standard model (tree level) prediction by 40±3\pm 3 \% where the main shift and uncertainty stem from hadronic vacuum polarization loops. A similar reduction also occurs for the electron-electron atomic parity violating interaction. That effect can be attributed to an increase of sin⁥2ΞW(q2)\sin^2\theta_W(q^2) by 3%3\% in running from q2=mZ2q^2=m_Z^2 to 0. The sensitivity of the asymmetry to ``new physics'' is also discussed.Comment: 14 pages, Revtex, postscript file including figures is available at ftp://ttpux2.physik.uni-karlsruhe.de/ttp95-14/ttp95-14.ps or via WWW at http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints/ (129.13.102.139

    Semileptonic decays of light quarks beyond the Standard Model

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    We describe non-standard contributions to semileptonic processes in a model independent way in terms of an SU(2)_L X U(1)_Y invariant effective lagrangian at the weak scale, from which we derive the low-energy effective lagrangian governing muon and beta decays. We find that the deviation from Cabibbo universality, \Delta_CKM = |V_ud|^2 + |V_us|^2 + |V_ub|^2 - 1, receives contributions from four effective operators. The phenomenological bound of \Delta_CKM = -1E-4 +- 6E-4 provides strong constraints on all four operators, corresponding to an effective scale greater than 11 TeV (90% CL). Depending on the operator, this constraint is at the same level or better then the Z pole observables. Conversely, precision electroweak constraints alone would allow universality violations as large as \Delta_CKM = -0.01 (90% CL). An observed nonzero \Delta_CKM at this level could be explained in terms of a single four-fermion operator which is relatively poorly constrained by electroweak precision measurements.Comment: 23 pages, 1 table and 5 eps figure

    Evidence for Bosonic Electroweak Corrections in the Standard Model

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    We present strong indirect evidence for the contribution of bosonic electroweak corrections in the Standard Model. Although important conceptually, these corrections give subleading contributions in current high energy experiments, and it was previously thought that they are difficult to detect. We also discuss the separate contribution of the Higgs boson.Comment: 9 pages (LaTeX + 3 PS figures, needs psfig

    K_L \ra \mu^\pm e^\mp \nu \overline{\nu} as background to K_L \ra \mu^\pm e^\mp

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    We consider the process K_L \ra \mu^\pm e^\mp \nu \overline{\nu} at next to leading order in chiral perturbation theory. This process occurs in the standard model at second order in the weak interaction and constitutes a potential background in searches for new physics through the modes K_L \ra \mu^\pm e^\mp. We find that the same cut, MÎŒe>489M_{\mu e}>489~MeV, used to remove the sequential decays K_{l3}\ra \pi_{l2} pushes the B(K_L \ra \mu^\pm e^\mp \nu \overline{\nu}) to the 10−2310^{-23} level, effectively removing it as a background.Comment: 8 pages, LaTeX, 1 figure appended as postscript file after \end{document}. Fermilab-Pub-93/024-

    Inelastic Channels in the Electroweak Symmetry-Breaking Sector

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    It has been argued that if light Higgs bosons do not exist then the self--interactions of WW's become strong in the TeV region and can be observed in longitudinal WWWW scattering. We present a model with many inelastic channels in the WWWW scattering process, corresponding to the creation of heavy fermion pairs. The presence of these heavy fermions affects the elastic scattering of WW's by propagating in loops, greatly reducing the amplitudes in some charge channels. Consequently, the symmetry--breaking sector cannot be fully explored by using, for example, the W+W+W^+W^+ mode alone; all WW→WWWW \rightarrow WW scattering modes must be measured.}Comment: 10 pages, phyzzx, JHU-TIPAC-92001

    Electroweak higher-order effects and theoretical uncertainties in deep-inelastic neutrino scattering

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    A previous calculation of electroweak O(alpha) corrections to deep-inelastic neutrino scattering, as e.g. measured by NuTeV and NOMAD, is supplemented by higher-order effects. In detail, we take into account universal two-loop effects from \Delta\alpha and \Delta\rho as well as higher-order final-state photon radiation off muons in the structure function approach. Moreover, we make use of the recently released O(alpha)-improved parton distributions MRST2004QED and identify the relevant QED factorization scheme, which is DIS like. As a technical byproduct, we describe slicing and subtraction techniques for an efficient calculation of a new type of real corrections that are induced by the generated photon distribution. A numerical discussion of the higher-order effects suggests that the remaining theoretical uncertainty from unknown electroweak corrections is dominated by non-universal two-loop effects and is of the order 0.0003 when translated into a shift in sin^2\theta_W=1-MW^2/MZ^2. The O(alpha) corrections implicitly included in the parton distributions lead to a shift of about 0.0004.Comment: 25 pages, latex, 8 postscript figure

    Assessing the Sustainability Impact of Improving Secondary Steel Production: Lessons Learned from an Italian Plant

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    This work presents a sustainability assessment approach to evaluate technological innovations in secondary steel production making use of Electric Arc Furnace (EAF) technology. The assessment covers the environmental, social, and economic dimensions of sustainability by combining different tools (Life Cycle Assessment and Analytic Hierarchy Process), and also provides an integrated assessment of the overall sustainability. The approach, which can also be used to support decision-making, has been applied to a real case study of a steel plant located in Northern Italy. In the case study, environmental sustainability is positively impacted mainly by increased metal yield and reduced furnace energy consumption. The greatest social sustainability benefits are mainly related to improved ergonomic and safety conditions for workers (reduced demand for physical effort, manual handling and repetitiveness, and lower risk of accidents), as a consequence of the introduction of Industry 4.0 technologies. Regarding economic sustainability, a positive impact related to reduced cycle time, increased metal yield and quality yield, reduced maintenance and quality control costs was observed. The integrated assessment of the overall sustainability has proven to be a viable approach to manage trade-offs between the different dimensions of sustainability

    Fermi Constants and ``New Physics''

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    Various precision determinations of the Fermi constant are compared. Included are muon and (leptonic) tau decays as well as indirect prescriptions employing \alpha, m_Z, m_W, \ssthwmzms, \Gamma(Z\to\ell^+\ell^-), and Γ(Z→ΜΜˉ)\Gamma(Z \to \nu\bar \nu) as input. Their good agreement tests the standard model at the ±0.1\pm 0.1% level and provides stringent constraints on new physics. That utility is illustrated for: heavy neutrino mixing, 2 Higgs doublet models, S, T, and U parameters and excited W∗±W^{\ast^\pm} bosons (Kaluza-Klein excitations). For the last of those examples, m_{W^\ast}\gsims 2.9 TeV is found.Comment: 14 page
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