Evidence for Bosonic Electroweak Corrections in the Standard Model

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

An improved calculation of the isospin-symmetry-breaking corrections to superallowed Fermi beta decay

We report new shell-model calculations of the isospin-symmetry-breaking correction to superallowed nuclear beta decay. The most important improvement is the inclusion of core orbitals, which are demonstrated to have a significant impact on the mismatch in the radial wave functions of the parent and daughter states. We determine which core orbitals are important to include from an examination of measured spectroscopic factors in single-nucleon pick-up reactions. We also examine the new radiative-correction calculation by Marciano and Sirlin and, by a simple reorganization, show that it is possible to preserve the conventional separation into a nucleus-independent inner radiative term and a nucleus-dependent outer term. We tabulate new values for the three theoretical corrections for twenty superallowed transitions, including the thirteen well-studied cases. With these new correction terms the corrected Ft values for the thirteen cases are statistically consistent with one another and the anomalousness of the 46V result disappears. These new calculations lead to a lower average Ft value and a higher value of Vud. The sum of squares of the top-row elements of the CKM matrix now agrees exactly with unitarity.Comment: 15 pages, 2 postscript figures, revtex

Thirty Years of Precision Electroweak Physics

We discuss the development of the theory of electroweak radiative corrections and its role in testing the Standard Model, predicting the top quark mass, constraining the Higgs boson mass, and searching for deviations that may signal the presence of new physics.Comment: 19 pages, acknowledgments added, J.J.Sakurai Prize Talk, APS Meeting, Albuquerque, N.M., April 2002. To appear in a future issue of Journal of Physics

Analysis of the chargino and neutralino mass parameters at one-loop level

In the Minimal Supersymmetric Standard Model (MSSM) the masses of the neutralinos and charginos depend on the gaugino and higgsino mass parameters M, M' and $\mu$. If supersymmetry is realized, the extraction of these parameters from future high energy experiments will be crucial to test the underlying theory. We present a consistent method how on-shell parameters can be properly defined at one-loop level and how they can be determined from precision measurements. In addition, we show how a GUT relation for the parameters M and M' can be tested at one-loop level. The numerical analysis is based on a complete one-loop calculation. The derived analytic formulae are given in the appendix.Comment: 16 pages, 8 figure

RG Invariance of the Pole Mass in the Minimal Subtraction Scheme

We prove the renormalization group(RG) invariance of the pole mass with respect to the RG functions of the minimal subtraction(MS) scheme and illustrate this in case of the the neutral scalar field theory both in the symmetric and in the broken symmetry phase

Width and Partial Widths of Unstable Particles in the Light of the Nielsen Identities

Fundamental properties of unstable particles, including mass, width, and partial widths, are examined on the basis of the Nielsen identities (NI) that describe the gauge dependence of Green functions. In particular, we prove that the pole residues and associated definitions of branching ratios and partial widths are gauge independent to all orders. A simpler, previously discussed definition of branching ratios and partial widths is found to be gauge independent through next-to-next-to-leading order. It is then explained how it may be modified in order to extend the gauge independence to all orders. We also show that the physical scattering amplitude is the most general combination of self-energy, vertex, and box contributions that is gauge independent for arbitrary s, discuss the analytical properties of the NI functions, and exhibit explicitly their one-loop expressions in the Z-gamma sector of the Standard Model.Comment: 20 pages (Latex); minor changes included, accepted for publication in Phys. Rev.

Improved full one--loop corrections to A^0 -> \sq_1 \sq_2 and \sq_2 -> \sq_1 A^0

We calculate the full electroweak one-loop corrections to the decay of the CP-odd Higgs boson A^0 into scalar quarks in the minimal supersymmetric extension of the Standard Model (MSSM). Due to the complex structure of the electroweak sector a proper renormalization of many parameters in the on-shell renormalization scheme is necessary. For the decay into sbottom quarks, especially for large tanb, the corrections can be very large in the on-shell renormalization scheme, which makes the perturbation series unreliable. We solve this problem by an appropriate definition of the tree-level coupling in terms of running quark masses and running trilinear couplings A_q. We also discuss the decay of heavy scalar quarks into light scalar quarks and A^0. We find that the corrections are significant and therefore cannot be neglected.Comment: 15 pages, 9 figures, Fig. 8 correcte

Supersymmetric Electroweak Corrections to Single Top Quark Production at the Fermilab Tevatron

We have calculated the $O(\alpha_{ew} M_t^2/M_W^2)$ supersymmetric electroweak corrections to single top quark production via $q\bar q' \to t\bar b$ at the Fermilab Tevatron in the minimal supersymmetric model. The supersymmetric electroweak corrections to the cross section are a few percent for $tan \beta> 1$, and can exceed 10% for $tan\beta<1$. The combined effects of SUSY electroweak corrections and the Yukawa corrections can exceed 10% for favorable parameter values, which might be observable at a high-luminosity Tevatron.Comment: 13 pages, 4 figures available at reques

Remarks on the Upper Bounds on the Higgs Boson Mass from Triviality

We study the effects of the one-loop matching conditions on Higgs boson and top quark masses on the triviality bounds on the Higgs boson mass using $\beta_{\lambda}$ with corrected two-loop coefficients. We obtain quite higher results than previous ones and observe that the triviality bounds are not nearly influenced by varying top quark mass over the range measured at CDF and D0. The effects of typo errors in $\beta_{\lambda}^{(2)}$ and the one-loop matching condition on the top quark mass are negligible. We estimate the size of effects on the triviality bounds from the one-loop matching condition on the Higgs boson mass.Comment: 9 pages, tar'ed gzip'ed uuencoded files, LaTex, 5 PostScript figures. To appear in Physical Review

Calculated corrections to superallowed Fermi beta decay: New evaluation of the nuclear-structure-dependent terms

The measured $ft$-values for superallowed $0^{+} \to 0^{+}$ nuclear $\beta$-decay can be used to obtain the value of the vector coupling constant and thus to test the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. An essential requirement for this test is accurate calculations for the radiative and isospin symmetry-breaking corrections that must be applied to the experimental data. We present a new and consistent set of calculations for the nuclear-structure-dependent components of these corrections. These new results do not alter the current status of the unitarity test -- it still fails by more than two standard deviations -- but they provide calculated corrections for eleven new superallowed transitions that are likely to become accessible to precise measurements in the future. The reliability of all calculated corrections is explored and an experimental method indicated by which the structure-dependent corrections can be tested and, if necessary, improved.Comment: Revtex4, one figur