Search

We study the lepton flavor violation in the supersymmetric seesaw model taking into account recent experimental improvements, especially for the Higgs boson mass measurement, direct searches of superpartners and the rare decay of B_s -> mu+ mu- at the LHC, the neutrino mixing angle of theta_{13} at the neutrino experiments, and the search of mu -> e gamma at the MEG experiment. We obtain the latest constraints on the parameters in the supersymmetry breaking terms and study the effect on the lepton flavor violating decays of tau -> mu gamma and mu -> e gamma. In particular, we consider two kinds of assumption on the structures in the Majorana mass matrix and the neutrino Yukawa matrix. In the case of the Majorana mass matrix proportional to the unit matrix, allowing non-vanishing CP violating parameters in the neutrino Yukawa matrix, we find that the branching ratio of tau -> mu gamma can be larger than 10^{-9} within the improved experimental limit of mu -> e gamma. We also consider the neutrino Yukawa matrix that includes the mixing only in the second and third generations, and find that a larger branching ratio of tau -> mu gamma than 10^{-9} is possible with satisfying the recent constraints., 25 pages, 7 figures

This article reviews the current theoretical and experimental status of the field of muon decay and its potential to search for new physics beyond the Standard Model. The importance of rare muon processes with lepton flavor violation is highly stressed, together with precision measurements of normal muon decay. Recent up-to-date motivations of lepton flavor violation based on supersymmetric models, in particular supersymmetric grand unified theories, are described along with other theoretical models. Future prospects of experiments and muon sources of high intensity for further progress in this field are also discussed., Comment: 109 pages, 37 postscript figures, uses REVTEX.sty

The $b\ensuremath{\rightarrow}{\mathrm{sl}}^{+}{l}^{\ensuremath{-}}$ process is studied in the minimal supergravity model in detail. Taking into account the long-distance contributions from the $c\overline{c}$ resonances, we calculate the branching ratio and the lepton forward-backward asymmetry in this model. We find that there is a strong correlation between the branching ratios of $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ and $b\ensuremath{\rightarrow}{\mathrm{sl}}^{+}{l}^{\ensuremath{-}}$ processes and that the interference effect can change the $b\ensuremath{\rightarrow}{\mathrm{sl}}^{+}{l}^{\ensuremath{-}}$ branching ratio in the off-resonance regions by up to \ifmmode\pm\else\textpm\fi{}15% depending on the relative phase between the long- and short-distance contributions. Using various phenomenological constraints including the branching ratio of $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$, we show that there are regions in the parameter space where the branching ratio of $b\ensuremath{\rightarrow}{\mathrm{sl}}^{+}{l}^{\ensuremath{-}}$ is enhanced by about 50% compared to the standard model (SM). We also show that the branching ratio of $b\ensuremath{\rightarrow}s\ensuremath{\nu}\overline{\ensuremath{\nu}}$ is reduced at most by 10% from the SM prediction.

A search for the lepton-flavor violating $\mu^{+}\rightarrow e^{+}\gamma$ decay using polarized muons is proposed. By measuring the angular distribution of $e^{+}$s with respect to the muon spin direction, in particular antiparallel $e^{+}$s, the serious physics background from $\mu^{+}\rightarrow e^{+}\nu\overline{\nu}\gamma$ as well as accidental background from normal muon decay accompanied by a high-energy photon can be suppressed significantly. In addition to the enhancement of the sensitivity, the angular distribution would discriminate among different extensions to the Standard Model, once the signal is observed.

We present a framework to analyze the effects of new physics beyond the standard model on $B\ensuremath{-}\overline{B}$ mixing and $\mathrm{CP}$ violation in $B$ decays in a model-independent manner. Assuming that the tree level decay amplitudes are dominated by the standard model ones, new physics contributions to $B\ensuremath{-}\overline{B}$ mixing can be extracted from several measurements at $B$ factories. Using this framework, we show the present constraint on new physics contributions to $B\ensuremath{-}\overline{B}$ mixing and illustrate the constraints expected to be given by future experiments at $B$ factories. We also point out the possibility that $\mathrm{CP}$ asymmetries in $B\ensuremath{\rightarrow}\ensuremath{\psi}{K}_{S}$, $B\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$, and $B\ensuremath{\rightarrow}\mathrm{DK}$ modes look consistent with the standard model, even if a large new physics contribution is present in $B\ensuremath{-}\overline{B}$ mixing.

{ital B}{sup 0}-{bar {ital B}}{sup 0} mixing and a {ital CP} violation parameter in {ital K}{sup 0}-{bar {ital K}}{sup 0} mixing, {epsilon}{sub {ital K}}, are studied in the minimal supergravity model. We solve the one-loop renormalization group equations for the minimal supersymmetric standard model parameters numerically in order to determine the masses and mixings of the supersymmetric particles, while all off-diagonal (generation mixing) elements and phases of Yukawa coupling matrices and those of squark mass matrices are taken into account. Applying the radiative electroweak symmetry-breaking condition and phenomenological constraints including the recent measurement of the {ital b}{r_arrow}{ital s}{gamma} inclusive branching ratio, we obtain the allowed parameter region. We have found that the present constraints still allow a parameter region where both {ital B}{sup 0}-{bar {ital B}}{sup 0} mass splitting {Delta}{ital M}{sub {ital B}} and {epsilon}{sub {ital K}} are {approximately}20{percent} larger than the standard model values. By explicit numerical calculations, we have also found that the complex phase of the {ital B}{sup 0}-{bar {ital B}}{sup 0} mixing matrix element in this model is almost the same as the standard model value within good accuracy in the whole allowed parameter region. It is shown that {Delta}{ital M}{sub {ital B}} and {epsilon}{sub {italmore » K}} can put useful constraints on the supersymmetry{close_quote}s parameter space when the Cabibbo-Kobayashi-Maskawa matrix elements are determined through the measurements of {ital CP} violations in {ital B} decay with future {ital B} factories. {copyright}{ital 1996 The American Physical Society.}« less

We discuss a possible strategy for supersymmetry searches and studies at future linear ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ colliders. We demonstrate their effectiveness by Monte Carlo analyses with full angular correlations under realistic experimental conditions including initial state radiation and beamstrahlung effects. The importance of precision measurements of supersymmetry parameters is emphasized. We demonstrate that the precision on mass measurements can be as good as 1% for leptonic and 3% for hadronic final states. A detailed study on the first superparticle alone gives us an upper bound on the next superparticle. We can also test the basic mass relations assumed in grand unified models or supergravity, such as the gaugino mass relations or the universal scalar mass assumption in a variety of ways. The polarized electron beam plays a crucial role in this study.

Lepton flavor violation in tau and mu processes is studied in the littlest Higgs model with T-parity. We consider various asymmetries defined in polarized tau and mu decays. Correlations among branching ratios and asymmetries are shown in the following lepton flavor violation processes: mu+ --> e+ gamma, mu+ --> e+ e+ e-, mu- A --> e- A (A = Al, Ti, Au and Pb), tau+ --> mu+ gamma, tau+ --> mu+ mu+ mu-, tau+ --> mu+ e+ e-, tau+ --> mu+ P (P = pi0, eta and eta'), tau+ --> mu+ V (V = rho0, omega and phi), tau+ --> e+ gamma, tau+ --> e+ e+ e-, tau+ --> e+ mu+ mu-, tau+ --> e+ P, tau+ --> e+ V, tau+ --> mu+ mu+ e- and tau+ --> e+ e+ mu-. It is shown that large parity asymmetries and time-reversal asymmetries are allowed in mu+ --> e+ e+ e-. For tau lepton flavor violation processes, sizable asymmetries are possible reflecting characteristic chirality structure of lepton flavor violating interactions in this model., 64 pages, 15 figures, v2; Version to be published in PRD

Many extensions of the Standard Model (SM) of particle physics predict the existence of charged Higgs bosons with substantial couplings to SM particles, which would render them observable both directly at the LHC and indirectly at B-factories. For example, the charged Higgs boson couplings to fermions in two doublet Higgs models of type II, are proportional to the ratio of the two Higgs doublet vacuum expectation values (tan(beta)) and fermionic mass factors and could thus be substantial at large tan(beta) and/or for heavy fermions. In this work we perform a model-independent study of the charged Higgs boson couplings at the LHC and at B-factories for large values of tan(beta). We have shown that at high luminosity it is possible to measure the couplings of a charged Higgs boson to the third generation of quarks up to an accuracy of 10%. We further argue that by combining the possible measurements of the LHC and the B-factories, it is possible to perform a universality test of charged Higgs boson couplings to quarks., 20 pages, 7 figures, LaTeX (style changed to PRD format, text expanded, references added)

13 pages, 12 figures, 1 table.-- PACS nrs.: 13.35.Bv; 11.30.Hv.-- ArXiv pre-print available at: http://arxiv.org/abs/0904.0957, We assess the model discriminating power of a combined phenomenological analysis of mu -> e gamma and mu -> e conversion on different target nuclei, including the current hadronic uncertainties. We find that the theoretical uncertainties can be largely reduced by using input from lattice QCD, and do not constitute a limiting factor in discriminating models where one or, at most, two underlying operators (dipole, scalar, vector) provide the dominant source of lepton flavor violation. Our results show that a realistic discrimination among underlying mechanisms requires a measurement of the ratio of conversion rates at the 5% level (two light nuclei) or at the 20% level (one light and one heavy nucleus). We also illustrate these main conclusions in the context of a supersymmetric model., Y. O. is supported in part by the Grant-in-Aid for Science Research, Ministry of Education, Culture, Sports, Science and Technology, Japan, No. 16081211 and by the Grant-in-Aid for Science Research, Japan Society for the Promotion of Science, No. 20244037. P. T. has been supported in part by the theory group at LANL (during her visit), by a grant from the Spanish Ministry of Science and Innovation (No. AP2006-04522), as well as by the EU under Grant No. MRTN-CT-2006-035482 (FLAVIAnet), by MEC (Spain) under Grant No. FPA2007-60323, and by the Spanish Consolider-Ingenio 2010 Programme CPAN (No. CSD2007-00042).

Bilocal operators induced by an axionic wormhole solution are obtained in the case of a massless scalar field. For this purpose, we first show that the calculation of a Green's function for the scalar field on the wormhole background is reduced to a one-dimensional potential-barrier problem. We then evaluate numerically the asymptotic behavior of the Green's function and identify the effective interaction induced by the wormhole.

We study new physics effects on the couplings of weak gauge bosons with the lightest CP-even Higgs boson ($h$), $hZZ$, and the tri-linear coupling of the lightest Higgs boson, $hhh$, at the one loop order, as predicted by the two Higgs doublet model. Those renormalized coupling constants can deviate from the Standard Model (SM) predictions due to two distinct origins; the tree level mixing effect of Higgs bosons and the quantum effect of additional particles in loop diagrams. The latter can be enhanced in the renormalized $hhh$ coupling constant when the additional particles show the non-decoupling property. Therefore, even in the case where the $hZZ$ coupling is close to the SM value, deviation in the $hhh$ coupling from the SM value can become as large as plus 100 percent, while that in the $hZZ$ coupling is at most minus 1 percent level. Such large quantum effect on the Higgs tri-linear coupling is distinguishable from the tree level mixing effect, and is expected to be detectable at a future linear collider., 52 pages, 10 figures, revtex4

The effects of supersymmetric particles on flavor changing neutral current and lepton flavor violating processes are studied in supersymmetric SU(5) grand unified theory with right-handed neutrino supermultiplets. Using input parameters motivated by neutrino oscillation, it is shown that the time-dependent $\mathrm{CP}$ asymmetry of radiative B decay can be as large as 25% when the $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\tau}}\ensuremath{\mu}\ensuremath{\gamma}$ branching ratio becomes close to the present experimental upper bound. We also show that the ${B}_{s}\char21{}{B}_{s}$ mixing can be significantly different from the presently allowed range in the standard model.

$\mu^{+} \to e^{+} \gamma$ and $\mu^{+} \to e^{+}e^{+}e^{-}$ processes are analyzed in detail with polarized muons in supersymmetric grand unified theories. We first present Dalitz plot distribution for $\mu^{+} \to e^{+}e^{+}e^{-}$ decay based on effective Lagrangian with general lepton-flavor-violating couplings and define various P- and T-odd asymmetries. We calculate branching ratios and asymmetries in supersymmetric SU(5) and SO(10) models taking into account complex soft supersymmetry breaking terms. Imposing constraints from experimental bounds on the electron, neutron and atomic electric dipole moments, we find that the T-odd asymmetry for $\mu^{+} \to e^{+}e^{+}e^{-}$ can be 15% in the SU(5) case. P-odd asymmetry with respect to muon polarization for $\mu^{+} \to e^{+} \gamma$ varies from -20% to -100% for the SO(10) model while it is $+100%$ in the SU(5) case. We also show that the P-odd asymmetries in $\mu^{+} \to e^{+}e^{+}e^{-}$ and the ratio of $\mu^{+} \to e^{+}e^{+}e^{-}$ and $\mu^{+} \to e^{+} \gamma$ branching fractions are useful to distinguish different models.

Branching ratio of $\mu \to \e \gamma$ is evaluated in the supersymmetric SU(5) grand unified theory taking account of higher dimensional operators, which reproduce the realistic quark and lepton masses and the mixing parameters. It is shown by numerical calculation that at large $\tan\beta$ the branching ratio is enhanced by a few orders of magnitude since the flavor mixings for both the left- and the right-handed sleptons are induced by the effect of the higher dimensional operators.

A triple vector correlation in the ${\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}{e}^{+}{e}^{\ensuremath{-}}$ decay with polarized muons is investigated as a probe to $\mathrm{CP}$ violating coupling constants in supersymmetric models. A sizable triple correlation can be induced due to a complex phase in the supersymmetric soft-breaking terms in the SU(5) grand unified theory. Correlation with the electric dipole moments of electron and neutron are investigated and it is shown that these quantities give independent information on possible $\mathrm{CP}$ violating sources.

A renormalizable and asymptotically free $\mathrm{O}(N)$ nonlinear $\ensuremath{\sigma}$ model is defined on a $p$-adic field. The effective potential is computed to the leading order in the $\frac{1}{N}$ expansion and it is shown that the mass term for the $\mathrm{O}(N)$ vector field is generated dynamically and the full $\mathrm{O}(N)$ symmetry is realized linearly. Also a discrete scale invariance of the classical action is shown to be violated because of quantum effects.

Quantum cosmology in Kaluza-Klein-type theories is investigated by using the fundamental equation of quantum gravity: the Wheeler-DeWitt equation. The Casimir stress tensor is considered as a prime source of compactification. By imposing the Hartle-Hawking boundary condition, we demonstrate that a fine-tuning of the boundary condition in the quantum regime is necessary, presumably at a moderate level of ${10}^{\mathrm{\ensuremath{-}}3}$, in order to obtain a sufficient inflation of our space.

We describe the calculation of a {beta} function for the {ital p}-adic string {sigma} model in a tachyonic background, and show that the vanishing condition of the {beta} function reproduces the tachyonic field equation obtained from {ital p}-adic amplitude calculations, up to the fifth order in the tachyonic field. By examining this {sigma} model in the presence of a soliton background, we show that a previously obtained soliton solution of the all-order tachyonic field equation follows from the requirement of discrete scale invariance.

The N-point functions for the p-adic version of the bosonic open-string theory are derived and discussed. The cases N=5 and 6 are explicitly calculated, and lead to simple (factorizable) formulas from which the general N case can be formulated.