arXiv subjects

D. Wyler

Publications and source records attributed to D. Wyler.

At least 19 recordsLinked to original sources

arXiv2015

Oscillations of the $^7$Be solar neutrinos inside the Earth

We explore in detail oscillations of the solar $^7$Be neutrinos in the matter of the Earth. The depth of oscillations is about $(0.1 - 0.2)\%$ and the length $\approx 30$ km. The period of the oscillatory modulations in the energy scale is comparable with the width of the line determined by the temperature in the center of the Sun. The latter means that depending on the length of trajectory (nadir angle) one obtains different degree of averaging of oscillations. Exploring these oscillations it is possible to measure the width of the $^7$Be line and therefore the temperature of the Sun, determine precisely $Δm^2_{21}$, perform tomography of the Earth, in particular, measure the deviation of its form from sphere, and detect small structures. Studies of the Be neutrinos open up a possibility to test quantum mechanics of neutrino oscillations and search for the sterile neutrinos. Accuracy of these measurements with future scintillator (or scintillator uploaded) detectors of the $\sim 100$ kton mass scale is estimated.

hep-ph↗

arXiv2011

Electromagnetic Logarithms in B -> X_s l+ l-

The B -> X_s l+ l- decay rate is known at the next-to-next-to-leading order in QCD. It is proportional to alpha_em (mu)^2 and has a +- 4% scale uncertainty before including the O(alpha_em log(M_W^2/m_b^2)) electromagnetic corrections. We evaluate these corrections and confirm the earlier findings of Bobeth et al. >. Furthermore, we complete the calculation of logarithmically enhanced electromagnetic effects by including also QED corrections to the matrix elements of four-fermion operators. Such corrections contain a collinear logarithm log(m_b^2/m_l^2) that survives integration over the low dilepton invariant mass region 1 GeV^2 < q^2 < 6 GeV^2 and enhances the integrated decay rate in this domain. For the low-q^2 integrated branching ratio in the muonic case, we find B (B -> X_s mu^+mu^-) = (1.59 +- 0.11) 10^(-6), where the error includes the parametric and perturbative uncertainties only. For B (B -> X_s e^+e^-), in the current BaBar and Belle setups, the logarithm of the lepton mass gets replaced by angular cut parameters and the integrated branching ratio for the electrons is expected to be close to that for the muons.

hep-ph↗

arXiv2011

A Little Higgs Model with Exact Dark Matter Parity

Based on a recent idea by Krohn and Yavin, we construct a little Higgs model with an internal parity that is not broken by anomalous Wess-Zumino-Witten terms. The model is a modification of the "minimal moose" models by Arkani-Hamed et al. and Cheng and Low. The new parity prevents large corrections to oblique electroweak parameters and leads to a viable dark matter candidate. It is shown how the complete Standard Model particle content, including quarks and leptons together with their Yukawa couplings, can be implemented. Successful electroweak symmetry breaking and consistency with electroweak precision constraints is achieved for natural paramters choices. A rich spectrum of new particles is predicted at the TeV scale, some of which have sizable production cross sections and striking decay signatures at the LHC.

hep-ph↗

arXiv2009

Phenomenology of the Little Higgs model with X-Parity

In the popular littlest Higgs model, T-parity can be broken by Wess-Zumino-Witten (WZW) terms induced by a strongly coupled UV completion. On the other hand, certain models with multiple scalar multiplets (called moose models) permit the implementation of an exchange symmetry (X-parity) such that it is not broken by the WZW terms. Here we present a concrete and realistic construction of such a model. The little Higgs model with X-Parity is a concrete and realistic implementation of this idea. In this contribution, the properties of the model are reviewed and the collider phenomenology is discussed in some detail. We also present new results on the decay properties and LHC signatures of the light triplet scalars that are predicted by this model.

hep-ph↗

arXiv2008

Consequences of T-parity breaking in the Littlest Higgs model

In this paper we consider the effects of the T-parity violating anomalous Wess-Zumino-Witten-Term in the Littlest Higgs model. Apart from tree level processes, the loop induced decays of the heavy mirror particles into light standard model fermions lead to a new and rich phenomenology in particular at breaking scales f below 1 TeV. Various processes are calculated and their signatures at present and future colliders are discussed. As a byproduct we find an alternative production mechanism for the Higgs boson.

hep-ph↗

arXiv2007

Astro Unparticle Physics

We investigate the effects of all flavor blind CP-conserving unparticle operators on 5th force experiments, stellar cooling, supernova explosions and compare the limits with each other and with those obtainable from collider experiments. In general, astrophysical bounds are considerably stronger, however they depend strongly on the dimension d_U of the unparticle operator. While for d_U=1, 5th force experiments yield exceedingly strong bounds, the bounds from stellar and supernova cooling are more comparable for d_U=2, with stellar cooling being most restrictive. Bounds on vectorial unparticle couplings are generally stronger than those on scalar ones.

hep-ph↗

arXiv2006

Phenomenology of Mirror Fermions in the Littlest Higgs Model with T-Parity

Little Higgs models are an interesting alternative to explain electroweak symmetry breaking without fine-tuning. Supplemented with a discrete symmetry (T-parity) constraints from electroweak precision data are naturally evaded and also a viable dark matter candidate is obtained. T-parity implies the existence of new (mirror) fermions in addition to the heavy gauge bosons of the little Higgs models. In this paper we consider the effects of the mirror fermions on the phenomenology of the littlest Higgs model with T-parity at the LHC. We study the most promising production channels and decay chains for the new particles. We find that the mirror fermions have a large impact on the magnitude of signal rates and on the new physics signatures. Realistic background estimates are given.

hep-ph↗

arXiv2005

The Discovery Potential of a Super B Factory

The Proceedings of the 2003 SLAC Workshops on flavor physics with a high luminosity asymmetric e+e- collider. The sensitivity of flavor physics to physics beyond the Standard Model is addressed in detail, in the context of the improvement of experimental measurements and theoretical calculations.

hep-ph↗

arXiv2004

Reducing the Error on alpha in B-> pi pi, rho rho, rho pi

Theoretical errors in the extraction of alpha from B -> pi^+ pi^-, rho^+ rho^-, rho pi decays are usually given in terms of upper bounds on alpha_eff-alpha obtained from isospin or from SU(3) relations, where alpha_eff is measured through CP asymmetries. We show that mild assumptions about magnitudes and strong phases of penguin and tree amplitudes (|P/T| < 1 and |delta| < pi/2) in B -> pi pi and B -> rho rho, imply alpha_eff > alpha, thus reducing by a factor two the error in alpha. Similarly, the assumptions |p_+-/t_+-| < 1, |δ_-| < pi/2 <|δ_+| in B -> rho pi lead to a cancellation between two terms in alpha_eff-alpha. Current data support these conditions.

hep-ph↗

arXiv2004

A precise analytical description of the Earth matter effect on oscillations of low energy neutrinos

We present a formalism for the matter effects in the Earth on low energy neutrino fluxes which is both accurate and has all advantages of a full analytic treatment. The oscillation probabilities are calculated up to second order term in $ε(x) \equiv 2V(x)E/Δm^2$ where $V(x)$ is the neutrino potential at position $x$. We show the absence of large undamped phases which makes the expansion in $ε$ well behaved. An improved expansion is presented in terms of the variation of $V(x)$ around a suitable mean value which allows to treat energies up to those relevant for Supernova neutrinos. We discuss also the case of three-neutrino mixing.

hep-ph↗

arXiv2004

Spin Asymmetries in Squark and Gluino Production at Polarized Hadron Colliders

We study the production cross sections for squarks and gluinos in collision of longitudinally polarized hadrons. The corresponding polarized partonic cross sections are computed in leading order supersymmetric QCD. The resulting asymmetries are evaluated for the polarized proton collider RHIC, as well as for hypothetical polarized options of the Tevatron and the LHC. These asymmetries turn out to be sizable over a wide range of supersymmetric particle masses, thus potentially opening a window to detailed sparticle spectroscopy at future polarized hadron colliders.

hep-ph↗

arXiv2003

Effect of supersymmetric phases on lepton dipole moments and rare lepton decays

We study the effect of SUSY phases on rare decays of leptons and on their magnetic and electric dipole moments. We consider the most general mass matrices for sleptons within the MSSM including left--right mixing, flavour mixing and complex phases. We show that the phases also affect CP even observables. Moreover, we demonstrate that contrary to common belief the phase of mu can be large even for slepton masses as small as 200 GeV provided the lepton flavour violating parameters are complex.

hep-ph↗

arXiv2001

CP Violation, Neutrino Mixing and the Baryon Asymmetry

We study neutrino masses and mixings based on the simplest SO(10) mass relations and the seesaw mechanism. We find that the requirement of large neutrino mixings determines the relative magnitude of the heavy Majorana neutrino masses in terms of the known quark mass hierarchy. This leads to specific predictions for the structure of the neutrino mixing matrix, the light neutrino masses, CP violation in neutrino oscillations, neutrinoless double b-decay and the baryon asymmetry.

hep-ph↗

arXiv2001

Complex flavour couplings in supersymmetry and unexpected CP-violation in the decay B -> phi K

Complex flavour couplings (off-diagonal mass terms) in the squark sector of supersymmetric theories may drastically alter both the rate and the CP-violating asymmetry of certain B-meson decays. We consider the effects of couplings that induce b -> s transitions and lead to final state with strangeness one. We investigate the bounds that must be satisfied by the new terms and explore the possible implications on direct and mixing induced asymmetries in the charged and neutral B -> J/Psi K and B -> phi K decays.

hep-ph↗

arXiv2001

Dynamical Instabilities of Brane World Models

We show the instability of two self-tuning brane world models with gauge invariant linear perturbation theory. This general method confirms a known instability of the original model with vanishing bulk potential. We also show the dynamical instability of a recently proposed self-tuning "smooth" brane model and its limit, the Randall-Sundrum model. Astonishingly, we also find instability under purely gravitational perturbations.

hep-th↗

arXiv2000

$c\to uγ$ in the minimal supersymmetric standard model

The minimal supersymmetric standard model (MSSM) with universal soft breaking terms has a negligible effect on the rare $c\to uγ$ decay rate. We therefore study a general model with non-universal soft breaking terms constrained by vacuum stability and the experimental upper bound on the mass difference of the neutral charm mesons. It turns out that gluino exchange can enhance the standard model rate by up to two orders of magnitudes; in contrast, the contributions from charginos and neutralinos remain at least an order of magnitude below the QCD corrected standard model rate.

hep-ph↗

arXiv2000

Gluino Contribution to Radiative B Decays: Organization of QCD Corrections and Leading Order Results

The gluino-induced contributions to the decay b-> s gamma are investigated in supersymmetric frameworks with generic sources of flavour violation. It is shown that, when QCD corrections are taken into account, the relevant operator basis of the Standard Model effective Hamiltonian gets enlarged to contain: i) magnetic and chromomagnetic operators with a factor of alpha_s and weighted by a quark mass m_b or m_c; ii) magnetic and chromomagnetic operators of lower dimensionality, also containing alpha_s; iii) four-quark operators weighted by a factor alpha_s^2. Numerical results are given, showing the effects of the leading order QCD corrections on the inclusive branching ratio for b-> s gamma. Constraints on supersymmetric sources of flavour violation are derived.

hep-ph↗

arXiv2000

A Possible Arena for Searching New Physics - the $Γ(D^0 \to ρ^0 γ)/Γ(D^0 \to ωγ)$ Ratio

We propose to investigate flavour changing neutral currents in the $c \to u γ$ transition through the measurement of the difference between $Γ(D^0 \to ρ^0 γ)$ and $Γ(D^0 \to ωγ)$. This is based on the observation that $D^0 \to (d \bar d) γ$ is due to long distance physics while $D^0 \to (u \bar u) γ$ arises from the $c \to u γ$ transition. The effect of $ρ- ω$ mixing is included. A difference in the decay widths of more than about 30% would be indicative of new physics.

hep-ph↗