F. Fucito, A. Lionetto, A. Racioppi, D. Ricci Pacifici
An extension of the Standard Model by at least one extra U(1) gauge symmetry has been investigated by many authors. In this paper we explore the possibility that this extra U(1) is anomalous. One of the possible signatures of this model could be given by the photons produced in the decays of the NLSP into the LSP.
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The most dramatic "Sommerfeld enhancements" of neutral-wino-pair annihilation occur when the wino mass is tuned to near critical values where there is a zero-energy S-wave resonance at the neutral-wino-pair threshold. If the wino mass is larger than the critical value, the resonance is a wino-pair bound state. If the wino mass is near a critical value, low-energy winos can be described by a zero-range effective field theory in which the winos interact nonperturbatively through a contact interaction. The parameters of the zero-range effective field theory can be determined by matching wino scat…
We discuss the phenomenology of supersymmetric models in which supersymmetry breaking terms are induced by the super-Weyl anomaly. Such a scenario is envisioned to arise when supersymmetry breaking takes place in another world, i.e., on another brane. We review the anomaly-mediated framework and study in detail the minimal anomaly-mediated model parametrized by only 3+1 parameters: M_aux, m_0, \tanβ, and sign(μ). The renormalization group equations exhibit a novel "focus point" (as opposed to fixed point) behavior, which allows squark and slepton masses to be far above their usual naturalness …
The $R$-parity violating decays of both Wino chargino and Wino neutralino LSPs are analyzed within the context of the $B-L$ MSSM "heterotic standard model". These LSPs correspond to statistically determined initial soft supersymmetry breaking parameters which, when evolved using the renormalization group equations, lead to an effective theory satisfying all phenomenological requirements; including the observed electroweak vector boson and Higgs masses. The explicit decay channels of these LSPs into standard model particles, the analytic and numerical decay rates and the associated branching ra…
When the GUT relation on gaugino masses is relaxed, the mass and composition of the lightest neutralino are different from those in the GUT case. We discuss its phenomenological implications on the relic abundance of the neutralinos and on superparticle searches. In particular, we focus on the case where the neutral component of Winos dominates the lightest neutralino. It turns out the Wino-LSP is not a candidate for the dark matter.
In the supersymmetric standard model there exist pure gravity contributions to the soft mass parameters which arise via the superconformal anomaly. We consider the low-energy phenomenology with a mass spectrum dominated by the anomaly-induced contributions. In a well-defined minimal model we calculate electroweak symmetry breaking parameters, scalar masses, and the full one-loop splitting of the degenerate Wino states. The most distinctive features are gaugino masses proportional to the corresponding gauge coupling beta-functions, the possibility of a Wino as the lightest supersymmetric partic…
Radiative corrections to the direct detection of the Higgsino-(and Wino-)like neutralino dark matter: Spin-dependent interactions
本文研究MSSM中类Higgsino和类Wino中性ino暗物质的自旋相关直接探测，发现单圈辐射修正可显著增强Z顶点（至多120%）及散射截面（至多50%），对暗物质探测有重要影响。
We compute the present-day Wino dark matter annihilation cross-section including the one-loop radiative corrections together with the fully treated electroweak Sommerfeld effect. We discuss what is the consistent way of incorporating these two corrections simultaneously and why simply using the running coupling constants values at the Wino mass scale is not correct. The results show that up to a few TeV scale the full one-loop computation makes the cross-section smaller up to about 30% with respect to the Sommerfeld enhanced tree level result and are considerably larger than the tree or one-lo…
Almost degenerate bino and wino masses at the weak scale is one of unique features of gauge messenger models. The lightest neutralino is a mixture of bino, wino and higgsino and can produce the correct amount of the dark matter density if it is the lightest supersymmetric particle. Furthermore, as a result of squeezed spectrum of superpartners which is typical for gauge messenger models, various co-annihilation and resonance regions overlap and very often the correct amount of the neutralino relic density is generated as an interplay of several processes. This feature makes the explanation of …
A striking consequence of supersymmetry breaking communicated purely via the superconformal anomaly is that the gaugino masses are proportional to the gauge beta functions. This result, however, is not unique to anomaly mediation. We present examples of ``generalized'' gauge-mediated models with messengers in standard model representations that give nearly identical predictions for the gaugino masses, but positive (mass)^2 for all sleptons. There are remarkable similarities between an anomaly-mediated model with a small additional universal mass added to all scalars and the gauge-mediated mode…
One CP--odd rephase-invariant phase appears in the chargino mass matrix in the minimal Supersymmetric Standard Model. We investigate in detail the phenomenological impacts of the CP-odd complex phase in the production of light charginos in $e^+e^-$ annihilation. The values of the chargino masses and the mixing angles, determining the size of the wino and higgsino components in the chargino wave functions, are so sensitive to the CP-odd phase that the constraints on the supersymmetric parameters based on the conventional assumptions for the parameters are recommended to be re-evaluated includin…
We work out the phenomenology of untagged time-dependent analysis with radiative $D^0$-decays into CP eigenstates, which allows to probe the photon polarization by means of the charm mesons' finite width difference. We show that $D^0 \to ϕγ$ or $D^0 \to \bar K^{0 *} γ$ decays, which are SM-dominated, or SM-like, respectively, together with U-spin allow to obtain chirality-predictions for radiative decay amplitudes. The order of magnitude of wrong-chirality contributions in the SM can be cross-checked with an up-down asymmetry in $D^0 \to \bar K_1^0 (\to \bar K ππ) γ$. We explore the sensitivit…
Lighting up the LHC with Dark Matter
本文提出在 Minimal Supersymmetric Standard Model 中，通过 Bino-Wino 共同湮灭解释暗物质遗留密度和 μ 子磁偶极矩，并建议在 LHC 搜索伴随硬初态辐射喷注的单光子加缺失横向能量信号以探测暗物质。
In framework of the chiral perturbation theory we obtain the phenomenological relations between decay branches of rare radiative kaon to pion and leptons $K^+ \to π^+ l^+ l^-$ and $K^0_S \to π^0 l^+ l^-$ and meson form factors. The comparison of these results with the present day experimental data shows us that the ChPT relations for a charge kaon can determine meson form factors from already measured decay rates at high precision level. However, in the case of the neutral kaon decays $K^0 \to π^0 e^+ e^- (μ^+ μ^-)$ the formfactor data are known to a high precision than data on the differentia…
The neutralino pair annihilation into two photons in our galactic halo gives a robust dark matter signal, since it would give a quasi-monotonic gamma ray. This process is radiatively-induced, and the full-one loop calculation was done previously. However, for the heavy wino-like or Higgsino-like neutralino, the one-loop cross section violates unitarity, therefore the higher-order corrections may be important. We construct a non-relativistic theory for chargino and neutralino two-body states, and estimate all-order QED corrections and two-loop corrections by $Z$ and/or $W$ exchange. We find tha…
Next-to-leading order corrections are an important aspect in the extraction of the Cabibbo- Kobayashi-Maskawa matrix elements $|V_{\text{cb}}|$ and $|V_{\text{ub}}|$ at $B$-factory experiments: virtual and real photons couple to all charged particles of the decay, alter the resulting decay dynamics and enhance the total decay rate. We present a phenomenologically motivated model and a Monte-Carlo implementation to study electromagnetic radiative corrections to differential and total decay rates for semileptonic $B$-meson decays into exclusive pseudoscalar and scalar final states and apply it t…
We study transition form factors for radiative and rare semi-leptonic B-meson decays into light pseudoscalar or vector mesons, combining theoretical constraints and phenomenological information from Lattice QCD, light-cone sum rules, and dispersive bounds. We pay particular attention to form factor parameterisations which are based on the so-called series expansion, and study the related systematic uncertainties on a quantitative level. In this context, we also provide the NLO corrections to the correlation function between two flavour-changing tensor currents, which enters the unitarity const…
In this article we investigate the consequences of radiative flavor violation (RFV) in the Minimal Supersymmetric Standard Model (MSSM). In this framework the small off-diagonal elements of the Cabibbo-Kobayashi-Maskawa (CKM) matrix and the small quark masses of the first two generations are generated from the trilinear supersymmetry-breaking terms. The impact of RFV on flavor-physics observables is studied in detail. We focus on the limiting cases in which the CKM matrix is either generated in the down-sector, i.e. by the soft SUSY-breaking mass insertions delta^dLR_i3 (i=1,2), or in the up-q…
When a small vacuum expectation value of Higgs triplet ($v_Δ$) in the type-II seesaw model is required to explain neutrino oscillation data, a fine-tuning issue occurs on the mass-dimension lepton-number-violation (LNV) scalar coupling. Using the scotogenic approach, we investigate how a small LNV term is arisen through a radiative correction when an $Z_2$-odd vector-like lepton ($X$) and an $Z_2$-odd right-handed Majorana lepton ($N$) are introduced to the type-II seesaw model. Due to the dark matter (DM) direct detection constraints, the available DM candidate is the right-handed Majorana pa…
A phenomenological analysis on various decay processes is performed using an energy-dependent $η-η'$ mixing angle scheme. Special attention is given to the radiative couplings between lowest-lying vector and pseudoscalar mesons. The agreement between our predictions and the experimental values is remarkable. This analysis opens a connection to two-angle fits in the $η-η'$ sector.
Radiative corrections in Lorentz violating (LV) models have already received a lot of attention in the literature in recent years, with many instances where a LV operator in one sector of the Standard Model Extension (SME) generates, via loop corrections, one of the LV coefficients in the photon sector, which is probably the most understood and well constrained part of the SME. In many of these works, however, the now standard notation of the SME is not used, which can obscure the comparison of different results, and their possible phenomenological relevance. In this work, we fill this gap, tr…
The neutral leptonic sector of the Standard Model presumably consists of three neutrinos with non-zero Majorana masses with properties further determined by three mixing angles and three CP-violating phases. We derive the general renormalization group equations for these physical parameters and apply them to study the impact of radiative effects on neutrino physics. In particular, we examine the existing solutions to the solar and atmospheric neutrino problems, derive conclusions on their theoretical naturalness, and show how some of the measured neutrino parameters could be determined by pure…
The shapes of the inclusive photon spectra in the processes $\Jp \to γX$ and $\Up \to γX$ have been analysed using all available experimental data. Relativistic, higher order QCD and gluon mass corrections were taken into account in the fitted functions. Only on including the gluon mass corrections, were consistent and acceptable fits obtained. Values of $0.721^{+0.016}_{-0.068}$ GeV and $1.18^{+0.09}_{-0.29}$ GeV were found for the effective gluon masses (corresponding to Born level diagrams) for the $\Jp$ and $\Up$ respectively. The width ratios $Γ(V \to {\rm hadrons})/Γ(V \to γ+ {\rm hadron…
Radiative neutrino mass generation within supersymmetric (SUSY) construction is studied. The mechanism is considered where the lepton number violation is originating from the soft SUSY breaking terms. This requires MSSM extensions with states around the TeV scale. We present several explicit realizations based on extensions either by MSSM singlet or SU(2)_w triplet states. Besides some novelties of the proposed scenarios, various phenomenological implications are also discussed.
We briefly review the phenomenological implications of the minimal supersymmetric standard model (MSSM) with explicit radiative breaking of CP invariance in the Higgs sector for the LEP2 and Tevatron colliders.
We propose a scheme where the three relevant physics scales related to the supersymmetry, electroweak, and baryon minus lepton (B-L) breakings are linked together and occur at the TeV scale. The phenomenological implications in the Higgs and leptonic sectors are discussed.
We consider a plausible scenario in the Minimal Supersymmetric Standard Model (MSSM) where all the genuine supersymmetric (SUSY) particles are heavier than the electroweak scale. In this situation, indirect searches via their radiative corrections to low energy observables are complementary to direct searches, and they can be crucial if the SUSY masses are at the TeV energy range. We summarize the most relevant heavy SUSY radiative effects in Higgs boson physics and emphasize those that manifest a non-decoupling behaviour. We focus, in particular, on the SUSY-QCD non-decoupling effects in ferm…
Phenomenological expressions are derived for rates of the $Δ(1232)$ radiative and Dalitz decays, $Δ(1232)$ $\to Nγ$ and $Δ(1232)$ $\to Ne^{+}e^{-}$. Earlier calculations of these decays are commented.
Using the operator product expansion (OPE) technique, we study the rare double radiative decay $B\to K γγ$ in the Standard Model (SM) and beyond. We estimate the short-distance (SD) contribution to the decay amplitude in a region of the phase space which is around the point where all decay products have energy $\sim m_b/3$ in the rest frame of the $B$-meson. At lowest order in $1/m_b$, the $B\to K γγ$ matrix element is then expressed in terms of the usual $B\to K$ form factors known from semileptonic rare decays. The integrated SD branching ratio in the SM in the OPE region turns out to be $Δ{…
It has been shown that only certain neutrino mass matrices with texture zeros are compatible with existing data. We discuss the stability of phenomenological consequences of texture zeros under radiative corrections in the type-I see-saw scenario. We show that under certain conditions additional patterns are allowed due to these effects.
Various studies have already considered radiative corrections in Lorentz-violating models unveiling many instances where a minimal or nonminimal operator generates, via loop corrections, a contribution to the photon sector of the Standard-Model Extension. However, an important fraction of this literature does not follow the widely accepted conventions and notations of the Standard-Model Extension, and this obscures the comparison between different calculations as well as possible phenomenological consequences. After reviewing some of these works, we uncover one example where a well defined loo…
The newly observed hidden-charm meson Zc(3900) with quantum numbers J(P) = 1(+) is considered as a hadronic molecule composed of DD*. We give detailed predictions for the decay modes Zc(+) -> J/psi + pi(+) + gamma and Zc(+) -> J/psi + pi(+) + l(+) + l(-) (l = e, mu) in a phenomenological Lagrangian approach.
We study the $Z^\pm(4430)$ meson within a heavy hadron molecule interpretation where the $Z$ is considered as a bound state of a vector $D^\ast(2010)$ and an axial-vector $D_1(2420)$. We give predictions for the strong hidden-charm $Z^\pm(4430) \to π^\pm ψ$ and $π^\pmψ^\prime$ decay widths and also study the radiative $Z^\pm\;(J^P=1^-) \to π^\pmγ$ decay properties in a phenomenological Lagrangian approach. Our findings are qualitatively in line with the experimental observation that the $π^\pmψ^\prime$ transition dominates over the $π^\pmψ$ decay mode despite a smaller phase space. The width f…
We apply a phenomenological Lagrangian approach to the radiative decay Y(4260) -> X(3872) + gamma. The Y(4260) and X(3872) resonances are considered as composite states containing both molecular hadronic and charmonium components. Having a leading molecular component in the X(3872) and a sole molecular configuration for the Y(4260) results in a prediction compatible with present data.
We study the radiative $ϕ\to K^0\bar{K}^0γ$ decay within a phenomenological framework by considering the contributions of the $f_{0}(980)$ and $a_{0}(980)$ scalar resonances. We calculate the branching ratio $B(ϕ\to K^0\bar{K}^0γ)$ by employing the coupling constants $g_{f_0K^{+}K^{-}}$ and $g_{a_0K^{+}K^{-}}$ as determined by different experimental groups.
Weak radiative hyperon decays are considered in the framework of a quark model. The phenomenological model includes 1-quark transitions with the effective $sdγ$-vertex and 2-quark ones with the W-exchange $s+u\to u+d+γ$ and turns out to describe well the data and gives predictions for asymmetry of the decays $Λ\to n+γ$ and $Ξ^-\to Σ^- +γ$.
Using a bound-state model of weakly bound gluons for glueballs made of two gluons and a natural generalization of the perturbative QCD formalism for exclusive hadronic processes, we present results for glueball production in radiative J/psi, Upsilon decays into several possible glueball states, including L \not= 0 ones. We perform a detailed phenomenological analysis, presenting results for the more favored experimental candidates and for decay angular distributions.
We study the radiative $ρ^0\to π^+π^-γ$ and $ρ^0\to π^0π^0γ$ decays and we calculate their branching ratios using a phenomenological approach by adding to the amplitude calculated within the framework of chiral perturbation theory and vector meson dominance the amplitude of $σ$-meson intermediate state. Our results for the branching ratios are in good agreement with the experimental values.
We apply the QCD factorization approach to exclusive, radiative B meson decays in the region of small invariant photon mass. We calculate factorizable and non-factorizable corrections to leading order in the heavy quark mass expansion and next-to-leading order in the strong coupling constant. Phenomenological consequences for the B -> K* gamma decay rate and the B -> K* ell+ ell- forward-backward asymmetry are discussed.
We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two body B-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approaches. PQCD results are compatible with present experimantal data for the charmless B-meson decays. We predict the possibility of large direct CP asymmetry in $B^0 \to π^{+}π^{-}$ $(23\pm7 %)$ and $B^0\to K^{+}π^{-}$ $(-17\pm5%)$. We also investigate the Branching ratios, CP asymmetry and isopsin symmetry breaking in radiative $B \to (K^*/ρ) γ$ decays.
We study the effect of scalar-isoscalar $f_{0}(980)$ meson in the mechanism of the radiative $ϕ\to π^{+}π^{-}γ$ decay. A phenomenological approach is used to study this decay by considering the contributions of $σ$-meson, $ρ$-meson and $f_{0}(980)$-meson. The interference effects between different contributions are analyzed and the branching ratio for this decay is calculated. We observe that $f_0$ meson contribution is much larger than the contributions of the other terms.
We study the generation of the GUT scale through radiative corrections in the context of a R-symmetric "flipped" SU(5) X U(1)_X model. A negative mass squared term for the GUT Higgs fields develops due to radiative effects along a flat direction at a superheavy energy scale. The R-symmetry is essential in maintaining triplet-doublet splitting and F-flatness in the presence of non-renormalizable terms. The model displays radiative electroweak symmetry breaking and satisfies all relevant phenomenological constraints.
Radiative Mass Mechanism: Addressing the Flavour Hierarchy and Strong CP Puzzle
本文提出基于左右对称模型的辐射质量机制，通过味非普适规范对称性生成费米子质量层级，并利用宇称不变性解决强CP问题，预测新物理尺度约10^8 GeV。
We present a simple model in which CP symmetry is spontaneously broken only after the radiative corrections are taken into account. The model includes two Higgs-boson doublets and two right-handed singlet neutrinos which induce the necessary non-hermitian interaction. To evade the Georgi-Pais theorem, some fine-tuning of coupling constants is necessary. However, we show that such fine-tuning is natural in the technical sense as it is protected by symmetry. Some phenomenological consequences are also discussed.
We derive a new factorization relation for the semileptonic radiative decay B -> π\ell νγin the kinematical region of a slow pion p_π~ Λand an energetic photon E_γ>> Λ, working at leading order in Λ/m_b. In the limit of a soft pion, the nonperturbative matrix element appearing in this relation can be computed using chiral perturbation theory. We present a phenomenological study of this decay, which may be important for a precise determination of the exclusive nonradiative decay.
If the minimal standard model of quarks and leptons is extended to include just a righthanded partner to nu_tau, then the quantum number B-3L_tau can be added as a gauge symmetry without the appearance of anomalies. A suitable extension of the scalar sector allows one neutrino to have a seesaw mass, and the other two to have radiative masses, with acceptable phenomenological values for neutrino oscillations. The B-3L_tau gauge boson may be light and be observable through its decay into tau^+ tau^-.
Properties of X(3872) are studied by regarding it as a $DD^{\ast}$ hadronic molecule with $J^{PC} = 2^{-+}$ in the phenomenological Lagrangian approach. We find that our model with about 97.6% isospin zero component explains the existing data nicely, for example, the ratio $\mathcal{B}(X(3872) \to J/ψπ^+π^-π^0)/\mathcal{B}(X(3872) \to J/ψπ^+π^-)$. We predict the partial widths of the radiative decays of $X(3872) \to γJ/ψ$, $γψ(2S) $ and the strong decays of $X(3872) \to J/ψπ^+ π^-$, $J/ψπ^+π^-π^0$ as well as $X(3872) \to χ_{cJ}π^0$. Our analysis shows that the measurement of the ratio $\mathca…
Using the results of the GRAAL collaboration on the ηphotoproduction from the neutron target, we attempt to extract the partial radiative width of the possible new nucleon resonance N^*(1675). The obtained estimates support this resonance to be a very attractive candidate for the non-strange member of the exotic antidecuplet of baryons -- a partner of the Θ^+ pentaquark. Our phenomenological value for the transition magnetic moment μ(n^* n), appears to be in good agreement with predictions of the Chiral Quark Soliton Model.
We study the photon spectrum in the radiative decays of the charmonium $\frac{1}Γ\frac{dΓ(J/ψ\rightarrowγgg)}{dz}$ as an excellent scene for hunting the exotic mesons (hybrids $q\bar{q}g$ and glueballs $gg$) and an ideal frame for the theoretical and phenomenological investigations of the gluon nature in IR, by subtle estimation of its non-zero effective mass which seems required in Quark-Gluon Constituent Model (QGCM) for identifying the nature of these exotic species.
The radiative decays of the B mesons may have a significant contribution from the transition b -> s J/psi followed by the J/psi-photon conversion. The size of this contribution is re-analysed in the light of a phenomenological model for the weak bsJ/psi vertex, and a modified J/psi-photon interaction that is manifestly gauge invariant. Predictions for both inclusive and exclusive cases are obtained, but large uncertainties still remain.
We investigate the spectrum and decay rates of low lying charmonium states within the framework of the non relativistic quark model by employing a Coulomb like potential from the perturbative one gluon exchange and the linear confining potential along with the potential derived from instanton vacuum to account for the hyperfine mass splitting of charmonium states in variational approach. We predict radiative E1, M1, two-photon, leptonic and two-gluon decay rates of low lying charmonium states. An overall agreement is obtained with the experimental masses and decay widths.
A gauge $U(1)$ family symmetry is proposed, spanning the quarks and leptons as well as particles of the dark sector. The breaking of $U(1)$ to $Z_2$ divides the two sectors and generates one-loop radiative masses for the first two families of quarks and leptons, as well as all three neutrinos. We study the phenomenological implications of this new connection between family symmetry and dark matter. In particular, a scalar or pseudoscalar particle associated with this $U(1)$ breaking may be identified with the 750 GeV diphoton resonance recently observed at the Large Hadron Collider (LHC).
We study the radiative leptonic $B_c\to γ\ell\barν$ decays in the nonrelativistic QCD effective field theory, and consider a fast-moving photon. As a result the interactions with the heavy quarks can be integrated out, and thus we arrive at a factorization formula for the decay amplitude. We calculate not only the relevant short-distance coefficients at leading order and next-to-leading order in $α_s$, but also the nonrelativistic corrections at the order $|\bold{v}|^2$ in our analysis. We find out that the QCD corrections can sizably decrease the branching ratio and thus is of great importanc…
The electroweak structures of the FCNC-induced rare and radiative K decays are presented. While the former decays are sensitive to short-distance physics and offer exceptional probes for new physics, the latter are dominated by long-distance physics. Even so, they should not be set aside since they constitute essential ingredients to control the hadronic uncertainties occurring for the rare decays. This is illustrated by systematically reviewing the phenomenological strategies currently in use to cleanly predict the rare K decay rates in the Standard Model.
The weak form factor for $B\to K_{1B}$ where $K_{1B}$ is the $^1P_1$ state is calculated in the light-cone sum rules (LCSR). Combining the quark model result for the form factor of $B\to K_{1A}$ with $K_{1A}$ being the $^3P_1$ state, we have larger values for $B\to K_1$ form factors than the previous LCSR results. The increased form factors reduce the discrepancy between theory and the experimental data for $B\to K_1 γ$. Some phenomenological meanings are also discussed.
For type I seesaw and in the basis where the charged lepton and heavy right-handed neutrino mass matrices are real and diagonal, four has been shown to be the maximum number of zeros allowed in the neutrino Yukawa coupling matrix $Y_ν$. These four zero textures have been classified into two distinct categories. We investigate certain phenomenological consequences of these textures within a supersymmetric framework. This is done by using conditions implied on elements of the neutrino Majorana mass matrix for textures of each category in $Y_ν$. These conditions turn out to be stable under radiat…
Recently, the LHCb Collaboration performed first search for the rare radiative $Ξ_{b}^{-}\rightarrow Ξ^{-}γ$ decay and put an upper limit, ${\cal B}(Ξ_{b}^{-}\to Ξ^{-}γ) < 1.3 \times 10^{-4}$, on its branching ratio. The measurement agrees well with existing theory prediction using SU(3) flavor symmetry method, but shows a slight tension with the previous prediction from light-cone sum rules. Inspired by this, we investigate this decay as well as other radiative decays of $Ξ_b^{0(-)}(Ξ^{'-}_{b})$ to $Ξ^{0(-)}$ and $Σ^{0(-)}$ baryons using the form factors calculated from light-cone QCD sum rul…
We discuss a model-independent framework for the analysis of the radiative B-meson decays B -> K* gamma and B -> rho gamma based on the heavy-quark limit of QCD. We present a factorization formula for the treatment of B -> V gamma matrix elements involving charm (or up-quark) loops, which contribute at leading power in Lambda_QCD/m_B to the decay amplitude. Annihilation topologies are power suppressed, but still calculable in some cases. The framework of QCD factorization is necessary to compute exclusive b -> s(d) gamma decays systematically beyond the leading logarithmic approximation. Resul…
The investigation of weak bosons $V$ ($V=\mathrm{W}^{\pm}$, $\mathrm{Z}$) produced with or without associated hard QCD jets will be of great phenomenological interest at the LHC. Owing to the large cross sections and the clean decay signatures of the vector bosons, weak-boson production can be used to monitor and calibrate the luminosity of the collider, to constrain the PDFs, or to calibrate the detector. Moreover, the $Z$+jet(s) final state constitutes an important background to a large variety of signatures of physics beyond the Standard Model. To match the excellent experimental accuracy t…
Two aspects of isospin breaking in the decay $K^\pm \to π^0 π^0 e^\pm \stackrel{_{(-)}}{ν_e}$ are studied and discussed. The first addresses the possible influence of the phenomenological description of the unitarity cusp on the extraction of the normalization of the form factor from data. Using the scalar form factor of the pion as a theoretical laboratory, we find that this determination is robust under variations of the phenomenological parameterizations of the form factor. The second aspect concerns the issue of radiative corrections. We compute the radiative corrections to the total decay…
We perform a phenomenological study of the scalar sector of two models that generate neutrino mass at the three-loop level and contain viable dark matter candidates. Both models contain a charged singlet scalar and a larger scalar multiplet (triplet or quintuplet). We investigate the effect of the extra scalars on the Higgs mass and analyze the modifications to the triple Higgs coupling. The new scalars can give observable changes to the Higgs decay channel $h\rightarrowγγ$ and, furthermore, we find that the electroweak phase transition becomes strongly first-order in large regions of paramete…
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