Non-minimal Flavour Violation Research Articles

Frugal U(1)X models with non-minimal flavor violation for b → sℓℓ anomalies and neutrino mixing

We analyze the class of models with an extra U(1)X gauge symmetry that can account for the b → sℓℓ anomalies by modifying the Wilson coefficients C9e and C9μ of the operators {O}_{9mathrm{ell}}equiv left(overline{b}{gamma}_{mu }{P}_Lsright)left(overline{mathrm{ell}}{gamma}^{mu}mathrm{ell}right) from their standard model values. At the same time, these models generate appropriate quark mixing, and give rise to neutrino mixing via the Type-I seesaw mechanism. Apart from the gauge boson Z′, these frugal models only have three right-handed neutrinos for the seesaw mechanism, an additional SU(2)L scalar doublet for quark mixing, and a SM-singlet scalar that breaks the U(1)X symmetry. This set-up identifies a class of leptonic symmetries, and necessitates non-zero but equal charges for the first two quark generations. If the quark mixing beyond the standard model were CKM-like, all these symmetries would be ruled out by the latest flavor constraints on Wilson coefficients and collider constraints on Z′ parameters. However, we identify a single-parameter source of non-minimal flavor violation that allows a wider class of U(1)X symmetries to be compatible with all data. We show that the viable leptonic symmetries have to be of the form Le± 3Lμ− Lτ or Le− 3Lμ + Lτ, and determine the (MZ′, gZ′) parameter space that may be probed by the high-luminosity data at the LHC.

Bs(d) \u2212 overline{B} s(d) mixing and Bs \u2192 \u03bc+\u03bc\u2212 decay in the NMSSM with the Flavour Expansion Theorem

In this paper, motivated by the observation that the Standard Model predictions are now above the experimental data for the mass difference ΔMs(d), we perform a detailed study of Bs(d) − overline{B} s(d) mixing and Bs → μ+μ− decay in the ℤ3-invariant NMSSM with non-minimal flavour violation, using the recently developed procedure based on the Flavour Expansion Theorem, with which one can perform a purely algebraic mass-insertion expansion of an amplitude written in the mass eigenstate basis without performing any diagrammatic calculations in the interaction/flavour basis. Specifically, we consider the finite orders of mass insertions for neutralinos but the general orders for squarks and charginos, under two sets of assumptions for the squark flavour structures (i.e., while the flavour-conserving off-diagonal element δ33LR is kept in both of these two sectors, only the flavour-violating off-diagonal elements δ23LL and δi3RR (i = 1, 2) are kept in the LL and RR sectors, respectively). Our analytic results are then expressed directly in terms of the initial Lagrangian parameters in the interaction/flavour basis, making it easy to impose the experimental bounds on them. It is found numerically that the NMSSM effects with the above two assumptions for the squark flavour structures can accommodate the observed deviation for ΔMs(d), while complying with the experimental constraints from the branching ratios of Bs → μ+μ− and B → Xsγ decays.

Non-minimal flavour violation in A4 \xd7 SU(5) SUSY GUTs with smuon assisted dark matter

We study CP-conserving non-minimal flavour violation in A4 × SU(5) inspired Supersymmetric Grand Unified Theories (GUTs), focussing on the regions of parameter space where dark matter is successfully accommodated due to a light right-handed smuon a few GeV heavier than the lightest neutralino. In this region of parameter space we find that some of the flavour-violating parameters are constrained by the requirement of the dark matter relic density, due to the delicate interplay between the smuon and neutralino masses. By scanning over GUT scale flavour violating parameters, constrained by low-energy quark and lepton flavour violating observables, we find a striking difference in the results in which individual parameters are varied to those where multiple parameters are varied simultaneously, where the latter relaxes the constraints on flavour violating parameters due to cancellations and/or correlations. Since charged lepton-flavour violation provides the strongest constraints within a GUT framework, due to relations between quark and lepton flavour violation, we examine in detail a prominent correlation between some of the flavour violating parameters at the GUT scale consistent with the stringent lepton flavour violating process μ → eγ. We also examine the relation between GUT scale and low scale flavour violating parameters, for both quarks and leptons, and show how the usual expectations may be violated due to the correlations when multiple parameters are varied simultaneously.

General squark flavour mixing: constraints, phenomenology and benchmarks

We present an extensive study of non-minimal flavour violation in the squark sector in the framework of the Minimal Supersymmetric Standard Model. We investigate the effects of multiple non-vanishing flavour-violating elements in the squark mass matrices by means of a Markov Chain Monte Carlo scanning technique and identify parameter combinations that are favoured by both current data and theoretical constraints. We then detail the resulting distributions of the flavour-conserving and flavour-violating model parameters. Based on this analysis, we propose a set of benchmark scenarios relevant for future studies of non-minimal flavour violation in the Minimal Supersymmetric Standard Model.

Radiative generation of neutrino mixing: Degenerate masses and threshold corrections

Degenerate neutrino masses are excluded by experiment. The experimentally measured mass squared differences together with the yet undetermined absolute neutrino mass scale allow for a quasi-degenerate mass spectrum. For the lightest neutrino mass larger than roughly 0.1 eV, we analyse the influence of threshold corrections at the electroweak scale. We show that typical one-loop corrections can generate the observed neutrino mixing as well as the mass differences starting from exactly degenerate masses at the tree-level. Those threshold corrections have to be explicitly flavour violating. Flavour diagonal, non-universal corrections are not sufficient to simultaneously generate the correct mixing and the mass differences. We apply the new insights to an extension of the Minimal Supersymmetric Standard Model with non-minimal flavour violation in the soft breaking terms and discuss the low-energy threshold corrections to the light neutrino mass matrix in that model.

Phenomenology of anomaly-mediated supersymmetry-breaking scenarios with nonminimal flavor violation

In minimal anomaly-mediated supersymmetry-breaking models, tachyonic sleptons are avoided by introducing a common scalar mass similar to the one introduced in minimal supergravity. This may lead to nonminimal flavor-violating interactions, e.g., in the squark sector. In this paper, we analyze the viable anomaly-mediated supersymmetry-breaking parameter space in the light of the latest limits on low-energy observables and LHC searches, complete our analytical calculations of flavor-violating supersymmetric particle production at hadron colliders with those related to gluino production, and study the phenomenological consequences of nonminimal flavor violation in anomaly-mediated supersymmetry-breaking scenarios at the LHC. Related cosmological aspects are also briefly discussed.

Higgs boson masses and B-physics constraints in Non-Minimal Flavor Violating SUSY scenarios

We present one-loop corrections to the Higgs boson masses in the MSSM with Non-Minimal Flavor Violation. The flavor violation is generated from the hypothesis of general flavor mixing in the squark mass matrices, and these are parametrized by a complete set of $\delta_{ij}^{XY}$ (X, Y = L, R; i, j = t, c, u or b, s, d). We calculate the corrections to the Higgs masses in terms of these $\delta_{ij}^{XY}$ taking into account all relevant restrictions from B-physics data. This includes constraints from BR(B → X s γ), BR(B s → μ + μ −) and ΔM Bs . After taking into account these constraints we find sizable corrections to the Higgs boson masses, in the case of the lightest MSSM Higgs boson mass exceeding tens of GeV. These corrections are found mainly for the low tan β case. In the case of a Higgs boson mass measurement these corrections might be used to set further constraints on $\delta_{ij}^{XY}$ .

Impact of squark flavor violation on neutralino dark matter

We discuss the possibility of new sources of flavour violation in the squark sector of supersymmetric models in the context of the dark matter relic density. We show that the corresponding non-minimal flavour violation terms in the squark mass matrices can have an important impact on the thermally averaged (co)annihilation cross section of the neutralino, and in consequence can modify its predicted relic density. We discuss in detail the relevant effects and present a numerical study of neutralino annihilation and coannihilation in this context. We also comment on the LHC phenomenology of the corresponding scenarios.

Signatures of bosonic squark decays in non-minimally flavour-violating supersymmetry

We investigate couplings of squarks to gauge and Higgs-bosons within the framework of non-minimal flavour violation in the Minimal Supersymmetric Standard Model. Introducing non-diagonal elements in the mass matrices of squarks, we first study their impact on the self-energies and physical mass eigenvalues of squarks. We then present an extensive analysis of bosonic squark decays for variations of the flavour-violating parameters around the two benchmark scenarios SPS1a' and SPS1b. Signatures, that would be characteristic for a non-minimal flavour structure in the squark sector, can be found in wide regions of the parameter space.

New physics contribution toB→Kπdecays in soft collinear effective theory

We analyze the $5\sigma$ difference between the CP asymmetries of the $B^0 \to K^+ \pi^-$ and $B^+ \to K^+ \pi^0$ decays within the Soft Collinear Effective Theory. We find that in the Standard Model, such a big difference cannot be achieved. We classify then the requirements for the possible New Physics models, which can be responsible for the experimental results. As an example of a New Physics model we study minimal supersymmetric models, and find that the measured asymmetry can be obtained with non-minimal flavor violation.

Non-minimal flavour violation, light pseudoscalar Higgs and evidence for SUSY in [formula omitted] decays

We summarise a detailed MSSM analysis of the dominant contributions to the B s 0 → μ + μ − decay rate assuming non-minimal flavour violation, light Higgs sector and large tan β . We investigate the case when the LHC finds light MSSM higgs states and, at the same time, the B s 0 → μ + μ − decay rate above the Standard Model rate, i.e., the scenario which would be ruled out under the assumption of minimal flavour violation.

Rare meson decays into very light neutralinos

We investigate the bounds on the mass of the lightest neutralino from rare meson decays within the minimal supersymmetric standard model (MSSM) with and without minimal flavor violation. We present explicit formulas for the two-body decays of mesons into light neutralinos and perform the first complete calculation of the loop-induced decays of kaons to pions and light neutralinos and $B$ mesons to kaons and light neutralinos. We find that the supersymmetric branching ratios are strongly suppressed within the MSSM with minimal flavor violation, and that no bounds on the neutralino mass can be inferred from experimental data, i.e., a massless neutralino is allowed. The branching ratios for kaon and $B$ meson decays into light neutralinos may, however, be enhanced when one allows for nonminimal flavor violation. We find new constraints on the MSSM parameter space for such scenarios and discuss prospects for future kaon and $B$ meson experiments. Finally, we comment on the search for light neutralinos in monojet signatures at the Tevatron and at the LHC.

FeynHiggs: A program for the calculation of MSSM Higgs-boson observables – Version 2.6.5

FeynHiggs is a Fortran code for the calculation of physical observables in the field of high-energy physics. FeynHiggs calculates various observables in the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) for real or complex parameters. These observables comprise Higgs-boson masses, mixing angles, couplings, Tevatron/LHC production cross-sections, branching ratios, as well as some additional observables such as Δ ρ, M W , the effective leptonic weak mixing angle, ( g − 2 ) μ , BR( b → s γ ), electric dipole moments. New version program summary Program title: FeynHiggs v2.6.5 Catalogue identifier: ADKT_v2_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADKT_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL No. of lines in distributed program, including test data, etc.: 156 455 No. of bytes in distributed program, including test data, etc.: 1 058 758 Distribution format: tar.gz Programming language: Fortran 77, C, Mathematica Computer: Intel/AMD, PowerPC, Alpha Operating system: Linux, Windows (Cygwin), Mac OS, Tru64 Unix RAM: insignificant (typically a few MB) Classification: 11.5 Catalogue identifier of previous version: ADKT_v1_0 Journal reference of previous version: Comput. Phys. Comm. 124 (2000) 76 Does the new version supersede the previous version?: Yes Nature of problem: The experimental searches for Higgs bosons have to be compared with theory predictions at a high level of accuracy. Radiative corrections are especially important in the Minimal Supersymmetric Standard Model (MSSM). Solution method: High-precision calculations (mostly based on the Feynman-diagrammatic approach) for various Higgs-boson observables in the MSSM are implemented. The program takes the basic model parameters as input and evaluates many MSSM Higgs-boson observables relevant for experimental Higgs-boson physics. Reasons for new version: Existing calculations have been refined (e.g., by the inclusion of complex parameters); many new observables have been implemented. Summary of revisions: Input parameters are now allowed to be complex, and non-minimal flavor violation is permitted. Besides the Higgs-boson masses also branching ratios and hadron-collider production cross-sections are calculated. Restrictions: Several observables are still missing and have to be implemented. Running time: The command-line frontend, which invokes essentially all FeynHiggs functions, takes 200 ms a single point in parameter space On a 3 GHz AMD CPU.

Supersymmetry beyond minimal flavor violation

We review the sources and phenomenology of non-minimal flavor violation in the MSSM. We discuss in some detail the most important theoretical and experimental constraints, as well as promising observables to look for supersymmetric effects at the LHC and in future experiments. We emphasize the sensitivity of flavor physics to the mechanism of supersymmetry breaking and to new degrees of freedom present at fundamental scales, such as the grand unification scale. We include a discussion of present data that may hint at departures from the standard model.

Flavour violation in gauge-mediated supersymmetry breaking models: Experimental constraints and phenomenology at the LHC

We present an extensive analysis of gauge-mediated supersymmetry breaking models with minimal and non-minimal flavour violation. We first demonstrate that low-energy, precision electroweak, and cosmological constraints exclude large “collider-friendly” regions of the minimal parameter space. We then discuss various possibilities how flavour violation, although naturally suppressed, may still occur in gauge-mediation models. The introduction of non-minimal flavour violation at the electroweak scale is shown to relax the stringent experimental constraints, so that benchmark points, that are also cosmologically viable, can be defined and their phenomenology, i.e. squark and gaugino production cross sections with flavour violation, at the LHC can be studied.

Squark and gaugino hadroproduction and decays in non-minimal flavour violating supersymmetry

We present an extensive analysis of squark and gaugino hadroproduction and decays in non-minimal flavour violating supersymmetry. We employ the so-called super-CKM basis to define the possible misalignment of quark and squark rotations, and we use generalized (possibly complex) charges to define the mutual couplings of (s)quarks and gauge bosons/gauginos. The cross sections for all squark–(anti-)squark/gaugino pair and squark-gaugino associated production processes as well as their decay widths are then given in compact analytic form. For four different constrained supersymmetry breaking models with non-minimal flavour violation in the second/third generation squark sector only, we establish the parameter space regions allowed/favoured by low-energy, electroweak precision, and cosmological constraints and display the chirality and flavour decomposition of all up- and down-type squark mass eigenstates. Finally, we compute numerically the dependence of a representative sample of production cross sections at the LHC on the off-diagonal mass matrix elements in the experimentally allowed/favoured ranges.

Huge right-handed current effects inB→K*(Kπ)ell+ell−in supersymmetry

Transverse asymmetries in the decay B->K*(K pi)l+l- are an extremely sensitive probe of right-handed flavour-changing neutral currents. We show how to include the contribution from the chiral partner of the electromagnetic operator on the transverse asymmetries at NLO in QCD factorization. We then consider supersymmetric models with non-minimal flavour violation in the down-squark sector. We include all the relevant experimental constraints and present a numerical formula for B->Xs gamma that takes into account the most recent NNLO calculations. We show that the flavour-changing parameters of these models are poorly constrained by present data and allow for large effects on the transverse asymmetries that we consider.

New two-loop contributions to hadronic EDMs in the MSSM

Flavor-changing terms with CP-violating phases in the quark sector may contribute to the hadronic electric dipole moments (EDMs). However, within the Standard Model (SM), the source of CP violation comes from the unique CKM phase, and it turns out that the EDMs are strongly suppressed. This implies that the EDMs are very sensitive to non-minimal flavor violation structures of theories beyond the SM. In this paper, we discuss the quark EDMs and CEDMs (chromoelectric dipole moments) in the MSSM with general flavor-changing terms in the squark mass matrices. In particular, the charged-Higgs mediated contributions to the down-quark EDM and CEDM are evaluated at two-loop level. We point out that these two-loop contributions may dominate over the one-loop induced gluino or Higgsino contributions even when the squark and gluino masses are around few TeV and \tan\beta is moderate.

Flavour-changing effects on e+e-→Hbs̄,Hb̄s in the MSSM

Flavour-changing effects originating from the exchange of scalar particles in the processes e+e-→Hxbs̄,Hxb̄s, with Hx≡h0,H0,A0, are investigated in the minimal supersymmetric standard model with non-minimal flavour violation at the one-loop level. The dominating SUSY-QCD contributions with squark–gluino loops are calculated and discussed. We consider the SUSY scenario with non-minimal flavour mixing in the down-type squark-mass matrix. The flavour-changing cross sections are derived, and we discuss the dependence on the MSSM parameters and the strength of flavour mixing. The values for the cross section can reach 10-4 pb for the production of the heavy Higgs boson H0 or A0, and only 10-7 pb for the light Higgs boson h0. Non-decoupling behaviour occurs for both h0,H0 production in the case of a common heavy SUSY mass scale.

Electroweak precision observables in the MSSM with non-minimal flavor violation

The leading corrections to electroweak precision observables in the MSSM with non-minimal flavor violation (NMFV) are calculated and the effects on M_W and sin^2 theta_eff are analyzed. The corrections are obtained by evaluating the full one-loop contributions from the third and second generation scalar quarks, including the mixing in the scalar top and charm, as well as in the scalar bottom and strange sector. Furthermore the leading corrections to the mass of the lightest MSSM Higgs boson, m_h, is obtained. The electroweak one-loop contribution to M_W can amount up to 140 MeV and up to 70x10^{-5} for sin^2 theta_eff, allowing to set limits on the NMFV parameters. The corrections for m_h are not significant for moderate generation mixing.