Flavor Observables Research Articles

Scaling of the CKM matrix in the 5D MSSM

We discuss a five-dimensional minimal supersymmetric standard model compactified on a ${S}^{1}/{Z}_{2}$ orbifold, looking at, in particular, the one-loop evolution equations of the Yukawa couplings for the quark sector and various flavor observables. Different possibilities for the matter fields are discussed; that is, where they are in the bulk or localized to the brane. The two possibilities give rise to quite different behaviors. By studying the implications of the evolution with the renormalization group of the Yukawa couplings and of the flavor observables, we find that, for a theory that is valid up to the unification scale, the case where fields are localized to the brane, with a large $\mathrm{tan}\ensuremath{\beta}$, would be more easily distinguishable from other scenarios.

Solution to the Flavor Problem of Warped Extra-Dimension Models

A minimal solution to the flavor problem of warped extra-dimension models, i.e., the excessive mixed-chirality contribution to CP violation in K-K ¯ mixing arising from Kaluza-Klein (KK) gluon exchange, is proposed. Extending the strong-interaction gauge group in the bulk by an additional SU(3), and breaking this symmetry to QCD via boundary conditions, the constraints arising from the ε(K) parameter are significantly relaxed. As a result, KK scales M(KK)~2 TeV are consistent with all flavor observables without significant fine-tuning. The model predicts an extended Higgs sector featuring massive color-octet scalars and a tower of KK pseudoaxial gluon resonances, whose existence is not in conflict with recent LHC dijet bounds.

Supersymmetric radiative flavour

We examine possibilities for the radiative generation of the Yukawa couplings and flavour structure in supersymmetric models in the supersymmetric phase. Not withstanding the non-renormalisation of the Wilsonian superpotential, this can occur through the 2-loop vertex renormalisation of the physical 1PI couplings. We describe this effect and construct models in which this occurs. For models attempting to reproduce the full flavour structure of the Standard Model, we analyse the tension between such models and constraints from low-energy flavour observables. We note that the tension is weakest for the case of generating Dirac neutrino masses.

Characterizing new physics models by effective dimensionality of parameter space

We show that the dimension of the geometric shape formed by the phenomenologically valid points inside a multi-dimensional parameter space can be used to characterise different new physics models and to define a quantitative measure for the distribution of the points. We explain a simple algorithm to determine the box-counting dimension from a given set of parameter points, and illustrate our method with examples from different models that have recently been studied with respect to precision flavour observables.

The effective Lagrangian for bulk fermions

We compute the dimension 6 effective Lagrangian arising from the tree level integration of an arbitrary number of bulk fermions in models with warped extra dimensions. The coefficients of the effective operators are written in terms of simple integrals of the metric and are valid for arbitrary warp factors, with or without an infrared brane, and for a general Higgs profile. All relevant tree level fermion effects in electroweak and flavor observables can be computed using this effective Lagrangian.

Indirect tests of the Randall-Sundrum model

I present phenomenological implications of the Randall-Sundrum model for indirect searches, specifically a selection of flavor observables and Higgs-related collider searches. I review the interplay of constraints from CP violation in flavor physics, possible effects in rare decays, and model-specific protection mechanisms. Deviations in the Higgs couplings to fermions and, at one-loop, to gluons are unexpectedly strong and lead to strong modifications in Higgs searches.

Signals ofCPviolation beyond the MSSM in Higgs and flavor physics

We study an extension of the Higgs sector of the minimal supersymmetric standard model (MSSM), considering the effects of new degrees of freedom at the TeV scale and allowing for sources of $CP$ violation beyond the MSSM. We analyze the impact of the beyond-the-MSSM sources of $CP$ violation on the Higgs collider phenomenology and on low energy flavor and $CP$-violating observables. We identify distinct Higgs collider signatures that cannot be realized, either in the case without $CP$-violating phases or in the $CP$-violating MSSM, and investigate the prospects to probe them at the Tevatron and the LHC. The most striking benchmark scenario has three neutral Higgs bosons that all decay dominantly into $W$ boson pairs and that are well within the reach of the 7 TeV LHC run. On the other hand, we also present scenarios with three Higgs bosons that have masses ${M}_{{H}_{i}}\ensuremath{\gtrsim}150\text{ }\text{ }\mathrm{GeV}$ and decay dominantly into $b\overline{b}$. Such scenarios are much more challenging to probe and can even lie completely outside the reach of the 7 TeV LHC run. We explore complementary scenarios with standard MSSM Higgs signals that allow us to accommodate a nonstandard ${B}_{s}$ mixing phase as indicated by D0, as well as the excess in ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ candidates recently reported by CDF. We find that, in contrast to the MSSM, a minimal flavor-violating soft sector is sufficient to generate significant corrections to $CP$-violating observables in meson mixing, compatible with Electric Dipole Moment constraints. In particular, a ${B}_{s}$ mixing phase ${S}_{\ensuremath{\psi}\ensuremath{\phi}}\ensuremath{\lesssim}0.15$ can be achieved for specific regions of parameter space, compatible with all the presently available experimental constraints on flavor observables. Such a nonstandard ${B}_{s}$ mixing phase would unambiguously imply a sizable suppression of ${S}_{\ensuremath{\psi}{K}_{S}}$ with respect to the standard model prediction and a $\mathrm{BR}({B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$ close to its 95% C.L. upper bound of $1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$.

Flavour Les Houches Accord: Interfacing flavour related codes

We present the Flavour Les Houches Accord (FLHA) which specifies a set of conventions for flavour-related parameters and observables. The FLHA uses the generic SUSY Les Houches Accord (SLHA) file structure. It defines the relevant Standard Model masses, Wilson coefficients, decay constants, bag parameters, flavour observables, etc. The accord provides a universal and model-independent interface between codes evaluating and/or using flavour-related observables.

Predictions of selected flavor observables within the standard model

This paper gathers a selection of standard model predictions issued from the metrology of the Cabibbo-Kobayashi-Maskawa parameters performed by the CKMfitter group. The selection includes purely leptonic decays of neutral and charged $B$, $D$, and $K$ mesons. In the light of the expected measurements from the LHCb experiment, special attention is given to the radiative decay modes of $B$ mesons as well as to the $B$-meson mixing observables, in particular the semileptonic charge asymmetries ${a}_{\mathrm{SL}}^{d,s}$ which have been recently investigated by the D0 experiment at Tevatron. Constraints arising from rare kaon decays are addressed, in light of both current results and expected performances of future rare kaon experiments. All results have been obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using Rfit to handle theoretical uncertainties.

SuperIso Relic v3.0: A program for calculating relic density and flavour physics observables: Extension to NMSSM

SuperIso Relic v3.0 is a public program for evaluation of relic density and flavour physics observables in the minimal supersymmetric extension of the Standard Model (MSSM) and next-to-minimal extension of the Standard Model (NMSSM). SuperIso Relic is an extension of the SuperIso program which adds to the flavour observables of SuperIso the computation of all possible annihilation and coannihilation processes of the LSP which are required for the relic density calculation. All amplitudes have been generated at the tree level with FeynArts/FormCalc, and widths of the Higgs bosons are computed with FeynHiggs or Hdecay at the two-loop level. SuperIso Relic also provides the possibility to modify the assumptions of the cosmological model, and to study their consequences on the relic density. New version program summaryProgram title:SuperIso Relic v3.0Catalogue identifier: AEGD_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGD_v2_0.htmlProgram obtainable from: CPC Program Library, Queenʼs University, Belfast, N. IrelandLicensing provisions: GNU General Public LicenseNo. of lines in distributed program, including test data, etc.: 1 198 441No. of bytes in distributed program, including test data, etc.: 13 486 632Distribution format: tar.gzProgramming language: C (C99 Standard compliant) and FortranComputer: 32- or 64-bit PC, MacOperating system: Linux, MacOSRAM: 100 MbClassification: 1.9, 11.6External routines: ISASUGRA/ISAJET, SOFTSUSY, SPheno, SuSpect, NMSSM-Tools, Hdecay, FeynHiggs, HiggsBounds, and/or 2HDMCCatalogue identifier of previous version: AEGD_v1_0Journal reference of previous version: Comput. Phys. Comm. 181 (2010) 1277Does the new version supersede the previous version?: YesNature of problem: Calculation of the lightest supersymmetric particle relic density, as well as flavour physics observables, in the MSSM and NMSSM, in order to derive constraints on the supersymmetric parameter space.Solution method:SuperIso Relic uses a SUSY Les Houches Accord file, which can be either generated automatically via a call to SOFTSUSY, ISAJET, SPheno, SuSpect or NMSSMTools, or provided by the user. This file contains the masses and couplings of the supersymmetric particles. SuperIso Relic then computes the lightest supersymmetric particle relic density as well as the most constraining flavour physics observables. To do so, it calculates first the widths of the Higgs bosons with FeynHiggs or Hdecay, and then it evaluates the squared amplitudes of the diagrams needed for the relic density calculation. These thousands of diagrams have been previously generated with the FeynArts/FormCalc package. SuperIso Relic is able to perform the calculations automatically in different supersymmetric scenarios, such as CMSSM, NUHM, AMSB and GMSB, in the MSSM or NMSSM.Reasons for new version:SuperIso Relic has been extended to the next to minimal supersymmetric extension of the Standard Model (NMSSM).Summary of revisions:•Extension of the calculations to the NMSSM.•Addition of the “reheating” cosmological scenario.•Addition of a “configure” script for automated configuration.•Implementation of interfaces for SuSpect, SPheno, NMSSMTools, Hdecay and HiggsBounds.•Merging of the “shared” and “static” versions into a single version.•Addition of two different MSSM scenarios (HCAMSB and MMAMSB) and the NMSSM scenarios (CNMSSM, NGMSB and NNUHM).•Six sample main programs have been added: hcamsb.c, mmamsb.c, cnmssm.c, ngmsb.c, nnuhm.c and test reheating.c. Additional instructions are given when run without arguments.•msugra.c renamed as cmssm.c.•Updated parameter values.•Faster “static” compilation.Unusual features:SuperIso Relic includes the possibility to alter the underlying cosmological model and to test the influence of the cosmological assumptions.Running time: Compilation: a couple of hours for the static compilation, a few minutes for the dynamical compilation. Run: about one second, or a few seconds if libraries need to be compiled on the fly.

Unitarity Triangle and New Physics

The Unitarity Triangle (UT) Analysis represents a powerful tool to test the SM and therefore to probe New Physics effects. After summarizing various tensions in the present UT analyses, we consider a number of Supersymmetric models showing their capability to solve these tensions. Moreover, we show how the characteristic patterns of correlations among flavour observables allow to distinguish between these different SUSY scenarios. We propose a “DNA-Flavour Test” of NP models, with the aim of showing a tool to distinguish between these NP scenarios, once additional data on flavour changing processes become available.

Flavour Physics in SUSY extensions of the SM in the LHC era

The coming years will witness tremendous progress at the “high energy frontier” accomplished primarily at the LHC. Important advances are also expected at the “high precision frontier” through the improved B s -physics experiments at the Tevatron and in particular LHCb at CERN. After summarizing the status of various tensions in the present Unitarity Triangle (UT) analyses, we consider a number of Supersymmetric models showing their capability to solve these tensions. Moreover, we show how the characteristic patterns of correlations among flavour observables allow to distinguish between these different SUSY scenarios. We propose a “DNA-Flavour Test” of NP models, with the aim of showing a tool to distinguish between these NP scenarios, once additional data on flavour changing processes become available.

Charmless two-body B-meson decays in QCD

The coming years will witness tremendous progress at the ''high energy frontier'' accomplished primarily at the LHC. Important advances are also expected at the ''high precision frontier'' through the improved B_s-physics experiments at the Tevatr on and in particular LHCb at CERN. After summarizing the status of various tensions in the present Unitarity Triangle (UT) analyses, we consider a number of Supersymmetric models showing their capability to solve these tensions. Moreover, we show how the characteristic patterns of correlations among flavour observables allow to distinguish between these different SUSY scenarios. We propose a ''DNA-Flavour Test'' of NP models, with the aim of showing a tool to distinguish between these NP scenarios, once a dditional data on flavour changing processes become available.

Minimal Flavor Constraints for Technicolor

We show the constraints on the vacuum polarization of the standard model gauge bosons from a minimal set of flavor observables valid for a model of dynamical electroweak symmetry breaking based on the walking dynamics. We will show that the constraints have a strong impact on the self-coupling and masses of the lightest spin-one resonances.

Less space for a new family of fermions

We investigate the experimentally allowed parameter space of an extension of the standard model (SM3) by one additional family of fermions. Therefore we extend our previous study of the CKM like mixing constraints of a fourth generation of quarks. In addition to the bounds from tree-level determinations of the 3$\times$3 CKM elements and FCNC processes ($K$-, $D$-, $B_d$-, $B_s$-mixing and the decay $b \to s \gamma$) we also investigate the electroweak $S$, $T$, $U$ parameters, the angle $\gamma$ of the unitarity triangle and the rare decay $B_s \to \mu^+ \mu^-$. Moreover we improve our treatment of the QCD corrections compared to our previous analysis. We also take leptonic contributions into account, but we neglect the mixing among leptons. As a result we find that typically small mixing with the fourth family is favored, but still some sizeable deviations from the SM3 results are not yet excluded. The minimal possible value of $V_{tb}$ is 0.93. Also very large CP-violating effects in $B_s$ mixing seem to be impossible within an extension of the SM3 that consists of an additional fermion family alone. We find a delicate interplay of electroweak and flavor observables, which strongly suggests that a separate treatment of the two sectors is not feasible. In particular we show that the inclusion of the full CKM dependence of the $S$ and $T$ parameters in principle allows the existence of a degenerate fourth generation of quarks.

Patterns of flavour violation in the presence of a fourth generation of quarks and leptons

We calculate a number of observables related to particle-antiparticle mixing and the branching ratios for the most interesting rare and CP-violating K and B decays in the Standard Model (SM3) extended by a fourth generation of quarks and leptons (SM4). A model-independent parameterisation of these observables in terms of gauge-independent functions is adopted, which is useful for studying the breaking of the universality between K, Bd and Bs systems through non-minimal flavour violating interactions. We calculate first the mass differences Delta M_i in the neutral K and B system, the mixing-induced CP asymmetries S_{psi K_S}, S_{psi phi}, S_{phi K_S}, S_{eta' K_S} and epsilon_K. Subsequently, a detailed analysis of K^+ -> pi^+ nu nu, K_L -> pi^0 nu nu, B_{s,d} -> mu^+ mu^-, B -> X_{s,d} nu nu, K_L -> pi^0 l^+ l^-, B -> X_s gamma and B -> X_{s,d} l^+ l^- is presented, and also epsilon'/epsilon is considered. For some of these observables the departures from SM3 predictions can still be spectacular. We discuss how the new mixing parameters (3 angles, 2 CP phases) can be determined using the flavour observables in question. We identify the different hierarchical structures in the SM4 flavour mixing matrix, allowed by phenomenological and theoretical constraints, and define the corresponding generalised Wolfenstein expansion. Most importantly, we show how the characteristic patterns of correlations among the considered flavour observables allow to distinguish this New Physics scenario from supersymmetric flavour models, the Littlest Higgs model with T-parity and the Randall-Sundrum model with custodial protection.

MINIMAL FLAVOR CONSTRAINTS FOR TECHNICOLOR

We analyze the constraints on the the vacuum polarization of the Standard Model gauge bosons from a minimal set of flavor observables valid for a general class of models of dynamical electroweak symmetry breaking. We will show that the constraints have a strong impact on the self-coupling and masses of the lightest spin-one resonances. Our analysis is applicable to any four and higher-dimensional extension of the Standard Model reducing to models of dynamical electroweak symmetry breaking.

Randall-Sundrum and strings

We investigate stringy excitations in Randall-Sundrum effective theories for electroweak symmetry breaking arising from embedding in string theory. RS is dual to a confining gauge theory, which we expect to have “QCD strings”, or color flux tubes. Stringy constructions of RS-like theories allow us to investigate the mass of these string states, which typically grows with a small fractional power of the number of colors N of the dual gauge theory. There are two known strong constraints on N for RS-like theories. The first arises from demanding that the Standard Model gauge couplings do not have a Landau pole at low scales. The second arises from demanding that the first-order confining phase transition in the early universe is able to proceed without leaving an empty universe, i.e. that the rate of bubble nucleation is not too small. We find that these constraints on N imply that string states are generically at most a factor of a few heavier than the lightest KK states, and we cannot self-consistently remain in the limit N,λ ≫ 1. We examine various string constructions of AdS or RS-like backgrounds, including orbifolds, theories on M5-branes, theories on D4-branes, and the recent F-theory construction of Polchinski and Silverstein. In every case we find that there are strong bounds on the mass of new stringy states. We briefly discuss important phenomenological implications due to the presence of such light stringy excitations, such as precision electroweak and flavor observables, as well as collider signals.

Simultaneous extraction of the Fermi constant and PMNS matrix elements in the presence of a fourth generation

Several recent studies performed on constraints of a fourth generation of quarks and leptons suffer from the ad-hoc assumption that 3 × 3 unitarity holds for the first three generations in the neutrino sector. Only under this assumption is one able to determine the Fermi constant G F from the muon lifetime measurement with the claimed precision of G F = 1.16637(1) × 10−5 GeV−2. We study how well G F can be extracted within the framework of four generations from leptonic and radiative μ and τ decays, as well as from K ℓ3 decays and leptonic decays of charged pions, and we discuss the role of lepton universality tests in this context. In the combined fit to leptonic and radiative μ and τ decays, K ℓ3 decays and leptonic decays of charged pions we find a p-value of 2.6 % for the fourth generation matrix element |U e4| = 0 of the neutrino mixing matrix. We emphasize that constraints on a fourth generation from quark and lepton flavour observables and from electroweak precision observables can only be obtained in a consistent way if these three sectors are considered simultaneously.

SuperIso Relic: A program for calculating relic density and flavor physics observables in Supersymmetry

We describe SuperIso Relic, a public program for evaluation of relic density and flavor physics observables in the minimal supersymmetric extension of the Standard Model (MSSM). SuperIso Relic is an extension of the SuperIso program which adds to the flavor observables of SuperIso the computation of all possible annihilation and coannihilation processes of the LSP which are required for the relic density calculation. All amplitudes have been generated at the tree level with FeynArts/ FormCalc, and widths of the Higgs bosons are computed with FeynHiggs at the two-loop level. SuperIso Relic also provides the possibility to modify the assumptions of the cosmological model, and to study their consequences on the relic density. Program summary Program title: SuperIso Relic Catalogue identifier: AEGD_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEGD_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: yes No. of lines in distributed program, including test data, etc.: 2 274 720 No. of bytes in distributed program, including test data, etc.: 6 735 649 Distribution format: tar.gz Programming language: C (C99 Standard compliant) and Fortran Computer: 32- or 64-bit PC, Mac Operating system: Linux, MacOS RAM: 100 Mb Classification: 1.9, 11.6 External routines: ISASUGRA/ISAJET and/or SOFTSUSY, FeynHiggs Does the new version supersede the previous version?: No (AEAN_v2_0) Nature of problem: Calculation of the lightest supersymmetric particle relic density, as well as flavor physics observables, in order to derive constraints on the supersymmetric parameter space. Solution method: SuperIso Relic uses a SUSY Les Houches Accord file, which can be either generated automatically via a call to SOFTSUSY or ISAJET, or provided by the user. This file contains the masses and couplings of the supersymmetric particles. SuperIso Relic then computes the lightest supersymmetric particle relic density as well as the most constraining flavor physics observables. To do so, it calculates first the widths of the Higgs bosons with FeynHiggs, and then it evaluates the squared amplitudes of the diagrams needed for the relic density calculation. These thousands of diagrams have been previously generated with the FeynArts/FormCalc package. SuperIso Relic is able to perform the calculations in different supersymmetry breaking scenarios, such as mSUGRA, NUHM, AMSB and GMSB. Reasons for new version: This version incorporates the calculation of the relic density, which is often used to constrain Supersymmetry. Summary of revisions: • Addition of the relic density calculation • Replacement of "float" type by "double". Unusual features: SuperIso Relic includes the possibility of altering the underlying cosmological model and testing the influence of the cosmological assumptions. Additional comments: This program is closely associated with the "SuperIso" program – CPC Program Library, Catalogue Id. AEAN. Running time: Compilation time: a couple of hours for the statically linked version, a few minutes for the dynamically linked version. Running time: about 1 second, or a few seconds if libraries need to be compiled on the fly.