Motivated by tensions between experimental measurements and SM predictions in $b\to s \ell^+\ell^-$ transitions, we present the first study of non-minimal flavour-violating Minimal Supersymmetric Standard Model (MSSM) scenarios contributing to the relevant Wilson coefficients to address the observed anomalies using SuperIso and MARTY. We calculate the full one-loop analytical contributions of the general MSSM to Wilson coefficients relevant for flavour anomalies, together with the anomalous muon magnetic dipole moment $(g-2)_μ$. We show that, after imposing theoretical constraints on the flavour-violating parameters we can find scenarios in agreement with the experimental measurements that can address at the same time the tensions in flavour observables and in $(g-2)_μ$.
The collection of a few anomalies in semileptonic $B$-decays invites to speculate about the emergence of some strikingly new phenomena. Here we offer a possible interpretation of these anomalies in the context of a weakly broken $U(2)^5$ flavour symmetry and lepto-quark mediators.
The U(2)_R x U(2)_L symmetry of QCD with two massless flavours is subject to anomalies which affect correlation functions involving the singlet currents A^0_μor V^0_μ. These are relevant for pion-photon interactions, because - for two flavours - the electromagnetic current contains a singlet piece. We give the effective Lagrangian required for the corresponding low energy analysis to next-to-leading order, without invoking an expansion in the mass of the strange quark. In particular, the Wess-Zumino-Witten term that accounts for the two-flavour anomalies within the effective theory is written …
In this manuscript, based on arXiv:2209.00276, I present a model which can simultaneously explain and connect the flavour hierarchies of the Standard Model with flavour anomalies in $B$-physics. I will briefly introduce the model and highlight the main features, including a common origin of Yukawa couplings and vector leptoquark $U_{1}$ couplings to Standard Model fermions. A GIM-like mechanism allows for large leptoquark couplings which can explain the $B$-anomalies, while protecting from the most dangerous FCNCs that could be mediated by a heavy coloron and $Z'$. Finally, I will highlight so…
B-decays mediated by both charged currents and neutral currents have provided hints of violation of lepton flavour universality. By assuming an explanation of these anomalies in terms of new physics at the TeV scale affecting the third fermion generation, we review the relevant constraints. In particular we illustrate the effects of electroweak radiative corrections and their impact on a consistent interpretation of the data. The simplest scenario is ruled out and we briefly discuss the modifications required to simultaneously describe the whole set of anomalies.
We propose renormalizable models of new physics that can explain various anomalies observed in decays of B-mesons to electron and muon pairs. The new physics states couple to linear combinations of Standard Model fermions, yielding a pattern of flavour violation that gives a consistent fit to the gamut of flavour data. Accidental symmetries prevent contributions to baryon- and lepton-number-violating processes, as well as enforcing a loop suppression of new physics contributions to flavour violating processes. Data require that the new flavour-breaking couplings are largely aligned with the Yu…
Several measurements of B-meson decay observables show deviations from Standard Model (SM) predictions, some of them hinting at violation of lepton flavour universality (LFU). I discusses how the anomalies in rare B decays can be explained by partial compositeness. Partial compositeness is a key ingredient of models with a composite Higgs boson and generically leads to violation of LFU. After presenting a simple model with partial compositeness that is able to explain the anomalies in rare B decays, the flavour phenomenology of a minimal UV completion of a composite Higgs model with partial co…
Discrepancies between recent experimental results and their respective Standard Model predictions, known as flavour anomalies, are reported in semileptonic charged and neutral-current $B$-decays, the muon magnetic moment $(g-2)_μ$, and the extraction of the Cabibbo angle. In this proceedings, we review two New Physics models that introduce two scalar mediators at the TeV scale and aim at a combined explanation of the flavour anomalies. The first model features the leptoquarks $S_1$ and $S_3$ and provides tree level solutions to both $B$-anomalies and one-loop level solution to the anomalous $(…
At the present time, there are discrepancies with the predictions of the SM in several observables involving $b \to s \ell^+ \ell^-$ and $b \to c \ell^- {\barν}_\ell$ decays. These are the $B$ flavour anomalies. In this review, we summarize the data as of Moriond 2021 and present theoretical new-physics explanations from both a model-independent effective-field-theory point of view and through the building of explicit models. Throughout, we stress the complementarity of these two approaches. We also discuss combined explanations of both $B$ anomalies, and present models that also explain other…
Motivated by the recent hints of lepton flavour non-universality in $B$-meson semi-leptonic decays, we study the constraints of perturbative unitarity on the new physics interpretation of the anomalies in $b \to c \ell \bar ν$ and $b \to s \ell \bar \ell$ transitions. Within an effective field theory approach we find that $2 \to 2$ fermion scattering amplitudes saturate the unitarity bound below 9 TeV and 80 TeV, respectively for $b \to c \ell \bar ν$ and $b \to s \ell \bar \ell$ transitions. Stronger bounds, up to few TeV, are obtained when the leading effective operators are oriented in the …
The LHCb measurement of the $μ/e$ ratio $R_{K^*}$ indicates a deficit with respect to the Standard Model prediction, supporting earlier hints of lepton universality violation observed in the $R_K$ ratio. We show that the $R_K$ and $R_{K^*}$ ratios alone constrain the chiralities of the states contributing to these anomalies, and we find deviations from the Standard Model at the $4σ$ level. This conclusion is further corroborated by hints in the theoretically challenging $b\to sμ^+μ^-$ distributions. Theoretical interpretations in terms of $Z'$, lepto-quarks, loop mediators, and composite dynam…
In supersymmetric models new sources of lepton flavour violation (LFV) may enhance the rates of charged lepton flavour violating processes, like mu to e gamma, and generate distinct final states at future colliders, e.g. tau mu + jets + missing energy. We discuss the role of chargino pair production for the LFV signals at e+e- colliders.
We summarize the results on patterns of flavour violation in a Randall-Sundrum model with custodial protection (RSc) and compare them with those identified in the Littlest Higgs Model with T--parity (LHT) and in a number of SUSY Flavour Models. While K decays play in this presentation a prominent role, the inclusion of B physics and lepton flavour violation is crucial in the distinction between these three popular extensions of the Standard Model (SM) by means of flavour physics.
In a generic supersymmetric extension of the Standard Model, whether unified or not, a simple and well motivated U(2) symmetry, acting on the lightest two generations, completely solves the flavour changing problem and necessarily leads to a predictive texture for the Yukawa couplings.
The Standard Model decay rate of the $B_c$ meson is discussed together with a novel approach that uses experimental data in combination with an operator product expansion. In the new method differences of $B,\,D$ and $B_c$ meson decay rates are considered for which the free-quark contributions drop out, leading to a reduction of the theory prediction.
It is suggested that the Higgs boson may have a branching ratio into the $c \bar{c}$ mode suppressed by several orders of magnitude compared with conventional predictions and in addition some small but detectable flavour-violating modes such as $b \bar{s}$ and $τ\barμ$. The suggestion is based on a scheme proposed and tested earlier for explaining the mixing pattern and mass hierarchy of fermions in terms of a rotating mass matrix. If confirmed, the effects would cast new light on the geometric origin of fermion generations and of the Higgs field itself.
Motivated by an explanation of the $R_{K^{(*)}}$ anomalies, we propose a Standard Model extension via two scalar SU(2)$_L$ triplet leptoquarks and three generations of triplet Majorana fermions. The gauge group is reinforced by a $Z_2$ symmetry, ensuring the stability of the lightest $Z_2$-odd particle, which is a potentially viable dark matter candidate. Neutrino mass generation occurs radiatively (at the three-loop level), and leads to important constraints on the leptoquark couplings to leptons. We consider very generic textures for the flavour structure of the $h_1$ leptoquark Yukawa coupl…
In recent years, significant experimental indications that point towards Lepton Flavour Universality violating effects in B-decays, involving $b \to c τν$ and $b \to s \ell^+ \ell^-$ have been accumulated. A possible New Physics explanation can be sought within the framework of R-parity violating Supersymmetry, which contains the necessary ingredients to explain the anomalies via both leptoquark, tree-level exchange and one-loop diagrams involving purely leptonic interactions. In addition, an approximate $U(2)^2$ flavour symmetry, that respects gauge coupling unification, successfully controls…
We discuss a supersymmetric inverse seesaw model in which lepton flavour violating decays can be enhanced either by flavour violating slepton contributions or by the non-unitarity of the charged current mixing matrix. As an example we calculate Br(mu -> e gamma) taking into account both heavy lepton exchange as well as supersymmetric diagrams in a minimal supergravity framework. We find that the for the same parameters the rate can be enhanced with respect to seesaw model expectations, with or without supersymmetry.
We discuss charged lepton flavour violating processes such as mu -> e gamma in supersymmetric extensions of the Standard Model and in models with gauge-Higgs unification and a warped extra dimension. In both classes of models the processes turn out to be compatible with present experimental bounds, but can be detected by future experiments, thanks to the presence of a flavour symmetry G_f which constrains the form of the relevant couplings. The symmetry G_f is chosen to be finite, discrete and non-abelian and also helps to predict the peculiar lepton mixing pattern.
We derive the renormalization group equations for dimensionless couplings and soft supersymmetry breaking (SSB) parameters given arbitrary high scale inputs, incorporating 1-loop thresholds. A program (to be incorporated into ISAJET) has been developed, which includes flavour violating couplings of superparticles based on an arbitrary framework for the high scale flavour structure of SSB parameters. The weak scale flavour structure derived in this way can be applied to the study of SUSY flavour changing decays. As an illustration, we recalculate the branching ratio of the flavour-violating dec…
We propose a theory of flavour based on abelian horizontal gauge symmetries and modular invariances. We construct explicit supergravity models where the scale of the horizontal $U(1)$ symmetry breaking is fixed by the Green-Schwarz mechanism for anomaly cancellation. The supersymmetric spectrum is obtained in terms of the $U(1)$ charges which are determined by the Yukawa matrices.
Flavour changing top decays $t \to c Z^0, t \to c g$ and $t \to c γ$ are predicted with invisible rates within the standard model and may represent a window on new physics. We consider these processes in supersymmetric extensions of the standard model and we show that observable rates can be obtained only if the SUSY breaking is non universal and flavour dependent.
We compute the lepton flavour violating couplings of Higgs bosons in the Minimal Supersymmetric Standard Model, and show that they can induce the decays (h,H,A) --> mu tau at non-negligible rates, for large tan(beta) and sizeable smuon-stau mixing. We also discuss the prospects for detecting such decays at LHC and other colliders, as well as the correlation with other flavour violating processes, such as tau --> mu gamma and tau --> 3 mu.
In supersymmetric extensions of the Standard Model, the Yukawa and/or mass terms of the heavy neutrinos can generate lepton flavour violating slepton mass terms. These new supersymmetric sources of lepton flavour violation may both enhance the rates of charged lepton flavour violating processes, l_a -> l_b y, and generate distinct final states, like l_b l_a + jets + missing E_T, at future colliders. First, we discuss the sensitivity of future e^+e^- colliders to the SLFV independently of the lepton flavour violating mechanism. Second, we study lepton flavour violating slepton pair production a…
We consider a $U(1)'$ extended supersymmetric model with a right-handed neutrino superfield which can generate light neutrino mass by Type I seesaw mechanism. The lighter superpartner of the right-handed neutrino could be the scalar dark matter. These right-handed sneutrinos can come from the decay of $\tilde{Z'}$, superpartner of the extra gauge boson $Z'$. Left-right handed sneutrino mixings affect their decays further, giving rise to displaced "lepton flavour violating" signatures. A wino-like chargino NLSP (next to lightest supersymmetric particle) creates even more interesting decay topol…
We explore the flavour structure of custodial Randall-Sundrum (RS) models in the context of the recently observed deviations in the decay of the $B$ mesons. The anomalies in the $b\rightarrow s ll$ processes can be easily fit with partially composite second generation leptons and third generation quarks. We establish correlation with the parameter space consistent with the flavour anomalies in the neutral current sector and obtain predictions for rare $K$- decay which are likely to be another candle for NP with increased precision. Two scenarios are considered: A) Right handed muon coupled mor…
In minimal supersymmetric models the $Z$-penguin usually provides sub-dominant contributions to charged lepton flavour violating observables. In this study, we consider the supersymmetric inverse seesaw in which the non-minimal particle content allows for dominant contributions of the $Z$-penguin to several lepton flavour violating observables. In particular, and due to the low-scale (TeV) seesaw, the penguin contribution to, for instance, $\Br(μ\to 3e)$ and $μ-e$ conversion in nuclei, allows to render some of these observables within future sensitivity reach. Moreover, we show that in this fr…
We study the impact of the inverse seesaw mechanism on several low-energy flavour violating observables such as tau decaying to three muons in the context of the Minimal Supersymmetric Standard Model. As a consequence of the inverse seesaw, the contributions of the right-handed sneutrinos significantly enhance the Higgs-mediated penguin diagrams. We find that different flavour violating branching ratios can be enhanced by as much as two orders of magnitude. We also comment on the impact of the Higgs-mediated processes on the leptonic B-meson decays and on the Higgs flavour violating decays.
Significant deviations from the Standard Model are observed in semileptonic charged and neutral-current B-decays, the muon magnetic moment, and the extraction of the Cabibbo angle. We propose that these deviations point towards a coherent pattern of New Physics effects induced by two scalar mediators, a leptoquark $S_1$ and a charged singlet $ϕ^+$. While $S_1$ can provide solutions to charged-current $B$-decays and the muon magnetic moment, and $ϕ^+$ can accommodate the Cabibbo-angle anomaly independently, their one-loop level synergy can also address neutral-current $B$-decays. This framework…
We study a new supersymmetric mechanism for lepton flavour violation in muon and tau decays and muon -> e conversion in nuclei, within a minimal extension of the MSSM with low-mass heavy singlet neutrinos and sneutrinos. We find that the decays mu -> e gamma, tau -> e gamma and tau -> mu gamma are forbidden in the supersymmetric limit of the theory, whereas other processes, such as mu -> eee, mu -> e conversion, tau -> eee and tau -> e mu mu, are allowed and can be dramatically enhanced several orders of magnitude above the observable level by potentially large neutrino Yukawa coupling effects…
In minimal supersymmetric seesaw models, the contribution to lepton flavour violation from Z-penguins is usually negligible. In this study, we consider the supersymmetric inverse seesaw and show that, in this case, the Z-penguin contribution dominates in several lepton flavour violating observables due to the low scale of the inverse seesaw mechanism. Among the observables considered, we find that the most constraining one is the muon to electron conversion rate which is already restricting the otherwise allowed parameter space of the model. Moreover, in this framework, the Z-penguins exhibit …
The supersymmetric flavour and CP problems can be avoided if the first two generations of sfermions are heavier than a few TeV and approximately degenerate in mass. However using flavour and CP-violating constraints on the third sfermion generation, together with the decoupling of the first two generations, can dramatically affect cosmological predictions such as the relic abundance of stable particles. In particular, we show that if the lightest supersymmetric particle is essentially bino-like then requiring that all flavour changing neutral current and CP-violating processes are adequately s…
We consider a supersymmetric scenario with large flavour violating A-terms in the stop/scharm sector and study their impact on the Higgs mass, the electroweak rho parameter and the effective Higgs couplings to gluons, photons and charm quarks. For each observable we present explicit analytical expressions which exhibit the relevant parametric dependences, both in the general case and in specific limits. We find significant effects and comment on phenomenological implications for the LHC and future colliders.
We explore the possibility that lepton family numbers and baryon number are such good symmetries of Nature because they are the global remnant of a spontaneously broken gauge symmetry. An almost arbitrary linear combination of these symmetries (together with a component of global hypercharge) can be consistently gauged, if the Standard Model (SM) fermion content is augmented by three chiral SM singlet states. Within this framework of $U(1)$ extensions of the SM one generically expects flavour non-universality to emerge in the charged leptons, in such a way that naturally prevents lepton flavou…
We study charged lepton flavour violation in low-scale seesaw models of minimal supergravity, which realize large neutrino Yukawa couplings thanks to approximate lepton-number symmetries. There are two dominant sources of lepton flavour violation in such models. The first source originates from the usual soft supersymmetry-breaking sector, whilst the second one is entirely supersymmetric and comes from the supersymmetric neutrino Yukawa sector. Within the framework of minimal supergravity, we consider both sources of lepton flavour violation, soft and supersymmetric, and calculate a number of …
We consider the supersymmetric seesaw mechanism induced by the exchange of heavy SU(2)_W triplet states, rather than `right-handed' neutrino singlets, to generate neutrino masses. We show that in this scenario the neutrino flavour structure tested at low-energy in the atmospheric and solar neutrino experiments is directly inherited from the neutrino Yukawa couplings to the triplets. This allows us to predict the ratio of the tau --> mu gamma (or tau --> e gamma) and mu --> e gamma decay rates in terms of the low-energy neutrino parameters. Moreover, once the model is embedded in a grand unifie…
It has been shown that, in the context of the MSSM, the Supersymmetric Flavour Problem cannot be solved by just letting the sfermions of the first two generations be relatively heavy. The reason is twofold: naturalness of the Fermi scale on one side, need for positive squared stop masses on the other. The situation is much more promising in models without a light Higgs boson, in which the goal can be met. The prices are: a relatively low messenger scale, semiperturbativity before the GUT scale, and some amount of degeneracy/alignement of order of the Cabibbo angle in the sfermion sector. A cru…
We present two recent developments on lepton flavour violation in the MSSM. 1) The supersymmetric seesaw mechanism can be realized through the exchange of heavy SU(2)_W-triplet states, rather than `right-handed' neutrinos. In this scenario the ratio of the tau --> mu gamma (or tau --> e gamma) and mu --> e gamma rates are unambiguously predicted in terms of the low-energy neutrino parameters. 2) Lepton flavour violating decays of the Higgs bosons, (h, H, A) --> mu tau, are induced at one-loop level. The branching ratios can reach 10^{-4} for large tan(beta) and sizeable smuon-stau mixing. Inte…
As a consequence of the large top quark Yukawa coupling, supersymmetric unified theories with soft supersymmetry breaking terms generated at the Planck scale predict lepton flavour and CP violating processes with significant rates. The flavour violating parameters of the low energy theory are derived in both SU(5) and SO(10) theories, and are used to calculate the rate for mu --> e gamma. The sensitivity of the search for mu --> e gamma is compared with that for mu --> e conversion in atoms, tau --> mu gamma and the electric dipole moment of the electron. The experimental search for these proc…
We present a global likelihood function in the space of dimension-six Wilson coefficients in the Standard Model Effective Field Theory (SMEFT). The likelihood includes contributions from flavour-changing neutral current B decays, lepton flavour universality tests in charged- and neutral-current B and K decays, meson-antimeson mixing observables in the K, B, and D systems, direct CP violation in K -> ππ, charged lepton flavour violating B, tau, and muon decays, electroweak precision tests on the Z and W poles, the anomalous magnetic moments of the electron, muon, and tau, and several other prec…
If the mechanism of Supersymmetry breaking is not flavour blind, some flavour symmetry is likely to be needed to prevent excessive flavour changing neutral current effects. We discuss two flavour models (based respectively on a U(2) and on a SU(3) horizontal symmetry) providing a good fit to fermion masses and mixings and particularly constraining the supersymmetry soft breaking terms. We show that, while reproducing successfully the Standard Model fit of the unitarity triangle, it is possible to obtain sizable deviations from the Standard Model predictions for three very clean B-physics obser…
We review the recent highlights of theoretical flavour physics, based on the theory summary talk given at FPCP2017. Over the past years, a number of intriguing anomalies have emerged in flavour violating $K$ and $B$ meson decays, constituting some of the most promising hints for the presence of physics beyond the Standard Model. We discuss the theory status of these anomalies and outline possible future directions to test the underlying New Physics.
We analyse the top flavour violating decays in general supersymmetric model using the mass insertion approximation. In particular, we discuss the impact of a light right-handed top-squark and large mixing between the first or second and third generation of up-squarks on processes as t -> q gamma,g . We also take into account the relevant experimental constraints from B-physics and the requirements for a successfull electroweak baryogenesis on squark mixings. We show that for general large mixings in squarks mass matrix, the branching ratio of the t -> q gamma, g (q=u,c) can be as large as 10^{…
We summarize the predictions for the radiative decays l_j->l_i γwithin the context of the supersymmetric type II seesaw mechanism considering universal boundary conditions for the soft SUSY breaking terms. The dependence on the low-energy neutrino parameters is discussed and the deviations from the analytical results for large $\tanβ$ analyzed.
Precision measurements of flavour observables provide powerful tests of many extensions of the Standard Model. This contribution covers a range of flavour measurements of $b\to s\ell^+\ell^-$ transitions, several of which are in tension with the Standard Model of particle physics, as well as their theoretical interpretation. The basics of the theoretical background are discussed before turning to the main question of the field: whether the anomalies can be explained by QCD effects or whether they may be indicators of effects beyond the Standard Model.
We study the impact of the inverse seesaw mechanism on several leptonic and hadronic low-energy flavour-violating observables in the context of the Minimal Supersymmetric Standard Model. Indeed, the contributions of the light right-handed sneutrinos from the inverse seesaw significantly enhance the Higgs-mediated penguin diagrams. We find that this can increase the different branching ratios by as much as two orders of magnitude.
We study supersymmetric models with a GUT-sized extra dimension, where both the Higgs fields and the SUSY breaking hidden sector are localized on a 4D brane. Exponential wave function profiles of the matter fields give rise to hierarchical structures in the Yukawa couplings and soft terms. Such structures can naturally explain hierarchical fermion masses and mixings, while at the same time alleviating the supersymmetric flavour problem. We discuss two sources of supersymmetry breaking, radion mediation and brane fields, and perform a detailed numerical analysis, thoroughly taking into account …
Treating the MSSM as an effective theory below a threshold scale Lambda, we study the consequences of having dimension-five operators in the superpotential for flavour and CP-violating processes. Below the supersymmetric threshold such terms generate flavour changing and/or CP-odd effective operators of dimension six composed from the Standard Model fermions, that have the interesting property of decoupling linearly with the threshold scale, i.e. as 1/(Lambda m_soft), where m_soft is the scale of soft supersymmetry breaking. The assumption of weak-scale supersymmetry, together with the stringe…
We study flavour violation in a supersymmetric SO(10) implementation of the type II seesaw mechanism, which provides a predictive realization of triplet leptogenesis. The experimental upper bounds on lepton flavour violating processes have a significant impact on the leptogenesis dynamics, in particular they exclude the strong washout regime. Requiring successful leptogenesis then constrains the otherwise largely unknown overall size of flavour-violating observables, thus yielding testable predictions. In particular, the branching ratio for mu -> e gamma lies within the reach of the MEG experi…
Motivated by the recent experimental progress on the $R_{D^{(\ast)}}$ and $R_{K^{(\ast)}}$ anomalies in $B$-decays, we consider an extension of the Standard Model by a single vector leptoquark field. We study how one can achieve the required lepton flavour non-universality, starting from a priori universal gauge couplings. While the unitary coupling flavour structure, induced by the mass misalignment of quarks and leptons after $SU(2)_L$ breaking, does not allow to comply with stringent bounds from lepton flavour violating processes, we find that effectively non-unitary couplings, due to mixin…
We study neutrino masses in the framework of the supersymmetric inverse seesaw model. Different from the non-supersymmetric version a minimal realization with just one pair of singlets is sufficient to explain all neutrino data. We compute the neutrino mass matrix up to 1-loop order and show how neutrino data can be described in terms of the model parameters. We then calculate rates for lepton flavour violating (LFV) processes, such as $μ\to e γ$, and chargino decays to singlet scalar neutrinos. The latter decays are potentially observable at the LHC and show a characteristic decay pattern dic…
With the recent experimental hint of new physics from flavor physics anomalies, combined with the evidence from neutrino mass and dark matter, we consider a minimal extension of SM with a scalar leptoquark and a fermion triplet. The scalar leptoquark with couplings to leptons and quarks can explain lepton flavor non-universality observables $R_K$, $R_{K^{(*)}}$, $R_{D^{(*)}}$ and $R_{J/ψ}$. Neutral component of fermion triplet provides current abundance of dark matter in the Universe. The interesting feature of the proposal is that the minimal addition of these phenomenologically rich particle…
We describe the phenomenology of the flavour changing neutral current sector of a supersymmetric model, invariant under the T' discrete flavour group. This model has been proposed in Ref.[1] and describes realistic leptonic and hadronic masses and mixings and predicts the amount of flavour changing in terms of the small flavour breaking parameter u in [0.007, 0.05]. For small values of u, the model almost reduces to the MSUGRA framework, while sizable deviations from MSUGRA can be, instead, observed when larger values of u and tan(beta) are considered. We analyse in detail the T' BR(mu --> e g…
We investigate Majorana dark matter in a new variant of $U(1)_{L_μ-L_τ}$ gauge extension of Standard Model, containing three additional neutral fermions $N_{e}, N_μ, N_τ$, along with a $(\bar{3},1,1/3)$ scalar Leptoquark (SLQ) and an inert doublet, to study the phenomenology of dark matter, neutrino mass generation and flavour anomalies on a single platform. The lightest mass eigenstate of the $N_μ, N_τ$ neutral fermions plays the role of dark matter. We compute the WIMP-nucleon cross section in leptoquark portal and the relic density mediated by inert doublet components, leptoquark and the ne…
By an explicit calculation we show that in ordinary SU(5) logarithmic divergence in the amplitude of $μ\to eγ$ cancels among diagrams and remaining finite part is suppressed by at least $1/M_{GUT}^2$. In SUSY SU(5), when the effect of flavour changing wave function renormalization is taken into account such logarithmic correction disappears, provided a condition is met among SUSY breaking masses. In SUGRA-inspired SUSY GUT the remaining logarithmic effect is argued not to be taken as a prediction of the theory.
We introduce two scalar leptoquarks, the SU$(2)_L$ isosinglet denoted $ϕ\sim(\mathbf{3}, \mathbf{1}, -1/3)$ and the isotriplet $φ\sim(\mathbf{3}, \mathbf{3}, -1/3)$, to explain observed deviations from the standard model in semi-leptonic $B$-meson decays. We explore the regions of parameter space in which this model accommodates the persistent tensions in the decay observables $R_{D^{(*)}}$, $R_{K^{(*)}}$, and angular observables in $b\to s μμ$ transitions. Additionally, we exploit the role of these exotics in existing models for one-loop neutrino mass generation derived from $ΔL=2$ effective …
Based on recent HQET sum rule and lattice calculations we present updated Standard Model predictions for the mass differences of neutral $B$ mesons: $ΔM_s^{\rm SM} = \left(18.4^{+0.7}_{-1.2} \right) \mbox{ps}^{-1}$ and $ΔM_d^{\rm SM} = \left(0.533^{+0.022}_{-0.036} \right) \mbox{ps}^{-1}$ and study their impact on new physics models that address the present hints of anomalous data in $b \to s \ell \ell$ transitions. We also examine future prospects of further reducing the theory uncertainties and discuss the implications of a 2025 scenario with $ΔM_s^\text{SM 2025} = \left(18.4 \pm 0.5\right) …
We construct an extension of the Standard Model with a scalar leptoquark $ϕ\sim (3,1,-\tfrac13)$ and the discrete flavour symmetry $G_f=D_{17}\times Z_{17}$ to explain anomalies observed in charged-current semi-leptonic $B$ meson decays and in the muon anomalous magnetic moment, together with the charged fermion masses and quark mixing. The symmetry $Z_{17}^{\rm diag}$, contained in $G_f$, remains preserved by the leptoquark couplings, at leading order, and efficiently suppresses couplings of the leptoquark to the first generation of quarks and/or electrons, thus avoiding many stringent experi…
