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The current experimental status of the searches for the very rare decays and is discussed. These channels are highly sensitive to various extensions of the Standard Model, especially in the scalar and pseudoscalar sector. The recent, most sensitive measurements from the CDF, ATLAS, CMS and LHCb collaborations are discussed and the combined upper exclusion limit on the branching fractions determined by the LHC experiments is shown to be 4.2×10^-9 for and 0.8×10^-9 for . The implications of these tight bounds on a selected set of New Physics models is sketched.

We present a review of the operation and of the most recent results from the LHCb experiment at the LHC collider, based on the analyses performed using the data collected in 2010 and 2011, which correspond to an integrated luminosity of ~ 1 fb^-1. These measurements set stringent new limits on the contributions of New Physics processes in the field of rare b decays, and in the search for CP violation in B⁰ and mesons decays. In addition, a summary of results from studies of CP violation in the charm sector are presented, together with measurements in quarkonia production, in spectroscopy, in electroweak physics and in searches for exotica. The planned upgrade of LHCb is also briefly discussed.

In this article we present a short review on measurements of charmonia production at the LHCb experiment carried out during 2010, 2011 and 2012 data taking periods. The review covers the production of J/ψ, ψ(2S), χ_c, J/ψJ/ψ, as well as J/ψ in association with open charm. We also review the measurement of J/ψ polarization. The results are compared to theoretical predictions.

We review the recent progress in our theoretical understanding of flavor-changing processes. The overall excellent agreement with the corresponding measurements allows to derive severe constraints on possible extensions of the Standard Model (SM). The important interplay between flavor, electroweak (EW) and Higgs boson probes of new phenomena is emphasized. Once the EW hierarchy problem is confronted with null results from searches for direct production of new particles at the LHC, a case can be made against purely flavor trivial new physics (NP) at the TeV scale. Theory implications of the few open experimental flavor puzzles are also briefly discussed.

We review constraints from quark and lepton flavor violation on extra dimensional models with warped geometry, both in the minimal and the custodial model. For both scenarios, Kaluza–Klein (KK) masses that are large enough to suppress constraints from electroweak precision tests (EWPT) also sufficiently suppress all quark flavor and CP violation, with the exception of CP violation in mixing and (to a lesser extend) in mixing. In the lepton sector the minimal scenario leads to excessively large contributions to μ→eγ transitions, requiring KK masses of at least 20 TeV or larger.

Rare charm decays offer the unique possibility to explore flavor-changing neutral-currents in the up-sector within the Standard Model and beyond. Due to the lack of effective methods to reliably describe its low energy dynamics, rare charm decays have been considered as less promising for long. However, this lack does not exclude the possibility to perform promising searches for New Physics per se, but a different philosophy of work is required. Exact or approximate symmetries of the Standard Model allow to construct clean null-test observables, yielding an excellent road to the discovery of New Physics, complementing the existing studies in the down-sector. In this review, we summarize the theoretical and experimental status of rare charm $\left|\mathrm{\Delta }c\right|=\left|\mathrm{\Delta }u\right|=1$ transitions, as well as opportunities for current and future experiments such as LHCb, Belle II, BES III, the FCC-ee and proposed tau-charm factories. We also use the most recent experimental results to report updated limits on lepton-flavor conserving and lepton-flavor violating Wilson coefficients.

We point out that in SUSY flipped SU(5) model the bilarge neutrino mixing which can be accommodated in the lepton Yukawa couplings can induce interesting flavor mixings for the left-handed charged slepton and right-handed up-type squark. FCNC processes such as τ → μ + γ, mixing and t → u, c + h⁰ are predicted.

We study the LHC phenomenology of a general class of "Private Higgs" (PH) models, in which fermions obtain their masses from their own Higgs doublets with Yukawa couplings, and the mass hierarchy is translated into a dynamical chain of vacuum expectation values. This is accomplished by introducing a number of light gauge-singlet scalars, the "darkons," some of which could play the role of dark matter. These models allow for substantial modifications to the decays of the lightest Higgs boson, for instance through mixing with TeV-scale PH fields and light darkons: in particular, one could accommodate flavor-uncorrelated deviations from the SM vertices with TeV-scale degrees of freedom. We also discuss a new implementation of the PH framework, in which the quark and neutrino mixing angles arise as one-loop corrections to the leading order picture.

In experiments at the luminosity frontier, New Physics is being searched for in precision studies of rare processes. The most important example of such an effort is experiments at B factories and super B factories. While B factories have fully established the CKM quark transition matrix as the only source of CP violation in the Standard Model, the next generation of B factories, the so-called super B factories, will look for departures from the Standard Model. To collect a 50 times larger data sample, needed to reach the required sensitivity, a substantial B factory upgrade is being carried out. The SuperKEKB accelerator complex is designed for an increase in luminosity by a factor of 40. The upgraded Belle II spectrometer is being constructed to operate at considerably higher event rates, as well as higher backgrounds, accompanied by an increase in occupancy and radiation damage. Higher event rates also require substantial modifications in the trigger scheme, data acquisition system and computing. The paper discusses the detectors at B factories, the motivation for SuperKEKB/Belle II, the super B factory at KEK, as well as the requirements for the new accelerator and for the new detector. The present status of the project will be presented together with plans for the future. We will also discuss its competition, the LHCb experiment at the LHC.

We show that it is possible to construct observables to test the existence of new physics in a model independent way for the $D^0\to VV$ modes using a time-dependent analysis of the neutral $D$ meson. We show that it is possible to identify whether the NP is due to decay, mixing or a combination of both. We also provide numerical estimates for the polarization amplitudes for the $D^0\to \overline{K^{\ast 0}}{\rho }^0$ mode and show that our analysis is consistent with the present data.

The unexpected absence of unambiguous signals of New Physics (NP) at the TeV scale at the Large Hadron Collider (LHC) puts today flavor physics at the forefront. In particular, rare decays of b-hadrons represent a unique probe to challenge the Standard Model (SM) paradigm and test models of NP at a scale much higher than that accessible by direct searches. This article reviews the status of the field.

This review discusses the present experimental and theoretical status of rare flavor-changing neutral current b-quark decays at the beginning of 2018. It includes a discussion of the experimental situation and details of the currently observed anomalies in measurements of flavor observables, including lepton flavor universality. Progress on the theory side within and beyond the Standard Model theory is also discussed, together with potential New Physics interpretations of the present measurements.

This work summarizes the current status of the measured semileptonic branching fractions ${\bar{B}}^{0,-}\to X_c\mu \nu$. The sum of exclusive measurements is compared with the inclusive determination, accounting for isospin extrapolation. Further derived quantities are computed, taking into account different explanations for the unmeasured components of the total branching fraction. These quantities focus on the charge breakdown of the final states, and are designed for use as inputs or comparisons in future experimental measurements.

This paper describes the work pursued in the years 2008–2013 on improving the Standard Model prediction of selected flavor-physics observables. The latter includes: (1) ${𝜖}_K$, that quantifies indirect CP violation in the $K^0-{\bar{K}}^0$ system and (2) the very rare decay $B_s\to \mu \mu$, recently measured at the LHC. Concerning point (1), the paper describes our reappraisal of the long-distance contributions to ${𝜖}_K$,${}^{1\text{–}3}$ that have permitted to unveil a potential tension between CP violation in the $K^0$- and $B_d$-system. Concerning point (2), the paper gives a detailed account of various systematic effects pointed out in Ref. 4 and affecting the Standard Model $B_s\to \mu \mu$ decay rate at the level of 10% — hence large enough to be potentially misinterpreted as nonstandard physics, if not properly included. The paper further describes the multifaceted importance of the $B_{d,s}\to \mu \mu$ decays as new physics probes, for instance how they compare with $Z$-peak observables at LEP, following the effective-theory approach of Ref. 5. Both cases (1) and (2) offer clear examples in which the pursuit of precision in Standard Model predictions offered potential avenues to discovery. Finally, this paper describes the impact of the above results on the literature, and what is the further progress to be expected on these and related observables.

In this paper we present a phenomenological analysis of the Partially Aligned Two Higgs Doublet Model (PA-2HDM) by using leptonic decays of mesons and $B_{d,s}^0$–${\bar{B}}_{d,s}^0$ mixing. We focus our attention in a scenario where the leading contribution to FCNC is given by the tree-level interaction with the light pseudoscalar $A^0$ ($M_{A^0}\sim 250$ GeV). We show how an underlying flavor symmetry controls FCNC in the quark and lepton couplings with the pseudoscalar, without alignment between Yukawa matrices. Upper bounds on the free parameters are calculated in the context of the leptonic decays $B_{s,d}^0\to {\mu }^{+}{\mu }^{-}$ and $K_L^0\to {\mu }^{+}{\mu }^{-}$ and $B_{s,d}^0$ mixing. Also, our assumptions imply that bounds on New Physics contribution in the quark sector coming from $B_{s,d}^0$ mixing impose an upper bound on the parameters for the leptonic sector. Finally we give predictions of branching ratios for leptonic decay of mesons with FCNC and LFV.

A measurement of $B_s$ decay parameters using data collected by the ATLAS detector in $pp$ collisions at 13 TeV in 2015–2017 is performed. Integrated luminosity of this sample is 80.5 fb${}^{-1}$. The measurement of physical parameters are statistically combined with results obtained from Run 1 data at 7 and 8 TeV. The measured value of CP-violating phase ${\varphi }_s=-0.076\pm 0.034(\mathrm{\text{stat.}})\pm 0.019(\mathrm{\text{syst.}})$ is obtained, which has significantly better precision in comparison with Run 1 result. Precision of other physical parameters is also improved, including the decay width difference $\mathrm{\Delta }\mathrm{\Gamma }$. Further improvement is expected from the use of full Run 2 statistics, as well as from modifications in the analysis.

In a version of the PA-2HDM where only mixing between third and second fermion generations is allowed, we propose a mechanism to generate the second Yukawa matrix through a Unitary V-spin flavor transformation on the mass matrix for quarks and leptons. This flavor structure is constrained to be universal, that is, we use the same parameters to generate Yukawa matrix elements in the quark and leptonic sectors, reducing drastically the number of free parameters of the PA-2HDM.

As a consequence of this restrictive condition, we obtain relations between the Yukawa matrix elements, that we call the Universal Texture Constraint (UTC). We obtained an interval of values for the second Yukawa matrix elements, expressed in terms of the Cheng and Sher ansatz, for $\tau \to \mu {\mu }^{+}{\mu }^{-}$ and $\tau \to \gamma \mu$ coming from the UTC and experimental bounds for light scalar masses. Finally, we find the allowed parameter region when the experimental bounds and values for $B_s\to \mu \mu$ decays, $B_s^0-{\bar{B}}_s^0$ mixing, $\tau \to \mu {\mu }^{+}{\mu }^{-}$ and $\tau \to \gamma \mu$ are considered.

We present sensitivity projections for discovering a heavy resonance decaying to electron and muon pairs and for probing the charged lepton nonuniversality in such decays at the High Luminosity Large Hadron Collider (HL-LHC) and hadron-hadron Future Circular Collider (FCC-hh). The analysis takes into account the expected differences in the reconstruction efficiencies and the di-lepton mass resolutions for di-electron and di-muon final states. We demonstrate how the analyses at HL-LHC naturally pave the way for a FCC-hh machine thereby underlining its importance.

Quark flavor physics is the study of hadrons, their properties, and their decays into other particles. As a discipline, it simultaneously catalogues the nature of physical states within the Standard Model of particle physics, and in doing so tests the consistency and completeness of the Standard Model’s description of reality. Following the discovery of the Higgs field, it is more essential than ever to critically examine the Standard Model’s own coherence. Precision studies of quark flavor are one of the most sensitive experimental instruments for this task. I give a brief and necessarily selective overview of recent developments in quark flavor physics and discuss prospects for the next generation of experiments and facilities, with an emphasis on the energy scales of beyond Standard Model physics probed by these types of measurements.

Texture matrices are used to mitigate the redundancy inherent in the description of flavor physics via Yukawa couplings by eliminating some entries in order to identify relevant parameters. In this paper, the implications of a 2-zero texture mixing matrix in the parallel case are studied for leptons. Eight possible parametrizations were found and the parameter space was studied for all the scenarios using a chi-squared analysis. Using a model of GUT with $SO(10)$ symmetry, the mass matrices were restricted and a reduction of parameters was possible by adding the previously proposed Universal Texture Constraint for two scenarios. Constrains on the mass of the heaviest neutrino were found and the interval favored by UTC is $m_{{\nu }_3}\le 0.3$eV as well as general properties of the free parameters of the model.