Search

Without adhering to any specific model, we have presented 4 × 4 quark mixing matrix as an extension of the 3 × 3 Particle Data Group (PDG) parametrization of the Cabibbo–Kobayashi–Maskawa (CKM) matrix Using unitarity constraints as well as the hierarchy among the elements of the 3 × 3 CKM matrix, we have found the hierarchy among the fourth row and fourth column elements of the 4 × 4 quark mixing matrix. Further, for the fourth generation case, we have explicitly found the nine independent rephasing invariant parameters J 4 × 4 . Also, using phenomenological estimates of the fourth row and fourth column elements, we have numerically evaluated these nine parameters. [ABSTRACT FROM AUTHOR]

In this paper, we present the current situation of the determinations of the first-row CKM components and show the Cabibbo angle anomaly corresponding to a deficit in the first-row CKM unitarity condition at the 3σ level. In this contribution, we show two new physics interpretations: heavy vector-like quark models and a MeV scale sterile neutrino scenario. The super tau-charm facility will directly probe the other CKM unitarity conditions related to Vcd. [ABSTRACT FROM AUTHOR]

The search for New Physics (NP) beyond the Standard Model (SM) has been a central focus of particle physics, including in the context of B-meson decays involving b → s ℓ ℓ transitions. These transitions, mediated by flavour-changing neutral currents, are highly sensitive to small NP effects due to their suppression in the SM. While direct searches at colliders have not yet led to NP discoveries, indirect probes through semi-leptonic decays have revealed anomalies in observables such as the branching fraction B (B → K μ μ) and the angular observable P 5 ′ (B → K ∗ μ μ) . In order to assess the observed tensions, it is essential to ensure an accurate SM prediction. In this review, we examine the theoretical basis of the B → K (∗) ℓ ℓ decays, addressing in particular key uncertainties arising from local and non-local form factors. We also discuss the impact of QED corrections to the Wilson coefficients, as well as the effect of CKM matrix elements on the predictions and the tension with the experimental measurements. We discuss the most recent results, highlighting ongoing efforts to refine predictions and to constrain potential signs of NP in these critical decay processes. [ABSTRACT FROM AUTHOR]

Since its discovery in the 1960s, the violation of CP symmetry has intrigued scientists and stimulated the advancement of knowledge in particle physics. Numerous experiments were designed and built to study it in increasingly deeper detail. Nowadays, the phenomenon is well framed within the Standard Model of Particle Physics. Nevertheless, new results are being produced by modern experiments at colliders that challenge the current understanding of the model. In this article, the current status of CP violation studies and the role of CP violation in the search for effects beyond the Standard Model are described together with the prospects for ongoing and future experiments. [ABSTRACT FROM AUTHOR]

Using unitarity, unlike the approaches available in the literature, we construct 9 independent representations of the Cabibbo–Kobayashi–Maskawa) CKM matrix starting with each of the 9 elements of the matrix. The relationship of these independently constructed representations with those already available in the literature is compared and discussed. Further, the implications of these representations are explored for some of the CKM parameters such as |$\delta$|⁠ , J and |$\epsilon _k$|⁠. Interestingly, we find that the PDG representation which is equivalent to our first representation seems to be most appropriate to incorporate the hierarchy of the elements of the CKM matrix as well as to describe the related phenomenology. [ABSTRACT FROM AUTHOR]

Quark and lepton masses and mixings are considered in the framework of the microscopic model. The most general ansatz for the interactions among tetrons leads to a Hamiltonian HT$H_T$ involving Dzyaloshinskii‐Moriya (DM), Heisenberg and torsional isospin forces. Diagonalization of the Hamiltonian provides for 24 eigenvalues which are identified as the quark and lepton masses. While the masses of the third and second family arise from DM and Heisenberg type of isospin interactions, light family masses are related to torsional interactions among tetrons. Neutrino masses turn out to be special in that they are given in terms of tiny isospin non‐conserving DM, Heisenberg and torsional couplings. The approach not only leads to masses, but also allows to calculate the quark and lepton eigenstates, an issue, which is important for the determination of the CKM and PMNS mixing matrices. Compact expressions for the eigenfunctions of HT$H_T$ are given. The almost exact isospin conservation of the system dictates the form of the lepton states and makes them independent of all the couplings in HT$H_T$. As a consequence, a parameter‐free analytic expression for the PMNS matrix is derived which fits numerically all the measured matrix components. The formula includes a prediction of the leptonic Jarlskog invariant JPMNS=−0.0106$J_{PMNS}=-0.0106$. An outlook is given on the treatment of the CKM matrix. Quark and lepton masses and mixings are considered in the framework of the microscopic model. The most general ansatz for the interactions among tetrons leads to a Hamiltonian HT involving Dzyaloshinskii‐Moriya (DM), Heisenberg and torsional isospin forces. Diagonalization of the Hamiltonian provides for 24 eigenvalues which are identified as the quark and lepton masses. While the masses of the third and second family arise from DM and Heisenberg type of isospin interactions, light family masses are related to torsional interactions among tetrons. Neutrino masses turn out to be special in that they are given in terms of tiny isospin non‐conserving DM, Heisenberg and torsional couplings. The approach not only leads to masses, but also allows to calculate the quark and lepton eigenstates, an issue, which is important for the determination of the CKM and PMNS mixing matrices. Compact expressions for the eigenfunctions of HT are given. The almost exact isospin conservation of the system dictates the form of the lepton states and makes them independent of all the couplings in HT. As a consequence, a parameter‐free analytic expression for the PMNS matrix is derived which fits numerically all the measured matrix components. The formula includes a prediction of the leptonic Jarlskog invariant JPMNS = −0.0106. An outlook is given on the treatment of the CKM matrix. [ABSTRACT FROM AUTHOR]

The Standard Model does not constrain the form of the Yukawa matrices and thus the origin of fermion mass hierarchies and mixing pattern remains puzzling. On the other hand, there are intriguing relations between the quark masses and their weak mixing angles, such as the well-known relationship tan θ C = m d / m s for the Cabibbo angle, which may point towards specific textures of Yukawa matrices hypothesized by Harald Fritzsch at the end of the 70s. Though the original ansatz of Fritzsch is excluded by the experimental data, one can consider its minimal modification which consists in introducing an asymmetry between the 23 and 32 entries in the down-quark Yukawa matrix. We show that this structure is perfectly compatible with the present precision data on quark masses and CKM mixing matrix, and theoretically it can be obtained in the context of SU (5) model with inter-family SU (3) H symmetry. We also discuss some alternative approaches which could give a natural description of the fermion mass spectrum and weak mixing pattern. [ABSTRACT FROM AUTHOR]

The binary tetrahedral group ( T ′ ) has provided the most successful flavor symmetry in understanding simultaneously the three mixing angles both for quarks in the CKM matrix and for neutrinos in the PMNS matrix. One prediction, invariant under leptonic CP violation, relates the atmospheric and reactor neutrino mixings θ 3 2 and θ 1 3 , respectively. We study sedulously this relation using the latest neutrino data. It is natural to focus on the frustrating experimental octant ambiguity of θ 3 2 . We conclude that the flavor symmetry requires that θ 3 2 is in the second octant θ 3 2 > 4 5 ∘ , not in the first one θ 3 2 < 4 5 ∘ , and eagerly await experimental confirmation of this prediction. [ABSTRACT FROM AUTHOR]

We review the theory and phenomenology of isosinglet vector-like quarks (VLQs). In recent years, interest in VLQs has been increasing, due to their contributions to new physics effects that can be tested in experiments at LHC and High-Luminosity LHC. The similarities of models with isosinglet VLQs and the seesaw framework in the leptonic sector are pointed out. The existence of VLQs leads to flavour-changing neutral currents at tree level and deviations from unitarity of the CKM matrix, introducing rich phenomenological implications. These new effects are naturally suppressed by the masses of the new quarks, that are constrained to be above the electroweak scale. In addition, striking new effects can be achieved with the inclusion of an extra complex scalar singlet. Such a minimal extension of the SM can give rise to new sources of CP violation with profound theoretical implications, allowing for a solution to the strong CP problem and a possible explanation for the baryon asymmetry of the Universe. We list and explain strong motivations to consider this class of models. We also briefly review how models with VLQs can be matched to the SM effective field theory (SMEFT). A detailed analysis of flavour observables that can be affected by the presence of VLQs is presented. Current bounds from collider searches of VLQs are summarized. We point out that the discovery of VLQs can be within the reach of present or future colliders being planned. [ABSTRACT FROM AUTHOR]

While the third run of the Large Hadron Collider (LHC) is ongoing, the underlying theory that extends the Standard Model remains so far unknown. Left-Right Models (LRMs) introduce a new gauge sector, and can restore parity symmetry at high enough energies. If LRMs are indeed realized in nature, the mediators of the new weak force can be searched for in colliders via their direct production. We recast existing experimental limits from the LHC Run 2 and derive generic bounds on the masses of the heavy LRM gauge bosons. As a novelty, we discuss the dependence of the WR and ZR total width on the LRM scalar content, obtaining model-independent bounds within the specific realizations of the LRM scalar sectors analysed here. These bounds avoid the need to detail the spectrum of the scalar sector, and apply in the general case where no discrete symmetry is enforced. Moreover, we emphasize the impact on the WR production at LHC of general textures of the right-handed quark mixing matrix without manifest left-right symmetry. We find that the WR and ZR masses are constrained to lie above 2 TeV and 4 TeV, respectively. [ABSTRACT FROM AUTHOR]

The prospects are presented for precise measurements of the branching ratios of the purely leptonic B c + → τ + ν τ and B + → τ + ν τ decays at the Future Circular Collider (FCC). This work is focused on the hadronic τ + → π + π + π - ν ¯ τ decay in both B c + → τ + ν τ and B + → τ + ν τ processes. Events are selected with two Boosted Decision Tree algorithms to optimise the separation between the two signal processes as well as the generic hadronic Z decay backgrounds. The range of the expected precision for both signals are evaluated in different scenarios of non-ideal background modelling. This paper demonstrates, for the first time, that the B + → τ + ν τ decay can be well separated from both B c + → τ + ν τ and generic Z → b b ¯ processes in the FCC-ee collision environment and proposes the corresponding branching ratio measurement as a novel way to determine the CKM matrix element | V ub | . The theoretical impacts of both B + → τ + ν τ and B c + → τ + ν τ measurements on New Physics cases are discussed for interpretations in the generic Two-Higgs-doublet model and leptoquark models. [ABSTRACT FROM AUTHOR]

The η (′) -mesons in the quark-flavor basis are mixtures of two mesonic states | η q ⟩ = | u ¯ u + d ¯ d ⟩ / 2 and | η s ⟩ = | s ¯ s ⟩. In previous work, we have made a detailed study on the η s leading-twist distribution amplitude by using the D s + meson semileptonic decays. As a sequential work, in the present paper, we fix the η q leading-twist distribution amplitude by using the light-cone harmonic oscillator model for its wave function and by using the QCD sum rules within the QCD background field to calculate its moments. The input parameters of η q leading-twist distribution amplitude ϕ 2 ; η q at the initial scale μ 0 ∼ 1 GeV are fixed by using those moments. The QCD sum rules for the 0 th -order moment can also be used to fix the magnitude of η q decay constant, giving f η q = 0.141 ± 0.005 GeV. As an application of ϕ 2 ; η q , we calculate the transition form factors B (D) + → η (′) by using the QCD light-cone sum rules up to twist-4 accuracy and by including the next-to-leading order QCD corrections to the leading-twist part, and then fix the related CKM matrix element and the decay width for the semi-leptonic decays B (D) + → η (′) ℓ + ν ℓ. [ABSTRACT FROM AUTHOR]

In this paper, we carry out an investigation into the semileptonic decays D s + → K 0 ℓ + ν ℓ with ℓ = (e , μ) by employing the QCD light-cone sum rules approach. The vector transition form factor (TFF) f + D s + K 0 (q 2) for D s + → K 0 decay is calculated while considering its next-to-leading order contribution. Subsequently, we briefly introduce the twist-2, 3 kaon distribution amplitudes, which are calculated by using QCD sum rules within the framework of the background field theory. At the large recoil point, the TFF has f + D s + K 0 (0) = 0.692 − 0.026 + 0.027. Then, we extrapolate f + D s + K 0 (q 2) to the whole physical q 2 -region via the simplified z (q 2 , t) -series expansion, and the behavior of TFF f + D s + K 0 (q 2) is exhibited in the numerical results part, including the theoretical and experimental predictions for comparison. In addition, we compute the differential branching fraction B (D s + → K 0 ℓ + ν ℓ) with the electron and muon channels, which are expected to be B (D s + → K 0 e + ν e) = 3.379 − 0.275 + 0.301 × 10 − 3 and B (D s + → K 0 μ + ν μ) = 3.351 − 0.273 + 0.299 × 10 − 3 as well as contained other results for comparison. Our results show good agreement with the BESIII measurements and theoretical predictions. Furthermore, we present our prediction with respect to the CKM matrix element | V c d | by using the B (D s + → K 0 e + ν e) result from BESIII Collaboration, yielding | V c d | = 0.221 − 0.010 + 0.008. Finally, we provide the ratio between D s + → K 0 e + ν e and D s + → η e + ν e channels, i.e. R K 0 / η e = 0.144 − 0.020 + 0.028. [ABSTRACT FROM AUTHOR]

The Standard Model has no Flavor-Changing Neutral Current (FCNC) processes at the tree level. Therefore, processes featuring FCNC in new physics are tightly constrained by data. Typically, the lower bounds on the scale of new physics obtained from K − K ¯ or B − B ¯ mixing lie well above 10 TeV, surpassing the reach of current and future colliders. In this paper, we demonstrate, using a specific Z ′ model that features flavor-changing interactions, that such limits can be severely weakened by specific choices of the quark mixing matrices with no prejudice while maintaining the CKM matrix in agreement with the data. We highlight the valuable role of the often-overlooked D 0 mixing in deriving robust FCNC limits and show that the LHC and HL-LHC are promising probes for flavor-changing interactions mediated by a Z ′ boson. [ABSTRACT FROM AUTHOR]