Rendiconti Lincei, volume 34, issue 1, pages 37-57

New UTfit analysis of the unitarity triangle in the Cabibbo–Kobayashi–Maskawa scheme

Marcella Bona 1
Marco Ciuchini 2
Fabio Ferrari 4, 5
Enrico Franco 6
Vittorio Lubicz 2, 7
Guido Martinelli 6, 8
Davide Morgante 9, 10
Maurizio Pierini 11
LUCA SILVESTRINI 6
Silvano Simula 2
Achille Stocchi 12
Cecilia Tarantino 2, 7
Vincenzo Vagnoni 4
Mauro Valli 13
Ludovico Vittorio 14
Show full list: 16 authors
Publication typeJournal Article
Publication date2023-02-14
scimago Q2
wos Q2
SJR0.408
CiteScore4.1
Impact factor2.1
ISSN11206349, 17200776, 20374631
General Agricultural and Biological Sciences
General Environmental Science
General Earth and Planetary Sciences
Abstract
Flavour mixing and CP violation as measured in weak decays and mixing of neutral mesons are a fundamental tool to test the Standard Model and to search for new physics. New analyses performed at the LHC experiment open an unprecedented insight into the Cabibbo–Kobayashi–Maskawa metrology and new evidence for rare decays. Important progress has also been achieved in theoretical calculations of several hadronic quantities with a remarkable reduction of the uncertainties. This improvement is essential since previous studies of the Unitarity Triangle did show that possible contributions from new physics, if any, must be tiny and could easily be hidden by theoretical and experimental errors. Thanks to the experimental and theoretical advances, the Cabibbo–Kobayashi–Maskawa picture provides very precise Standard Model predictions through global analyses. We present here the results of the latest global Standard Model analysis performed by the UTfit collaboration including all the most updated inputs from experiments, lattice Quantum Chromo-Dynamics and phenomenological calculations.
Cirigliano V., Crivellin A., Hoferichter M., Moulson M.
2023-03-01 citations by CoLab: 37 Abstract  
Precision tests of first-row unitarity of the Cabibbo-Kobayashi-Maskawa matrix currently display two intriguing tensions, both at the $3\sigma$ level. First, combining determinations of $V_{ud}$ from superallowed $\beta$ decays with $V_{us}$ from kaon decays suggests a deficit in the unitarity relation. At the same time, a tension of similar significance has emerged between $K_{\ell 2}$ and $K_{\ell 3}$ decays. In this Letter, we point out that a measurement of the $K_{\mu3}/K_{\mu 2}$ branching fraction at the level of $0.2\%$ would have considerable impact on clarifying the experimental situation in the kaon sector, especially in view of tensions in the global fit to kaon data as well as the fact that the $K_{\mu2}$ channel is currently dominated by a single experiment. Such a measurement, as possible for example at NA62, would further provide important constraints on physics beyond the Standard Model, most notably on the role of right-handed vector currents.
Buras A.J.
European Physical Journal C scimago Q1 wos Q2 Open Access
2023-01-24 citations by CoLab: 26 PDF Abstract  
AbstractThe Standard Model (SM) does not contain by definition any new physics (NP) contributions to any observable but contains four CKM parameters which are not predicted by this model. We point out that if these four parameters are determined in a global fit which includes processes that are infected by NP and therefore by sources outside the SM, the resulting so-called SM contributions to rare decay branching ratios cannot be considered as genuine SM contributions to the latter. On the other hand genuine SM predictions, that are free from the CKM dependence, can be obtained for suitable ratios of the K and B rare decay branching ratios to $$\Delta M_s$$ Δ M s , $$\Delta M_d$$ Δ M d and $$|\varepsilon _K|$$ | ε K | , all calculated within the SM. These three observables contain by now only small hadronic uncertainties and are already well measured so that rather precise SM predictions for the ratios in question can be obtained. In this context the rapid test of NP infection in the $$\Delta F=2$$ Δ F = 2 sector is provided by a $$|V_{cb}|-\gamma $$ | V cb | - γ plot that involves $$\Delta M_s$$ Δ M s , $$\Delta M_d$$ Δ M d , $$|\varepsilon _K|$$ | ε K | , and the mixing induced CP-asymmetry $$S_{\psi K_S}$$ S ψ K S . As with the present hadronic matrix elements this test turns out to be negative, assuming negligible NP infection in the $$\Delta F=2$$ Δ F = 2 sector and setting the values of these four observables to the experimental ones, allows to obtain SM predictions for all K and B rare decay branching ratios that are most accurate to date and as a byproduct to obtain the full CKM matrix on the basis of $$\Delta F=2$$ Δ F = 2 transitions alone. Using this strategy we obtain SM predictions for 26 branching ratios for rare semileptonic and leptonic K and B decays with the $$\mu ^+\mu ^-$$ μ + μ - pair or the $$\nu {\bar{\nu }}$$ ν ν ¯ pair in the final state. Most interesting turn out to be the anomalies in the low $$q^2$$ q 2 bin in $$B^+\rightarrow K^+\mu ^+\mu ^-$$ B + → K + μ + μ - ($$5.1\sigma $$ 5.1 σ ) and $$B_s\rightarrow \phi \mu ^+\mu ^-$$ B s → ϕ μ + μ - ($$4.8\sigma $$ 4.8 σ ).
Bazavov A., DeTar C.E., Du D., El-Khadra A.X., Gámiz E., Gelzer Z., Gottlieb S., Heller U.M., Kronfeld A.S., Laiho J., Mackenzie P.B., Simone J.N., Sugar R., Toussaint D., Van de Water R.S., et. al.
European Physical Journal C scimago Q1 wos Q2 Open Access
2022-12-16 citations by CoLab: 46 PDF Abstract  
AbstractWe present the first unquenched lattice-QCD calculation of the form factors for the decay $$B\rightarrow D^*\ell \nu $$ B → D ∗ ℓ ν at nonzero recoil. Our analysis includes 15 MILC ensembles with $$N_f=2+1$$ N f = 2 + 1 flavors of asqtad sea quarks, with a strange quark mass close to its physical mass. The lattice spacings range from $$a\approx 0.15$$ a ≈ 0.15 fm down to 0.045 fm, while the ratio between the light- and the strange-quark masses ranges from 0.05 to 0.4. The valence b and c quarks are treated using the Wilson-clover action with the Fermilab interpretation, whereas the light sector employs asqtad staggered fermions. We extrapolate our results to the physical point in the continuum limit using rooted staggered heavy-light meson chiral perturbation theory. Then we apply a model-independent parametrization to extend the form factors to the full kinematic range. With this parametrization we perform a joint lattice-QCD/experiment fit using several experimental datasets to determine the CKM matrix element $$|V_{cb}|$$ | V cb | . We obtain $$\left| V_{cb}\right| = (38.40 \pm 0.68_{\text {th}} \pm 0.34_{\text {exp}} \pm 0.18_{\text {EM}})\times 10^{-3}$$ V cb = ( 38.40 ± 0 . 68 th ± 0 . 34 exp ± 0 . 18 EM ) × 10 - 3 . The first error is theoretical, the second comes from experiment and the last one includes electromagnetic and electroweak uncertainties, with an overall $$\chi ^2\text {/dof} = 126/84$$ χ 2 /dof = 126 / 84 , which illustrates the tensions between the experimental data sets, and between theory and experiment. This result is in agreement with previous exclusive determinations, but the tension with the inclusive determination remains. Finally, we integrate the differential decay rate obtained solely from lattice data to predict $$R(D^*) = 0.265 \pm 0.013$$ R ( D ∗ ) = 0.265 ± 0.013 , which confirms the current tension between theory and experiment.
Brod J., Kvedaraitė S., Polonsky Z., Youssef A.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2022-12-05 citations by CoLab: 9 PDF Abstract  
Abstract We calculate the leading-logarithmic and next-to-leading-logarithmic electroweak corrections to the charm-top-quark contribution to the effective |∆S| = 2 Lagrangian, relevant for the parameter ϵK. We find that these corrections lead to a −0.5% shift in the corresponding Wilson coefficient. Moreover, our calculation removes an implicit ambiguity in the standard-model prediction of ϵK, by fixing the renormalization scheme of the electroweak input parameters.
Martinelli G., Simula S., Vittorio L.
European Physical Journal C scimago Q1 wos Q2 Open Access
2022-12-01 citations by CoLab: 24 PDF Abstract  
AbstractIn this work we apply the Dispersive Matrix (DM) method of Di Carlo et al. (Phys Rev D 104:054502, 2021) and Martinelli et al. (Phys Rev D 105:034503, 2022) to the lattice computations of the Form Factors (FFs) entering the semileptonic $$B \rightarrow D^* \ell \nu _\ell $$ B → D ∗ ℓ ν ℓ decays, recently produced by the FNAL/MILC Collaborations (Fermilab Lattice, MILC collaboration, Semileptonic form factors for $$B \rightarrow D^*\ell \nu $$ B → D ∗ ℓ ν at nonzero recoil from 2 + 1-flavor lattice QCD. arXiv:2105.14019) at small, but non-vanishing values of the recoil variable ($$w-1$$ w - 1 ). Thanks to the DM method we obtain the FFs in the whole kinematical range accessible to the decay in a completely model-independent and non-perturbative way, implementing exactly both unitarity and kinematical constraints. Using our theoretical bands of the FFs we extract $$\vert V_{cb} \vert $$ | V cb | from the experimental data and compute the theoretical value of $$R(D^*)$$ R ( D ∗ ) . Our final result for $$\vert V_{cb} \vert $$ | V cb | reads $$\vert V_{cb} \vert = (41.3 \pm 1.7) \cdot 10^{-3}$$ | V cb | = ( 41.3 ± 1.7 ) · 10 - 3 , compatible with the most recent inclusive estimate at the $$0.5\sigma $$ 0.5 σ level. Moreover, we obtain the pure theoretical value $$R(D^*) = 0.275 \pm 0.008$$ R ( D ∗ ) = 0.275 ± 0.008 , which is compatible with the experimental world average at the $$\sim 1.3 \sigma $$ ∼ 1.3 σ level.
Martinelli G., Naviglio M., Simula S., Vittorio L.
Physical Review D scimago Q1 wos Q1
2022-11-08 citations by CoLab: 17 Abstract  
In addition to the well-known $B\ensuremath{\rightarrow}{D}^{(*)}\ensuremath{\ell}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ decays, semileptonic ${B}_{s}\ensuremath{\rightarrow}{D}_{s}^{(*)}\ensuremath{\ell}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ processes offer the possibility to determine the Cabibbo-Kobayashi-Maskawa matrix element $|{V}_{cb}|$. We implement the dispersive matrix approach to describe the hadronic form factors (FFs) for the ${B}_{s}\ensuremath{\rightarrow}{D}_{s}^{(*)}$ transition in the whole kinematical range, starting from recent lattice QCD computations at large values of the four-momentum transfer. We extract $|{V}_{cb}|$ from the experimental data, obtaining $|{V}_{cb}|\ifmmode\times\else\texttimes\fi{}{10}^{3}=(41.7\ifmmode\pm\else\textpm\fi{}1.9)$ from ${B}_{s}\ensuremath{\rightarrow}{D}_{s}\ensuremath{\ell}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ and $|{V}_{cb}|\ifmmode\times\else\texttimes\fi{}{10}^{3}=(40.7\ifmmode\pm\else\textpm\fi{}2.4)$ from ${B}_{s}\ensuremath{\rightarrow}{D}_{s}^{*}\ensuremath{\ell}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ decays. After averaging with the values of $|{V}_{cb}|$ obtained from the $B\ensuremath{\rightarrow}{D}^{(*)}$ channels [G. Martinelli et al., Phys. Rev. D 105, 034503 (2022); G. Martinelli et al., arXiv:2109.15248.], we get $|{V}_{cb}|\ifmmode\times\else\texttimes\fi{}{10}^{3}=(41.2\ifmmode\pm\else\textpm\fi{}0.8)$, which is compatible with the most recent inclusive estimate $|{V}_{cb}{|}_{\mathrm{incl}}\ifmmode\times\else\texttimes\fi{}{10}^{3}=42.16\ifmmode\pm\else\textpm\fi{}0.50$ [M. Bordone et al., Phys. Lett. B 822, 136679 (2021).] at the $1\ensuremath{\sigma}$ level. In addition we test the lepton flavor universality by computing the $\ensuremath{\tau}/\ensuremath{\ell}$ ratios of the total decay rates (where $\ensuremath{\ell}$ is a light lepton), obtaining $R({D}_{s})=0.298(5)$ and $R({D}_{s}^{*})=0.250(6)$. We also address the issue of the $SU(3{)}_{F}$ symmetry breaking by comparing the hadronic FFs entering the semileptonic $B\ensuremath{\rightarrow}{D}^{(*)}$ and ${B}_{s}\ensuremath{\rightarrow}{D}_{s}^{(*)}$ channels.
Bernlochner F., Fael M., Olschewsky K., Persson E., van Tonder R., Vos K.K., Welsch M.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2022-10-10 citations by CoLab: 43 PDF Abstract  
We present the first determination of Vcb from inclusive $$ B\to {X}_c \ell {\overline{v}}_{\ell} $$ using moments of the dilepton invariant mass, q2. These moments are reparametrization invariant quantities and depend on a reduced set of non-perturbative parameters. This reduced set of parameters opens a new path to extract these parameters up to $$ 1/{m}_b^4 $$ purely from data and can potentially reduce the uncertainty on Vcb. In this paper, we present our first determination of Vcb using this method. Combining the recent measurements of q2 moments by Belle and Belle II, our default fit gives |Vcb| = (41.69±0.63)·10−3. This result presents an important independent cross check of, and is consistent with, the previous state-of-the-art inclusive determinations using lepton energy and hadronic invariant mass moments.
Aoki Y., Blum T., Colangelo G., Collins S., Morte M.D., Dimopoulos P., Dürr S., Feng X., Fukaya H., Golterman M., Gottlieb S., Gupta R., Hashimoto S., Heller U.M., Herdoiza G., et. al.
European Physical Journal C scimago Q1 wos Q2 Open Access
2022-10-04 citations by CoLab: 370 PDF Abstract  
We review lattice results related to pion, kaon, D-meson, B-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More specifically, we report on the determination of the light-quark masses, the form factor $$f_+(0)$$ arising in the semileptonic $$K \rightarrow \pi $$ transition at zero momentum transfer, as well as the decay constant ratio $$f_K/f_\pi $$ and its consequences for the CKM matrix elements $$V_{us}$$ and $$V_{ud}$$ . Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of $$SU(2)_L\times SU(2)_R$$ and $$SU(3)_L\times SU(3)_R$$ Chiral Perturbation Theory. We review the determination of the $$B_K$$ parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for $$m_c$$ and $$m_b$$ as well as those for the decay constants, form factors, and mixing parameters of charmed and bottom mesons and baryons. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant $$\alpha _s$$ . We consider nucleon matrix elements, and review the determinations of the axial, scalar and tensor bilinears, both isovector and flavor diagonal. Finally, in this review we have added a new section reviewing determinations of scale-setting quantities.
Colquhoun B., Hashimoto S., Kaneko T., Koponen J.
Physical Review D scimago Q1 wos Q1
2022-09-06 citations by CoLab: 12 Abstract  
Using a fully relativistic lattice fermion action, we compute the form factors of the semileptonic decay $B\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\ell}\ensuremath{\nu}$, which is required for the determination of the Cabibbo-Kobayashi-Maskawa matrix element $|{V}_{ub}|$. We employ the M\"obius domain-wall fermion formalism for the generation of lattice ensembles with $2+1$ sea quark flavors as well as for the valence heavy and light quarks. We compute the form factors at various values of the lattice spacing and multiple light and heavy quark masses, and extrapolate the results to the physical point. We combine our lattice results with the available experimental data to obtain $|{V}_{ub}|=(3.93\ifmmode\pm\else\textpm\fi{}0.41)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$.
Workman R.L., Burkert V.D., Crede V., Klempt E., Thoma U., Tiator L., Agashe K., Aielli G., Allanach B.C., Amsler C., Antonelli M., Aschenauer E.C., Asner D.M., Baer H., Banerjee S., et. al.
2022-08-08 citations by CoLab: 2576 PDF Abstract  
Abstract The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,143 new measurements from 709 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on Machine Learning, and one on Spectroscopy of Light Meson Resonances. The Review is divided into two volumes. Volume 1 includes the Summary Tables and 97 review articles. Volume 2 consists of the Particle Listings and contains also 23 reviews that address specific aspects of the data presented in the Listings. The complete Review (both volumes) is published online on the website of the Particle Data Group (pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print, as a web version optimized for use on phones, and as an Android app.
Martinelli G., Simula S., Vittorio L.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2022-08-02 citations by CoLab: 27 PDF Abstract  
The Cabibbo-Kobayashi-Maskawa (CKM) matrix element ∣Vub∣ is obtained from exclusive semileptonic B → πℓνℓ and Bs → Kℓνℓ decays adopting the unitarity-based dispersion matrix approach for the determination of the hadronic form factors (FFs) in the whole kinematical range. We use lattice computations of the relevant susceptibilities and of the FFs in the large-q2 regime in order to derive their behavior in the low-q2 region without assuming any specific momentum dependence and without constraining their shape using experimental data. Then, we address the extraction of |Vub| from the experimental data, obtaining |Vub| = (3.62 ± 0.47) · 10−3 from B → π and |Vub| = (3.77 ± 0.48) · 10−3 from Bs → K, which after averaging yield |Vub| = (3.69 ± 0.34) · 10−3. These results are compatible with the most recent inclusive value |Vub|incl = 4.13 (26) · 10−3 at the 1σ level. We also present purely theoretical estimates of the ratio of the τ/μ decay rates $$ {R}_{\pi (K)}^{\tau /\mu } $$ , the normalized forward-backward asymmetry $$ {\overline{\mathcal{A}}}_{FB}^{\ell, \pi (K)} $$ and the normalized lepton polarization asymmetry $$ {\overline{\mathcal{A}}}_{\mathrm{polar}}^{\ell, \pi (K)} $$ .
Seng C., Galviz D., Gorchtein M., Meißner U.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2022-07-13 citations by CoLab: 22 PDF Abstract  
We fill up the missing piece in our own re-analysis of the long-distance electromagnetic radiative corrections to semileptonic kaon decays by performing a rigorous study in the K → πμ+νμ(γ) channels. With appropriate experimental and lattice inputs, we achieve a precision level of 10−4 in these channels. This is comparable to our previous analysis in the K → πe+νe(γ) channels. With this new result, we present an updated global analysis to extract the Standard Model parameter |Vus| from semileptonic kaon decays. We obtain |Vus| = 0.22308(55) and 0.22356(73), using the lattice average of the K0 → π− transition form factor at Nf = 2 + 1 + 1 and Nf = 2 + 1, respectively.
Aaij R., Abdelmotteleb A. ., Abellán Beteta C., Abudinén F., Ackernley T., Adeva B., Adinolfi M., Afsharnia H., Agapopoulou C., Aidala C. ., Aiola S., Ajaltouni Z., Akar S., Albrecht J., Alessio F., et. al.
Physical Review Letters scimago Q1 wos Q1 Open Access
2022-05-11 citations by CoLab: 59 Abstract  
Two new $B$ meson decays are observed and used to probe lepton universality, with results fitting the overall picture of a persistent but not yet compelling deviation from the Standard Model of particle physics.
Giannakopoulou A.S., Meade P., Valli M.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2025-02-12 citations by CoLab: 0 PDF Abstract  
Abstract The coupling of the Higgs boson to first and second generation fermions has yet to be measured experimentally. There still could be very large deviations in these couplings, as the origin of flavor is completely unknown. Nevertheless, if Yukawa couplings are modified, especially for light generations, there are generically strong constraints from flavor-changing neutral currents (FCNCs). Therefore, it is imperative to understand whether there exists viable UV physics consistent with current data that motivates future Higgs coupling probes. In particular, the charm-quark Yukawa is the next quark coupling that could be measured at the LHC if it is a few times larger than the SM and compatible with flavor data. This is difficult to achieve in the context of standard ansatz such as Minimal Flavor Violation. In this paper we show that within the framework of Spontaneous Flavor Violation (SFV), using a Two Higgs Doublet Model as an example, the Higgs can be sufficiently charming that new LHC probes are relevant. In this charming region, we show that new Higgs states near the EW scale with large couplings to quarks are required, providing complementary observables or new constraints on the SM Yukawa couplings. The down-type SFV mechanism enabling the suppression of FCNCs also allows for independent modifications to the up-quark Yukawa coupling, which we explore in detail as well.
Coutinho A.M., Karan A., Miralles V., Pich A.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2025-02-11 citations by CoLab: 0 PDF Abstract  
Abstract In this article we study the possibility that neutral and charged scalars lighter than the 125 GeV Higgs boson might exist within the framework of the $$ \mathcal{CP} $$ CP -conserving Aligned-two-Higgs-doublet model. Depending on which new scalar (scalars) is (are) light, seven different scenarios may be considered. Using the open-source code HEPfit, which relies on Bayesian statistics, we perform global fits for all seven light-mass scenarios. The constraints arising from vacuum stability, perturbativity, electroweak precision observables, flavour observables, Higgs signal strengths, and direct-detection results at the LEP and the LHC are taken into account. Reinterpreted data from slepton searches are considered too. It turns out that the seven scenarios contain sizeable regions of their parameter space compatible with all current data. Although not included in the global fits, the possible implications of (g − 2) μ are also addressed.
Bordone M., Jüttner A.
European Physical Journal C scimago Q1 wos Q2 Open Access
2025-02-03 citations by CoLab: 0 PDF Abstract  
Abstract We present an analysis of the exclusive semileptonic decay $$B\rightarrow D^*\ell \bar{\nu }_\ell $$ B → D ∗ ℓ ν ¯ ℓ based on the Belle and Belle II data made public in 2023, combined with recent lattice-QCD calculations of the hadronic transition form factors by FNAL/MILC, HPQCD and JLQCD. We also consider a new combination of the Belle and Belle II data sets by HFLAV. The analysis is based on the form-factor parameterisation by Boyd–Grinstein–Lebed (BGL), using Bayesian and frequentist statistics, for which we discuss novel strategies. We compare the results of an analysis where the BGL parameterisation is fit only to the lattice data with those from a simultaneous fit to lattice and experiment, and discuss the resulting predictions for the CKM-matrix element $${|V_{cb}|}$$ | V cb | , as well as other phenomenological observables, such as $$R^{\tau /\mu }(D^*)$$ R τ / μ ( D ∗ ) . We find tensions when comparing analyses based on different combinations of experimental or theoretical input, requiring the introduction of a systematic error for some of our results.
Van Loi D., Duy N.T., Nam C.H., Van Dong P.
European Physical Journal C scimago Q1 wos Q2 Open Access
2025-01-30 citations by CoLab: 0 PDF Abstract  
Abstract Assuming fundamental fermions possess a new Abelian gauge charge that depends on flavors of both quark and lepton, we obtain a simple extension of the Standard Model, which reveals some new physics insights. The new gauge charge anomaly cancellation not only explains the existence of just three fermion generations as observed but also requires the presence of a unique right-handed neutrino $$\nu _R$$ ν R with a non-zero new gauge charge. Further, the new gauge charge breaking supplies a residual matter parity, under which the fundamental fermions and $$\nu _R$$ ν R are even, whereas a right-handed neutrino $$N_R$$ N R without the new charge is odd. Consequently, light neutrino masses in our model are generated from the tree-level type-I seesaw mechanism induced by $$\nu _R$$ ν R and from the one-loop scotogenic contribution accommodated by potential dark matter candidates, $$N_R$$ N R and dark scalars, odd under the matter parity. We examine new physics phenomena related to the additional gauge boson, which could be observed at colliders. We analyze the constraints imposed on our model by current experimental limits on neutrino masses, neutral meson oscillations, B-meson decays, and charged lepton flavor violating processes. We also investigate the potential dark matter candidates by considering relic density and direct detection.
Zhang S., Qiao C.
Physical Review D scimago Q1 wos Q1
2024-12-27 citations by CoLab: 0 Abstract  
Recent experimental progress on baryonic rare decays has spurred a deeper investigation on flavor-changing neutral current transitions in the baryon sector. Within the framework of QCD sum rules, we derive a complete set of form factors for the Λc→p process in the large recoil region and use the z-series parametrization to extrapolate them across the full physical range. Employing these form factors and flavor symmetries, we compute branching fractions for the decays Λc→pe+e− and Λc→pμ+μ−, as well as for rare Ξc decay modes. We examine as well the new physics effects through specific angular observables such as the lepton forward-backward asymmetry and the fraction of longitudinally polarized dileptons. Results indicate that new physics models may be testified in baryonic rare decays, with immense data collected in running and future colliders. Published by the American Physical Society 2024
Lunghi E., Soni A.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2024-12-12 citations by CoLab: 0 PDF Abstract  
Abstract We use vector meson dominance to calculate non-perturbative contributions to the branching ratio of the rare decay $$ {K}^{\pm}\to {\pi}^{\pm}\nu \overline{\nu} $$ K ± → π ± ν ν ¯ stemming from matrix elements involving up-quark loops. The importance of this observable as well as of K0 → π0l+l− and of the direct CP violation parameter $$ {\epsilon}_K^{\prime } $$ ϵ K ′ is then discussed in the context of a Unitarity Triangle sqtudy based on Kaon sector observables only.
Marzocca D., Nardecchia M., Stanzione A., Toni C.
European Physical Journal C scimago Q1 wos Q2 Open Access
2024-11-25 citations by CoLab: 1 PDF Abstract  
AbstractWe study the implications of the observed excess in $$B^+ \rightarrow K^+ \nu \bar{\nu }$$ B + → K + ν ν ¯ under the assumption of Rank-One Flavour Violation, i.e. that New Physics couples to a single specific direction in flavour space. By varying this direction we perform analyses at the level of the low-energy EFT, the SMEFT, and with explicit mediators such as leptoquarks and colorless vectors ($$Z^\prime $$ Z ′ and $$V^\prime $$ V ′ ). We study correlations with other flavour, electroweak and collider observables, finding that the most interesting ones are with $$K \rightarrow \pi \nu \bar{\nu }$$ K → π ν ν ¯ , $$B_s \rightarrow \mu ^+ \mu ^-$$ B s → μ + μ - , meson mixing and the LHC searches in $$\tau ^+ \tau ^-$$ τ + τ - high-energy tails. Among the various mediators, the scalar leptoquarks $$\tilde{R}_2$$ R ~ 2 and $$S_1$$ S 1 offer the best fits of the Belle-II excess, while being consistent with the other bounds. On the other hand, colorless vectors are strongly constrained by meson mixing and resonance searches in $$p p \rightarrow \tau ^+ \tau ^-$$ p p → τ + τ - . In all cases we find that a flavour alignment close to the third generation is generically preferred.
Gustafson E.J., Herren F., Van de Water R.S., van Tonder R., Wagman M.L.
Physical Review D scimago Q1 wos Q1
2024-11-18 citations by CoLab: 1 Abstract  
We introduce a new parametrization of B→Dπℓν form factors using a partial-wave expansion and derive bounds on the series coefficients using analyticity and unitarity. This is the first generalization of the model-independent formalism developed by Boyd, Grinstein, and Lebed for B→Dℓν to semileptonic decays with multihadron final states, and enables data-driven form-factor determinations with robust, systematically improvable uncertainties. Using this formalism, we extract the form-factor parameters for B→D2*(→Dπ)ℓν decays in a model-independent way from fits of data from the Belle Experiment. We find that the semileptonic data are compatible with the presence of two poles in the Dπ S-wave channel, which is the scenario preferred by nonleptonic decays and unitarized chiral perturbation theory. Published by the American Physical Society 2024
Sabir M., Mansha A., Li T., Wang Z.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2024-10-31 citations by CoLab: 1 PDF Abstract  
Abstract Recently, the complete landscape of three-family supersymmetric Pati-Salam models from intersecting D6-branes on a type IIA $$ {\mathbbm{T}}^6/\left({\mathbb{Z}}_2\times {\mathbb{Z}}_2\right) $$ T 6 / ℤ 2 × ℤ 2 orientifold has been enumerated consisting of 33 independent models with distinct gauge coupling relations at the string scale. Here, we study the phenomenology of all such models by providing the detailed particle spectra and the analysis of the possible 3-point and the 4-point Yukawa interactions in order to accommodate all standard-model fermion masses and mixings. We find that only 17 models contain viable Yukawa textures to explain quarks masses, charged-leptons’ masses, neutrino-masses, quarks’ mixings and leptons’ mixings. These viable models split into four classes, viz. a single model with 3 Higgs fields from the bulk and sixteen models with either 6, 9 or 12 Higgs from the $$ \mathcal{N} $$ N = 2 sector. The models perform successively better with the increasing number of Higgs pairs. Remarkably, the class of models with 12 Higgs naturally predicts the Dirac-type neutrino masses in normal ordering consistent with both the experimental constraints as well as the bounds from the swampland program.
Adachi I., Aggarwal L., Aihara H., Akopov N., Aloisio A., Al Said S., Anh Ky N., Asner D.M., Atmacan H., Aushev V., Aversano M., Ayad R., Babu V., Bae H., Bahinipati S., et. al.
Journal of High Energy Physics scimago Q2 wos Q1 Open Access
2024-10-22 citations by CoLab: 1 PDF Abstract  
Abstract We report a determination of the CKM angle ϕ3, also known as γ, from a combination of measurements using samples of up to 711 fb−1 from the Belle experiment and up to 362 fb−1 from the Belle II experiment. We combine results from analyses of B+→ DK+, B+→ Dπ+, and B+→ D*K+ decays, where D is an admixture of D0 and $$ {\overline{D}}^0 $$ D ¯ 0 mesons, in a likelihood fit to obtain ϕ3 = (75.2 ± 7.6)°. We also briefly discuss the interpretation of this result.
Bečirević D., Jaffredo F., Pinheiro J. ., Sumensari O.
Physical Review D scimago Q1 wos Q1
2024-10-07 citations by CoLab: 0 Abstract  
We discuss the exclusive lepton flavor violating (LFV) decays modes based on b→dℓiℓj and b→sℓiℓj by considering the ground state mesons and baryons. After spelling out the expressions for such decay rates in a low energy effective theory which includes generic contributions arising from physics beyond the Standard Model, we show that the experimental bounds on meson decays can be used to bound the corresponding modes involving baryons. We find, for example, B(Λb→Λμτ)≲4×10−5. We also consider two specific models and constrain the relevant LFV couplings by using the low energy observables. In the first model, we assume the Higgs mediated LFV and find the resulting decay rates to be too small to be experimentally detectable. We also emphasize that the regions favored by the bounds B(h→μτ)Atlas and B(h→eτ)Atlas are not compatible with B(μ→eγ)MEG to 1σ. In the second model, we assume LFV mediated by a heavy Z′ boson and find that the corresponding b-hadron branching fractions can be O(10−6), thus possibly within experimental reach at LHCb and Belle II. Published by the American Physical Society 2024
Chen F., Wen Q., Xu F.
European Physical Journal C scimago Q1 wos Q2 Open Access
2024-10-07 citations by CoLab: 3 PDF Abstract  
AbstractThe recent measurement of $$\mathcal {B}(B^+\rightarrow K^+\nu \bar{\nu })$$ B ( B + → K + ν ν ¯ ) by Belle-II reveals a $$2.8~\sigma $$ 2.8 σ deviation from the Standard Model (SM) prediction. Combining this with a prior Belle measurement of $$\mathcal {B}(B^{0}\rightarrow K^{*0}\nu \bar{\nu })$$ B ( B 0 → K ∗ 0 ν ν ¯ ) , the upper bound of the ratio $$\mathcal {B}(B^{0}\rightarrow K^{*0}\nu \bar{\nu })/\mathcal {B}(B^+\rightarrow K^+\nu \bar{\nu })$$ B ( B 0 → K ∗ 0 ν ν ¯ ) / B ( B + → K + ν ν ¯ ) is notably smaller than the SM prediction. In this work, tensions are solved within the framework of Standard Model effective field theory (SMEFT). The flavor-changing-neutral-current (FCNC) and charged-current observables of either down-type ($$b\rightarrow s\nu \bar{\nu }$$ b → s ν ν ¯ , $$b\rightarrow s\ell ^+\ell ^-$$ b → s ℓ + ℓ - , and $$b\rightarrow u_i\ell \bar{\nu }$$ b → u i ℓ ν ¯ ) or up-type ($$u_j\rightarrow u_i\nu \bar{\nu }$$ u j → u i ν ν ¯ , $$u_j\rightarrow u_i\ell ^+\ell ^-$$ u j → u i ℓ + ℓ - , and $$u_j\rightarrow s\ell \bar{\nu }$$ u j → s ℓ ν ¯ ) processes, described by low-energy effective field theory (LEFT) operators, are interconnected by a minimal set of four SMEFT operators at the electroweak scale. Subsequently, we obtain the latest ranges of Wilson coefficients for these four operators through a global fit that accommodates flavor anomalies such as $$R_{K^{(*)}}$$ R K ( ∗ ) , $$R_{D^{(*)}}$$ R D ( ∗ ) , and $$\mathcal {B}(B\rightarrow K^{(*)}\nu \bar{\nu })$$ B ( B → K ( ∗ ) ν ν ¯ ) . Our findings reveal that predictions for $$\mathcal {B}(B^+\rightarrow \tau ^+\nu _\tau )$$ B ( B + → τ + ν τ ) and $$\mathcal {B}(D_s^+\rightarrow \tau ^+\nu _\tau )$$ B ( D s + → τ + ν τ ) align well with measured values from Belle and BESIII, based on the fitted coefficients. The predicted branching fraction for $$B^0\rightarrow K^{*0}\nu \bar{\nu }$$ B 0 → K ∗ 0 ν ν ¯ is $$(1.42\pm 0.74)\times 10^{-5}$$ ( 1.42 ± 0.74 ) × 10 - 5 , closely approaching the current experimental upper limit. Anticipation surrounds the rare decay $$B_s\rightarrow \tau ^+ \tau ^-$$ B s → τ + τ - , expected in the near future with a branching fraction on the order of $$10^{-4}$$ 10 - 4 .

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