LHCb Data Research Articles

Data-driven analysis of the beauty hadron production in pp collisions at the LHC with Bayesian unfolding

Heavy flavour production in proton-proton (pp) collisions provides insights into the fundamental properties of Quantum Chromodynamics (QCD). Beauty hadron production measurements are widely performed through indirect approaches based on their inclusive decay modes. A Bayesian unfolding data-driven analysis of the ALICE and LHCb data was performed in this study, which recovers the full kinematic information of the beauty hadrons via different inclusive decay channels. The corresponding beauty hadron production cross sections obtained after the Bayesian unfolding are found to be consistent within their uncertainties. The weighted average open beauty production cross sections are presented as a function of the transverse momentum and rapidity in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 5.02 TeV and s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV, respectively. The pT-integrated open beauty production dσ/dy and the total bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ extrm{b}\\overline{\ extrm{b}} $$\\end{document} cross section σbb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\sigma}_{\ extrm{b}\\overline{\ extrm{b}}} $$\\end{document} are also reported. The precision of these results significantly improves upon worldwide measurements, providing valuable validation and constraints on mechanisms of heavy flavour production in pp collisions at the LHC energies.

Asymmetric intrinsic charm in the nucleon and its implications for the D0 production in the LHCb p+Ne20 fixed-target experiment

Recent results indicate that charm quarks are intrinsic components of the proton wave function, and that the charm and anticharm distributions for a given value of the Bjorken-x variable can be different. In this paper, we will investigate the impact of this asymmetric intrinsic charm on the production of D0 and D¯0 mesons for fixed target p+Ne20 collisions at the LHCb. In our calculations, we include the contribution of the gluon-gluon fusion, gluon-charm and recombination processes and assume distinct models for the treatment of the intrinsic charm component. We demonstrate that the presence of an intrinsic charm improves the description of the current data for the rapidity and transverse momentum distributions of D mesons. However, such models are not able to describe the LHCb data for the D0−D¯0 asymmetry at large transverse momentum, which point out that the description of the intrinsic charm needs to be improved and/or new effects should be taken into account in the production of heavy mesons at forward rapidities in fixed-target collisions. Published by the American Physical Society 2024

How viable is a QCD axion near 10 MeV?

There has been an attempt to revive the visible QCD axion at the 10 MeV scale assuming that it exclusively couples to the first-generation quarks and the electron. This variant of the QCD axion is claimed to remain phenomenologically viable, partly due to a clever model construction that induces tree-level pion-phobia and exploits uncertainties inherent in the chiral perturbation theory. We confront this model with the cosmological domain wall problem, the quality issue and constraints arising from the electron electric dipole moment. It is also pointed out that the gluon loop-generated axion-top coupling can provide a very large contribution to rare B-meson decays, such that the present LHCb data for B0 → K*0e+e− rule out the model for the axion mass larger than 30 MeV. There is a strong motivation for pushing the experimental analysis of B → K(*)e+e− to a lower e+e− invariant mass window, which will conclusively determine the fate of the model, as its contribution to this branching ratio significantly exceeds the Standard Model prediction.

Scalar and tensor mesons in dd̄, ss̄ and gg→f0, f2

LHCb data on [Formula: see text], [Formula: see text] and [Formula: see text] are fitted in a coupled-channel analysis jointly with data on radiative [Formula: see text] decays, [Formula: see text] elastic scattering and further data sets. Branching ratios for [Formula: see text] are determined and compared to those from radiative [Formula: see text] decays. Above 1500[Formula: see text]MeV, only little intensity is observed in [Formula: see text] decays. In radiative [Formula: see text] decays, the intensities are strong and peak at 1865[Formula: see text]MeV in the scalar wave and at 2210[Formula: see text]MeV in the tensor wave. This pattern is interpreted as further support for the glueball interpretation of [Formula: see text] and of [Formula: see text].

Detector-embedded reconstruction of complex primitives using FPGAs

The slowdown of Moore’s law and the growing requirements of future HEP experiments with ever-increasing data rates pose important computational challenges for data reconstruction and trigger systems, encouraging the exploration of new computing methodologies. In this work we discuss a FPGA-based tracking system, relying on a massively parallel pattern recognition approach, inspired by the processing of visual images by the natural brain (“retina architecture”). This method allows a large efficiency of utilisation of the hardware, low power consumption and very low latencies. Based on this approach, a device has been designed within the LHCb Upgrade-II project, with the goal of performing track reconstruction in the forward acceptance region in real-time during the upcoming Run 4 of the LHC. This innovative device will perform track reconstruction before the event-building, in a short enough time to provide pre-reconstructed tracks (“primitives”) transparently to the processor farm, as if they had been generated directly by the detector. This allows significant savings in higher-level computing resources, enabling handling higher luminosities than otherwise possible. The feasibility of the project is backed up by the results of tests performed on a realistic hardware prototype, that has been opportunistically processing actual LHCb data in parallel with the regular DAQ in the LHC Run 3.

D0 meson production in pp collisions at large Qs2

The impact of the nonlinear effects in the QCD on the observables is directly related to the magnitude of the saturation scale Qs, which is predicted to increase with the energy, rapidity, and multiplicity. In this paper, we investigate the D0 meson production in pp collisions at forward rapidities and/or high multiplicities considering the color glass condensate (CGC) formalism and the solutions of the running coupling Balitsky-Kovchegov equation. The contributions of gluon- and charm-initiated processes are taken into account, and a comparison with the current LHCb data is performed. The impact of an intrinsic charm component in the proton’s wave function is also estimated. Predictions for the self-normalized yields of D0 mesons as a function of the multiplicity of coproduced charged hadrons are presented, considering pp collisions at s=13 TeV and different values of the meson rapidity. A comparison with the predictions for the kaon and isolated photon production is performed. Our results indicate that a future experimental analysis of the D0 meson production at forward rapidities and high multiplicities can be useful to probe the CGC formalism and to disentangle the contribution of initial—and final—state effects. Published by the American Physical Society 2024

Analysis of anomalies using weak effective Hamiltonian with complex couplings and their impact on various physical observables

Abstract Recently, the experimental measurements of the branching ratios and different polarization asymmetries for processes occurring through flavor-changing-charged current transitions by BABAR, Belle, and LHCb have revealed some significant differences from the corresponding Standard Model (SM) predictions. This has triggered an interest to search for physics beyond the SM in the context of various new physics (NP) models and using the model-independent weak effective Hamiltonian (WEH). Assuming left-handed neutrinos, we add the dimension-six vector, (pseudo-)scalar, and tensor operators with complex Wilson coefficients (WCs) to the SM WEH. Using 60%, 30%, and 10% constraints resulting from the branching ratio of , we reassess the parametric space of these new physics WCs accommodating the current anomalies based on the most recent HFLAV data of and and Belle data of and . We find that the allowed parametric region of left-handed scalar couplings strongly depends on the constraints of the branching ratio, and the maximum pull from the SM predictions results from the <60% branching ratio limit. Also, the parametric region changes significantly if we extend the analysis by adding LHCb data of and . Furthermore, due to the large uncertainties in the measurements of and , we derive the sum rules which complement them with and . Using the best-fit points of the new complex WCs along with the latest measurements of , we predict the numerical values of the observable , , and from the sum rules. The simultaneous dependence of abovementioned physical observables on the NP WCs is established by plotting their correlation with and , which are useful to discriminate between various NP scenarios. We find that the most significant impact of NP results from the WC . Finally, we study the impact of these NP couplings on various angular and triple product asymmetries that could be measured in some ongoing and future experiments. The precise measurements of these observables are important to check the SM and extract the possible NP.

Strange hidden-charm pentaquark poles from B− → J / ψΛp

Recent LHCb data for B− → J/ψΛp¯ show a clear peak structure at the ΞcD¯ threshold in the J/ψ invariant mass (MJ/ψΛ) distribution. In their amplitude analysis, LHCb identified the peak with the first hidden-charm pentaquark with strangeness PψsΛ(4338). We conduct a coupled-channel amplitude analysis of the LHCb data by simultaneously fitting the MJ/ψΛ,MJ/ψp¯,MΛp¯, and cosθK* distributions. Rather than the Breit-Wigner fit employed in the LHCb analysis, we consider relevant threshold effects and a unitary ΞcD¯ − ΛcD¯s coupled-channel scattering amplitude from which PψsΛ poles are extracted for the first time. In our default fit, the PψsΛ(4338) pole is almost a ΞcD¯ bound state at (4338:2±1:4)−(1:9±0:5) i MeV. Our default model also fits a large fluctuation at the ΛcD¯s threshold, giving a ΛcD¯s virtual state, PψsΛ(4255), at 4254:7±0:4 MeV. We also found that the PψsΛ(4338) peak cannot solely be a kinematical effect, and a nearby pole is needed.

The isospin and compositeness of the Tcc(3875)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{cc}(3875)$$\\end{document} state

We perform a fit to the LHCb data on the Tcc(3875)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{cc}(3875)$$\\end{document} state in order to determine its nature. We use a general framework that allows to have the D0D∗+,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^0 D^{*+},$$\\end{document}D+D∗0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^+ D^{*0}$$\\end{document} components forming a molecular state, as well as a possible nonmolecular state or contributions from missing coupled channels. From the fits to the data we conclude that the state observed is clearly of molecular nature from the D0D∗+,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^0 D^{*+},$$\\end{document}D+D∗0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^+ D^{*0}$$\\end{document} components and the possible contribution of a nonmolecular state or missing channels is smaller than 3%, compatible with zero. We also determine that the state has isospin I=0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I=0$$\\end{document} with a minor isospin breaking from the different masses of the channels involved, and the probabilities of the D0D∗+,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^0 D^{*+},$$\\end{document}D+D∗0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^+ D^{*0}$$\\end{document} channels are of the order of 69% and 29% with uncertainties of 1%. The differences between these probabilities should not be interpreted as a measure of the isospin violation. Due to the short range of the strong interaction where the isospin is manifested, the isospin nature is provided by the couplings of the state found to the D0D∗+,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^0 D^{*+},$$\\end{document}D+D∗0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^+ D^{*0}$$\\end{document} components, and our results for these couplings indicate that we have an I=0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I=0$$\\end{document} state with a very small isospin breaking. We also find that the potential obtained provides a repulsive interaction in I=1,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I=1,$$\\end{document} preventing the formation of an I=1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I=1$$\\end{document} state, in agreement with what is observed in the experiment.

Associated production of prompt J/ψ and Υ mesons in pp collisions at sqrt{s} = 13 TeV

The associated production of prompt J/ψ and Υ mesons in pp collisions at a centre-of-mass energy of sqrt{s} = 13 TeV is studied using LHCb data, corresponding to an integrated luminosity of 4 fb−1. The measurement is performed for J/ψ (Υ) mesons with a transverse momentum pT< 10 (30) GeV/c in the rapidity range 2.0 < y < 4.5. In this kinematic range, the cross-section of the associated production of prompt J/ψ and Υ(1S) mesons is measured to be 133 ± 22 ± 7 ± 3 pb, with a significance of 7.9 σ, and that of prompt J/ψ and Υ(2S) mesons to be 76 ± 21 ± 4 ± 7 pb, with a significance of 4.9 σ. The first uncertainty is statistical, the second systematic, and the third due to uncertainties on the used branching fractions. This is the first observation of the associated production of J/ψ and Υ(1S) in proton-proton collisions. Differential cross-sections are measured as functions of variables that are sensitive to kinematic correlations between the J/ψ and Υ(1S) mesons. The effective cross-sections of the associated production of prompt J/ψ and Υ mesons are obtained and found to be compatible with measurements using other particle productions.

Tree-level new physics in R(K(∗))

We implement the [Formula: see text] fit for [Formula: see text] with possible tree-level new physics in a model-independent parametrization. Relevant Wilson coefficients are decomposed into the new physics scale, its power, and the fermionic couplings. Constraints from the branching ratio of [Formula: see text] can be naturally incorporated with the scheme. For a reasonable set of the parameter ranges it is found that the new physics is less than [Formula: see text]. Some new physics models including the leptoquark, [Formula: see text], etc. can be embraced within our framework. We give comments on new LHCb data which are close to the standard model predictions.

To (b)e or not to (b)e: no electrons at LHCb

We discuss the impact of the recent LHCb update on the two lepton-flavour universality ratios R_K and R_{K^*}, and the CMS update of B({B_s rightarrow mu ^+mu ^-}) regarding the possibility of New Physics in brightarrow sell ^+ell ^- decays. We perform global fits of the New Physics Wilson coefficients defined in the model-independent approach of the Weak Effective Theory at the b-quark mass. We discuss three different frameworks for this analysis: (i) an update limited to the experimental data but using the same theoretical framework as in earlier works, (ii) a full update concerning both the experimental inputs and the theoretical framework, (iii) an analysis without the LHCb results on electron modes. The comparison between these various sets of results allows us to identify the differences stemming from the various components of the analysis: new experimental results, new inputs for the hadronic form factors, the role played by LHCb data on electron modes. As expected, the significance of all New Physics hypotheses gets reduced after the LHCb announcements on R_{K^{(*)}} while the hypothesis of a lepton-flavour-universal contribution to the Wilson coefficient of the semileptonic O_{9ell } operators (possibly with a very small lepton-flavour-universality violating component) is clearly reinforced. We also discuss the possibility of a long-distance charm-loop contribution through a mode-by-mode analysis and we find that the preferred values for the {mathcal C}_{9mu } Wilson coefficient are consistent throughout the different brightarrow smu ^+mu ^- modes and that there is no significant evidence of non-constant q^2 dependencies, which would indicate the presence of a long-distance charm-loop contribution beyond those already included.

A study of C!P violation in the decays {{B} ^pm } rightarrow [{{K} ^+} {{K} ^-} {{uppi } ^+} {{uppi } ^-} ]_{D} h^{pm } (h = K, pi ) and {{B} ^pm } rightarrow [{{uppi } ^+} {{uppi } ^-} {{uppi } ^+} {{uppi } ^-} ]_{D} h^{pm }

The first study of C!P violation in the decay mode {{B} ^pm } rightarrow [{{K} ^+} {{K} ^-} {{uppi } ^+} {{uppi } ^-} ]_{D} h^pm , with h=K,pi , is presented, exploiting a data sample of proton–proton collisions collected by the LHCb experiment that corresponds to an integrated luminosity of 9text {,fb} ^{-1} . The analysis is performed in bins of phase space, which are optimised for sensitivity to local C!P asymmetries. C!P-violating observables that are sensitive to the angle gamma of the Unitarity Triangle are determined. The analysis requires external information on charm-decay parameters, which are currently taken from an amplitude analysis of LHCb data, but can be updated in the future when direct measurements become available. Measurements are also performed of phase-space integrated observables for {{B} ^pm } rightarrow [{{K} ^+} {{K} ^-} {{uppi } ^+} {{uppi } ^-} ]_{D} h^pm and {{B} ^pm } rightarrow [{{uppi } ^+} {{uppi } ^-} {{uppi } ^+} {{uppi } ^-} ]_{D} h^pm decays.

Open charm production and asymmetry in pNe collisions at sqrt{s_{scriptscriptstyle {textrm{NN}}}} = 68.5,text {Gehspace{-1.00006pt}V}

A measurement of {{D}} ^0 meson production by the LHCb experiment in its fixed-target configuration is presented. The production of {{D}} ^0 mesons is studied with a beam of 2.5 ,text {Tehspace{-1.00006pt}V} protons colliding on a gaseous neon target at rest, corresponding to a nucleon–nucleon centre-of-mass energy of sqrt{s_{scriptscriptstyle text {NN}}} = 68.5,,text {Gehspace{-1.00006pt}V} . The sum of the {{D}} ^0 and {hspace{0.0pt}overline{hspace{0.0pt}{D}}} {}^0 production cross-section in ptext {Ne} collisions in the centre-of-mass rapidity range y^{star }in [-2.29, 0] is found to be sigma _{D^{0}}^{y^star in [-2.29, 0]} = 48.2 pm 0.3 pm 4.5 ,upmu text {b}/text {nucleon} where the first uncertainty is statistical and the second is systematic. The {{{D}} ^0}-{{hspace{0.0pt}overline{hspace{0.0pt}{D}}} {}^0} production asymmetry is also evaluated and suggests a trend towards negative values at large negative y^{star }. The considered models do not account precisely for all the features observed in the LHCb data, but theoretical predictions including 1% intrinsic charm and 10% recombination contributions better describe the data than the other models considered.

Near-threshold structures in the Ds+Ds− mass distribution of the decay B+→Ds+Ds−K+

Two near-threshold peaking structures with spin-parities $J^{\mathrm{PC} }=0^{++}$ were recently discovered by the LHCb Collaboration in the $ D_{s}^{+}D_{s}^{-}$ invariant mass distribution of the decay $ B^{+}\rightarrow D_{s}^{+}D_{s}^{-}K^{+}$. The first of them is the resonance $X(3960)$, whereas the second one, $X_0(4140)$, is a structure with the mass around $4140~\mathrm{MeV}$. To explore their natures and model them, we study the hadronic molecule $\mathcal{M}=D_s^{+}D_s^{-}$ and calculate its mass, current coupling, and width. The mass and current coupling of the molecule are extracted from the QCD two-point sum rule analyses by taking into account vacuum condensates up to dimension $10$. To evaluate its full width, we consider the processes $\mathcal{M} \to D_{s}^{+}D_{s}^{-}$, $\mathcal{M} \to\eta_{c}\eta^{(\prime)}$, and $\mathcal{ M} \to J/\psi\phi$. Partial widths of these decays are determined by the strong couplings $g_i, \ i=1,2,3,4 $ at vertices $\mathcal{M} D_{s}^{+}D_{s}^{-}$, $\mathcal{M}\eta_{c} \eta^{(\prime)}$, and $\mathcal{M} J/\psi\phi$. They are computed by means of the three-point sum rule method. Predictions for the mass $m=(4117 \pm 85)~\mathrm{MeV}$ and width $\Gamma_{ \mathcal{M}}=(62 \pm 12)~\mathrm{MeV}$ of the molecule $\mathcal{M}$ are compared with the corresponding LHCb data, and also with our results for the diquark-antidiquark state $X=[cs][\overline{c}\overline{s}]$. We argue that the structure $X_0(4140)$ may be interpreted as the hadronic molecule $ D_s^{+}D_s^{-}$, whereas the resonance $X(3960)$ can be identified with the tetraquark $X$.

Resolution of the LHCb ηc anomaly

Due to the heavy-quark symmetry of Non-Relativistic Quantum Chromodynamics (NRQCD), the cross-section for the production of ηc can be predicted. This NRQCD prediction when confronted with data from the LHCb is seen to fail miserably. We address this LHCb ηc anomaly in this paper using a new approach called modified NRQCD, an approach that has been shown to work extremely well for studying J/ψ, ψ′ and χc production at the LHC. We show, in the present paper, that the predictions for ηc production agrees very well with LHCb measurements at the three different values of energy that the experiment has presented data for. Modified NRQCD also explains the intriguing agreement of the LHCb ηc data with the colour-singlet prediction. The remarkable agreement of the theoretical predictions with the LHCb data suggests that modified NRQCD is closer to apprehending the true dynamics of quarkonium production.

X(6900) peak could be a molecular state

The analyses of the LHCb data on $X(6900)$ found in di-$J/\psi$ and $J/\psi \psi(3686)$ systems are performed using a momentum-dependent {Flatt\'{e}}-like parameterization. The use of the pole counting rule and spectral density function sum rule give consistent conclusions that $X(6900)$ may not be a molecule of $J/\psi \psi(3686)$. Nevertheless it is still possible that $X(6900)$ be a molecule of higher states, such as $J/\psi\psi(3770)$, $\chi_{c0}\chi_{c2}$, etc.

A U-spin anomaly in charm CP violation

Recent LHCb data shows that the direct CP asymmetries of the decay modes D0 → π+π− and D0 → K+K− have the same sign, violating an improved U-spin limit sum rule in an unexpected way at 2.1σ. From the new data, we determine for the first time the imaginary part of the CKM-subleading, U-spin breaking ∆U = 1 correction to the U-spin limit ∆U = 0 amplitude. The imaginary part of the ∆U = 0 amplitude is determined by Delta {a}_{textrm{CP}}^{textrm{dir}} . The corresponding strong phases are yet unknown and could be extracted in the future from time-dependent measurements. Assuming mathcal{O}(1) strong phases due to non-perturbative rescattering, we find the ratio of U-spin breaking to U-spin limit contributions to the CKM-subleading amplitudes to be left({173}_{hbox{--} 74}^{+85}right)% . This highly exceeds the Standard Model (SM) expectation of ~ 30% U -spin breaking, with a significance of 1.95σ. If this puzzle is confirmed with more data in the future, in the SM it would imply the breakdown of the U -spin expansion in CKM-subleading amplitudes of charm decays. The other solution are new physics models that generate an additional ∆U = 1 operator, leaving the U-spin power expansion intact. Examples for the latter option are an extended scalar sector or flavorful Z′ models.

B-anomalies in a twin Pati-Salam theory of flavour including the 2022 LHCb {R}_{K^{left(ast right)}} analysis

We perform a comprehensive phenomenological analysis of the twin Pati-Salam theory of flavour, focussing on the parameter space relevant for interpreting the B-anomalies via vector leptoquark U1 exchange. This model provides a very predictive framework in which the U1 couplings and the Yukawa couplings find a common origin via mixing of chiral quarks and leptons with vector-like fermions, providing a direct link between the B-anomalies and the fermion masses and mixing. We propose and study a simplified model with three vector-like fermion families, in the massless first family approximation, and show that the second and third family charged fermion masses and mixings and the B-anomalies can be simultaneously explained and related. The model has the proper flavour structure to be compatible with all low-energy observables, and leads to predictions in promising observables such as τ → 3μ, τ → μγ and Bto {K}^{left(ast right)}nu overline{nu} at Belle II and LHCb. The model also predicts a rich spectrum of TeV scale gauge bosons and vector-like fermions, all accessible to the LHC. In this updated version we have included an extended analysis considering the new 2022 LHCb data on {R}_{K^{left(ast right)}} , which has slightly shifted the preferred parameter space with respect to the 2021 case. The model can still explain the {R}_{D^{left(ast right)}} anomalies at 1σ in a narrow window, however we expect small deviations from the SM on the {R}_{K^{left(ast right)}} ratios, to be tested in the future via more precise measurements by the LHCb collaboration. We also predict RD = {R}_{D^{ast }} , with future measurements shifting the world averages to slightly smaller central values.

Form factors and branching fraction calculations for $$B_s \rightarrow D_s^{(*)} \ell ^+ \nu _\ell$$ in view of LHCb observation

In light of the LHCb observations about the $$B_s \rightarrow D_s^{(*)}\ell \nu _\ell$$ semileptonic decays, we study these channels within the standard model framework of covariant confined quark model. The necessary transition form factors are computed in the entire dynamical range of momentum transfer squared with built-in infrared confinement. Our computed ratios of the decay widths from tau mode to muon mode for $$D_s$$ and $$D_s^*$$ mesons are found to be $$R(D_s) = 0.271 \pm 0.069$$ and $$R(D_s^*) = 0.240 \pm 0.038$$ . We further determine the ratio of the decay width from $$D_s$$ and $$D_s^*$$ channel for muon mode $$\Gamma (B_s \rightarrow D_s \mu ^+ \nu _\mu )/\Gamma (B_s \rightarrow D_s^* \mu ^+ \nu _\mu ) = 0.451 \pm 0.093$$ . Our results are in excellent agreement with the data from the latest LHCb experiments as well as lattice quantum chromodynamics simulations. We also compare the shape of differential decay distribution for $$B_s \rightarrow D_s^* \mu ^+ \nu _\mu$$ with the LHCb data, and our results are in very good agreement throughout all the individual bins. Some other physical observables such as forward-backward asymmetry and longitudinal polarizations of leptons in the final state are also computed.