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In this work we improve on several aspects of the computation of the (anti-)neutrino charged-current multi-nucleon cross section carried out in Phys.Rev.C 83 (2011) 045501 and Phys.Rev.C 102 (2020) 024601. Most importantly, we implement a consistent treatment of the nucleon self-energy in the $W^\pm N\to N'\pi$ amplitude entering the definition of the two-particle two-hole (2p2h) cross-section, and estimate the source of uncertainty of our model due to a simplified treatment of the $\Delta$ self-energy. Our new predictions are around $20-40\%$ higher than previously. We show comparisons for the inclusive lepton double-differential cross sections, with no pions in the final state, measured by MiniBooNE on carbon and by T2K on carbon and oxygen. In all cases, we find an excellent reproduction of the experiments, and in particular, the neutrino MiniBooNE data is now well described without requiring a global $90\%$ re-scaling of the flux. In addition, we take the opportunity of this revision to discuss in detail several important issues of the calculation of the 2p2h cross section, delving into the microscopic dynamics of the multi-nucleon mechanisms. The improved treatment presented in this work provides realistic first-step emitted two-nucleon final state momentum configurations, beyond the approximation of phase-space distributions., Comment: 16 pages, 9 figures

We present a detailed study of the lowest-lying ${\frac{1}{2}}^-$ and ${\frac{3}{2}}^-$ $\Lambda_{Q}$ resonances both in the heavy quark (bottom and charm) and the strange sectors. We have paid special attention to the interplay between the constituent quark-model and chiral baryon-meson degrees of freedom, which are coupled using a unitarized scheme consistent with leading-order heavy quark symmetries. We show that the $\Lambda_b(5912)$ [$J^P=1/2^-$], $\Lambda_b(5920)$ [$J^P=3/2^-$] and the $\Lambda_c(2625)$ [$J^P=3/2^-$], and the $\Lambda(1520)$ [$J^P=3/2^-$] admitting larger breaking corrections, are heavy-quark spin-flavor siblings. They can be seen as dressed quark-model states with $\Sigma_{Q}^{(*)}\pi$ molecular components of the order of 30\%. The ${J^P=\frac{1}{2}}^-$ $\Lambda_c(2595)$ has, however, a higher molecular probability of at least $50$\%, and even values greater than 70\% can be easily accommodated. This is because it is located almost on top of the threshold of the $\Sigma_c\pi$ pair, which largely influences its properties. Although the light degrees of freedom in this resonance would be coupled to spin-parity $1^-$ as in the $\Lambda_b(5912)$, $\Lambda_b(5920)$ and $\Lambda_c(2625)$, the $\Lambda_c(2595)$ should not be considered as a heavy-quark spin-flavor partner of the former ones. We also show that the $\Lambda(1405)$ chiral two-pole pattern does not have analogs in the $\frac{1}{2}^-$ charmed and bottomed sectors, because the $ND^{(*)}$ and $N\overline{B}{}^{(*)} $ channels do not play for heavy quarks the decisive role that the $N \overline{K}$ does in the strange sector, and the notable influence of the bare quark-model states for the charm and bottom resonances. Finally, we predict the existence of two $\Lambda_b(6070)$ and two $\Lambda_c(2765)$ heavy-quark spin and flavor sibling odd parity states., Comment: 41 pages, 13 figures, and 7 tables

We study here the inverse problem of starting from the femtoscopic correlation functions of related channels and analyze them with an efficient tool to extract the maximum information possible on the interaction of the components of these channels, and the existence of possible bound states tied to this interaction. The method is flexible enough to accommodate non-molecular components and the effect of missing channels relevant for the interaction. We apply the method to realistic correlation functions for the $D^{*+}D^0$ and $D^{*0}D^+$ channels derived consistently from the properties of the $T_{cc}(3875)^+$ and find that we can extract the existence of a bound state, its nature as a molecular state of the $D^{*+}D^0$ and $D^{*0}D^+$ channels, the probabilities of each channel, as well as scattering lengths and effective ranges for the channels, together with the size of the source function, all of them with a relatively good precision.

We have conducted a study of the femtoscopic correlation functions for the $D^0D^{*+}$ and $D^+D^{*0}$ channels that build the $T_{cc}$ state. We develop a formalism that allows us to factorize the scattering amplitudes outside the integrals in the formulas, and the integrals involve the range of the strong interaction explicitly. For a source of size of 1 fm, we find values for the correlation functions of the $D^0 D^{*+}$ and $D^+D^{*0}$ channels at the origin around 30 and 2.5, respectively, and we see these observables converging to unity already for relative momenta of the order of 200 MeV. We conduct tests to see the relevance of the different contributions to the correlation function and find that it mostly provides information on the scattering length, since the presence of the source function in the correlation function introduces an effective cut in the loop integrals that makes them quite insensitive to the range of the interaction., Comment: 9 pagines, 9 figures

We have studied the contribution of the state $X(3930)$, coming from the interaction of the $D \overline{D}$ and $D^{+}_s D^{-}_s$ channels, to the $B^- \to K^- J/\psi \omega $ decay. The purpose of this work is to offer a complementary tool to see if the $X(3930)$ state observed in the $D^+ D^-$ channel is the same or not as the $X(3960)$ resonance claimed by the LHCb collaboration from a peak in the $D^{+}_s D^{-}_s$ mass distribution around threshold. We present results for what we expect in the $J/\psi \omega $ mass distribution in the $B^- \to K^- J/\psi \omega $ decay and conclude that a clear signal should be seen around $3930\,\rm MeV$. At the same time, finding no extra resonance signal at $3960\,\rm MeV$ would be a clear indication that there is not a new state at $3960\,\rm MeV$, supporting the hypothesis that the near-threshold peaking structure peak in the $D^{+}_s D^{-}_s$ mass distribution is only a manifestation of a resonance below threshold., Comment: 15 pages; 10 figures; new version with improved discussion related to available experimental results

This white paper provides a comprehensive review of our present understanding of experimental neutrino anomalies that remain unresolved, charting the progress achieved over the last decade at the experimental and phenomenological level, and sets the stage for future programmatic prospects in addressing those anomalies. It is purposed to serve as a guiding and motivational "encyclopedic" reference, with emphasis on needs and options for future exploration that may lead to the ultimate resolution of the anomalies. We see the main experimental, analysis, and theory-driven thrusts that will be essential to achieving this goal being: 1) Cover all anomaly sectors -- given the unresolved nature of all four canonical anomalies, it is imperative to support all pillars of a diverse experimental portfolio, source, reactor, decay-at-rest, decay-in-flight, and other methods/sources, to provide complementary probes of and increased precision for new physics explanations; 2) Pursue diverse signatures -- it is imperative that experiments make design and analysis choices that maximize sensitivity to as broad an array of these potential new physics signatures as possible; 3) Deepen theoretical engagement -- priority in the theory community should be placed on development of standard and beyond standard models relevant to all four short-baseline anomalies and the development of tools for efficient tests of these models with existing and future experimental datasets; 4) Openly share data -- Fluid communication between the experimental and theory communities will be required, which implies that both experimental data releases and theoretical calculations should be publicly available; and 5) Apply robust analysis techniques -- Appropriate statistical treatment is crucial to assess the compatibility of data sets within the context of any given model., Comment: Contribution to Snowmass 2021 by the NF02 Topical Group (Understanding Experimental Neutrino Anomalies). Submitted to J. Phys. G as a Major Report

We discuss a model-independent estimator of the likelihood of the compositeness of a shallow S-wave bound or virtual state. The approach is based on an extension of Weinberg's relations in Phys. Rev. 137, B672 (1965) and it relies only on the proximity of the energy of the state to the two-hadron threshold to which it significantly couples. The scheme only makes use of the experimental scattering length and the effective range low energy parameters, and it is shown to be fully consistent for predominantly molecular hadrons. As explicit applications, we analyse the case of the deuteron, the $^1{\rm S}_0$ nucleon-nucleon virtual state and the exotic $D^{\ast}_{s0}(2317)^\pm$, and find strong support to the molecular interpretation in all cases. Results are less conclusive for the $D^{\ast}_{s0}(2317)^\pm$, since the binding energy of this state is significantly higher than that of the deuteron, and the approach employed here is at the limit of its applicability. We also qualitatively address the case of the recently discovered $T_{cc}^+$ state, within the isospin limit to avoid the complexity of the very close thresholds $D^0D^{\ast +}$ and $D^+D^{\ast 0}$, which could mask the ingredients of the approach proposed in this work., Comment: Reviewed version matching the published one

Since the $\nu_\tau(\bar\nu_\tau) A_Z \to \tau^\mp X$ reaction is notoriously difficult to be directly measured, the information on the dynamics of this nuclear process should be extracted from the analysis of the energy and angular distributions of the tau decay visible products. These distributions depend on the components of the tau-polarization vector. We give, for the first time, the general expression for the outgoing hadron (pion or rho meson) energy and angular differential cross section for the sequential $\nu_\tau A_Z \to \tau^-(\pi^- \nu_\tau, \rho^-\nu_\tau) X$ and $\bar\nu_\tau A_Z \to \tau^+(\pi^+ \bar\nu_\tau, \rho^+ \bar\nu_\tau) X$ reactions. Though all possible nuclear reaction mechanisms contribute to the distribution, it may be possible to isolate/enhance one of them by implementing appropriate selection criteria. For the case of the quasi-elastic reaction off oxygen and neutrino energies below 6 GeV, we show that the pion distributions are sensitive to the details of the tau-polarization components. We find significant differences between the full calculation, where the longitudinal and transverse components of the tau polarization vector vary with the energy and the scattering angle of the produced tau, and the simplified scheme in which the polarizations are set to one and zero (respective asymptotic values in the high energy regime). In addition to its potential impact on neutrino oscillation analyses, this result can be used to further test different nuclear models, since these observables provide complementary information to that obtained by means of the inclusive nuclear weak charged-current differential cross section. We also study the effects on the cross section of the $W_4$, $W_5$ nuclear structure functions, which contributions are proportional to the charged lepton mass, and therefore difficult to constrain in muon and electron neutrino experiments., Comment: 11 pages, 5 figures. We have corrected a numerical error in our calculation. Figures have changed but the discussion and conclusions remain the same. An erratum will be published

We study the $d^2 \Gamma_d /(d\omega d\cos\theta_d) $, $d\Gamma_d /d\cos\theta_d$ and $ d\Gamma_d /dE_d $ distributions, which are defined in terms of the visible energy and polar angle of the charged particle from the $\tau-$decay in $b\to c \tau\, (\mu \bar \nu_\mu \nu_\tau,\pi \nu_\tau,\rho\nu_\tau) \bar\nu_\tau$ reactions. The first two contain information on the transverse tau-spin, tau-angular and tau-angular-spin asymmetries of the $H_b\to H_c\tau\bar\nu_\tau$ parent decay and, from a dynamical point of view, they are richer than the commonly used one, $d^2 \Gamma_d /(d\omega dE_d) $, since the latter only depends on the tau longitudinal polarization. We pay attention to the deviations with respect to the predictions of the standard model (SM) for these new observables, considering new physics (NP) operators constructed using both right- and left-handed neutrino fields, within an effective field-theory approach. We present results for $\Lambda_b\to\Lambda_c\tau\, (\mu \bar \nu_\mu \nu_\tau,\pi\nu_\tau,\rho\nu_\tau)\bar\nu_\tau$ and $\bar B \to D^{(*)}\tau\, (\mu \bar \nu_\mu \nu_\tau,\pi\nu_\tau,\rho\nu_\tau) \bar\nu_\tau$ sequential decays and discuss their use to disentangle between different NP models. In this respect, we show that $d\Gamma_d /d\cos\theta_d$, which should be measured with sufficiently good statistics, becomes quite useful, especially in the $\tau\to \pi \nu_\tau$ mode. The study carried out in this work could be of special relevance due to the recent LHCb measurement of the lepton flavor universality ratio ${\cal R}_{\Lambda_c}$ in agreement with the SM. The experiment identified the $\tau$ using its hadron decay into $\pi^-\pi^+\pi^-\nu_\tau$, and this result for ${\cal R}_{\Lambda_c}$, which is in conflict with the phenomenology from the $b$-meson sector, needs confirmation from other tau reconstruction channels., Comment: 20 latex pages, 10 figures, 5 tables, presentation of figures 3 and 4 has changed, new comments and a new reference added

In the context of lepton flavor universality violation (LFUV) studies, we fully derive a general tensor formalism to investigate the role that left- and right-handed neutrino new-physics (NP) terms may have in $b\to c \tau\bar\nu_\tau$ transitions. We present, for several extensions of the Standard Model (SM), numerical results for the $\Lambda_b\to\Lambda_c\tau\bar\nu_\tau$ semileptonic decay, which is expected to be measured with precision at the LHCb. This reaction can be a new source of experimental information that can help to confirm, or maybe rule out, LFUV presently seen in $\bar B$ meson decays. The present study analyzes observables that can help in distinguishing between different NP scenarios that otherwise provide very similar results for the branching ratios, which are our currently best hints for LFUV. Since the $\tau$ lepton is very short-lived, we consider three subsequent $\tau$-decay modes, two hadronic $\pi\nu_\tau$ and $\rho\nu_\tau$ and one leptonic $\mu\bar\nu_\mu\nu_\tau$, which have been previously studied for $\bar B\to D^{(*)}$ decays. Within the tensor formalism that we have developed in previous works, we re-obtain the expressions for the differential decay width written in terms of visible (experimentally accessible) variables of the massive particle created in the $\tau$ decay. There are seven different $\tau$ angular and spin asymmetries that are defined in this way and that can be extracted from experiment. Those asymmetries provide observables that can help in constraining possible SM extensions., Comment: 43 latex pages, 4 figures, 2 tables, a few errata corrected and new comments added. Version accepted for publication in JHEP

For a general $H_b\to H_c\tau\bar\nu_\tau$ decay we analyze the role of the $\tau$ polarization vector ${\cal P}^\mu$ in the context of lepton flavor universality violation studies. We use a general phenomenological approach that includes, in addition to the Standard Model (SM) contribution, vector, axial, scalar, pseudoscalar and tensor new physics (NP) terms which strength is governed by, complex in general, Wilson coefficients. We show that both in the laboratory frame, where the initial hadron is at rest, and in the center of mass of the two final leptons, a $\vec {\cal P}$ component perpendicular to the plane defined by the three-momenta of the final hadron and the $\tau$ lepton is only possible for complex Wilson coefficients, being a clear signal for physics beyond the SM as well as time reversal (or CP-symmetry) violation. We make specific evaluations of the different polarization vector components for the $\Lambda_b\to\Lambda_c$, $\bar B_c\to\eta_c,J/\psi$ and $\bar B\to D^{(*)}$ semileptonic decays, and describe NP effects in the complete two-dimensional space associated with the independent kinematic variables on which the polarization vector depends. We find that the detailed study of ${\cal P}^\mu$ has great potential to discriminate between different NP scenarios for $0^-\to 0^-$ decays, but also for $\Lambda_b \to \Lambda_c$ transitions. For this latter reaction, we pay special attention to corrections to the SM predictions derived from complex Wilson coefficients contributions., Comment: 34 latex pages, 10 figures, 1 table. Enlarged and modified discussion. New references and one new figure added

We study the behaviour of the $\chi_{c1}(3872)$, also known as $X(3872)$, in dense nuclear matter. We begin from a picture in vacuum of the $X(3872)$ as a purely molecular $(D \bar D^*-c.c.)$ state, generated as a bound state from a heavy-quark symmetry leading-order interaction between the charmed mesons, and analyze the $D \bar D^*$ scattering $T-$matrix ($T_{D \bar D^*}$) inside of the medium. Next, we consider also mixed-molecular scenarios and, in all cases, we determine the corresponding $X(3872)$ spectral function and the $D \bar D^*$ amplitude, with the mesons embedded in the dense environment. We find important nuclear corrections for $T_{D \bar D^*}$ and the pole position of the resonance, and discuss the dependence of these results on the $D \bar D^*$ molecular component in the $X(3872)$ wave-function. These predictions could be tested in the finite-density regime that can be accessed in the future CBM and PANDA experiments at FAIR.

We have improved the tree-level model of Ref arXiv:1004.5484 [hep-ph] for weak production of kaons off nucleons by partially restoring unitarity. This is achieved by imposing Watson's theorem to the dominant vector and axial-vector contributions in appropriate angular momentum and isospin quantum number sectors. The observable consequences of this procedure are investigated., Comment: 8 pages, 5 figures

The NuSTEC workshop held at the University of Pittsburgh in October 2019 brought theorists and experimentalists together to discuss the state of modeling and measurements related to pion production in neutrino-nucleus scattering in the kinematic region where pions are produced through both resonant and non-resonant mechanisms. Modeling of this region is of critical importance to the current and future accelerator- and atmospheric-based neutrino oscillation experiments. For the benefit of the community, links to the presentations are accompanied by annotations from the speakers highlighting significant points made during the presentations and resulting discussions., Comment: 31 pages, includes links to workshop presentations

We apply the general formalism derived in N. Penalva et al. [Phys. Rev. D 101, 113004 (2020)] to the semileptonic decay of pseudoscalar mesons containing a $b$ quark. While present $B\to D^{(*)}$ data give the strongest evidence in favor of lepton flavor universality violation, the observables that are normally considered are not able to distinguish between different new physics (NP) scenarios. In the above reference we discussed the relevant role that the various contributions to the double differential decay widths $d^2\Gamma/(d\omega d\cos\theta_\ell)$ and $d^2\Gamma/(d\omega dE_\ell)$ could play to this end. Here $\omega$ is the product of the two hadron four-velocities, $\theta_\ell$ is the angle made by the final lepton and final hadron three-momenta in the center of mass of the final two-lepton system, and $E_\ell$ is the final charged lepton energy in the laboratory system. The formalism was applied there to the analysis of the $\Lambda_b\to\Lambda_c$ semileptonic decay showing the new observables were able to tell apart different NP scenarios. Here we analyze the $\bar B_c\to \eta_c \tau\bar\nu_\tau$, $\bar B_c\to J/\psi\tau\bar\nu_\tau$, $\bar B\to D\tau\bar\nu_\tau$ and $\bar B\to D^*\tau\bar\nu_\tau$ semileptonic decays. We show that, as a general rule, the $\bar B_c \to J/\psi$ observables, even including $\tau$ polarization, are less optimal for distinguishing between NP scenarios than those obtained from $\bar B_c \to \eta_c$ decays, or those presented in N. Penalva et al. for the related $\Lambda_b \to \Lambda_c$ semileptonic decay. Finally, we show that $\bar B\to D$ and $\bar B_c\to \eta_c$, and $\bar B\to D^*$ and $\bar B_c\to J/\psi$ decay observables exhibit similar behaviors., Comment: 28 latex pages, 26 figures, 2 tables, a new reference added and a few misprints corrected

We extend our general framework for semileptonic decay, originally introduced in N. Penalva et al. [Phys. Rev. D100, 113007 (2019)], with the addition of new physics (NP) tensor terms. In this way, all the NP effective Hamiltonians that are considered in lepton flavour universality violation (LFUV) studies have now been included. Besides, we now also give general expressions that allow for complex Wilson coefficients. The scheme developed is totally general and it can be applied to any charged current semileptonic decay, involving any quark flavors or initial and final hadron states. We show that all the hadronic input, including NP effects, can be parametrized in terms of 16 Lorentz scalar structure functions. In the second part of this work, we use this formalism to obtain the complete NP effects in the $\Lambda_b\to \Lambda_c \tau\bar\nu_\tau$ semileptonic decay, where LFUV, if finally confirmed, is also expected to be seen. We stress the relevance of the center of mass (CM) $d^2\Gamma/(d\omega d\cos\theta_\ell)$ and laboratory (LAB) $d^2\Gamma/(d\omega dE_\ell)$ differential decay widths. While models with very different strengths in the NP terms give the same differential $d\Gamma/d\omega$ and total decay widths for this decay, they predict very different numerical results for some of the $\cos\theta_\ell$ and $E_\ell$ coefficient-functions that determine the above two distributions. Thus, the combined analysis of the CM $d^2\Gamma/(d\omega d\cos\theta_\ell)$ and LAB $d^2\Gamma/ (d\omega dE_\ell)$ differential decay widths will help clarifying what kind of NP is a better candidate in order to explain LFUV., Comment: 24 latex pages, 7 figures, 1 table. A few typos corrected. Accepted for publication in Physical Review D

We present results of an updated calculation of the 2p2h (two particle two hole) contribution to the neutrino-induced charge-current cross section. We provide also some exclusive observables, interesting from the point of view of experimental studies, e.g. distributions of momenta of the outgoing nucleons and of available energy, which we compare with the results obtained within the NEUT generator. We also compute, and separate from the total, the contributions of 3p3h mechanisms. Finally, we discuss the differences between the present results and previous implementations of the model in MC event-generators, done at the level of inclusive cross sections, which might significantly influence the experimental analyses, particularly in the cases where the hadronic observables are considered., Comment: 15 pages, 9 figures

Recently five $\Omega_c$ excited states have been reported by the LHCb Collaboration, four of them corroborated by Belle. The Belle Collaboration has also discovered in 2017 one excited $\Xi_c$ with mass of 2930 MeV. In view of these recent detections, we analyze the possible molecular description of these states, using a unitarized baryon-meson model that incorporates both chiral and heavy-quark spin symmetries in a consistent manner. We pay a special attention to the renormalization procedure, so as to determine the robustness of our predictions. Within our model, we generate dynamically several $\Omega_c$ and $\Xi_c$ states. We find that, at least, three of our $\Omega_c$ states can be identified with the experimental ones and have spin-parity $J=1/2^-$ or $J=3/2^-$. Moreover, we find a plausible molecular description of not only the $\Xi_c(2930)$ state, but also $\Xi_c(2790)$, $\Xi_c(2815)$ and $\Xi_c(2970)$, reported in the PDG. Interestingly, we determine that $\Xi_c(2930)$ and $\Xi_c(2970)$ are heavy-quark spin partners with $J=1/2^-$ and $J=3/2^-$, respectively, while obtaining that $\Xi_c(2930)$, $\Omega_c(3090)$ or the $\Omega_c(3119)$, and $\Sigma_c(2800)$ would belong to the same SU(3) multiplet., Comment: 6 pages, contribution to the proceedings of the XVIII International Conference on Hadron Spectroscopy and Structure (HADRON2019), Guilin, China, 16-21 August 2019

We study odd parity $J=1/2$ and $J=3/2$ $\Xi_c$ resonances using a unitarized coupled-channel framework based on a ${\rm SU(6)}_{\rm lsf}\times$HQSS-extended Weinberg-Tomozawa baryon-meson interaction, while paying a special attention to the renormalization procedure. We predict a large molecular $\Lambda_c \bar K$ component for the $\Xi_c(2790)$ with a dominant $0^-$ light-degree-of-freedom spin configuration. We discuss the differences between the $3/2^-$ $\Lambda_c(2625)$ and $\Xi_c(2815)$ states, and conclude that they cannot be SU(3) siblings, whereas we predict the existence of other $\Xi_c-$states, two of them related to the two-pole structure of the $\Lambda_c(2595)$. It is of particular interest a pair of $J=1/2$ and $J=3/2$ poles, which form a HQSS doublet and that we tentatively assign to the $\Xi_c(2930)$ and $\Xi_c(2970)$, respectively. Within this picture, the $\Xi_c(2930)$ would be part of a SU(3) sextet, containing either the $\Omega_c(3090)$ or the $\Omega_c(3119)$, and that would be completed by the $\Sigma_c(2800)$. Moreover, we identify a $J=1/2$ sextet with the $\Xi_b(6227)$ state and the recently discovered $\Sigma_b(6097)$. Assuming the equal spacing rule and to complete this multiplet, we predict the existence of a $J=1/2$ $\Omega_b$ odd parity state, with a mass of 6360 MeV and that should be seen in the $\Xi_b \bar K$ channel., Comment: 13 pages, 5 figures, 4 tables

We have studied the meson-baryon $S-$wave interaction, using coupled channels, in the isoscalar hidden-charm strange sector and $J^P = 1/2^-,3/2^-$ and $5/2^-$. We impose constraints of heavy quark spin symmetry in the interaction and obtain the non vanishing matrix elements from an extension of the local hidden gauge approach to the charm sector. The ultraviolet divergences are renormalized using the same meson-baryon-loops regulator previously employed in the non-strange hidden charm sector, where a good reproduction of the properties of the newly discovered pentaquark states is obtained. We obtain five states of $1/2^-$, four of $3/2^-$ and one of $5/2^-$, which could be compared in the near future with forthcoming LHCb experiments. The $5/2^-$, three of the $3/2^-$ and another three of the $1/2^-$ resonances are originated from isoscalar $\bar D^{(*)}\Xi_c^\prime$ and $\bar D^{(*)}\Xi_c^*$ interactions. They should be located just few MeV below the corresponding thresholds (4446, 4513, 4588 and 4655 MeV), and would be SU(3)-siblings of the isospin 1/2 $\bar D^{(*)} \Sigma_c^{(*)}$ quasi-bound states previously found, and that provided a robust theoretical description of the $P_c(4440)$, $P_c(4457)$ and $P_c(4312)$ LHCb exotic states. The another two $1/2^-$ and $3/2^-$ states obtained in this work are result of the $\bar D^{(*)}\Xi_c-D^{(*)}_s\Lambda_c$ coupled-channels isoscalar interaction, are significantly broader than the others, with widths of the order of 15 MeV, being $\bar D^{(*)}_s\Lambda_c$ the dominant decay channel., Comment: 16 pages, 3 figures

We present a study of the $\tau$ polarization in charged-current quasielastic (anti)neutrino-nucleus scattering. The spectral function formalism is used to compute the differential cross section and the polarization components for several kinematical setups, relevant for neutrino-oscillation experiments. The effects of the nuclear corrections in these observables are investigated by comparing the results obtained using two different realistic spectral functions, with those deduced from the relativistic global Fermi gas model, where only statistical correlations are accounted for. We show that the spectral functions, although they play an important role when predicting the differential cross sections, produce much less visible effects on the polarization components of the outgoing $\tau$., Comment: 16 pages, 8 figures

We consider the ${\bar D}^{(*)}\Sigma_c^{(*)}$ states, together with $J/\psi N$ and other coupled channels, and take an interaction consistent with heavy quark spin symmetry, with the dynamical input obtained from an extension of the local hidden gauge approach. By fitting only one parameter to the recent three pentaquark states reported by the LHCb collaboration, we can reproduce the three of them in base to the mass and the width, providing for them the quantum numbers and approximate molecular structure as $1/2^-$ $\bar{D} \Sigma_c$, $1/2^-$ $\bar{D}^* \Sigma_c$, and $3/2^-$ $\bar{D}^* \Sigma_c$, and isospin $I=1/2$. We find another state around 4374 MeV, of $3/2^-$ $\bar{D} \Sigma_c^*$ structure, for which indications appear in the experimental spectrum. Two other near degenerate states of $1/2^-$ $\bar{D}^* \Sigma_c^*$ and $3/2^-$ $\bar{D}^* \Sigma_c^*$ nature are also found around 4520 MeV, which although less clear, are not incompatible with the observed spectrum. In addition, a $5/2^-$ $\bar D^* \Sigma_c^*$ state at the same energy appears, which however does not couple to $J/\psi p$ in $S-$wave, and hence it is not expected to show up in the LHCb experiment., Comment: 8 pages

We study the implications for $\Lambda_b \to \Lambda_c^*\ell\bar{\nu}_\ell$ and $\Lambda_b \to \Lambda_c^*\pi^-$ $[\Lambda_c^*=\Lambda_c(2595)$ and $\Lambda_c(2625)]$ decays that can be deduced from heavy quark spin symmetry (HQSS). Identifying the odd parity $\Lambda_c(2595)$ and $\Lambda_c(2625)$ resonances as HQSS partners, with total angular momentum--parity $j_q^P=1^-$ for the light degrees of freedom, we find that the ratios $\Gamma(\Lambda_b\rightarrow\Lambda_c(2595)\pi^-)/\Gamma(\Lambda_b\rightarrow\Lambda_c(2625)\pi^-)$ and $\Gamma(\Lambda_b\rightarrow \Lambda_c(2595) \ell \bar{\nu}_\ell)/ \Gamma(\Lambda_b\rightarrow\Lambda_c(2625) \ell \bar{\nu}_\ell)$ agree, within errors, with the experimental values given in the Review of Particle Physics. We discuss how future, and more precise, measurements of the above branching fractions could be used to shed light into the inner HQSS structure of the narrow $\Lambda_c(2595)$ odd-parity resonance. Namely, we show that such studies would constrain the existence of a sizable $j^P_q=0^-$ component in its wave-function, and/or of a two-pole pattern, in analogy to the case of the similar $\Lambda(1405)$ resonance in the strange sector, as suggested by most of the approaches that describe the $\Lambda_c(2595)$ as a hadron molecule. We also investigate the lepton flavor universality ratios $R[\Lambda_c^*] = {\cal B}(\Lambda_b \to \Lambda_c^* \tau\,\bar\nu_\tau)/{\cal B}(\Lambda_b \to \Lambda_c^* \mu\,\bar\nu_\mu)$, and discuss how $R[\Lambda_c(2595)]$ may be affected by a new source of potentially large systematic errors if there are two $\Lambda_c(2595)$ poles., Comment: 22 pages, 2 figures

We present results for the quasi-elastic weak production of $\Lambda$ and $\Sigma$ hyperons induced by $\bar{\nu}$ scattering off nuclei, in the kinematical region of interest for accelerator neutrino experiments. We employ realistic hole spectral functions and we describe the propagation of the hyperons in the nuclear medium by means of a Monte Carlo cascade. The latter strongly modifies the kinematics and the relative production rates of the hyperons, leading to a non-vanishing $\Sigma^+$ cross section, to a sizable enhancement of the $\Lambda$ production and to a drastic reduction of the $\Sigma^0$ and $\Sigma^-$ distributions. We also compute the quasi-elastic weak $\Lambda_c$ production cross section, paying special attention to estimate the uncertainties induced by the model dependence of the vacuum $n\to \Lambda_c$ weak matrix element. In this regard, the recent BESIII measurements of the branching ratios of $\Lambda_c\rightarrow \Lambda l^+\nu_l$ ($l=e,\mu$) are used to benchmark the available theoretical predictions., Comment: 18 pages, 10 figures

Motivated by the success of the flavour physics programme carried out over the last decade at the Large Hadron Collider (LHC), we characterize in detail the physics potential of its High-Luminosity and High-Energy upgrades in this domain of physics. We document the extraordinary breadth of the HL/HE-LHC programme enabled by a putative Upgrade II of the dedicated flavour physics experiment LHCb and the evolution of the established flavour physics role of the ATLAS and CMS general purpose experiments. We connect the dedicated flavour physics programme to studies of the top quark, Higgs boson, and direct high-$p_T$ searches for new particles and force carriers. We discuss the complementarity of their discovery potential for physics beyond the Standard Model, affirming the necessity to fully exploit the LHC's flavour physics potential throughout its upgrade eras., Comment: Report from Working Group 4 on the Physics of the HL-LHC, and Perspectives at the HE-LHC, 292 pages

The study of pion production in nuclei is important for signal and background determinations in current and future neutrino oscillation experiments. The first step, however, is to understand the pion production reactions at the free nucleon level. We present an exhaustive study of the charged-current and neutral-current neutrino and antineutrino pion production off nucleons, paying a special attention to the angular distributions of the outgoing pion. We show, using general arguments, that parity violation and time-reversal odd correlations in the weak differential cross sections are generated from the interference between different contributions to the hadronic current that are not relatively real. Next, we present a detailed comparison of three, state of the art, microscopic models for electroweak pion production off nucleons, and we also confront their predictions with polarized electron data, as a test of the vector content of these models. We also illustrate the importance of carrying out a comprehensive test at the level of outgoing pion angular distributions, going beyond comparisons done for partially integrated cross sections, where model differences cancel to a certain extent. Finally, we observe that all charged and neutral current distributions show sizable anisotropies, and identify channels for which parity violating effects are clearly visible. Based on the above results, we conclude that the use of isotropic distributions for the pions in the center of mass of the final pion-nucleon system, as assumed by some of the Monte Carlo event generators, needs to be improved by incorporating the findings of microscopic calculations., Comment: 41 latex pages, 26 figures. Figure 4b corrected. Misprints corrected

The masses of the $D^\ast_{s0}(2317)$ and $D_{s1}(2460)$ resonances lie below the $DK$ and $D^\ast K$ thresholds respectively, which contradicts the predictions of naive quark models and points out to non-negligible effects of the $D^{(\ast)}K$ loops in the dynamics of the even-parity scalar ($J^\pi=0^+$) and axial-vector ($J^\pi=1^+$) $c\bar s$ systems. Recent lattice QCD studies, incorporating the effects of the $D^{(\ast)}K$ channels, analyzed these spin-parity sectors and correctly described the $D^\ast_{s0}(2317)-D_{s1}(2460)$ mass splitting. Motivated by such works, we study the structure of the $D_{s0}^\ast(2317)$ and $D_{s1}(2460)$ resonances in the framework of an effective field theory consistent with heavy quark spin symmetry, and that incorporates the interplay between $D^{(\ast)}K$ meson-meson degrees of freedom and bare P-wave $c\bar s$ states predicted by constituent quark models. We extend the scheme to finite volumes and fit the strength of the coupling between both types of degrees of freedom to the available lattice levels, which we successfully describe. We finally estimate the size of the $D^{(\ast)}K$ two-meson components in the $D^\ast_{s0}(2317)$ and $D_{s1}(2460)$ resonances, and we conclude that these states have a predominantly hadronic-molecular structure, and that it should not be tried to accommodate these mesons within $c\bar{s}$ constituent quark model patterns., Comment: 21 pages, 5 figures. Matches the published version. arXiv admin note: text overlap with arXiv:1706.01247 by other authors

By solving the Muskhelishvili-Omn\`es integral equations, the scalar form factors of the semileptonic heavy meson decays $D\to\pi \bar \ell \nu_\ell$, $D\to \bar{K} \bar \ell \nu_\ell$, $\bar{B}\to \pi \ell \bar\nu_\ell$ and $\bar{B}_s\to K \ell \bar\nu_\ell$ are simultaneously studied. As input, we employ unitarized heavy meson-Goldstone boson chiral coupled-channel amplitudes for the energy regions not far from thresholds, while, at high energies, adequate asymptotic conditions are imposed. The scalar form factors are expressed in terms of Omn\`es matrices multiplied by vector polynomials, which contain some undetermined dispersive subtraction constants. We make use of heavy quark and chiral symmetries to constrain these constants, which are fitted to lattice QCD results both in the charm and the bottom sectors, and in this latter sector to the light-cone sum rule predictions close to $q^2=0$ as well. We find a good simultaneous description of the scalar form factors for the four semileptonic decay reactions. From this combined fit, and taking advantage that scalar and vector form factors are equal at $q^2=0$, we obtain $|V_{cd}|=0.244\pm 0.022$, $|V_{cs}|=0.945\pm 0.041$ and $|V_{ub}|=(4.3\pm 0.7)\times10^{-3}$ for the involved Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. In addition, we predict the following vector form factors at $q^2=0$: $|f_+^{D\to\eta}(0)|=0.01\pm 0.05$, $|f_+^{D_s\to K}(0)|=0.50 \pm 0.08$, $|f_+^{D_s\to\eta}(0)|=0.73\pm 0.03$ and $|f_+^{\bar{B}\to\eta}(0)|=0.82 \pm 0.08$, which might serve as alternatives to determine the CKM elements when experimental measurements of the corresponding differential decay rates become available. Finally, we predict the different form factors above the $q^2-$regions accessible in the semileptonic decays, up to moderate energies amenable to be described using the unitarized coupled-channel chiral approach., Comment: includes further discussions and references; matches the accepted version

We have reviewed the renormalization procedure used in the unitarized coupled-channel model of Phys. Rev. D85 114032 (2012), and its impact in the $C=1$, $S=-2$, and $I=0$ sector, where five $\Omega_c^{(*)}$ states have been recently observed by the LHCb Collaboration. The meson-baryon interactions used in the model are consistent with both chiral and heavy-quark spin symmetries and lead to a successful description of the observed lowest-lying odd parity resonances $\Lambda_c(2595)$ and $\Lambda_c(2625)$, and $\Lambda_b(5912)$ and $\Lambda_b(5920)$ resonances. We show that some (probably at least three) of the states observed by LHCb will also have odd parity and spins $J=1/2$ and $J=3/2$, belonging two of them to the same ${\rm SU(6)}_{\rm light-spin-flavor}\times$HQSS multiplets that the latter strangenessless heavy$-\Lambda$ baryons., Comment: 11 pages, 3 figures, 6 tables, published in The European Physical Journal C

In this work we calculate the ratios of rates of the $\Xi_b$ nonleptonic and semileptonic decays into the $\Xi_c$(2790) and $\Xi_c$(2815) ($\Xi_c^*$) resonances. These resonances are dynamically generated from the pseudoscalar-baryon and vector-baryon interactions, whose mixing is done using the chiral Weinberg-Tomozawa (WT) meson-baryon interaction extended to four flavors. The first part of the decay is a weak decay that we analyze through their quark constituents where it is noted that only the heavy quarks ($b$ and $c$) participate in the interaction, leaving the light pair ($ds$) as spectators. This first decay then produces a meson-baryon pair that creates the $\Xi_c^*$ through the WT interaction. We then proceed to calculate the decay rates to $\Xi_c$(2790) and $\Xi_c$(2815) for both the nonleptonic and semileptonic cases and then calculate the ratios between them. We do this calculation nonrelativistically and fully relativistically and notice that, even though both approaches yield somewhat different results in the rates, the ratios are very similar (difference on the order of 1\%) in both cases. The absolute values of the decay rates are also successfully calculated by obtaining the rates between our decays and $\Lambda_b \to \pi (D_s ) \ \Lambda_c (2595) \left(\Lambda_c (2625) \right)$ and $\Lambda_b \to \bar{\nu}_l l \ \Lambda_c (2595) \left(\Lambda_c (2625) \right)$ for which there are experimental results, since the momentum transfer is similar such we can cancel out the influence of the quark wave functions in the ratios., Comment: 6 pages, 2 figures

Scaling features of the nuclear electromagnetic response functions unveil aspects of nuclear dynamics that are crucial for interpretating neutrino- and electron-scattering data. In the large momentum-transfer regime, the nucleon-density response function defines a universal scaling function, which is independent of the nature of the probe. In this work, we analyze the nucleon-density response function of $^{12}$C, neglecting collective excitations. We employ particle and hole spectral functions obtained within two distinct many-body methods, both widely used to describe electroweak reactions in nuclei. We show that the two approaches provide compatible nucleon-density scaling functions that for large momentum transfers satisfy first-kind scaling. Both methods yield scaling functions characterized by an asymmetric shape, although less pronounced than that of experimental scaling functions. This asymmetry, only mildly affected by final state interactions, is mostly due to nucleon-nucleon correlations, encoded in the continuum component of the hole SF., Comment: 15 pages, 11 figures

The precise measurement of neutrino properties is among the highest priorities in fundamental particle physics, involving many experiments worldwide. Since the experiments rely on the interactions of neutrinos with bound nucleons inside atomic nuclei, the planned advances in the scope and precision of these experiments requires a commensurate effort in the understanding and modeling of the hadronic and nuclear physics of these interactions, which is incorporated as a nuclear model in neutrino event generators. This model is essential to every phase of experimental analyses and its theoretical uncertainties play an important role in interpreting every result. In this White Paper we discuss in detail the impact of neutrino-nucleus interactions, especially the nuclear effects, on the measurement of neutrino properties using the determination of oscillation parameters as a central example. After an Executive Summary and a concise Overview of the issues, we explain how the neutrino event generators work, what can be learned from electron-nucleus interactions and how each underlying physics process - from quasi-elastic to deep inelastic scattering - is understood today. We then emphasize how our understanding must improve to meet the demands of future experiments. With every topic we find that the challenges can be met only with the active support and collaboration among specialists in strong interactions and electroweak physics that include theorists and experimentalists from both the nuclear and high energy physics communities.

We have performed the calculations for the nonleptonic $\Xi_b^- \rightarrow \pi^- \ \Xi_c^0 (2790) \left(J=\frac{1}{2}\right)$ and $\Xi_b^- \rightarrow \pi^- \ \Xi_c^0 (2815) \left(J=\frac{3}{2}\right)$ and the same reactions replacing the $\pi^-$ by a $D_s^-$. At the same time we evaluate the semileptonic rates for $\Xi_b^- \rightarrow \bar{\nu}_l l \ \Xi_c^0 (2790)$ and $\Xi_b^- \rightarrow \bar{\nu}_l l \ \Xi_c^0 (2815)$. We look at the reactions from the perspective that the $\Xi_c^0 (2790)$ and $\Xi_c^0 (2815)$ resonances are dynamically generated from the pseudoscalar-baryon and vector-baryon interactions. We evaluate ratios of the rates of these reactions and make predictions that can be tested in future experiments. We also find that the results are rather sensitive to the coupling of the $\Xi_c^*$ resonances to the $D^* \Sigma$ and $D^* \Lambda$ components., Comment: 12 pages, 5 figures

We have studied the scaling properties of the electromagnetic response functions of $^4$He and $^{12}$C nuclei computed by the Green's Function Monte Carlo approach, retaining only the one-body current contribution. Longitudinal and transverse scaling functions have been obtained in the relativistic and non relativistic cases and compared to experiment for various kinematics. The characteristic asymmetric shape of the scaling function exhibited by data emerges in the calculations in spite of the non relativistic nature of the model. The results are consistent with scaling of zeroth, first and second kinds. Our analysis reveals a direct correspondence between the scaling and the nucleon-density response functions., Comment: 11 pages, 15 figures

Understanding single pion production reactions on free nucleons is the first step towards a correct description of these processes in nuclei, which are important for signal and background contributions in current and near future accelerator neutrino oscillation experiments. In this work, we reanalyze our previous studies of neutrino-induced one-pion production on nucleons for outgoing $\pi N$ invariant masses below 1.4 GeV. Our motivation is to get a better description of the $\nu_\mu n\to\mu^- n\pi^+$ cross section, for which current theoretical models give values significantly below data. This channel is very sensitive to the crossed $\Delta (1232)$ contribution and thus to spin 1/2 components in the Rarita-Schwinger $\Delta$ propagator. We show how these spin 1/2 components are nonpropagating and give rise to contact interactions. In this context, we point out that the discrepancy with experiment might be corrected by the addition of appropriate extra contact terms and argue that this procedure will provide a natural solution to the $\nu_\mu n\to\mu^- n\pi^+$ puzzle. To keep our model simple, in this work we propose to change the strength of the spin 1/2 components in the $\Delta$ propagator and use the $\nu_\mu n\to\mu^- n\pi^+$ data to constraint its value. With this modification, we now find a good reproduction of the $\nu_\mu n\to\mu^- n\pi^+$ cross section without affecting the good results previously obtained for the other channels. We also explore how this change in the $\Delta$ propagator affects our predictions for pion photoproduction and find also a better agreement with experiment than with the previous model., Comment: 21 pages, 1 Table, 8 Figures. Enlarged introduction and discussion. One new figure, One new panel in Figure 1

Starting from a molecular picture for the X(3872) resonance, this state and its J^{PC}=2++ HQSS partner [X2(4012)] are analyzed within a model which incorporates possible mixings with 2P charmonium states. Since it is reasonable to expect the bare chi_{c1}(2P) to be located above the D\bar D* threshold, but relatively close to it, the presence of the charmonium state provides an effective attraction that will contribute to bind the X(3872), but it will not appear in the 2++ sector. Indeed in this latter sector, the chi_{c2}(2P) should provide an effective small repulsion, because it is placed well below the D*\bar D* threshold. We show how the 1++ and 2++ bare charmonium poles are modified due to the D(*)\bar D(*) loop effects, and the first one is moved to the complex plane. The meson loops produce, besides some shifts in the masses of the charmonia, a finite width for the 1++ dressed charmonium state. On the other hand, the X(3872) and X2(4012) start developing some charmonium content, which is estimated by means of the compositeness Weinberg sum-rule. We also show that for X(3872) molecular probabilities of around 70-90 %, the X2 resonance destabilizes and disappears from the spectrum, becoming either a virtual state or being located deep into the complex plane, with decreasing influence in the D* \bar D* scattering line., Comment: 46 pages, 5 figures; Accepted in EPJC

We consider a recent $T$-matrix analysis by Albaladejo {\it et al.}, [Phys.\ Lett.\ B {\bf 755}, 337 (2016)] which accounts for the $J/\psi\pi$ and $D^\ast\bar{D}$ coupled--channels dynamics, and that successfully describes the experimental information concerning the recently discovered $Z_c(3900)^\pm$. Within such scheme, the data can be similarly well described in two different scenarios, where the $Z_c(3900)$ is either a resonance or a virtual state. To shed light into the nature of this state, we apply this formalism in a finite box with the aim of comparing with recent Lattice QCD (LQCD) simulations. We see that the energy levels obtained for both scenarios agree well with those obtained in the single-volume LQCD simulation reported in Prelovsek {\it et al.} [Phys.\ Rev.\ D {\bf 91}, 014504 (2015)], making thus difficult to disentangle between both possibilities. We also study the volume dependence of the energy levels obtained with our formalism, and suggest that LQCD simulations performed at several volumes could help in discerning the actual nature of the intriguing $Z_c(3900)$ state.

Recent studies have shown that the well established $\Lambda_c(2595)$ resonance contains a large meson-baryon component, which can vary depending on the specific formalism. In this work, we examine such a picture by utilizing the compositeness condition and the large number of colors ($N_c$) expansion. We examine three different models fulfilling two body unitarity in coupled-channels, and adopting renormalization schemes where the mass of the $\Lambda_c(2595)$ resonance is well described, but not necessarily its width, since we do not consider three body channels and work at the isospin symmetric limit. Both approximations might have an effect larger on the width than on the mass. In this context, our studies show that the compositeness of the $\Lambda_c(2595)$ depends on the number of considered coupled channels, and on the particular regularization scheme adopted in the unitary approaches and, therefore, is model dependent. In addition, we perform an exploratory study of the $\Lambda_c(2595)$ in the large $N_c$ expansion, within a scheme involving only the $\pi\Sigma_c$ and $K\Xi'_c$ channels, whose dynamics is mostly fixed by chiral symmetry. In this context and formulating the leading-order interaction as a function of $N_c$, we show that for moderate $N_c> 3$ values, the mass and width of the $\Lambda_c(2595)$ deviate from those of a genuine $qqq$ baryon, implying the relevance of meson-baryon components in its wave function. Furthermore, we study the properties of the $\Lambda_c(2595)$, in the strict $N_c \to \infty $ limit, using an extension of the chiral Weinberg-Tomozawa interaction to an arbitrary number of flavors and colors. This latter study hints at the possible existence of a (perhaps) sub-dominant $qqq$ component in the $\Lambda_c(2595)$ resonance wave function, which would become dominant when the number of colors gets sufficiently large., Comment: 33 pages, 2 figures

Some of the recent progress in the physics of pion production induced by neutrinos on nucleons and nuclei is reviewed from a theoretical perspective. The importance of Watson's theorem to reconcile ANL and BNL data with the off-diagonal Goldberger-Treiman relation for the $\Delta(1232)$ is discussed. The disagreement between MiniBooNE data and theoretical calculations is presented in the light of the new MINERvA data. The coherent pion production data on $^{12}$C obtained by MINERvA are also compared to different microscopic and PCAC models., Comment: 8 pages, 4 figures, prepared for the Proceedings of the 10th International Workshop on Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt15)

We investigate the structure and formation of charmed meson--nucleus systems, with the aim of understanding the charmed meson--nucleon interactions and the properties of the charmed mesons in the nuclear medium. The $\bar{D}$ mesic nuclei are of special interest, since they have tiny decay widths due to the absence of strong decays for the $\bar{D} N$ pair. Employing an effective model for the $\bar{D} N$ and $D N$ interactions and solving the Klein--Gordon equation for $\bar{D}$ and $D$ in finite nuclei, we find that the $D^{-}$-${}^{11}\rm{B}$ system has $1 s$ and $2p$ mesic nuclear states and that the $D^{0}$-${}^{11}\rm{B}$ system binds in a $1s$ state. In view of the forthcoming experiments by the PANDA and CBM Collaborations at the future FAIR facility and the J-PARC upgrade, we calculate the formation spectra of the $[D^{-}$-${}^{11}\rm{B}]$ and $[D^{0}$-${}^{11}\rm{B}]$ mesic nuclei for an antiproton beam on a ${}^{12} \rm{C}$ target. Our results suggest that it is possible to observe the $2 p$ $D^{-}$ mesic nuclear state with an appropriate experimental setup., Comment: 8 pages, 5 figures

We present a new determination of the $N\Delta$ axial form factors from neutrino induced pion production data. For this purpose, the model of Hernandez {\it et al.} [Phys. Rev. D76, 033005 (2007)] is improved by partially restoring unitarity. This is accomplished by imposing Watson's theorem on the dominant vector and axial multipoles. As a consequence, a larger $C_5^A(0)$, in good agreement with the prediction from the off-diagonal Goldberger-Treiman relation, is now obtained., Comment: 17 latex pages, 7 figures, 2 tables. Some typos corrected

In this work, we study systems composed of a $\rho/\omega$ and $B^*$ meson pair. We find three bound states in isospin, spin-parity channels $(1/2, 0^+)$, $(1/2, 1^+)$ and $(1/2, 2^+)$. The state with $J=2$ can be a good candidate for the $B_2^*(5747)$. We also study the $\rho B$ system, and a bound state with mass $5728$ MeV and width around $20$ MeV is obtained, which can be identified with the $B_1(5721)$ resonance. In the case of $I=3/2$, one obtains repulsion and thus, no exotic (molecular) mesons in this sector are generated in the approach.

We perform a theoretical analysis of the $\Lambda_b \to J/\psi K^- p$ reaction from where a recent LHCb experiment extracts a $\Lambda(1405)$ contribution in the $K^- p$ spectrum close to threshold and two baryon states of hidden charm in the $J/\psi\,p$ spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and $J^P$ of the experiment, concretely some states built up from the $J/\psi\, N$, $\bar D^* \Lambda_c$, $\bar D^* \Sigma_c$, $\bar D \Sigma^*_c$ and $\bar D^* \Sigma^*_c$ coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the $K^- p$ mass distribution close to threshold and the peak of the $J/\psi\,p$ distribution, with values of the $J/\psi\, p$ coupling to the resonance in line with the theoretical ones. The non trivial matching of many properties gives support to a $J^P=3/2^-$ assignment to this state and to its nature as a molecular state mostly made of $\bar D^* \Sigma_c$ and $\bar D^* \Sigma^*_c$., Comment: 4 pages, 2 figures

We have applied a microscopic model for single photon emission in neutral current interactions on nucleons and nuclei to determine the number and distributions of such events at the Super-Kamiokande detector, for the flux and beam exposure of the T2K experiment in neutrino mode. These reactions represent an irreducible background in electron-(anti)neutrino appearance measurements aimed at a precise measurement of mixing angle $\theta_{13}$ and the $CP$ violating phase. We have obtained a total number of photon events that is twice larger than the one from the NEUT event generator (version 5.1.4.2) used in the analysis of T2K data. Detailed comparisons of energy and angular distributions for the $\nu_\mu$ and $\bar\nu_\mu$ fluxes have also been performed., Comment: 9 pages, 6 figures