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We review our theoretical approach to neutral current photon emission on nucleons and nuclei in the few-GeV energy region, relevant for neutrino oscillation experiments. These reactions are dominated by the weak excitation of the Δ(1232) resonance but there are also important non-resonant contributions. We have also included terms mediated by nucleon excitations from the second resonance region. On nuclei, Pauli blocking, Fermi motion and the in-medium Δ resonance broadening have been taken into account for both incoherent and coherent reaction channels. With this model, the number and distributions of photon events at the MiniBooNE and T2K experiments have been obtained. We have also compared to the NOMAD upper limit at higher energies. The implications of our findings and future perspectives are discussed. [ABSTRACT FROM AUTHOR]

We improve the model of Phys. Rev. D 76, 033005 (2007) for single pion production by neutrinos off the nucleon by partially restoring unitarity. To that end we impose Watson's theorem on the dominant vector and axial multipoles. As a result a larger CA5(0) value, in better agreement with the one obtained from the off-diagonal Goldberger-Treiman relation, is now needed in order to describe the experimental data. [ABSTRACT FROM AUTHOR]

We have studied quasielastic charged current hyperon production induced by νμ on free nucleon and the nucleons bound inside the nucleus and the results are presented for several nuclear targets like 40Ar, 56Fe and 208Pb. The hyperonnucleon transition form factors are determined from neutrino-nucleon scattering and semileptonic decays of neutron and hyperons using SU(3) symmetry. The nuclear medium effects(NME) due to Fermi motion and final state interaction(FSI) effect due to hyperon-nucleon scattering have been taken into account. Also we have studied two pion production at threshold induced by neutrinos off nucleon targets. The contribution of nucleon, pion, and contact terms are calculated using Lagrangian given by nonlinear σ model. The contribution of the Roper resonance has also been taken into account. The numerical results for the cross sections are presented and compared with the experimental results from ANL and BNL. [ABSTRACT FROM AUTHOR]

We analyze the MiniBooNE muon neutrino CCQE-like dσ/dTμdcosθμ data using a theoretical model that, among other nuclear effects, includes RPA correlations and 2p2h (multinucleon) mechanisms. These corrections turn out to be essential for the description of the data. We find that MiniBooNE CCQE-like data are fully compatible with former determinations of the nucleon axial mass MA ~ 1.05 GeV. This is in sharp contrast with several previous analysis where anomalously large values of MA ~ 1.4 GeV have been suggested. We also show that because of the the multinucleon mechanism effects, the algorithm used to reconstruct the neutrino energy is not adequate when dealing with quasielastic-like events. Finally, we analyze the MiniBooNE unfolded cross section, and show that it exhibits an excess (deficit) of low (high) energy neutrinos, which is an artifact of the unfolding process that ignores 2p2h mechanisms. [ABSTRACT FROM AUTHOR]

We report on our study of photon emission induced by Eν ~ 1 GeV (anti)neutrino neutral current interactions with nucleons and nuclei. This process is an important background for νe appearance oscillation experiments. At the relevant energies, the reaction is dominated by the excitation of the Δ(1232) resonance but there are also non-resonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. We have obtained differential and integrated cross section for the (anti)neutrino-nucleon scattering and compare them with previous results. Furthermore, we have extended the model to nuclear targets taking into account Fermi motion, Pauli blocking and the in-medium modifications of the Δ properties. This study is important in order to reduce systematic effects in neutrino oscillation experiments. [ABSTRACT FROM AUTHOR]

We use our model for neutrino pion production on the nucleon to study pion production on a nucleus. The model is conveniently modified to include in-medium corrections and its validity is extended up to 2 GeV neutrino energies by the inclusion of new resonant contributions in the production process. Our results are compared with recent MiniBooNE data measured in mineral oil. Our total cross sections are below data for neutrino energies above ≈ 1 GeV. As with other theoretical calculations, the agreement with data improves if we neglect pion final state interaction. This is also the case for differential cross sections convoluted over the neutrino flux. [ABSTRACT FROM AUTHOR]

We investigate the Λ(1520) photoproduction in the γp→K+Λ (1520) reaction within the effective Lagrangian method near threshold. In addition to the "background" contributions from the contact, t-channel K exchange, and s-channel nucleon pole terms, which were already considered in previous works, the contribution from the nucleon resonance N* (2080) (spin-parity JP = 3/2-) is also considered. We show that the inclusion of the nucleon resonance N* (2080) leads to a fairly good description of the new LEPS differential cross-section data, and that these measurements can be used to determine some of the properties of this latter resonance. [ABSTRACT FROM AUTHOR]

In this work we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on shell approach for the scattering matrix, commonly used, is also obtained in Quantum Mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two Λ(1405) states in the πΣ, KN and other coupled channels. It also offers a practical way to study three body systems when two of them cluster into a resonance. [ABSTRACT FROM AUTHOR]

We analyze the effects of hyperfine mixing in b→c semileptonic and electromagnetic decays of doubly heavy baryons. [ABSTRACT FROM AUTHOR]

We follow a model based on the SU(8) symmetry for the interaction of mesons with baryons. The model treats on an equal footing the pseudo-scalars and the vector mesons, as required by heavy quark symmetry. The T-matrix calculated within an unitary scheme in coupled channels has poles which are interpreted as baryonic resonances. [ABSTRACT FROM AUTHOR]

We have studied isospin breaking effects in the X(3872) resonance and found a natural explanation for the branching fraction of the X decaying to J/Ψ with two and three pions being close to unit. Within our framework the X(3872) is a dynamically generated resonance in coupled channels. We also study the relationship between the couplings of the resonance to the coupled channels with its wave function, which further helps us to understand the isospin structure of the resonance. [ABSTRACT FROM AUTHOR]

We obtain the properties of charmed mesons in dense matter using a coupled-channel approach which accounts for Pauli blocking effects and meson self-energies in a self-consistent manner. We study the behaviour of dynamically-generated baryonic resonances together with the open-charm meson spectral functions in this dense nuclear environment. We discuss the implications of the in-medium properties of open-charm mesons on the Ds0(2317) and the predicted X(3700) scalar resonances, and on the formation of D-mesic nuclei. [ABSTRACT FROM AUTHOR]

We review the main nuclear effects that affect neutrino-nucleus cross sections. We discuss how the different models in the literature try to describe these different effects, and thus try to compare between them. We focus on the quasi-elastic reaction in the neutrino energy region of around 1 GeV, where recent data from MiniBooNE are available. Among the issues discussed are the different treatment of medium corrections to initial and final state nucleon wave functions and the problem of the rescattering of ejected nucleons. [ABSTRACT FROM AUTHOR]

We discuss different parameterizations of the C5A(q2) NΔ form factor, fitted to the old Argonne bubble chamber data for pion production by neutrinos, and we use coherent pion production to test their low q2 behavior. We find moderate effects that will be difficult to observe with the accuracy of present experiments. We also discuss the use of the Rein-Sehgal model for low energy coherent pion production. By comparison to a microscopic calculation, we show the weaknesses some of the approximations in that model that lead to very large cross sections as well as to the wrong shapes for differential ones. Finally we show that models based on the partial conservation of the axial current hypothesis are not fully reliable for differential cross sections that depend on the angle formed by the pion and the incident neutrino. [ABSTRACT FROM AUTHOR]

This summary of “the path forward” session of the NuInt09 workshop focuses on neutrino-induced coherent pion production. The main question raised as part of this discussion was whether or not we adequately understand neutral current (NC) and charged current (CC) coherent pion production at low and intermediate neutrino energies. In this work, several experts in the field summarize their views, as presented at the workshop. [ABSTRACT FROM AUTHOR]

We present a microscopic model for neutrino induced one-pion production off the nucleon and its implementation for the purpose of calculating coherent pion production in nuclei. We further criticize the use of the Rein-Sehgal model for coherent pion production by low energy neutrinos. In particular, we show how the approximations in that model give rise to a much flatter differential cross section in the η = Eπ(1-cos θπ) variable. We discuss the limitations intrinsic to any approach based on the partial conservation of the axial current hypothesis and the inability of such models to properly determine the angular distribution of the outgoing pion with respect to the direction of the incoming neutrino. We show the effects of those limitation for the case of the dσdη differential cross section. [ABSTRACT FROM AUTHOR]

We review the general interplay between Nuclear Physics and neutrino-nucleus cross sections at intermediate and high energies. The effects of different reaction mechanisms over the neutrino observables are illustrated with examples in calculations using several nuclear models and ingredients. [ABSTRACT FROM AUTHOR]

The Quasi-Elastic (QE) contribution of the nuclear inclusive electron model developed in reference [1] is extended to the study of neutrino/antineutrino Charged Current (CC) and Neutral Current (NC) induced nuclear reactions at intermediate energies. Long range nuclear (RPA) correlations, Final State Interaction (FSI) and Coulomb corrections are included within the model. RPA correlations are shown to play a crucial role in the whole range (100–500 MeV) of studied neutrino energies. Results for inclusive muon capture for different nuclei through the Periodic Table are also discussed. In addition, and by means of a Monte Carlo cascade method to account for the rescattering of the outgoing nucleon, we also study the CC and NC inclusive one nucleon knockout reactions off nuclei. [ABSTRACT FROM AUTHOR]

We construct a model for the weak pion production off the nucleon, which in addition to the weak excitation of the Δ(1232) resonance and its subsequent decay into Nπ, it includes also some background terms required by chiral symmetry. We re-fit the C5A(q2) form factor to the flux averaged νμp→μ-pπ+ ANL q2-differential cross section data, finding a substantially smaller contribution of the Δ pole mechanism than traditionally assumed in the literature. We also show that the interference between the Delta pole and the background terms produces parity-violating contributions to the pion angular differential cross section. [ABSTRACT FROM AUTHOR]

We study the electromagnetic properties of a system that consists of an electron background and a neutrino gas that may be moving or at rest, as a whole, relative to the background. The photon self-energy for this system is characterized by the usual transverse and longitudinal polarization functions, and two additional ones which are the focus of our calculations, that give rise to birefringence and anisotropic effects in the photon dispersion relations. We consider the macroscopic electrodynamic equations for the above system, and discuss the evolution of a magnetic field perturbation in such a medium. This particular phenomena has also been considered by others as a mechanism for the generation of large-scale magnetic fields in the Early Universe as a consequence of the neutrino-plasma interactions. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We evaluate masses of bottom and charmed baryons using several non-relativistic quark potentials which parameters have been adjusted to the meson spectra. Heavy Quark Symmetry leads to important simplifications of the three body problem, which turns out to be easily solved by a simple variational ansatz. The wave functions obtained can be readily used to compute further observables as mass densities or form factors. The quark-quark potentials explored so far, show an overall good agreement with the experimental masses. [ABSTRACT FROM AUTHOR]

Meson-Baryon Interactions can be successfully described using both Chiral Symmetry and Unitarity. The s--wave meson-baryon scattering amplitude is analyzed in a Bethe-Salpeter coupled channel formalism incorporating Chiral Symmetry in the potential. Two body coupled channel unitarity is exactly preserved. The needed two particle irreducible matrix amplitude is taken from lowest order Chiral Perturbation Theory in a relativistic formalism. Off-shell behavior is parameterized in terms of low energy constants. The relation to the heavy baryon limit is discussed. The position of the complex poles in the second Riemann sheet of the scattering amplitude determine masses and widths baryonic resonances of the N(1535), N(1670), Λ(1405) and Λ(1670) resonances which compare well with accepted numbers. [ABSTRACT FROM AUTHOR]

We re-evaluate our model predictions in Phys. Rev. D 79, 013002 (2009) for different observables in neutrino induced coherent pion production. This comes as a result of the new improved fit to old bubble chamber data of the dominant axial C5A nucleon-to-Delta form factor. We find an increase of 20%∼30% in the values for the total cross sections. Uncertainties induced by the errors in the determination of C5A are computed. Our new results turn out to be compatible within about 1σ with the former ones. We also stress the existing tension between the recent experimental determination of the σ(CCcohπ+)/σ(NCcohπ0) ratio by the SciBooNE Collaboration and the theoretical predictions. [ABSTRACT FROM AUTHOR]

We consider the role played by hyperfine mixing in electromagnetic and semileptonic decays of doubly heavy baryons, which give rise to large corrections to the decay widths in both cases. Our results qualitatively agree with other calculations. [ABSTRACT FROM AUTHOR]

The neutrino pion production off the nucleon is traditionally described in the literature by means of the weak excitation of the Δ(1232) resonance and its subsequent decay into Nπ. Here, we present results from a model that includes also some background terms required by chiral symmetry. We show that the contribution of these terms is sizeable and leads to significant effects in total and partially integrated pion production cross sections at intermediate energies of interest for neutrino oscillation experiments. Finally, we discuss parity-violating contributions to the pion angular differential cross section induced by the interference of these non-resonant terms with the Δ piece. [ABSTRACT FROM AUTHOR]

The semileptonic decay B → πlνl is studied starting from a simple quark model and taking into account the effect of the B* resonance. A novel, multiply subtracted, Omnès dispersion relation has been implemented to extend the predictions of the quark model to all physical q2 values. We find |Vub| = 0.0034 ± 0.0003(exp.) ± 0.0007(theory), in good agreement with experiment. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Working in the framework of a nonrelativistic quark model we evaluate the widths for the strong one-pion decays Σc → Λc π, Σc* → Λc π and [cap_xi]c* → [cap_xi]c π. We take advantage of the constraints imposed by heavy quark symmetry to solve the three-body problem by means of a simple variational ansatz. We use partial conservation of the axial current hypothesis to get the strong vertices from weak axial current matrix elements. Our results are in good agreement with experimental data. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We evaluate the widths for the strong decays Σc → Λc π, Σc* → Λc π and [cap_xi]c* → [cap_xi]c π. The calculations have been done within a nonrelativistic constituent quark model with wave functions that take advantage of the constraints imposed by heavy quark symmetry. Partial conservation of axial current hypothesis allows us to determine the strong vertices from an analysis of the weak axial current matrix elements. Our results are in good agreement with experimental data. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Working in the framework of a nonrelativistic quark model we evaluate the widths for the strong one-pion decays Σc → Λc π, Σc* → Λc π and [cap_xi]c* → [cap_xi]c π. We take advantage of the constraints imposed by heavy quark symmetry to solve the three-body problem by means of a simple variational ansatz. We use partial conservation of the axial current hypothesis to get the strong vertices from weak axial current matrix elements. Our results are in good agreement with experimental data. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]