Formation of Slow Heavy Mesons in Nuclei

Abstract We study ϕ meson production in the C 12 ( p ¯ , ϕ ) reaction at p p ¯ = 1.3 GeV/c . We also discuss the interest in and the difficulties of studying heavy meson-nucleus systems.

Possible omega bound states in nuclei produced with the (gamma, p) reaction

We perform calculations for ω production in nuclei by means of the (γ,p) reaction for photon energies and proton angles suited to currently running and future experiments in present laboratories. For some cases of possible ω optical potentials, we find that clear peaks are observable when a good resolution in the ω energy is available. We also study the inclusive production of π(0)γ in nuclei around the ω energy and find a double hump structure for the energy spectra, with a peak around a π(0)γ energy of m(ω) -100 MeV, which could easily be misidentified by a signal of an ω bound state in nuclei, while it is actually due to a different scaling of the uncorrelated π(0)γ production and ω prod…

Chiral unitary model for the kaonic atom

We study kaonic atoms over the periodic table using a kaon self-energy in the nuclear medium derived from the SU(3) chiral unitary model. This model is quite successful in reproducing the scattering amplitude of meson meson and the strangeness $S=\ensuremath{-}1$ meson baryon reactions. In particular the properties of the $\ensuremath{\Lambda}(1405)$ resonance are well reproduced. In the nuclear medium the properties of this resonance are appreciably modified, and consequently the kaon nucleon scattering amplitudes, leading to an attractive kaon nucleus self-energy for densities higher than ${\ensuremath{\rho}}_{0}/25.$ With this interaction we are able to reproduce shifts and widths of kao…

Recent progress on the chiral unitary approach to meson meson and meson baryon interactions

We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented. Results for the extension of these ideas to the meson baryon sector are discussed, together with applications to kaons in a nuclear medium and $K^-$ atoms.

Proton emission off nuclei induced by kaons in flight

We study the (K-, p) reaction on nuclei with a 1 GeV/c momentum kaon beam, paying special attention to the region of emitted protons having kinetic energy above 600 MeV, which was used to claim a deeply attractive kaon nucleus optical potential. Our model describes the nuclear reaction in the framework of a local density approach and the calculations are performed following two different procedures: one is based on a many-body method using the Lindhard function and the other is based on a Monte Carlo simulation. The simulation method offers flexibility to account for processes other than kaon quasielastic scattering, such as K- absorption by one and two nucleons, producing hyperons, and all…

Chiral loops and VMD in the V -> P P gamma decays

We evaluate radiative decays of rho and omega going to two neutral mesons, pi(0)pi(0) and pi(0)eta. We use the sequential vector decay mechanisms in addition to chiral loops and rho-omega mixing. The chiral loops are obtained using elements of UchiPT successfully applied in the study of meson-meson interactions up to 1.2 GeV. The chiral loops are found very important in the case of the rho --> pi(0)pi(0)gamma decay and small in the other cases. A good agreement with present measurements of rho --> pi(0)pi(0)gamma and omega --> pi(0)pi(0)gamma is obtained and predictions are made for the other decays where the rates obtained are rather small.

NUCLEAR EFFECTS IN NEUTRINO INDUCED REACTIONS

We discuss the relevance of nuclear medium effects in the analysis of some low and medium energy neutrino reactions of current interest. In particular, we study the Quasi-Elastic (QE) process, where RPA correlations and Final State Interactions (FSI) are shown to play a crucial role. We have also investigated the neutrino induced coherent pion production. We find a strong reduction of the cross section due to the distortion of the pion wave function and the modification of the production mechanisms in the nucleus. The sensitivity of the results to the axial $N\Delta$ coupling $C_5^A(0)$ has been also investigated.

Formation of Meson Nucleus Systems

Chiral unitary theory: Application to nuclear problems

In this talk we briefly describe some basic elements of chiral perturbation theory, $\chi PT$, and how the implementation of unitarity and other novel elements lead to a better expansion of the $T$ matrix for meson meson and meson baryon interactions. Applications are then done to the $ \pi \pi $ interaction in nuclear matter in the scalar and vector channels, antikaons in nuclei and $K^-$ atoms, and how the $\phi$ meson properties are changed in a nuclear medium.

Selected topics on Hadrons in Nuclei

In this talk we report on selected topics on hadrons in nuclei. The first topic is the renormalization of the width of the $\Lambda(1520)$ in a nuclear medium. This is followed by a short update of the situation of the $\omega$ in the medium. The investigation of the properties of $\bar{K}$ in the nuclear medium from the study of the $(K_{flight},p)$ reaction is also addressed, as well as properties of X,Y,Z charmed and hidden charm resonances in a nuclear medium. Finally we address the novel issue of multimeson states.

Radiative decay of rho(0) and phi mesons in a chiral unitary approach

We study the rho^0 and phi decays into pi^+ pi^- gamma, pi^0 pi^0 gamma and phi into pi^0 eta gamma using a chiral unitary approach to deal with the final state interaction of the M M system. The final state interaction modifies only moderately the large momenta tail of the photon spectrum of the rho^0 --> pi^+ pi^- gamma decay. In the case of phi decay the contribution to pi^+ pi^- gamma and pi^0 pi^0 gamma decay proceeds via kaonic loops and gives a distribution of pi pi invariant masses in which the f_0(980) resonance shows up with a very distinct peak. The spectrum found for phi --> pi^0 pi^0 gamma decay agrees with the recent experimental results obtained at Novosibirsk. The bran…

Production of Θ+ hypernuclei with the (K+,π+) reaction

Abstract We present results on the production of bound states of Θ + in nuclei using the ( K + , π + ) reaction. By taking into account the states obtained within a wide range of strength of the Θ + nucleus optical potential, plus the possibility to replace different nucleons of the nucleus, we obtain an excitation spectra with clearly differentiated peaks. The magnitude of the calculated cross sections is well within reachable range.

The (K-, p) reaction on nuclei with in-flight kaons

10th International Conference on Hypernuclear and Strange Particle Physics. Tokai, JAPAN, SEP 14-18, 2009

eta '-Nucleus optical potential and possible eta ' bound states

Starting from a recent model of the eta'N interaction, we evaluate the eta'-nucleus optical potential, including the contribution of lowest order in density, t rho/2m(eta'), together with the second-order terms accounting for eta' absorption by two nucleons. We also calculate the formation cross section of the eta' bound states from (pi(+), p) reactions on nuclei. The eta'-nucleus potential suffers from uncertainties tied to the poorly known eta'N interaction, which can be partially constrained by the experimental modulus of the eta'N scattering length and/or the recently measured transparency ratios in eta' nuclear photoproduction. Assuming an attractive interaction and taking the claimed …

Projectile Delta and target Roper excitation in the p(d,d ') X reaction

In this paper we compare a model that contains the mechanisms of Δ excitation in the projectile and Roper excitation in the target with experimental data from two (d, d') experiments on a proton target. The agreement of the theory with the experiment is fair for the data taken at T_d = 2.3 GeV. The Δ excitation in the projectile is predicted close to the observed energy with the correct width. The theory, however, underpredicts by about 40% the cross sections measured at T_d = 1.6 GeV at angles where the cross section has fallen by about two orders of magnitude. The analysis done here allows to extract an approximate strength for the excitation of the Roper [N^*(1440)] excitation and a qual…

Pion double charge exchange reactions leading to deeply bound double pionic atoms

We study theoretically pion double charge exchange reactions leading to double pionic atoms. The reaction cross-sections with two pions in the deeper bound pionic orbits in 208Pb are calculated with realistic pionic atom wave functions and distortion effects. The cross-sections are found to be d2σ/dEdΩ~10−3−10−4 µb/srMeV, which are only a small fraction of the double charge exchange background.

η′-Nucleus optical potential and possible η′ bound states

Abstract Starting from a recent model of the η ′ N interaction, we evaluate the η ′ -nucleus optical potential, including the contribution of lowest order in density, t ρ / 2 m η ′ , together with the second-order terms accounting for η ′ absorption by two nucleons. We also calculate the formation cross section of the η ′ bound states from ( π + , p ) reactions on nuclei. The η ′ -nucleus potential suffers from uncertainties tied to the poorly known η ′ N interaction, which can be partially constrained by the experimental modulus of the η ′ N scattering length and/or the recently measured transparency ratios in η ′ nuclear photoproduction. Assuming an attractive interaction and taking the c…

PION DOUBLE CHARGE EXCHANGE REACTIONS LEADING TO DOUBLE PIONIC ATOMS

We study theoretically pion double charge exchange reactions leading to double pionic atoms. The reaction cross-sections with two pions in the deeper bound pionic orbits in 208Pb are calculated with realistic pionic atom wave functions and distortion effects. The cross-sections are found to be d2σ/dEdΩ~10−3−10−4 µ b/srMeV , which are only a small fraction of the double charge exchange background.

ProjectileΔand target Roper excitation in thep(d,d′)Xreaction

In this paper we compare a model that contains the mechanisms of $\ensuremath{\Delta}$ excitation in the projectile and Roper excitation in the target with experimental data from two ${(d,d}^{\ensuremath{'}})$ experiments on a proton target. The agreement of the theory with the experiment is fair for the data taken at ${T}_{d}=2.3$ GeV. The $\ensuremath{\Delta}$ excitation in the projectile is predicted close to the observed energy with the correct width. The theory, however, underpredicts by about 40% the cross sections measured at ${T}_{d} = 1.6$ GeV at angles where the cross section has fallen by about two orders of magnitude. The analysis done here allows us to extract an approximate st…

PRODUCTION OF Θ+ HYPERNUCLEI WITH THE (K+, π+) REACTION

Abstract We present results on the production of bound states of Θ + in nuclei using the ( K + , π + ) reaction. By taking into account the states obtained within a wide range of strength of the Θ + nucleus optical potential, plus the possibility to replace different nucleons of the nucleus, we obtain an excitation spectra with clearly differentiated peaks. The magnitude of the calculated cross sections is well within reachable range.

Roper excitation in alpha-proton scattering

We study the Roper excitation in the $(\alpha,\alpha')$ reaction. We consider all processes which may be relevant in the Roper excitation region, namely, Roper excitation in the target, Roper excitation in the projectile, and double $\Delta$ excitation processes. The theoretical investigation shows that the Roper excitation in the proton target mediated by an isoscalar exchange is the dominant mechanism in the process. We determine an effective isoscalar interaction by means of which the experimental cross section is well reproduced. This should be useful to make predictions in related reactions and is a first step to construct eventually a microscopic $NN \rightarrow NN^*$ transition poten…

Possible ω bound states in nuclei produced with the (γ,p) reaction

We perform calculations for ω production in nuclei by means of the ( γ, p) reaction for photon energies and proton angles suited to currently running and future experiments in present laboratories. For some cases of possible ω optical potentials, we find that clear peaks are observable when a good resolution in the ω energy is available. We also study the inclusive production of π 0 γ in nuclei around the ω energy and find a double hump structure for the energy spectra, with a peak around a π 0 γ energy of mω − 100 MeV, which could easily be misidentified by a signal of an ω bound state in nuclei, while it is actually due to a different scaling of the uncorrelated π 0 γ production and ω pro…

Latest Results for the Antikaon-Nucleon Optical Potential

The key question of this letter is whether the K-nucleus optical potential is deep, as it is prefered by the phenomenological fits to kaonic atoms data, or shallow, as it comes out from unitary chiral model calculations. The current experimental situation is reviewed.

Charged current neutrino-induced coherent pion production

We analyze the neutrino induced charged current coherent pion production at the energies of interest for recent experiments like K2K and MiniBooNE. Medium effects in the production mechanism and the distortion of the pion wave function, obtained solving the Klein Gordon equation with a microscopic optical potential, are included in the calculation. We find a strong reduction of the cross section due to these effects and also substantial modifications of the energy distributions of the final lepton and pion.

Precision Spectroscopy of Deeply Bound Pionic Atoms and Partial Restoration of Chiral Symmetry in Medium

We study theoretically the formation spectra of deeply bound pionic atoms expected to be observed by experiments with high energy resolution at RIBF/RIKEN, and we discuss in detail the possibilities to extract new information on the pion properties at finite density from the observed spectra, which may provide information on partial restoration of chiral symmetry in medium. We find that the non-yrast pionic states such as 2s are expected to be seen in the (d,3He) spectra, which will be helpful to reduce uncertainties of the theoretical calculations in the neutron wave functions in nucleus. The observation of the 2s state with the ground 1s state is also helpful to reduce the experimental un…

Chiral loops and VMD in the V→PPγ decays

Abstract We evaluate radiative decays of ρ and ω going to two neutral mesons, π0π0 and π0η. We use the sequential vector decay mechanisms in addition to chiral loops and ρ–ω mixing. The chiral loops are obtained using elements of UχPT successfully applied in the study of meson–meson interactions up to 1.2 GeV. The chiral loops are found very important in the case of the ρ→π0π0γ decay and small in the other cases. A good agreement with present measurements of ρ→π0π0γ and ω→π0π0γ is obtained and predictions are made for the other decays where the rates obtained are rather small.

Formation of Heavy Meson Bound States by Two Nucleon Pick-up Reactions

We develop a model to evaluate the formation rate of the heavy mesic nuclei in the two nucleon pick-up reactions, and apply it to the $^6$Li target cases for the formation of heavy meson-$\alpha$ bound states, as examples. The existence of the quasi-deuteron in the target nucleus is assumed in this model. It is found that the mesic nuclei formation in the recoilless kinematics is possible even for heavier mesons than nucleon in the two nucleon pick-up reactions. We find the formation rate of the meson-$\alpha$ bound states can be around half of the elementary cross sections at the recoilless kinematics with small distortions.

Meson and baryon resonances

6 pages, 1 table.-- PACS nrs.: 13.75.Lb, 14.40.Cs, 12.40.Vv, 12.40.Yx.-- Talk at the 2008 International Conference on Particles And Nuclei (PANIC08, Nov 9-14, 2008, Eilat, Israel).

Coherent π0 electroproduction

Abstract We analyze the coherent electroproduction of neutral pions in nuclei. We find that this process does not contribute to the longitudinal response function for spin saturated nuclei and the dependence of the cross section on the azimuthal pion angle is particularly simple and given by 1− ϵ cos 2 o π . This angular dependence could be useful to isolate the coherent contribution in future experiments, offering an advantage over coherent photoproduction. The Δ-peak is considerably moved to lower pion energies and appreciably modified due to medium corrections.

gamma gamma decay of the f(0)(1370) and f(2)(1270) resonances in the hidden gauge formalism

Using recent results obtained within the hidden gauge formalism for vector mesons, in which the f0(1370) and f2(1270) resonances are dynamically generated resonances from the ρρ interaction, we evaluate the radiative decay of these resonances into γγ. We obtain results for the width in good agreement with the experimental data for the f2(1270) state and a width about a factor five smaller for the f0(1370) resonance, which would agree with preliminary results from the Belle collaboration, hinting at an order of magnitude smaller width for this resonance than for the f2(1270).