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1.
2.
Differential cross sections of nucleons excited in photonuclear reactions in medium and heavy nuclei are studied by considering all relevant reaction mechanisms leading to the excitation of protons or neutrons. We take advantage of previous microscopic studies for the absorption and scattering of photons and photoproduced pions, and implement a simulation code in order to take into account the propagation of the nucleons as well as their collisions with other nucleons in the nuclear medium, which generate secondary excited nucleons. Comparison with experimental data is done. Cross sections for nucleon emission in coincidence with one pion are also calculated, and some coincidence observables are discussed. 相似文献
3.
We study the reaction
– +A + (A
–) with the – bound in the nucleus, as a means of producing deeply bound pionic states in nuclei, so far unobserved. The reaction is similar to the (n, p) reaction but, because of the
–, mass difference, it allows the reaction to occur with smaller momentum transfer, thus increasing the transition probability and reducing the effects of distortion. The ratios of signal to background are one to two orders of magnitude better than in the (n, p) reaction.We would like to thank C. Dover and G. Tamas who helped us to get a perspective of the present and future possibilities of this and other reactions.One of us, J. Nieves wishes to acknowledge a fellowship from the Ministerio de Educatión y Ciencia. This work is partially supported by the CICYT. All the calculations have been done in the Centro Informático de la Universidad de Valencia. 相似文献
4.
M. D?ring U. -G. Mei?ner E. Oset A. Rusetsky 《The European Physical Journal A - Hadrons and Nuclei》2012,48(8):1-18
Phase shifts and resonance parameters can be obtained from finite-volume lattice spectra for interacting pairs of particles, moving with non-zero total momentum. We present a simple derivation of the method that is subsequently applied to obtain the ?Ц? and ??K phase shifts in the sectors with total isospin I = 0 and I = 1/2 , respectively. Considering different total momenta, one obtains extra data points for a given volume that allow for a very efficient extraction of the resonance parameters in the infinite-volume limit. Corrections due to the mixing of partial waves are provided. We expect that our results will help to optimize the strategies in lattice simulations, which aim at an accurate determination of the scattering and resonance properties. 相似文献
5.
A. Martınez Torres K. P. Khemchandani E. Oset 《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):295-297
We discuss the dynamical generation of some low-lying 1/2+ Σ 's and Λ 's in two-meson one-baryon systems. These systems have been constructed by adding a pion in the S -wave to the ˉN pair and its coupled channels, where the 1/2- Λ(1405) -resonance gets dynamically generated. We solve Faddeev equations in the coupled-channel approach to calculate the
T -matrix for these systems as a function of the total energy and the invariant mass of one of the meson-baryon pairs. This
squared T -matrix shows peaks at the energies very close to the masses of the strangeness -1 , 1/2+ resonances listed in the particle data book. 相似文献
6.
The K- p --> pi0pi0sigma0 reaction is studied within a chiral unitary model. The distribution of pi0sigma0 states forming the lambda(1405) shows, in agreement with a recent experiment, a peak at 1420 MeV and a relatively narrow width of gamma = 38 MeV. The mechanism for the reaction is largely dominated by the emission of a pi0 prior to the K- p interaction leading to the lambda(1405). This ensures the coupling of the lambda(1405) to the K- p channel, thus maximizing the contribution of the second state found in chiral unitary theories, which is narrow and of higher energy than the nominal lambda(1405). This is unlike the pi- p --> K0pisigma reaction, which gives more weight to the pole at lower energy and with a larger width. The data of these two experiments, together with the present theoretical analysis, provide firm evidence of the two-pole structure of the lambda(1405). 相似文献
7.
Bao-Xi Sun Hua-Xing Chen E. Oset 《The European Physical Journal A - Hadrons and Nuclei》2011,47(10):127
The ρρN and ρρΔ three-body systems have been studied within the framework of the fixed center approximation of Faddeev equation. The ρρ interaction in isospin I = 0 , spin S = 2 is strongly attractive, and so are the N ρ, ρΔ interactions. This leads to bound states of both ρρN and ρρΔ. We find peaks of the modulus squared of the scattering matrix around 2227 MeV for ρρN, and 2372 MeV for ρρΔ. Yet, the strength of the peak for the ρρN amplitude is much smaller than for ρρΔ, weakening the case for a ρρN bound state, or a dominant ρρN component. A discussion is made on how these states can be searched for in present programs looking for multimeson final
states in different reactions. 相似文献
8.
We generalise the operations of augmentation and concatenations defined in Cooper et al. (Compos Math 131(2):121–160, 2002) in order to obtain multigerms of analytic (or smooth) maps \((\mathbb {K}^n,S)\rightarrow (\mathbb {K}^p,0)\) with \(\mathbb {K}=\mathbb {C}\) or \(\mathbb {R}\) from monogerms and some special multigerms. We then prove that any corank 1 codimension 2 multigerm in Mather’s nice dimensions \((n,p)\) with \(n\ge p-1\) can be constructed using augmentations and these operations. 相似文献
9.
The problem of inclusive radiative pion capture is reanalyzed from a many-body point of view which allows to investigate effects like the Pauli blocking and the polarization of the medium by the spin-isospin interaction in a systematic way. Standard approximations are improved by means of this method, which is however much simpler technically than other available methods and very transparent. Results are presented for a variety of nuclei and the branching ratios for the capture rates are in overall agreement with experiment. The energy distribution of the photons is narrower than experiment and several mechanisms to solve these discrepancies are examined. 相似文献
10.
L. Roca C. Hanhart E. Oset U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2006,27(3):373-380
The Λ(1520)-resonance has been recently studied in a unitarized coupled-channel formalism with πΣ(1385), KΞ(1530), ˉN and πΣ as constituents blocks. We provide a theoretical study of the predictions of this model in physical observables of
the pp → pK+K-p and pp → pK+π0π0Λ reactions. In particular, we show that the ratio between the π0π0Λ and K-p mass distributions can provide valuable information on the ratio of the couplings of the Λ(1520)-resonance to πΣ(1385) and
ˉN than the theory predicts. Calculations are done for energies which are accessible in an experimental facility like COSY at
Jülich or the developing CSR facility at Lanzhou. 相似文献