Dijon, A. et al, & Gadea, A. (2011). Lifetime measurements in Co-63 and Co-65. Phys. Rev. C, 83(6), 064321–7pp.
Abstract: Lifetimes of the 9/2(1)(-) and 3/2(1)(-) states in Co-63 and the 9/2(1)(-) state in Co-65 were measured using the recoil distance Doppler shift and the differential decay curve methods. The nuclei were populated by multinucleon transfer reactions in inverse kinematics. gamma rays were measured with the EXOGAM Ge array and the recoiling fragments were fully identified using the large-acceptance VAMOS spectrometer. The E2 transition probabilities from the 3/2(1)(-) and 9/2(1)(-) states to the 7/2(-) ground state could be extracted in Co-63 as well as an upper limit for the 9/2(1)(-) -> 7/2(1)(-) B(E2) value in Co-65. The experimental results were compared to large-scale shell-model calculations in the pf and pfg(9/2) model spaces, allowing us to draw conclusions on the single-particle or collective nature of the various states.
|
Xie, J. J., Martinez Torres, A., & Oset, E. (2011). Faddeev fixed-center approximation to the N K K(bar) system and the signature of a N*(1920)(1/2+) state. Phys. Rev. C, 83(6), 065207–8pp.
Abstract: We perform a calculation for the three-body N (K) over barK scattering amplitude by using the fixed-center approximation to the Faddeev equations, taking the interaction between N and (K) over bar, N and K, and (K) over bar and K from the chiral unitary approach. The resonant structures show up in the modulus squared of the three-body scattering amplitude and suggest that a N (K) over barK hadron state can be formed. Our results are in agreement with others obtained in previous theoretical works, which claim a new N* resonance around 1920 MeV with spin-parity J(P) = 1/2(+). The existence of these previous works allows us to test the accuracy of the fixed center approximation in the present problem and sets the grounds for possible application in similar problems, as an explorative tool to determine bound or quasibound three-hadron systems.
|
Bayar, M., Yamagata-Sekihara, J., & Oset, E. (2011). K-bar NN system with chiral dynamics. Phys. Rev. C, 84(1), 015209–9pp.
Abstract: We have performed a calculation of the scattering amplitude for the three-body system (K) over bar NN assuming (K) over bar scattering against a NN cluster using the fixed center approximation to the Faddeev equations. The (K) over bar N amplitudes, which we take from chiral unitary dynamics, govern the reaction and we find a (K) over bar NN amplitude that peaks around 40 MeV below the (K) over bar NN threshold, with a width in |T|(2) of the order of 50 MeV for spin 0 and has another peak around 27 MeV with similar width for spin 1. The results are in line with those obtained using different methods but implementing chiral dynamics. The simplicity of the approach allows one to see the important ingredients responsible for the results. In particular, we show the effects from the reduction of the size of the NN cluster due to the interaction with the (K) over bar and those from the explicit consideration of the pi Sigma N channel in the three-body equations.
|
n_TOF Collaboration(Tagliente, G. et al.), Domingo-Pardo, C., & Tain, J. L. (2011). Neutron capture on (94)Zr: Resonance parameters and Maxwellian-averaged cross sections. Phys. Rev. C, 84(1), 015801–9pp.
Abstract: The neutron capture cross sections of the Zr isotopes play an important role in nucleosynthesis studies. The s-process reaction flow between the Fe seed and the heavier isotopes passes through the neutron magic nucleus (90)Zr and through (91,92,93,94)Zr, but only part of the flow extends to (96)Zr because of the branching point at (95)Zr. Apart from their effect on the s-process flow, the comparably small isotopic (n, gamma) cross sections make Zr also an interesting structural material for nuclear reactors. The (94)Zr (n, gamma) cross section has been measured with high resolution at the spallation neutron source n_TOF at CERN and resonance parameters are reported up to 60 keV neutron energy.
|
Wu, J. J., Molina, R., Oset, E., & Zou, B. S. (2011). Dynamically generated N* and Lambda* resonances in the hidden charm sector around 4.3 GeV. Phys. Rev. C, 84(1), 015202–15pp.
Abstract: The interactions of (D) over bar Sigma(c)-(D) over bar Lambda(c), (D) over bar*Sigma(c)-(D) over bar*Lambda(c), and related strangeness channels, are studied within the framework of the coupled-channel unitary approach with the local hidden gauge formalism. A series of meson-baryon dynamically generated relatively narrow N* and Lambda* resonances are predicted around 4.3 GeV in the hidden charm sector. We make estimates of production cross sections of these predicted resonances in (p) over barp collisions for the experiment of antiproton annihilation at Darmstadt (PANDA) at the forthcoming GSI Facility for Antiproton and Ion Research (FAIR) facility.
|
Morales, A. I. et al, Agramunt, J., Algora, A., Gadea, A., Molina, F., & Rubio, B. (2011). Synthesis of N=127 isotones through (p,n) charge-exchange reactions induced by relativistic (208)Pb projectiles. Phys. Rev. C, 84(1), 011601–5pp.
Abstract: The production cross sections of four N = 127 isotones ((207)Hg, (206)Au, (205)Pt, and (204)Ir) have been measured using (p,n) charge-exchange reactions, induced in collisions of a (208)Pb primary beam at 1 A GeV with a Be target. These data allow one to investigate the use of a reaction mechanism to extend the limits of the chart of nuclides toward the important r-process nuclei in the region of the third peak of elemental abundance distribution.
|
Szilner, S. et al, & Gadea, A. (2011). Interplay between single-particle and collective excitations in argon isotopes populated by transfer reactions. Phys. Rev. C, 84(1), 014325–7pp.
Abstract: New gamma transitions have been identified in argon isotopes in (40)Ar + (208)Pb multiple transfer reactions by exploiting, in a fragment-gamma measurement, the new generation of magnetic spectrometers based on trajectory reconstruction coupled to large gamma arrays. The coupling of single-particle degrees of freedom to nuclear vibration quanta was discussed. The interpretation of the newly observed states within a particle-phonon coupling picture was used to consistently follow, via their excitation energies, the evolution of collectivity in odd Ar isotopes. The proposed level schemes are supported by the results of sd-pf shell-model calculations, which have been also employed to evaluate the strength functions of the populated states.
|
Dillmann, I., Coquard, L., Domingo-Pardo, C., Kappeler, F., Marganiec, J., Uberseder, E., et al. (2011). Cross sections for proton-induced reactions on Pd isotopes at energies relevant for the gamma process. Phys. Rev. C, 84(1), 015802–11pp.
Abstract: Proton-activation reactions on natural and enriched palladium samples were investigated via the activation technique in the energy range of E(p) = 2.75-9 MeV, close to the upper end of the respective Gamow window of the. process. We have determined cross sections for (102)Pd(p,gamma)(103)Ag, (104)Pd(p,gamma)(105)Ag, and (105)Pd(p,n)(105)Ag, as well as partial cross sections of (104)Pd(p,n)(104)Ag(g), (105)Pd(p,gamma)(106)Ag(m), (106)Pd(p,n)(106)Ag(m), and (110)Pd(p,n)(110)Ag(m) with uncertainties between 3% and 15% for constraining theoretical Hauser-Feshbach rates and for direct use in gamma-process calculations.
|
Pavon Valderrama, M., & Ruiz Arriola, E. (2011). Renormalization of chiral two-pion exchange NN interactions with Delta excitations: Correlations in the partial-wave expansion. Phys. Rev. C, 83(4), 044002–19pp.
Abstract: In this work we consider the renormalization of the chiral two-pion exchange potential with explicit Delta excitations for nucleon-nucleon scattering at next-to-leading (NLO) and next-to-next-to-leading order (N(2)LO). Because of the singular nature of the chiral potentials, correlations between different partial waves are generated. In particular, we show that two-body scattering by a short distance power like singular attractive interaction can be renormalized in all partial waves with a single counterterm, provided the singularities are identical. A parallel statement holds in the presence of tensor interactions when the eigenpotentials in the coupled channel problem also coincide. Although this construction reduces the total number of counterterms to 11 in the case of nucleon-nucleon scattering with chiral two-pion exchange interactions with Delta degrees of freedom, the differences in the scattering phases as compared to the case with the uncorrelated partial-wave renormalization become smaller as the angular momentum is increased in the elastic scattering region.
|
Pavon Valderrama, M. (2011). Perturbative renormalizability of chiral two-pion exchange in nucleon-nucleon scattering. Phys. Rev. C, 83(2), 024003–11pp.
Abstract: We study the perturbative renormalizability of chiral two-pion exchange for singlet and triplet channels within effective field theory, provided that the one-pion exchange piece of the interaction has been fully iterated. We determine the number of counterterms/subtractions needed to obtain finite results when the cutoff is removed, resulting in three counterterms for the singlet channel and six for the triplet. The results show that perturbative chiral two-pion exchange reproduce the data up to a center-of-mass momentum of k similar to 200-300 MeV in the singlet channel and k similar to 300-400 MeV in the triplet.
|
