Search results for "nucleus"
showing 10 items of 1803 documents
Anomalous transition strength in the proton-unbound nucleus I5653109
2011
A lifetime measurement has been made for the first excited 11/2(+) state in the proton-unbound nucleus (109)(53)I56 using the recoil-distance Doppler-shift method in conjunction with recoil-proton ...
First observation of gamma-rays from the proton emitter 171Au
2003
Gamma-rays from the alpha- and proton-unstable nuclide 171Au have been observed for the first time. The gamma-rays were correlated with both a proton- and an alpha-particle decay branch, confirming that the nucleus decays by alpha and proton emission from a single (11/2-) state. The measurement confirms the previously determined half-lives for these particle decays but the present values are of higher precision. In addition, a longer half-life than determined in previous work was measured for the proton-unstable tentative ground state. The results are discussed in relation to structures in neighbouring nuclei and compared with a Strutinsky-type TRS calculation.
Photoproduction of the Lambda(1405) on the proton and nuclei
1999
We study the gamma p ---> K^+ Lambda(1405) reaction at energies close to threshold using a chiral unitary model where the resonance is generated dynamically from K^-p interaction with other channels constructed from the octets of baryons and mesons. Predictions are made for cross sections into several channels and it is shown that the detection of the K^+ is sufficient to determine the shape and strength of the Lambda(1405) resonance. The determination of the resonance properties in nuclei requires instead the detection of the resonance decay channels. Pauli blocking effects on the resonance, which have been shown to be very important for the resonance at rest in the nucleus, are irrelev…
Excited states of111I and the observation of a 21 ns isomer
1994
Proton rich nuclei close to 100 Sn have been investigated inbeam using the NORDBALL detector array. A beam of 270 MeV58 Ni was used to bombard a 54 Fe target. Reaction channel separation was achieved with a 4π charged particle multi-detector set-up together with a 1π neutron detector wall placed in the forward direction. Gamma-ray transitions belonging to the 111 I nucleus were identified for the first time. A level scheme constructed from γ-γ-particle-coincidence analysis is proposed. The level structure is discussed within the framework of the shell model and the systematics of the heavier odd iodine nuclei.
Nuclear stucture studies of transfermium nuclei
2007
The study of deformed nuclei in the region of 254No provides an indirect method to access the single-particle orbitals which are of relevance in determining the location of the next closed proton and neutron closed shells above 208Pb. Several of these orbitals are strongly down-sloping and are close to the Fermi surface in the deformed region. These nuclei are some of the heaviest for which detailed spectroscopy can be performed. Initial in-beam measurements in the region focussed on γ-ray spectroscopy of even-even nuclei (e.g. 252,254No, 250Fm), while more recently attention has switched to odd-mass nuclei such as 253No, 251Md and 255Lr, the latter being the heaviest nucleus so far studied…
Coexistence of triaxial and prolate shapes in 171Ir
1999
Abstract Excited states in 171Ir have been observed for the first time. Gamma-rays were assigned to the nucleus by the recoil-decay tagging method. The ground-state band has a structure consistent with an h 11 2 proton coupled to a core of large triaxial deformation. At high spins, a bandcrossing occurs which is interpreted as a change in shape to a prolate deformation. Band-mixing calculations are performed for 171–175Ir. These show that shape-coexistence between triaxial and prolate states in these nuclei follows the same systematics found in their Pt and Os neighbours. The systematics are also compared with deformations calculated for 171–179Ir using the code “Ultimate Cranker”. Dipole b…
Spectroscopy of the proton drip-line nucleus 203Fr
2013
The nucleus ${}^{203}$Fr has been studied through $\ensuremath{\gamma}$-ray and electron spectroscopy, using the recoil-decay tagging technique. A 13/2${}^{+}$ state, with a half-life of 0.37(5) $\ensuremath{\mu}$s, has been observed in ${}^{203}$Fr. Both the $\ensuremath{\alpha}$-decay branch and the internal de-excitation of the 1/2${}^{+}$ isomer in ${}^{203}$Fr have been studied. Furthermore, the corresponding 1/2${}^{+}$ state, with a half-life of 0.31(8) s, has been found in ${}^{199}$At. In addition, transitions feeding the 9/2${}^{\ensuremath{-}}$ ground state of ${}^{203}$Fr have been identified. The observed level pattern suggests that the ground state is still spherical.
Nuclear matter effects onJ/ψproduction in asymmetric Cu + Au collisions atsNN=200GeV
2014
We report on J/psi production from asymmetric Cu + Au heavy-ion collisions at root S-NN = 200 GeV at the Relativistic Heavy Ion Collider at both forward (Cu-going direction) and backward (Au-going direction) rapidities. The nuclear modification of J/psi yields in Cu + Au collisions in the Au-going direction is found to be comparable to that inAu + Au collisions when plotted as a function of the number of participating nucleons. In the Cu-going direction, J/psi production shows a stronger suppression. This difference is comparable in magnitude and has the same sign as the difference expected from shadowing effects due to stronger low-x gluon suppression in the larger Au nucleus.
Direct measurements of the lifetime of medium-heavy hypernuclei
2018
Abstract The lifetime of a Λ particle embedded in a nucleus (hypernucleus) decreases from that of free Λ decay mainly due to the opening of the Λ N → N N weak decay channel. However, it is generally believed that the lifetime of a hypernucleus attains a constant value (saturation) for medium to heavy hypernuclear masses, yet this hypothesis has been difficult to verify. This paper presents a direct measurement of the lifetime of medium-heavy hypernuclei that were hyper-fragments produced by fission or break-up from heavy hypernuclei initially produced with a 2.34 GeV photon-beam incident on thin Fe, Cu, Ag, and Bi target foils. For each event, fragments were detected in coincident pairs by …
Production of Θ+ hypernuclei with the (K+,π+) reaction
2005
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.