This work aims at presenting an alternative approach to the long standing problem of the B(E2) values in Sn isotopes in the vicinity of the N=Z double-magic nucleus 100Sn, until now predominantly ...measured with relativistic and intermediate-energy Coulomb excitation reactions. The direct measurement of the lifetime of low-lying excited states in odd-even Sn isotopes provides a new and precise guidance for the theoretical description of the nuclear structure in this region. Lifetime measurements have been performed in 105Sn for the first time with the coincidence Recoil Distance Doppler Shift technique. The lifetime results for the 7/21+ first excited state and the 11/21+ state, 2+(104Sn) ⊗ν1g7/2 multiplet member, are discussed in comparison with state-of-the-art shell model and mean field calculations, highlighting the crucial contribution of proton excitation across the core of 100Sn. The reduced transition probability B(E2) of the 11/21+ core-coupled state points out an enhanced staggering with respect to the B(E2; 21+→01+) in the even-mass 104Sn and 106Sn isotopes.
Quadrupole interaction involving protons and neutrons drives the nucleus into deformed configurations at low excitation energies. Intruder states appear in N=49 isotones, reaching a minimum at around ...500 keV in 83Se. Since 83Se is in the mid of the proton shell (Z=28-40), it is a good candidate to study the properties of particle-hole intruder states lowered in energy by large quadrupole correlations. Moreover, it will also allow one to estimate the degree of N=50 core breaking in the ground state of Se isotopes. The lifetime of the 540-keV 1/2+ state and 1100-keV 3/2+ state of 83Se were measured using the Recoil Distance Method and the Doppler Shift Attenuation Method respectively. A beam of 82Se, with intensity 0.02 pnA, accelerated to 270 MeV from the Tandem accelerator at LNL-INFN, was sent into a deuterated polyethylene foil (C2D4), evaporated on a 6 mg/cm2 gold layer. The GALILEO γ-array was coupled to the SPIDER silicon array, allowing one to obtain the needed channel selectivity through particle-γ coincidence measurements.
A search is presented in proton-proton collisions at radicals = 7 TeV for fermionic triplet states expected in type III seesaw models. The search is performed using final states with three isolated ...charged leptons and an imbalance in transverse momentum. The data, collected with the CMS detector at the LHC, correspond to an integrated luminosity of 4.9 fb super(?1). No excess of events is observed above the background predicted by the standard model, and the results are interpreted in terms of limits on production cross sections and masses of the heavy partners of the neutrinos in type III seesaw models. Depending on the considered scenarios, lower limits are obtained on the mass of the heavy partner of the neutrino that range from 180 to 210 GeV. These are the first limits on the production of type III seesaw fermionic triplet states reported by an experiment at the LHC.
The GALILEO γ-ray spectrometer has been constructed at the Legnaro National Laboratory of INFN (LNL-INFN). It can be coupled to advanced ancillary devices which allows nuclear structure studies ...employing the variety of in-beam γ-ray spectroscopy methods. Such studies benefit from reactions induced by the intense stable beams delivered by the Tandem-ALPI-PIAVE accelerator complex and by the radioactive beams which will be provided by the SPES facility. In this paper we outline two experiments performed within the experimental campaign at GALILEO coupled to the EUCLIDES Si-ball and the Neutron Wall array. The first one was aimed at spectroscopic studies in A=31 mirror nuclei and the second one at measurements of lifetimes of excited states in nuclei in the vicinity of 100Sn.
Abstract
Quadrupole interaction involving protons and neutrons drives the nucleus into deformed configurations at low excitation energies. Intruder states appear in N=49 isotones, reaching a minimum ...at around 500 keV in
83
Se. Since
83
Se is in the mid of the proton shell (Z=28-40), it is a good candidate to study the properties of particle-hole intruder states lowered in energy by large quadrupole correlations. Moreover, it will also allow one to estimate the degree of N=50 core breaking in the ground state of Se isotopes. The lifetime of the 540-keV 1/2
+
state and 1100-keV 3/2
+
state of
83
Se were measured using the Recoil Distance Method and the Doppler Shift Attenuation Method respectively. A beam of
82
Se, with intensity 0.02 pnA, accelerated to 270 MeV from the Tandem accelerator at LNL-INFN, was sent into a deuterated polyethylene foil (C
2
D
4
), evaporated on a 6 mg/cm
2
gold layer. The GALILEO γ-array was coupled to the SPIDER silicon array, allowing one to obtain the needed channel selectivity through particle-γ coincidence measurements.
A new dedicated plunger device for the GALILEO γ-ray detector array Müller-Gatermann, C.; von Spee, F.; Goasduff, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2019, Letnik:
920
Journal Article
Recenzirano
A new device, the GALILEO plunger, has been developed for lifetime measurement studies using the GALILEO γ-ray detector array at the Laboratori Nazionali di Legnaro (LNL) in Legnaro, Italy. This ...plunger device holds two stretched metal foils in the beam path for the use of the recoil distance Doppler-shift technique in order to measure lifetimes of nuclear excited states in the range of 1 ps to 1 ns. The compact design allows one to combine different auxiliary detectors with the plunger device inside the target chamber and takes care of high γ-ray transparency. The design and control of the device are presented in this paper, together with lifetimes of excited states in 180Pt measured within the first in-beam commissioning run.
The GALILEO γ-ray spectrometer, installed at the Laboratori Nazionali di Legnaro (LNL), benefits from intense stable beams provided by the Tandem-ALPI-PIAVE accelerator complex and from radioactive ...beams to be delivered in the near future by the SPES facility. The spectrometer is complemented with a variety of ancillary devices to allow for nuclear structure and reaction studies. The 4π Si-ball array EUCLIDES coupled to the GALILEO γ-ray spectrometer represents one of the commonly used setup for experiments aiming at spectroscopic studies. High-efficiency detection of light-charged particles in a fusion–evaporation reaction guarantees good discrimination of different reaction channels and provides essential information for the kinematic reconstruction. In this paper we discuss a configuration of the EUCLIDES array developed for the lifetime measurements of nuclear excited states populated in a fusion–evaporation reaction. In such a configuration a part of the EUCLIDES detectors is disassembled allowing for the installation of a plunger device in the reaction chamber. The reduced configuration of EUCLIDES provides high detection efficiency necessary for reliable light charged-particle discrimination. We report on the commissioning experiment focused on the 58Ni(58Ni,3p)113I reaction. The lifetimes of 11/2− and 15/2− states were measured by applying the Recoil Distance Doppler Shift method to be equal to 206(20) ps and 7.9(12) ps correspondingly and were in good agreement with the values cited in the literature. Thus, the combination of the GALILEO and EUCLIDES arrays, and the plunger device has resulted in a powerful experimental setup to determine lifetimes of excited states in neutron-deficient nuclei in the picosecond range.
Shape coexistence in the \(Z \approx 82\) region has been established in mercury, lead and polonium isotopes. Even-even mercury isotopes with \(100 \leq N \leq 106\) present multiple fingerprints of ...this phenomenon, which seems to be no longer present for \(N \geq 110\). According to a number of theoretical calculations, shape coexistence is predicted in the \(^{188}\)Hg isotope. The \(^{188}\)Hg nucleus was populated using two different fusion-evaporation reactions with two targets, \(^{158}\)Gd and \(^{160}\)Gd, and a beam of \(^{34}\)S, provided by the Tandem-ALPI accelerators complex at the Laboratori Nazionali di Legnaro. The channels of interest were selected using the information from the Neutron Wall array, while the \(\gamma\) rays were detected using the GALILEO \(\gamma\)-ray array. The lifetimes of the excited states were determined using the Recoil Distance Doppler-Shift method, employing the dedicated GALILEO plunger device. Using the two-bands mixing and rotational models, the deformation of the pure configurations was obtained from the experimental results. The extracted transition strengths were compared with those calculated with the state-of-the-art symmetry-conserving configuration-mixing (SCCM) and five-dimentional collective Hamiltonian (5DCH) approaches in order to shed light on the nature of the observed structures in the \(^{188}\)Hg nucleus. An oblate, a normal- and a super-deformed prolate bands were predicted and their underlying shell structure was also discussed.
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