123674609
Band Structure in 79Y and the Question of T=0 Pairing
Excited states in the N = Z+1 nucleus Y-79 Were identified using the reaction Si-28(Fe-54, p2n)Y-79 at a 200 MeV beam energy and an experimental set up consisting of an array of Ge detectors and the Recoil Mass Spectrometer at Oak Ridge National Laboratory. With the help of additional gamma-gamma coincidence data obtained with Gammasphere, these gamma-rays were found to form a strongly-coupled rotational band with rigid-rotor-like behavior. Results of conventional Nilsson-Strutinsky cranked shell model calculations, which predict a deformation of beta(2)similar to 0.4, are in excellent agreement with the properties of this band. Similar calculations for the neighboring N = Z and N = Z + 1 nuclei are also in good agreement with experimental data. This suggests that the presence of the putative T = 0 neutron-proton pairing does not significantly affect such simple observables as the moments of inertia of these bands at low spins. (Less)
122667645
First Observation of the Drip Line Nucleus 140Dy: Identification of a 7 Mu s K-isomer Populating the Ground State Band
A new $7 \ensuremath{\mu}\mathrm{s}$ isomer in the drip line nucleus ${}^{140}\mathrm{Dy}$ was selected from the products of the ${}^{54}\mathrm{Fe}$ $(315 \mathrm{MeV}{)+}^{92}\mathrm{Mo}$ reaction by a recoil mass spectrometer and studied with recoil-delayed $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidences. Five cascading $\ensuremath{\gamma}$ transitions were interpreted as the decay of an ${I}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ ${\ensuremath{\nu}{9/2}^{\ensuremath{-}}[514]\ensuremath{\bigotimes}\ensuremath{\nu}{7/2}^{+}[404]}$ K isomer $({T}_{1/2}=7.0(5) \ensuremath{\mu}\mathrm{s})$ via the ground-state band. The probability of proton emission from ${}^{141}\mathrm{Ho}$ to the ${0}^{+}$ ground state and to the ${2}^{+}$ excited state in ${}^{140}\mathrm{Dy}$ is discussed.
120523530
Neutron Single Particle Strengths from the (d,p) Reaction on 18F
The 19F nucleus has been studied extensively. However, there have been no comprehensive experimental studies of 18F+n single-particle components in 19F, and no measure of neutron vacancies in the 18F ground state, as such experiments require a (radioactive) 18F target or beam. We have used the 2H(18F,p)19F reaction to selectively populate states in 19F that are of 18F+n character. The 108.5-MeV radioactive 18F+9 beam was provided by the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Proton-recoil coincidence data were taken for both -decaying and particle-stable final states. Angular distributions and spectroscopic factors were measured for nine proton groups, corresponding to 13 states in 19F. The results are compared to shell model calculations.
3838065
Spectroscopy of element 115 decay chains.
A high-resolution α, x-ray, and γ-ray coincidence spectroscopy experiment was conducted at the GSI Helmholtzzentrum für Schwerionenforschung. Thirty correlated α-decay chains were detected following the fusion-evaporation reaction 48Ca + 243Am. The observations are consistent with previous assignments of similar decay chains to originate from element Z=115. For the first time, precise spectroscopy allows the derivation of excitation schemes of isotopes along the decay chains starting with elements Z>112. Comprehensive Monte Carlo simulations accompany the data analysis. Nuclear structure models provide a first level interpretation.
124889976
β -decay study of neutron-rich bromine and krypton isotopes
Short lived neutron rich nuclei including 93 Br, 93 Kr and 94 Kr were produced in proton induced fission of 238 U at the HRIBF in Oak Ridge. Their beta decay was studied by means of a high resolution on line mass separator and beta gamma spectroscopy methods. The half life of 93Br T1/2 = 152(8) ms and delayed branching ratio of Pn = 53-8+11 may be compared to the previously reported values of T1/2 = 102(10) ms and Pn = 68(7)%. At the same time the half life of 94Kr T1/2 = 227(14) ms and B delayed branching ratio of Pn = 1.9+0.6 0.2 % of 93Kr are in very good agreement with literature values. The decay properties of 93Br include four new gamma transitions following beta delayed neutron emission.
121184959
Search for inverse fission of uranium
There is a long-term interest in running the fission reaction backward, i.e., studying the 'inverse fission' of uranium. The recent availability of beams of n-rich fission fragments has stimulated interest in this endeavor. The purpose is to search for inverse fission in the reactions {sup 124,132}Sn + {sup 100}Mo. In the {sup 124}Sn + {sup 100}Mo reaction, evaporation residues were searched for using in-beam detection of evaporation residues, in-beam {alpha} spectroscopy, and post-irradiation {alpha} spectroscopy, while in the {sup 132}Sn + {sup 100}Mo reaction, the evaporation residue {sup 230}U was searched for using post-irradiation {alpha} spectroscopy. No evidence for the occurrence of the inverse fission reactions was found. The upper-limit cross section for the latter reaction is {approx}550 {mu}b, while the experimental upper-limit cross section for the former reaction is about 21{sup -21}{sup +38} nb. The intensity of suitable radioactive beams is not high enough at present to detect inverse fission. For the {sup 124}Sn + {sup 100}Mo reaction, the observed upper limits are below the estimates of current models for these reactions, probably due to fusion hindrance.
4356427
The ‘Higgs’ amplitude mode at the two-dimensional superfluid/Mott insulator transition
Spontaneous symmetry breaking plays a key role in our understanding of nature. In relativistic quantum field theory, a broken continuous symmetry leads to the emergence of two types of fundamental excitation: massless Nambu–Goldstone modes and a massive ‘Higgs’ amplitude mode. An excitation of Higgs type is of crucial importance in the standard model of elementary particle physics, and also appears as a fundamental collective mode in quantum many-body systems. Whether such a mode exists in low-dimensional systems as a resonance-like feature, or whether it becomes overdamped through coupling to Nambu–Goldstone modes, has been a subject of debate. Here we experimentally find and study a Higgs mode in a two-dimensional neutral superfluid close to a quantum phase transition to a Mott insulating phase. We unambiguously identify the mode by observing the expected reduction in frequency of the onset of spectral response when approaching the transition point. In this regime, our system is described by an effective relativistic field theory with a two-component quantum field, which constitutes a minimal model for spontaneous breaking of a continuous symmetry. Additionally, all microscopic parameters of our system are known from first principles and the resolution of our measurement allows us to detect excited states of the many-body system at the level of individual quasiparticles. This allows for an in-depth study of Higgs excitations that also addresses the consequences of the reduced dimensionality and confinement of the system. Our work constitutes a step towards exploring emergent relativistic models with ultracold atomic gases.
15114914
De Sitter vacua in no-scale supergravities and Calabi-Yau string models
We perform a general analysis on the possibility of obtaining metastable vacua with spontaneously broken N = 1 supersymmetry and non-negative cosmological constant in the moduli sector of string models. More specifically, we study the condition under which the scalar partners of the Goldstino are non-tachyonic, which depends only on the Kahler potential. This condition is not only necessary but also sufficient, in the sense that all of the other scalar fields can be given arbitrarily large positive square masses if the superpotential is suitably tuned. We consider both heterotic and orientifold string compactifications in the large-volume limit and show that the no-scale property shared by these models severely restricts the allowed values for the 'sGoldstino' masses in the superpotential parameter space. We find that a positive mass term may be achieved only for certain types of compactifications and specific Goldstino directions. Additionally, we show how subleading corrections to the Kahler potential which break the no-scale property may allow to lift these masses.
118472215
Hybrid anomaly-gravity mediation with flavor
We study models with contributions of similar size to the soft masses from anomaly-and gravity mediation, thereby curing the tachyonic slepton problem of anomaly mediation. A possible origin of this hybrid setup in a 5-dimensional brane world is briefly discussed. The absence of excessive flavor violation is explained by alignment. The gravitino can be heavy enough so that the gravitino problem of supersymmetric theories with leptogenesis is avoided. The model has a characteristic signature: It predicts the distinctive gaugino mass pattern of anomaly mediation and, at the same time, (1) slepton mass splittings.
8572469
Constructing de Sitter vacua in no-scale string models without uplifting
We develop a method for constructing metastable de Sitter vacua in N = 1 supergravity models describing the no-scale volume moduli sector of Calabi-Yau string compactifications. We consider both heterotic and orientifold models. Our main guideline is the necessary condition for the existence of metastable vacua coming from the Goldstino multiplet, which constrains the allowed scalar geometries and supersymmetry-breaking directions. In the simplest non-trivial case where the volume is controlled by two moduli, this condition simplifies and turns out to be fully characterised by the intersection numbers of the Calabi-Yau manifold. We analyse this case in detail and show that once the metastability condition is satisfied it is possible to reconstruct in a systematic way the local form of the superpotential that is needed to stabilise all the fields. We apply then this procedure to construct some examples of models where the superpotential takes a realistic form allowed by flux backgrounds and gaugino condensation effects, for which a viable vacuum arises without the need of invoking corrections to the Kahler potential breaking the no-scale property or uplifting terms. We finally discuss the prospects of constructing potentially realistic models along these lines.
16376745
Einstein-Podolsky-Rosen correlations of ultracold atomic gases.
We demonstrate that collective continuous variables of two species of trapped ultracold bosonic gases can be Einstein-Podolsky-Rosen-correlated (entangled) via inherent interactions between the species. We propose two different schemes for creating these correlations--a dynamical scheme and a static scheme analogous to two-mode squeezing in quantum optics. We quantify the correlations by using known measures of entanglement and study the effect of finite temperature on these quantum correlations.