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.
26764553
Shape coexistence effects and quasiparticle alignment in 81Sr.
High spin states in /sup 81/Sr were investigated in the reactions /sup 56/Fe(/sup 28/Si,2pn) at 103.6 MeV and /sup 55/Mn(/sup 29/Si,p2n) at 95.2 MeV using the techniques of in-beam ..gamma..-ray spectroscopy. Measurements were made of ..gamma..-..gamma.. coincidences and ..gamma..-ray directional correlations from oriented nuclei. The lifetimes of 12 states and lifetime limits of 10 others were determined with the Doppler shift attenuation method. The data have been analyzed in terms of the Woods-Saxon cranking model. The first crossing observed in the yrast band is attributed to the alignment of a pair of g/sub 9/2/ protons. The irregularities observed in the J/sup (2)/ moment of inertia in the K/sup ..pi../ = (5/2/sup -/ and 1/2/sup (+)/ bands are interpreted as evidence for the alignment of a g/sub 9/2/ proton pair as well. The coexistence of prolate and oblate configurations at low spin is discussed in terms of the polarization of the soft even-even core by the odd neutron.
42734915
Identification of T=0 and T=1 bands in the N=Z=37 nucleus 74Rb.
The {gamma} decay of excited states in the {ital N}={ital Z} odd-odd nucleus {sup 74}Rb has been observed for the first time. The reaction {sup 40}Ca({sup 40}Ca,{alpha}{ital pn}){sup 74}Rb at 128 MeV beam energy was used. The ground state rotational band can be interpreted as being formed from the {ital T}=1 isobaric analog states of {sup 74}Kr with pairing correlations based on {ital T}=1, {ital M}{sub {ital T}}=0 neutron-proton pairs. At higher rotational frequency, a {ital T}=0 rotational band becomes energetically favored over the {ital T}=1 ground state band, in agreement with the predictions of cranked shell model calculations which explicitly include {ital T}=0 and {ital T}=1pairs. {copyright} {ital 1996 The American Physical Society.}
122384124
Lifetime Measurements of Normally Deformed and Superdeformed States in 82Sr
Lifetimes of a superdeformed band in Sr-82 were measured with the centroid shift method. The measured average quadrupole moment of this band corresponds to a quadrupole deformation of beta(2) approximate to 0.49, which is slightly smaller than both the theoretical prediction, and the measured deformation of the SD band in the neighboring isotone Zr-84. Lifetimes of high spin states of three normally deformed rotational bands in Sr-82 were also measured with the Doppler shift attenuation method technique. The quadrupole moments of these normally deformed bands show a decrease at the highest spins, supporting the predicted band terminations.
121608484
Identification of Excited States in 61Ga: Mirror Nuclei in the Upper fp Shell
In the fusion-evaporation reaction Ca-40+Mg-24 at 104 MeV beam energy, excited states have been observed for the first time in the isotope Ga-31(61)30. The experimental setup comprised the Ge array CLARION, a recoil mass spectrometer and, in its focal plane, an ionization chamber. Five transitions in Ga-61 are identified, out of which a cascade of three transitions has been established by means of recoil-gammagamma coincidences. The strong transitions at 271 keV in Ga-61 and 124 keV in Zn-61 are viewed as the "mirror" 5/2(-)-->3/2(-) ground-state transitions. The rather large energy difference of 150 keV is suggested to arise from Coulomb monopole contributions. Shell-model calculations support this interpretation.
122115035
Deformation driving intruder orbitals in Kr-77
High-spin states in Kr-77 were identified via analysis of prompt gamma-gamma coincidences in the Ni-58(Si-29,2 alpha 2p) reaction at 128 MeV at the Gammasphere facility. Evaporation channel selecti ...
119272291
Flavorful hybrid anomaly-gravity mediation
We consider supersymmetric models where anomaly and gravity mediation give comparable contributions to the soft terms and discuss how this can be realized in a five-dimensional brane world. The gaugino mass pattern of anomaly mediation is preserved in such a hybrid setup. The flavorful gravity-mediated contribution cures the tachyonic slepton problem of anomaly mediation. The supersymmetric flavor puzzle is solved by alignment. We explicitly show how a working flavor-tachyon link can be realized with Abelian flavor symmetries and give the characteristic signatures of the framework, including O(1) slepton mass splittings between different generations and between doublets and singlets. This provides opportunities for same flavor dilepton edge measurements with missing energy at the Large Hadron Collider (LHC). Rare lepton decay rates could be close to their current experimental limit. Compared to pure gravity mediation, the hybrid model is advantageous because it features a heavy gravitino which can avoid the cosmological gravitino problem of gravity-mediated models combined with leptogenesis.
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.
15184738
Constraints on modular inflation in supergravity and string theory
We perform a general algebraic analysis on the possibility of realising slow-roll inflation in the moduli sector of string models. This problem turns out to be very closely related to the characterisation of models admitting metastable vacua with non-negative cosmological constant. In fact, we show that the condition for the existence of viable inflationary trajectories is a deformation of the condition for the existence of metastable de Sitter vacua. This condition depends on the ratio between the scale of inflation and the gravitino mass and becomes stronger as this parameter grows. After performing a general study within arbitrary supergravity models, we analyse the implications of our results in several examples. More concretely, in the case of heterotic and orientifold string compactifications on a Calabi-Yau in the large volume limit we show that there may exist fully viable models, allowing both for inflation and stabilisation. Additionally, we show that subleading corrections breaking the no-scale property shared by these models always allow for slow-roll inflation but with an inflationary scale suppressed with respect to the gravitino scale. A scale of inflation larger than the gravitino scale can also be achieved under more restrictive circumstances and only for certain types of compactifications.
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.
119253199
Inverse neutrino mass hierarchy in a flavour GUT model
Abstract We construct a supersymmetric SU ( 5 ) × A 4 flavour GUT model in which an inverse neutrino mass hierarchy is realised without fine-tuning of parameters. The model shares some properties with the normal hierarchy model which we presented in arXiv:1305.6612 – in particular the relation θ 13 PMNS ≃ θ C / 2 . Besides these shared features, there are also important differences, mainly due to the different neutrino sector. These differences not only change the predictions in the lepton sector, but also in the quark sector, and will allow to discriminate between the two models using the results of present and future experiments. From a Markov Chain Monte Carlo fit we find that the inverse hierarchy model is in excellent agreement with the present experimental data.