122665147
De Sitter vacua and inflation in no-scale string models
This thesis studies the question of how de Sitter vacua and slow-roll inflation may be realized in string-motivated models. More specifically, we consider 4d N = 1 supergravity theories (without vector multiplets) with Kahler potentials which are ‘no-scale’ at leading order. Such theories frequently arise in the moduli sector of string compactifications. We discuss a condition on the scalar geometry (defined by the Kahler potential) and on the direction of supersymmetry breaking in the scalar manifold, which has to be met in order for the average of the masses of the sGoldstinos to be positive, and hence for metastable vacua to be possible. This condition also turns out to be necessary for the existence of trajectories admitting slow-roll inflation. Its implications for certain scalar manifolds which arise from Calabi-Yau string compactifications are discussed. In particular, for two-moduli models arising from compactifications of heteroticand type IIB string theory, a simple criterion on the intersection numbers needs to be satisfied for possible de Sitter phases to exist. In addition, we show that subleading corrections breaking the no-scale property may allow the condition on the scalar geometry to be fulfilled, even when it is violated at leading order. Finally, we develop a procedure to construct superpotentials for a given viable Kahler potential, such that the scalar potential has a realistic local minimum. We propose two-moduli models, with superpotentials which could arise from flux backgrounds and non-perturbative effects, which have a viable vacuum without employing subleading corrections or an uplifting sector.
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.
115171499
\theta^PMNS_13 = \theta_C / \sqrt2 from GUTs
Abstract The recent observations of the leptonic mixing angle θ 13 PMNS are consistent with θ 13 PMNS = θ C / 2 (with θ C being the Cabibbo angle θ 12 CKM ). We discuss how this relation can emerge in Grand Unified Theories (GUTs) via charged lepton corrections. The key ingredient is that in GUTs the down-type quark Yukawa matrix and the charged lepton Yukawa matrix are generated from the same set of GUT operators, which implies that the resulting entries are linked and differ only by group-theoretical Clebsch factors. This allows a link θ 12 e ≈ θ C to be established, which can induce θ 13 PMNS ≈ θ C / 2 provided that the 1–3 mixing in the neutrino mass matrix is much smaller than θ C . We find simple conditions under which θ 13 PMNS ≈ θ C / 2 can arise via this link in SU(5) GUTs and Pati–Salam models. We also discuss possible corrections to the exact relation. Using lepton mixing sum rules different neutrino mixing patterns can be distinguished by their predictions for the Dirac CP phase δ PMNS .
121826170
Test of calculations with single-particle density dependent pairing inTe132
R. O. Hughes, N. V. Zamfir, R. F. Casten, D. C. Radford, C. J. Barton, C. Baktash, M. A. Caprio, A. Galindo-Uribarri, C. J. Gross, P. A. Hausladen, E. A. McCutchan, J. J. Ressler, D. Shapira, D. W. Stracener, and C.-H. Yu Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124, USA Department of Physics, University of Surrey, Guildford GU 2 7XH, United Kingdom Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA University of York, Heslington YO10 5DD, United Kingdom Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520-8120, USA (Received 29 January 2004; published 25 May 2004)
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.
118100450
High spin states in Sr78
$^{78}\mathrm{Sr}$ was produced in the reaction $^{58}\mathrm{Ni}$${(}^{24}$Mg, 2p2n) with a relative cross section of less than 2.5% of the total fusion cross section at 110 MeV, but high spin states up to 16\ensuremath{\Elzxh} were firmly identified. Fifteen neutron detectors and fifteen Compton suppressed Ge detectors were used in a large solid angle arrangement. 2n\ensuremath{\gamma}\ensuremath{\gamma} and n\ensuremath{\gamma}\ensuremath{\gamma} coincidences were recorded. A small irregularity in the dynamic moment of inertia ${J}^{(2)}$/${\ensuremath{\Elzxh}}^{2}$ is evidence for a strongly mixed band crossing at \ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\approxeq}0.55 MeV in agreement with what is observed in $^{80}$,82Sr.
122193418
Time delays in heavy-ion-induced fission of medium- Z nuclei, measured by crystal blocking
Time delays in fission induced by bombardment of Mo with 170- and 180-MeV {sup 32}S, 225- and 240-MeV {sup 48}Ti, and 300-MeV {sup 58}Ni have been measured by observation of crystal blocking of fission fragments. In contrast to earlier measurements with a W target, the results are consistent with fission of a compound nucleus in competition with mainly neutron emission. Most of the fissions happen on a time scale much shorter than attoseconds but there is a significant component of fission with much longer lifetimes. The measurements are reproduced with a standard statistical model, including a Kramers correction to fission widths from the viscosity of hot nuclear matter. These new results support the interpretation of our earlier measurements with a W target, which indicate that there is a transition in heavy-ion-induced fission at large atomic number and mass, from multichance fission in the standard Bohr-Wheeler picture to fission without formation of a compound nucleus. The process is slowed down by nuclear viscosity, with measured delays of order attoseconds.
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)