874 research outputs found
Formation of light exotic nuclei in low-energy multinucleon transfer reactions
Low-energy multinucleon transfer reactions are shown to be very effective
tool for the production and spectroscopic study of light exotic nuclei. The
corresponding cross sections are found to be significantly larger as compared
with high energy fragmentation reactions. Several optimal reactions for the
production of extremely neutron rich isotopes of elements with Z=6-14 are
proposed.Comment: 8 figure
Standard model with compactified spatial dimensions
We analyze the structure of the standard model coupled to gravity with
spatial dimensions compactified on a three-torus. We find that there are no
stable one-dimensional vacua at zero temperature, although there does exist an
unstable vacuum for a particular set of Dirac neutrino masses.Comment: 7 pages, 2 figures; v2: published in JHE
Simplified models with baryon number violation but no proton decay
We enumerate the simplest models that have baryon number violation at the classical level but do not give rise to proton decay. These models have scalar fields in two representations of SU(3)ĂSU(2)ĂU(1) and violate baryon number by two units. Some of the models give rise to nnĚ
(neutron-antineutron) oscillations, while some also violate lepton number by two units. We discuss the range of scalar masses for which nnĚ
oscillations are measurable in the next generation of experiments. We give a brief overview of the phenomenology of these models and then focus on one of them for a more quantitative discussion of nnĚ
oscillations, the generation of the cosmological baryon number, the electric dipole moment of the neutron, and K^0-KĚ
^0 mixing
Phenomenology of scalar leptoquarks
We study the simplest renormalizable scalar leptoquark models where the standard model is augmented only by one additional scalar representation of SU(3)ĂSU(2)ĂU(1). The requirement that there be no proton decay from renormalizable interactions singles out two such models, one of which exhibits an unusual top mass enhancement of the ÎźâeÎł decay rate. We analyze the phenomenology of the model with the unusual top mass enhancement of loop level chirality changing charged lepton processes in the light of existing and upcoming experiments. Both of the models that do not allow proton decay from renormalizable interactions have dimension-5 operators that, even if suppressed by the Planck scale, can give rise to an unacceptably high level of baryon number violation. We discuss symmetries that can forbid these dimension-5 operators
Particle creation in a toroidal universe
We calculate the particle production rate in an expanding universe with a
three-torus topology. We discuss also the complete evolution of the size of
such a universe. The energy density of particles created through the nonzero
modes is computed for selected masses. The unique contribution of the zero mode
and its properties are also analyzed.Comment: 9 pages, 11 figure
Core excitations across the neutron shell gap in ²â°âˇTl
The single closed-neutron-shell, one proton-hole nucleus 207Tl was populated in deep-inelastic collisions of a 208Pb beam with a 208Pb target. The yrast and near-yrast level scheme has been established up to high excitation energy, comprising an octupol
Nature of yrast excitations near N=40: Level structure of Ni-67
Excited states in Ni-67 were populated in deep-inelastic reactions of a Ni-64
beam at 430 MeV on a thick U-238 target. A level scheme built on the previously
known 13 micro-s isomer has been delineated up to an excitation energy of ~5.3
MeV and a tentative spin and parity of (21/2-). Shell model calculations have
been carried out using two effective interactions in the f5/2pg9/2 model space
with a Ni-56 core. Satisfactory agreement between experiment and theory is
achieved for the measured transition energies and branching ratios. The
calculations indicate that the yrast states are associated with rather complex
configurations, herewith demonstrating the relative weakness of the N=40
subshell gap and the importance of multi particle-hole excitations involving
the g9/2 neutron orbital.Comment: Accepted by Physical Review
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