549 research outputs found
Droplets formation inside a venturi liquid mixer
The formation of a coarse photographic emulsion by entraining a hot oil phase into a cooler aqueous phase by a Venturi device is considered. The main focus is on understanding the mechanism and site of droplet formation in the device, as well as the time-scale of heat flow, to see if it is feasible to feed this emulsion directly to a homogenizer in a continuous process
INTERIM REPORT ON THE USE OF SM-2 ELEMENTS IN SM-1, SM-1A AND PM-2A CORES
Interim results of analytical investigation of nuclear and thermal characteristics of SM-2 type fuel elements in SM-1, SM-lA, and PM-2Ae reactor cores are reported. Utilizing modified two-proup diffusion theory, predictions of power distribution and core and rod reactivity were performed. The calculations indicate that use of SM-2 fuel elemente in SM-1, SM-lA, and PM-2A is feasible from the nuclear standpoint. A steady state thermal analysis of each plant utilizing SM-2 elements was carried out. This analysis showed that the minimum departure from nuclear boiling ratios were considerably abovs the minimum value ftom the design criteria standpoint at both the operating and scram power levels. The investigation indicated that SM-2 elements can successfully be employed in SM-1, SM-lA, and PM-2A as replacement core elements. (auth
The Off-diagonal Goldberger-Treiman Relation and Its Discrepancy
We study the off-diagonal Goldberger-Treiman relation (ODGTR) and its
discrepancy (ODGTD) in the N, Delta, pi sector through O(p^2) using heavy
baryon chiral perturbation theory. To this order, the ODGTD and axial vector N
to Delta transition radius are determined solely by low energy constants. Loop
corrections appear at O(p^4). For low-energy constants of natural size, the
ODGTD would represent a ~ 2% correction to the ODGTR. We discuss the
implications of the ODGTR and ODGTD for lattice and quark model calculations of
the transition form factors and for parity-violating electroexcitation of the
Delta.Comment: 11 pages, 1 eps figur
Reaction and Axial Vector Coupling
The reaction is studied in the region of low
to investigate the effect of deuteron structure and width of the
resonance on the differential cross section. The results are used to extract
the axial vector coupling from the experimental data on
this reaction. The possibility to determine this coupling from electroweak
interaction experiments with high intensity electron accelerators is discussed.Comment: 14 pages, REVTEX, 5 figure
TeV scale resonant leptogenesis from supersymmetry breaking
We propose a model of TeV-scale resonant leptogenesis based upon recent
models of the generation of light neutrino masses from supersymmetry-breaking
effects with TeV-scale right-handed (rhd) neutrinos, . The model leads to
naturally large cosmological lepton asymmetries via the resonant behaviour of
the one-loop self-energy contribution to decay. Our model addresses the
primary problems of previous phenomenological studies of low-energy
leptogenesis: a rational for TeV-scale rhd neutrinos with small Yukawa
couplings so that the out-of equilibrium condition for decay is
satisfied; the origin of the tiny, but non-zero mass splitting required between
at least two masses; and the necessary non-trivial breaking of flavour
symmetries in the rhd neutrino sector. The low mass-scale of the rhd neutrinos
and their superpartners, and the TeV-scale -terms automatically contained
within the model offer opportunities for partial direct experimental tests of
this leptogenesis mechanism at future colliders.Comment: 10 Pages latex, version for JHE
Reconstructing the two right-handed neutrino model
In this paper we propose a low-energy parametrization of the two right-handed
neutrino model, and discuss the prospects to determine experimentally these
parameters in supersymmetric scenarios. In addition, we present exact formulas
to reconstruct the high-energy leptonic superpotential in terms of the
low-energy observables. We also discuss limits of the three right-handed
neutrino model where this procedure applies.Comment: 28 pages, 4 figures. Typos corrected, references adde
Future Directions in Parity Violation: From Quarks to the Cosmos
I discuss the prospects for future studies of parity-violating (PV)
interactions at low energies and the insights they might provide about open
questions in the Standard Model as well as physics that lies beyond it. I cover
four types of parity-violating observables: PV electron scattering; PV hadronic
interactions; PV correlations in weak decays; and searches for the permanent
electric dipole moments of quantum systems.Comment: Talk given at PAVI 06 workshop on parity-violating interactions,
Milos, Greece (May, 2006); 10 page
On the fraction of dark matter in charged massive particles (CHAMPs)
From various cosmological, astrophysical and terrestrial requirements, we
derive conservative upper bounds on the present-day fraction of the mass of the
Galactic dark matter (DM) halo in charged massive particles (CHAMPs). If dark
matter particles are neutral but decay lately into CHAMPs, the lack of
detection of heavy hydrogen in sea water and the vertical pressure equilibrium
in the Galactic disc turn out to put the most stringent bounds. Adopting very
conservative assumptions about the recoiling velocity of CHAMPs in the decay
and on the decay energy deposited in baryonic gas, we find that the lifetime
for decaying neutral DM must be > (0.9-3.4)x 10^3 Gyr. Even assuming the
gyroradii of CHAMPs in the Galactic magnetic field are too small for halo
CHAMPs to reach Earth, the present-day fraction of the mass of the Galactic
halo in CHAMPs should be < (0.4-1.4)x 10^{-2}. We show that redistributing the
DM through the coupling between CHAMPs and the ubiquitous magnetic fields
cannot be a solution to the cuspy halo problem in dwarf galaxies.Comment: 21 pages, 2 figures. To appear in JCA
Leptogenesis Bound on Spontaneous Symmetry Breaking of Global Lepton Number
We propose a new class of leptogenesis bounds on the spontaneous symmetry
breaking of global lepton number. These models have a generic feature of
inducing new lepton number violating interactions, due to the presence of the
Majorons. We analyzed the singlet Majoron model with right-handed neutrinos and
find that the lepton number should be broken above 10^5 GeV to realize a
successful leptogenesis because the annihilations of the right-handed neutrinos
into the massless Majorons and into the standard model Higgs should go out of
equilibrium before the sphaleron process is over. We then argue that this type
of leptogenesis constraint should exist in the singlet-triplet Majoron models
as well as in a class of R-parity violating supersymmetric Majoron models.Comment: 4 pages, 2 figure
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