Search NASA⌕ Search

SEARCH · Search NASA

Results for “UNITARITY”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Hadron cross sections at ultra high energies and unitarity bounds on diffraction dissociation

It was shown that if unitarity bounds on diffractive cross sections are valid at ultra high energies then diffractive dominance models which ascribe the increase in total hadron-hadron cross sections to diffractive processes only are ruled out. Calculations also show that cosmic ray cross sections derived from air shower experiments at ultra high energies clearly rule out models for hadron-hadron cross sections with nat.log ns energy dependence and favor those with nat.log n(2)s variation.

Yodh, G. B.↗
NASA NTRS1989

Unitarity limits on the mass and radius of dark matter particles

Using partial wave unitarity and the observed density of the Universe, it is show that a stable elementary particle which was once in thermal equilibrium cannot have a mass greater than 340 TeV. An extended object which was once in thermal equilibrium cannot have a radius less than 7.5 x 10(exp -7) fm. A lower limit to the relic abundance of such particles is also found.

Griest, Kim↗
NASA NTRS1990

Unitarity limits on the mass and radius of dark-matter particles

Using partial wave unitarity and the observed density of the Universe, it is shown that a stable elementary particle which was once in thermal equilibrium cannot have a mass greater than 340 TeV. An extended object which was once in thermal equlibrium cannot have a radius less than 7.5 x 10(exp -7) fm. A lower limit to the relic abundance of such particles is also found.

Griest, Kim↗
NASA NTRS1972

Excitation of Mg/+/ by electron collisions.

Demonstration that the Mg II resonance doublet at 2800 A represents a suitable diagnostic tool for the study of physical conditions in the solar chromosphere. The interpretation of intensities and line profiles requires the knowledge of all electron collision cross sections, which can affect directly or indirectly the population of upper levels of the doublet. For this purpose collision cross sections for transitions between levels 3s, 4s, 5s, 6s, 3p, 4p, 5p, 3d, 4d, and 5d have been calculated in the unitarized Coulomb-Born approximation without exchange. For the 3s-3p and 3s-3d transitions the present results are in a good agreement with the close-coupling calculations of Burke and Moores (1968).

Blaha, M.↗
NASA NTRS1975

Upper bound on neutrino cross sections

Asymptotic bounds on the total cross sections of neutrino (weak) scattering processes are obtained. It is shown that the elastic neutrino-neutrino cross section obeys the following bound in the high energy region: sigma sub T (S) equals ImF(S,0)/S is less than or equal to const. (LogS) squared. Assumptions of analyticity, crossing, unitarity, polynomial boundaries, and a zero-condition on the absorptive part of the scattering amplitude, are used to obtain this bound.

Mickens, R. E.↗
NASA NTRS2016

Heavy Right-Handed Neutrino Dark Matter and PeV Neutrinos at IceCube

We discuss a simple non-supersymmetric model based on the electroweak gauge group SU(2) (sub L) times SU(2) prime times U(1) (Sub B-L) where the lightest of the right-handed neutrinos, which are part of the leptonic doublet of SU(2) prime, play the role of a long-lived unstable dark matter with mass in the multi-Peta-electronvolt range. We use a resonant s-channel annihilation to obtain the correct thermal relic density and relax the unitarity bound on dark matter mass. In this model, there exists a 3-body dark matter decay mode producing tau leptons and neutrinos, which could be the source for the Peta-electronvolt cascade events observed in the IceCube experiment. The model can be tested with more precise flavor information of the highest-energy neutrino events in future data.

Bhupal Dev, P. S.↗
NASA NTRS2019

Simulation of Non-Markovian Dynamics on IBM QX

Currently available quantum computers allow us to run proof of principle algorithms that are unitary in their nature. Therefore, this architecture is unoptimized for simulation of an open quantum system. Here we present a method that helps us to overcome unitarity. We show how to run a non-Markovian evolution of a qubit system. We discuss all the discrepancies from theoretical predictions.

Wudarski, Filip A.↗