8,307 research outputs found
Stop Decay with LSP Gravitino in the final state:
In MSSM scenarios where the gravitino is the lightest supersymmetric particle
(LSP), and therefore a viable dark matter candidate, the stop
could be the next-to-lightest superpartner (NLSP). For a mass spectrum
satisfying: ,
the stop decay is dominated by the 3-body mode . We calculate the stop life-time, including the full
contributions from top, sbottom and chargino as intermediate states. We also
evaluate the stop lifetime for the case when the gravitino can be approximated
by the goldstino state. Our analytical results are conveniently expressed using
an expansion in terms of the intermediate state mass, which helps to identify
the massless limit.
In the region of low gravitino mass ()
the results obtained using the gravitino and goldstino cases turns out to be
similar, as expected. However for higher gravitino masses the results for the lifetime could show a difference
of O(100)\%
Axial Transition Form Factors and Pion Decay of Baryon Resonances
The pion decay constants of the lowest orbitally excited states of the
nucleon and the along with the corresponding axial transition
form factors are calculated with Poincar\'e covariant constituent-quark models
with instant, point and front forms of relativistic kinematics. The model wave
functions are chosen such that the calculated electromagnetic and axial form
factors of the nucleon represent the empirical values in all three forms of
kinematics, when calculated with single-constituent currents. The pion decay
widths calculated with the three forms of kinematics are smaller than the
empirical values. Front and instant form kinematics provide a similar
description, with a slight preference for front form, while the point form
values are significantly smaller in the case of the lowest positive parity
resonances.Comment: 18 pages, 5 figures. Slightly revised, accepted in Phys. Rev.
Chaos in a Switched-Capacitor Circuit
We report chaotic phenomena observed from a simple nonlinear switched-capacitor circuit. The experimentally measured bifurcation tree diagram reveals a period-doubling route to chaos. This circuit is described by a first-order discrete equation which can be transformed into the logistic map whose chaotic dynamics is well known.National Science Foundation ECS-8542885Comisión Interministerial de Ciencia y Tecnología 0245/81Office of Naval Research under Contract NOOO14-76-C-057
ROCOV scheme for Fault Detection and Location in HVDC sytems
A reliable DC fault protection system is essential
for the development of HVDC grids. Therefore, this paper deals
with the voltage derivative ROCOV scheme to locate and detect
DC faults. The algorithm is able to differentiate internal and
external faults considerably fast. The proposed algorithm is
analyzed in a HVDC grid with different fault case scenarios.
Finally, the ROCOV protection thresholds are discussed.The authors thank the support from the Spanish Ministry of
Economy, Industry and Competitiveness (project
ENE2016-79145-R AEI/FEDER, UE) and GISEL research
group IT1083-16), as well as from the University of the
Basque Country UPV/EHU (research group funding
PPG17/23)
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