19,983 research outputs found
Neutral heavy lepton production at next high energy linear colliders
The discovery potential for detecting new heavy Majorana and Dirac neutrinos
at some recently proposed high energy colliders is discussed. These
new particles are suggested by grand unified theories and superstring-inspired
models. For these models the production of a single heavy neutrino is shown to
be more relevant than pair production when comparing cross sections and
neutrino mass ranges.
The process is calculated
including on-shell and off-shell heavy neutrino effects.
We present a detailed study of cross sections and distributions that shows a
clear separation between the signal and standard model contributions, even
after including hadronization effects.Comment: 4 pages including 15 figures, 1 table. RevTex. Accepted in Physical
Review
Gauge fields in a string-cigar braneworld
In this work we investigate the properties of an Abelian gauge vector field
in a thin and in a smoothed string-like braneworld, the so-called string-cigar
model. This thick brane scenario satisfies the regularity conditions and it can
be regarded as an interior and exterior string-like solution. The source
undergoes a geometric Ricci flow which is connected to a variation of the bulk
cosmological constant. The Ricci flow changes the width and amplitude of the
massless mode at the brane core and recover the usual thin string-like behavior
at large distances. By numerical means we obtain the Kaluza-Klein (KK) spectrum
for both the thin brane and the string-cigar. It turns out that both models
exhibit a mass gap between the massless and the massive modes and between the
high and the low mass regimes. The KK modes are smooth near the brane and their
amplitude are enhanced by the string-cigar core. The analogue Schr\"odinger
potential is also tuned by the geometric flow.Comment: The discussion about the Kaluza-Klein spectrum of the gauge field was
improved. Numerical analysis was adapted to the conventional notation on
Kaluza-Klein number. Some graphics were modified for considering other
notation. Results unchanged. References added. Corrected typos. 17 pages. 6
figures. To match version to appears in Physics Letters
Decoherence of tripartite states - a trapped ion coupled to an optical cavity
We investigate the non-dissipative decoherence of three qubit system obtained
by manipulating the state of a trapped two-level ion coupled to an optical
cavity. Modelling the environment as a set of noninteracting harmonic
oscillators, analytical expressions for the state operator of tripartite
composite system, the probability of generating maximally entangled GHZ state,
and the population inversion have been obtained. The pointer observable is the
energy of the isolated quantum system. Coupling to environment results in
exponential decay of off diagonal matrix elements of the state operator with
time as well as a phase decoherence of the component states.
Numerical calculations to examine the time evolution of GHZ state generation
probability and population inversion for different system environment coupling
strengths are performed. Using negativity as an entanglement measure and linear
entropy as a measure of mixedness, the entanglement dynamics of the tripartite
system in the presence of decoherence is analysed.Comment: Revised version, errors corrected and references added. 12 pages, 6
figures, Presented at ICSSUR May 2005, Besancon, Franc
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