30,670 research outputs found
Space-charge compensation experiments at IOTA ring
Space-charge effects belong to the category of the most long-standing issues
in beam physics, and even today, after several decades of very active
exploration and development of counter-measures, they still pose the most
profound limitations on performance of high intensity proton accelerators. We
briefly consider past experience in active compensation of these effects and
present in detail the progress towards experimental studies of novel schemes of
space-charge compensation at the Fermilab's IOTA ring.Comment: 5 p
Detecting the Higgs Bosons of Minimal Supergravity with Muon Pairs
The prospects at the CERN LHC are investigated for the discovery via decays
into muon pairs of neutral Higgs bosons in the minimal supergravity model.
Promising results are found for the CP-odd pseudoscalar () and the heavier
CP-even scalar () Higgs bosons at large . For
\tan\beta \agt 10 and 100 GeV \alt m_A,m_H \alt 550 GeV, the and the
masses could be precisely reconstructed from the dimuon invariant mass.Comment: 12 pages, REVTEX, 4 figure
Scattering of Bunched Fractionally Charged Quasiparticles
The charge of fractionally charged quasiparticles, proposed by Laughlin to
explain the fractional quantum Hall effect (FQHE), was recently verified by
measurements. Charge q=e/3 and e/5 (e is the electron charge), at filling
factors nu=1/3 and 2/5, respectively, were measured. Here we report the
unexpected bunching of fractional charges, induced by an extremely weak
backscattering potential at exceptionally low electron temperatures (T<10 mK) -
deduced from shot noise measurements. Backscattered charges q=nu e,
specifically, q=e/3, q=2e/5, and q<3e/7, in the respective filling factors,
were measured. For the same settings but at an only slightly higher electron
temperature, the measured backscattered charges were q=e/3, q=e/5, and q=e/7.
In other words, bunching of backscattered quasiparticles is taking place at
sufficiently low temperatures. Moreover, the backscattered current exhibited
distinct temperature dependence that was correlated to the backscattered charge
and the filling factor. This observation suggests the existence of 'low' and
'high' temperature backscattering states, each with its characteristic charge
and characteristic energy.Comment: 4 pages, 3 figure
Nonequilibrium noise correlations in a point contact of helical edge states
We investigate theoretically the nonequilibrium finite-frequency current
noise in a four-terminal quantum point contact of interacting helical edge
states at a finite bias voltage. Special focus is put on the effects of the
single-particle and two-particle scattering between the two helical edge states
on the fractional charge quasiparticle excitations shown in the nonequilibrium
current noise spectra. Via the Keldysh perturbative approach, we find that the
effects of the single-particle and the two-particle scattering processes on the
current noise depend sensitively on the Luttinger liquid parameter. Moreover,
the Fano factors for the auto- and cross correlations of the currents in the
terminals are distinct from the ones for tunneling between the chiral edge
states in the quantum Hall liquid. The current noise spectra in the
single-particle-scattering-dominated and the two-particle-scattering-dominated
regime are shown. Experimental implications of our results on the transport
through the helical edges in two-dimensional topological insulators are
discussed.Comment: 10 pages, 8 figure
A State-Space Estimation of the Lee-Carter Mortality Model and Implications for Annuity Pricing
In this article we investigate a state-space representation of the Lee-Carter
model which is a benchmark stochastic mortality model for forecasting
age-specific death rates. Existing relevant literature focuses mainly on
mortality forecasting or pricing of longevity derivatives, while the full
implications and methods of using the state-space representation of the
Lee-Carter model in pricing retirement income products is yet to be examined.
The main contribution of this article is twofold. First, we provide a rigorous
and detailed derivation of the posterior distributions of the parameters and
the latent process of the Lee-Carter model via Gibbs sampling. Our assumption
for priors is slightly more general than the current literature in this area.
Moreover, we suggest a new form of identification constraint not yet utilised
in the actuarial literature that proves to be a more convenient approach for
estimating the model under the state-space framework. Second, by exploiting the
posterior distribution of the latent process and parameters, we examine the
pricing range of annuities, taking into account the stochastic nature of the
dynamics of the mortality rates. In this way we aim to capture the impact of
longevity risk on the pricing of annuities. The outcome of our study
demonstrates that an annuity price can be more than 4% under-valued when
different assumptions are made on determining the survival curve constructed
from the distribution of the forecasted death rates. Given that a typical
annuity portfolio consists of a large number of policies with maturities which
span decades, we conclude that the impact of longevity risk on the accurate
pricing of annuities is a significant issue to be further researched. In
addition, we find that mis-pricing is increasingly more pronounced for older
ages as well as for annuity policies having a longer maturity.Comment: 9 pages; conference pape
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