51,053 research outputs found
Recent progress in the transition radiation detector techniques
A list of some of the major experimental achievements involving charged particles in the relativistic region are presented. With the emphasis mainly directed to the X-ray region, certain modes of application of the transition radiation for the identification and separation of relativistic charged particles are discussed. Some recent developments in detection techniques and improvements in detector performances are presented. Experiments were also carried out to detect the dynamic radiation, but no evidence of such an effect was observed
New Production Mechanism of Neutral Higgs Bosons with Right scalar tau neutrino as the LSP
Motived by the neutrino oscillation data, we consider the lightest tau
sneutrino (which is mostly the right tau sneutrino) to be
the lightest supersymmetric particle (LSP) in the framework of the minimal
supersymmetric Standard Model. Both the standard and the non-standard trilinear
scalar coupling terms are included for the right tau sneutrino interactions.
The decay branching ratio of
can become so large that the production rate of the lightest neutral Higgs
boson () can be largely enhanced at electron or hadron colliders, either
from the direct production of or from the decay of
charginos, neutralinos, sleptons, and the cascade decay of squarks and gluinos,
etc. Furthermore, because of the small LSP annihilation rate, can be a good candidate for cold dark matter.Comment: 11 pages, RevTex, 3 eps figures. We clarify the theoretical framework
of this study, with a note added in the end, and correct an equation, with
updated figure
Avoiding the Detector Blinding Attack on Quantum Cryptography
We show the detector blinding attack by Lydersen et al [1] will be
ineffective on most single photon avalanche photodiodes (APDs) and certainly
ineffective on any detectors that are operated correctly. The attack is only
successful if a redundant resistor is included in series with the APD, or if
the detector discrimination levels are set inappropriately
Quantum key distribution over 122 km of standard telecom fiber
We report the first demonstration of quantum key distribution over a standard
telecom fiber exceeding 100 km in length. Through careful optimisation of the
interferometer and single photon detector, we achieve a quantum bit error ratio
of 8.9% for a 122km link, allowing a secure shared key to be formed after error
correction and privacy amplification. Key formation rates of up to 1.9 kbit/sec
are achieved depending upon fiber length. We discuss the factors limiting the
maximum fiber length in quantum cryptography
Optimal vaccination in a stochastic epidemic model of two non-interacting populations
Developing robust, quantitative methods to optimize resource allocations in
response to epidemics has the potential to save lives and minimize health care
costs. In this paper, we develop and apply a computationally efficient
algorithm that enables us to calculate the complete probability distribution
for the final epidemic size in a stochastic Susceptible-Infected-Recovered
(SIR) model. Based on these results, we determine the optimal allocations of a
limited quantity of vaccine between two non-interacting populations. We compare
the stochastic solution to results obtained for the traditional, deterministic
SIR model. For intermediate quantities of vaccine, the deterministic model is a
poor estimate of the optimal strategy for the more realistic, stochastic case.Comment: 21 pages, 7 figure
NNLO QCD Corrections to t-channel Single Top-Quark Production and Decay
We present a fully differential next-to-next-to-leading order calculation of
t-channel single top-quark production and decay at the LHC under narrow-width
approximation and neglecting cross-talk between incoming protons. We focus on
the fiducial cross sections at 13 TeV, finding that the next-to-next-to-leading
order QCD corrections can reach the level of -6%. The scale variations are
reduced to the level of a percent. Our results can be used to improve
experimental acceptance estimates and the measurements of the single top-quark
production cross section and the top-quark electroweak couplings.Comment: 6 pages, 4 figures, version appear on PRD rapid communicatio
The Impact of Type Ia Supernovae in Quiescent Galaxies: I. Formation of the Multiphase Interstellar medium
A cool phase of the interstellar medium has been observed in many giant
elliptical galaxies, but its origin remains unclear. We propose that uneven
heating from Type Ia supernovae (SNe Ia), together with radiative cooling, can
lead to the formation of the cool phase. The basic idea is that since SNe Ia
explode randomly, gas parcels which are not directly heated by SN shocks will
cool, forming multiphase gas. We run a series of idealized high-resolution
numerical simulations, and find that cool gas develops even when the overall
SNe heating rate exceeds the cooling rate by a factor as large as 1.4.
We also find that the time for multiphase gas development depends on the gas
temperature. When the medium has a temperature K, the cool
phase forms within one cooling time \tc; however, the cool phase formation is
delayed to a few times \tc\ for higher temperatures. The main reason for the
delay is turbulent mixing. Cool gas formed this way would naturally have a
metallicity lower than that of the hot medium. For constant , there is
more turbulent mixing for higher temperature gas. We note that this mechanism
of producing cool gas cannot be captured in cosmological simulations, which
usually fail to resolve individual SN remnants.Comment: 16 pages, 11 figures, published by ApJ. This work is part of the
SMAUG project, see more information at
https://www.simonsfoundation.org/flatiron/center-for-computational-astrophysics/galaxy-formation/smaug/papersplash
Origin of the X-ray Emission in the Nuclei of FR Is
We investigate the X-ray origin in FRIs using the multi-waveband high
resolution data of eight FR I sources, which have very low Eddington ratios. We
fit their multi-waveband spectrum using a coupled accretion-jet model. We find
that X-ray emission in the source with the highest L_X (~1.8*10^-4 L_Edd) is
from the advection-dominated accretion flow (ADAF). Four sources with moderate
L_X(~several*10^-6 L_Edd) are complicated. The X-ray emission of one FR I is
from the jet, and the other three is from the sum of the jet and ADAF. The
X-ray emission in the three least luminous sources (L_X<1.0*10^-6L_Edd) is
dominated by the jet. These results roughly support the predictions of Yuan and
Cui(2005) where they predict that when the X-ray luminosity of the system is
below a critical value, the X-radiation will not be dominated by the emission
from the ADAF any longer, but by the jet. We also find that the accretion rates
in four sources must be higher than the Bondi rates, which implies that other
fuel supply (e.g., stellar winds) inside the Bondi radius should be important.Comment: 6 pages. To published in Journal of Physics, in proceedings of "The
Universe under the Microscope - Astrophysics at High Angular Resolution" (Bad
Honnef, Germany, April 2008), eds. R. Schoedel, A. Eckart, S. Pfalzner, and
E. Ro
Gluon-gluon contributions to the production of continuum diphoton pairs at hadron colliders
We compute the contributions to continuum photon pair production at hadron
colliders from processes initiated by gluon-gluon and gluon-quark scattering
into two photons through a four-leg virtual quark loop. Complete two-loop cross
sections in perturbative quantum chromodynamics are combined with contributions
from soft parton radiation resummed to all orders in the strong coupling
strength. The structure of the resummed cross section is examined in detail,
including a new type of unintegrated parton distribution function affecting
azimuthal angle distributions of photons in the pair's rest frame. As a result
of this analysis, we predict diphoton transverse momentum distributions in
gluon-gluon scattering in wide ranges of kinematic parameters at the Fermilab
Tevatron collider and the CERN Large Hadron Collider.Comment: 28 pages, 11 figures; published versio
A modal model for diffraction gratings
A description of an algorithm for a rather general modal grating calculation
is presented. Arbitrary profiles, depth, and permittivity are allowed. Gratings
built up from sub-gratings are allowed, as are coatings on the sidewalls of
lines, and arbitrary complex structure. Conical angles and good conductors are
supported
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