23,985 research outputs found
Angular distributions of γ rays from the 7Li(p,γ) reaction at low energies
Angular distributions of the 14–17 MeV γ rays from the 7Li(p,γ) reaction at Ep=450, 402, and 80 keV were measured at 0°≤θlab≤135°, using a BGO detector and a 28-μg/cm2 LiF target. The angular distributions at Ep=450 and 402 keV agree with the previous results by Mainsbridge; at Ep=80 keV the ground-state transition is anisotropic on the order of 20%, confirming recent results by Chasteler et al
Should You Be Allowed to Use Your Cellular Phone While Driving?
Regulation of the use of cellular phones by individuals while driving is now commonplace outside the United States and has been proposed in a number of jurisdictions in the United States. There is growing concern that using cellular phones while driving leads to increases in accidents and fatalities. This paper provides an economic analysis of regulatory options for addressing cellular phone usage by drivers of vehicles. While large uncertainties surrounding both benefits and costs exist, a key conclusion is that banning drivers from using cellular phones is a bad idea. Our best estimate is that the costs of a ban are likely to exceed benefits by about $20 billion annually. Less intrusive regulation, such as requiring the use of a hands-free device that would allow a driver to use both hands for steering also is not likely to be economically justified.
Parametric LTL on Markov Chains
This paper is concerned with the verification of finite Markov chains against
parametrized LTL (pLTL) formulas. In pLTL, the until-modality is equipped with
a bound that contains variables; e.g., asserts that
holds within time steps, where is a variable on natural
numbers. The central problem studied in this paper is to determine the set of
parameter valuations for which the probability to
satisfy pLTL-formula in a Markov chain meets a given threshold , where is a comparison on reals and a probability. As for pLTL
determining the emptiness of is undecidable, we consider
several logic fragments. We consider parametric reachability properties, a
sub-logic of pLTL restricted to next and , parametric B\"uchi
properties and finally, a maximal subclass of pLTL for which emptiness of is decidable.Comment: TCS Track B 201
Parameter-Independent Strategies for pMDPs via POMDPs
Markov Decision Processes (MDPs) are a popular class of models suitable for
solving control decision problems in probabilistic reactive systems. We
consider parametric MDPs (pMDPs) that include parameters in some of the
transition probabilities to account for stochastic uncertainties of the
environment such as noise or input disturbances.
We study pMDPs with reachability objectives where the parameter values are
unknown and impossible to measure directly during execution, but there is a
probability distribution known over the parameter values. We study for the
first time computing parameter-independent strategies that are expectation
optimal, i.e., optimize the expected reachability probability under the
probability distribution over the parameters. We present an encoding of our
problem to partially observable MDPs (POMDPs), i.e., a reduction of our problem
to computing optimal strategies in POMDPs.
We evaluate our method experimentally on several benchmarks: a motivating
(repeated) learner model; a series of benchmarks of varying configurations of a
robot moving on a grid; and a consensus protocol.Comment: Extended version of a QEST 2018 pape
A complete one-loop calculation of electroweak supersymmetric effects in -channel single top production at LHC
We have computed the complete one-loop electroweak effects in the MSSM for
single top (and single antitop) production in the -channel at hadron
colliders, generalizing a previous analysis performed for the dominant
final state and fully including QED effects. The results are quite similar for
all processes. The overall Standard Model one-loop effect is small, of the few
percent size. This is due to a compensation of weak and QED contributions that
are of opposite sign. The genuine SUSY contribution is generally quite modest
in the mSUGRA scenario. The experimental observables would therefore only
practically depend, in this framework, on the CKM coupling.Comment: 25 pages, several eps figures. Update corresponding to published
versio
Full O(alpha) corrections to e+e- -> sf_i sf_j
We present a complete precision analysis of the sfermion pair production
process e+e- -> sf_i sf_j (f = t, b, tau, nu_tau) in the Minimal Supersymmetric
Standard Model. Our results extend the previously calculated weak corrections
by including all one-loop corrections together with higher order QED
corrections. We present the details of the analytical calculation and discuss
the renormalization scheme. The numerical analysis shows the results for total
cross-sections, forward-backward and left-right asymmetries. It is based on the
SPS1a' point from the SPA project. The complete corrections are about 10% and
have to be taken into account in a high precision analysis.Comment: 32 pages, 24 figures, RevTeX
Determination of Strong-Interaction Widths and Shifts of Pionic X-Rays with a Crystal Spectrometer
Pionic 3d-2p atomic transitions in F, Na, and Mg have been studied using a bent crystal spectrometer. The pionic atoms were formed in the production target placed in the external proton beam of the Space Radiation Effects Laboratory synchrocyclotron. The observed energies and widths of the transitions are E=41679(3) eV and Γ=21(8) eV, E=62434(18) eV and Γ=22(80) eV, E=74389(9) eV and Γ=67(35) eV, in F, Na, and Mg, respectively. The results are compared with calculations based on a pion-nucleus optical potential
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