3,041 research outputs found
Radiative two-pion decay of the tau lepton
We consider the bremsstrahlung and model-dependent contributions to the
radiative decay in the context of a
meson dominance model. We focus on several observables related to this decay,
including the branching ratio and the photon and di-pion spectra. Particular
attention is paid to the sensitivity of different observables upon the effects
of model-dependent contributions and of the magnetic dipole moment of the
vector meson. Important numerical differences are found with
respect to results obtained in the framework of chiral perturbation theory.Comment: 14 pages, 8 figures, submitted for publicatio
Folding and unfolding of a triple-branch DNA molecule with four conformational states
Single-molecule experiments provide new insights into biological processes
hitherto not accessible by measurements performed on bulk systems. We report on
a study of the kinetics of a triple-branch DNA molecule with four
conformational states by pulling experiments with optical tweezers and
theoretical modelling. Three distinct force rips associated with different
transitions between the conformational states are observed in the folding and
unfolding trajectories. By applying transition rate theory to a free energy
model of the molecule, probability distributions for the first rupture forces
of the different transitions are calculated. Good agreement of the theoretical
predictions with the experimental findings is achieved. Furthermore, due to our
specific design of the molecule, we found a useful method to identify
permanently frayed molecules by estimating the number of opened basepairs from
the measured force jump values.Comment: 17 pages, 12 figure
Inter-Particle Distribution Functions for One-Species Diffusion-Limited Annihilation, A+A->0
Diffusion-limited annihilation, , and coalescence, , may
both be exactly analyzed in one dimension. While the concentrations of
particles in the two processes bear a simple relation, the inter-particle
distribution functions (IPDF) exhibit remarkable differences. However, the IPDF
is known exactly only for the coalescence process. We obtain the IPDF for the
annihilation process, based on the Glauber spin approach and assuming that the
IPDF's of nearest-particle pairs are statistically independent. This assumption
is supported by computer simulations. Our analysis sheds further light on the
relationship between the annihilation and the coalescence models.Comment: 15 pages, plain TeX, 3 figures - available upon request (snail mail
Reactive dynamics on fractal sets: anomalous fluctuations and memory effects
We study the effect of fractal initial conditions in closed reactive systems
in the cases of both mobile and immobile reactants. For the reaction , in the absence of diffusion, the mean number of particles is shown to
decay exponentially to a steady state which depends on the details of the
initial conditions. The nature of this dependence is demonstrated both
analytically and numerically. In contrast, when diffusion is incorporated, it
is shown that the mean number of particles decays asymptotically as
, the memory of the initial conditions being now carried by the
dynamical power law exponent. The latter is fully determined by the fractal
dimension of the initial conditions.Comment: 7 pages, 2 figures, uses epl.cl
Improved Determination of the Hadronic Contribution to the Muon (g-2) and to alpha(M_Z**2) Using new Data from Hadronic Tau Decays
We have reevaluated the hadronic contribution to the anomalous magnetic
moment of the muon (g-2) and to the running of the QED fine structure constant
alpha(s) at s=M_Z**2. We incorporated new data from hadronic tau decays,
recently published by the ALEPH Collaboration. In addition, compared to
previous analyses, we use more extensive e+e- annihilation data sets. The
integration over the total hadronic cross section is performed using
experimental data up to 40 GeV and results from perturbative QCD above 40 GeV.
The improvement from tau data concerns mainly the pion form factor, where the
uncertainty in the corresponding integral could be reduced by more than a
factor of two. We obtain for the lowest order hadronic vacuum polarization
graph a_mu(had) = (695.0 +/- 15.0) x 10^{-10} and delta(alpha(M_Z**2))(had) =
(280.9 +/- 6.3) x 10^{-4} using e+e- data only. The corresponding results for
combined e+e- and tau data are a_mu(had) = (701.1 +/- 9.4) x 10^{-10} and
delta(alpha(M_Z**2))(had) = (281.7 +/- 6.2) x 10^{-4}, where the latter is
calculated using the contribution from the five lightest quarks.Comment: 23 pages, LaTex, 6 figures, Paper submitted to Zeitschrift fuer
Physik
The small pelagic fisheries in the South-Mediterranean Region (Western Mediterranean Sea): Past and present state
A review on small pelagic fisheries of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Northern Alboran Sea (Western Mediterranean Sea) was carried out. The study was focused on a very extense historical serie of landings (from 40’s to the present), as well as the number of fishery vessels and fishery effort during the last decade, and the assessment in 200
Virtual effects of light gauginos and higgsinos: a precision electroweak analysis of split supersymmetry
We compute corrections to precision electroweak observables in supersymmetry
in the limit that scalar superpartners are very massive and decoupled. This
leaves charginos and neutralinos and a Standard Model-like Higgs boson as the
only states with unknown mass substantially affecting the analysis. We give
complete formulas for the chargino and neutralino contributions, derive simple
analytic results for the pure gaugino and higgsino cases, and study the general
case. We find that in all circumstances, the precision electroweak fit improves
when the charginos and neutralinos are near the current direct limits. Larger
higgsino and gaugino masses worsen the fit as the theory predictions
asymptotically approach those of the Standard Model. Since the Standard Model
is considered by most to be an adequate fit to the precision electroweak data,
an important corollary to our analysis is that all regions of parameter space
allowed by direct collider constraints are also allowed by precision
electroweak constraints in split supersymmetry.Comment: 22 pages, 5 figures, v2: typos fixed and note adde
Child t-shirt size data set from 3D body scanner anthropometric measurements and a questionnaire
[EN] A dataset of a fit assessment study in children is presented. Anthropometric measurements of 113 children were obtained using a 3D body scanner. Children tested a t-shirt of different sizes and a different model for boys and girls, and their fit was assessed by an expert. This expert labeled the fit as 0 (correct), ¿1 (if the garment was small for that child), or 1 (if the garment was large for that child) in an ordered factor called Size-fit. Moreover, the fit was numerically assessed from 1 (very poor fit) to 10 (perfect fit) in a variable called Expert evaluation. This data set contains the differences between the reference mannequin of the evaluated size and the child¿s anthropometric measurements for 27 variables. Besides these variables, in the data set, we can also find the gender, the size evaluated, and the size recommended by the expert, including if an intermediate, but nonexistent size between two consecutive sizes would have been the right size. In total, there are 232 observations. The analysis of these data can be found in Pierola et al. (2016) [2].This work has been partially supported by Grants DPI2013-47279-C2-1-R and DPI2013-47279-C2-2-R.Pierola, A.; Epifanio, I.; Alemany Mut, MS. (2017). Child t-shirt size data set from 3D body scanner anthropometric measurements and a questionnaire. Data in Brief. 11:311-315. https://doi.org/10.1016/j.dib.2017.02.025S3113151
Spatial distribution of tuna larvae in the gulf of Gabes (Eastern Mediterranean) in relation with environmental parameters
Spatial distribution and ecology of the larvae of three tuna species (Thunnus thynnus, Auxis rochei and Euthynnus alletteratus) were studied during an ichthyoplankton survey carried out in the Gulf of Gabes (Tunisia) in June and July 2009. A total of 80 stations, distributed on a regular sampling grid, were sampled. The main objectives of this survey were to provide information on tuna larvae distribution in the Gulf of Gabes in relation to the environmental parameters. Regarding small tunas, larvae of A. rochei (bullet tuna) showed the more widespread distribution, being found at both inshore and offshore stations. E. alletteratus (Atlantic black skipjack) larvae were mainly found at the inshore stations covering the wide continental shelf of this region. On the other hand, larvae of the large migratory tuna T. Thynnus (Atlantic bluefin tuna), were mainly recorded at offshore stations, suggesting that spawning possibly takes place mainly near the shelf break. Regarding the biological and physical parameters examined, our results indicate that tuna larvae were mainly collected in oligotrophic and mixed waters resulting from the confluence of surface water of recent Atlantic origin and resident surface Mediterranean waters, as shown by their preference for lower chlorophyll a concentrations (from 1.4 to 2.5 mg m-3) and moderate salinity values (between 37.35 and 37.75). Significantly, tuna larvae seemed to avoid the more eutrophic and saltier waters of the gulf situated very close to the coast and around Kerkennah and Djerba islandsPublicado
Assessing the Effectiveness of a Gamified Social Network for Applying Privacy Concepts: An Empirical Study with Teens
[EN] The concept of privacy in online social networks (OSNs) is a challenge, especially for teenagers. Previous works deal with teaching about privacy using educational online content, and media literacy. However, these tools do not necessarily promote less risky behaviors, and do not allow the assessment of users' behavior after the learning period. Moreover, few research studies about the effects of social gamification have been performed for this population segment (i.e., teenagers). To address this problem in this article, we propose the use of gamification in an OSN called Pesedia to facilitate the teaching/learning process, and assess its effectiveness in promoting suitable privacy behaviors. We tested our proposal comparing teenagers' performance in two editions of a course about social networks, and privacy (with, and without gamification) for one month. We measured the impact of gamification in the participants' behaviors toward privacy concepts as a consequence of the privacy teaching/learning process, and the participants' engagement in the educational process. The results show that there are significant differences in participants' behavior regarding privacy, and engagement in the gamified social network. Moreover, there is also a significant difference in participants' engagement for the gamified male participants. The gamified social network proposed in this article may be relevant, and useful for educators who wish to develop, and enhance teenagers' privacy skills, or for a broader base of aspects related to the development of digital competences, and technology in education.This work was supported in part by the Spanish Government Project TIN2017-89156-R, and in part by the FPI under Grant BFS-2015-074498. (Corresponding author: Elena Del Vol.)Alemany-Bordera, J.; Del Val, E.; García-Fornes, A. (2020). Assessing the Effectiveness of a Gamified Social Network for Applying Privacy Concepts: An Empirical Study with Teens. IEEE Transactions on Learning Technologies. 13(4):777-789. https://doi.org/10.1109/TLT.2020.3026584S77778913
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