Recent results on Charm Physics from Fermilab

New high statistics, high resolution fixed target experiments producing $10^5$ - $10^6$ fully reconstructed charm particles are allowing a detailed study of the charm sector. Recent results on charm quark production from Fermilab fixed target experiments E791, SELEX and FOCUS are presented.Comment: 27 pages, corrected some typographical errors. To appear Proc. VII Mexican Workshop of Particles and Field, Merida Yuc. M\'ex., Nov. 199

On the intrinsic charm and the recombination mechanisms in charm hadron production

We study $\Lambda_c^\pm$ production in $pN$ and $\pi^-N$ interactions. Recent experimental data from the SELEX and E791 Collaborations at FNAL provide important information on the production mechanism of charm hadrons. In particular, the production of the $\Lambda_c$ baryon provides a good test of the intrinsic charm and the recombination mechanisms, which have been proposed to explain the so called leading particle effects.Comment: 11 pages, two figures (postscript), late

A Reproducible Study on Remote Heart Rate Measurement

This paper studies the problem of reproducible research in remote photoplethysmography (rPPG). Most of the work published in this domain is assessed on privately-owned databases, making it difficult to evaluate proposed algorithms in a standard and principled manner. As a consequence, we present a new, publicly available database containing a relatively large number of subjects recorded under two different lighting conditions. Also, three state-of-the-art rPPG algorithms from the literature were selected, implemented and released as open source free software. After a thorough, unbiased experimental evaluation in various settings, it is shown that none of the selected algorithms is precise enough to be used in a real-world scenario

Social ties and economic development

We develop a parsimonious general equilibrium model where agents allocate time across three activities: production, trade, and leisure. Leisure includes time spent socializing, which economizes transaction costs. Our framework yields multiple equilibria in terms of the number of social ties and predicts that the number of social ties is positively associated with development, a relationship we observe in cross-country data. The model captures additional dimensions of data, namely: (i) increasing income inequality, but converging growth rates; (ii) an association between weak social ties and development; and (iii) an association between number of social ties and size of the transaction sector.social capital; development; transaction costs; networks

Multi-pion production in the d d -> alpha X reaction

A simple model, based on two parallel and independent N N -> d pi processes, has recently been proposed for two-pion production in the d d -> alpha X reaction. It reproduces all observed features, including the sharp peak structure in momentum distributions (the ABC effect) and the strong oscillations in the deuteron vector and tensor analyzing powers. This model is now extended to describe also four-pion production with the same basic mechanism, but with two n p -> d pi pi processes as input. The calculations of the high missing mass spectra are within about 30% of the experimental data for beam energies in the range 1.9 < T_d < 2.4 GeV.Comment: 7 pages, LaTeX2e, 2 PS figures, submitted to Phys. Lett.

Dalitz plot analysis and branching fraction measurement of D+ and Ds+ -> pi+pi-pi+

Fermilab fixed target experiment E791 obtained a sample of $1172 \pm 61$ events of $D^+ \to \pi^- \pi^+ \pi^+$ and 848 $\pm 44$ events of $D_s^+ \to \pi^- \pi^+ \pi^+$ decays. We find respectively $B (D^+ \to \pi^- \pi^+ \pi^+) / B (D^+ \to K^- \pi^+ \pi^+) = 0.0311 \pm 0.0018 ^ {+0.0016}_{-0.0026}$ and $B(D_s^+ \to \pi^+ \pi^- \pi^+) / B(D_s^+ \to \phi \pi^+) = 0.245 \pm 0.028^{+0.019}_{-0.012}$. Using a coherent amplitude analysis to fit the Dalitz plot of the $D^+ \to \pi^- \pi^+ \pi^+$ decay, we find strong evidence for a scalar resonance of mass $478^{+24}_{-23} \pm 17$MeV/$c^2$ and width $324^{+42}_{-40} \pm 21$ MeV/$c^2$, compatible with what is expected for the isoscalar meson $\sigma$ >. The $D^+ \to \sigma(500) \pi^+$ fraction accounts for approximately half of all three-charged-pion decays of the $D^+$ . From the Dalitz plot analysis of the $D_s^+ \to \pi^- \pi^+ \pi^+$ decay events, we find significant contributions from the channels $\rho^0(770)\pi^+$, $\rho^0(1450)\pi^+$, $f_0(980)\pi^+$, $f_2(1270)\pi^+$, and $f_0(1370)\pi^+$. We also present new measurement of the masses and widths of the isoscalar resonances $f_0(980)$ and $f_0(1370)$.Comment: 4 pages, 4 figures, talk presented in BEACH2000, Valencia, Spai