82 research outputs found

    Radiative Corrections for Pion Polarizability Experiments

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    We use the semi-analytical program RCFORGV to evaluate radiative corrections to one-photon radiative emission in the high-energy scattering of pions in the Coulomb field of a nucleus with atomic number Z. It is shown that radiative corrections can simulate a pion polarizability effect. The average effect was estimated for pion energies 40-600 GeV. We also study the range of applicability of the equivalent photon approximation in describing one-photon radiative emission.Comment: 11 pages (LaTex), 6 figures, 1 table. No changes in the paper. New submission because old files are corrupted in arXi

    Estudio del Proceso Software Personal (PSP) en un entorno académico

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    Resumen: El Proceso Software Personal (En Inglés, Personal Software Process oPSP) es un proceso individual cuyo objetivo es ayudar a los ingenieros ensoftware a medir y mejorar su productividad personal. El PSP suele enseñarseexclusivamente a profesionales, no obstante éste ha comenzado a incluirsecomo parte de cursos universitarios. En este trabajo se presenta un estudio sobrePSP efectuado en un entorno académico donde se analizan los siguientesindicadores: precisión en las estimaciones de tamaño y esfuerzo, calidad del producto así como productividad. Los resultados aquí reportados sugieren una mejoría parcial con respecto a la precisión de las estimaciones, una reducción sustantiva en la densidad de defectos de acuerdo a un factor de 6.6 y una productividad media de 53 líneas de código fuente por hora. Palabras clave: ingeniería en software; proceso software personal; PSP; medición del software; proceso de mejora continua

    Fermilab E791

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    Fermilab E791, a very high statistics charm particle experiment, recently completed its data taking at Fermilab's Tagged Photon Laboratory. Over 20 billion events were recorded through a loose transverse energy trigger and written to 8mm tape in the the 1991-92 fixed target run at Fermilab. This unprecedented data sample containing charm is being analysed on many-thousand MIP RISC computing farms set up at sites in the collaboration. A glimpse of the data taking and analysis effort is presented. We also show some preliminary results for common charm decay modes. Our present analysis indicates a very rich yield of over 200K reconstructed charm decays.Comment: 4 pages, 1 figure, LaTe

    Search for the Flavor-Changing Neutral-Current Decays D+π+μ+μD^+\to \pi^+ \mu^+ \mu^- and D+π+e+eD^+\to \pi^+ e^+ e^-

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    We report the results of a search for the flavor-changing neutral-current decays D+π+μ+μD^+\rightarrow \pi^+ \mu^+ \mu^- and D+π+e+eD^+\rightarrow \pi^+ e^+ e^- in data from Fermilab charm hadroproduction experiment E791. No signal above background is found, and we obtain upper limits on branching fractions, B(D+π+μ+μ)<1.8×105B(D^+\rightarrow \pi^+ \mu^+ \mu^-) < 1.8 \times 10^{-5} and B(D+π+e+e)<6.6×105B(D^+\rightarrow \pi^+ e^+ e^-) < 6.6 \times 10^{-5}, at the 90\% confidence level.Comment: nine pages with figures; compressed, uuencoded postscrip

    Direct measurement of the pion valence quark momentum distribution, the pion light-cone wave function squared

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    We present the first direct measurements of the pion valence quark momentum distribution which is related to the square of the pion light-cone wave function. The measurements were carried out using data on diffractive dissociation of 500 GeV/c π\pi^- into di-jets from a platinum target at Fermilab experiment E791. The results show that the qqˉ>|q\bar {q}> light-cone asymptotic wave function, which was developed using perturbative QCD methods, describes the data well for Q210 (GeV/c)2Q^2 \sim 10 ~{\rm (GeV/c)^2} or more. We also measured the transverse momentum distribution of the diffractive di-jets.Comment: 13 pages, 4 figure

    Observation of the Cabibbo-suppressed decay Xi_c+ -> p K- pi+

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    We report the first observation of the Cabibbo-suppressed charm baryon decay Xi_c+ -> p K- pi+. We observe 150 +- 22 events for the signal. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Sigma- beam. The branching fractions of the decay relative to the Cabibbo-favored Xi_c+ -> Sigma+ K- pi+ and Xi_c+ -> X- pi+ pi+ are measured to be B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> Sigma+ K- pi+) = 0.22 +- 0.06 +- 0.03 and B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> X- pi+ pi+) = 0.20 +- 0.04 +- 0.02, respectively.Comment: 5 pages, RevTeX, 3 figures (postscript), Submitted to Phys. Rev. Let

    Asymmetries between the production of D+ and D- mesons from 500 GeV/c pi- nucleon interactions as a function of xF and pt**2

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    We present asymmetries between the production of D+ and D- mesons in Fermilab experiment E791 as a function of xF and pt**2. The data used here consist of 74,000 fully-reconstructed charmed mesons produced by a 500 GeV/c pi- beam on C and Pt foils. The measurements are compared to results of models which predict differences between the production of heavy-quark mesons that have a light quark in common with the beam (leading particles) and those that do not (non-leading particles). While the default models do not agree with our data, we can reach agreement with one of them, PYTHIA, by making a limited number of changes to parameters used

    Mass Splitting and Production of Σc0\Sigma_c^0 and Σc++\Sigma_c^{++} Measured in 500GeV500 {GeV} π\pi^- -N Interactions

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    From a sample of 2722±782722 \pm 78 Λc+\Lambda_c^+ decaying to the pKπ+pK^-\pi^+ final state, we have observed, in the hadroproduction experiment E791 at Fermilab, 143±20143 \pm 20 Σc0\Sigma_c^0 and 122±18122 \pm 18 Σc++\Sigma_c^{++} through their decays to Λc+π±\Lambda_c^+ \pi^{\pm}. The mass difference M(Σc0)M(Λc+M(\Sigma_c^0) - M(\Lambda_c^+) is measured to be (167.38±0.29±0.15)MeV(167.38\pm 0.29\pm 0.15) {MeV}; for M(Σc++)M(Λc+)M(\Sigma_c^{++}) - M(\Lambda_c^+), we find (167.76±0.29±0.15)MeV(167.76\pm 0.29\pm0.15) {MeV}. The rate of Λc+\Lambda_c^+ production from decays of the Σc\Sigma_c triplet is (22\pm 2\pm 3) {%} of the total Λc+\Lambda_c^+ production assuming equal rate of production from all three, as measured for Σc0\Sigma_c^0 and Σc++\Sigma_c^{++}. We do not observe a statistically significant Σc\Sigma_c baryon-antibaryon production asymmetry. The xFx_F and pt2p_t^2 spectra of Λc+\Lambda_c^+ from Σc\Sigma_c decays are observed to be similar to those for all Λc+\Lambda_c^+'s produced.Comment: 15 pages, uuencoded postscript 3 figures uuencoded, tar-compressed fil
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