Local Alignment of the BABAR Silicon Vertex Tracking Detector

The BABAR Silicon Vertex Tracker (SVT) is a five-layer double-sided silicon detector designed to provide precise measurements of the position and direction of primary tracks, and to fully reconstruct low-momentum tracks produced in e+e- collisions at the PEP-II asymmetric collider at Stanford Linear Accelerator Center. This paper describes the design, implementation, performance, and validation of the local alignment procedure used to determine the relative positions and orientations of the 340 SVT wafers. This procedure uses a tuned mix of in-situ experimental data and complementary lab-bench measurements to control systematic distortions. Wafer positions and orientations are determined by minimizing a chisquared computed using these data for each wafer individually, iterating to account for between-wafer correlations. A correction for aplanar distortions of the silicon wafers is measured and applied. The net effect of residual mis-alignments on relevant physical variables is evaluated in special control samples. The BABAR data-sample collected between November 1999 and April 2008 is used in the study of the SVT stability.Comment: 21 pages, 20 figures, 3 tables, submitted to Nucl. Instrum. Meth.

Perceptual compensation for the effects of reverberation on consonant identification: Evidence from studies with monaural stimuli

Mounting evidence suggests that listeners perceptually compensate for the adverse effects of reverberation in rooms when listening to speech monaurally. However, it is not clear whether the underlying perceptual mechanism would be at all effective in the high levels of stimulus uncertainty that are present in everyday listening. Three experiments investigated monaural compensation with a consonant identification task in which listeners heard different speech on each trial. Consonant confusions frequently arose when a greater degree of reverberation was added to a test-word than to its surrounding context, but compensation became apparent in conditions where the context reverberation was increased to match that of the test-word; here, the confusions were largely resolved. A second experiment shows that information from the test-word itself can also effect compensation. Finally, the time course of compensation was examined by applying reverberation to a portion of the preceding context; consonant identification improves as this portion increases in duration. These findings indicate a monaural compensation mechanism that is likely to be effective in everyday listening, allowing listeners to recalibrate as their reverberant environment changes

Gauge Invariant Variational Approach with Fermions: the Schwinger Model

We extend the gauge invariant variational approach of Phys. Rev. D52 (1995) 3719, hep-th/9408081, to theories with fermions. As the simplest example we consider the massless Schwinger model in 1+1 dimensions. We show that in this solvable model the simple variational calculation gives exact results.Comment: 14 pages, 1 figur

Dispersive analysis of the decay eta -> 3 pi

We demonstrate that the decay eta -> 3 pi represents a sensitive probe for the breaking of chiral symmetry by the quark masses. The transition amplitude is proportional to the mass ratio (m_d^2-m_u^2)/(m_s^2-m^2). The factor of proportionality is calculated by means of dispersion relations, using chiral perturbation theory to determine the subtraction constants. The theoretical uncertainties in the result are shown to be remarkably small, so that eta-decay may be used to accurately measure this ratio of quark masses.Comment: 14 pages, 1 figur

Vulnerabilidad sociodemográfica en el Caribe: examen de los factores sociales y demográficos que impiden un desarrollo equitativo con participación ciudadana en los albores del siglo XXI

Incluye BibliografíaResumen Partiendo del análisis que la CEPAL efectuó en su documento Equidad, desarrollo y ciudadanía ¾presentado en el vigesimoctavo período de sesiones¾ sobre la vulnerabilidad ambiental, geográfica, económica e institucional que afecta a los pequeños Estados insulares del Caribe, se identifican y discuten las estructuras, procesos y conductas sociodemográficas que entrañan riesgos para las personas, hogares y comunidades de estos Estados. El análisis se concentra en tres asuntos sociodemográficos. Primero, la fecundidad, que sigue siendo temprana y alta entre los grupos pobres de la población y todavía implica sesgos de género marcados, sobre todo para las jefas de hogar que deben hacerse cargo de la crianza de la prole. Segundo, el envejecimiento de la población, proceso bastante avanzado en algunas islas del Caribe y cuyo enfrentamiento requiere de una cuidadosa preparación previa cuidadosa. Tercero, la migración, en particular la internacional, que en algunos territorios de esta región presenta niveles muy elevados; pese a las oportunidades que la migración ofrece para personas y comunidades, drena parte de los recursos humanos calificados de los países del Caribe y expone a los migrantes, en particular los menos calificados, a tratos discriminatorios e injustos. El documento concluye con orientaciones de política para hacer frente a estos asuntos, que configuran la vulnerabilidad sociodemográfica en el Caribe

Fractons in Twisted Multiflavor Schwinger Model

We consider two-dimensional QED with several fermion flavors on a finite spatial circle. A modified version of the model with {\em flavor-dependent} boundary conditions $\psi_p(L) = e^{2\pi ip/ N} \psi_p(0)$, $p = 1, \ldots , N$ is discussed ($N$ is the number of flavors). In this case a non-contactable contour in the space of the gauge fields is {\em not} determined by large gauge transformations. The Euclidean path integral acquires the contribution from the gauge field configurations with fractional topological charge. The configuration with $\nu = 1/N$ is responsible for the formation of the fermion condensate $\langle\bar{\psi}_p \psi_p\rangle_0$. The condensate dies out as a power of $L^{-1}$ when the length $L$ of the spatial box is sent to infinity. Implications of this result for non-abelian gauge field theories are discussed in brief.Comment: 29 pages, 3 figures available upon request, Report TPI-MINN-94-24-T Plain LATE

On Epsilon Expansions of Four-loop Non-planar Massless Propagator Diagrams

We evaluate three typical four-loop non-planar massless propagator diagrams in a Taylor expansion in dimensional regularization parameter $\epsilon=(4-d)/2$ up to transcendentality weight twelve, using a recently developed method of one of the present coauthors (R.L.). We observe only multiple zeta values in our results.Comment: 3 pages, 1 figure, results unchanged, discussion improved, to appear in European Physical Journal

Deeply virtual electroproduction of photons and mesons on the nucleon : leading order amplitudes and power corrections

We estimate the leading order amplitudes for exclusive photon and meson electroproduction reactions at large Q^2 in the valence region in terms of skewed quark distributions. As experimental investigations can currently only be envisaged at moderate values of Q^2, we estimate power corrections due to the intrinsic transverse momentum of the partons in the meson wavefunction and in the nucleon. To this aim the skewed parton distribution formalism is generalized so as to include the parton intrinsic transverse momentum dependence. Furthermore, for the meson electroproduction reactions, we calculate the soft overlap type contributions and compare with the leading order amplitudes. We give first estimates for these different power corrections in kinematics which are relevant for experiments in the near future.Comment: 59 pages, 21 figure

(Anti-)self-dual homogeneous vacuum gluon field as an origin of confinement and SUL(NF)×SUR(NF)SU_L(N_F)\times SU_R(N_F) symmetry breaking in QCD

It is shown that an (anti-)self-dual homogeneous vacuum gluon field appears in a natural way within the problem of calculation of the QCD partition function in the form of Euclidean functional integral with periodic boundary conditions. There is no violation of cluster property within this formulation, nor are parity, color and rotational symmetries broken explicitly. The massless limit of the product of the quark masses and condensates, $m_f \langle \bar\psi_f \psi_f \rangle$, is calculated to all loop orders. This quantity does not vanish and is proportional to the gluon condensate appearing due to the nonzero strength of the vacuum gluon field. We conclude that the gluon condensate can be considered as an order parameter both for confinement and chiral symmetry breaking.Comment: 16 pages, LaTe

Quantum-critical pairing with varying exponents

We analyse the onset temperature T_p for the pairing in cuprate superconductors at small doping, when tendency towards antiferromagnetism is strong. We consider the model of Moon and Sachdev (MS), which assumes that electron and hole pockets survive in a paramagnetic phase. Within this model, the pairing between fermions is mediated by a gauge boson, whose propagator remains massless in a paramagnet. We relate the MS model to a generic \gamma-model of quantum-critical pairing with the pairing kernel \lambda (\Omega) \propto 1/\Omega^{\gamma}. We show that, over some range of parameters, the MS model is equivalent to the \gamma-model with \gamma =1/3 (\lambda (\Omega) \propto \Omega^{-1/3}). We find, however, that the parameter range where this analogy works is bounded on both ends. At larger deviations from a magnetic phase, the MS model becomes equivalent to the \gamma-model with varying \gamma >1/3, whose value depends on the distance to a magnetic transition and approaches \gamma =1 deep in a paramagnetic phase. Very near the transition, the MS model becomes equivalent to the \gamma-model with varying \gamma <1/3. Right at the magnetic QCP, the MS model is equivalent to the \gamma-model with \gamma =0+ (\lambda (\Omega) \propto \log \Omega), which is the model for color superconductivity. Using this analogy, we verified the formula for T_c derived for color superconductivity.Comment: 10 pages, 8 figures, submitted to JLTP for a focused issue on Quantum Phase Transition