ReDecay: A novel approach to speed up the simulation at LHCb

With the steady increase in the precision of flavour physics measurements collected during LHC Run 2, the LHCb experiment requires simulated data samples of larger and larger sizes to study the detector response in detail. The simulation of the detector response is the main contribution to the time needed to simulate full events. This time scales linearly with the particle multiplicity. Of the dozens of particles present in the simulation only the few participating in the signal decay under study are of interest, while all remaining particles mainly affect the resolutions and efficiencies of the detector. This paper presents a novel development for the LHCb simulation software which re-uses the rest of the event from previously simulated events. This approach achieves an order of magnitude increase in speed and the same quality compared to the nominal simulation

Anelastic relaxation and 139^{139}La NQR in La2−x_{2-x}Srx_xCuO4_4 around the critical Sr content x=0.02

Anelastic relaxation and $^{139}$La NQR relaxation measurements in La$_{2-x}$Sr$_x$CuO$_4$ for Sr content x around 2 and 3 percent, are presented and discussed in terms of spin and lattice excitations and ordering processes. It is discussed how the phase diagram of La$_{2-x}$Sr$_x$CuO$_4$ at the boundary between the antiferromagnetic (AF) and the spin-glass phase (x = 0.02) could be more complicate than previous thought, with a transition to a quasi-long range ordered state at T = 150 K, as indicated by recent neutron scattering data. On the other hand, the $^{139}$La NQR spectra are compatible with a transition to a conventional AF phase around T = 50 K, in agreement with the phase diagram commonly accepted in the literature. In this case the relaxation data, with a peak of magnetic origin in the relaxation rate around 150 K at 12 MHz and the anelastic counterparts around 80 K in the kHz range, yield the first evidence in La$_{1.98}$Sr$_{0.02}$CuO$_4$ of freezing involving simultaneously lattice and spin excitations. This excitation could correspond to the motion of charged stripes.Comment: 10 pages, 8 figure

A deep and wide-field view at the IC 2944 / 2948 complex in Centaurus

We employed the ESO MPI wide-field camera and obtained deep images in the VIc pass-bands in the region of the IC 2944/2948 complex (l ~ 294; b ~ -1), and complemented them with literature and archival data. We used this material to derive the photometric, spectroscopic and kinematic properties of the brightest (V < 16) stars in the region. The VI deep photometry on the other end, helped us to unravel the lower main sequence of a few, possibly physical, star groups in the area. Our analysis confirmed previous suggestions that the extinction toward this line of sight follows the normal law (Rv = 3.1). We could recognize B-type stars spread in distance from a few hundred pc to at least 2 kpc. We found two young groups (age ~ 3 Myr) located respectively at about 2.3 and 3.2 kpc from the Sun. They are characterized by a significant variable extinction (E(B-V) ranging from 0.28 to 0.45 mag), and host a significant pre-main sequence population. We computed the initial mass functions for these groups and obtained slopes Gamma from -0.94 to -1.02 (e_Gamma = 0.3), in a scale where the classical Salpeter law is -1.35. We estimated the total mass of both main stellar groups in ~ 1100$and ~ 500$ Mo, respectively. Our kinematic analysis indicated that both groups of stars deviate from the standard rotation curve of the Milky Way, in line with literature results for this specific Galactic direction. Finally, along the same line of sight we identified a third group of early-type stars located at ~ 8 kpc from the Sun. This group might be located in the far side of the Sagittarius-Carina spiral arm.Comment: 13 pages, 11 figures, accepted for publication in MNRA

EL DISEÑO POLITICO DE LOS 90 Y LOS DESAFIOS DE LA GESTION UNIVERSITARIA.

La presentación se desarrollará a partir de la descripción de tres ejes condicionantes de la política en educación superior : El quiebre de la idea de progreso unida a la educación en la configuración del contexto socio-económico de los 90 y el cambio educativo La matriz cultural interna que ha impregnado la política universitaria a partir de los modelos de vinculación estado- sistema superior en los últimos 30 años La agenda de problemas del sector y la Ley Superior. Aspectos que se han visto favorecidos y aspectos bloqueados, inhibidos Se parte de entender que las políticas de Educación Superior constituyen un capítulo fundamental en el entramado de políticas sociales globales de un país, ya que ellas determinan una forma particular de distribución social del conocimiento, un sistema particular de producción y una herramienta para restringir o ampliar los niveles culturales de la población, por ende los tres ejes que se describirán constituyen a nuestro entender condicionantes fundamentales en el análisis del futuro de la universidad

Singular del Pezzo fibrations and birational rigidity

A known conjecture of Grinenko in birational geometry asserts that a Mori fibre space with the structure of del Pezzo fibration of low degree is birationally rigid if and only if its anticanonical class is an interior point in the cone of mobile divisors. The conjecture is proved to be true for smooth models (with a generality assumption for degree 3). It is speculated that the conjecture holds for, at least, Gorenstein models in degree 1 and 2. In this article, I present a (Gorenstein) counterexample in degree 2 to this conjecture.Comment: This is essentially a more detailed version of the second section of arXiv:1310.5548. To appear in the proceedings of the conference 'Groups of Automorphisms in Birational and Affine Geometry', held in Trento, Italy, 201