8,532 research outputs found
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 La NQR in LaSrCuO around the critical Sr content x=0.02
Anelastic relaxation and La NQR relaxation measurements in
LaSrCuO 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 LaSrCuO 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 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 LaSrCuO 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 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 polÃtica 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 polÃtica 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 polÃticas de Educación Superior constituyen un capÃtulo fundamental en el entramado de polÃticas sociales globales de un paÃs, 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
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