1,008 research outputs found
Mu-tau neutrino refraction and collective three-flavor transformations in supernovae
We study three-flavor collective neutrino transformations in the
dense-neutrino region above the neutrino sphere of a supernova core. We find
that two-flavor conversions driven by the atmospheric mass difference and the
13-mixing angle capture the full effect if one neglects the second-order
difference between the muon and tau neutrino refractive index. Including this
"mu-tau matter term" provides a resonance at a density of approximately 3 x
10^7 g cm^-3 that typically causes significant modifications of the overall
electron neutrino and antineutrino survival probabilities. This effect is
surprisingly sensitive to deviations from maximal 23-mixing, being different
for each octant.Comment: 9 pages, 7 figures. New presentation of results, version to be
published in PR
Interplay between collective effects and nonstandard interactions of supernova neutrinos
We consider the effect of non-standard neutrino interactions (NSI, for short) on the propagation of neutrinos through the supernova (SN) envelope within a three-neutrino framework and taking into account the presence of a neutrino background. We find that for given NSI parameters, with strength generically denoted by εij, neutrino evolution exhibits a significant time dependence. For |εττ|≳ 10−3 the neutrino survival probability may become sensitive to the θ23 octant and the sign of εττ. In particular, if εττ≳10−2 an internal I-resonance may arise independently of the matter density. For typical values found in SN simulations this takes place in the same dense-neutrino region above the neutrinosphere where collective effects occur, in particular during the synchronization regime. This resonance may lead to an exchange of the neutrino fluxes entering the bipolar regime. The main consequences are (i) bipolar conversion taking place for normal neutrino mass hierarchy and (ii) a transformation of the flux of low-energy νe, instead of the usual spectral swap
Astrophysics at n-TOF facility
The neutron time of flight (n_TOF) facility at CERN is a neutron spallation source, its white neutron energy spectrum ranges from thermal to several GeV, covering the full energy range of interest for nuclear astrophysics, in particular for measurements of the neutron capture cross section required in s-process nucleosynthesis. This contribution gives an overview on the astrophysical program made at n_TOF facility, the results and the implications will be reported.Postprint (published version
Study of the background in the measuring station at the n_TOF facility at CERN: sources and solutions
A background roughly two orders of magnitude higher than tolerable was found in the n_TOF facility at CERN during the first measurements. This note describes a series of additional measurements performed in the n_TOF experimental area to study the origin and the characteristics of the background. The program of these measurements was determined taking into account the results from the simulations carried out by the EET group. A first phase of measurements confirmed the results of the simulations, namely that the dominant source of background was due to neutrons generated by negative muon capture. Actions to reduce the background were taken according to the results from both measurements and simulations. An iron shielding wall 3.2 m thick was then placed in between the sweeping magnet and the second collimator, with the purpose of stopping most of the muons. In a second phase of measurements, results showed that the additional shielding reduced the main component of the background by about a factor of 30.Postprint (author's final draft
Physics potential of future supernova neutrino observations
We point out possible features of neutrino spectra from a future galactic
core collapse supernova that will enhance our understanding of neutrino mixing
as well as supernova astrophysics. We describe the neutrino flavor conversions
inside the star, emphasizing the role of "collective effects" that has been
appreciated and understood only very recently. These collective effects change
the traditional predictions of flavor conversion substantially, and enable the
identification of neutrino mixing scenarios through signatures like Earth
matter effects.Comment: 8 pages, uses jpconf.cls. Talk given at Neutrino 2008, Christchurch,
NZ. Some entries in Table 2 have been correcte
Ear, nose and throat manifestations in pemphigus vulgaris
Pemphigus vulgaris (PV) is an autoimmune disease characterized by mucocutaneous intraepithelial blisters and pathogenic autoantibodies against desmoglein 3. There are two clinical forms: mucosal (MPV) and mucocutaneous (MCPV). The frequency of ear, nose and throat (ENT) involvement in PV is not clearly defined. Only a few isolated individual cases have been reported.
OBJECTIVES: The objective of our study was to determine the incidence of ENT involvement in patients with PV.
PATIENTS: We studied prospectively all 16 patients diagnosed with PV and treated in the Department of Dermatology of the University Clinic of Navarra between 2001 and 2005. They were 10 cases of MPV and six cases of MCPV. All patients were evaluated for ENT manifestations by endoscopic examination.
RESULTS: Of the 16 patients, 13 presented with throat symptoms (81%), 12 pharyngeal (75%) and seven laryngeal symptoms (44%). Fourteen patients (88%) had active PV lesions on endoscopic evaluation (eight patients had active lesions on both pharyngeal and laryngeal mucosa, four had PV lesions only on laryngeal mucosa and two had PV lesions on pharyngeal mucosa). Laryngeal lesions were most commonly present in MPV patients. The frequency of nasal symptoms (38%) was lower than active PV lesions (62%) found on ENT examination. Oral symptoms and oral active PV lesions were the most frequent findings (94%). Only three patients with MCPV showed erosions on the external auditory canal.
CONCLUSIONS: As ENT endoscopy allows more extensive areas of mucosa to be examined than simple visual inspection, we recommend that it be included in the examination of all patients with PV. By obtaining more complete information concerning the extent of the disease, a more accurate diagnosis can be made, better choice of drug and dose may be decided and, ultimately, response to treatment may be improved
S_3-flavour symmetry as realized in lepton flavour violating processes
A variety of lepton flavour violating effects related to the recent discovery
of neutrino oscillations and mixings is here systematically discussed in terms
of an S_3-flavour permutational symmetry. After a brief review of some relevant
results on lepton masses and mixings, that had been derived in the framework of
a Minimal S_3-Invariant Extension of the Standard Model, we derive explicit
analytical expressions for the matrices of the Yukawa couplings and compute the
branching ratios of some selected flavour changing neutral current (FCNC)
processes, as well as, the contribution of the exchange of neutral flavour
changing scalars to the anomaly of the muon's magnetic moment as functions of
the masses of the charged leptons and the neutral Higgs bosons. We find that
the S_3 x Z_2 flavour symmetry and the strong mass hierarchy of the charged
leptons strongly suppress the FCNC processes in the leptonic sector well below
the present experimental upper bounds by many orders of magnitude. The
contribution of FCNC to the anomaly of the muon's magnetic moment is small but
non-negligible.Comment: 23 pages, one figure. To appear in J. Phys A: Mathematical and
Theoretical (SPE QTS5
Collective neutrino flavor transitions in supernovae and the role of trajectory averaging
Non-linear effects on supernova neutrino oscillations, associated with
neutrino self-interactions, are known to induce collective flavor transitions
near the supernova core for theta_13 \neq 0. In scenarios with very shallow
electron density profiles, these transformations have been shown to couple with
ordinary matter effects, jointly producing spectral distortions both in normal
and inverted hierarchy. In this work we consider a complementary scenario,
characterized by higher electron density, as indicated by post-bounce
shock-wave simulations. In this case, early collective flavor transitions are
decoupled from later, ordinary matter effects. Moreover, such transitions
become more amenable to both numerical computations and analytical
interpretations in inverted hierarchy, while they basically vanish in normal
hierarchy. We numerically evolve the neutrino density matrix in the region
relevant for self-interaction effects. In the approximation of averaged
intersection angle between neutrino trajectories, our simulations neatly show
the collective phenomena of synchronization, bipolar oscillations, and spectral
split, recently discussed in the literature. In the more realistic (but
computationally demanding) case of non-averaged neutrino trajectories, our
simulations do not show new significant features, apart from the smearing of
``fine structures'' such as bipolar nutations. Our results seem to suggest
that, at least for non-shallow matter density profiles, averaging over neutrino
trajectories plays a minor role in the final outcome. In this case, the swap of
nu_e and nu_{\mu,\tau} spectra above a critical energy may represent an
unmistakable signature of the inverted hierarchy, especially for theta_{13}
small enough to render further matter effects irrelevant.Comment: v2 (27 pages, including 9 eps figures). Typos removed, references
updated. Minor comments added. Corrected numerical errors in Eq.(6). Matches
the published versio
Study of the photon strength function of 152SM in resonance neutron capture at n-TOF
The Photon Strength Function of 152Sm has been investigated at nTOF by studying the ¿-ray spectra from resonance neutron capture of 151Sm. The experimental apparatus consisted of two C6D6 liquid scintillator detectors. The measured spectra were compared with the predictions of the DICEBOX code, for different assumptions on the Photon Stregth Functions and on the Nuclear Level Density. For a meaningful comparison, the model calculations were filtered through a detailed software replica of the experimental apparatus, performed by means of three different Monte Carlo simulations. Preliminary results indicate that a reasonable reproduction of the experimental ¿-ray spectrum is obtained by postulating the presence of a Scissors Resonance. Some hints on the most suitable models, developed in the most recent studies of the Photon Strength Functions and Nuclear Level Density, are also obtained. © 2007 Sissa Medialab Srl. All rights reserved.Postprint (published version
Dinámica de sistemas para la selección de un sistema de pronóstico con base en el impacto de excesos y faltantes
This article studies the effect of the excesses and shortages in an organization, specifically in a product whose demand is growing. A system dynamics model was made through two diagrams two diagrams that are joined and related. In one of the diagrams is easy a sharing of forecast data, and in the main plot we can see the relations in the selection of a forecast with other components that are part of the organization. Based on all the relationships, we concluded about the impact of using three types of forecasts on finished goods inventory, safety stock, the level of service and the marginal utility of an organization.En el presente artÃculo se estudia el efecto de los excesos y faltantes en una organización, especÃficamente en un producto cuya demanda es creciente. Para facilitar el análisis, se realizó un modelo de dinámica de sistemas, compuesto de dos diagramas que posteriormente se relacionan. En uno de los diagramas se pueden intercambiar datos de los pronósticos, y en el diagrama principal se pueden observar las relaciones que tiene la selección de dicho pronóstico con otros aspectos que hacen parte de la organización. Su finalidad es conocer el impacto que genera el uso de tres tipos de pronósticos sobre el inventario de producto terminado, el inventario de seguridad, el nivel de servicio y la utilidad marginal de una organización
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