Experimental study of quasi-elastic neutrino interactions on Ar with a liquid Ar TPC exposed to the WANF neutrino beam

We present results from the first exposure of a liquid Ar time projection chamber to a neutrino beam. The data have been collected in 1997 with a 50 liter ICARUS-like chamber located between the CHORUS and NOMAD experiment at the CERN West Area Neutrino Facility. We focus on the analysis of quasi-elastic interactions; despite the limited size of the detector, nuclear effects beyond Fermi motion and Pauli blocking have been observed as perturbations to the pure quasi-elastic kinematics.Comment: 6 pages, 4 figures, prepared for the proceedings of NuInt0

Three-Flavour Neutrino-Mixing Implications of the LSND Result

The LSND result is shown to fit into a minimal three-flavour neutrino-mixing scenario capable of describing all known experimental facts provided the large Delta M^2 = m_3^2 - m_2^2 \sim m_3^2 - m_1^2 lies in the range 2.5 x 10^{-1} < Delta M^2 < 3.0 eV^2. In this range the value of P_{\mu\tau} is expected to be about 5% or larger.Comment: 10 pages, 2 eps figures, LaTeX 2.09, revised for Physics Letters

Atmospheric neutrino data : Active-Active ×\times Active-Sterile oscillations

I summarize here the results of a global fit to the full data set corresponding to 33.0 kt-yr of data of the Super-Kamiokande experiment as well as to all other experiments in order to compare the active-active and active-sterile neutrinos oscillation channels to the atmospheric neutrino anomaly.Comment: 3 pages, uses espcrc2.sty (Nuclear Physics style) and epsfig.sty, 2 PS files. To appear in the Proceedings of the XTH Int. Symposium on Very High Energy Cosmic Ray Interactions, Laboratory Nazionali del Gran Sasso, Assergi, Italy, July 12-17 199

New limits on radiative sterile neutrino decays from a search for single photons in neutrino interactions

It has been recently shown that excess events observed by the LSND and MiniBooNE neutrino experiments could be interpreted as a signal from the radiative decay of a heavy sterile neutrino \nu_h produced in \nu_\mu neutral current-like interactions. If the \nu_h exist, it would be also produced by the \nu_\mu beam from the CERN SPS in the neutrino beam line shielding. The \nu_h's would penetrate the shielding and be observed through the decay \nu_h -> \nu \gamma, followed by the photon conversion into e+e- pair in the active target of the NOMAD detector. The \nu_h's could be also produced in the iron of the magnetic spectrometer of the CHORUS detector, located just in front of NOMAD. Considering these two sources of \nu_h's we set new constraints on \nu_h properties and exclude part of the LSND/MiniBooNE \nu_h parameter space using bounds on single photons production in neutrino reactions recently reported by the NOMAD collaboration. We find that broad bands in the parameter space are still open for more sensitive searches for the \nu_h in future neutrino experiments.Comment: 10 pages, 5 figures. Revised version to appear in PLB. Discussion of dominant NC-like production of \nu_h's adde

Charmonium production at neutrino factories

At existing and planned neutrino factories (high energy and high intensity neutrino beam facilities) precision studies of QCD in neutrino-nucleon interactions are a realistic opportunity. We investigate charmonium production in fixed target neutrino experiments. We find that $J/\psi$ production in neutrino-nucleon collision is dominated by the color octet $^3S_1$ NRQCD matrix element in a neutral current process, which is not accessible in photo or leptoproduction. Neutrino experiments at a future Muon Collider will acquire sufficient event rate to accurately measure color octet matrix element contributions. The currently running high energy neutrino experiments, NOMAD and NuTeV could also observe several such events.Comment: 13 pages Latex, with five embedded eps figures. Cosmetic fixups in the figures, otherwise unchange

Emulsion Chamber with Big Radiation Length for Detecting Neutrino Oscillations

A conceptual scheme of a hybrid-emulsion spectrometer for investigating various channels of neutrino oscillations is proposed. The design emphasizes detection of $\tau$ leptons by detached vertices, reliable identification of electrons, and good spectrometry for all charged particles and photons. A distributed target is formed by layers of low-Z material, emulsion-plastic-emulsion sheets, and air gaps in which $\tau$ decays are detected. The tracks of charged secondaries, including electrons, are momentum-analyzed by curvature in magnetic field using hits in successive thin layers of emulsion. The $\tau$ leptons are efficiently detected in all major decay channels, including \xedec. Performance of a model spectrometer, that contains 3 tons of nuclear emulsion and 20 tons of passive material, is estimated for different experimental environments. When irradiated by the $\nu_\mu$ beam of a proton accelerator over a medium baseline of $\sim 1$ km/GeV, the spectrometer will efficiently detect either the \omutau and \omue transitions in the mass-difference region of $\Delta m^2 \sim 1$ eV$^2$, as suggested by the results of LSND. When exposed to the neutrino beam of a muon storage ring over a long baseline of $\sim$ 10-20 km/GeV, the model detector will efficiently probe the entire pattern of neutrino oscillations in the region $\Delta m^2 \sim 10^{-2}-10^{-3}$ eV$^2$, as suggested by the data on atmospheric neutrinos.Comment: 34 pages, 8 figure

Detecting the (Quasi-)Two-Body Decays of τ\tau Leptons in Short-Baseline Neutrino Oscillation Experiments

Novel detector schemes are proposed for the short-baseline neutrino experiments of next generation, aimed at exploring the large-$\Delta m^2$ domain of \omutau oscillations in the appearance mode. These schemes emphasize good spectrometry for charged particles and for electromagnetic showers and efficient reconstruction of \ypi_gg decays. The basic elements are a sequence of relatively thin emulsion targets, immersed in magnetic field and interspersed with electronic trackers, and a fine-grained electromagnetic calorimeter built of lead glass. These elements act as an integral whole in reconstructing the electromagnetic showers. This conceptual scheme shows good performance in identifying the $\tau$ (quasi-)two-body decays by their characteristic kinematics and in selecting the electronic decays of the $\tau$.Comment: 34 pages, 8 figure

The muon anomalous magnetic moment and a new light gauge boson

It is shown that the 2.6 $\sigma$ discrepancy between the predicted and recently measured value of the anomalous magnetic moment of positive muons could be explained by the existence of a new light gauge boson X with a mass $M_X \leq O(5) GeV$. Phenomenological bounds on the X coupling are discussed.Comment: 7 pages, version to appear in PL

Cross-section measurements in the NOMAD experiment

The NOMAD experiment collected valuable neutrino data samples, matching both the large statistics of massive calorimeters and the reconstruction quality of bubble chambers. This paper describes the recent measurements of neutrino cross-sections on carbon target. The approach followed for cross-section modeling is also explained.Comment: Proceedings of the NuInt05 conference, Okayama September 200

Structural and functional studies on the homeostasis and type-III-secretion of flagellin

The ability to move towards favorable and avoid unfavorable conditions is key to the survival of many bacterial species. Bacterial movement relies on a sophisticated nanomachine, the flagellum. Despite being one of the tiniest motors in the biosphere, the flagellum exhibits a complex architecture and is composed of more than 30 different proteins in diverse stoichiometries. Flagellar architecture can be subdivided into a membrane-embedded basal body, a hook and a long helical filament. The process of flagellar assembly involves a plethora of accessory factors and is organized at different stages on the transcriptional, post-transcriptional and translational level. Furthermore, biogenesis of a flagellum is strictly sequential and requires the completion of a building phase prior to initiating the next one. The most abundant constituent within a flagellum is the protein flagellin that assembles into a helical filament with more than 20.000 monomers. The two proteins CsrA and FliW regulate flagellin homeostasis via a posttranscriptional mechanism only allowing flagellin translation when cytoplasmic levels are low, thereby ensuring that flagellin is directly secreted after production. A third protein, the intrinsic chaperone FliS is essential for the recognition and efficient secretion of flagellin. Together these proteins couple translation to secretion of flagellin and keep cytoplasmic flagellin concentrations around a low and narrow threshold. This work aims at unraveling the molecular mechanisms by which the above-named proteins regulate flagellin homeostasis. In enterobacteria CsrA activity is antagonized by small non-coding RNAs (sRNAs) that act as competitive inhibitors. Conversely, the FliW protein allosterically controls CsrA in a variety of flagellated bacteria, which seems to represent the ancestral state of CsrA regulation. This work furthermore demonstrates that interaction of FliW and flagellin seems to be cotranslational or strongly associated with translating ribosomes, therefore coupling homeostasis and secretion. Another level of regulation elucidated in this study is the influence of bactofilins on the process of flagellar biogenesis. This ubiquitous class of proteins is reminiscent of cytoskeleton factors but seems to rather provide a dynamic scaffold for diverse processes. In B. subtilis the bactofilins BacE and BacF are involved in flagellar assembly at the stage of hook-completion but BacE also directly interacts with FliW. Finally, this work includes a model explaining the coupling of homeostasis and secretion of flagellin at atomic resolution