308 research outputs found

    Large-angle scattering of multi-GeV muons on thin Lead targets

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    The probability of large-angle scattering for multi-GeV muons in thin (t/X0∌10−1t/X_0 \sim 10^{-1}) lead targets is studied. The new estimates presented here are based both on simulation programs (GEANT4 libraries) and theoretical calculations. In order to validate the results provided by simulation, a comparison is drawn with experimental data from the literature. This study is particularly relevant when applied to muons originating from ΜΌCC\nu_\mu^{CC} interactions of CNGS beam neutrinos. In that circumstance the process under study represents the main background for the ΜΌ→Μτ\nu_\mu \to \nu_\tau search in the τ→Ό\tau \to \mu channel for the OPERA experiment at LNGS. Finally, we also investigate, in the CNGS context, possible contributions from the muon photo-nuclear process which might in principle also produce a large-angle muon scattering signature in the detector

    A compact light readout system for longitudinally segmented shashlik calorimeters

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    The longitudinal segmentation of shashlik calorimeters is challenged by dead zones and non-uniformities introduced by the light collection and readout system. This limitation can be overcome by direct fiber-photosensor coupling, avoiding routing and bundling of the wavelength shifter fibers and embedding ultra-compact photosensors (SiPMs) in the bulk of the calorimeter. We present the first experimental test of this readout scheme performed at the CERN PS-T9 beamline in 2015 with negative particles in the 1-5~GeV energy range. In this paper, we demonstrate that the scheme does not compromise the energy resolution and linearity compared with standard light collection and readout systems. In addition, we study the performance of the calorimeter for partially contained charged hadrons to assess the e/πe/\pi separation capability and the response of the photosensors to direct ionization.Comment: To appear in Nuclear Instruments and Methods in Physics Research,


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    Apomixis (asexual reproduction through seeds) is considered a deviation of the sexual reproductive pathway leading to the formation of clonal progenies genetically identical to the mother plant. It has been suggested that apomixis might be a consequence of epigenetic alterations, such as interspecific hybridization and polyploidization, resulting in a wide deregulation of reproductive development. Studies on epigenetic are transforming our actual idea of the structural variation and diversity that prevails at key steps of plant female gametogenesis, with deep implications for understanding the evolutionary trends that model innovation in reproductive development and adaptation. Recent results have provided evidences indicating that epigenetic mechanisms are crucial to control events that distinguish sexual from apomictic development. Therefore, the epigenetic regulation of apomixis is an attractive theory as it potentially accounts for the facultative nature of apomixis as well as the ability of apomictic to revert back to sexuality. In this work we used the Methylation-Sensitive Amplification Polymorphism (MSAP) technique to characterize floral genome cytosine methylation patterns occurring in sexual and aposporous Paspalum notatum genotypes, in order to identify epigenetically-controlled genes putatively involved in apomixis development. A partial and rather divergent methylation reprogramming was detected in apomictic genotypes. From twelve polymorphic MSAP-derived sequences, one (PN_6.6, renamed PN_SCD1) was selected due to its relevant annotation and differential representation in 454 floral transcriptome libraries of sexual and apomictic P. notatum. PN_6.6 encodes the DENN domain/WD repeat-containing protein SCD1, which interacts with RAB GTPases- and/or MAPKs to promote specialized cell division, functions in clathrin-mediated membrane transport and was defined as potential substrate receptor of CUL4 E3 ubiquitin ligases. Quantitative RT-PCR and comparative RNAseq analyses of laser microdissected nucellar cells confirmed PN_SCD1 upregulation in florets of apomictic plants and revealed that overexpression takes place just before the onset of apospory initials. Moreover, we found that several SCD1 molecular partners are upregulated in florets of P. notatum apomictic plants. Our results revealed a specific vesicle trafficking molecular pathway epigenetically modulated during apomixis. Results will be presented and critically discussed

    A narrow band neutrino beam with high precision flux measurements

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    The ENUBET facility is a proposed narrow band neutrino beam where lepton production is monitored at single particle level in the instrumented decay tunnel. This facility addresses simultaneously the two most important challenges for the next generation of cross section experiments: a superior control of the flux and flavor composition at source and a high level of tunability and precision in the selection of the energy of the outcoming neutrinos. We report here the latest results in the development and test of the instrumentation for the decay tunnel. Special emphasis is given to irradiation tests of the photo-sensors performed at INFN-LNL and CERN in 2017 and to the first application of polysiloxane-based scintillators in high energy physics.Comment: Poster presented at NuPhys2017 (London, 20-22 December 2017). 5 pages, 2 figure

    The ENUBET Beamline

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    The ENUBET ERC project (2016-2021) is studying a narrow band neutrino beam where lepton production can be monitored at single particle level in an instrumented decay tunnel. This would allow to measure ΜΌ\nu_{\mu} and Μe\nu_{e} cross sections with a precision improved by about one order of magnitude compared to present results. In this proceeding we describe a first realistic design of the hadron beamline based on a dipole coupled to a pair of quadrupole triplets along with the optimisation guidelines and the results of a simulation based on G4beamline. A static focusing design, though less efficient than a horn-based solution, results several times more efficient than originally expected. It works with slow proton extractions reducing drastically pile-up effects in the decay tunnel and it paves the way towards a time-tagged neutrino beam. On the other hand a horn-based transferline would ensure higher yields at the tunnel entrance. The first studies conducted at CERN to implement the synchronization between a few ms proton extraction and a horn pulse of 2-10 ms are also described.Comment: Poster presented at NuPhys2018 (London 19-21 December 2018). 4 pages, 3 figure

    NEWS: Nuclear emulsion WIMP search

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    The most convincing candidate as main constituent of the dark matter in the Universe consists of Weakly Interacting Massive Particles (WIMPs). WIMPs must be electrically neutral and interact with a very low cross-section (σ < 10 −40 cm2) which makes them detectable in direct searches only through the observation of nuclear recoils induced by the WIMP rare scatterings. In the experiments carried out so far, recoiled nuclei are searched for as a signal over a background produced by Compton electrons and neutron scatterings. Signal found by some experiments have not been confirmed by other techniques. We propose an R&D program for a new experimental method able to observe the track of the scattered nucleus based on new developments in the nuclear emulsion technique. Nuclear emulsions would act both as the WIMP target and as the tracking detector able to reconstruct the direction of the recoiled nucleus. This unique characteristic would provide a new and unambiguous signature of the presence of the dark matter in our galaxy

    Limited impacts of experimental flow releases on water quality and macroinvertebrate community composition in an upland regulated river

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    River regulation following the construction of dams has affected the hydrology, water quality, and biology of watercourses across the globe. The term “environmental flows” has been used to describe measures that can be employed to return some lost elements of the natural flow regime. Their introduction has been suggested as a way to mitigate the impacts of river regulation throughout the world, but understanding of the effects of artificial high flows on water quality and biota is limited for many different river types. We report a field study that manipulated compensation flows from reservoirs in the Pennine uplands of northern England and measured changes in water quality and benthic macroinvertebrates using a before‐after‐control‐impact approach. These resulted in minor short‐term changes in water quality, but there was no evidence of immediate (within 48 hr) responses by the macroinvertebrate community to individual flow releases. However, a shift in macroinvertebrate community composition was found after multiple releases, characterized by reductions in Amphinemura sulcicollis (Plecoptera) and Baetis rhodani (Ephemeroptera) and changes in the density of all Diptera. The introduction of short‐term flow pulses in flashy regulated river systems is unlikely to yield significant changes in water quality and biota. Nevertheless, cumulative rather than single environmental flow events show promise for mitigating some of the impacts of river regulation. More widely, our findings indicate that environmental flow releases from reservoirs may have to go beyond occasional experimental high flow releases if these rivers are to more closely mimic unregulated river systems