Changes in the benthic algal flora and vegetation of a semi-enclosed Mediterranean coastal lagoon (Stagnone di Marsala, Western Sicily)

È stato condotto uno studio sulla flora e vegetazione macroalgale dello Stagnone di Marsala (Trapani) con l’obiettivo di fornire una revisione dei dati riportati in letteratura ed esaminare i principali cambiamenti che si sono verificati nell’intera area negli ultimi tre decenni. La flora algale è risultata più povera rispetto al passato (94 taxa contro 108), mostrando un incremento delle Cloroficee e una riduzione delle Rodoficee e delle Feoficee. Solo 48 taxa sono stati riportati precedentemente, mentre 46 sono nuovi per lo Stagnone. Tra questi, è interessante sottolineare sia da un punto di vista floristico che ecologico, il ritrovamento per la prima volta dell’alga bruna Cystoseira compressa (Esper) Gerloff & Nizamuddin e delle alghe invasive Caulerpa cylindracea Sonder e Lophocladia lallemandii (Montagne) F. Schmitz. Al contrario, 60 taxa riportati precedentemente non sono stati trovati nel presente studio. In particolare, si annovera la scomparsa dell’alga verde Lamprothamnium papulosum (Wallroth) Groves e dell’alga bruna Cystoseira barbata (Stackhouse) C. Agardh f. aurantia (Kützing) Giaccone. L’elevato grado di confinamento e la natura del substrato sono stati i principali fattori che hanno influenzato il numero dei taxa e l’abbondanza delle comunità fitobentoniche, con valori massimi nelle stazioni caratterizzate da un buon ricambio idrico e/o dalla presenza di comunità dominate da Cystoseira. Nel presente studio vengono proposte alcune ipotesi per descrivere i cambiamenti nella composizione e struttura delle comunità fitobentoniche all’interno della laguna come conseguenza degli effetti del riscaldamento globale in atto negli ultimi anni.A study of the benthic macroalgal flora and vegetation of the Stagnone di Marsala (Trapani) has been performed in order to provide an up-to-date review of the status of and verify main changes that have occurred in the area over the past three decades. The flora of this study was poorer in taxa than that of literature (94 taxa against 108), with an increase in Chlorophyta and a decrease in Rhodophyta and Phaeophyceae. Only 48 taxa in the present flora have been previously reported, while 46 are new for the Stagnone. Among these, it was noteworthy, from both floristic and ecological point of view, the record for the first time of Cystoseira compressa (Esper) Gerloff & Nizamuddin and the invasive algae Caulerpa cylindracea Sonder and Lophocladia lallemandii (Montagne) F. Schmitz. On the contrary, 60 taxa previously reported have not been detected during the present study. Among these, Lamprothamnium papulosum (Wallroth) Groves and Cystoseira barbata (Stackhouse) C. Agardh f. aurantia (Kützing) Giaccone have been the most significant disappearances. High degree of confinement and sediment composition were the major factors affecting number of taxa and abundance of the phytobenthic communities, with maximum values in the stations characterized by a good water exchange and/or presence of Cystoseira assemblages. As a result of the effects of global warming over the past few years, noticeable changes in composition and structure of phytobenthic communities in the lagoon have been observed and some hypotheses of expected changes are here proposed

MICE: the Muon Ionization Cooling Experiment. Step I: First Measurement of Emittance with Particle Physics Detectors

The Muon Ionization Cooling Experiment (MICE) is a strategic R&D project intended to demonstrate the only practical solution to providing high brilliance beams necessary for a neutrino factory or muon collider. MICE is under development at the Rutherford Appleton Laboratory (RAL) in the United Kingdom. It comprises a dedicated beamline to generate a range of input muon emittances and momenta, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. The emittance of the incoming beam will be measured in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in Liquid Hydrogen (LH2) absorbers to RF cavity acceleration. A second spectrometer, identical to the first, and a second muon identification system will measure the outgoing emittance. In the 2010 run at RAL the muon beamline and most detectors were fully commissioned and a first measurement of the emittance of the muon beam with particle physics (time-of-flight) detectors was performed. The analysis of these data was recently completed and is discussed in this paper. Future steps for MICE, where beam emittance and emittance reduction (cooling) are to be measured with greater accuracy, are also presented

Measurement of the production of charged pions by protons on a tantalum target

A measurement of the double-differential cross-section for the production of charged pions in proton--tantalum collisions emitted at large angles from the incoming beam direction is presented. The data were taken in 2002 with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 \GeVc to 12 \GeVc hitting a tantalum target with a thickness of 5% of a nuclear interaction length. The angular and momentum range covered by the experiment (100 \MeVc \le p < 800 \MeVc and 0.35 \rad \le \theta <2.15 \rad) is of particular importance for the design of a neutrino factory. The produced particles were detected using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. Track recognition, momentum determination and particle identification were all performed based on the measurements made with the TPC. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections ${{\mathrm{d}^2 \sigma}} / {{\mathrm{d}p\mathrm{d}\theta}}$ at four incident proton beam momenta (3 \GeVc, 5 \GeVc, 8 \GeVc and 12 \GeVc). In addition, the pion yields within the acceptance of typical neutrino factory designs are shown as a function of beam momentum. The measurement of these yields within a single experiment eliminates most systematic errors in the comparison between rates at different beam momenta and between positive and negative pion production.Comment: 49 pages, 31 figures. Version accepted for publication on Eur. Phys. J.

Inclusive production of ρ0(770),f0(980)\rho^{0}(770), f_0(980) and f2(1270)f_2(1270) mesons in νμ\nu_{\mu} charged current interactions

The inclusive production of the meson resonances $\rho^{0}(770)$, $f_0(980)$ and $f_2(1270)$ in neutrino-nucleus charged current interactions has been studied with the NOMAD detector exposed to the wide band neutrino beam generated by 450 GeV protons at the CERN SPS. For the first time the $f_{0}(980)$ meson is observed in neutrino interactions. The statistical significance of its observation is 6 standard deviations. The presence of $f_{2}(1270)$ in neutrino interactions is reliably established. The average multiplicity of these three resonances is measured as a function of several kinematic variables. The experimental results are compared to the multiplicities obtained from a simulation based on the Lund model. In addition, the average multiplicity of $\rho^{0}(770)$ in antineutrino - nucleus interactions is measured.Comment: 23 pages, 14 figures, 8 tables. To appear in Nucl. Phys.

Search for the exotic Θ+\Theta^+ resonance in the NOMAD experiment

A search for exotic Theta baryon via Theta -> proton +Ks decay mode in the NOMAD muon neutrino DIS data is reported. The special background generation procedure was developed. The proton identification criteria are tuned to maximize the sensitivity to the Theta signal as a function of xF which allows to study the Theta production mechanism. We do not observe any evidence for the Theta state in the NOMAD data. We provide an upper limit on Theta production rate at 90% CL as 2.13 per 1000 of neutrino interactions.Comment: Accepted to European Physics Journal

Search for heavy neutrinos mixing with tau neutrinos

We report on a search for heavy neutrinos (\nus) produced in the decay D_s\to \tau \nus at the SPS proton target followed by the decay \nudecay in the NOMAD detector. Both decays are expected to occur if \nus is a component of $\nu_{\tau}$.\ From the analysis of the data collected during the 1996-1998 runs with $4.1\times10^{19}$ protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the \nus mass range from 10 to 190 $\rm MeV$. Windows between the SN1987a and Big Bang Nucleosynthesis lower limits and our result are still open for future experimental searches. The results obtained are used to constrain an interpretation of the time anomaly observed in the KARMEN1 detector.\Comment: 20 pages, 7 figures, a few comments adde

Characterisation of the muon beams for the Muon Ionisation Cooling Experiment

A novel single-particle technique to measure emittance has been developed and used to characterise seventeen different muon beams for the Muon Ionisation Cooling Experiment (MICE). The muon beams, whose mean momenta vary from 171 to 281 MeV/c, have emittances of approximately 1.2–2.3 π mm-rad horizontally and 0.6–1.0 π mm-rad vertically, a horizontal dispersion of 90–190 mm and momentum spreads of about 25 MeV/c. There is reasonable agreement between the measured parameters of the beams and the results of simulations. The beams are found to meet the requirements of MICE

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +c¯¯)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−s¯¯¯ quark asymmetry