A high-resolution tracking hodoscope based on capillary layers filled with liquid scintillator

Results are given on tests of a high-resolution tracking hodoscope based on layers of \hbox{26-$\mu$m-bore} glass capillaries filled with organic liquid scintillator (1-methylnaphthalene doped with R39). The detector prototype consisted of three 2-mm-thick parallel layers, with surface areas of $2.1 \times 21$~cm$^2$. The layers had a centre-to-centre spacing of 6~mm, and were read by an optoelectronic chain comprising two electrostatically focused image intensifiers and an Electron-Bombarded Charge-Coupled Device (EBCCD). Tracks of cosmic-ray particles were recorded and analysed. The observed hit density was 6.6~hits/mm for particles crossing the layers perpendicularly, at a distance of 1~cm from the capillaries' readout end, and 4.2~hits/mm for particles at a distance of 20~cm. A track segment reconstructed in a single layer had an rms residual of $\sim$~20~$\mu$m, and allowed determination of the track position in a neighbouring layer with a precision of $\sim$~170~$\mu$m. This latter value corresponded to an rms angular resolution per layer of about 30~mrad. A comparison is made between capillary layers and silicon microstrip planes

Leading order analysis of neutrino induced dimuon events in the CHORUS experiment

We present a leading order QCD analysis of a sample of neutrino induced charged-current events with two muons in the final state originating in the lead-scintillating fibre calorimeter of the CHORUS detector. The results are based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign dimuon events collected during the exposure of the detector to the CERN Wide Band Neutrino Beam between 1995 and 1998. % with $E_{\mu 1},E_{\mu 2} > 5$ GeV and $Q^2 > 3$ GeV$^2$ collected %between 1995 and 1998. The analysis yields a value of the charm quark mass of \mc = (1.26\pm 0.16 \pm 0.09) \GeVcc and a value of the ratio of the strange to non-strange sea in the nucleon of $\kappa = 0.33 \pm 0.05 \pm 0.05$, improving the results obtained in similar analyses by previous experiments.Comment: Submitted to Nuclear Physics

Crayfish Recognize the Faces of Fight Opponents

The capacity to associate stimuli underlies many cognitive abilities, including recognition, in humans and other animals. Vertebrates process different categories of information separately and then reassemble the distilled information for unique identification, storage and recall. Invertebrates have fewer neural networks and fewer neural processing options so study of their behavior may reveal underlying mechanisms still not fully understood for any animal. Some invertebrates form complex social colonies and are capable of visual memory–bees and wasps, for example. This ability would not be predicted in species that interact in random pairs without strong social cohesion; for example, crayfish. They have chemical memory but the extent to which they remember visual features is unknown. Here we demonstrate that the crayfish Cherax destructor is capable of visual recognition of individuals. The simplicity of their interactions allowed us to examine the behavior and some characteristics of the visual features involved. We showed that facial features are learned during face-to-face fights, that highly variable cues are used, that the type of variability is important, and that the learning is context-dependent. We also tested whether it is possible to engineer false identifications and for animals to distinguish between twin opponents

Measurement of charm production in neutrino charged-current interactions

The nuclear emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy from 1994 to 1997. In total about 100000 charged-current neutrino interactions with at least one identified muon were located in the emulsion target and fully reconstructed, using newly developed automated scanning systems. Charmed particles were searched for by a program recognizing particle decays. The observation of the decay in nuclear emulsion makes it possible to select a sample with very low background and minimal kinematical bias. 2013 charged-current interactions with a charmed hadron candidate in the final state were selected and confirmed through visual inspection. The charm production rate induced by neutrinos relative to the charged-current cross-section is measured to be sigma(nu_mu N -> mu- C X)/sigma(CC) = (5.75 +-0.32 stat +-0.30 syst)%. The charm production cross-section as a function of the neutrino energy is also obtained. The results are in good agreement with previous measurements. The charm-quark hadronization produces the following charmed hadrons with relative fractions (in %): f_Dzero = 43.7+-4.5, f_Lambda_c^plus = 19.2+-4.2, f_Dplus = 25.3+-4.2, and f_D_splus = 11.8+-4.7.Comment: 16 pages, 5 figure

Observation of weak neutral current neutrino production of J/ψJ/\psi

Observation of \jpsi production by neutrinos in the calorimeter of the CHORUS detector exposed to the CERN SPS wide-band \numu beam is reported. A spectrum-averaged cross-section $\sigma^{\mathrm{J/\psi}}$ = (6.3 $\pm$ 3.0) $\times \mathrm{10^{-41}~cm^{2}}$ is obtained for 20 GeV $\leq E_{\nu} \leq$ 200 GeV. The data are compared with the theoretical model based on the QCD Z-gluon fusion mechanism

The CHARON detector: An emulsion / counter hybrid set-up to measure the mean free path of near-elastic pion scattering in nuclear emulsion (white kink) at 2-GeV/c, 3-GeV/c and 5-GeV/c

White and grey kink events define a special class of soft hadron interactions in nuclear emulsion in which only one track (the scattered hadron) is leaving the interaction vertex. Due to their small and sometimes invisible activity at the scattering point, they represent a potential background source for all emulsion experiments hunting for decay topologies of short-lived particles like the lepton and charm mesons. For an extensive study of such hadronic kink signatures a dedicated experimental set-up has been built and exposed at the CERN PS hadron beam facility and it has collected about 300000 pions with a fixed momentum ranging from 2 to 5 GeV/c. Each particle was tracked by silicon strip detectors to connect it to the proper track in the nuclear emulsion located in between. Threshold Cherenkov detectors for electron discrimination, a muon counter and an MWPC- based magnetic spectrometer completed the experimental configuration. A total of 222 white and 271 grey kinks could be successfully located in the emulsion target. Their angular and transverse momentum distributions were extensively studied. (15 refs)

A high-resolution tracking hodoscope based on capillary layers filled with liquid scintillator

Results are given on tests of a high-resolution tracking hodoscope based on layers of 26-mum-bore glass capillaries filled with organic liquid scintillator (1-methylnaphthalene doped with R39). The detector prototype consisted of three 2-mm-thick parallel layers, with surface areas of 3.1 x 21 cm(2). The layers had a centre-to-centre spacing of 6 mm, and were read by an optoelectronic chain comprising two electrostatically focused image intensifiers and an Electron-Bombarded Charge-Coupled Device (EBCCD). Tracks of cosmic-ray particles were recorded and analysed. The observed hit density was 6.6 hits/mm for particles crossing the layers perpendicularly, at a distance of 1 cm from the capillaries' readout end, and 4.2 hits/mm for particles at a distance of 20 cm, A track segment reconstructed in a single layer had an rms residual of 20 mum, and allowed determination of the track position in a neighbouring layer with a precision of similar to 170 mum. This latter value corresponded to an rms angular resolution per layer of about 30 mrad, A comparison is made between capillary layers and silicon microstrip planes. (C) 2001 Elsevier Science B.V. All rights reserved