91193621
Some expected rates of electron backgrounds for LEP13
120136815
A lead-glass cherenkov detector for electrons and photons
Abstract An apparatus for the detection of high-energy electrons and photons is described. Lead-glass Cherenkov counters measure the energies, and charged particle tracks are reconstructed using an array of wire spark chambers. The mode of operation, calibration, and stability of the system are described, and details are given of the ability to discriminate electrons from hadrons.
115544175
Estimated rates for electron backgrounds at LEP
120618738
Observation of high mass electron-positron pairs produced in proton-proton collisions at the CERN ISR
Abstract In an experiment performed at the CERN Intersecting Storage Rings (ISR), 11 e + e − pairs of high invariant mass value (> 2.5 GeV/c 2 ) have been observed. Of these events, 9 can be interpreted as arising from the reaction p + p → J (3.1) + anything. the cross-section for this reaction is estimated and compared with the result obtained at lower centre-of-mass energies.
117328126
Estimates for the rates of off momentum electrons to be expected in LEP
120272757
A System of Cylindrical Drift Chambers in a Superconducting Solenoid
Abstract A superconducting solenoid at the CERN ISR has been equipped with a system of high accuracy cylindrical drift chambers. This detector consists of eight layers of field shaped drift cells with a delay line opposite each sense wire to provide coupled two dimensional readout. The design, construction, and operation of this system are discussed. The resolution and performance of the delay lines and sense wires under ISR running conditions are shown.
20742679
Galaxy Zoo: an independent look at the evolution of the bar fraction over the last eight billion years from HST-COSMOS ?
We measure the redshift evolution of the bar fraction in a sample of 2380 visually selected disc galaxies found in Cosmic Evolution Survey (COSMOS) Hubble Space Telescope (HST ) images. The visual classications used both to identify the disc sample and to indicate the presence of stellar bars were provided by citizen scientists via the Galaxy Zoo: Hubble (GZH) project. We nd that the overall bar fraction decreases by a factor of 2, from 22 5% at z = 0:4 (tlb = 4:2 Gyr) to 11 2% at z = 1:0 (tlb = 7:8 Gyr), consistent with previous analysis. We show that this decrease, of the strong bar fraction in a volume limited sample of massive disc galaxies [stellar mass limit of log(M?=M ) 10:0], cannot be due to redshift-dependent biases hiding either bars or disc galaxies at higher redshifts. Splitting our sample into three bins of mass we nd that the decrease in bar fraction is most prominent in the highest mass bin, while the lower mass discs in our sample show a more modest evolution. We also include a sample of 98 red disc galaxies. These galaxies have a high bar fraction (45 5%), and are missing from other COSMOS samples which used SED tting or colours to identify high redshift discs. Our results are consistent with a picture in which the evolution of massive disc galaxies begins to be aected by slow (secular) internal process at z 1. We discuss possible connections of the decrease in bar fraction to the redshift, including the growth of stable disc galaxies, mass evolution of the gas content in disc galaxies, as well as the mass-dependent eects of tidal interactions.
120145716
The response of air shower arrays to air showers
Abstract The air shower that is measured and analysed by an air shower experiment is not, in general, an unprejudiced derivative of the data. Biases of many kinds are present in these experiments and they can significantly modify the interpretation of the results if not eliminated.
129617632
The Durham Extensive Air Shower Array
7049031
Small-scale structure in the interstellar medium: time-varying interstellar absorption towards κ Velorum
Ultra-high spectral resolution observations of time-varying interstellar absorption towards κ Vel are reported, using the Ultra-High Resolution Facility on the Anglo-Australian Telescope. Detections of interstellar Ca i, Ca ii, K i, Na i and CH are obtained, whilst an upper limit on the column density is reported for C_2. The results show continued increases in column densities of K i and Ca i since observations ∼4 yr earlier, as the transverse motion of the star carried it ∼10 au perpendicular to the line of sight. Line profile models are fitted to the spectra and two main narrow components (A and B) are identified for all species except CH. The column density N(K i) is found to have increased by 82^(+10)_(−9) per cent between 1994 and 2006, whilst N(Ca i) is found to have increased by 32 ± 5 per cent over the shorter period of 2002–2006. The line widths are used to constrain the kinetic temperature to T_(k,A) < 671^(+18)_(−17) K and T_(k,B) < 114^(+15)_(−14) K. Electron densities are determined from the Ca i/Ca ii ratio, which in turn place lower limits on the total number density of n_A ≳ 7 × 10^3 cm^(−3) and n_B ≳ 2 × 10^4 cm^(−3). Calcium depletions are estimated from the Ca i/K i ratio. Comparison with the chemical models of Bell et al. confirms the high number density, with n = 5 × 10^4 cm^(−3) for the best-fitting model. The first measurements of diffuse interstellar bands (DIBs) towards this star are made at two epochs, but only an upper limit of ≲ 40 per cent is placed on their variation over ∼9 yr. The DIBs are unusually weak for the measured E(B − V) and appear to exhibit similar behaviour to that seen in Orion. The ratio of equivalent widths of the λ5780 to λ5797 DIBs is amongst the highest known, which may indicate that the carrier of λ5797 is more sensitive to ultraviolet radiation than to local density.
119221732
The Impact of Assuming Flatness in the Determination of Neutrino Properties from Cosmological Data
Cosmological data have provided new constraints on the number of neutrino species and the neutrino mass. However these constraints depend on assumptions related to the underlying cosmology. Since a correlation is expected between the number of effective neutrinos N_{eff}, the neutrino mass \sum m_\nu, and the curvature of the universe \Omega_k, it is useful to investigate the current constraints in the framework of a non-flat universe. In this paper we update the constraints on neutrino parameters by making use of the latest cosmic microwave background (CMB) data from the ACT and SPT experiments and consider the possibility of a universe with non-zero curvature. We first place new constraints on N_{eff} and \Omega_k, with N_{eff} = 4.03 +/- 0.45 and 10^3 \Omega_k = -4.46 +/- 5.24. Thus, even when \Omega_k is allowed to vary, N_{eff} = 3 is still disfavored with 95% confidence. We then investigate the correlation between neutrino mass and curvature that shifts the 95% upper limit of \sum m_\nu < 0.45 eV to \sum m_\nu < 0.95 eV. Thus, the impact of assuming flatness in neutrino cosmology is significant and an essential consideration with future experiments.