Measurements of the Rate Capability of Various Resistive Plate Chambers

Resistive Plate Chambers (RPCs) exhibit a significant loss of efficiency for the detection of particles, when subjected to high particle fluxes. This rate limitation is related to the usually high resistivity of the resistive plates used in their construction. This paper reports on measurements of the performance of three different glass RPC designs featuring a different total resistance of the resistive plates. The measurements were performed with 120 GeV protons at varying beam intensitie

Radiation-Hardness Measurements of High OH−OH^{-} Content Quartz Fibres Irradiated with 24 GeV Protons up to 1.25 Grad

We investigated the darkening of two high OH- content quartz fibres irradiated with 24 GeV protons at the Cern PS facility IRRAD. The two tested fibres have a 0.6 mm quartz core diameter, one with hard plastic cladding (qp) and the other with quartz cladding (qq). These fibres were exposed at about 1.25 Gigarad in 3 weeks. The fibres became opaque below 380nm, and in the range 580-650 nm. The darkening under irradiation and damage recovery after irradiation as a function of dose and time are similar to what we observed with electrons. The typical attenuation at 455 nm are 1.44 + - 0.22 and 2.20 + - 0.15 dB/m at 100 Mrad for qp and qq fibres, respectively. The maximum damage recovery is also observed near this wavelength

An intercomparison of CH3O2 measurements by Fluorescence Assay by Gas Expansion and Cavity Ring–Down Spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

Simultaneous measurements of CH3O2 radical concentrations have been performed using two different methods in the Leeds HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) chamber at 295 K and in 80 mbar of a mixture of 3 : 1 He : O2 and 100 mbar or 1000 mbar of synthetic air. The first detection method consisted of the indirect detection of CH3O2 using the conversion of CH3O2 into CH3O by excess NO with subsequent detection of CH3O by fluorescence assay by gas expansion (FAGE). The FAGE instrument was calibrated for CH3O2 in two ways. In the first method, a known concentration of CH3O2 was generated using the 185 nm photolysis of water vapour in synthetic air at atmospheric pressure followed by the conversion of the generated OH radicals to CH3O2 by reaction with CH4 / O2. This calibration can be used for experiments performed in HIRAC at 1000 mbar in air. In the second method, calibration was achieved by generating a near steady-state of CH3O2 and then switching off the photolysis lamps within HIRAC and monitoring the subsequent decay of CH3O2 which was controlled via its self-reaction, and analysing the decay using second order kinetics. This calibration could be used for experiments performed at all pressures. In the second detection method, CH3O2 has been measured directly using Cavity Ring-Down Spectroscopy (CRDS) using the absorption at 7487.98 cm-1 in the A <– X (ν12) band with the optical path along the ~1.4 m chamber diameter. Analysis of the second-order kinetic decays of CH3O2 by self-reaction monitored by CRDS has been used for the determination of the CH3O2 absorption cross section at 7487.98 cm-1, both at 100 mbar of air and at 80 mbar of a 3 : 1 He : O2 mixture, from which σCH3O2 = (1.49 ± 0.19) × 10–20 cm2 molecule-1 was determined for both pressures. The absorption spectrum of CH3O2 between 7486 and 7491 cm-1 did not change shape when the total pressure was increased to 1000 mbar, from which we determined that σCH3O2 is independent of pressure over the pressure range 100–1000 mbar in air. CH3O2 was generated in HIRAC using either the photolysis of Cl2 with UV black lamps in the presence of CH4 and O2 or the photolysis of acetone at 254 nm in the presence of O2. At 1000 mbar of synthetic air the correlation plot of [CH3O2]FAGE against [CH3O2]CRDS gave a gradient of 1.10 ± 0.02. At 100 mbar of synthetic air the gradient of the FAGE – CRDS correlation plot had a gradient of 1.06 ± 0.01 and at 80 mbar of 3 : 1 He : O2 mixture the correlation plot gradient was 0.91 ± 0.02. These results provide a validation of the FAGE method to determine concentrations of CH3O2

Validation of the lupus nephritis clinical indices in childhood-onset systemic lupus erythematosus

OBJECTIVE: To validate clinical indices of lupus nephritis (LN) activity and damage when used in children against the criterion standard of kidney biopsy findings. METHODS: In 83 children requiring kidney biopsy the SLE Disease Activity Index Renal Domain (SLEDAI-R); British Isles Lupus Assessment Group index Renal Domain (BILAG-R), Systemic Lupus International Collaborating Clinics Renal Activity (SLICC-RAS) and Damage Index Renal Domain (SDI-R) were measured. Fixed effect and logistic models were done to predict International Society of Nephrology/Renal Pathology Society (ISN/RPS) class; low/moderate vs. high LN-activity [NIH Activity Index (NIH-AI) score:10; Tubulointerstitial Activity Index (TIAI) score:5) or the absence vs. presence of LN chronicity [NIH Chronicity Index (NIH-CI) score: 0 vs. \u3e/= 1]. RESULTS: There were 10, 50 and 23 patients with class I/II, III/IV and V, respectively. Scores of the clinical indices did not differentiate among patients by ISN/RPS class. The SLEDAI-R and SLICC-RAS but not the BILAG-R differed with LN-activity status defined by NIH-AI scores, while only the SLEDAI-R scores differed between LN-activity status based on TIAI scores. The sensitivity and specificity of the SDI-R to capture LN chronicity was 23.5% and 91.7%, respectively. Despite designed to measure LN-activity, SLICC-RAS and SLEDAI-R scores significantly differed with LN chronicity status. CONCLUSION: Current clinical indices of LN fail to discriminate ISN/RPS Class in children. Despite its shortcomings, the SLEDAI-R appears to best for measuring LN activity in a clinical setting. The SDI-R is a poor correlate of LN chronicity. This article is protected by copyright. All rights reserved

Spin-Splitter Studies: Polarization Stability Measurements at IUCF

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Forward Neutron Production at the Fermilab Main Injector

We have measured cross sections for forward neutron production from a variety of targets using proton beams from the Fermilab Main Injector. Measurements were performed for proton beam momenta of 58 GeV/c, 84 GeV/c, and 120 GeV/c. The cross section dependence on the atomic weight (A) of the targets was found to vary as $A^(alpha)$ where $\alpha$ is $0.46\pm0.06$ for a beam momentum of 58 GeV/c and 0.54$\pm$0.05 for 120 GeV/c. The cross sections show reasonable agreement with FLUKA and DPMJET Monte Carlos. Comparisons have also been made with the LAQGSM Monte Carlo.Comment: Accepted for publication in Physical Review D. This version incorporates small changes suggested by referee and small corrections in the neutron production cross sections predicted by FLUK

Measurement of Charged Pion Production Yields off the NuMI Target

The fixed-target MIPP experiment, Fermilab E907, was designed to measure the production of hadrons from the collisions of hadrons of momenta ranging from 5 to 120 GeV/c on a variety of nuclei. These data will generally improve the simulation of particle detectors and predictions of particle beam fluxes at accelerators. The spectrometer momentum resolution is between 3 and 4%, and particle identification is performed for particles ranging between 0.3 and 80 GeV/c using $dE/dx$, time-of-flight and Cherenkov radiation measurements. MIPP collected $1.42 \times10^6$ events of 120 GeV Main Injector protons striking a target used in the NuMI facility at Fermilab. The data have been analyzed and we present here charged pion yields per proton-on-target determined in bins of longitudinal and transverse momentum between 0.5 and 80 GeV/c, with combined statistical and systematic relative uncertainties between 5 and 10%.Comment: 15 pages, 13 figure

First observation of a narrow charm-strange meson DsJ(2632) -> Ds eta and D0 K+

We report the first observation of a charm-strange meson DsJ(2632) at a mass of 2632.6+/-1.6 MeV/c^2 in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, Ds eta and D0 K+. In the Ds eta decay mode we observe an excess of 49.3 events with a significance of 7.2sigma at a mass of 2635.9+/-2.9 MeV/c^2. There is a corresponding peak of 14 events with a significance of 5.3sigma at 2631.5+/-1.9 MeV/c^2 in the decay mode D0 K+. The decay width of this state is <17 MeV/c^2 at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(Dseta) is 0.16+/-0.06. The mechanism which keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the Ds eta decay mode.Comment: 5 pages, 3 included eps figures. v2 as accepted for publication by PR

First Observation of the Doubly Charmed Baryon Xi_cc^+

We observe a signal for the doubly charmed baryon Xi_cc^+ in the charged decay mode Xi_cc^+ --> Lambda_c^+ K- pi+ in data from SELEX, the charm hadro-production experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1 +/- 0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is (3519 +/- 1) MeV/c^2. The Gaussian mass width of this state is 3MeV/c^2, consistent with resolution; its lifetime is less than 33fsec at 90% confidence.Comment: 5 pages, 3 figures, accepted for publication in Physical Review Letter

First Measurement of pi e -> pi e gamma Pion Virtual Compton Scattering

Pion Virtual Compton Scattering (VCS) via the reaction pi e --> pi e gamma was observed in the Fermilab E781 SELEX experiment. SELEX used a 600 GeV/c pi- beam incident on target atomic electrons, detecting the incident pi- and the final state pi-, electron and gamma. Theoretical predictions based on chiral perturbation theory are incorporated into a Monte Carlo simulation of the experiment and are compared to the data. The number of reconstructed events (9) and their distribution with respect to the kinematic variables (for the kinematic region studied) are in reasonable accord with the predictions. The corresponding pi- VCS experimental cross section is sigma=38.8+-13 nb, in agreement with the theoretical expectation sigma=34.7 nb.Comment: 10 pages, 12 figures, 4 tables, 25 references, SELEX home page is http://fn781a.fnal.gov/, revised July 21, 2002 in response to journal referee Comment