R. Cester

A study of the effect of molecular and aerosol conditions in the atmosphere on air fluorescence measurements at the Pierre Auger Observatory

The air fluorescence detector of the Pierre Auger Observatory is designed to perform calorimetric measurements of extensive air showers created by cosmic rays of above 10 eV. To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group of monitoring instruments to record atmospheric conditions across the detector site, an area exceeding 3000 km. The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierre Auger Observatory since the start of regular operations in 2004, and includes a discussion of the impact of these measurements on air shower reconstructions. Between 10 and 10 eV, the systematic uncertainties due to all atmospheric effects increase from 4% to 8% in measurements of shower energy, and 4 g cm 2 to 8 g cm 2 in measurements of the shower maximum. 2010 Elsevier B.V. All rights reserved.

The Lidar System of the Pierre Auger Observatory

The Pierre Auger Observatory in Malargue, Argentina, is designed to study the origin of ultrahigh energy cosmic rays with energies above 10 18 eV. The energy calibration of the detector is based on a system of four air fluorescence detectors. To obtain reliable calorimetric information from the fluorescence stations, the atmospheric conditions at the experiments site need to be monitored continuously during operation. One of the components of the observatorys atmospheric monitoring system is a set of four elastic backscatter lidar stations, one station at each of the fluorescence detector sites. This paper describes the design, current status, standard operation procedure, and performance of the lidar system of the Pierre Auger Observatory. r 2007 Elsevier B.V. All rights reserved. PACS: 07.60.� j; 42.68.Wt; 92.60.� e; 96.50.sd

Study of the chi(1) and chi(2) charmonium states formed in anti-p p annihilations

We report on a study of the χ1(3P1) and χ2(3P2) states of charmonium formed in antiproton-proton annihilations. An energy scan through the resonances, performed with a very narrow momentum-band beam of antiprotons intersecting a hydrogen jet target, enables us to perform very precise measurements of the mass and the total width of the two resonances. From a sample of 513 χ1 and 585 χ2 events we find Mχ1 = (3510.53±0.13) MeV/c2, Mχ2 = (3556.15±0.14) MeV/c2, Γχ1 = (0.88±0.14) MeV and Γχ2 = (1.98±0.18) MeV. From our measurement of the quantity Γ(R → pp) × BR(R → Jψ → e+ e−), using known branching ratios, we obtain Λ(χ1 → pp) = (69±13) eV and Λ(χ2 → pp) = (180±31) eV.

Production of the f2 (1520) resonance in antiproton—proton annihilations at s = 2980 and MeV☆

Abstract We present measurements of the 2π0 mass spectrum in proton—antiproton annihilations. The f2 (1520) resonance is strongly produced in the 3π0 channel. Its production along with an η is observed, but strongly suppressed. Other features are seen in the data, including the f2 (1270) and structures at 2000 MeV/c2 and above.

THE THRESHOLD GAS CHERENKOV COUNTER OF CHARMONIUM EXPERIMENT 835 AT FERMILAB

Abstract A threshold gas Cherenkov counter is used in Fermilab experiment 835 to tag electrons from the decay of charmonium states. It is an improved version of the counter used in a previous charmonium experiment, E760. The new features of the design, the technique used to build a set of ellipsoidal mirrors, and the counter performance are presented.

A very short threshold Cherenkov counter operated with Freon at atmospheric pressure

Abstract We have built a prototype 40 cm long atmospheric pressure threshold Cherenkov counter and tested it with Freon 13 at STP. With 1–4 Gev/ c electrons we measure an average number of 6 photoelectrons/incident particle. Below π threshold the π rejection is measured to be 4 × 10 −3 , with a corresponding electron efficiency of 0.96.

A large acceptance threshold Cherenkov counter for experiment 760 at Fermilab

Abstract A threshold gas Cherenkov counter is used in Fermilab Experiment 760 to tag electrons in the detection of charmonium states. Mechanical structures and mirrors were built with carbon-fiber-epoxy composites, resulting in a light weight detector covering 2π in azimuthal angle. The counter is operated at atmospheric pressure with different gases, CO 2 and Freon 13, respectively in the two cells at small and large polar angles, to maximize pion rejection. Design considerations, construction details, and performance of the counter are described.

A technique to produce mirrors for the Auger Observatory

The Fluorescence Detector of the Pierre Auger Cosmic Ray Observatory will provide a measurement of the parameters of Extensive Air Showers with energy >10/sup 19/ eV. The mirror of the Fluorescence Detector prototype has dimension /spl sim/3.6/spl times/3.6 m/sup 2/ and is composed of 49 trapezoidal segments of approximately 50/spl times/50 cm/sup 2/. Each segment is curved using a steel mold in which the glass sags in a controlled environment. The glass is then aluminized under vacuum and coated with oxide (Al/sub 2/O/sub 3/). The oxide thickness is chosen to maximize the reflectivity in the wavelength range of fluorescence light (300 nm </spl lambda/<400 nm). The 49 mirror segments plus 10 spare ones are now ready for installation. In this paper we discuss the production technique of the segments for the Torino prototype mirror.

Measurement of the branching ratios ψ′→e+e-, ψ′→J/ψππ, and ψ′→J/ψη

We have measured several branching ratios for

A glass spherical Cherenkov counter based on total internal reflection

\psi^\prime