A novel method for the absolute fluorescence yield measurement by AIRFLY

One of the goals of the AIRFLY (AIR FLuorescence Yield) experiment is to measure the absolute fluorescence yield induced by electrons in air to better than 10% precision. We introduce a new technique for measurement of the absolute fluorescence yield of the 337 nm line that has the advantage of reducing the systematic uncertainty due to the detector calibration. The principle is to compare the measured fluorescence yield to a well known process - the Cerenkov emission. Preliminary measurements taken in the BFT (Beam Test Facility) in Frascati, Italy with 350 MeV electrons are presented. Beam tests in the Argonne Wakefield Accelerator at the Argonne National Laboratory, USA with 14 MeV electrons have also shown that this technique can be applied at lower energies.Comment: presented at the 5th Fluorescence Workshop, El Escorial - Madrid, Spain, 16 - 20 September 200

Temperature and Humidity Dependence of Air Fluorescence Yield measured by AIRFLY

The fluorescence detection of ultra high energy cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules over a wide range of atmospheric parameters, corresponding to altitudes typical of the cosmic ray shower development in the atmosphere. We have studied the temperature and humidity dependence of the fluorescence light spectrum excited by MeV electrons in air. Results for the 313.6 nm, 337.1 nm, 353.7 nm and 391.4 nm bands are reported in this paper. We found that the temperature and humidity dependence of the quenching process changes the fluorescence yield by a sizeable amount (up to 20%) and its effect must be included for a precise estimation of the energy of ultra high energy cosmic rays.Comment: presented at the 5th Fluorescence Workshop, El Escorial - Madrid, Spain, 16 - 20 September 2007, to appear in Nuclear Instruments and Methods

The TOTEM Experiment at the CERN Large Hadron Collider

The TOTEM Experiment will measure the total pp cross-section with the luminosity independent method and study elastic and diffractive scattering at the LHC. To achieve optimum forward coverage for charged particles emitted by the pp collisions in the interaction point IP5, two tracking telescopes, T1 and T2, will be installed on each side in the pseudorapidity region 3,1 <h< 6,5, and Roman Pot stations will be placed at distances of 147m and 220m from IP5. Being an independent experiment but technically integrated into CMS, TOTEM will first operate in standalone mode to pursue its own physics programme and at a later stage together with CMS for a common physics programme. This article gives a description of the TOTEM apparatus and its performance

Pectic Cell Wall Fragments Regulate Tobacco Thin-Cell-Layer Explant Morphogenesis.

Pectic fragments of cell wall polysaccharides, released from the walls of suspension-cultured sycamore cells by treatment with endopolygalacturonase, were tested for morphogenesis-regulating activity in a modified tobacco thin-cell-layer explant (TCL) bioassay (D. Mohnen, S. Eberhard, V. Marfa, N. Doubrava, P. Toubart, D. J. Gollin, T.A. Gruber, W. Nuri, P. Albersheim, and A. Darvill, manuscript submitted). The pectic fragments inhibited the formation of roots on TCLs grown on a root-inducing medium containing 15 micromolar indole-3-butyric acid and 0.5 micromolar kinetin. Addition of the pectic fragments to a root-inducing medium containing 7 micromolar indole-3-butyric acid and 0.15 micromolar kinetin caused roots to form on the basal end of TCLs. TCLs cultured on this medium in the absence of added pectic fragments formed roots along their entire length. The pectic fragments induced polar tissue enlargement and the formation of flowers on TCLs cultured on transition medium. The flower-inducing activity was stable to heat treatment and proteolytic digestion. Pectic fragments isolated from the walls of suspension-cultured tobacco cells were as effective as those from the walls of sycamore cells in inducing de novo flower formation in the TCLs. These results support the hypothesis that oligosaccharins from plant cell walls regulate morphogenesis

Energy dependence of air fluorescence yield measured by AIRFLY

Contains fulltext : 72281.pdf (preprint version ) (Open Access)4 p

Measurement of the pressure dependence of air fluorescence emission induced by electrons

Contains fulltext : 34503.pdf (preprint version ) (Open Access)The fluorescence detection of ultra high energy (≳1e18 eV) cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules, which are excited by the cosmic ray shower particles along their path in the atmosphere. We have made a precise measurement of the fluorescence light spectrum excited by MeV electrons in dry air. We measured the relative intensities of 34 fluorescence bands in the wavelength range from 284 to 429 nm with a high resolution spectrograph. The pressure dependence of the fluorescence spectrum was also measured from a few hPa up to atmospheric pressure. Relative intensities and collisional quenching reference pressures for bands due to transitions from a common upper level were found in agreement with theoretical expectations. The presence of argon in air was found to have a negligible effect on the fluorescence yield. We estimated that the systematic uncertainty on the cosmic ray shower energy due to the pressure dependence of the fluorescence spectrum is reduced to a level of 1% by the AIRFLY results presented in this paper

Spectrally resolved pressure dependence measurements of air fluorescence emission with AIRFLY

Contains fulltext : 72576.pdf (publisher's version ) (Closed access)5 p