72 research outputs found

    Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC

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    Detection of VUV photons with large-area avalanche photodiodes

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    The room-temperature response of large-area avalanche photodiodes (LAAPDs) to 128- and 172-nm light pulses is investigated. The minimum detectable number of photons, which can produce a signal just above the noise level, is found to be around 1300 and 600 photons, respectively. The LAAPD relative statistical fluctuations in the detection of 15 000 photons of 128 nm and 25 500 photons of 172 nm were found to be about 3.9% and 2.2%, respectively. Both the minimum detectable number of photons and statistical fluctuations do not depend on the photon wavelength, but rather on the number of charge carriers produced by the light pulse in the LAAPD. For these light levels, good LAAPD performance is already achieved for gains as low as 30 to 60

    Beam tests of lead tungstate crystal matrices and a silicon strip preshower detector for the CMS electromagnetic calorimeter

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    Tests of lead tungstate crystal matrices carried out in high-energy electron beams in 1996, using new crystals, new APDs and an improved test set-up, confirm that an energy resolution of better than 0 .6% at 100 GeV can be obtained when the longitudinal uniformity of the struck crystal is adequate. Light loss measurements under low dose irradiation are reported. It is shown that there is no loss of energy resolution after irradiation and that the calibration change due to light loss can be tracked with a precision monitoring system. Finally, successuful tests with a preshower device, equipped wi th silicon strip detector readout, are described

    Beam tests of lead tungstate crystal matrices and a silicon strip preshower detector for the CMS electromagnetic calorimeter

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    Tests of lead tungstate crystal matrices carried out in high-energy electron beams in 1996, using new crystals, new APDs and an improved test set-up, confirm that an energy resolution of better than 0 .6% at 100 GeV can be obtained when the longitudinal uniformity of the struck crystal is adequate. Light loss measurements under low dose irradiation are reported. It is shown that there is no loss of energy resolution after irradiation and that the calibration change due to light loss can be tracked with a precision monitoring system. Finally, successuful tests with a preshower device, equipped wi th silicon strip detector readout, are described

    A search for doubly charged higgs production in z0 decays

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    Contains fulltext : 124394.pdf (preprint version ) (Open Access

    Further results on cerium fluoride crystals

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    A systematic investigation of the properties of cerium fluoride monocrystals has been performed by the ''Crystal Clear'' collaboration in view of a possible use of such crystals for the construction of high precision electromagnetic calorimeters for the future generation of high luminosity accelerators. A large sample of different crystals grown by several producers has been studied. The spectroscopic characteristics, the transmission, luminescence aid excitation spectra and the decay time curves are analysed. The light yield of the different crystals is measured with photomultipliers and Si photodiodes and compared to reference standards like BGO and NaI(Tl). The radiation damage behaviour is then presented for gamma and neutron irradiations, at different doses and dose rates, including thermal and optical bleaching

    Search for a scalar top quark using the OPAL detector

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    Contains fulltext : 124482.pdf (preprint version ) (Open Access

    Topological search for the production of neutralinos and scalar particles

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    Contains fulltext : 124609pre.pdf (preprint version ) (Open Access) Contains fulltext : 124609pub.pdf (publisher's version ) (Open Access
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