122418971
The Reaction $\pi^- p \to K^0 \Lambda^0$ Up to 2375-{MeV}/$c$: New Results and Analysis
Abstract New data are presented on the reaction π − p→K 0 Λ 0 at 13 incident momenta between 1395 and 2375 MeV/ c . A partial-wave analysis has been performed using these data and previous data at lower momenta. The resulting resonance parameters are in broad agreement with recent πN analyses and with the predictions of SU(6) W × O(3) for the couplings.
122373946
A large scintillator array for particle identification by time of flight
Abstract We describe the design and method of operation of a large scintillator array used for particle identification by time of flight. The calibration of the array and the consequences of having approximately 1.1 radiation lengths (∼10 cm) of aluminium in the particle flight-path are described in detail.
121364230
The development of vacuum phototriodes for the CMS electromagnetic calorimeter
Abstract A new generation of vacuum phototriodes (VPTs) has been developed for application in the end-cap sub-system of the crystal electromagnetic calorimeter (ECAL) for the CMS experiment at the CERN Large Hadron Collider (LHC). These VPTs must operate with high reliability for at least 10 years in an extremely hostile environment. Results are presented from an extensive programme of tests, demonstrating that the required properties of significant gain in a 4 T magnetic field, resistance to ionising radiation, and stable operation with large photocurrents can all be satisfied in a robust, compact, inexpensive device.
121404010
The performance of prototype vacuum phototriodes in the first full sized supercrystal array for the CMS ECAL endcaps
The performance of prototype vacuum phototriodes is presented from the first full sized supercrystal array for the CMS ECAL endcaps. The array was exposed to high-energy electrons and tested in magnetic fields of up to 3 T, in the CERN North area, in July and August 1999. The mean VPT electron yield, normalised to a naked crystal light yield of 8 photoelectrons/MeV into an HPMT, was found to be 25 electrons/MeV at 3 T for devices from Research Institute Electron, 35 electrons/MeV for devices from Hamamatsu and 18/23 electrons/MeV from Electron Tubes.
34689945
Vacuum phototriodes for the CMS electromagnetic calorimeter endcap
The measurement of scintillation light from the lead tungstate crystals of the CMS ECAL poses a substantial technical challenge, particularly in the endcap regions, where the radiation levels are highest. The photodetectors must be fast, sensitive, radiation-hard, and operate with significant internal gain in a magnetic field of 4 Tesla. In what follows, the measured performance characteristics of the first half of series production vacuum phototriodes (VPTs), specially developed to satisfy the needs of CMS, will be described. The mean measured VPT gain is 10.2 at 0 T and 9.7 at 4 T.
14766409
The front-end driver card for the CMS silicon strip tracker readout
The first prototypes of the production version of the Front-End Driver (FED) card for the CMS silicon strip tracker are about to be manufactured. The FEDs provide the off-detector processing of the tracker readout system. They digitise and zero-suppress the multiplexed analogue optical data sent on each Level-1 trigger from the ondetector APV25 pipeline chips. This paper outlines the design and describes in detail the implementation of the 96 ADC channel, 9U VME64x form factor card. In total, 440 FEDs will be required to readout the silicon strip tracker.
118898339
Using FU Orionis Outbursts to Constrain Self-Regulated Protostellar Disk Models
One dimensional, convective, vertical structure models and one dimensional, time dependent, radial diffusion models are combined to create a self-consistent picture in which FU~Orionis outbursts occur in young stellar objects (YSOs) as the result of a large scale, self-regulated, thermal ionization instability in the surrounding protostellar accretion disk. By fitting the results of time dependent disk models to observed time scales of FU~Orionis events, we estimate the magnitude of the effeciency of the effective viscous stress in the inner disk (r < 1 AU) to be, in accordance with the ad hoc ``alpha'' prescription, 10^{-4} where hydrogen is neutral and 10^{-3} where hydrogen is ionized. We hypothesize that all YSOs receive infall onto their outer disks which is steady (or slowly declining with time) and that FU~Orionis outbursts are self-regulated, disk outbursts which occur only in systems which transport matter inward at a rate sufficiently high to cause hydrogen to be ionized in the inner disk. We estimate a critical mass flux of 5x10^{-7} solar masses / year {\it independent of the magnitude of alpha} for systems with one solar mass, three solar radius central objects. Infall accretion rates in the range of (1-10)x10^{-6} solar masses per year produce observed FU~Orionis time scales consistent with estimates of spherical molecular cloud core collapse rates.