The ATLAS level-1 central trigger system
The central part of the ATLAS Level-1 trigger system consists of the central trigger processor (CTP), the local trigger processors (LTPs), the timing, trigger, and control (TTC) system, and the read-out driver busy (ROD/spl I.bar/BUSY) modules. The CTP combines information from calorimeter and muon trigger processors, as well as from other sources, and makes the final Level-1 accept decision (L1A) on the basis of lists of selection criteria, implemented as trigger menus. Timing and trigger signals are fanned out to about 40 LTPs, which inject them into the subdetector TTC partitions. The LTPs also support stand-alone running and can generate all necessary signals from memory. The TTC partitions fan out the timing and trigger signals to the subdetector front-end electronics. The ROD/spl I.bar/BUSY modules receive busy signals from the front-end electronics, and send them to the CTP (via an LTP) to throttle the generation of L1As. An overview of the ATLAS Level-1 central trigger system will be presented, with emphasis on the design and tests of the CTP modules.
Diffractive dijet production in √s = 7 TeV pp collisions at the ATLAS Experiment
A data sample of pp collisions with an integrated luminosity of 6.75 nb\(^{-1}\) was collected using a combination of a minimum bias trigger and a single jet trigger at √s = 7 TeV using the ATLAS detector at the Large Hadron Collider. It is analysed to study diffractive dijet production, i.e. events with a hadronic system containing at least two jets in addition to a large region of pseudorapidity devoid of hadronic activity. The cross section is presented differentially with respect to Δη\(^F\), the largest continuous region of pseudorapidity which extends from the edge of the detector at η = ±4.9 and contains no final state particles above threshold momentum cuts, over the region 0 < Δη\(^F\) < 6.5. It is also presented differentially in the variable ξ\(^±\), which estimates the fractional momentum loss of the proton in single diffractive dissociation (pp → pX) events. Comparing the data distributions with a Monte Carlo model suggest that fluctuations in the hadronisation process allow non-diffractive dijets to look like diffractive events, but that the data cannot be described solely by non-diffractive dijet production. In addition, the monitoring of the electromagnetic and jet efficiencies for the ATLAS Level-1 Calorimeter Trigger is described.
ISOLATION OF BOVINE PARAINFLUENZA-3 VIRUS IN CHICK EMBRYOS
Myxovirus parainfluenza-3 (SF-4 bovine strain) was first isolated in tissue cultures of embryonic bovine kidney (EBK) cells (Reisinger, Heddleston, and Manthei, J. Am. Vet. Med. Assoc. 135:147, 1959). This agent is antigenically and biologically related to the human HA-1 strain isolated previously by Chanock et al. in monkey kidney cells (Abinanti and Huebner, Virology 8:391, 1959; Abinanti et al., Proc. Soc. Exptl. Biol. Med. 106:466,1961). At present, both viruses are isolated and propagated in tissue cultures, and tissue-culture products are employed for most research purposes. This investigation indicates that bovine parainfluenza-3 virus can be isolated and produced in 14-day-old embryonated hen's eggs, and that the developing chick embryo is highly susceptible to parainfluenza-3 virus infection. Isolation of parainfluenza-3 virus in chick embryos was compared with isolation in tissue cultures. EBK tissue cultures, maintained in Earle's balanced salts (BSS) with 5.0% calf serum and 0.5% lactalbumin hydrolysate (Nutritional Biochemicals Corp., Cleveland, Ohio), were inoculated with 0.2 ml of nasal-swab material (nasal swabs suspended in 4.0 ml of BSS) from 14 calves with signs of shipping fever. After incubation at 36 C for 6 days, fluids from cultures not showing cytopathic effects were subcultured in fresh cells, and the remaining monolayers were examined for noncytopathic virus by the adsorption-hemagglutination (hemadsorption) test of Vogel and Sholokov (Science 126:358, 1957). Infectious fluids from positive cultures were retained for parainfluenza-3 virus identification. Embryonated hen's eggs (14 days old) were inoculated by the amniotic route with 0.1 ml of nasalswab material. After 4 days at 36 C, the amniotic fluids were harvested and tested for virus by inoculation of EBK cells. Parainfluenza-3 virus was identified by serum-neutralization tests in tissue cultures with immune rabbit serum prepared against the original SF-4 bovine virus isolate. Parainfluenza-3 virus was isolated from six nasal-swab suspensions in both EBK cells and 14-day-old chick embryos. Five embryonated eggs and an equal number of tissue cultures were inoculated with each suspension and, in all cases, eggs were infected more frequently than were corresponding tissue cultures inoculated with larger doses of the same material. The isolation of parainfluenza-3 virus from two samples was complicated in tissue cultures by the presence of infectious bovine rhinotracheitis (IBR) virus which also produces cytopathic effects in EBK cells. IBR virus did not interfere with the isolation of parainfluenza-3 virus in embryonated eggs and was not demonstrated in amniotic fluids 4 days after virus inoculation. Noncytopathic virus, demonstrable by hemadsorption, was not isolated. When three nasal-swab samples containing parainfluenza-3 virus were diluted 1:2 and 1:20 in BSS, virus was isolated from the lower concen-