G. Schuler

The ATLAS central level-1 trigger logic and TTC system

The ATLAS central level-1 trigger logic consists in the Central Trigger Processor and the interface to the detector-specific muon level-1 trigger electronics. It is responsible for forming a level-1 trigger in the ATLAS experiment. The distribution of the timing, trigger and control information from the central trigger processor to the readout electronics of the ATLAS subdetectors is done with the TTC system. Both systems are presented.

The trigger system of the OPAL experiment at LEP

Abstract A pretrigger system is described for running the OPAL detector at the LEP e + e − collider with more bunches than originally foreseen. A large number of low threshold pretrigger signals are formed by several independent components of the detector, and combined by a custom-built VME-based central pretrigger logic. Flexibility, high efficiency and high redundancy in all physics channels are all achieved with low additional deadtime, without any compromise to the trigger performance.

Design of a fast gated charge integrating front end for use in high density CAMAC and fastbus modules

Abstract This paper describes the design principles of two versions of a gated charge integrating front end for use with high energy physics particle detectors. The current integration, gate and clear problems are discussed. A high slew rate design and its implementation on a very small printed circuit board is presented. The design of a 32 channel, 12 bit CAMAC charge integrating ADC is outlined.

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 a trigger menu. Timing and trigger signals are fanned out to about 40 LTPs which inject them into the sub-detector 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 sub-detector front-end electronics. The ROD-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.

STUDY OF CHARM CORRELATIONS IN PI(-)-N INTERACTIONS AT ROOT-S-APPROXIMATE-TO-26 GEV

Abstract We report on the associated production of charmed hadrons in π−-nucleon interactions at s ≃26 GeV at the CERN Ω′ spectrometer. Results on the azimuthal correlation of charmed particle pairs are presented and compared to the predictions of Next-to-Leading-Order QCD calculations.

The beauty contiguity trigger of the BEATRICE experiment: detector, readout and processor overview

Abstract This report describes the impact-parameter trigger used by the WA92 BEATRICE fixed-target experiment at the CERN Omega spectrometer. A comprehensive description of the microstrip detector, readout electronics and trigger processor is given. Preliminary results on its operation in the 1992 data collection are also presented.

The ATLAS level-1 muon to central trigger processor interface (MUCTPI)

The Level-1 Muon to Central Trigger Processor Interface (MUCTPI) receives trigger information synchronously with the 40 MHz LHC clock from all trigger sectors of the muon trigger. The MUCTPI combines the information and calculates total multiplicity values for each of six programmable pT thresholds. It avoids double counting of single muons by taking into account the fact that some muons cross more than one sector. The MUCTPI sends the multiplicity values to the Central Trigger Processor which takes the final Level-1 decision. For every Level-1 Accept the MUCTPI also sends region-of- interest information to the Level-2 trigger and event data to the data acquisition system. Results will be presented on the functionality and performance of a demonstrator of the MUCTPI in full-system stand-alone tests and in several integration tests with other elements of the trigger and data acquisition system. Lessons learned from the demonstrator will be discussed along with plans for the final system.

Measurement of the beauty production cross section in 350 GeV / c π-Cu interactions

Abstract Using a sample of 108 triggered events, produced in π−−Cu interactions at 350 GeV/c, we have identified 26 beauty events. The estimated background in this sample is 0.6 ± 0.6 events. From these data, assuming a linear A-dependence, we measure a beauty production cross section integrated over all χF of 5.7−1.1+1.3 (stat.)−0.5+0.6 (syst.) nb/N.

The ATLAS level-1 muon to central trigger processor interface

The Muon to Central Trigger Processor Interface (MUCTPI) is part of the ATLAS Level-1 trigger system and connects the output of muon trigger system to the Central Trigger Processor (CTP). At every bunch crossing (BC), the MUCTPI receives information on muon candidates from each of the 208 muon trigger sectors and calculates the total multiplicity for each of six transverse momentum (pT) thresholds. This multiplicity value is then sent to the CTP, where it is used together with the input from the Calorimeter trigger to make the final Level-1 Accept (L1A) decision. In addition the MUCTPI provides summary information to the Level-2 trigger and to the data acquisition (DAQ) system for events selected at Level-1. This information is used to define the regions of interest (RoIs) that drive the Level-2 muontrigger processing. The MUCTPI system consists of a 9U VME chassis with a dedicated active backplane and 18 custom designed modules. The design of the modules is based on state-of-the-art FPGA devices and special attention was paid to low-latency in the data transmission and processing. We present the design and implementation of the final version of the MUCTPI. A partially populated MUCTPI system is already installed in the ATLAS experiment and is being used regularly for commissioning tests and combined cosmic ray data taking runs. I. ATLAS FIRST LEVEL MUON TRIGGER The ATLAS Level-1 trigger [1] uses information on clusters and global energy in the calorimeters and multiplicities from tracks found in the dedicated fast muon trigger detectors in order to reduce the event rate to 100 kHz with an overall latency of less than 2.5 μs. The muon trigger detectors are resistive plate chambers (RPC) in the barrel region and thin-gap chambers (TGC) in the end-cap and forward regions of ATLAS. Coincidences of hits in different detector layers are used to identify muon candidates. The muon trigger electronics also determines the transverse-momentum (pT) of the muon candidates and classifies them according to six programmable pT thresholds. The muon trigger detectors are divided into sectors, 64 for the barrel, 96 for the end-cap and 48 for the forward region. Each sector can identify up to two muon candidates. The trigger sector logic modules send information about the position and pT threshold of the muon candidates to the MUCTPI at the bunch crossing (BC) rate of 40.08 MHz. An overview of the muon trigger system is shown in Figure 1 below.

The ATLAS Level-1 Central Trigger Processor (CTP)

The ATLAS Level-1 Central Trigger Processor (CTP) com- bines information from the Level-1 calorimeter and muon trig- ger processors, as well as from other sources such as calibration triggers, and makes the final Level-1 Accept deci- sion. The CTP synchronises the trigger inputs from different sources to the internal clock and aligns them with respect to the same bunch crossing. The algorithm used by the CTP to com- bine the different inputs allows events to be selected on the basis of trigger menus. The CTP provides trigger summary information to the data acquisition and to the Level-2 trigger system, and allows one to monitor various counters of bunch- by-bunch as well as accumulated information on the trigger inputs. The design of the CTP with its six different module types and two dedicated back-planes will be presented.