Dfub 95/2 Results from a Neural Trigger Based on the Ma16 Microprocessor#

Results from a neural-network trigger based on the digital MA16 chip of Siemens are reported. The neural trigger has been applied to data from the WA92 experiment, looking for beauty particles, which have been collected during a run in which a neural trigger module based on Intel's analog neural chip ETANN operated, as already reported. The MA16 has a precision of 16 bits for input variables, 16 bits for weights, 16 bits for scalar multipliers modifying the transfer function shape, 47 bits for thresholds, 53 bits for internal calculations, 38 bits for the output. Of the latter only 16 bits are used in the MA16 board, as input to the transfer function inplemented on 16-bit addressable EPROM's. The MA16 board operated at 50 MHz, yielding a response time for a 16 input variable net of 3 μs for a Fisher discriminant (1-layer net) and of 6 μs for a 2-layer net. Results are compared with those previously obtained with the ETANN trigger. # Paper presented at the 4th Int. Workshop on Software Engineering, Artificial Intelligence and Expert Systems for High Energy and Nuclear Physics, April 4-8, 1995, Pisa, Italy. * E-mail: [email protected], 38239::odorico We have already reported at the previous workshop of this series [1] and in subsequent publications (see e.g. [2]) the results from a neural trigger based on the analog ETANN chip which operated in the experiment WA92 at CERN during the 1993 run. The neural trigger included also two boards based on the digital microprocessor MA16, which were not ready at the time of the run because of delays in the debugging of the board control code. We present here results from the MA16 board of the neural trigger module which has been applied off-line to the same experimental data on which the ETANN board operated on line. Aims of the Neural Trigger in WA92. WA92 is an experiment at CERN looking for the production of beauty particles by a π− beam at 350 GeV/c impinging on a Cu target (during the 1993 run) [3]. The Neural Trigger hosted in the experiment had the the task of selecting events, already accepted by the WA92 standard trigger, by exploiting a non-leptonic beauty decay signature and to accept them into a special data stream, meant for early analysis. Specifically, the Neural Trigger was trained to enrich the fraction of events with C3 secondary vertices, i.e. branching into three tracks with sum of electric charges equal to +1 or -1. C3 vertices are sought for further analysis aimed to identify charm and beauty non-leptonic decays. Training was done with previously collected events, certified off-line to contain or not a C3 vertex by the Trident event reconstruction program. Input from the WA92 Trigger Apparatus. Input to the Neural Trigger was provided by the Beauty Contiguity Processor (BCP) [4], which determined tracks and their impact parameters on-line, using hit locations in the silicon microstrip Vertex Detector. The BCP output, arranged in five 64-bit hit-maps each one corresponding to separate impact parameter windows, was preprocessed within the neural crate to yield 16 input variables for the neural chips. Neural Trigger Module. The Neural Trigger hardware consists of a crate hosting VME9U boards: i) an Interface Board receiving the five 64-bit words plus a termination word from the BCP and control bits to synchronize with the beam pulse; ii) four Preprocessing Boards hosting two independent Preprocessing Unit each, each one of the latter calculating the input variables referring to a given impact parameter window entering the neural chips (with 5 impact parameter windows only 5 such units are actually used); iii) an ETANN board, hosting two independent ETANN neural chips [5]; iv) two MA16 boards, hosting a MA16 neural chip each; v) a (VME6U) VIC board of CES interfacing the VME bus to a personal computer for control and monitoring operations, and which also allows to simulate on-line running conditions by having recorded experimental inputs passed through the crate with subsequent collection of the corresponding outputs. At the time of running the MA16 boards were not yet operating, waiting for debugging of the microcode controlling the boards. The Neural Trigger output trigger bit was sent to the WA92 trigger apparatus and fuller information about the neural chips responses was sent to the WA92 event recording apparatus where it was written in the event record on tape.