Bruschini, Claudio

Darbo, G

Malferrari, L

Martinengo, P

Passaseo, M

Ryzhov, V

Salvo, C

Torelli, M

Infoscience - École polytechnique fédérale de Lausanne

234 OCR OutputThe trigger algorithm should find tracks crossing the detector and flag them as primary or secondaryTrigger algorithm• readout speed of 200 ns/hit• zero supression at the front-end levelTheir relevant features exploited at the trigger level are:the vertex position in the target. The £ront—end and the readout system are fully described in reimm thick) are used as beam monitor.The second and last Z planes are used at the trigger level for findinglevel.Ten more planes (512 strips,20 pm pitch,5 Z and 5 Y) located upstream of the target (Cu or W,2are used to measure the Z coordinate and six to measure Y. Only the Z planes are used at the trigger1 shows a real event from 1992 data taking, full lines are Z planes,dotted lines Y planes). Six planesThe WA92 vertex telescope consists of 12 silicon microstrips planes,2048 strips,25 pm pitch each (fig.Detectors and readout layout1992 data taking.which has been operated as the main second level trigger of the WA92 experiment (see ref. duringIn the following we will show how this strategy has been pursued using a contiguity processorleast one secondary vertex has proved to be very effective ( see ref. [1],[2]).Among the various strategies to face the heavy—quark problem,the selection of events with evidence of atIntroductionAn overview of both the algorithm and the processor architecture is given.of tracks belonging to primary and secondary vertices in less than 30 pa for any track multiplicity.(bidimensional lattice) and highly parallel algorithms (contiguity masks) allow for separate countingand is based on a custom designed ASIC ch.ip.High interconnectivity among processing elementsfixed target experiment WA92/BEATRICE at CERN. It is composed of 11 FASTBUS modulesThe Beauty Contiguity Processor (BCP) is an impact parameter trigger for beauty search in theDipartimento di Fisica and INFN,R0maM. TorelliCERN / EC P,GeneveM .Pas.sa.se0, V.R·yzhc·uDipartimento cli Fisica and INFN ,BolognaL.Ma.Lfer·r·a.·riDipartimento di Fisica and INFN,GenovaC.Br·u.schini, G.Darb0,P.Martinengo, C.Sa,l·v0The Beauty Contiguity Processor of the BEATRICE experiment235 OCR OutputThe PE array is actually built using a dedicated ASIC chip (15000 equivalent gates),64 PE areaffects only the time needed for the readout of the detector.instructions executed by the processor. The number of hits in the event (but not the number of tracks)depends on the actual number of tracks nor on the number of hits in the event but only on the number ofto this particular architecture,the time needed to reconstruct the tracks and measure their IP neitherto the number of shifts needed to make the bottom and top registers electrically connected (fig. 4). Duedelete the associated hits (fig. 3),theu to find secondary tracks and measure their IP,which is proportialshould then be detected at the top row level. This property is exploited to find the primary tracks anddetector a connective path from bottom to top will be created. A voltage applied to the bottom rowfew switches around it,following a programmed rule (Contiguity Mask),in case of a track crossing the4 neighbours by a set of switches. If,for each large dot corresponding to a microstrip fired,we close athe flag set to one,the flag being set according to the detector output. Each PE is connected to itsIn fig. 2 small dots represent PE’s with an internal flag reset to zero, large dots are PE’s withmachine (SIMD).A rectangular mesh of switches helps to explain the functional principle.clock and they execute the same instruction stream,making the BCP a single instruction multiple datanumber of PE’s being equal to the number of microstrips (61:2048). All the PE’s are driven by the samebehaving like a very simple processor. The organization of the array reflects the detector structure,theThe architecture of the BCP is based on a bidimensional array of processing elements (PE),each of themThe processor architecturea track with impact parameter h in a primary track) relative to the first microstrip plane.track is found we can calculate its IP from sl i.e. from the shift function (the function that transform(3),the equation of a track having IP : I h ] becomes a constant function of z. If such a constantwhere w is the microstrip pitch and sg is the integer function of h that better approximates eq.(2.)si(h)w a- hi{iez 1, ..., 6&adding to eq. (1) after the transformation (2)for hyperbolae tracks ( i.e secondary tracks ) the impact parameter is calculated observing thatfor secondary trackshits belonging to parallel ( i.e. primary } tracks are erased and the few points left are used to looktracks while secondary tracks are mapped into hyperbolaeis applied to all the ng hits from plane i. This transformation maps primary tracks into parallel(2)* · w · . . zi(J):;(z§])—z,,) _1:1,...,n; 1:1,...,6(h. : 0 for primary tracks,I P z| h [ for secondary tracks), the transformationz : bz + z., + h (1)writing the equation of a straight line in the x—z plane in the formcenter ofthe target is assumed to give the position along the X coordinatethe Z coordinate of the interaction point,z,,,is extrapolated using the position of the beam.Thetracks according to their impact parameter (IP). It is executed in the following steps:236 OCR OutputSymposium and Medical Imaging Conference,5-9 November 1991,Santa Fe,USAat the Omega spectrometer at CERN CERN/ ECP 91-27,Presented at the 1991 IEEE Nuclear Science[4] A.Beer et al.,A highly integrated trigger and readout system for a silicon microstrip detector installedPhysics B(Proc. Suppl.)27(1992) 251-256[3] M.Adamovich et al.,WA92:a fixed target experiment to study beauty in hadronic interactions,Nucl.A289(1990)584-591[2] G.Darbo and L.Rossi,Fast Trigger for Beauty hadroproduction study,Nucl. Inst. and Meth.[ll .I.F.Baland et al.,Nucl. Phys. B1 (1988) 303Referencesprocessor results,with a very good matching between the tracks found by the BCP and the filter.The processor performances have been cross-checked with an ofi`·line filter which has confirmed theps).processing time required has increased from 10 ps to 30 ps, in addition to the readout time (about 10for one plane to be missing. This has been achieved by modifying the Contiguity Mask Network. Theon last year run experience,the program has been modified to accept tracks with at least 5 hits,allowingThe original trigger program was designed to reconstruct tracks having 6 hits,one per plane.Basedcan be made about the performances of the processor.some 90 milions triggers have been collected. While the data analysis is under way,some considerationsThe BCP has been successfully operated during the 1992 BEATRICE data taking. During this periodIssues from 1992 data takingprograms.a VAX computer. This simulator has proved to be extremely useful in writing and debugging the triggerging and validation, we have designed an interactive cross-simulator running the same source program onprogram which is running on it.To overcome this limitation that makes very difficult the program debugThe BCP architecture that has a "step-lock" control structure does not allow the tracing of thethe VAX Macro assembler.We have deined a dedicated programming language and a compiler has been writen for the BCP usingProgramming language and simulatorclock signals,counts the tracks for each IP class and takes the final trigger decision.to find the primary vertex position, about 300 ns). Lastly the BCPC module generates the control andto the readout from the detector,not adding further dead time to the trigger (apart for the time neededaccount misalignement among the planes. The processing in the FBCT takes 100 ns / hit and it is pipelinedBCPS modules through the FASTBUS auxiliary backplane. Coordinates are also corrected to take intodetectors,execute steps 1 and 2 of the trigger algorithm and send the transformed coordinates to theand 1 BCPC (Beauty Contiguity Processor Controller). The FBCT modules receive the data from thechips.The processor comprises 3 more modules,2 FBCT (Feros to Beauty Contiguity Trigger interface)housed in 8 FASTBUS boards (BCPS for Beauty Contiguity Processor S1ice),each of them holding 24implemented in one chip and 192 chips are needed to realize the whole trigger. The chips are238Fig.4Bottom Register Bottom Registerllllllllllllllll llllllllllllllllEIDCIDDUDDUDD¤¤¤D¤¤¤¤¤¤¤•; CI QDUUDDEIDCIGDD¤¤¤¤¤¤¤¤¤¤¤¤ 4E UDCDDU¤Q|Q¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤D¤¤¤¤¤¤¤¤¤¤¤¤ 4 ¤0|0¤¤¤¤¤¤¤¤¤¤¤¤¤g}DDQ ¤¤¤¤¤¤¤D¤¤¤¤ UU·Q¤D¤D¤DDDD¤UDD¤¤|¤¤¤¤¤D¤¤¤D¤¤¤¤ ¤¤|D¤¤¤D¤D¤U¤¤¤¤¤Top Register Top RegisterSearch for Impact Parameter TracksFig.3Bottom Register Bottom Register1111111111111111¤¤¤¤¤¤¤ ¤¤¤¤¤¤¤¤¤¤¤¤||¤¤¤¤¤|¤¤¤¤ Y ¤¤¤¤¤||¤¤¤¤¤|¤¤¤¤¤¤+¤¤¤¤¤¤¤¤¤ ¤¤+¤¤¤¤a¤¤¤¤¤|¤¤¤¤·t¤¤¤¤¤¤¤¤¤|¤¤¤m§4·¤¤¤¤¤¤¤¤¤¤q¤¤¤¤••¤¤¤¤¤¤¤¤¤¤;¤¤¤¤••¤¤¤¤¤¤¤¤¤BDDDUDIGDGGDDDDDDDGGDDGQQDDDDDDDDD11 11Top RegisterTop RegisterOCR OutputSearch and Erase Primary Vertex Tracks

The beauty contiguity processor of the BEATRICE experiment

http://infoscience.epfl.ch/record/257037/files/1992_Bruschini_BeautyContiguityProcessor_ProcCHEP92.pdf

The beauty contiguity processor of the BEATRICE experiment

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