The CMS Drift Tube Trigger Track Finder

Muons are among the decay products of many new particles that may be discovered at the CERN Large Hadron Collider. At the first trigger level the identification of muons and the determination of their transverse momenta and location is performed by the Drift Tube Trigger Track Finder in the central region of the Compact Muon Solenoid experiment, using track segments detected in the Drift Tube muon chambers. Track finding is performed both in pseudorapidity and azimuth. Track candidates are ranked and sorted, and the best four are delivered to the subsequent high level trigger stage. The concept, design, control and simulation software as well as the expected performance of the system are described. Prototyping, production and tests are also summarized

Implementation and Synchronisation of the First Level Global Trigger for the CMS Experiment at LHC

The hardware implementation of the First Level Global Trigger for the CMS experiment at the CERN Large Hadron Collider LHC is described. Special emphasis is given to the algorithm logic and the synchronisation procedure. Up to 128 different trigger algorithms are calculated in parallel by the Global Trigger for every beam crossing taking place in 25 ns intervals. Already at the first trigger level the Global Trigger is able to select complex topological event configurations by performing fast calculations. The electronics is based on VME and relies completely on FPGA technology. The electronic circuits are optimised for speed by exploiting to a great extent the small look-up tables provided in the FPGA chips

The Central Trigger Control System of the CMS Experiment at CERN

The Large Hadron Collider delivers up to 32 million physics collisions per second. This rate is far too high to be processed by present-day computer farms, let alone stored on disk by the experiments for offline analysis. A fast selection of interesting events must therefore be made. In the CMS experiment this is implemented in two stages: the Level-1 Trigger of the CMS experiment uses custom-made, fast electronics, while the experiment's high-level trigger is implemented in computer farms. The Level-1 Global Trigger electronics has to receive signals from the subdetector systems that enter the trigger (mostly from muon detectors and calorimeters), synchronize them, determine if a pre-set trigger condition is fulfilled, check if the various subsystems are ready to accept triggers based on information from the Trigger Throttling System and on calculations of possible dead-times, and finally distribute the trigger (``Level-1 Accept'') together with timing signals to the subdetectors over the so-called ``Trigger, Timing and Control'' distribution tree of the experiment. These functions are fulfilled by several specialized, custom-made VME modules, most of which are housed in one crate. The overall control is exerted by the central ``Trigger Control System'', which is described in this paper. It consists of one main module and several ancillary boards for input and output functions. {\bf Keywords:} Trigger concepts and systems (hardware and software), Digital electronic circuit

Prediction of molecular alignment of nucleic acids in aligned media

Contains fulltext : 35529.pdf (publisher's version ) (Closed access)We demonstrate - using the data base of all deposited DNA and RNA structures aligned in Pf1-medium and RDC refined - that for nucleic acids in a Pf1-medium the electrostatic alignment tensor can be predicted reliably and accurately via a simple and fast calculation based on the gyration tensor spanned out by the phosphodiester atoms. The rhombicity is well predicted over its full range from 0 to 0.66, while the alignment tensor orientation is predicted correctly for rhombicities up to ca. 0.4, for larger rhombicities it appears to deviate somewhat more than expected based on structural noise and measurement error. This simple analytical approach is based on the Debye-Huckel approximation for the electrostatic interaction potential, valid at distances sufficiently far away from a poly-ionic charged surface, a condition naturally enforced when the charge of alignment medium and solute are of equal sign, as for nucleic acids in a Pf1-phage medium. For the usual salt strengths and nucleic acid sizes, the Debye-Huckel screening length is smaller than the nucleic acid size, but large enough for the collective of Debye-Huckel spheres to encompass the whole molecule. The molecular alignment is then purely electrostatic, but it's functional form is under these conditions similar to that for steric alignment. The proposed analytical expression allows for very fast calculation of the alignment tensor and hence RDCs from the conformation of the nucleic acid molecule. This information provides opportunities for improved structure determination of nucleic acids, including better assessment of dynamics in (multi-domain) nucleic acids and the possibility to incorporate alignment tensor prediction from shape directly into the structure calculation process. The procedures are incorporated into MATLAB scripts, which are available on request