The central trigger control system of the CMS experiment at CERN Jeitler, M.; Taurok, A.; Bergauer, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
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The Level-1 (L1) Trigger of the CMS experiment uses custom-made, fast electronics, while the experiment's high-level trigger is implemented in computer farms. The Central Trigger Control System ...described in this poster receives physics triggers from the Global Trigger Logic unit, collects information from the various subdetector systems to check if they are ready to accept triggers, reduces excessive trigger rates according to preset rules and finally distributes the trigger (“Level-1 Accept”) together with timing signals to the subdetectors over the so-called “Trigger, and Timing and Control” (TTC) network of the experiment. The complete functionality of the Central Trigger Control System is implemented in one 9U-VME module and several ancillary boards for input and output functions. The system has been used successfully during CMS test runs with cosmics and beam.
The CMS experiment at CERN's Large Hadron Collider will search for new physics at the TeV energy scale. Its trigger system is an essential component in the selection process of potentially ...interesting events. The Global Trigger is the final stage of the first-level selection process. It is implemented as a complex electronic system containing logic devices, which need to be programmed according to physics requirements. It has to reject or accept events for further processing based on coarse measurements of particle properties such as energies, momenta, and location. Algorithms similar to the ones used in the physics analysis are executed in parallel during the event selection process. A graphical setup program to define these algorithms and to subsequently configure the hardware has been developed. The design and implementation of the program, guided by the principal requirements of flexibility, quality assurance, platform-independence and extensibility, are described.
The hardware implementation of the First Level Global Trigger for the Compact Muon Solenoid experiment at the CERN Large Hadron Collider 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 (GT) for every beam crossing taking place at 25
ns intervals. Already, at the first trigger level the GT is able to select complex topological event configurations by performing fast calculations. The electronics is based on VME and relies completely on Field Programmable Gate Arrays (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 performance of the CMS Level-1 Trigger for supersymmetric events at an LHC luminosity of 2 x 1033 cm-2s-1 is reviewed. Energy and momentum trigger thresholds have been chosen to yield a maximum ...Level-1 output rate of 50 kHz, within a safety factor of three. The Level-1 trigger efficiencies for the majority of the channels studied are found to be greater than 90%, which provides a good basis for the High-Level Trigger, where more stringent conditions are applied. Reasons for occasional lower efficiencies are given.
The direct CP violation parameter Re(ϵ′/ϵ) has been measured from the decay rates of neutral kaons into two pions using the NA48 detector at the CERN SPS. The 2001 running period was devoted to ...collecting additional data under varied conditions compared to earlier years (1997–1999). The new data yield the result: Re(ϵ′/ϵ)=(13.7±3.1)×10−4. Combining this result with that published from the 1997, 98 and 99 data, an overall value of Re(ϵ′/ϵ)=(14.7±2.2)×10−4 is obtained from the NA48 experiment.
Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, ...including the transverse momenta ( ) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta ( ), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb super(-1). The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the distributions of the leading jets at high values, the distributions of the at high- and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.
The tagging detector of the CP-violation experiment NA48 at CERN Bergauer, H.; Blümer, H.; Calvetti, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/1998, Letnik:
419, Številka:
2-3
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The CP-violation experiment NA48 at CERN aims at measuring direct CP-violation in the decays of neutral kaons into π+π− and π0π0. The experiment uses simultaneous, almost collinear beams of neutral ...KL0 and KS0 mesons, which are produced on two different targets. KS0 events are “tagged” by measuring the times of the protons that fly towards the KS0 production target. In order to sustain the high rate of 107protons/s in this beam without suffering from too many pile-up events, the detector consists of 24 separate scintillators (12 horizontal and 12 vertical), each of which sees only a small fraction of the beam. Their signals are digitized by specially developed 1GHz FADCs. The exact time of a pulse is established offline by a fit procedure. The detector and its electronics have been successfully used during test beams in 1994–1996 and during the first physics run of NA48 in 1997. The inefficiency of the detector has been measured to 2×10−4. Sources of background have been identified to allow for off-line correction. The mechanical setup of the detector, the 1GHz FADC and results from the test and data runs are presented.
A peaking structure in the J/ psi phi J/ psi phi mass spectrum near threshold is observed in B super( plus or minus ) arrow right J/ psi phi K super( plus or minus )B plus or minus arrow right J/ psi ...phi K plus or minus decays, produced in pp collisions at s=7 TeV collected with the CMS detector at the LHC. The data sample, selected on the basis of the dimuon decay mode of the J/ psi J/ psi , corresponds to an integrated luminosity of 5.2 fb super(-1). Fitting the structure to an S -wave relativistic Breit-Wigner lineshape above a three-body phase-space nonresonant component gives a signal statistical significance exceeding five standard deviations. The fitted mass and width values are m=4148.0 plus or minus 2.4(stat.) plus or minus 6.3(syst.)MeV and Gamma =28-11+15(stat.) plus or minus 19(syst.)MeV, respectively. Evidence for an additional peaking structure at higher J/ psi phi J/ psi phi mass is also reported.
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