662 research outputs found
The LHCb trigger system: performance and outlook
No full textThe LHCb experiment is a spectrometer dedicated to the study of heavy flavor at the LHC. The rate of proton-proton collisions at the LHC is 15 MHz, of which only 5 kHz can be written to storage for offline analysis. The trigger system plays a key role in selecting signal events and rejecting background, and is comprised of a hardware level (L0), reducing the rate to the maxi- mum at which the detector can be fully read out, and a High Level Trigger (HLT) -implemented in software and deployed on a farm of roughly 25000 parallel processing cores- responsible for reducing the rate to the 5 kHz which can be processed offline. The LHCb trigger system allowed LHCb to run at twice its design luminosity in 2012, and performed beyond the nominal design in terms of signal yields. The design and performance of the selection algorithms are discussed in the context of the 2012 data taking, and planned improvements for RunII are presente
Real-time Detection of Antihydrogen Annihilations and Applications to Spectroscopy
No full textA detection scheme based on real-time measurement of antihydrogen annihilations during radiation injection is presented, which allows an efficient use of the trapped atoms for laser and microwave spectroscopy. The application of real-time detection of H¯ annihilations to microwave spectroscopy, which yielded the first evidence of microwave induced spin-flip transitions in trapped antihydrogen [1], is reported
Development of a High-Throughput Tracking Processor on FPGA Boards
No full textWe present the latest results on the prototype of a tracking processor capable of reconstructing events in a silicon-strip tracker at about 40 MHz event rate with sub-microsecond latency. The processor is based on an advanced pattern-recognition algorithm, called “artificial retina”, inspired to the vision system of the mammals. We design and implement one of the first functional prototype of this processor on a DAQ board based on Alters Stratix III FPGAs. Then, in order to test the maximum rate capability, we port and optimize the processor on a high-speed board equipped with Altera Stratix V FPGAs. Future applications of this novel approach as real-time track trigger at LHC experiments are also discussed
Real-time track reconstruction during readout using an artificial retina architecture
No full textWe present the results of a study of the feasibility of implementing real-time track reconstruction within the framework of a pre-existing readout system, using the "Artificial Retina" approach. This is the first attempt at building a complete medium-size prototype of this kind (comprising about 8M Logic Elements, distributed on several separate boards), operating it continuously at its limit speed. This study emphasizes logic architecture, correct operation, size, and compatibility with a standard readout framework, to explore its useability as an add-on to a conventional readout system. For this reason we have chosen for implementation a moderate-cost, moderate-speed board already in use in the data acquisition of an existing HEP experiment. Our choice fell on the readout boards currently in use by the NA62 experiment (TEL62), each equipped with 5 Altera Stratix III FPGAs and 4 Gbit/s ethernet interface. We have reprogrammed the board firmware in two different ways, to make the boards behave as the two main blocks of a AR system (switch system, and cellular processor farm). They are interfaced via the front panel, inverting their normal data flow path, by custom interconnection boards, and devoped in internal sytem for continuous feeding of data in order to test them at their maximum achievable speed. We report the results of extensive tests perfomed with this prototype, and discuss their implications regarding the applicability of the "retina architecture" to faster, and custom-developed real-time processors
Searches for CPV in decays at LHCb
No full textSingly-Cabibbo-suppressed D + ( s ) decays are a good place to search for CP violation in charm, which in the Standard Model is expected to be small, at the level of 0.1% or less. In Cabibbo- Favored decays of charm mesons, observing a significant CP violation with the present level of precision would be a signature of new physics. We report on recent searches for CP violation in D + ( s ) decays by the LHCb experiment, using proton-proton collision data corresponding to an integrated luminosity of 3 fb-1, recorded at centre-of-mass energies of 7 and 8TeV. In particular, we report on searches for CP violation in D ! h ′ p and D s ! h ′ p decays
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Two- and Three-Body Charmless B Decays at BaBar
No full textWe report recent measurements of rare charmless B decays performed by BaBar. The results are based on the final BaBar dataset of 424 fb{sup -1} collected at the PEP-II B-factory based at the SLAC National Accelerator Laboratory. The study of rare B decays is a key ingredient to meet two of the main goals of the B-factories: assessing the validity of the Cabibbo-Kobayashi-Maskawa (CKM) picture of CP-violation by precisely measuring the elements of the Unitarity Triangle (UT), and searching for hints of New Physics (NP), or otherwise constraining NP scenarios, in processes which are suppressed in the Standard Model (SM). In loop processes, in particular, NP at some higher energy scale may manifest itself in the low energy effective theory as new couplings, such as those introduced by new very massive virtual particles in the loop. In NP searches hadronic uncertainties can play a major role, expecially for branching fraction measurements. Many theoretical uncertainties cancel in ratios of amplitudes, and most NP probes are therefore of this kind. In the following sections we report recent measurements, performed by the BaBar Collaboration, that are relevant to NP searches in charmless hadronic B decays
Published in arXiv:1101.0845.
No full textMeasurement of the weak phase α from B 0 → a1(1260) ± π ∓ decay
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Measurements of the CKM Angle Alpha at BaBar
No full textThe authors present improved measurements of the branching fractions and CP-asymmetries fin the B{sup 0} {yields} {pi}{sup +}{pi}{sup -}, B{sup 0} {yields} {pi}{sup 0}{pi}{sup 0}, and B{sup +} {yields} {rho}{sup +}{rho}{sup 0} decays, which impact the determination of {alpha}. The combined branching fractions of B {yields} K{sub 1}(1270){pi} and B {yields} K{sub 1}(1400){pi} decays are measured for the first time and allow a novel determination of {alpha} in the B{sup 0} {yields} {alpha}{sub 1}(1260){sup {+-}}{pi}{sup {-+}} decay channel. These measurements are performed using the final dataset collected by the BaBar detector at the PEP-II B-factory. The primary goal of the experiments based at the B factories is to test the Cabibbo-Kobayashi-Maskawa (CKM) picture of CP violation in the standard model of electroweak interactions. This can be achieved by measuring the angles and sides of the Unitarity Triangle in a redundant way
Measurement of branching fractions of B decays to K<sub>1</sub>(1270)π and K<sub>1</sub>(1400)π and determination of the CKM angle α from B<sup>0</sup>→ a<sub>1</sub>(1260)<sup>±</sup> π<sup>∓</sup>
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