838 research outputs found
MEASUREMENT OF BRANCHING FRACTIONS OF B DECAYS TO K_1(1270) PI AND K_1(1400) PI AND DETERMINATION OF THE CKM ANGLE ALPHA FROM B0 --> A_1(1260)+/- PI-/+
No full textThis dissertation reports the measurement of the branching fractions of neutral and charged B meson decays to final states containing a K_1(1270) or K_1(1400) meson and a charged pion. The data, collected with the BaBar detector at the SLAC National Accelerator Laboratory, correspond to 454 million B Bbar pairs produced in e+ e- annihilation. We use the results to estimate the weak phase alpha from the time dependent CP asymmetries in B0 --> a_1(1260)+/- pi-/+ decays
Upstream regulation of yeast TOR complexes
No full textNitrogen is an essential component of living organism. Protein synthesis and biosynthesis of nitrogen containing molecules essential for growth, such as amino acids and NAD, strictly depend on the availability of the nitrogen source. Limiting amount of nitrogen limit cell growth. Exogenous amino acids and other nitrogenous compounds such as ammonium constitute the nitrogen source. The budding yeast S. cerevisiae can sense and utilize a total of 21 different nitrogenous compounds to sustain growth. The uptake and utilization of different nitrogen sources is hierarchical and subject to strict and complex regulation at the transcriptional, translation and post-translational level. In general, preferred nitrogen sources inhibit the uptake and catabolism of non-preferred nitrogen sources.
The target of rapamycin (TOR) is a conserved Ser/Thr protein kinase among eukaryotes controlling growth in response to nutrients and growth factors. TOR is found in two essential conserved multiprotein complexes named TOR complex 1 (TORC1) and TORC2. In yeast, TORC1 signaling is sensitive to nutrients, particularly to availability of the nitrogen source. Thus, TORC1 by promoting anabolic processes, such as protein synthesis and ribosome biogenesis, couples growth to the availability of the nitrogen source.
The sensing mechanism activating TORC1 in response to nitrogen source sufficiency is only poorly understood. Recent studies identified the EGO complex as intermediary component of the amino acid sensing pathway. In the presence of amino acids, particularly leucine, the EGO complex is activated and promotes TORC1 activity. The small GTP binding proteins Gtr1 and Gtr2 are part of the EGO complex. Gtr1 and Gtr2 form a heterodimeric complex. In response to amino acids Gtr1 is loaded with GTP and Gtr2 with GDP, leading to activation of the EGO complex. Several factors determine EGO complex activation by dictating the Gtr1/2 guanosine loading. Vam6 was proposed to act as guanosine exchange factor (GEF) towards Gtr1. The Npr2/Npr3/Iml1 complex was reported to act as GTPase activating protein (GAP) for Gtr1. Therefore, amino acid stimulation of TORC1 is decreased in the absence of Vam6 and increased in the absence of Iml1. Several observations point out that EGO complex signaling, alone, is not sufficient to explain TORC1 activation by the nitrogen source. For instance, 1) components of the EGO complex signaling are not essential; 2) ammonium starvation down-regulates growth even in cells where EGO complex signaling is hyperactivated. Therefore, nitrogen source and amino acids sufficiency might signal to TORC1 via distinct mechanisms.
In this study we analyze the effect of different nitrogen sources on TORC1 activity. We use the phosphorylation state of the direct TORC1 target Sch9 as readout for TORC1 activity. We describe that preferred nitrogen sources activate TORC1 signaling stronger and better than non-preferred nitrogen source. TORC1 activation by preferred nitrogen sources is paralleled by an increase in glutamine synthesis and accumulation. Growth is increased in the presence of preferred nitrogen sources in a glutamine synthesis dependent way. Therefore, glutamine constitutes a metabolic input linking TORC1 activation in response to the quality of the nitrogen source to growth capacity. We find that EGO complex signaling is dispensable when a preferred nitrogen source is provided. TORC1 activation and growth increase are still induced in cells compromised for EGO complex signaling. Taken together, we demonstrate that nitrogen source and amino acid sufficiency act via discrete mechanisms to activate TORC1
Performance of a high-throughput tracking processor implemented on Stratix-V FPGA
No full textTwo of the biggest challenges for future HEP experiments at hadron colliders are triggering and track reconstruction of high-multiplicity events, where collisions have multiple primary vertices. The highly-non-linear scaling of computing power required for these tasks encourages the adoption of non-traditional, specialized architectures. Amongst them, the “artificial retina” approach, inspired by the architecture of the vision system in the living brain, promises large efficiency of hardware utilization, low-power and low-latency when implemented in state-of-art FPGA devices. The INFN-RETINA project has been a 3-year effort dedicated to investigate the potential of that approach in a real-time tracking processor at Level-0 of the LHC HEP experiments. We present results from studies performed on a prototype system capable of carrying out track reconstruction in a generic 6-layer silicon-strip detector with sub-μs latency at an event rate in excess of 30 MHz, and how a large-scale system can be implemented on multiple boards interconnected with high-speed optical links. Possible applications to real experimental environments will be also discussed
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
Effective lifetime measurements in the B-s(0) -> K+K-, B-0 -> K+pi(-) and B-s(0) -> pi K-+(-) decays
No full textMeasurements of the effective lifetimes in the View the MathML source, B0→K+π− and View the MathML source decays are presented using 1.0 fb−1 of pp collision data collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The analysis uses a data-driven approach to correct for the decay time acceptance.
This is the most precise determination to date of the effective lifetime in the View the MathML source decay and provides constraints on contributions from physics beyond the Standard Model to the View the MathML source mixing phase and the width difference ΔΓs
Rare charmless B decays at the B-factories
No full textWe report on recent results on charmless hadronic and radiative rare B decays, based on data collected by the BaBar and Belle detectors at the B-factories. The potential reach of a Super B Factory is also presented
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
The artificial retina for track reconstruction at the LHC crossing rate
No full textWe present the results of an R&D study for a specialized processor capable of precisely reconstructing events with hundreds of charged-particle tracks in pixel and silicon strip detectors at 40 MHz, thus suitable for processing LHC events at the full crossing frequency. For this purpose we design and test a massively parallel pattern-recognition algorithm, inspired to the current understanding of the mechanisms adopted by the primary visual cortex of mammals in the early stages of visual-information processing. The detailed geometry and charged-particle's activity of a large tracking detector are simulated and used to assess the performance of the artificial retina algorithm. We find that high-quality tracking in large detectors is possible with sub-microsecond latencies when the algorithm is implemented in modern, high-speed, high-bandwidth FPGA devices
Real-time reconstruction of pixel vertex detectors with FPGAs
No full textThe LHCb experiment is undergoing a major upgrade in view of Run-3, in which the complete detector will be read out, and events fully reconstructed, at the full LHC crossing rate (averaging 30 MHz). One of the key steps of event reconstruction is finding tracks in the new, high precision pixel vertex detector (VELOPIX). This step is the necessary starting point for most of the rest of the reconstruction, and requires a significant fraction (close to a half) of the total CPU time that will be availabe in the upgraded Event Filter Farm. We present the current status of a LHCb R&D project devoted to accelerating this computation by the use of an array of commercial state-of-the-art FPGA cards embedded in the DAQ system, performing pattern recognition in the vertex detector 'on the fly', while the detector is being readout at 30 MHz
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