The production of a Z boson in association with a J/psi meson in proton-proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and ...allows studies of multiple parton scattering. Using 20.3 fb^-1 of data collected with the ATLAS experiment at the LHC in pp collisions at (sqrt)s=8 TeV, the first measurement of associated Z + Jpsi production is presented for both prompt and non-prompt J/psi production, with both signatures having a significance in excess of 5(sigma). The inclusive production cross-sections for Z boson production (analysed in mu^+mu^- or e^+e^- decay modes) in association with prompt and non-prompt J/psi (rightarrow mu^+mu^-) are measured relative to the inclusive production rate of Z bosons in the same fiducial volume to be (36.8 +/- 6.7 +/- 2.5) x 10^-7 and (65.8 +/- 9.2 +/- 4.2) x 10^-7 respectively. Normalised differential production cross-section ratios are also determined as a function of the Jpsi transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of 5.3 (3.7) mb at 68 (95)% confidence level is placed on the effective cross-section regulating double parton interactions.
The performance of the ATLAS muon trigger system is evaluated with proton-proton collision data collected in 2012 at the Large Hadron Collider at a centre-of-mass energy of 8 TeV. It is primarily ...evaluated using events containing a pair of muons from the decay of Formula: see text bosons. The efficiency of the single-muon trigger is measured for muons with transverse momentum Formula: see text GeV, with a statistical uncertainty of less than 0.01 % and a systematic uncertainty of 0.6 %. The Formula: see text range for efficiency determination is extended by using muons from decays of Formula: see text mesons, Formula: see text bosons, and top quarks. The muon trigger shows highly uniform and stable performance. The performance is compared to the prediction of a detailed simulation.
This paper reports on a search for narrow resonances in diboson production in the Formula: see text final state using Formula: see text collision data corresponding to an integrated luminosity of ...Formula: see text fbFormula: see text collected at Formula: see text TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95 % confidence level are set on the production cross section times branching ratio for Kaluza-Klein gravitons predicted by the Randall-Sundrum model and for Extended Gauge Model Formula: see text bosons. These results lead to the exclusion of mass values below 740 and 1590 GeV for the graviton and Formula: see text boson respectively.
A measurement of Formula: see text boson production in lead-lead collisions at Formula: see text is presented. It is based on the analysis of data collected with the ATLAS detector at the LHC in 2011 ...corresponding to an integrated luminosity of 0.14 Formula: see text and 0.15 Formula: see text in the muon and electron decay channels, respectively. The differential production yields and lepton charge asymmetry are each measured as a function of the average number of participating nucleons Formula: see text and absolute pseudorapidity of the charged lepton. The results are compared to predictions based on next-to-leading-order QCD calculations. These measurements are, in principle, sensitive to possible nuclear modifications to the parton distribution functions and also provide information on scaling of Formula: see text boson production in multi-nucleon systems.
Double-differential three-jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of Formula: see text using the ATLAS detector at the large hadron collider. ...The measurements are presented as a function of the three-jet mass Formula: see text, in bins of the sum of the absolute rapidity separations between the three leading jets Formula: see text. Invariant masses extending up to 5 TeV are reached for Formula: see text. These measurements use a sample of data recorded using the ATLAS detector in 2011, which corresponds to an integrated luminosity of Formula: see text. Jets are identified using the anti-Formula: see text algorithm with two different jet radius parameters, Formula: see text and Formula: see text. The dominant uncertainty in these measurements comes from the jet energy scale. Next-to-leading-order QCD calculations corrected to account for non-perturbative effects are compared to the measurements. Good agreement is found between the data and the theoretical predictions based on most of the available sets of parton distribution functions, over the full kinematic range, covering almost seven orders of magnitude in the measured cross-section values.
Cellular Dynamics of Network Memory Fuster, Joaquin M.
Zeitschrift für Naturforschung C. A journal of biosciences,
07/1998, Letnik:
53, Številka:
7
Journal Article
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One example of “emergence” is the development, as a result of neural ontogeny and living experience, of cortical networks capable of representing and retaining cognitive information. A large body of ...evidence from neuropsychology, electrophysiology and neuroimaging indicates that so-called working memory and long-term memory share the same neural substrate in the cerebral cortex. That substrate consists in a system of widespread, overlapping and hierarchically organized networks of cortical neurons. In this system, any neuron or group of neurons can be part of many networks, and thus many memories. Working memory is the temporary activation of one such network of long-term memory for the purpose of executing an action in the near future. The activation of the network may be brought about by stimuli that by virtue of prior experience are in some manner associated with the cognitive content of the network, including the response of the organism to those stimuli. The mechanisms by which the network stays activated are presumed to include the recurrent re-entry of impulses through associated neuronal assemblies of the network. Consistent with this notion is the following evidence: (1) working memory depends on the functional integrity of cortico-corti-cal connective loops; and (2) during working memory, remarkable similarities -including “attractor behavior” -have been observed between firing patterns in real cortex and in an artificial recurrent network.
A search for the production of single-top-quarks in association with missing energy is performed in proton-proton collisions at a centre-of-mass energy of Formula: see text with the ATLAS experiment ...at the large hadron collider using data collected in 2012, corresponding to an integrated luminosity of Formula: see text fbFormula: see text. In this search, the Formula: see text boson from the top quark is required to decay into an electron or a muon and a neutrino. No deviation from the standard model prediction is observed, and upper limits are set on the production cross-section for resonant and non-resonant production of an invisible exotic state in association with a right-handed top quark. In the case of resonant production, for a spin-Formula: see text resonance with a mass of Formula: see text GeV, an effective coupling strength above Formula: see text is excluded at 95Formula: see text confidence level for the top quark and an invisible spin-Formula: see text state with mass between Formula: see text and Formula: see text GeV. In the case of non-resonant production, an effective coupling strength above Formula: see text is excluded at 95Formula: see text confidence level for the top quark and an invisible spin-Formula: see text state with mass between Formula: see text and Formula: see text GeV.
This article reports on a search for dark matter pair production in association with bottom or top quarks in Formula: see text of Formula: see text collisions collected at Formula: see text TeV by ...the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing Formula: see text-quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter-nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a coloured mediator suitable to explain a possible signal of annihilating dark matter.
The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector using proton-proton collision data with a centre-of-mass energy of Formula: see ...text TeV corresponding to an integrated luminosity of Formula: see textFormula: see text. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells using the anti-Formula: see text algorithm with distance parameters Formula: see text or Formula: see text, and are calibrated using MC simulations. A residual JES correction is applied to account for differences between data and MC simulations. This correction and its systematic uncertainty are estimated using a combination of in situ techniques exploiting the transverse momentum balance between a jet and a reference object such as a photon or a Formula: see text boson, for Formula: see text and pseudorapidities Formula: see text. The effect of multiple proton-proton interactions is corrected for, and an uncertainty is evaluated using in situ techniques. The smallest JES uncertainty of less than 1 % is found in the central calorimeter region (Formula: see text) for jets with Formula: see text. For central jets at lower Formula: see text, the uncertainty is about 3 %. A consistent JES estimate is found using measurements of the calorimeter response of single hadrons in proton-proton collisions and test-beam data, which also provide the estimate for Formula: see text TeV. The calibration of forward jets is derived from dijet Formula: see text balance measurements. The resulting uncertainty reaches its largest value of 6 % for low-Formula: see text jets at Formula: see text. Additional JES uncertainties due to specific event topologies, such as close-by jets or selections of event samples with an enhanced content of jets originating from light quarks or gluons, are also discussed. The magnitude of these uncertainties depends on the event sample used in a given physics analysis, but typically amounts to 0.5-3 %.
The mass of the top quark is measured in a data set corresponding to 4.6 Formula: see text of proton-proton collisions with centre-of-mass energy Formula: see text TeV collected by the ATLAS detector ...at the LHC. Events consistent with hadronic decays of top-antitop quark pairs with at least six jets in the final state are selected. The substantial background from multijet production is modelled with data-driven methods that utilise the number of identified Formula: see text-quark jets and the transverse momentum of the sixth leading jet, which have minimal correlation. The top-quark mass is obtained from template fits to the ratio of three-jet to dijet mass. The three-jet mass is calculated from the three jets produced in a top-quark decay. Using these three jets the dijet mass is obtained from the two jets produced in the Formula: see text boson decay. The top-quark mass obtained from this fit is thus less sensitive to the uncertainty in the energy measurement of the jets. A binned likelihood fit yields a top-quark mass of Formula: see text.
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