Signal Purity Research Articles

Measurement of the top-quark pair-production cross section in events with two leptons and bottom-quark jets using the full CDF data set

We present a measurement of the top-quark pair production cross-section in proton-antiproton collisions at $\sqrt{s}$=1.96 TeV. The data were collected at the Fermilab Tevatron by the CDF II detector and correspond to an integrated luminosity of 8.8 fb$^{-1}$, representing the complete CDF Run II data set. We select events consistent with the production of top-quark pairs by requiring the presence of two reconstructed leptons, an imbalance in the total event transverse momentum, and jets. At least one jet is required to be identified as consistent with the fragmentation of a bottom quark using a secondary-vertex-finding algorithm. The 246 candidate events are estimated to have a signal purity of 91%. We measure a cross section of $\sigma_{\ttbar}$ = 7.09 $\pm$ 0.84 pb, assuming a top-quark mass of 172.5 GeV/$c^{2}$. The results are consistent with the standard model as predicted by next-to-leading-order calculations.

Simulation of the Expected Performance of a Seamless Scanner for Brain PET Based on Highly Pixelated CdTe Detectors

The aim of this work is the evaluation of the design for a nonconventional PET scanner, the voxel imaging PET (VIP), based on pixelated room-temperature CdTe detectors yielding a true 3-D impact point with a density of 450 channels/cm(3), for a total 6 336 000 channels in a seamless ring shaped volume. The system is simulated and evaluated following the prescriptions of the NEMA NU 2-2001 and the NEMA NU 4-2008 standards. Results show that the excellent energy resolution of the CdTe detectors (1.6% for 511 keV photons), together with the small voxel pitch (1 × 1 × 2 mm(3)), and the crack-free ring geometry, give the design the potential to overcome the current limitations of PET scanners and to approach the intrinsic image resolution limits set by physics. The VIP is expected to reach a competitive sensitivity and a superior signal purity with respect to values commonly quoted for state-of-the-art scintillating crystal PETs. The system can provide 14 cps/kBq with a scatter fraction of 3.95% and 21 cps/kBq with a scatter fraction of 0.73% according to NEMA NU 2-2001 and NEMA NU 4-2008, respectively. The calculated NEC curve has a peak value of 122 kcps at 5.3 kBq/mL for NEMA NU 2-2001 and 908 kcps at 1.6 MBq/mL for NEMA NU 4-2008. The proposed scanner can achieve an image resolution of ~ 1 mm full-width at half-maximum in all directions. The virtually noise-free data sample leads to direct positive impact on the quality of the reconstructed images. As a consequence, high-quality high-resolution images can be obtained with significantly lower number of events compared to conventional scanners. Overall, simulation results suggest the VIP scanner can be operated either at normal dose for fast scanning and high patient throughput, or at low dose to decrease the patient radioactivity exposure. The design evaluation presented in this work is driving the development and the optimization of a fully operative prototype to prove the feasibility of the VIP concept.

Search for the neutral Supersymmetric Higgs boson with the CMS experiment at LHC

The search of neutral Higgs boson in two different decay channels, a pair of τ leptons and a pair of b-quarks, is presented. The search is performed in the context of the Minimal Supersymmetric Standard Model (MSSM), using data collected by the CMS experiment at the LHC during 2011–12 at a center-of-mass energy of 7–8 TeV. In the τ decay four independent pair final states, where one or both τs decay leptonically, are studied. In the bb̄ channel we look for final states with two high energetic jets plus a third jet, exploiting the production in association with b-quarks to enhance the signal purity in the selections of events. A description of the analyses strategies adopted for the two channels is provided. The results are presented and interpreted in the scenario of the MSSM framework.

Signal-purity-spectrum-based colored deconvolution

Signal to noise ratio (SNR) and resolution are two important but contradictory characteristics used to evaluate the quality of seismic data. For relatively preserving SNR while enhancing resolution, the signal purity spectrum is introduced, estimated, and used to define the desired output amplitude spectrum after deconvolution. Since a real reflectivity series is blue rather than white, the effects of white reflectivity hypothesis on wavelets are experimentally analyzed and color compensation is applied after spectrum whitening. Experiments on real seismic data indicate that the cascade of the two processing stages can improve the ability of seismic data to delineate the geological details.

Ultralow-Power Ku-Band Dual-Feedback Armstrong VCO With a Wide Tuning Range

Here, we investigate the design of a Ku-band Armstrong voltage-controlled oscillator (VCO) utilizing dual transformer feedback for low-voltage low-power operation. The primary transformer feedback between the drain and the source of the VCO increases the output voltage swing under low supply voltage. With the secondary transformer feedback, g_m-boosting is obtained by the coupling between the drain and the gate of the Armstrong VCO. Combined with transformer feedback, g_m-boosting further reduces the negative transconductance required for oscillation startup, enabling ultralow-power operation. Thus, the proposed Armstrong VCO with dual feedback operates at 0.4 V with power consumption as low as 600 W. Under this condition, the measured phase noise of the VCO is -100.6 dB/Hz at 1-MHz offset from a 14.1-GHz carrier. The results show that the proposed VCO is suitable for very low-power applications requiring high signal purity.

A new method for blind extraction of cyclostationary signals

This paper illustrates the significance of the purity of cyclostationary signals and presents a new method for blind extraction of these signals. The advantage of the method can not only extract the cyclostationary signals from low order to high order in turn but also perform algorithm without knowing cyclic frequencies of the extracted signals. The effectiveness of the proposed method is finally demonstrated by computer simulations and experiments.

Quantification of Cynaropicrin in Artichoke Leaf Extracts by1H NMR Spectroscopy

The quantification of cynaropicrin in artichoke leaf extracts (ALE) by means of quantitative ¹H NMR was performed. The method relies on solid phase extraction for sample preparation and spectra acquisition in DMSO- D₆ containing anthracene as the internal standard. The obtained ¹H NMR spectra revealed excellent signal purity for H-13(b) of cynaropicrin, which was thus chosen for quantification. Validation was performed in terms of selectivity, linearity, precision, accuracy, and robustness. The content of cynaropicrin in the analyzed samples showed considerable variation, ranging from non detectable to 1.6 %. The NMR approach does not rely on external calibration, which represents the major advantage compared to traditional approaches based on HPLC.

Measurement ofνμ-induced charged-current neutral pion production cross sections on mineral oil atEν∈0.5–2.0 GeV

Using a custom 3 \v{C}erenkov-ring fitter, we report cross sections for $\nu_\mu$-induced charged-current single $\pi^0$ production on mineral oil (\chtwo) from a sample of 5810 candidate events with 57% signal purity over an energy range of $0.5-2.0$GeV. This includes measurements of the absolute total cross section as a function of neutrino energy, and flux-averaged differential cross sections measured in terms of $Q^2$, $\mu^-$ kinematics, and $\pi^0$ kinematics. The sample yields a flux-averaged total cross section of $(9.2\pm0.3_{stat.}\pm1.5_{syst.})\times10^{-39}$cm$^2$/CH$_2$ at mean neutrino energy of 0.965GeV.

A Frequency-Multiplied Source With More Than 1 mW of Power Across the 840–900-GHz Band

We report on the design, fabrication, and characterization of an 840-900-GHz frequency multiplier chain that delivers more than 1 mW across the band at room temperature with a record peak power of 1.4 mW at 875 GHz. When cooled to 120 K, the chain delivers up to 2 mW at 882 GHz. The chain consists of a power amplifier module that drives two cascaded frequency triplers. This unprecedented output power from an electronic source is achieved by utilizing in-phase power-combining techniques. The first stage tripler uses four power-combined chips while the last stage tripler utilizes two power-combined chips. The source output was analyzed with a Fourrer transform spectrometer to verify signal purity.

Reducing multi-dimensional information into a 1D histogram

We present two methods for reducing multidimensional information to one dimension for ease of understand or analysis while maintaining statistical power. While not new, dimensional reduction is not greatly used in high-energy physics and has applications whenever there is a distinctive feature (for instance, a mass peak) in one variable but when signal purity depends on others; so in practice in most of the areas of physics analysis. While both methods presented here assume knowledge of the background, they differ in the fact that only one of the methods uses a model for the signal, trading some increase in statistical power for this model dependence.

Survey and qualification of internal standards for quantification by 1H NMR spectroscopy

In quantitative NMR (qNMR) selection of an appropriate internal standard proves to be crucial. In this study, 25 candidate compounds considered to be potent internal standards were investigated with respect to the ability of providing unique signal chemical shifts, purity, solubility, and ease of use. The (1)H chemical shift (delta) values, assignments, multiplicities and number of protons (for each signal), appropriateness (as to be used as internal standards) in four different deuterated solvents (D(2)O, DMSO-d(6), CD(3)OD, CDCl(3)) were studied. Taking into account the properties of these 25 internal standards, the most versatile eight compounds (2,4,6-triiodophenol, 1,3,5-trichloro-2-nitrobenzene, 3,4,5-trichloropyridine, dimethyl terephthalate, 1,4-dinitrobenzene, 2,3,5-triiodobenzoic acid, maleic acid and fumaric acid) were qualified using both differential scanning calorimetry (DSC) and NMR spectroscopy employing highly pure acetanilide as the reference standard. The data from these two methods were compared as well as utilized in the quality assessment of the compounds as internal standards. Finally, the selected internal standards were tested and evaluated in a real case of quantitative NMR analysis of a paracetamol pharmaceutical product.

Advanced Instrument For Field Calibration of Electrical Energy Meters

Calibration of electrical energy meters is coming up as a metrological concern. The latest European Union (EU) directives about measuring instruments adopted for commercial transactions state that their accuracy has to be verified in actual operating conditions. This requirement is leaving all laboratories involved in energy meter calibration in serious difficulty because this kind of metrological verification is, at the moment, still not fully developed or even clarified in all involved aspects. In this paper, a measurement equipment for the calibration of energy meters is presented. Its structure and metrological characterization are discussed. To improve its performances without increasing its costs, two online digital compensation procedures have been realized and are shown: one increases the spectral purity of test signals and one corrects the transducer frequency response. Experimental results relating metrological characterization have shown that the so-realized calibrator is suitable for the onsite calibration of energy meters.

RF optoelectronic oscillator using a directly modulated semiconductor laser and a fiber optical ring filter

AbstractIn this article we present an RF optoelectronic oscillator based on directly modulated laser diode and an all optical RF filter. The system is modeled and simulated using standard simulators. Using commercial modules and standard single mode fiber, the implemented system shows an RF oscillation with 9.8 dBm at 1.1 GHz. We also show that the use of an all optical RF filter allows a sidemode suppression ratio more than 50 dB without affecting the signal purity. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 470–475, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24069

A computational study of tomographic measurement of carbon monoxide at minor concentrations

In order to develop a chemical species tomography system, this paper carries out various computational steps to address the problem of measuring minor species concentration using single-pass, short path-length absorption techniques in the mid-infrared. It focuses on the imaging of carbon monoxide (CO) in combustion exhaust as a case study, with an average concentration of 10 ppm over a 50 mm diameter cross-section, taking account of the presence of other absorbing species. CO absorption transitions R6, R7, R9 and R10 are identified as possible measurement targets. The joint effects of spectral absorption linewidth and laser source linewidth are considered at length, resulting in recommendations for laser linewidth to achieve appropriate levels of CO absorption signal purity. Measurement strategies are considered for achievement of the necessary sensitivity, noise and bandwidth performance. A feasible beam arrangement for tomographic imaging is discussed, providing 48 measurements of path concentration integral. Representative phantom reconstructions are presented, with encouraging results for application to such dynamic gaseous subjects.

Generation of two-mode optical signals with broadband frequency tunability and low spurious signal level

For continuous millimeter and terahertz-wave applications, a two-mode optical signal generation technique that uses two arrayed waveguide gratings and two optical switch units is presented. In addition to easy and fast operation, this scheme offers broadband frequency tunability and high signal purity with a low spurious mode level. Mode spacing, which corresponds to the frequency of the generated MM/THz-wave signal after photomixing, was successfully swept in the range of 200 ~ 550 GHz and the optical spurious mode suppression ratio higher than 25 dBc was achieved. In addition, spurious modes characteristics were investigated by using second harmonic generation (SHG) autocorrelation methods for several frequencies.

DETERMINATION OF |Vub| FROM TAGGED AND UNTAGGED $B \overline{B}$ EVENTS WITH THE BABAR DETECTOR

Measurements of charmless semileptonic B-meson decays and the CKM matrix element |Vub| are reported based on a sample of 88 million [Formula: see text] events recorded with the BABAR detector. Decays B → Xuℓν are selected from both tagged and untagged [Formula: see text] events and separated from the dominant charm background, B → Xcℓν, using different kinematic variables: the lepton momentum Eℓ, the squared four-momentum transfer q2, and the hadronic mass mX. The extrapolation to the total decay rate to determine |Vub| is performed for different theoretical models. We have also measured branching ratios for the exclusive semileptonic decays B → π(ρ,ω,η,η′,a0)ℓν, where a high signal purity is reached by fully or partially reconstructing the second B meson.

Polarized light detection in spiders.

We describe here the detection of polarized light by the simple eyes of spiders. Using behavioural, morphological, electrophysiological and optical studies, we show that spiders have evolved two different mechanisms to resolve the e-vector of light. Wolf spiders (Lycosidae), are able to turn in response to rotation of a polarized pattern at the zenith of their visual fields, and we also describe a strip in the ventral retina of the principal (anterio-median) eyes that views this location and has receptors tiered into two layers. This provides each pair of receptors with a similar optical solution to that provided by the 'dorsal rim area' of the insect compound eye. In contrast, gnaphosid spiders have evolved a pair of lensless secondary eyes for the detection of polarized light. These two eyes, each sensitive to orthogonal directions of polarization, are perfectly designed to integrate signals from the larger part of the sky and cooperate to analyse the polarization of light. Built-in polarizers help to improve signal purity. Similar organisation in the eyes of several other spider families suggests that these two mechanisms are not restricted to only a few families.

Signal identification in size-exclusion HPLC-ICP-MS chromatograms of plant extracts by electrospray tandem mass spectrometry (ES MS/MS)

Pneumatically-assisted electrospray (ion-spray®) tandem mass spectrometry (ES-MS/MS) was evaluated for the identification of cadmium binding ligands in complexes detected in extracts of plant cell cultures by size-exclusion HPLC (SEHPLC) with ICP-MS detection. The metal-containing fractions were heartcut, purified by reversed-phase chromatography, and analysed by ES-MS/MS. The purity and identity of signals in ES-MS/MS spectra were further confirmed by collision induced dissociation (CID)-MS. The different peaks in SEHPLC-ICP-MS turned out to contain identical ligands at different ratios. On the other hand, a single SEHPLC-ICP-MS chromatographic signal was demonstrated to contain a number of complexes with ligands varying in terms of amino-acid chain length, amino-acid sequence and stoichiometry. Whereas the particular ligands (phytochelatins modified on the C-terminal amino-acid) could be identified, the complexity of equilibria within the isolated fraction prevented the elucidation of the stoichiometry of the complexes formed. The results question the validity of signal identification in SEHPLC-ICP-MS by elution volume matching with standards unless the chromatographic purity of peaks is demonstrated.

Optimization of DTV Signals within a Transmission Plant

With the transition to digital television (DTV), some of the old challenges in maintaining signal purity through a high-power transmitter become more complex, as the signal can be much less tolerant to distortions. Comark has researched new technologies to minimize and compensate for distortions in DTV transmitters for over four years. This paper will explain why these distortions are so important and what methods Comark is using in its new DTV transmitters to insure that the highest possible quality signal is transmitted at all times. Real world examples from high-power DTV transmitter installations will be presented and explained.

Evaluation of 26Mg stable isotope as an in vivo tracer of magnesium transport for SIMS ion microscopy imaging studies.

Isotopic detection with high sensitivity, one of the most important features of ion microscopy, allows the in vivo application of stable isotopes as tracers for unravelling smaller tissue structures implicated with transport capabilities. The evaluation of the mass interferences associated with a particular mass of secondary ion signals is a necessity for tracer studies with stable isotopes. We have tested the feasibility of 26Mg stable isotope as a tracer of magnesium transport in the killifish. The fish were given a single intraperitoneal injection of 3 mumol 26MgCl2.6H2O (99.5% 26Mg enrichment), and the renal distribution of 26Mg was examined in frozen freeze-dried cryosections with ion microscopy. High-mass resolution analyses were performed to evaluate the purity of positive secondary ion signals of the nominal masses 24, 25 and 26 in order to assess the purity of 24Mg, 25Mg and 26Mg signals, respectively, in kidneys of control and 26Mg-injected fish. In kidneys of control fish, the purities of 24Mg, 25Mg and 26Mg signals were approximately 97%, 82% and 90%, respectively. In fish that were injected with 26Mg stable isotope, an enhancement of 26Mg+ secondary ion signals was observed with signal purity reaching 95%. These observations indicate that 26Mg can be used successfully as a tracer of magnesium transport in animal models. To uncover the distribution of tracer 26Mg from the naturally abundant background of this isotope, a pixel-by-pixel digital subtraction is applied to the raw ion microscopy mass 26 image.