Luminosity

The determination of the integrated luminosity and its uncertainty is crucial for this measurement. Different methods are proposed to measure the integrated luminosity at CMS. The quality of the luminosity measurement is a dominate source of systematic uncertainty for the cross section measurement. During the early CMS data taking, the integrated luminosity has been determined with a precision of 11% [27]. 

A summary of the main systematic uncertainties of the measurement of the ft-quark production cross-section is shown in Table 4.6. The main contribution is due to the uncertainty of the integrated luminosity. The systematic uncertainties depend on the muon transverse momentum and pseudorapidity bin. 

Within the analysis presented here the events of interest are selected by requiring a global muon with transverse momentum pr 5GeV and pseudorapidity t) 2.1 and a TrackJet with transverse energy Ej GeV in the reconstructed event. 

The table shows the number of selected events in 1 pb, the h-fraction determined by the fit and total efficiency of the event selection for each bin. In the last two columns the calculated differential cross section as a function of the muon transverse momentum and the systematic uncertainty are given 

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The high luminosity of the instrument with no slits to limit the size of the beam. This is the Jacquinot s advantage also called etendue. ... 

The luminometer index (ASTM D 1740) is a characteristic that is becoming less frequently used. It is determined using the standard lamp mentioned above, except that the lamp is equipped with thermocouples allowing measurement of temperatures corresponding to different flame heights, and a photo-electric cell to evaluate the luminosity. The jet fuel under test is compared to two pure hydrocarbons tetraline and iso-octane to which are attributed the indices 0 and 100, respectively. The values often observed in commercial products usually vary between 40 and 70 the official specification is around 45 for TRO. 

Optional experiment. When all the air has been displaced, collect a test-tube of the gas over water (by appropriate inclination of the end of the delivery tube beneath the mouth of a test-tube filled with water and supported in a beaker of water). Observe the colour and odour of the gas. Ignite the test-tube of gas, and note the luminosity of the flame and the amount of carbon deposited. Pure acetylene is almost odourless the characteristic odour observed is due to traces of hydrides of phosphorus, arsenic and sulphur. 

Some potential problems of alcohol fuels have been addressed by a dding small amounts of gasoline or specific hydrocarbons to the fuel, reducing the flammabihty envelope and providing luminosity in case of fine. 

The fire ha2ard of methanol appears to be substantially smaller than the fire ha2ard of gasoline, although considerably greater than the fire ha2ard of diesel fuel. The lack of luminosity of a methanol flame is stiH a concern to some, and M85 (or some other methanol fuel with an additive for flame luminosity) may become the standard fuel for this reason. 

Blue gas, or blue-water gas, so-called because of the color of the flame upon burning (10), was discovered in 1780 when steam was passed over incandescent carbon (qv), and the blue-water gas process was developed over the period 1859—1875. Successfiil commercial appHcation of the process came about in 1875 with the introduction of the carburetted gas jet. The heating value of the gas was low, ca 10.2 MJ /m (275 Btu/fT), and on occasion oil was added to the gas to enhance the heating value. The new product was given the name carburetted water gas and the technique satisfied part of the original aim by adding luminosity to gas lights (10). 

Methanol, a clean burning fuel relative to conventional industrial fuels other than natural gas, can be used advantageously in stationary turbines and boilers because of its low flame luminosity and combustion temperature. Low NO emissions and virtually no sulfur or particulate emissions have been observed (83). Methanol is also considered for dual fuel (methanol plus oil or natural gas) combustion power boilers (84) as well as to fuel gas turbines in combined methanol / electric power production plants using coal gasification (85) (see Power generation). 

The formation of carbon black in a candle flame was the subject of a series of lectures in the 1860s by Michael Faraday at the Royal Institution in London (23). Faraday described the nature of the diffusion flame, the products of combustion, the decomposition of the paraffin wax to form hydrogen and carbon, the luminosity of the flame because of incandescent carbon particles, and the destmctive oxidation of the carbon by the air surrounding the flame. Since Faraday s time, many theories have been proposed to account for carbon formation in a diffusion flame, but controversy still exists regarding the mechanism (24). 

Allowance for spectral overlap, the effect of pressure, and the effect of soot luminosity would make computation tedious. Table 5-8 gives constants for use in direct calculation, for H9O/CO9 mixtures, of the product cT The product term is used because it varies much less with T than does c alone. Constants are given for mixtures, in nonradiat-ing gases, of water vapor alone, CO9 alone, and four p Jpc mixtures. 

Luminous Flames Luminosity conventionally refers to soot radiation it is important when combustion occurs under such conditions that the hydrocarbons in the flame are subject to heat in the absence of sufficient air well mixed on a molecular scale. Because soot parti-... 

With 200- Im particles and an L of 3.05 m (10 ft), the particle contribution to emissivity will be 0.31. Soot luminosity will increase this particle burnout will decrease it. 

Figure 3.16. Time-resolved shock luminosity record from one of the channels in a shock pyrometry experiment (Lyzenga and Ahrens, 1979).

Figure 8.30. Cumulative number distribution for the galaxies in the Universe. Mass is assumed proportional to absolute luminosity (units solar luminosity x 10 ). From Brown et al. (1983).

Luminosity is the amount of chemical energy in the fuel that is released as thermal radiation. 

Elevated Flares See Flares for a general definition. The elevated flare, by the use of steam injection and effective tip design, operates as a smokeless combustion device. Flaring generally is of low luminosity up to about 20 % of maximum flaring load. Steam injection tends to introduce a source of noise to the operation, and a compromise between smoke elimination and noise is usually necessary. When adequately elevated (by means of a stack) this type of flare displays the best dispersion characteristics for malodorous and toxic combustion products. Visual and noise pollution often creates nuisance problems. Capital and operating costs tend to be high, and an appreciable plant area can be rendered unavailable for plant operations and equipment because of excessive radiant heat. 

Three types of flare systems are commonly used the elevated flare, the ground flare, and the burning-pit flare. Although the three basic designs differ considerably in required capital and operating costs, selection is based primarily on pollution/public relations considerations such as smoke, luminosity, air pollution, noise and spacing factors. Table 1 summarizes the advantages and... 

Smokeless operation can generally be achieved, with essentially no noise or luminosity problems, provided that the design gas rate to the flare is not exceeded. However, since the flame is near ground level, dispersion of stack releases is poor and this may result in severe air pollution or hazard if the combustion products are toxic or in the event of flame-out. Capital and operating cost and maintenance requirements are high. 

Steam injection introduces an additional source of noise. An effective flare tip is one which achieves a good balance of smoke and luminosity reduction without exceeding acceptable noise levels. Low-frequency noise is encountered at relatively high steam to hydrocarbon ratios. 

During the test, hydrogen flow rate was raised to a maximum of approximately 55 kg/s (120 Ib/s). About 23 seconds into the experiment, a reduction in flow rate began. Three seconds later, the hydrogen exploded. Electrostatic discharges and mechanical sparks were proposed as probable ignition sources. The explosion was preceded by a fire observed at the nozzle shortly after flow rate reduction began. The fire developed into a fireball of modest luminosity, and an explosion followed immediately. 

Figure 1.2 The Hertzsprung-Russell diagram for stars with known luminosities and spectra.

Humphry Davy showed carbon particles are the source of luminosity in flames (lamp black). 

The minerals on which the work was performed during the nineteenth century were indeed rare, and the materials isolated were of no interest outside the laboratory. By 1891, however, the Austrian chemist C. A. von Welsbach had perfected the thoria gas mantle to improve the low luminosity of the coal-gas flames then used for lighting. Woven cotton or artificial silk of the required shape was soaked in an aqueous solution of the nitrates of appropriate metals and the fibre then burned off and the nitrates converted to oxides. A mixture of 99% ThOz and 1% CeOz was used and has not since been bettered. CeOz catalyses the combustion of the gas and apparently, because of the poor thermal conductivity of the ThOz, particles of CeOz become hotter and so brighter than would otherwise be possible. The commercial success of the gas mantle was immense and produced a worldwide search for thorium. Its major ore is monazite, which rarely contains more than 12% ThOz but about 45% LnzOz. Not only did the search reveal that thorium, and hence the lanthanides, are more plentiful than had previously been thought, but the extraction of the thorium produced large amounts of lanthanides for which there was at first little use. 

Helle, /. brightness, luminosity clearness, transparency vermeil (the varnish), hellen, v.t. make clear, clarify treat with vermeil. 

Heiligkeitswert, m. luminosity value. hell>matt, a. slightly dull, semidull, semimat. -rot, a. bright red light red. >rotgliihend, a. bright-red-hot. 

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