Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Determination of the strong coupling constant αs from transverse energy–energy correlations in multijet events at s√=8 TeV using the ATLAS detector

Measurements of transverse energy–energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to s√=8 TeV proton–proton collisions with an integrated luminosity of 20.2 fb−1 . The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of αs(μ) predicted in QCD up to scales over 1 TeV . A global fit to the transverse energy–energy correlation distributions yields αs(mZ)=0.1162±0.0011(exp.) +0.0084−0.0070(theo.) , while a global fit to the asymmetry distributions yields a value of αs(mZ)=0.1196±0.0013(exp.) +0.0075−0.0045(theo.)

Oxygen deficiency in Graham\u27s Ratio evaluation

There are a number of indicators used to determine the level of coal oxidation in underground coal mines. The common indicator Graham’s ratio is the amount of carbon monoxide produced in proportion to the amount of oxygen consumed by the coal. The more carbon monoxide produced relative to the oxygen consumed (oxygen deficiency), the greater the intensity of the coal’s reaction. Graham’s ratio is often used as a trigger for Trigger Action Response Plans (TARPs) for the management of spontaneous combustion. This emphasises the importance of accurate measurement of oxygen deficiency and ability to successfully determine the status of underground atmosphere. Samples with a similar composition to air may return a negative or minuscule measured oxygen deficiency unsuitable for Graham’s ratio. The same problem is identified in samples diluted with seam gas or when there are inaccuracies in other measured components when nitrogen is calculated by difference. If the oxygen deficiency is inadequate and insufficient, the Graham’s ratio result can be overestimated and trigger a TARP level. If the minimum oxygen deficiency is set to inadequate level, in order to avoid alarm “fatigue”, there is a concern that valid data may be excluded from interpretation. The optimal value which indicates the beginning of spontaneous combustion event is site specific. This paper will present the case studies where the oxygen deficiency minimum limit has been adjusted to suit the mine site actual real data and analysis technique

Review of oxygen deficiency requirements for graham’s ratio

Graham’s ratio is a commonly used indicator for measuring the intensity of the oxidation of coal in underground mine atmospheres. Successful measurement of oxygen deficiency is critical in order to generate relevant results, as well as meaningful data trends. Graham’s ratio is often used as a trigger for Trigger Action Response Plans (TARP) for the management of spontaneous combustion. If a Graham’s ratio is calculated where there is an insufficient oxygen deficiency the result can be overestimated and trigger a TARP level. Mitchell (1996) and the NSW Mines Rescue gas detection and emergency preparedness book (2014) has previously identified issues with using Graham’s Ratio when the oxygen deficiency is less than 0.3%, due to analytical limitations. This issue is often encountered in samples in which the composition is close to air due to the low inherent oxygen deficiency of the sample. The same problem is identified in samples diluted with seam gas. Errors in oxygen deficiency can be compounded by inaccuracies in other measured components when nitrogen is calculated by difference. A concern with applying the 0.3% oxygen deficiency requirement (minimum limit) to dilute or close to air samples is that valid data may be excluded from interpretation. This paper will review the magnitude and application of minimum oxygen deficiency required for a consistent valid measurement of Graham’s ratio. This will be done across a range of samples using real data from a number of modern analysis techniques in underground coal mines

Operational Considerations for Tube Bundle Gas Monitoring Systems

Tube bundle gas monitoring systems are now common practice in the Australian underground coal mining industry. Systems are in operation at all underground coal mines in Queensland, all longwall coal mines in New South Wales, and most bord and pillar coal mines in New South Wales. This paper utilises the information assessed by Simtars as part of the project “The Application of Tube Bundle Systems in the Prevention of Mine Fires and Explosions and Post-Event Response”, prepared for the National Institute for Occupational Safety and Health (NIOSH), under contract number 200-2013-56949. The operational considerations and decisions required to ensure the optimum operation of the system will be outlined. Installation, maintenance, training requirements, alarm settings and interpretation of the gas results will be taken into account. Practical solutions and explanations will be provided, drawing on Australian and overseas experience, as well as information publicised by the National Coal Board in the United Kingdom and the United States Bureau of Mines (USBM)

Filter requirements for Graham’s ratio oxygen deficiency

ABSTRACT: Graham’s ratio (GR) is used to calculate the amount of carbon monoxide produced in proportion to the amount of oxygen consumed by the coal. It is a useful indicator for Coal Mines to determine the level of coal oxidation and to respond accordingly in the event of spontaneous combustion. The intensity of the coal reaction is related to the carbon monoxide produced and the oxygen consumed (oxygen deficiency). Graham’s ratio is very important as it is often used as a trigger for Trigger Action Response Plans (TARPs) for the management of spontaneous combustion. Samples with a similar composition to air may return a negative or minuscule measured oxygen deficiency unsuitable for Graham’s ratio. The same problem is identified in samples diluted with seam gas or when there are inaccuracies in other measured components when nitrogen is calculated by difference and not directly measured. The issue arises when oxygen deficiency is inadequate and insufficient, where the GR result can be overestimated and trigger a TARP level. Some mine sites introduced a filter for minimum oxygen deficiency value to avoid alarm “fatigue” for a Control Room Operator (CRO). There are cases where this minimal value is not suitable and where valid oxygen values have been filtered. This paper will present the case studies where the filter value was adjusted to suit the mine site actual real data and analysis technique