1,927 research outputs found
Top Quark Pair Production Cross Section and Forward-Backward Asymmetry at the Tevatron
We present recent results on top quark pair production cross section and
forward-backward asymmetry at the Tevatron. Three new cross section
measurements from CDF and one new measurement from DO are presented that
utilize the full dataset available. A new DO top cross section combination
gives a ttbar production cross section of sigma_ttbar = 7.83 + 0.46-0.45 (stat)
+ 0.64-0.53 (syst) +-0.48 (lumi). The new CDF cross section combination for
ttbar production is found to be 7.0 +- 0.3 (stat) +- 0.4 (syst) +- 0.4 (lumi)
pb giving a total uncertainty of 9%, very close to the that of the current best
theoretical predictions. It is important to measure the top cross section in as
many different channels as possible and investigate their compatibility. This
is useful as new physics might show up differently in the different channels.
Thus any significant discrepancy could be a sign of new physics. Three new
measurements of the forward-backward asymmetry are also presented. The two CDF
measurements unfold the observed asymmetry back to parton level in order to
directly compare the values obtained with theoretical predictions. The DO
measurement is not unfolded and therefore does not depend on the specific
method used for unfolding.Comment: Parallel talk at ICHEP08, Philadelphia, USA, July 200
Lessons from the Long View: Observations and Insights on Developments in Private Practice from the 30 Year History of One Independent Textile Conservation Studio
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Lessons from the Long View: Observations and Insights on Developments in Private Practice from the 30 Year History of One Independent Textile Conservation Studio
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Fragmentation, underlying event and jet shapes at the Tevatron
Experimental tests of QCD processes, in particular fragmentation, underlying event and jet shape studies, are not only essential in their own right to allow an improved understanding of the theoretical models and their limitations but they are also important in searches for new physics. Recent results of such tests are presented here. All the results show good agreement between the latest theoretical models or Monte Carlo predictions
Data release notes : UK Geoenergy Observatories Glasgow Geothermal Energy Research Field Site (GGERFS) ground gas, 2018 and 2019 surveys
In 2014, the British Geological Survey (BGS) and the Natural Environment Research Council
(NERC) were tasked with developing new centres for research into the sub-surface environment
to aid the responsible development of new low-carbon energy technologies in the United Kingdom
(UK) and internationally.
Under the United Kingdom Geoenergy Observatories (UKGEOS) project, two sites were chosen,
including the Glasgow Geothermal Energy Research Field Site (GGERFS) in the
Cuningar Loop-Dalmarnock area in the east of Glasgow (Figure 1). The aims of the GGERFS
facility include de-risking technical aspects of mine water geothermal to assess the feasibility of
extracting/storing heat energy in an urbanised former coal mine setting (Monaghan 2019;
Monaghan et al. 2017; Monaghan et al. 2018).
The initial phase of the GGERFS project entails installing a network of boreholes into the
superficial deposits and bedrock in the Cuningar Loop-Dalmarnock area of Glasgow to
characterise the geological and hydrogeological setting and assess the potential for shallow
geothermal energy. The borehole network is also designed for baseline monitoring to assess the
environmental status before and during the lifetime of the project.
A ground gas baseline is considered important at the GGERFS site to enable us to determine if
there are significant ongoing ground gas contributions from sources such as (i) leakage from mine
workings/features related to legacy mine workings (ii) gas generated from components of the made
ground (building rubble, mine water, other waste) and (iii) natural soil processes. The made ground
at Cuningar Loop is known to have been formed from a range of prior land uses (see Ramboll
2018 a, b) and is commonly around 10 m thick.
Ground gas measurement is an important tool for monitoring geoenergy sites since sensitive
measurements of, for example, CO2, CH4 and associated gases can be made directly within the
biosphere in which we live. Monitoring of ground gas in the vadose zone has been undertaken as
part of a broader GGERFS environmental monitoring effort that includes groundwater, soil and
surface water chemistry, ground movement and seismicity. The intention of ground gas
monitoring, indeed the environmental monitoring effort as a whole, is to characterise pre-existing
i.e. pre-operational or baseline conditions, particularly with respect to former coal mining, building
demolition, waste disposal/landfill, or other industrial activities, before significant development
occurs in relation to GGERFS. As such, it should be noted that the August 2018 survey precedes
any development of GGERFS and can be considered ‘baseline’ in the conventional sense, whereas
the May and October 2019 surveys were conducted alongside site construction but ahead of site
operation.
Approaches to monitoring ground gas may include long term continuous monitoring using
permanently deployed instruments, and discrete surveys involving mobile, wide area screening
techniques (for example open path laser, cavity ring down laser) to augment high density grids of
detailed point measurements.
Point measurement data from ground gas surveys conducted at the Glasgow Geothermal Energy
Research Field Site (GGERFS) in August 2018, and May and October 2019 are reported. Ground
gas is defined here as:
a. gas concentrations in the shallow (c.70-100 cm below ground level) unsaturated zone of
the subsurface, and
b. gas flux at the soil-atmosphere interfac
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