1,807 research outputs found
Inclusion of new LHC data in MMHT PDFs
I consider the effects of including a variety of new LHC data sets into the
MMHT approach for PDF determination. I consider the impact of fitting new LHC
and Tevatron data, which leads to clear improvements in some PDF uncertainties.
There are specific issues with ATLAS 7 TeV jet data and I include a discussion
of the treatment of correlated uncertainties and briefly the effects of NNLO
corrections. I also present preliminary results with the inclusion of the high
precison final ATLAS 7 TeV rapidity-dependent data.Comment: 6 pages. To appear in proceedings of DIS2017 Worksho
Updates of PDFs in the MSTW framework
I present results on updates on PDFs which are obtained within the general
framework which led to the MSTW2008 PDF sets. There are some theory and
procedural improvements and a variety of new data sets, including many relevant
up-to-date LHC data. A new set of PDFs is very close to being finalised, with
no significant changes expected to the preliminary PDFs shown here.Comment: 6 pages, 6 figures,Published in PoS DIS (2014
The Impact of LHC Jet and Data at up to Approximate NLO Order in the MSHT Global PDF Fit
We present an analysis of two key sets of data constraining the high
gluon at up to approximate NLO in QCD within the MSHT global PDF fitting
framework. We begin with LHC 7 and 8 TeV inclusive jet and dijet production at
both NNLO and aNLO. This makes use of the formalism established in the
previous global MSHT20aNLO PDF fit, but now considers the role of dijet
production for the first time at this order. We present a detailed comparison
of the fit quality and PDF impact for both cases, and consider the role that
electroweak corrections, and the scale choice for inclusive jet production has.
Some mild tension between these data sets in the impact on the high gluon
is seen at NNLO, but this is largely eliminated at aNLO. While a good fit
quality to the dijet data is achieved at both orders, the fit quality to the
inclusive jet data is relatively poor. We examine the impact of including full
colour corrections in a global PDF fit for the first time, finding this to be
relatively mild. We also revisit the fit to the ATLAS 8 TeV data,
considering the role that the cuts, data selection and different aspects
of the aNLO treatment have on the fit quality and PDF impact. We observe
that in all cases the aNLO fit quality is consistently improved relative
to the NNLO, indicating a clear preference for higher order theory for these
data.Comment: 32 pages, 17 figures, 10 table
Signal specific electric potential sensors for operation in noisy environments
Limitations on the performance of electric potential sensors are due to saturation caused by environmental electromagnetic noise. The work described involves tailoring the response of the sensors to reject the main components of the noise, thereby enhancing both the effective dynamic range and signal to noise. We show that by using real-time analogue signal processing it is possible to detect a human heartbeat at a distance of 40 cm from the front of a subject in an unshielded laboratory. This result has significant implications both for security sensing and biometric measurements in addition to the more obvious safety related applications
Approximate NLO Parton Distribution Functions with Theoretical Uncertainties: MSHT20aNLO PDFs
We present the first global analysis of parton distribution functions (PDFs)
at approximate NLO in the strong coupling constant ,
extending beyond the current highest NNLO achieved in PDF fits. To achieve
this, we present a general formalism for the inclusion of theoretical
uncertainties from missing higher orders (MHOs) into a PDF fit. We demonstrate
how using the currently available knowledge surrounding the next highest order
(NLO) in can provide consistent, justifiable and explainable
approximate NLO (aNLO) PDFs, including estimates for missing higher
order uncertainties (MHOUs). Specifically, we approximate the splitting
functions, transition matrix elements, coefficient functions and -factors
for multiple processes to NLO. Crucially, these are constrained to be
consistent with the wide range of already available information about NLO
to match the complete result at this order as accurately as possible. Using
this approach we perform a fully consistent approximate NLO global fit
within the MSHT framework. This relies on an expansion of the Hessian procedure
used in previous MSHT fits to allow for sources of theoretical uncertainties.
These are included as nuisance parameters in a global fit, controlled by
knowledge and intuition based prior distributions. We analyse the differences
between our aNLO PDFs and the standard NNLO PDF set, and study the impact
of using aNLO PDFs on the LHC production of a Higgs boson at this order.
Finally, we provide guidelines on how these PDFs should be be used in
phenomenological investigations.Comment: 150 pages, 48 figures, 20 tables. Updated LHAPDF Grids available
which include a correction of a minor bug in the non-singlet splitting
function leading to very small changes in fit quality and PDFs, but with no
significant changes to any results or conclusion
Updates of PDFs using the MMHT framework
We summarise recent developments in the path towards the "MMHT19" parton distribution functions. We concentrate on the extraction of the strange quark upon the improvement of theoretical calculations for NNLO charged current cross sections; the effect of an extension of our parameterisation; and the role of correlated uncertainties in some data sets which prove difficult to fit
A study of psychiatristsâ concepts of mental illness
Background: There are multiple models of mental illness that inform professional and lay understanding. Few studies have formally investigated psychiatrists' attitudes. We aimed to measure how a group of trainee psychiatrists understand familiar mental illnesses in terms of propositions drawn from different models.
Method: We used a questionnaire study of a sample of trainees from South London and Maudsley National Health Service (NHS) Foundation Trust designed to assess attitudes across eight models of mental illness (e.g. biological, psychodynamic) and four psychiatric disorders. Methods for analysing repeated measures and a principal components analysis (PCA) were used.
Results: No one model was endorsed by all respondents. Model endorsement varied with disorder. Attitudes to schizophrenia were expressed with the greatest conviction across models. Overall, the âbiologicalâ model was the most strongly endorsed. The first three components of the PCA (interpreted as dimensions around which psychiatrists, as a group, understand mental illness) accounted for 56% of the variance. Each main component was classified in terms of its distinctive combination of statements from different models: PC1 33% biological versus non-biological; PC2 12% âeclecticâ (combining biological, behavioural, cognitive and spiritual models); and PC3 10% psychodynamic versus sociological.
Conclusions: Trainee psychiatrists are most committed to the biological model for schizophrenia, but in general are not exclusively committed to any one model. As a group, they organize their attitudes towards mental illness in terms of a biological/non-biological contrast, an âeclecticâ view and a psychodynamic/sociological contrast. Better understanding of how professional group membership influences attitudes may facilitate better multidisciplinary working
Feasibility of targeted early detection for melanoma: a population-based screening study
The feasibility of targeted screening for cutaneous malignant melanoma in the UK using a postal questionnaire and invitation to screening by a consultant dermatologist was investigated in a population based cross-sectional survey. A total of 1600 people aged 25â69 years, stratified by the social deprivation score of wards within one general practice, were randomly selected from a population of 8000.1227 (77%) returned the questionnaire and 896 (56%) attended the screening clinic. Uptake was lower for men (P< 0.001), those aged under 50 (P< 0.001), people from deprived areas (P< 0.001) and skin types III and IV (men only, P< 0.001). Twenty per cent of women and 10% of men felt nervous about attending the clinic, but only 4% were worried by the questionnaire. The level of agreement between the self- and dermatologist's assessments of risk factors was best for hair colour (Kappa = 0.67, sensitivity 73% and specificity 98%). People tended to under-report their level of risk. Over 95% knew about at least one major sign, but 54% reported incorrect signs of melanoma. Targeted screening for melanoma in the UK will be hampered by difficulties in accurately identifying the target population. Strategies to improve skin self-awareness rather than screening should be developed and evaluated. © 2000 Cancer Research Campaig
The impact of the final HERA combined data on PDFs obtained from a global fit.
We investigate the effect of including the HERA run I + II combined cross section data on the MMHT2014 PDFs. We present the fit quality within the context of the global fit and when only the HERA data are included. We examine the changes in both the central values and the uncertainties in the PDFs. We find that the prediction for the data is good, and only relatively small improvements in Ï2Ï2 and changes in the PDFs are obtained with a refit at both NLO and NNLO. PDF uncertainties are slightly reduced. There is a small dependence of the fit quality on the value of Q2minQmin2 . This can be improved by phenomenologically motived corrections to FL(x,Q2)FL(x,Q2) which parametrically are largely in the form of higher-twist type contributions
- âŠ