665 research outputs found
Scheme and Scale Dependence of Charm Production in Neutrino Scattering
We discuss some theoretical uncertainties in the calculation of the cross
section for charm production in charged current deep inelastic neutrino
scattering related to ambiguities in the treatment of terms which are singular
in the limit of a vanishing charm mass. In particular we compare the so-called
variable flavour scheme where these terms are absorbed in the parton
distribution functions containing the charm as an active flavour, with the
so-called fixed flavour scheme with no charm mass subtraction where the charm
appears only in the final state of fixed-order scattering matrix elements.
Using available parametrizations of parton distribution functions we find that
the two schemes lead to largely differing results for separate structure
functions whereas the differences cancel to a large extent in the total cross
section in that kinematical region which has been measured so far.Comment: 20pages, uuencoded postscript, figures include
Influences on academics' approaches to development: voices from below
The purpose of this qualitative case study research was to explore faculty-based academics’ views on what influences their behaviours and attitudes towards their development. Informed by critical realist ontology, the data collection was carried out through narrative interviews with academics in two contrasting English Universities. Findings, or areas for reflection, have emerged about the constraints and enablements academics perceive in respect of their professional development. In particular, themes such as the significance of professional status; misaligned initiatives and priorities; the influence of supportive networks; and emergent personal, individual concerns have surfaced. The conclusion is drawn that the significance of agency raises the importance of responding to the ‘voices from below’
Complete Order alpha_s^3 Results for e^+ e^- to (gamma,Z) to Four Jets
We present the next-to-leading order (O(alpha_s^3)) perturbative QCD
predictions for e^+e^- annihilation into four jets. A previous calculation
omitted the O(alpha_s^3) terms suppressed by one or more powers of 1/N_c^2,
where N_c is the number of colors, and the `light-by-glue scattering'
contributions. We find that all such terms are uniformly small, constituting
less than 10% of the correction. For the Durham clustering algorithm, the
leading and next-to-leading logarithms in the limit of small jet resolution
parameter y_{cut} can be resummed. We match the resummed results to our
fixed-order calculation in order to improve the small y_{cut} prediction.Comment: Latex2e, 17 pages with 5 encapsulated figures. Note added regarding
subsequent related work. To appear in Phys. Rev.
Evolution of Microstructure and Texture during Warm Rolling Of a Duplex Steel
The effect of warm rolling on the evolution of microstructure and texture in a duplex stainless steel (DSS) was investigated. For this purpose, a DSS steel was warm rolled up to 90 pct reduction in thickness at 498 K, 698 K, and 898 K (225 °C, 425 °C, and 625 °C). The microstructure with an alternate arrangement of deformed ferrite and austenite bands was observed after warm rolling; however, the microstructure after 90 pct warm rolling at 498 K and 898 K (225 °C and 625 °C) was more lamellar and uniform as compared to the rather fragmented and inhomogeneous structure observed after 90 pct warm rolling at 698 K (425 °C). The texture of ferrite in warm-rolled DSS was characterized by the presence of the RD (〈011〉//RD) and ND (〈111〉//ND) fibers. However, the texture of ferrite in DSS warm rolled at 698 K (425 °C) was distinctly different having much higher fraction of the RD-fiber components than that of the ND-fiber components. The texture and microstructural differences in ferrite in DSS warm rolled at different temperatures could be explained by the interaction of carbon atoms with dislocations. In contrast, the austenite in DSS warm rolled at different temperatures consistently showed pure metal- or copper-type deformation texture which was attributed to the increase in stacking fault energy at the warm-rolling temperatures. It was concluded that the evolution of microstructure and texture of the two constituent phases in DSS was greatly affected by the temperature of warm rolling, but not significantly by the presence of the other phas
Higgs-Boson Production Induced by Bottom Quarks
Bottom quark-induced processes are responsible for a large fraction of the
LHC discovery potential, in particular for supersymmetric Higgs bosons.
Recently, the discrepancy between exclusive and inclusive Higgs boson
production rates has been linked to the choice of an appropriate bottom
factorization scale. We investigate the process kinematics at hadron colliders
and show that it leads to a considerable decrease in the bottom factorization
scale. This effect is the missing piece needed to understand the corresponding
higher order results. Our results hold generally for charged and for neutral
Higgs boson production at the LHC as well as at the Tevatron. The situation is
different for single top quark production, where we find no sizeable
suppression of the factorization scale. Turning the argument around, we can
specify how large the collinear logarithms are, which can be resummed using the
bottom parton picture.Comment: 18 page
Charged Higgs Boson Production in Bottom-Gluon Fusion
We compute the complete next-to-leading order SUSY-QCD corrections for the
associated production of a charged Higgs boson with a top quark via
bottom-gluon fusion. We investigate the applicability of the bottom parton
description in detail. The higher order corrections can be split into real and
virtual corrections for a general two Higgs doublet model and into additional
massive supersymmetric loop contributions. We find that the perturbative
behavior is well under control. The supersymmetric contributions consist of the
universal bottom Yukawa coupling corrections and non-factorizable diagrams.
Over most of the relevant supersymmetric parameter space the Yukawa coupling
corrections are sizeable, while the remaining supersymmetric loop contributions
are negligible.Comment: 18 pages, v2: some discussions added, v3: published versio
Towards resolution of the enigmas of P-wave meson spectroscopy
The mass spectrum of P-wave mesons is considered in a nonrelativistic
constituent quark model. The results show the common mass degeneracy of the
isovector and isodoublet states of the scalar and tensor meson nonets, and do
not exclude the possibility of a similar degeneracy of the same states of the
axial-vector and pseudovector nonets. Current experimental hadronic and \tau
-decay data suggest, however, a different scenario leading to the a_1 meson
mass \simeq 1190 MeV and the K_{1A}-K_{1B} mixing angle \simeq (37\pm 3)^o.
Possible s\bar{s} states of the four nonets are also discussed.Comment: 22 pages, LaTe
Spallation reactions. A successful interplay between modeling and applications
The spallation reactions are a type of nuclear reaction which occur in space
by interaction of the cosmic rays with interstellar bodies. The first
spallation reactions induced with an accelerator took place in 1947 at the
Berkeley cyclotron (University of California) with 200 MeV deuterons and 400
MeV alpha beams. They highlighted the multiple emission of neutrons and charged
particles and the production of a large number of residual nuclei far different
from the target nuclei. The same year R. Serber describes the reaction in two
steps: a first and fast one with high-energy particle emission leading to an
excited remnant nucleus, and a second one, much slower, the de-excitation of
the remnant. In 2010 IAEA organized a worskhop to present the results of the
most widely used spallation codes within a benchmark of spallation models. If
one of the goals was to understand the deficiencies, if any, in each code, one
remarkable outcome points out the overall high-quality level of some models and
so the great improvements achieved since Serber. Particle transport codes can
then rely on such spallation models to treat the reactions between a light
particle and an atomic nucleus with energies spanning from few tens of MeV up
to some GeV. An overview of the spallation reactions modeling is presented in
order to point out the incomparable contribution of models based on basic
physics to numerous applications where such reactions occur. Validations or
benchmarks, which are necessary steps in the improvement process, are also
addressed, as well as the potential future domains of development. Spallation
reactions modeling is a representative case of continuous studies aiming at
understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Presuming the Status Quo? The Impact of the Statutory Presumption of Parental Involvement
The courts’ treatment of domestic abuse within private law child arrangements disputes has attracted significant concern for many years, most recently culminating in the call for major reform by the Ministry of Justice’s expert review into the courts’ practice. The Ministry of Justice has since committed to a follow-up review into the operation of the statutory presumption of parental involvement (Children Act 1989, section 1(2A)). This paper provides timely insight into the impact of this presumption in cases involving domestic abuse, presenting the findings from the first empirical study to explore its impact on the lower courts. Forty-one semi-structured interviews were conducted with judges, barristers, solicitors, Cafcass practitioners and representatives from domestic abuse organisations. It also explores perceptions of whether the statutory presumption ought to be reversed to introduce a presumption against contact in domestic abuse cases. It is argued that whilst the statutory presumption does not appear to be changing the courts’ practice, its harm lies in the reinforcement of a dominant narrative that children ‘need’ contact. Whilst a presumption against contact might not hold the answer to changing this narrative, there remains an urgent need to reappraise the approach taken to the resolution of cases involving domestic abuse
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