1,020 research outputs found
Drell-Yan Non-Singlet Spin Cross Sections and Spin Asymmetry to (II)
We present predictions for the non-singlet Drell-Yan longitudinal spin cross
sections and spin asymmetry, , in proton-proton collisions at large
at the RHIC energy of 200\gev at next-to-leading order QCD. The higher
order corrections to the non-singlet polarized cross section,
, are sizeable and similar to those found for the unpolarized
cross section. The non-singlet asymmetry parameter, , is very
stable against higher order corrections and is a direct measurement of the
non-singlet (i.e. valence) polarized quark distributions within the proton.Comment: 24 pages, 13 figure
Strange quarks and lattice QCD
The last few years have seen a dramatic improvement in our knowledge of the
strange form factors of the nucleon. With regard to the vector from factors the
level of agreement between theory and experiment gives us considerable
confidence in our ability to calculate with non-perturbative QCD. The
calculation of the strange scalar form factor has moved significantly in the
last two years, with the application of new techniques which yield values
considerably smaller than believed for the past 20 years. These new values turn
out to have important consequences for the detection of neutralinos, a
favourite dark matter candidate. Finally, very recent lattice studies have
resurrected interest in the famed H-dibaryon, with modern chiral extrapolation
of lattice data suggesting that it may be only slightly unbound. We review some
of the major sources of uncertainty in that chiral extrapolation.Comment: Invited talk at the Asia-Pacific few Body Conference, Seoul Kore
Spin Dependent Drell-Yan beyond Leading Order: Non-Singlet Virtual corrections to
We present parton-level analytical results for the next-to-leading order
non-singlet virtual and real corrections to the Drell-Yan differential
cross-section. The dependence of the differential cross section on the helicity
of the initial state partons is shown explicitly (the spins of the final state
partons are summed). The calculation is implemented in dimensional
regularization within the scheme and with the t'Hooft Veltman
prescriptions for the n-dimensional . Both the polarized initial
state and the unpolarized cross sections can be obtained from our result. Our
unpolarized cross section agrees with the previous result of Ellis, Martinelli
and Petronzio in the non-singlet sector.Comment: 12 pages, 7 figures, one chapter added, change in figure
Serum vitamin D levels, diabetes and cardio-metabolic risk factors in Aboriginal and Torres Strait Islander Australians
Assesses levels of serum 25(OH)D in Aboriginal and Torres Strait Islander Australians and explores relationships between 25(OH)D and cardio-metabolic risk factors and diabetes.
Abstract
Background: Low levels of serum 25 – hydroxy vitamin D (25(OH)D), have been associated with development of type 2 diabetes and cardiovascular disease (CVD); however there are limited data on serum 25(OH)D in Indigenous Australians, a population at high risk for both diabetes and CVD. We aimed to assess levels of serum 25(OH)D in Aboriginal and Torres Strait Islander Australians and to explore relationships between 25(OH)D and cardio-metabolic risk factors and diabetes.
Methods: 592 Aboriginal and/or Torres Strait Islander Australian participants of The eGFR (estimated glomerular filtration rate) Study, a cross-sectional analysis of a cohort study performed in 2007 – 2011, from urban and remote centres within communities, primary care and tertiary hospitals across Northern Territory, Far North Queensland and Western Australia. Assessment of serum 25(OH)D, cardio-metabolic risk factors (central obesity, diabetes, hypertension, history of cardiovascular disease, current smoker, low HDL-cholesterol), and diabetes (by history or HbA1c ≥ 6.5%) was performed. Associations were explored between 25(OH)D and outcome measures of diabetes and number of cardio-metabolic risk factors.
Results: The median (IQR) serum 25(OH)D was 60 (45 – 77) nmol/L, 31% had 25(OH)D <50 nmol/L. For participants with 25(OH)D < 50 vs ≥ 50 nmol/L, cardio-metabolic risk profile differed for: diabetes (54%, 36% p < 0.001), past history of cardiovascular disease (16%, 9%, p = 0.014), waist-hip ratio (0.98, 0.92, p < 0.001), urine albumin-creatinine ratio (2.7, 1.5 mg/mmol, p < 0.001). The OR (95% CI) for diabetes was 2.02 (1.03 – 3.95) for people in the lowest vs highest tertiles of 25(OH)D (<53 vs >72 nmol/L, respectively) after adjusting for known cardio-metabolic risk factors.
Conclusion: The percentage of 25(OH)D levels <50 nmol/L was high among Aboriginal and Torres Strait Islander Australians from Northern and Central Australia. Low 25(OH)D level was associated with adverse cardio-metabolic risk profile and was independently associated with diabetes. These findings require exploration in longitudinal studies
Painting the ideal home: using art to express visions of technologically supported independent living for older people in North East England
This paper describes the investigation of the development of future technological products to support older people in everyday living through the agency of a community art group. Recent research has identified a number of challenges facing designers seeking to use traditional participatory design approaches to gather technology requirements data from older people. Here, a project is described that sought to get a group of older people to think creatively about their needs and desires for technological support through the medium of paint. The artistic expression technique described in this article allowed the identification of issues that had also been found by previous research that used a range of different techniques. This indicates that the approach shows promise, as it allows information to be gathered in an environment that is comfortable and familiar using methods already known by the participants and which they find enjoyable. It provides a complement (or possible alternative) to standard protocols and has the potential benefit of extracting even richer information as the primary task for participants is enjoyable in its own right and is not associated with an interrogative process. Furthermore, it is argued that some of the key risks of traditional approaches are lessened or removed by the naturalistic setting of this approach
Spin Dependent Drell Yan in QCD to (I). (The Non-Singlet Sector)
A study of the order corrections to the Drell Yan (non-singlet)
cross section for incoming states of arbitrary longitudinal helicities is
presented. The study is performed in the case of the transverse momentum
distributions, , of the lepton pair and extends the calculation of Ellis
Martinelli and Petronzio (EMP) to the polarized case. We use the
scheme and the t'Hooft-Veltman regularization for the helicity projectors. From
our results one can obtain the bulk of the totally inclusive NNLO cross section
for the production of a Drell Yan pair in the non-singlet sector by a simple
integration over the heavy photon momentum. We show that in the
helicity is not conserved, unless a finite renormalization is done to reenter
into a physical scheme (). This aspect of the calculation follows
the same trend as in polarized production of single and double photon to
. In the unpolarized limit we reproduce all the results of EMP.Comment: 39 pages, 7 figures (included
New Observational Bounds to Quantum Gravity Signals
We consider a new set of effects arising from the quantum gravity corrections
to the propagation of fields, associated with fluctuations of the spacetime
geometry. Using already existing experimental data, we can put bounds on these
effects that are more stringent by several orders of magnitude than those
expected to be obtained in astrophysical observations. In fact these results
can be already interpreted as questioning the whole scenario of linear (in
) corrections to the dispersion relations for free fields in Lorentz
violating theories.Comment: Latex, to be published in PR
Recent results on nucleon sigma terms in lattice QCD
It has proven a significant challenge to experiment and phenomenology to
extract precise values of the nucleon sigma terms. This difficulty opens the
window for lattice QCD simulations to lead the field in resolving this aspect
of nucleon structure. Here we report on recent advances in the extraction of
nucleon sigma terms in lattice QCD. In particular, the strangeness component is
now being resolved to a precision that far surpasses best phenomenological
estimates.Comment: 6 pages, 1 figure; prepared for Proc. 4th Int Symposium on Symmetries
in Subatomic Physics (SSP2009), Taipei, Taiwan, June 2-5 200
Fluctuation Theorems for Entropy Production and Heat Dissipation in Periodically Driven Markov Chains
Asymptotic fluctuation theorems are statements of a Gallavotti-Cohen symmetry
in the rate function of either the time-averaged entropy production or heat
dissipation of a process. Such theorems have been proved for various general
classes of continuous-time deterministic and stochastic processes, but always
under the assumption that the forces driving the system are time independent,
and often relying on the existence of a limiting ergodic distribution. In this
paper we extend the asymptotic fluctuation theorem for the first time to
inhomogeneous continuous-time processes without a stationary distribution,
considering specifically a finite state Markov chain driven by periodic
transition rates. We find that for both entropy production and heat
dissipation, the usual Gallavotti-Cohen symmetry of the rate function is
generalized to an analogous relation between the rate functions of the original
process and its corresponding backward process, in which the trajectory and the
driving protocol have been time-reversed. The effect is that spontaneous
positive fluctuations in the long time average of each quantity in the forward
process are exponentially more likely than spontaneous negative fluctuations in
the backward process, and vice-versa, revealing that the distributions of
fluctuations in universes in which time moves forward and backward are related.
As an additional result, the asymptotic time-averaged entropy production is
obtained as the integral of a periodic entropy production rate that generalizes
the constant rate pertaining to homogeneous dynamics
Aspects of Soft and Spontaneous CP Violation
We study four different models for CP violation: the standard (KM) model, the
aspon model of spontaneous breaking and two models of soft breaking. In all
except the standard model, the strong CP problem is addressed and solved.
Testable predictions for the area of the unitarity triangle and for
(epsilon'/epsilon)_K are emphasized. The issue of CP violation may well become
the first place where the standard model of particle theory is shown
definitively to be deficient. There are two reasons for expecting this to
happen: (1) the strong CP problem is still not understood in the unadorned
standard model and (2) the KM mechanism, although unquestionably present, may
not provide the full explanation of epsilon_K and (epsilon'/epsilon)_K.Comment: 24 pages LaTeX including 4 figures. Minor modification to analysis of
lower bound for d_n, summarized in new Table I
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