1,464 research outputs found
Structure Functions are not Parton Probabilities
The common view that structure functions measured in deep inelastic lepton
scattering are determined by the probability of finding quarks and gluons in
the target is not correct in gauge theory. We show that gluon exchange between
the fast, outgoing partons and target spectators, which is usually assumed to
be an irrelevant gauge artifact, affects the leading twist structure functions
in a profound way. This observation removes the apparent contradiction between
the projectile (eikonal) and target (parton model) views of diffractive and
small x_{Bjorken} phenomena. The diffractive scattering of the fast outgoing
quarks on spectators in the target causes shadowing in the DIS cross section.
Thus the depletion of the nuclear structure functions is not intrinsic to the
wave function of the nucleus, but is a coherent effect arising from the
destructive interference of diffractive channels induced by final state
interactions. This is consistent with the Glauber-Gribov interpretation of
shadowing as a rescattering effect.Comment: 35 pages, 8 figures. Discussion of physical consequences of final
state interactions amplified. Material on light-cone gauge choices adde
Cost effectiveness of community leg ulcer clinics: randomised controlled trial
Objectives: To establish the relative cost effectiveness of community leg ulcer clinics that use four layer
compression bandaging versus usual care provided by district nurses.
Design: Randomised controlled trial with 1 year of follow up.
Setting: Eight community based research clinics in four trusts in Trent.
Subjects: 233 patients with venous leg ulcers allocated at random to intervention (120) or control (113) group.
Interventions: Weekly treatment with four layer bandaging in a leg ulcer clinic (clinic group) or usual care at home by the district nursing service (control group).
Main outcome measures: Time to complete ulcer healing, patient health status, and recurrence of ulcers. Satisfaction with care, use of services, and personal costs were also monitored.
Results: The ulcers of patients in the clinic group tended to heal sooner than those in the control group over the whole 12 month follow up (log rank P=0.03). At 12 weeks, 34% of patients in the clinic group were healed compared with 24% in the control. The crude initial healing rate of ulcers in intervention compared with control patients was 1.45 (95% confidence interval 1.04 to 2.03). No significant differences were found between the groups in health status. Mean total NHS costs were £878.06 per year for the clinic group and £859.34 for the control (P=0.89).
Conclusions: Community based leg ulcer clinics with trained nurses using four layer bandaging is more effective than traditional home based treatment. This benefit is achieved at a small additional cost and could be delivered at reduced cost if certain service configurations were used
Space-time properties of the higher twist amplitudes
A consistent and intuitive description of the twist-4 corrections to the
hadron structure functions is presented in a QCD-improved parton model using
time-ordered perturbative theory, where the collinear singularities are
naturally eliminated. We identify the special propagators with the backward
propagators of partons in time order.Comment: 18 Pages, Latex, 8 Ps figures, To appear in Phys. Rev.
Evolution of Catholic Marriage Morality in the Twentieth Century from a Baby-Making Contract to a Love-Making Covenant - Part II: Code of Cannon Law to Vatican II
Sexual ethics in the West has been evolving, in practice and in theory, over the last century. The official Catholic Church teaching was challenged by many Christian churches and by the changing culture of the West. The Vatican insisted that no change could be made in its timeless truths. Nevertheless, each challenge required ever more sophisticated and convoluted arguments. The impetus for change came through the Western shift from seeing sexual activity as a procreative act toward viewing it as a way for husbands and wives (and gradually also any consenting adult) to express and deepen love. The Second Vatican Council accepted this new view, but subsequently the official teaching became more strict, insisting that both procreation and marital love-making must be present. The teaching of Pope Paul VI prohibiting contraception was the proverbial straw that broke the camel’s back for many Catholics. They abandoned the official teaching, recognizing that it was the new personalist view itself that complicated the meaning of marriage. Subsequently, the Canon Law tried reestablish the validity of loveless sex in marriage–the dominant view through the centuries. That move was rejected
Evolution of Catholic Marriage Morality in the Twentieth Century from a Baby-Making Contract to a Love-Making Covenant - Part I: Era of John Paul II
For nearly a century Catholic Church teaching on Sexuality evolved greatly. Changes in science and the teaching of other Christian churches begged for a fresh start. John Paul II, elected pope in 1978, attempted to update that teaching by providing new background arguments, without changing any of the strictures in the foreground. John Paul II insisted on necessity of total love, allowing for no exceptions. He claimed that divorce was impossible because the spouses retained no control over their marriage promises. Homosexual activity was judged to be morally deficient. Likewise the recent arrival of reproductive technology was largely condemned for breaking the sexual unity of the spouses. But fertile sexual activity was newly appreciated as the important activity of spouses cooperating with the creative activity of God. In the twenty-first century the Church’s official teachings continues to be reformed, but their relevance is widely questioned as social norms continue to drastically change
Simulation of deposit formation in particle laden flows: thermal properties
Fatty deposits formed on arterial walls lead to atherosclerosis but it is the interplay between these deposits and the vessel walls which governs the growth of plaque formation. Cells in the vessel walls trigger the body's defenses and through a series of mechanisms lead to the promotion of plaque growth. Crucially however the vast majority of acute coronary syndromes such as, myocardial infarction, and sudden ischaemic cardiac death is caused by atherosclerotic plaque rupture and not from a stenosis growing and blocking the blood flow. Although the stress caused by the blood flow does play a role in plaque rupture, it has been found that the degree of stenosis is a relatively minor factor in predicting which plaques are most prone to rupture. In fact, atherosclerotic plaques expand into the vessel wall during much of their existence and this can make their detection problematic
Initial-State Interactions in the Unpolarized Drell-Yan Process
We show that initial-state interactions contribute to the
distribution in unpolarized Drell-Yan lepton pair production and , without suppression. The asymmetry is expressed as a
product of chiral-odd distributions , where the quark-transversity function
is the transverse momentum dependent, light-cone
momentum distribution of transversely polarized quarks in an {\it unpolarized}
proton. We compute this (naive) -odd and chiral-odd distribution function
and the resulting asymmetry explicitly in a quark-scalar diquark
model for the proton with initial-state gluon interaction. In this model the
function equals the -odd (chiral-even) Sivers
effect function . This suggests that the
single-spin asymmetries in the SIDIS and the Drell-Yan process are closely
related to the asymmetry of the unpolarized Drell-Yan process,
since all can arise from the same underlying mechanism. This provides new
insight regarding the role of quark and gluon orbital angular momentum as well
as that of initial- and final-state gluon exchange interactions in hard QCD
processes.Comment: 22 pages, 6 figure
Left-right asymmetry for pion and kaon production in the semi-inclusive deep inelastic scattering process
We analyze the left-right asymmetry in the semi-inclusive deep inelastic
scattering (SIDIS) process without introducing any weighting functions. With
the current theoretical understanding, we find that the Sivers effect plays a
key role in our analysis. We use the latest parametrization of the Sivers and
fragmentation functions to reanalyze the production process and find
that the results are sensitive to the parametrization. We also extend our
calculation on the production, which can help us know more about the
Sivers distribution of the sea quarks and the unfavored fragmentation
processes. HERMES kinematics with a proton target, COMPASS kinematics with a
proton, deuteron, and neutron target (the information on the neutron target can
be effectively extracted from the He target), and JLab kinematics (both 6
GeV and 12 GeV) with a proton and neutron target are considered in our paper.Comment: 7 latex pages, 11 figures, final version for publication, with
references update
Restoration of factorization for low hadron hadroproduction
We discuss the applicability of the factorization theorem to low-
hadron production in hadron-hadron collision in a simple toy model, which
involves only scalar particles and gluons. It has been shown that the
factorization for high- hadron hadroproduction is broken by soft gluons in
the Glauber region, which are exchanged among a transverse-momentum-dependent
(TMD) parton density and other subprocesses of the collision. We explain that
the contour of a loop momentum can be deformed away from the Glauber region at
low , so the above residual infrared divergence is factorized by means of
the standard eikonal approximation. The factorization is then restored in
the sense that a TMD parton density maintains its universality. Because the
resultant Glauber factor is independent of hadron flavors, experimental
constraints on its behavior are possible. The factorization can also be
restored for the transverse single-spin asymmetry in hadron-hadron collision at
low in a similar way, with the residual infrared divergence being
factorized into the same Glauber factor.Comment: 12 pages, 2 figures, version to appear in EPJ
Space-time dependent couplings in N=1 SUSY gauge theories: Anomalies and Central Functions
We consider N=1 supersymmetric gauge theories in which the couplings are
allowed to be space-time dependent functions. Both the gauge and the
superpotential couplings become chiral superfields. As has recently been shown,
a new topological anomaly appears in models with space-time dependent gauge
coupling. Here we show how this anomaly may be used to derive the NSVZ beta
function in a particular, well-determined renormalisation scheme, both without
and with chiral matter. Moreover we extend the topological anomaly analysis to
theories coupled to a classical curved superspace background, and use it to
derive an all-order expression for the central charge c, the coefficient of the
Weyl tensor squared contribution to the conformal anomaly. We also comment on
the implications of our results for the central charge a expected to be of
relevance for a four-dimensional C-theorem.Comment: 28 pages, LaTeX, no figure
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