830 research outputs found

### Measurement of dsigma/dy for high mass Drell-Yan e+e- Pairs at CDF

We report on the first measurement of the rapidity distribution dsigma/dy
over nearly the entire kinematic region of rapidity for e+e- pairs in the
Z-boson region of 66116 GeV/c2. The
data sample consists of 108 pb-1 of pbar-p collisions at sqrt{s}=1.8 TeV taken
by the Collider Detector at Fermilab during 1992--1995. The total cross section
in the Z-boson region is measured to be 252 +- 11 pb. The measured total cross
section and dsigma/dy are compared with quantum chromodynamics calculations in
leading and higher orders.Comment: 3 pages, Presented by Arie Bodek for the CDF Collaboration at
DPF-2000, Columbus, Ohio, August 200

### Modeling Deep Inelastic Cross Sections in the Few GeV Region

We present preliminary results on simple modifications and corrections to
GRV94 leading order parton distribution functions such that they can be used to
model electron,muon and neutrino deep-inelastic scattering cross sections at
low energies.Comment: 6 pages, 6 figures. Presented by Arie Bodek at NuInt01, the First
International Workshop on Neutrino-Nucleus Interactions in the Few GeV
Region, Dec. 2001, KEK, Tsukuba, Japan. To be published in Nucl. Physics B.
Proceedings Supplement, Fall 200

### Analytic Estimates of the QCD Corrections to Neutrino-Nucleus Scattering

We study the QCD corrections to neutrino deep-inelastic scattering on a
nucleus, and analytically estimate their size. For an isoscalar target, we show
that the dominant QCD corrections to the ratio of the neutral- to
charged-current events are suppressed by sin^4 theta_W, where theta_W is the
weak mixing angle. We then discuss the implications for the NuTeV determination
of sin^2 theta_W.Comment: 16 pages, Late

### Evidence for SU(3) symmetry breaking from hyperon production

We examine the SU(3) symmetry breaking in hyperon semileptonic decays (HSD)
by considering two typical sets of quark contributions to the spin content of
the octet baryons: Set-1 with SU(3) flavor symmetry and Set-2 with SU(3) flavor
symmetry breaking in HSD. The quark distributions of the octet baryons are
calculated with a successful statistical model. Using an approximate relation
between the quark fragmentation functions and the quark distributions, we
predict polarizations of the octet baryons produced in $e^+e^-$ annihilation
and semi-inclusive deeply lepton-nucleon scattering in order to reveal the
SU(3) symmetry breaking effect on the spin structure of the octet baryons. We
find that the SU(3) symmetry breaking significantly affects the hyperon
polarization. The available experimental data on the $\Lambda$ polarization
seem to favor the theoretical predictions with SU(3) symmetry breaking. We
conclude that there is a possibility to get a collateral evidence for SU(3)
symmetry breaking from hyperon production. The theoretical errors for our
predictions are discussed.Comment: 3 tables, 14 figure

### On the value of $\alpha_s$ from the analysis of the SLAC/BCDMS deep inelastic scattering data

We performed NLO QCD analysis of the nonsinglet part of the combined
SLAC/BCDMS data on $F_2$ with the extraction of $\alpha_s$ and high twist
contribution. It was shown that the value of $\alpha_s$ obtained in the
analysis is sensitive to the statistical inference procedures dealing with
systematic errors on the data. The fit with the complete account of
point-to-point correlations of the data gave the value of
$\alpha_s(M_Z)=0.1180\pm0.0017 (68% C.L.)$, to be compared with the previously
reported value of $\alpha_s(M_Z)=0.113\pm0.003 (99% C.L.)$. This new value of
$\alpha_s$ is compatible with the LEP measurements and the world average. The
high twist contribution being strongly anti-correlated with the value of
$\alpha_s$ became lower than it was previously reported.Comment: 9 pages, LATEX, 2 figures (PS), report-no added, English improved,
misprints corrected, minor changes of the tex

### Leading and higher twists in the proton polarized structure function at large Bjorken x

A phenomenological parameterization of the proton polarized structure
function has been developed for x > 0.02 using deep inelastic data up to ~ 50
(GeV/c)**2 as well as available experimental results on both photo- and
electro-production of proton resonances. According to the new parameterization
the generalized Drell-Hearn-Gerasimov sum rule is predicted to have a
zero-crossing point at Q**2 = 0.16 +/- 0.04 (GeV/c)**2. Then, low-order
polarized Nachtmann moments have been estimated and their Q**2-behavior has
been investigated in terms of leading and higher twists for Q**2 > 1
(GeV/c)**2. The leading twist has been treated at NLO in the strong coupling
constant and the effects of higher orders of the perturbative series have been
estimated using soft-gluon resummation techniques. In case of the first moment
higher-twist effects are found to be quite small for Q**2 > 1 (GeV/c)**2, and
the singlet axial charge has been determined to be a0[10 (GeV/c)**2] = 0.16 +/-
0.09. In case of higher order moments, which are sensitive to the large-x
region, higher-twist effects are significantly reduced by the introduction of
soft gluon contributions, but they are still relevant at Q**2 ~ few (GeV/c)**2
at variance with the case of the unpolarized transverse structure function of
the proton. Our finding suggests that spin-dependent correlations among partons
may have more impact than spin-independent ones. As a byproduct, it is also
shown that the Bloom-Gilman local duality is strongly violated in the region of
polarized electroproduction of the Delta(1232) resonance.Comment: revised version to appear in Phys. Rev. D; extended discussion on the
generalized DHG sum rul

### Pre-M Phase-promoting Factor Associates with Annulate Lamellae in Xenopus Oocytes and Egg Extracts

We have used complementary biochemical and in vivo approaches to study the compartmentalization of M phase-promoting factor (MPF) in prophase Xenopus eggs and oocytes. We first examined the distribution of MPF (Cdc2/CyclinB2) and membranous organelles in high-speed extracts of Xenopus eggs made during mitotic prophase. These extracts were found to lack mitochondria, Golgi membranes, and most endoplasmic reticulum (ER) but to contain the bulk of the pre-MPF pool. This pre-MPF could be pelleted by further centrifugation along with components necessary to activate it. On activation, Cdc2/CyclinB2 moved into the soluble fraction. Electron microscopy and Western blot analysis showed that the pre-MPF pellet contained a specific ER subdomain comprising "annulate lamellae" (AL): stacked ER membranes highly enriched in nuclear pores. Colocalization of pre-MPF with AL was demonstrated by anti-CyclinB2 immunofluorescence in prophase oocytes, in which AL are positioned close to the vegetal surface. Green fluorescent protein-CyclinB2 expressed in oocytes also localized at AL. These data suggest that inactive MPF associates with nuclear envelope components just before activation. This association may explain why nuclei and centrosomes stimulate MPF activation and provide a mechanism for targeting of MPF to some of its key substrates

### Neutron structure function and inclusive DIS from H-3 and He-3 at large Bjorken-x

A detailed study of inclusive deep inelastic scattering (DIS) from mirror A =
3 nuclei at large values of the Bjorken variable x is presented. The main
purpose is to estimate the theoretical uncertainties on the extraction of the
neutron DIS structure function from such nuclear measurements. On one hand,
within models in which no modification of the bound nucleon structure functions
is taken into account, we have investigated the possible uncertainties arising
from: i) charge symmetry breaking terms in the nucleon-nucleon interaction, ii)
finite Q**2 effects neglected in the Bjorken limit, iii) the role of different
prescriptions for the nucleon Spectral Function normalization providing baryon
number conservation, and iv) the differences between the virtual nucleon and
light cone formalisms. Although these effects have been not yet considered in
existing analyses, our conclusion is that all these effects cancel at the level
of ~ 1% for x < 0.75 in overall agreement with previous findings. On the other
hand we have considered several models in which the modification of the bound
nucleon structure functions is accounted for to describe the EMC effect in DIS
scattering from nuclei. It turns out that within these models the cancellation
of nuclear effects is expected to occur only at a level of ~ 3%, leading to an
accuracy of ~ 12 % in the extraction of the neutron to proton structure
function ratio at x ~ 0.7 -0.8$. Another consequence of considering a broad
range of models of the EMC effect is that the previously suggested iteration
procedure does not improve the accuracy of the extraction of the neutron to
proton structure function ratio.Comment: revised version to appear in Phys. Rev. C; main modifications in
Section 4; no change in the conclusion

### Association Between Insulin Resistance and Development of Microalbuminuria in Type 2 Diabetes: A prospective cohort study

[[abstract]]OBJECTIVE An association between insulin resistance and microalbuminuria in type 2 diabetes has often been found in cross-sectional studies. We aimed to reassess this relationship in a prospective Taiwanese cohort of type 2 diabetic subjects. RESEARCH DESIGN AND METHODS We enrolled 738 normoalbuminuric type 2 diabetic subjects, aged 56.6 +/- 9.0 years, between 2003 and 2005 and followed them through the end of 2009. Average follow-up time was 5.2 +/- 0.8 years. We used urine albumin-to-creatinine ratio to define microalbuminuria and the homeostasis model assessment for insulin resistance (HOMA-IR) to assess insulin resistance. The incidence rate ratio and Cox proportional hazard model were used to evaluate the association between HOMA-IR and development of microalbuminuria. RESULTS We found incidences of microalbuminuria of 64.8, 83.5, 93.3, and 99.0 per 1,000 person-years for the lowest to highest quartiles of HOMA-IR. Compared with those in the lowest quartile of HOMA-IR, the incidence rate ratio for those in the 2nd, 3rd, and highest quartiles were 1.28 (95% CI 0.88-1.87), 1.44 (0.99-2.08), and 1.52 (1.06-2.20), respectively (trend test: P < 0.001). By comparison with those in the lowest quartile, the adjusted hazard ratios were 1.37 (0.93-2.02), 1.66 (1.12-2.47), and 1.76 (1.20-2.59) for those in the 2nd, 3rd, and highest HOMA-IR quartiles, respectively. CONCLUSIONS According to the dose-response effects of HOMA-IR shown in this prospective study, we conclude that insulin resistance could significantly predict development of microalbuminuria in type 2 diabetic patients

- …