27 research outputs found
Low proton structure function, using gluon and pseudoscalar meson clouds in the constituent quark framework
The idea of the meson cloud approach in the chiral quark model has been
extended to include gluon cloud in order to achieve the parton densities in the
nucleon, based on the constitute quark framework. The splitting function of the
quark to the quark-meson and quark-gluon at low value are used to obtain
parton densities in the constituent quark. The phenomenological constituent
model is employed to extract the parton distributions in the proton at low
value. Since we have access to the parton densities at low , we are
able to obtain structure function at low value. The result
is in good agreement with available experimental data and some theoretical
models. To confirm the validity of our calculations, the fraction of total
momentum of proton which is carried by gluon at high and also the
Gottfried sum rule are computed. The results are in good agreement with what
are expected.Comment: 13 pages, 3 figure
Determination of neutron fracture functions from a global QCD analysis of the leading neutron production at HERA
In this article, we present our global QCD analysis of leading neutron production in deep inelastic scattering at H1 and ZEUS collaborations. The analysis is performed in the framework of a perturbative QCD description for semi-inclusive processes, which is based on the fracture functions approach. Modeling the nonperturbative part of the fragmentation process at the input scale Q20, we analyze the Q
2 dependence of the leading neutron structure functions and obtain the neutron fracture functions (neutron FFs) from next-to-leading order global QCD fit to data. We have also performed a careful estimation of the uncertainties using the âHessian methodâ for the neutron FFs and corresponding observables originating from experimental errors. The predictions based on the obtained neutron FFs are in good agreement with all data analyzed, at small and large longitudinal momentum fraction xL as well as the scaled fractional momentum variable
ÎČ
Phenomenology of leading nucleon production in ep collisions at HERA in the framework of fracture functions
In recent years, several experiments at the eâp collider HERA have collected high precision deepinelastic
scattering (DIS) data on the spectrum of leading nucleon carrying a large fraction of the protonâs energy. In this paper, we have analyzed recent experimental data on the production of forward protons and
neutrons in DIS at HERA in the framework of a perturbative QCD. We propose a technique based on the
fractures functions framework, and extract the nucleon fracture functions (FFs) MĂ°n=pĂ 2 Ă°x;Q2; xLĂ from
global QCD analysis of DIS data measured by the ZEUS Collaboration at HERA. We have shown that an
approach based on the fracture functions formalism allows us to phenomenologically parametrize the
nucleon FFs. Considering both leading neutron as well as leading proton production data at HERA, we
present the results for the separate parton distributions for all parton species, including valence quark
densities, the antiquark densities, the strange sea distribution, and the gluon distribution functions. We
proposed several parametrizations for the nucleon FFs and open the possibility of these asymmetries. The
obtained optimum set of nucleon FFs is accompanied by Hessian uncertainty sets which allow one to
propagate uncertainties to other observables interest. The extracted results for the t-integrated leading
neutron FLNĂ°3Ă 2 Ă°x;Q2; xLĂ and leading proton FLPĂ°3Ă 2 Ă°x;Q2; xLĂ structure functions are in good agreement with all data analyzed, for a wide range of fractional momentum variable x as well as the longitudinal
momentum fraction xL
A new approach to calculate the gluon polarization
We derive the Leading-Order master equation to extract the polarized gluon
distribution G(x;Q^2) = x \deltag(x;Q^2) from polarized proton structure
function, g1p(x;Q^2). By using a Laplace-transform technique, we solve the
master equation and derive the polarized gluon distribution inside the proton.
The test of accuracy which are based on our calculations with two different
methods confirms that we achieve to the correct solution for the polarized
gluon distribution. We show that accurate experimental knowledge of g1p(x;Q^2)
in a region of Bjorken x and Q^2, is all that is needed to determine the
polarized gluon distribution in that region. Therefore, to determine the gluon
polarization \deltag /g,we only need to have accurate experimental data on
un-polarized and polarized structure functions (F2p (x;Q^2) and g1p(x;Q^2)).Comment: 12 pages, 5 figure
Long-term exposure to air pollution and mortality in a Danish nationwide administrative cohort study: Beyond mortality from cardiopulmonary disease and lung cancer.
BACKGROUND: The association between long-term exposure to air pollution and mortality from cardiorespiratory diseases is well established, yet the evidence for other diseases remains limited. OBJECTIVES: To examine the associations of long-term exposure to air pollution with mortality from diabetes, dementia, psychiatric disorders, chronic kidney disease (CKD), asthma, acute lower respiratory infection (ALRI), as well as mortality from all-natural and cardiorespiratory causes in the Danish nationwide administrative cohort. METHODS: We followed all residents aged â„ 30 years (3,083,227) in Denmark from 1 January 2000 until 31 December 2017. Annual mean concentrations of fine particulate matter (PM2.5), nitrogen dioxide (NO2), black carbon (BC), and ozone (warm season) were estimated using European-wide hybrid land-use regression models (100 m Ă 100 m) and assigned to baseline residential addresses. We used Cox proportional hazard models to evaluate the association between air pollution and mortality, accounting for demographic and socioeconomic factors. We additionally applied indirect adjustment for smoking and body mass index (BMI). RESULTS: During 47,023,454 person-years of follow-up, 803,881 people died from natural causes. Long-term exposure to PM2.5 (mean: 12.4 ”g/m3), NO2 (20.3 ”g/m3), and/or BC (1.0 Ă 10-5/m) was statistically significantly associated with all studied mortality outcomes except CKD. A 5 ”g/m3 increase in PM2.5 was associated with higher mortality from all-natural causes (hazard ratio 1.11; 95% confidence interval 1.09-1.13), cardiovascular disease (1.09; 1.07-1.12), respiratory disease (1.11; 1.07-1.15), lung cancer (1.19; 1.15-1.24), diabetes (1.10; 1.04-1.16), dementia (1.05; 1.00-1.10), psychiatric disorders (1.38; 1.27-1.50), asthma (1.13; 0.94-1.36), and ALRI (1.14; 1.09-1.20). Associations with long-term exposure to ozone (mean: 80.2 ”g/m3) were generally negative but became significantly positive for several endpoints in two-pollutant models. Generally, associations were attenuated but remained significant after indirect adjustment for smoking and BMI. CONCLUSION: Long-term exposure to PM2.5, NO2, and/or BC in Denmark were associated with mortality beyond cardiorespiratory diseases, including diabetes, dementia, psychiatric disorders, asthma, and ALRI