4,273,625 research outputs found
Global Analysis of Data on the Proton Structure Function g1 and Extraction of its Moments
Inspired by recent measurements with the CLAS detector at Jefferson Lab, we
perform a self-consistent analysis of world data on the proton structure
function g1 in the range 0.17 < Q2 < 30 (GeV/c)**2. We compute for the first
time low-order moments of g1 and study their evolution from small to large
values of Q2. The analysis includes the latest data on both the unpolarized
inclusive cross sections and the ratio R = sigmaL / sigmaT from Jefferson Lab,
as well as a new model for the transverse asymmetry A2 in the resonance region.
The contributions of both leading and higher twists are extracted, taking into
account effects from radiative corrections beyond the next-to-leading order by
means of soft-gluon resummation techniques. The leading twist is determined
with remarkably good accuracy and is compared with the predictions obtained
using various polarized parton distribution sets available in the literature.
The contribution of higher twists to the g1 moments is found to be
significantly larger than in the case of the unpolarized structure function F2.Comment: 18 pages, 13 figures, to appear in Phys. Rev.
Towards a global analysis of polarized parton distributions
We present a technique for implementing in a fast way, and without any
approximations, higher-order calculations of partonic cross sections into
global analyses of parton distribution functions. The approach, which is set up
in Mellin-moment space, is particularly suited for analyses of future data from
polarized proton-proton collisions, but not limited to this case. The
usefulness and practicability of this method is demonstrated for the
semi-inclusive production of hadrons in deep-inelastic scattering and the
transverse momentum distribution of ``prompt'' photons in pp collisions, and a
case study for a future global analysis of polarized parton densities is
presented.Comment: 20 pages, LaTeX, 6 eps figures, final version to appear in PRD (minor
changes
Diluting the Scalability Boundaries: Exploring the Use of Disaggregated Architectures for High-Level Network Data Analysis
Traditional data centers are designed with a rigid architecture of
fit-for-purpose servers that provision resources beyond the average workload in
order to deal with occasional peaks of data. Heterogeneous data centers are
pushing towards more cost-efficient architectures with better resource
provisioning. In this paper we study the feasibility of using disaggregated
architectures for intensive data applications, in contrast to the monolithic
approach of server-oriented architectures. Particularly, we have tested a
proactive network analysis system in which the workload demands are highly
variable. In the context of the dReDBox disaggregated architecture, the results
show that the overhead caused by using remote memory resources is significant,
between 66\% and 80\%, but we have also observed that the memory usage is one
order of magnitude higher for the stress case with respect to average
workloads. Therefore, dimensioning memory for the worst case in conventional
systems will result in a notable waste of resources. Finally, we found that,
for the selected use case, parallelism is limited by memory. Therefore, using a
disaggregated architecture will allow for increased parallelism, which, at the
same time, will mitigate the overhead caused by remote memory.Comment: 8 pages, 6 figures, 2 tables, 32 references. Pre-print. The paper
will be presented during the IEEE International Conference on High
Performance Computing and Communications in Bangkok, Thailand. 18 - 20
December, 2017. To be published in the conference proceeding
Impact of unidentified light charged hadron data on the determination of pion fragmentation functions
In this paper a new comprehensive analysis of parton-to-pion fragmentation
functions (FFs) is performed for the first time by including all experimental
data sets on single inclusive pion as well as unidentified light charged hadron
production in electron-positron () annihilation. We determine the pion
FFs along with their uncertainties using the standard "Hessian" technique at
next-to-leading order (NLO) and next-to-next-to leading order (NNLO) in
perturabative QCD. It is shown that the determination of pion FFs using
simultaneously the data sets from pion and unidentified light charged hadron
productions leads to the reduction of all pion FFs uncertainties especially for
the case of strange quark and gluon FFs by significant factors. In this study,
we have quantified the constraints that these data sets could impose on the
extracted pion FFs. Our results also illustrate the significant improvement in
the precision of FFs fits achievable by inclusion of higher order corrections.
The improvements on both FFs uncertainties as well as fit quality have been
clearly discussed.Comment: 34 pages, 9 figures and 3 table
- âŠ