56 research outputs found
NLO Analysis of Small- Region in Drell-Yan Production with Parton Branching
The Parton-Branching Method (PB) facilitates the determination of Transverse
Momentum Dependent (TMD) parton densities across a wide \kt\ range, spanning
small to large transverse momentum scales. In the small region, both
intrinsic parton motion and resummed ultra-soft gluons are significant
contributors. Our analysis highlights their crucial role in shaping integrated
and TMD parton densities.
Using PB-derived TMD parton densities and a NLO calculation in MC@NLO style,
we compute the transverse momentum spectrum of Drell-Yan pairs across a broad
mass range. The spectrum's sensitivity to the intrinsic distribution
allows us to fine-tune parametric parameters. Starting from the
PB-NLO-HERAI+II-2018 set2 TMD parton distributions, we determine the intrinsic
distribution width, resulting in a slightly wider profile than the
default set. Importantly, this width remains independent of Drell-Yan pair mass
and center-of-mass energy (), distinguishing our approach.Comment: Presented at "The European Physical Society Conference on High Energy
Physics (EPS-HEP2023)", 21-25 August 2023, Hamburg, Germany, Submitted to PoS
- Proceedings of Science. Updated paper to include a reference published in
EPJ
The CCFM uPDF evolution uPDFevolv
uPDFevolv is an evolution code for TMD parton densities using the CCFM
evolution equation. A description of the underlying theoretical model and
technical realization is given together with a detailed program description,
with emphasis on parameters the user may want to changeComment: Code and description on https://updfevolv.hepforge.org Version to be
published in EPJ
TMD parton densities and corresponding parton showers: the advantage of four- and five-flavour schemes
The calculations of tagged jet production performed in the
four- and five-flavour schemes allow for detailed comparison of the heavy
flavour structure of collinear and transverse momentum dependent (TMD) parton
distributions as well as for detailed investigations of heavy quarks radiated
during the initial state parton shower cascade.
We have determined the first set of collinear and TMD parton distributions in
the four-flavour scheme with NLO DGLAP splitting functions within the
Parton-Branching (PB) approach. The four- and five-flavour PB-TMD distributions
were used to calculate tagged jet production at LHC energies
and very good agreement with measurements obtained at TeV
by the CMS and ATLAS collaborations is observed.
The different configurations of the hard process in the four- and
five-flavour schemes allow for a detailed investigation of the performance of
heavy flavor collinear and TMD parton distributions and the corresponding
initial TMD parton shower, giving confidence in the evolution of the PB-TMD
parton densities as well as in the PB-TMD parton shower
Determination of collinear and TMD photon densities using the Parton Branching method
We present the first determination of transverse momentum dependent (TMD)
photon densities with the Parton Branching method. The photon distribution is
generated perturbatively without intrinsic photon component. The input
parameters for quarks and gluons are determined from fits to precision
measurements of deep inelastic scattering cross sections at HERA. The TMD
densities are used to predict the mass and transverse momentum spectra of very
high mass lepton pairs from both Drell-Yan production and Photon-Initiated
lepton processes at the LHC.Comment: 5 pages, 4 figure
Polarized Deeply Inelastic Scattering (DIS) Structure Functions for Nucleons and Nuclei
We extract parton distribution functions (PDFs) and structure functions from
recent experimental data of polarized lepton-DIS on nucleons at next-to-leading
order (NLO) Quantum Chromodynamics. We apply the Jacobi polynomial method to
the DGLAP evolution as this is numerically efficient. Having determined the
polarized proton and neutron spin structure, we extend this analysis to
describe 3He and 3H polarized structure functions, as well as various sum
rules. We compare our results with other analyses from the literature.Comment: LaTeX, 12 pages, 11 figures, 6 tables. Update to match published
versio
On the role of soft gluons in collinear parton densities
The role of soft (non-perturbative) gluons in collinear parton densities is
investigated with the Parton Branching method as a solution of the DGLAP
evolution equations. It is found that soft gluons contribute significantly to
collinear parton densities.
Within the Parton Branching frame, the Sudakov form factor can be split into
a perturbative and non-perturbative part. The non-perturbative part can be
calculated analytically under certain conditions. It is shown that the
inclusion of soft (non-perturbative) gluons to the parton density evolution is
essential for the proper cancellation of divergent terms.
It is argued that the non-perturbative part of the Sudakov form factor has
its correspondence in Transverse Momentum Dependent parton distributions.
Within the Parton Branching approach, this non-perturbative Sudakov form factor
is constrained by fits of inclusive, collinear parton densities.
We show that the non-perturbative Sudakov form factor and soft gluon
emissions are essential for inclusive distributions (collinear parton densities
and Drell-Yan transverse momentum spectra), while those soft gluons play
essentially no role in final state hadron spectra.Comment: Significantly updated including studies on parton shower and
hadronizatio
Nucleon spin structure functions at NNLO in the presence of target mass corrections and higher twist effects
We extract polarized parton distribution functions (PPDFs), referred to as “KTA17,” together with the
highly correlated strong coupling αs from recent and up-to-date g1 and g2 polarized structure functions
world data at next-to-next-to-leading order in perturbative QCD. The stability and reliability of the results
are ensured by including nonperturbative target mass corrections as well as higher-twist terms which are
particularly important at the large-x region at low Q2. Their role in extracting the PPDFs in the nucleon is
studied. Sum rules are discussed and compared with other results from the literature. This analysis is made
by means of the Jacobi polynomials expansion technique to the DGLAP evolution. The uncertainties on the
observables and on the PPDFs throughout this paper are computed using standard Hessian error
propagation which served to provide a more realistic estimate of the PPDFs uncertainties
Study of spin-dependent structure functions of 3He and 3H at NNLO approximation and corresponding nuclear corrections
We determine polarized parton distribution functions (PPDFs) and structure functions from recent experimental data of polarized deep inelastic scattering (DIS) on nucleons at next-to-next-to-leading order (NNLO) approximation in perturbative quantum chromodynamics (pQCD). The nucleon polarized structure functions are computed using the Jacobi polynomial approach while target mass corrections (TMCs) are included in our fitting procedure. Having extracted the polarized spin structure functions, we extend our study to describe 3He
and 3H polarized structure functions, as well as the Bjorken sum rule. We also explore the importance of the nuclear corrections on the polarized nuclear structure functions at small and large values of x . Our results are compared with the recent available and high precision polarized 3He and 3H experimental data
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