scholarly journals Dijet correlations at BNL RHIC: Leading-orderkt-factorization approach versus next-to-leading order collinear approach

2007 ◽  
Vol 76 (3) ◽  
Author(s):  
A. Szczurek ◽  
A. Rybarska ◽  
G. Ślipek
Keyword(s):  
Leading Order ◽  
Factorization Approach

scholarly journals Introduction to the Transverse-Momentum-Weighted Technique in the Twist-3 Collinear Factorization Approach

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Hongxi Xing ◽  
Shinsuke Yoshida
Keyword(s):  
Transverse Momentum ◽  
Leading Order ◽  
Precise Description ◽  
Collinear Factorization ◽  
Factorization Approach ◽  
Hard Part ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Successful Approach

The twist-3 collinear factorization framework has drawn much attention in recent decades as a successful approach in describing the data for single spin asymmetries (SSAs). Many SSAs data have been experimentally accumulated in a variety of energies since the first measurement was done in the late 1970s and it is expected that the future experiments like Electron-Ion-Collider will provide us with more data. In order to perform a consistent and precise description of the data taken in different kinematic regimes, the scale evolution of the collinear twist-3 functions and the perturbative higher-order hard part coefficients are mandatory. In this paper, we introduce the techniques for next-to-leading order (NLO) calculation of transverse-momentum-weighted SSAs, which can be served as a useful tool to derive the QCD evolution equation for twist-3 functions and to verify the QCD collinear factorization for twist-3 observables at NLO, as well as obtain the finite NLO hard part coefficients.

scholarly journals Intrinsic charm in the nucleon and charm production at large rapidities in collinear, hybrid and kT-factorization approaches

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Rafał Maciuła ◽  
Antoni Szczurek
Keyword(s):  
Transverse Momentum ◽  
High Energy ◽  
Charm Production ◽  
Leading Order ◽  
Collinear Factorization ◽  
Factorization Approach ◽  
High Energies ◽  
Neutrino Production ◽  
Intrinsic Charm ◽  
Gluon Distributions

Abstract We discuss the role of intrinsic charm (IC) in the nucleon for forward production of c-quark (or $$ \overline{c} $$ c ¯ -antiquark) in proton-proton collisions for low and high energies. The calculations are performed in collinear-factorization approach with on-shell partons, kT-factorization approach with off-shell partons as well as in a hybrid approach using collinear charm distributions and unintegrated (transverse momentum dependent) gluon distributions. For the collinear-factorization approach we use matrix elements for both massless and massive charm quarks/antiquarks. The distributions in rapidity and transverse momentum of charm quark/antiquark are shown for a few different models of IC. Forward charm production is dominated by gc-fusion processes. The IC contribution dominates over the standard pQCD (extrinsic) gg-fusion mechanism of $$ c\overline{c} $$ c c ¯ -pair production at large rapidities or Feynman-xF. We perform similar calculations within leading-order and next-to-leading order kT-factorization approach. The kT-factorization approach leads to much larger cross sections than the LO collinear approach. At high energies and large rapidities of c-quark or $$ \overline{c} $$ c ¯ -antiquark one tests gluon distributions at extremely small x. The IC contribution has important consequences for high-energy neutrino production in the Ice-Cube experiment and can be, to some extent, tested at the LHC by the SHIP and FASER experiments by studies of the ντ neutrino production.

scholarly journals Photon and leptons induced processes at the LHC

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Luca Buonocore ◽  
Paolo Nason ◽  
Francesco Tramontano ◽  
Giulia Zanderighi
Keyword(s):  
Cross Sections ◽  
Parton Shower ◽  
Search Strategy ◽  
Scalar Particle ◽  
Leading Order ◽  
Hadronic Tensor ◽  
Factorization Approach ◽  
Exotic Particles ◽  
Initial States ◽  
Standard Model Process

Abstract We study a few basic photon- and lepton-initiated processes at the LHC which can be computed using the recently developed photon and lepton parton densities. First, we consider the production of a massive scalar particle initiated by lepton-antilepton annihilation and photon-photon fusion as representative examples of searches of exotic particles. Then we study lepton-lepton scattering, since this Standard-Model process may be observable at the LHC. We examine these processes at leading and next-to-leading order and, using the POWHEG method, we match our calculations to parton shower programs that implement the required lepton or photon initial-states. We assess the typical size of cross-sections and their uncertainties and discuss the preferred choices for the factorization scale. These processes can also be computed starting directly from the lepto-production hadronic tensor, leading to a result where some collinear-enhanced QED corrections are missing, but all strong corrections are included. Thus, we are in the unique position to perform a comparison of results obtained via the factorization approach to a calculation that does not have strong corrections. This is particularly relevant in the case of lepton-scattering, that is more abundant at lower energies where it is affected by larger strong corrections. We thus compute this process also with the hadronic-tensor method, and compare the results with those obtained with POWHEG. Finally, for some lepton-lepton scattering processes, we compare the size of the signal to the main quark-induced background, which is double Drell-Yan production, and outline a preliminary search strategy to enhance the signal to background ratio.

scholarly journals PARTON SHOWERS BEYOND THE LEADING ORDER: A FACTORIZATION APPROACH

2001 ◽  
Vol 16 (supp01a) ◽  
pp. 238-241 ◽  
Author(s):  
F. HAUTMANN
Keyword(s):  
Recent Work ◽  
Parton Shower ◽  
Leading Order ◽  
Factorization Approach

We discuss recent work on methods for incorporating nonleading QCD corrections in parton shower algorithms.

scholarly journals Direct CP Violation from Isospin Symmetry Breaking Effects for the Decay Process B-s→P(V)π0 in PQCD

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Gang Lü ◽  
Qin-Qin Zhi
Keyword(s):  
Cp Violation ◽  
Symmetry Breaking ◽  
Quark Mass ◽  
Mass Difference ◽  
Electroweak Interaction ◽  
Decay Process ◽  
Isospin Symmetry ◽  
Leading Order ◽  
Factorization Approach ◽  
Isospin Symmetry Breaking

We investigate the direct CP violation for the decay process of B-s→P(V)π0 (P,V refer to the pseudoscalar meson and vector meson, resp.) via isospin symmetry breaking effects from the π0-η-η′ mixing mechanism in PQCD factorization approach. Isospin symmetry breaking arises from the electroweak interaction and the u-d quark mass difference by the strong interaction, which are known to be tiny. However, we find that isospin symmetry breaking at the leading order shifts the CP violation due to the new strong phases.

Sign in / Sign up

Export Citation Format

Share Document