scholarly journals A massive variable flavour number scheme for the Drell-Yan process

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Rhorry Gauld

The prediction of differential cross-sections in hadron-hadron scattering processes is typically performed in a scheme where the heavy-flavour quarks (c, b, tc,b,t) are treated either as massless or massive partons. In this work, a method to describe the production of colour-singlet processes which combines these two approaches is presented. The core idea is that the contribution from power corrections involving the heavy-quark mass can be numerically isolated from the rest of the massive computation. These power corrections can then be combined with a massless computation (where they are absent), enabling the construction of differential cross-section predictions in a massive variable flavour number scheme. As an example, the procedure is applied to the low-mass Drell-Yan process within the LHCb fiducial region, where predictions for the rapidity and transverse-momentum distributions of the lepton pair are provided. To validate the procedure, it is shown how the n_fnf-dependent coefficient of a massless computation can be recovered from the massless limit of the massive one. This feature is also used to differentially extract the massless N^3LON3LO coefficient of the Drell-Yan process in the gluon-fusion channel.

Atoms ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 68 ◽  
Author(s):  
François Frémont

A four-body classical model based on the resolution of Hamilton equations of motion was used here to determine and analyze ionization doubly-differential cross sections following 3.6 MeV/amu Au53+ + He collisions. Our calculation was not able to reproduce the binary peaks experimentally observed in the transverse momentum distributions for electron emission energies larger than 10 eV. Surprisingly, by introducing a large number of free or quasi-free electrons that followed the projectile at the same velocity, the agreement between the experiment and our calculation was improved, since our model reproduced, at least qualitatively, the experimental binary peaks. The origin of the presence of such electrons is discussed.


Author(s):  
Simon Lumsden

This paper examines the theory of sustainable development presented by Jeffrey Sachs in The Age of Sustainable Development. While Sustainable Development ostensibly seeks to harmonise the conflict between ecological sustainability and human development, the paper argues this is impossible because of the conceptual frame it employs. Rather than allowing for a re-conceptualisation of the human–nature relation, Sustainable Development is simply the latest and possibly last attempt to advance the core idea of western modernity — the notion of self-determination. Drawing upon Hegel’s account of historical development it is argued that Sustainable Development and the notion of planetary boundaries cannot break out of a dualism of nature and self-determining agents.


1999 ◽  
Vol 32 (4) ◽  
pp. L73-L79 ◽  
Author(s):  
Kh Khayyat ◽  
T Weber ◽  
R Dörner ◽  
M Achler ◽  
V Mergel ◽  
...  

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Markus A. Ebert ◽  
Bernhard Mistlberger ◽  
Gherardo Vita

Abstract We demonstrate how to efficiently expand cross sections for color-singlet production at hadron colliders around the kinematic limit of all final state radiation being collinear to one of the incoming hadrons. This expansion is systematically improvable and applicable to a large class of physical observables. We demonstrate the viability of this technique by obtaining the first two terms in the collinear expansion of the rapidity distribution of the gluon fusion Higgs boson production cross section at next-to-next-to leading order (NNLO) in QCD perturbation theory. Furthermore, we illustrate how this technique is used to extract universal building blocks of scattering cross section like the N-jettiness and transverse momentum beam function at NNLO.


2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
M. V. Garzelli ◽  
L. Kemmler ◽  
S. Moch ◽  
O. Zenaiev

Abstract We present predictions for heavy-quark production at the Large Hadron Collider making use of the $$ \overline{\mathrm{MS}} $$ MS ¯ and MSR renormalization schemes for the heavy-quark mass as alternatives to the widely used on-shell renormalization scheme. We compute single and double differential distributions including QCD corrections at next-to-leading order and investigate the renormalization and factorization scale dependence as well as the perturbative convergence in these mass renormalization schemes. The implementation is based on publicly available programs, MCFM and xFitter, extending their capabilities. Our results are applied to extract the top-quark mass using measurements of the total and differential $$ t\overline{t} $$ t t ¯ production cross-sections and to investigate constraints on parton distribution functions, especially on the gluon distribution at low x values, from available LHC data on heavy-flavor hadro-production.


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