In ongoing and upcoming hadron collider experiments, top quark physics will play an important role in testing the Standard Model and its possible extensions. In this work we present analytic results ...for the differential cross sections of top quark pair production in hadronic collisions at next-to-leading order in the QCD coupling, keeping the full dependence on the spins of the top quarks. These results are combined with the corresponding next-to-leading order results for the decay of polarized top quarks into dilepton, lepton plus jets, and all jets final states. As an application we predict double differential angular distributions which are due to the QCD-induced top quark spin correlations in the intermediate state. In addition to the analytic results, we give numerical results in terms of fit functions that can easily be used in an experimental analysis.
Top-quark physics plays an important role at hadron colliders such as the Tevatron at Fermilab or the upcoming Large Hadron Collider (LHC) at CERN. Given the planned experimental precision, detailed ...theoretical predictions are mandatory. In this article we present analytic results for the complete weak corrections to gluon-induced top-quark pair production – neglecting purely photonic corrections, completing our earlier results for the quark-induced reaction. As an application we discuss top-quark pair production at the Tevatron and LHC. In particular we show that, although they are small for inclusive quantities, weak corrections can be sizeable for differential distributions.
We analyze, within several parameter scenarios of type-II two-Higgs doublet extensions of the standard model, the impact of heavy neutral Higgs-boson resonances on top-quark pair production and their ...subsequent decay to dileptonic final states at the LHC (13 TeV). In particular, we investigate the effects of heavy Higgs bosons on top-spin observables, that is, the longitudinal top-quark polarization and top-quark spin correlations. We take into account NLO QCD as well as weak interaction corrections and show that top-spin observables, if evaluated in judiciously chosen top-quark pair invariant mass bins, can significantly enhance the sensitivity to heavy Higgs resonances in top-quark pair events.
We report on the calculation of the next-to-leading-order QCD corrections to the production of W-boson pairs in association with a hard jet at the Fermilab Tevatron and CERN Large Hadron Collider, ...which is an important source of background for Higgs boson and new-physics searches. The corrections stabilize the leading-order prediction for the cross section considerably, in particular, if a veto against the emission of a second hard jet is applied.
The next-to-leading order analysis for the cross section for hadroproduction of top-quark pairs close to threshold is presented. Within the framework of non-relativistic QCD a significant enhancement ...compared to fixed-order perturbation theory is observed which originates from the characteristic remnant of the 1
S
peak below production threshold of top-quark pairs. The analysis includes all color-singlet and color-octet configurations of top-quark pairs in
S
-wave states and, for the dominant configurations, it employs all-order soft-gluon resummation for the hard parton cross section. Numerical results for the Large Hadron Collider at
TeV and
TeV and also for the Tevatron are presented. The possibility of a top-quark mass measurement from the invariant-mass distribution of top-quark pairs is discussed.
Kira—A Feynman integral reduction program Maierhöfer, P.; Usovitsch, J.; Uwer, P.
Computer physics communications,
September 2018, 2018-09-00, Volume:
230
Journal Article
Peer reviewed
Open access
In this article, we present a new implementation of the Laporta algorithm to reduce scalar multi-loop integrals appearing in quantum field theoretic calculations to a set of master integrals. We ...extend existing approaches by using an additional algorithm based on modular arithmetic to remove linearly depen- dent equations from the system of equations arising from integration-by-parts and Lorentz identities. Furthermore, the algebraic manipulations required in the back substitution are optimized. We describe in detail the implementation as well as the usage of the program. In addition, we show benchmarks for concrete examples and compare the performance to Reduze 2 and FIRE 5. In our benchmarks we find that Kira is highly competitive with these existing tools.
Program title: Kira
Program Files doi:http://dx.doi.org/10.17632/v3cmsnfrnn.1
Licensing provisions: GPLv3
Programming language:C++
External routines/libraries used:Fermat 1, gateToFermat 2, GiNaC 3,4, yaml-cpp 5, zlib 6 and SQLite3 7
Nature of problem: The reduction of Feynman integrals to master integrals leads in general to a system of equations which contains redundant, i.e. linearly dependent, equations. In particular, for multi-scale problems, the algebraic manipulation of these redundant equations can lead to a substantial increase in runtime and memory consumption without affecting the results.
Solution method: The program identifies linearly dependent relations based on modular arithmetic with the help of an algorithm presented in Ref. 8. Afterwards the program brings a linearly independent system of equations in a triangular form. Furthermore, the algebraic manipulations required in the back substitution are optimized.
Restrictions: the CPU time and the available RAM
References:
1 R. H. Lewis, Computer Algebra System Fermat, https://home.bway.net/lewis/.
2 M. Tentioukov, gateToFermat, http://science.sander.su/FLink.htm.
3 C. W. Bauer, A. Frink, and R. Kreckel, Introduction to the GiNaC framework for symbolic computationwithin the C++ programming language, J. Symb. Comput. 33 (2000) 1, arXiv:cs/0004015 cs-sc.
4 J. Vollinga, GiNaC: Symbolic computation with C++, Nucl. Instrum. Meth. A559 (2006) 282-284, arXiv:hep-ph/0510057 hep-ph.
5 YAML, YAML Aint Markup Language, http://yaml.org.
6 J.-L. Gailly and M. Adler, ZLIB, http://zlib.net.
7 SQLite, SQLite3, version: 3.14.2, https://www.sqlite.org.
8 P. Kant, Finding Linear Dependencies in Integration-By-Parts Equations: A Monte Carlo Approach, Comput. Phys. Commun. 185 (2014) 1473-1476, arXiv:1309.7287 hep-ph.
Abstract We present the calculation of the next-to-leading order QCD corrections for top-quark pair production in association with an additional jet at hadron colliders, using the modified minimal ...subtraction scheme to renormalize the top-quark mass. The results are compared to measurements at the Large Hadron Collider run I. In particular, we determine the top-quark running mass from a fit of the theoretical results presented here to the LHC data.
Top-quark physics plays an important rôle at hadron colliders such as the Tevatron at Fermilab or the LHC at CERN. Given the planned precision at these colliders, precise theoretical predictions are ...required. In this paper we present the complete electroweak corrections to QCD-induced top-quark pair production in quark-antiquark annihilation. In particular we provide compact analytic expressions for the differential partonic cross section, which will be useful for further theoretical investigations.
We present the calculation of the next-to-leading order QCD corrections for top-quark pair production in association with an additional jet at hadron colliders, using the modified minimal subtraction ...scheme to renormalize the top-quark mass. The results are compared to measurements at the Large Hadron Collider run I. In particular, we determine the top-quark running mass from a fit of the theoretical results presented here to the LHC data.
We present an update of the Binoth Les Houches Accord (BLHA) to standardise the interface between Monte Carlo programs and codes providing one-loop matrix elements.
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