scholarly journals Parton showers and matching uncertainties in top quark pair production with Herwig 7

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Kyle Cormier ◽  
Simon Plätzer ◽  
Christian Reuschle ◽  
Peter Richardson ◽  
Stephen Webster
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Hadron Collider ◽  
Event Generator ◽  
Leading Order ◽  
Large Hadron Collider Data ◽  
Quark Decays ◽  
Depth Study ◽  
Matching Schemes ◽  
Hadronic Collisions

Abstract We evaluate the theoretical uncertainties in next-to-leading order plus parton shower predictions for top quark pair production and decay in hadronic collisions. Our work is carried out using the Herwig  7 event generator and presents an in-depth study of variations in matching schemes with two systematically different shower algorithms, the traditional angular-ordered and alternative dipole shower. We also present all of the required extensions of the Herwig dipole shower algorithm to properly take into account quark mass effects, as well as its ability to perform top quark decays. The predictions are compared at parton level as well as to Large Hadron Collider data, including in the boosted regime. We find that the regions where predictions with a non-top-quark-specific tune differ drastically from data are plagued by large uncertainties which are consistent between our two shower and matching algorithms.

scholarly journals Search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
◽  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Production Cross ◽  
Branching Fraction ◽  
Hadron Collider ◽  
Atlas Detector ◽  
Third Generation ◽  
Final State ◽  
Generation Scalar ◽  
Scalar Leptoquarks

Abstract A search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton is presented. The search is based on a dataset of pp collisions at $$ \sqrt{s} $$ s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. Events are selected if they have one light lepton (electron or muon) and at least one hadronically decaying τ -lepton, or at least two light leptons. In addition, two or more jets, at least one of which must be identified as containing b-hadrons, are required. Six final states, defined by the multiplicity and flavour of lepton candidates, are considered in the analysis. Each of them is split into multiple event categories to simultaneously search for the signal and constrain several leading backgrounds. The signal-rich event categories require at least one hadronically decaying τ-lepton candidate and exploit the presence of energetic final-state objects, which is characteristic of signal events. No significant excess above the Standard Model expectation is observed in any of the considered event categories, and 95% CL upper limits are set on the production cross section as a function of the leptoquark mass, for different assumptions about the branching fractions into tτ and bν. Scalar leptoquarks decaying exclusively into tτ are excluded up to masses of 1.43 TeV while, for a branching fraction of 50% into tτ, the lower mass limit is 1.22 TeV.

scholarly journals Next-to-leading order QCD predictions for top-quark pair production with up to two jets merged with a parton shower

2015 ◽  
Vol 748 ◽  
pp. 74-78 ◽  
Author(s):  
Stefan Höche ◽  
Frank Krauss ◽  
Philipp Maierhöfer ◽  
Stefano Pozzorini ◽  
Marek Schönherr ◽  
...  
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Parton Shower ◽  
Leading Order ◽  
Two Jets

scholarly journals Next-to-leading order QCD predictions for top-quark pair production with up to three jets

2017 ◽  
Vol 77 (3) ◽  
Author(s):  
S. Höche ◽  
P. Maierhöfer ◽  
N. Moretti ◽  
S. Pozzorini ◽  
F. Siegert
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Leading Order

scholarly journals Development and validation of HERWIG 7 tunes from CMS underlying-event measurements

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
Top Quark ◽  
W Boson ◽  
Parton Distribution Function ◽  
Event Generator ◽  
Event Shape ◽  
Minimum Bias ◽  
Leading Order ◽  
Underlying Event ◽  
Proton Proton ◽  
Positron Collisions

AbstractThis paper presents new sets of parameters (“tunes”) for the underlying-event model of the $${\textsc {herwig}} \,7$$ H E R W I G 7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in $${\textsc {herwig}} \,7$$ H E R W I G 7 , and are obtained from a fit to minimum-bias data collected by the CMS experiment at $$\sqrt{s}=0.9$$ s = 0.9 , 7, and $$13 \,\text {Te}\text {V} $$ 13 Te . The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the data.

scholarly journals T-Odd Anomalous Interactions of the Top-Quark at the Large Hadron Collider

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Apurba Tiwari ◽  
Sudhir Kumar Gupta
Keyword(s):  
Large Hadron Collider ◽  
Pair Production ◽  
Top Quark ◽  
Coupling Strength ◽  
Hadron Collider ◽  
Decay Products ◽  
Wide Range

We study the effects of T-odd interactions of top-quark via the pair production of the top-quark in the semileptonic detection modes at the Large Hadron Collider by means of the T-odd observables constructed through the momenta of the observed decay products of the top (and anti-top)-quark for a wide range of CP-violating scale Λ . Estimates on sensitivities of the coupling strength of such interactions for 13 TeV LHC energy with ∫ L d t = 36.1   f b − 1 , 140   f b − 1 and for HL-LHC with 14 TeV energy with integrated luminosities of 0.3   a b − 1 , 1   a b − 1 , 2   a b − 1 , and 3   a b − 1 are also presented for Λ ranging between M W and 2 TeV.

scholarly journals TOP QUARK PAIR PRODUCTION AND DECAY INCLUDING SPIN EFFECTS AT HADRON COLLIDERS: PREDICTIONS AT NLO QCD

2003 ◽  
Vol 18 (08) ◽  
pp. 1357-1364 ◽  
Author(s):  
W. BERNREUTHER ◽  
A. BRANDENBURG ◽  
Z. G. SI ◽  
P. UWER
Keyword(s):  
Angular Distribution ◽  
Pair Production ◽  
Top Quark ◽  
Leading Order ◽  
Hadron Colliders ◽  
Tevatron Collider ◽  
Spin Effects ◽  
Quark Flavor ◽  
Future Data ◽  
Hadronic Production

Top quark-antiquark [Formula: see text] pairs will be produced copiously at the Tevatron collider and in huge numbers at the LHC. This will make possible detailed investigations of the properties and interactions of this quark flavor. The analysis and interpretation of future data requires precise predictions of the hadronic production of [Formula: see text] pairs and of their subsequent decays. In this talk the reactions [Formula: see text], [Formula: see text] are considered and results are presented of our calculation6 of the dilepton angular distribution at next-to-leading order QCD, keeping the full dependence on the spins of the intermediate [Formula: see text] state. The angular distribution is determined for different choices of reference axes that can be identified with the t and [Formula: see text] spin axes. While the QCD corrections to the leading-order distribution turn out to be small in the case of the LHC, we find them to be sizeable in the case of the Tevatron and find, moreover, the angular distribution to be sensitive to the parton content of the proton.

scholarly journals Next-to-leading order corrections to top quark decays to heavy quarkonia

2010 ◽  
Vol 81 (11) ◽  
Author(s):  
Peng Sun ◽  
Li-Ping Sun ◽  
Cong-Feng Qiao
Keyword(s):  
Top Quark ◽  
Heavy Quarkonia ◽  
Leading Order ◽  
Quark Decays
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