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Top Quark Physics at the LHC [article]

Jorgen D'hondt
2007 arXiv   pre-print
The Large Hadron Collider (LHC) is expected to provide proton-proton collisions at a centre-of-mass energy of 14 TeV, yielding millions of of top quark events. The top-physics potential of the two general purpose experiments, ATLAS and CMS, is discussed according to state-of-the-art simulation of both physics and detectors. An overview is given of the most important results with emphasis on the expected improvements in our understanding of physics connected to the top quark.
arXiv:0707.1247v2 fatcat:oa5fby5ygvazbimh6g33e2cufu

Possible reduction of the total uncertainty on the W boson mass measured at LEP2 [article]

Jorgen D'Hondt
2002 arXiv   pre-print
An alternative W mass estimator in e+e- -> WW -> qqqq events at LEP2 is designed to optimize the balance between the statistical uncertainty and the systematic uncertainty due to a possible Colour Reconnection effect. The preliminary result for the total uncertainty on the W mass in this channel is roughly 30 % lower then those obtained with the standard estimators, based on the SKI implementation of Colour Reconnection. Also an indirect measurement of the SKI Colour Reconnection model
more » ... kappa is inferred from the difference between both W mass estimators.
arXiv:hep-ex/0205036v1 fatcat:d3n66kle3rf5xigy3jtqa5cugi

Colour reconnection at LEP2

Jorgen D'Hondt
2004 European Physical Journal C: Particles and Fields  
Two measurements are presented of estimators sensitive to the Colour Reconnection effect in WW events at LEP2. The results are compared with various phenomenological Monte Carlo implementations of the effect. A feasibility study is performed to reduce the total uncertainty in the direct W boson mass measurement at LEP2 by use of the inferred information about the Colour Reconnection effect.
doi:10.1140/epjcd/s2004-03-1621-3 fatcat:3hz7qbt4hjhkdhriysvfji3bqq

Learning to pinpoint effective operators at the LHC: a study of the tt̅bb̅ signature [article]

Jorgen D'Hondt, Alberto Mariotti, Ken Mimasu, Seth Moortgat, Cen Zhang
2018 arXiv   pre-print
In the context of the Standard Model effective field theory (SMEFT), we study the LHC sensitivity to four fermion operators involving heavy quarks by employing cross section measurements in the tt̅bb̅ final state. Starting from the measurement of total rates, we progressively exploit kinematical information and machine learning techniques to optimize the projected sensitivity at the end of Run III. Indeed, in final states with high multiplicity containing inter-correlated kinematical
more » ... , multi-variate methods provide a robust way of isolating the regions of phase space where the SMEFT contribution is enhanced. We also show that training for multiple output classes allows for the discrimination between operators mediating the production of tops in different helicity states. Our projected sensitivities not only constrain a host of new directions in the SMEFT parameter space but also improve on existing limits demonstrating that, on one hand, tt̅bb̅ production is an indispensable component in a future global fit for top quark interactions in the SMEFT, and on the other, multi-class machine learning algorithms can be a valuable tool for interpreting LHC data in this framework.
arXiv:1810.01603v1 fatcat:zvtivcwlojaifgwhkfvoilrrxm

Signatures of top flavour-changing dark matter

Jorgen D'Hondt, Alberto Mariotti, Kentarou Mawatari, Seth Moortgat, Pantelis Tziveloglou, Gerrit Van Onsem
2016 Journal of High Energy Physics  
We develop the phenomenology of scenarios in which a dark matter candidate interacts with a top quark through flavour-changing couplings, employing a simplified dark matter model with an s-channel vector-like mediator. We study in detail the top-charm flavour-changing interaction, by investigating the single top plus large missing energy signature at the LHC as well as constraints from the relic density and direct and indirect dark matter detection experiments. We present strategies to
more » ... sh between the top-charm and top-up flavour-changing models by taking advantage of the lepton charge asymmetry as well as by using charm-tagging techniques on an extra jet. We also show the complementarity between the LHC and canonical dark matter experiments in exploring the viable parameter space of the models.
doi:10.1007/jhep03(2016)060 fatcat:t3eo6ronfjcv5msjqa3d25szfm

Automated mass spectrum generation for new physics

Adam Alloul, Jorgen D'Hondt, Karen De Causmaecker, Benjamin Fuks, Michel Rausch de Traubenberg
2013 European Physical Journal C: Particles and Fields  
We describe an extension of the FeynRules package dedicated to the automatic generation of the mass spectrum associated with any Lagrangian-based quantum field theory. After introducing a simplified way to implement particle mixings, we present a new class of FeynRules functions allowing both for the analytical computation of all the model mass matrices and for the generation of a C++ package, dubbed ASperGe. This program can then be further employed for a numerical evaluation of the rotation
more » ... trices necessary to diagonalize the field basis. We illustrate these features in the context of the Two-Higgs-Doublet Model, the Minimal Left-Right Symmetric Standard Model and the Minimal Supersymmetric Standard Model.
doi:10.1140/epjc/s10052-013-2325-x fatcat:xuvoznllvfghxkcm3dtw7yqgni

Multilepton signals of gauge mediated supersymmetry breaking at the LHC

Jorgen D'Hondt, Karen De Causmaecker, Benjamin Fuks, Alberto Mariotti, Kentarou Mawatari, Christoffer Petersson, Diego Redigolo
2014 Physics Letters B  
We investigate multilepton LHC signals arising from electroweak processes involving sleptons. We consider the framework of general gauge mediated supersymmetry breaking, focusing on models where the low mass region of the superpartner spectrum consists of the three generations of charged sleptons and the nearly massless gravitino. We demonstrate how such models can provide an explanation for the anomalous four lepton events recently observed by the CMS collaboration, while satisfying other
more » ... ing experimental constraints. The best fit to the CMS data is obtained for a selectron/smuon mass of around 145 GeV and a stau mass of around 90 GeV. These models also give rise to final states with more than four leptons, offering alternative channels in which they can be probed and we estimate the corresponding production rates at the LHC.
doi:10.1016/j.physletb.2014.02.016 fatcat:3q23v4pq7jgb7jer5vh5pxb7ga

Learning to pinpoint effective operators at the LHC: a study of the tt¯bb¯$$ \mathrm{t}\overline{\mathrm{t}}\mathrm{b}\overline{\mathrm{b}} $$ signature

Jorgen D'Hondt, Alberto Mariotti, Ken Mimasu, Seth Moortgat, Cen Zhang
2018 Journal of High Energy Physics  
In the context of the Standard Model effective field theory (SMEFT), we study the LHC sensitivity to four fermion operators involving heavy quarks by employing cross section measurements in the tt̅bb̅ final state. Starting from the measurement of total rates, we progressively exploit kinematical information and machine learning techniques to optimize the projected sensitivity at the end of Run III. Indeed, in final states with high multiplicity containing inter-correlated kinematical
more » ... , multi-variate methods provide a robust way of isolating the regions of phase space where the SMEFT contribution is enhanced. We also show that training for multiple output classes allows for the discrimination between operators mediating the production of tops in different helicity states. Our projected sensitivities not only constrain a host of new directions in the SMEFT parameter space but also improve on existing limits demonstrating that, on one hand, tt̅bb̅ production is an indispensable component in a future global fit for top quark interactions in the SMEFT, and on the other, multi-class machine learning algorithms can be a valuable tool for interpreting LHC data in this framework.
doi:10.1007/jhep11(2018)131 fatcat:qccn6pm7m5gnpnm3jxo3otioi4

Potential of Standard Model measurements with CMS

Jorgen D'Hondt
2007 Proceedings of International Europhysics Conference on High Energy Physics — PoS(HEP2005)   unpublished
Although hadron colliders like the LHC are constructed for exploring new physics at higher energies, they also provide a tremendous set of data for precise measurements within the Standard Model. The LHC will provide proton-proton collisions at energies of about 14 TeV and at a rate of about 40 MHz. CMS is a general purpose detector which is designed to detect and measure the properties of the particles in the final state of these collisions. Detailed simulations of the expected events are
more » ... ed using Monte Carlo techniques. On the basis of these simulations and advanced data analysis techniques the potential for the precise Standard Model measurements can be studied. An overview is given of the results obtained within domains like top quark physics, electro-weak physics, gauge boson couplings, B-physics and QCD. Due to the high rate and energy it is expected that new Standard Model processes become visible at the LHC.
doi:10.22323/1.021.0295 fatcat:qjsxpb5uwbah5h2edbw6hrul2e

Particle physicists hash out long-term strategy for Europe

Toni Feder
2020 Physics today  
"The big elephant is power consumption," says Jorgen D'Hondt of Vrije University Brussels and a strategy coordinator.  ...  Several people quoted in this story are in the front row: Siegfried Bethke (second from left), Jorgen D'Hondt (fifth from left), and Leonid Rivkin (far right). 6 , 6 000+ Companies including 20+ Fortune  ... 
doi:10.1063/pt.3.4566 fatcat:5nmjy3jkhvb2xapa3hdg3crdby

Distributed Analysis in CMS

Alessandra Fanfani, Anzar Afaq, Jose Afonso Sanches, Julia Andreeva, Giusepppe Bagliesi, Lothar Bauerdick, Stefano Belforte, Patricia Bittencourt Sampaio, Ken Bloom, Barry Blumenfeld, Daniele Bonacorsi, Chris Brew (+67 others)
2010 Journal of Grid Computing  
The CMS experiment expects to manage several Pbytes of data each year during the LHC programme, distributing them over many A. Fanfani et al. location for physics analysis to support a wide community with thousands potential users. This represents an unprecedented experimental challenge in terms of the scale of distributed computing resources and number of user. An overview of the computing architecture, the software tools and the distributed infrastructure is reported. Summaries of the
more » ... ce in establishing efficient and scalable operations to get prepared for CMS distributed analysis are presented, followed by the user experience in their current analysis activities.
doi:10.1007/s10723-010-9152-1 fatcat:jvs2ccg7r5em7b3vringhmobye

Divisor Methods for Sequential Portfolio Allocation in Multi-Party Executive Bodies: Evidence from Northern Ireland and Denmark

Brendan O'Leary, Bernard Grofman, Jorgen Elklit
2005 American Journal of Political Science  
Divisor rule sequencing using the d'Hondt method was recently used to determine the ten cabinet positions in the Northern Ireland Executive Committee created under the 1998 Belfast ("Good Friday") Agreement  ...  Jørgen Elklit is Professor of Political Science, University of Aarhus, Bartholins Alle, DK, 8000 Aarhus C, Denmark; .  ...  Here the d'Hondt and Sainte-Laguë rules give us different allocations.  ... 
doi:10.1111/j.0092-5853.2005.00118.x fatcat:54vtgiwsojhjfddactcj5fogve

Er der virkelig ingen argumenter for at ændre det kommunale valgsystem?

Jørgen Elklit
2004 Politica - Tidsskrift for politisk videnskab  
Indenrigs-og sundhedsminister Lars Løkke Rasmussen udtalte i november 2003 i et svar i Folketinget, at der efter hans opfattelse ikke var argumenter for ved kommunalvalg m.m. at erstatte brugen af d'Hondts  ...  D'Hondts og Sainte-Lagues mandatfordelingssystemer er såkaldte divisor systemer.  ...  Den målsaetning opfyldes også langt bedre af største brøks og Sainte-Lagues metoder end af d'Hondts.  ... 
doi:10.7146/politica.v36i3.69908 fatcat:c45exgdzgrhwxisrlspudqlxjq

Learning to pinpoint effective operators at the LHC: a study of the $\text{t}\bar{\text{t}}\text{b}\bar{\text{b}}$ signature

Seth Moortgat, Jorgen D'Hondt, Alberto Mariotti, Ken Mimasu, Cen Zhang
2020 Proceedings of European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2019)   unpublished
In the context of the Standard Model effective field theory (SMEFT), we study the LHC sensitivity to four fermion operators involving heavy quarks by employing cross section measurements in the ttbb final state. Starting from the measurement of total rates, we progressively exploit kinematical information and machine learning techniques to optimize the projected sensitivity at the end of Run III. Indeed, in final states with high multiplicity containing inter-correlated kinematical information,
more » ... multi-variate methods provide a robust way of isolating the regions of phase space where the SMEFT contribution is enhanced. We also show that training for multiple output classes allows for the discrimination between operators mediating the production of tops in different helicity states. Our projected sensitivities not only constrain a host of new directions in the SMEFT parameter space but also improve on existing limits demonstrating that, on one hand, ttbb production is an indispensable component in a future global fit for top quark interactions in the SMEFT, and on the other, multi-class machine learning algorithms can be a valuable tool for interpreting LHC data in this framework.
doi:10.22323/1.364.0666 fatcat:rh34ufjkxncydcpg3x7l3x7yp4

Page 280 of Psychological Abstracts Vol. 67, Issue 1 [page]

1982 Psychological Abstracts  
Jorgen, 822 Engellenner, William J., 770 England.  ...  Paul L.. 1779 D'Hondt, Walter, 1099 AUTHOR INDEX Dickenson, A. H.. 610 Dickinson, Anthony. 490 Dickinson, Winifred B.. 1105 son, Gordon C.. 22% Dies. Robert R.. 1902 Dieskova.  ... 
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