António Onofre

Using single top rapidity to measure V-td, V-ts, V-tb at hadron colliders

Single top production processes are usually regarded as the ones in which V{sub tb} can be directly measured at hadron colliders. We show that the analysis of the single top rapidity distribution in t-channel and tW production can also set direct limits on V{sub td}. At LHC with 10 fb{sup -1} at 14 TeV, the combined limits on V{sub td} may be reduced by almost a factor of 2 when the top rapidity distribution is used. This also implies that the limits on V{sub tb} can also be reduced by 15%, since both parameters, as well as V{sub ts}, must be simultaneously obtained from a global fit to data. At Tevatron, the exploitation of this distribution would require very high statistics.

Top effective operators at the ILC

In this paper we study the effect of new physics contributions to the top quark pair production (t) in a possible future linear collider, such as the International Linear Collider (ILC). The use of a dimension-six gauge invariant effective operator approach allows to compare the prospected results at the ILC with the current ones obtained at the Large Hadron Collider (LHC), both in neutral and charged current processes. We also prove that the use of specific observables, together with a combination of measurements in different polarized beam scenarios and with different center-of-mass energies, allows to disentangle different effective operator contributions and significantly improve the limits on the anomalous couplings with respect to the LHC.

Pseudoscalar couplings in t t H production at NLO+NLL accuracy

We thank R. Frederix, Ossola, and N. Castro for useful discussions and for reading the manuscript. The in-house Monte Carlo code, which we developed and employed to evaluate the (differential) cross sections presented in this paper, was run on the computer cluster of the Center for Theoretical Physics at the Physics Department of New York City College of Technology. This work was supported by the CUNY Summer Collaborative Research Opportunity Grant No. 80232-20 17 and PSC-CUNY Grants No. 60061-00 48 and No. 0185-00 48. The work of A. F. is supported in part by the National Science Foundation under Grant No. PHY-1417354.

HEP-Frame: A Software Engineered Framework to Aid the Development and Efficient Multicore Execution of Scientific Code

This communication presents an evolutionary software prototype of a user-centered Highly Efficient Pipelined Framework, HEP-Frame, to aid the development of sustainable parallel scientific code with a flexible pipeline structure. HEP-Frame is the result of a tight collaboration between computational scientists and software engineers: it aims to improve scientists coding productivity, ensuring an efficient parallel execution on a wide set of multicore systems, with both HPC and HTC techniques. Current prototype complies with the requirements of an actual scientific code, includes desirable sustainability features and supports at compile time additional plugin interfaces for other scientific fields. The porting and development productivity was assessed and preliminary efficiency results are promising.

Removing Inefficiencies from Scientific Code: The Study of the Higgs Boson Couplings to Top Quarks

This paper presents a set of methods and techniques to remove inefficiencies in a data analysis application used in searches by the ATLAS Experiment at the Large Hadron Collider. Profiling scientific code helped to pinpoint design and runtime inefficiencies, the former due to coding and data structure design. The data analysis code used by groups doing searches in the ATLAS Experiment contributed to clearly identify some of these inefficiencies and to give suggestions on how to prevent and overcome those common situations in scientific code to improve the efficient use of available computational resources in a parallel homogeneous platform.

Tuning pipelined scientific data analyses for efficient multicore execution

Scientific data analyses often apply a pipelined sequence of computational tasks to independent datasets. Each task in the pipeline captures and processes a dataset element, may be dependent on other tasks in the pipeline, may have a different computational complexity and may be filtered out from progressing in the pipeline. The goal of this work is to develop an efficient scheduler that automatically (i) manages a parallel data reading and an adequate data structure creation, (ii) adaptively defines the most efficient order of pipeline execution of the tasks, considering their inter-dependence and both the filtering out rate and the computational weight, and (iii) manages the parallel execution of the computational tasks in a multicore system, applied to the same or to different dataset elements. A real case study data analysis application from High Energy Physics (HEP) was used to validate the efficiency of this scheduler. Preliminary results show an impressive performance improvement of the pipeline tuning when compared to the original sequential HEP code (up to a 35x speedup in a dual 12-core system), and also show significant performance speedups over conventional parallelization approaches of this case study application (up to 10x faster in the same system).

MEtop – a top FCNC event generator

In this work we present a new Monte Carlo generator for Direct top and Single top production via flavour-changing neutral currents (FCNC). This new tool calculates the cross section and generates events with Next-to-Leading order precision for the Direct top process and Leading-Order precision for all other FCNC single top processes. A set of independent dimension six FCNC operators has been implemented – including four-fermion operators – where at least one top-quark is present in the interaction.

Top Quark Couplings and Search for New Physics at the LHC

The search for new physics in top quark decays at the LHC is reviewed in this paper. Results from ATLAS [1] and CMS [2] experiments on top quark decays within the Standard Model are presented together with the measurements of the W boson polarizations and the study of the structure of the Wtb vertex. As a natural step forward, the experimental status on measurements sensitive to top quark couplings to gauge bosons (γ, Z, W and H) is reviewed as well as possible top quark decays Beyond the Standard Model (MSSM and FCNC).