Eur. Phys. J. C (2008) 53: 689-699
https://doi.org/10.1140/epjc/s10052-007-0519-9

Special Article - Scientific Note

ATLAS sensitivity to Wtb anomalous couplings in top quark decays

¹ Departamento de Física Teórica y del Cosmos and CAFPE, Universidad de Granada, 18071, Granada, Spain
² LIP, Dep. Física, Universidade de Coimbra, 3004-516, Coimbra, Portugal

^* e-mail: nuno.castro@lipc.fis.uc.pt

Received: 22 June 2007
Revised: 14 December 2007
Published online: 10 January 2008

Abstract

We study the sensitivity of the ATLAS experiment to Wtb anomalous couplings in top pair production with semileptonic decay, pp→tt̄→W⁺bW^-b̄ with one of the W bosons decaying leptonically and the other hadronically. Several observables are examined, including the W helicity fractions and new quantities recently introduced, such as the ratios of helicity fractions and some angular asymmetries defined in the W rest frame. The dependence on anomalous couplings of all these observables has been previously obtained. In this work we show that some of the new observables also have smaller systematic uncertainties than the helicity fractions, with a similar or stronger dependence on anomalous couplings. Consequently, their measurement can significantly improve the limits on anomalous couplings. Moreover, the most sensitive measurements can be combined. In this case, the precision achieved in the determination of Wtb anomalous couplings can be of a few percent in the semileptonic channel alone.