Mainz 2014 – scientific programme

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T: Fachverband Teilchenphysik

T 42: Elektroschwache Wechselwirkung 2

T 42.9: Talk

Monday, March 24, 2014, 18:45–19:00, P110

Measurement of the production cross-section of a W boson in association with a charm quark in pp collisions at √s=8 TeV in ATLAS — •Christopher Betancourt¹, Kristin Lohwasser¹, Christian Weiser¹, Karl Jakobs¹, and Georges Aad² — ¹Albert-Ludwigs-Universitaet Freiburg — ²CPPM, Aix-Marseill Universite, CNRS/IN2P3

The production cross-section of a W boson in association with a single charm quark at hadron colliders is very sensitive to the strange quark parton distribution function (PDF). W+c production is dominated by strange-gluon scattering, for which the final state W boson is accompanied by a charm quark of opposite charge. The W is selected through its leptonic decay, while the charm quark is selected through its semi-leptonic decay into a soft muon. The signal is selected by requiring the charge of the W decay lepton and the charm quark to have opposite sign, while the backgrounds are mostly symmetrical between same sign and opposite sign.

We review the results of the recent 2011 cross section measurement using 4.6 pb⁻¹ of pp collisions at √s = 7 TeV with the ATLAS detector, which has been used to constrain the strange content of the proton, although the measurement is still dominated by statistical uncertainties. Preliminary results on the measurement of the production cross-section for the 2012 data at √s = 8 TeV using 20.3 fb⁻¹ of pp collisions are also presented, where the statistics are roughly 5 times higher than for the 7 TeV results. The estimation of the residual backgrounds using data-driven methods will be discussed in detail.