Choose timezone
Your profile timezone:
Powered by Indico
v3.3.4-pre
The Standard Model is the most powerful theory describing the fundamental constituents of matter and their interactions. Historically, relations between the fundamental parameters of the SM have been used to predict the mass of the top quark and to put constraints on the Higgs boson mass before these particles were experimentally confirmed. Today, the indirect determination of the W-boson mass from global electroweak fits outperforms the precision of its experimentally measured value. An improved experimental measurement is, therefore, one of the goals of the LHC physics program, aiming to test the overall consistency of the Standard Model and possibly reveal new, conflicting phenomena.
The seminar will discuss the improved measurement of the mass of the W boson at a centre-of-mass energy of 7 TeV, recently released by the ATLAS Collaboration. The previous ATLAS measurement is re-evaluated using a profile likelihood fit, which improves the precision of the mass determination by 15% by fully exploiting the information present in data.
Further improvements of the mass measurements are challenging and the modelling of the W-boson production and decay is one of the limiting factors to ultimately reach an uncertainty of 10 MeV at the LHC. New ATLAS measurements of the W and Z boson transverse momenta at a 5 and 13 TeV will also be presented. This remarkable analysis is performed using dedicated LHC runs with reduced instantaneous luminosity. Such an experimental environment is favourable for the reconstruction of the W-boson transverse momentum from the hadronic recoil. A high resolution of the hadronic recoil allows the low transverse momentum of the W boson to be measured with unprecedented granularity. The measurement provides a fundamental input for reducing the physics-modelling uncertainties in future W-boson mass determinations.
Refreshments will be served at 10:30
Michelangelo Mangano, Jan Fiete Grosse-Oetringhaus and Pedro Silva