Measurement of the invisible width of the Z boson using the ATLAS detector

The invisible width of the Z boson is its partial width to neutrinos and is a well known Standard Model quantity. A direct measurement of the Z boson's invisible width has been performed using the ATLAS detector. The width was measured to be Γ(Z → inv) = 481 ± 5(stat.) ± 22(syst.), which rivals the precision of the direct measurements performed by the LEP experiments. Such a precise was measurement performed by measuring the ratio of Z → νν to Z → ee events and correcting for the differences between the neutrino and electron selections. The measurement is sensitive to any non Standard Model interactions with a jet(s) + undetected particle final state. No evidence was found for a deviation from the Standard Model, however improvements have been suggested to allow more sensitivity to new phenomena at high energies.