Aad G.Abbott B.Abeling K.Abicht N. J.Abidi S. H.Aboulhorma A.Abramowicz H.Abreu H.Abulaiti Y.Acharya B. S.Bourdarios C. AdamAdamczyk L.Addepalli S. V.Addison M. J.Adelman J.Adiguzel A.Adye T.Affolder A. A.Afik Y.Agaras M. N.Agarwala J.Aggarwal A.Agheorghiesei C.Ahmad A.Ahmadov F.Ahmed W. S.Ahuja S.Ai X.Aielli G.Aikot A.Tamlihat M. AitAitbenchikh B.Aizenberg I.Akbiyik M.Akesson T. P. A.Akimov A. V.Akiyama D.Akolkar N. N.Al Khoury K.Alberghi G. L.2025-05-192025-05-192023/09/281029-8479http://dx.doi.org/10.1007/JHEP09(2023)199https://publicacionesabiertas.userena.cl/handle/123456789/229This paper reports the first ATLAS measurement of the B-s(0) -> mu mu effective lifetime. The measurement is based on the data collected in 2015-2016, amounting to 26.3 fb(-1) of 13TeV LHC proton-proton collisions. The proper decay-time distribution of 58 +/- 13 background-subtracted signal candidates is fit with simulated signal templates parameterised as a function of the B-s(0) effective lifetime, with statistical uncertainties extracted through a Neyman construction. The resulting effective measurement of the B-s(0) -> mu mu lifetime is 0.99(-0.07)(+0.42) (stat.) +/- 0.17 (syst.) ps and it is found to be consistent with the Standard Model.Article