JINST JINST Luminosity determination in $\sqrt{s}$ = 7 TeV proton collisions using the LHCf Front Counter at LHC Adriani O INFN, Florence Florence U. Bonechi L INFN, Florence Bongi M INFN, Florence Castellini G INFN, Florence Florence U. D'Alessandro R INFN, Florence Florence U. Fukatsu K Nagoya U., Solar-Terrestrial Environ. Lab. Haguenauer M Ecole Polytechnique Itow Y Nagoya U., Solar-Terrestrial Environ. Lab. Kasahara K Waseda U., RISE Mase T Nagoya U., Solar-Terrestrial Environ. Lab. Kawade K Nagoya U., Solar-Terrestrial Environ. Lab. Ricciarini S INFN, Florence Macina D CERN Masuda K Nagoya U., Solar-Terrestrial Environ. Lab. Menjo H KMI, Nagoya Mitsuka G Nagoya U., Solar-Terrestrial Environ. Lab. Muraki Y Nagoya U., Solar-Terrestrial Environ. Lab. Noda K INFN, Catania Papini P INFN, Florence Perrot A L CERN Sako T Nagoya U., Solar-Terrestrial Environ. Lab. KMI, Nagoya Shimizu Y Waseda U., RISE Suzuki K Nagoya U., Solar-Terrestrial Environ. Lab. Suzuki T Waseda U., RISE Tamura T Kanagawa U. Torii S Kanagawa U. Tricomi A INFN, Catania Catania U. Turner W C LBL, Berkeley Taki K Nagoya U., Solar-Terrestrial Environ. Lab. 2012 7 In the Large Hadron Collider forward (LHCf) experiment, the luminosity is determined with the counting rates of detectors called Front Counter. During the LHCf physics operation at √s = 7 TeV in 2010, two series of calibration run in the conversion factors from the counting rate to the luminosity were carried out on 26th of April and 9th of May. Using the luminosities determined in the April and May scans with 5 % and 4 % accuracy, the conversion factors were determined with 5.0 % accuracy, providing the luminosity determination at the LHCf experiment with this accuracy. research-article