Phys. Rev. D Phys. Rev. D Measurements of longitudinal and transverse momentum distributions for neutral pions in the forward-rapidity region with the LHCf detector Adriani O. INFN, Florence Florence U. Berti E. INFN, Florence Florence U. Bonechi L. INFN, Florence Bongi M. INFN, Florence Florence U. D'Alessandro R. INFN, Florence Florence U. Del Prete M. INFN, Florence Florence U. Haguenauer M. Ec. Polytech., Palaiseau (main) Itow Y. Nagoya U., Solar-Terrestrial Environ. Lab. KMI, Nagoya Iwata T. Waseda U., RISE Kasahara K. Waseda U., RISE Kawade K. Nagoya U., Solar-Terrestrial Environ. Lab. Makino Y. Nagoya U., Solar-Terrestrial Environ. Lab. Masuda K. Nagoya U., Solar-Terrestrial Environ. Lab. Matsubayashi E. Nagoya U., Solar-Terrestrial Environ. Lab. Menjo H. Nagoya U. Mitsuka G. Florence U. Muraki Y. Nagoya U., Solar-Terrestrial Environ. Lab. Papini P. INFN, Florence Perrot A.L. CERN Ricciarini S. INFN, Florence IFAC, Florence Sako T. Nagoya U., Solar-Terrestrial Environ. Lab. KMI, Nagoya Sakurai N. KMI, Nagoya Suzuki T. Waseda U., RISE Tamura T. Kanagawa U. Tiberio A. INFN, Florence Florence U. Torii S. Waseda U., RISE Tricomi A. INFN, Catania Catania U. Turner W.C. LBL, Berkeley Ueno M. KMI, Nagoya Zhou Q.D. Nagoya U., Solar-Terrestrial Environ. Lab. 2016 94 The transverse and longitudinal momentum distributions for inclusive neutral pions in the very forward rapidity region have been measured with the Large Hadron Collider forward detector in proton-proton collisions at $\sqrt{s}=$ 2.76 and 7 TeV and in proton-lead collisions at nucleon-nucleon center-of-mass energies of $\sqrt{s_\text{NN}}=$ 5.02 TeV at the LHC. Such momentum distributions in proton-proton collisions are compatible with the hypotheses of limiting fragmentation and Feynman scaling. A sizable suppression of the production of neutral pions, after taking into account ultraperipheral collisions, is found in the transverse and longitudinal momentum distributions obtained in proton-lead collisions. This leads to a strong nuclear modification factor value of about 0.1-0.3. The experimental measurements presented in this paper provide a benchmark for the hadronic interaction Monte Carlo simulations codes that are used for the simulation of air showers. research-article