Transverse momentum distribution and nuclear modification factor of   forward neutral pion in proton--lead collisions at $\sqrt{s_{NN}} = 5.02$TeV
  The transverse momentum ($p_\text{T}$) distribution for inclusive neutral pions in the very forward rapidity region has been measured, with the Large Hadron Collider forward detector (LHCf), in proton--lead collisions at nucleon-nucleon center-of-mass energies of $\sqrt{s_{NN}} = 5.02$TeV at the LHC. The $p_\text{T}$ spectra obtained in the rapidity range $-11.0 < y_\text{lab} < -8.9$ and $0 < p_\text{T} < 0.6$GeV   (in the detector reference frame) show a strong suppression of the production of neutral pions after taking into account ultra-peripheral collisions. This leads to a nuclear modification factor value, relative to the interpolated $p_\text{T}$ spectra in proton-proton collisions at $\sqrt{s} = 5.02$TeV, of about 0.1--0.4. This value is compared with the predictions of several hadronic interaction Monte Carlo simulations. 
O. Adriani, E. Berti, L. Bonechi, M. Bongi, G. Castellini, R.   D'Alessandro, M. Del Prete, M. Haguenauer, Y. Itow, K. Kasah...
nucl-ex hep-ex