Nuclear dependence of light neutral meson production in p-A collisions at 400 GeV with NA60

R. Arnaldi , K. Banicz , K. Borer , J. Castor (1) , B. Chaurand (2) , W. Chen , C. Cicalò , A. Colla , P. Cortese , S. Damjanovic , A. David , A. de Falco , A. Devaux (1) , L. Ducroux (3) , H. En'Yo , J. Fargeix (1) , A. Ferretti , M. Floris , A. Förster , P. Force (1) , N. Guettet (1) , A. Guichard (3) , H. Gulkanian , J.M. Heuser , P. Jarron , M. Keil , L. Kluberg (2) , Z. Li , C. Lourenço , J. Lozano , F. Manso (1) , P. Martins , A. Masoni , A. Neves , H. Ohnishi , C. Oppedisano , P. Parracho , Philippe Pillot (3) , T. Poghosyan , G. Puddu , E. Radermacher , P. Ramalhete , P. Rosinsky , E. Scomparin , J. Seixas , S. Serci , R. Shahoyan , P. Sonderegger , H.J. Specht , R. Tieulent (3) , A. Uras (3) , G. Usai , R. Veenhof , H.K. Wöhri

1 LPC - Laboratoire de Physique de Clermont
2 LLR - Laboratoire Leprince-Ringuet
3 IPNL - Institut de Physique Nucléaire de Lyon

The NA60 experiment has studied low-mass muon pair production in proton–nucleus collisions with a system of Be, Cu, In, W, Pb and U targets, using a 400 GeV proton beam at the CERN SPS. The transverse momentum spectra of the $\rho /\omega $ and $\phi $ mesons are measured in the full $p_{\mathrm {T}}$ range accessible, from $p_{\mathrm {T}}= 0$ up to $2 \, {\hbox {GeV/c}}$ . The nuclear dependence of the production cross sections of the $\eta $ , $\omega $ and $\phi $ mesons has been found to be consistent with the power law $\sigma _{\mathrm {pA}} \propto {\mathrm {A}}^\alpha $ , with the $\alpha $ parameter increasing as a function of $p_{\mathrm {T}}$ for all the particles, and an approximate hierarchy $\alpha _\eta \approx \alpha _\phi > \alpha _\omega $ . The cross section ratios $\sigma _\eta /\sigma _\omega $ , $\sigma _\rho /\sigma _\omega $ and $\sigma _\phi /\sigma _\omega $ have been studied as a function of the size A of the production target, and an increase of the $\eta $ and $\phi $ yields relative to the $\omega $ is observed from p–Be to p–U collisions.

Mots clés: meson: production; transverse momentum: momentum spectrum; muon: pair production; cross section: ratio; p: beam; NA60; dimuon: mass spectrum; p nucleus: scattering; CERN SPS; eta(958): decay; omega(783): decay; Phi(1020): decay

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

R. Arnaldi, K. Banicz, K. Borer, J. Castor, B. Chaurand, et al.. Nuclear dependence of light neutral meson production in p-A collisions at 400 GeV with NA60. European Physical Journal C: Particles and Fields, 2019, 79 (5), pp.443. ⟨10.1140/epjc/s10052-019-6848-7⟩. ⟨hal-02154290⟩