g +A  J/Ψ+A : possible background sources

• “Non-physical”:

• (1) Cosmic rays: no ZDC, no good vtx.

• (2) Beam-gas: no good vtx., large multiplicity, asymmetric dN/dy

• Physical processes:

• (3) Peripheral nuclear A+A: “large” multiplicity, large pT

• (4) Hadronic diffractive (Pomeron-Pomeron, rapidity gap evt.):

• forward proton emission, larger pT: pT(gg) < pT(PP), like-sign pairs.

• Hard-diffractive J/ production.

• (5) Incoherent UPC g+nn+J/: pT(gg) < pT(gP), wider & asymm. dN/dy,

• ≥2 neutrons (induced nuclear break-up) w/ same direction as J/.

• (6) Other coherent UPC processes:

• gg  e+e- (Important !) , gA  jet(s)+A (lower cross-sections) ?