Collider test of proton intrinsic charm in γ ( Z )+ c ( b ) production by pp collisions
2017 November 24
2018 January 16
We consider an observable very sensitive to the non-zero intrinsic charm (IC) contribution to the proton density.
It is the ratio between the differential cross sections of the photon or $Z$-boson and $c$-jet
production in the $pp$ collision, $\gamma(Z) + c$, and the $\gamma(Z)$ and the $b$-jet production.
It is shown that this ratio can be approximately flat or increasing at large $\gamma(Z)$ transverse momenta $p_T$
and their pseudo-rapidities $1.5 < \eta < 2.4$ if the IC contribution is taken into account.
On the contrary, in the absence of the IC this ratio decreases as $p_T$ grows.
We also present the ratios of the cross sections integrated over $p_T$ as a function of the IC probability $w$.
It is shown that these ratios are mostly independent on the theoretical uncertainties, and such predictions could
therefore be much more promising for the search for the intrinsic charm signal at the LHC compared to the predictions on pT-spectrta of photons or Z-bosons.