Probing proton intrinsic charm in photon or Z boson production accompanied by heavy jets at LHC

TL;DR

This paper proposes a sensitive observable based on cross section ratios in proton collisions at the LHC to detect intrinsic charm in the proton, showing that the ratio's behavior at high transverse momentum can reveal the presence of intrinsic charm.

Contribution

It introduces a new ratio of differential cross sections that is highly sensitive to intrinsic charm and less affected by theoretical uncertainties, aiding its detection at the LHC.

Findings

The ratio can be flat or increasing at high p_T if intrinsic charm exists.

Without intrinsic charm, the ratio decreases with increasing p_T.

Ratios of integrated cross sections are largely independent of theoretical uncertainties.

Abstract

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 for $p_T$-spectra, which significantly depend on these uncertainties.