Measurements of open beauty and charm production cross sections in deep inelastic $ep$ scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections for beauty and charm production are obtained in the kinematic range of photon virtuality 2.5 ≤ Q$^2$ ≤ 2000 GeV$^2$ and Bjorken scaling variable 3 · 10$^{−5}$ ≤ x ≤ 5 · 10$^{−2}$. The combination method accounts for...
We present the possibility of intrinsic (non-perturbative) charm in parton distribution functions (PDF) of the proton, within the context of the CT14 next-to-next-to-leading order (NNLO) global analysis. Different models of intrinsic charm are analysed and compared. The correlations between the value of the charm-quark mass and the allowed amount of intrinsic charm is also discussed.
We present an updated and improved extraction of the low-$x$ gluon distribution from the HERA and LHCb (7 TeV and preliminary 13 TeV) exclusive $J/\psi$ production data in the context of $k_T$ factorisation. Critically, we use a more precise expression for the photon flux and re-calculate the rapidity gap survival factors.
In collinear factorisation exclusive $J/\psi$ photoproduction...
The small-$x$ gluon in global fits of parton distributions is affected by large uncertainties from the lack of direct experimental constraints. In this work we provide a precision determination of the small-$x$ gluon from the exploitation of forward charm production data provided by LHCb for three different centre-of-mass (CoM) energies: 5 TeV, 7 TeV and 13 TeV. The LHCb measurements are...
I discuss the impact of recent measurements of top-pair differential distributions from ATLAS and CMS at $\sqrt{s}=8$ TeV on the gluon parton distribution function (PDF). The new data is included in a global QCD analysis of PDFs at next-to-next-to-leading order (NNLO) accuracy, based on the NNPDF methodology. I comment on the compatibility between ATLAS and CMS measurements and I show how a...
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...