Understanding forward BB hadron production

The LHCb collaboration has recently performed a measurement of the production rate of inclusive $B$ hadron production ($pp\to BX$) at both 7 and 13~TeV centre-of-mass (CoM) energies. As part of this measurement, the ratio of these two cross section measurements has been presented differentially in $B$ hadron pseudorapidity within the range of $\eta_B \in [2.0,5.0]$. A large tension ($4\sigma$) is observed for the ratio measurement in the lower pseudorapidity range of $\eta_B \in [2.0,3.0]$, where the data is observed to exceed theoretical predictions, while consistency is found at larger $\eta_B$ values. This behaviour is not expected within perturbative QCD, and can only be achieved by introducing ad-hoc features into the structure of the non-perturbative gluon PDF within the region of $x\in[10^{-3},10^{-4}]$. Specifically, the gluon PDF must grow extremely quickly with decreasing $x$ within this kinematic range, closely followed by a period of decelerated growth. However, such behaviour is highly disfavoured by global fits to proton structure. Further studies of the available LHCb $B$ and $D$ hadron cross section data, available for a range of CoM energies, indicate systematic tension in the (pseudo)rapidity region of $[2.0,2.5]$.Comment: 31 page

Feasibility of top quark measurements at LHCb and constraints on the large-xx gluon PDF

The forward LHCb acceptance opens interesting possibilities of studying precision Standard Model hard processes in a kinematical region beyond the reach of ATLAS and CMS. In this paper we perform a feasibility study for cross-section measurements of top quark pairs with the LHCb detector, with an analysis of signal and background rates for selected final states, and determine the potential precision achievable at $\sqrt{s} =$ 7 and 14~TeV. We then study the dependence of theoretical uncertainties on the pseudorapidity distribution of top quarks produced in pair production at NLO, and observe that a cross-section measurement at high pseudorapidity has enhanced sensitivity to probe the high-$x$ gluon PDF as compared to measurements in the central-region. Based on simulated pseudodata, the impact of a 14~TeV cross-section measurement on the gluon PDF and charge asymmetry is quantified.Comment: 25 pages, 14 figures, 8 tables. Extended PDF analysis to include ABM11 5flv nlo. Added summary plots of LHCb cross-sections. Include shift of gluon PDF central value for CT10, NNPDF sets assuming different pseudodata values. Matches version to be published in JHE

The small-x gluon from forward charm production: implications for a 100 TeV proton collider

We review the constraints on the small-x gluon PDF that can be derived by exploiting the forward D meson production data from the LHCb experiment at $\sqrt{s}=5,7$ and 13 TeV. We then discuss the phenomenological implications of the resulting improved small-x gluon for ultra-high energy astrophysics, in particular neutrino telescopes, as well as for the proposed Future Circular Collider (FCC) with $\sqrt{s}=100$ TeV. We illustrate how at the FCC even electroweak scale cross-sections can become sensitive to the small-x region of the quark and gluon PDFs, and then demonstrate how the addition of the LHCb heavy meson production measurements leads to a reduction of PDF uncertainties for various benchmark cross-sections.Comment: 5 pages, 4 figures, to appear in the proceedings of the XXV International Workshop on Deep-Inelastic Scattering and Related Subjects, 3-7 April 2017, University of Birmingham, U