MMHT PDFs: updates and outlook

TL;DR

The paper advances MMHT PDFs by evaluating the impact of LHC jet data, including NNLO jet corrections, and incorporating new LHC Run data to refine uncertainties, notably reducing the strange sector and reshaping valence differences. A key finding is that correlated systematic uncertainties in ATLAS jet measurements can strongly influence fit quality, and decorrelating a small set of sources between rapidity bins can dramatically improve the description at NLO. NNLO jet corrections modestly worsen the fit, while the inclusion of new LHC data yields a marked reduction in the $s+ar s$ uncertainty and significant improvements to $u_V-d_V$, together with a slight shift in $\alpha_s(M_Z^2)$ to around $0.118$ at NNLO. In parallel, work toward MMHTQED integrates a photon PDF via a LUXqed-inspired input and coupled evolution, with early results showing good consistency with other photon-PDF determinations and tightening constraints on high-mass photon-initiated processes, enabling precision photon PDF phenomenology at the LHC.

Abstract

We present the latest results of studies within the MMHT PDF framework. We discuss the impact of the most recent ATLAS 7 TeV jet data, demonstrating that while a good fit can be achieved for individual jet rapidity bins, it is not possible to achieve a good description of the data when all bins are fitted. We examine the role that the experimental correlated systematic uncertainties play in this, and demonstrate that by simply decorrelating no more than two sources of error between rapidity bins a remarkably improved description of the data can be achieved. We then study the impact of NNLO corrections, showing that a mild decrease in the fit quality is produced. We also present the results of including new LHC $W$, $Z$, $W+c$ and $t\overline{t}$ data on the MMHT14 PDF set, showing that a marked decrease in the $s+\overline{s}$ uncertainty is in particular achieved. Finally, some discussion of the latest work towards the inclusion of the photon PDF within the MMHT framework is presented.

Figures (8)

• Figure 1: Comparison of NLO prediction and fit to ATLAS jet data Aad:2014vwa for two jet rapidity bins. Data/theory is plotted, with the data already shifted by the systematic uncertainties in order to achieve the best description. The displayed errors are purely statistical.
• Figure 2: Average squared sum of the systematic shift differences $(r_i-r_j)^2$ for the first four rapidity bins of the ATLAS 7 TeV jet data Aad:2014vwa.
• Figure 3: Data/theory fit as in Fig. \ref{['fig:jet1']}, with and without the labelled systematic errors decorrelated between jet rapidity bins.
• Figure 4: Comparison of NLO prediction and fit to ATLAS jet data Aad:2014vwa for two jet rapidity bins. Data/theory is plotted, without including the shifts due to the systematic uncertainties. Errors are the systematic and statistical added in quadrature.
• Figure 5: Impact on the gluon PDF of the ATLAS jet data, for the default and systematic error treatment and with errors jes21,62, defined in the text.