# LHAPDF grids from HF-LHC-RW-2017

This page links to the LHAPDF grids of  “Reweighted nuclear PDFs using Heavy-Flavor Production Data at the LHC: nCTEQ15rwHF & EPPS16rwHF” by A. Kusina, J.P. Lansberg, I. Schienbein and H.S. Shao (2020) (http://arxiv.org/pdf/2012.11462.pdf) based on the nPDF reweighting analysus published in Phys.Rev.Lett. 121 (2018) no.5, 052004 (http://arXiv.org/pdf/1712.07024.pdf)

All the LHAPDF files provided here are at 90% CL (same as the original EPPS16 and nCTEQ15 nPDFs). On the other hand, only N_eigen error PDFs are provided (one error PDF per eigenvector direction/free parameter, i.e. is 16 in case of nCTEQ15 and 20 in case of EPPS16). In case of symmetric errors this is sufficient for calculating the PDF uncertainty. The formula that should be used for this purpose is:
delta_f = sqrt(sum_{i=1}^{N_eigen}(f_i-f_0)^2)
or for a PDF-dependent observable, X:
delta_X = sqrt(sum_{i=1}^{N_eigen}(X(f_i)-X(f_0))^2)

One should note that this is different from the original EPPS16 and nCTEQ15 PDF sets which provided 2*N_eigen error PDFs (32 for nCTEQ15 and 40 for EPPS16) which then require using the following formula for calculating PDF uncertainties:
delta_f = 0.5*sqrt(sum_{k=1}^{Neigen}(f_{2*k-1}-f_{2*k})^2)

As for the PDF sets, they are divided into directories based on the original nPDF set (nCTEQ15 or EPPS16), on the nucleus (Pb or Au), and on the data type that was used for the reweighting (J\Psi, D-meson, B->J\Psi). This gives total of 12 (2x2x3) directories and each of these directories contains 4 reweighted PDF sets: 3 sets for different scale choices: {\mu_0, 0.5*\mu_0, 2.0*\mu_0} and an additional set combining the uncertainties of the three scale choices.

For details on how to use the reweighted PDF sets, we recommend consulting Sec.3 and 4 of ref. arXiv:2012.11462 as well as the original analysis: PRL 121 (2018) 052004, arXiv:1712.07024.

Note that the provided LHAPDF files have dummy "SetIndex" indices and these should not be used. As such, one should initialize PDF sets by their names.



EPPS16

Pb

Au

nCTEQ15

Pb

Au