arXiv : How to include exclusive $J/\psi$ production data in global PDF analyses

Flett, C.A.; Martin, A.D.; Jones, S.P.; Teubner, T.; Ryskin, M.G.

doi:10.1103/PhysRevD.101.094011

Article
Report number	arXiv:1908.08398 ; CERN-TH-2019-137 ; IPPP/19/65 ; LTH 1213
Title	How to include exclusive $J/\psi$ production data in global PDF analyses
Author(s)	Flett, C.A. (Liverpool U., Dept. Math.) ; Jones, S.P. (CERN) ; Martin, A.D. (Durham U., IPPP) ; Ryskin, M.G. (Durham U., IPPP ; St. Petersburg, INP) ; Teubner, T. (Liverpool U., Dept. Math.)
Publication	2020-05-14
Imprint	2019-08-22
Number of pages	9
Note	16 pages, 6 figures, text improved, references added
In:	Phys. Rev. D 101 (2020) 094011
DOI	10.1103/PhysRevD.101.094011
Subject category	hep-ph ; Particle Physics - Phenomenology
Accelerator/Facility, Experiment	CERN LHC ; LHCb
Abstract	We compare the cross section for exclusive $J/\psi$ photoproduction calculated at NLO in the collinear factorization approach with HERA and LHCb data. Using the optimum scale formalism together with the subtraction of the low $k_t<Q_0$ contribution from the NLO coefficient function to avoid double counting we show that the existing global parton distribution functions (PDFs) are consistent with the data within their uncertainties. However, at low $x$ the uncertainties of the present global PDFs are large. On the other hand, the accuracy of the LHCb data are rather good. Therefore, these data provide the possibility to directly measure the gluon PDF over the very large interval of $x$, $10^{-6}<x<10^{-2}$, at a fixed low scale.
Copyright/License	preprint: (License: CC-BY-4.0) publication: © 2020-2024 authors (License: CC-BY-4.0), sponsored by SCOAP³

$\sf{LO and LO+NLO contributions to the imaginary part of the $\gamma p \to V +p$ amplitude as a function of the $\gamma p$ centre-of-mass energy, $W$, with $\mu_F = m_c$ before (left panel) and after (right panel) the double counting correction has been implemented, as explained in the text. The dashed, continuous and dot-dashed (red) curves correspond to three choices of the factorization scale $\mu_f$: namely $\mu_f^2=2m_c^2,~m_c^2,~Q_0^2,$ respectively, where $m_c^2=M^2_\psi /4=2.4$ GeV$^2$. Here $Q_0=1.3$ GeV is the starting scale of the input PDFs from CTEQ6.6 \cite{CTEQ6.6} which were used. The dotted black curve is the LO contribution.}$ $\sf{(a) LO contribution to $\gamma p \to V +p$. (b) NLO quark contribution. For these graphs all permutations of the parton lines and couplings of the gluon lines to the heavy-quark pair are to be understood. Here the momentum $P\equiv (p+p^\prime)/2$ and $l$ is the loop momentum. Note that the momentum fractions of the left and right partons are $x=X+\xi$ and $x'=X-\xi$ respectively; for the upper gluons we have $x' \ll x$ and so $x\simeq 2\xi$.}$ $\sf{(a) LO contribution to $\gamma p \to V +p$. (b) NLO quark contribution. For these graphs all permutations of the parton lines and couplings of the gluon lines to the heavy-quark pair are to be understood. Here the momentum $P\equiv (p+p^\prime)/2$ and $l$ is the loop momentum. Note that the momentum fractions of the left and right partons are $x=X+\xi$ and $x'=X-\xi$ respectively; for the upper gluons we have $x' \ll x$ and so $x\simeq 2\xi$.}$ Show more plots

Corresponding record in: Inspire

Back to search

記錄創建於2019-08-25，最後更新在2022-10-21

相似記錄

Article from SCOAP3: