Abstract
By globally analyzing nuclear Drell-Yan data including all incident energies, the nuclear effects of nuclear parton distribution functions (nPDFs) and initial-state parton energy loss are investigated. Based on the Landau-Pomeranchuk-Migdal (LPM) regime, the calculations are carried out by means of analytic parametrizations of quenching weights derived from the Baier-Dokshitzer-Mueller-Peign -Schiff (BDMPS) formalism and using the new EPPS16 nPDFs. It is found that the results are in good agreement with the data and the role of the energy loss effect in the suppression of Drell-Yan ratios is prominent, especially for low-mass Drell-Yan measurements. The nuclear effects of nPDFs become more obvious with increasing nuclear mass number A, the same as the energy loss effect. By a global fit, the transport coefficient extracted is GeV2/fm. In addition, to avoid diminishing the QCD NLO correction to the data form of Drell-Yan ratios, separate calculations of the Compton differential cross section ratios at 120 GeV are performed, which provides a feasible way to better distinguish the gluon energy loss in Compton scattering. It is found that the role of the initial-state gluon energy loss in the suppression of Compton scattering ratios is not very important and disappears with the increase of .
Highlights
The nuclear Drell-Yan production of leptons provides an ideal tool to study the parton dynamics and the nuclear effects in cold nuclear matter
It is found that the calculations by EPPS16 nuclear parton distribution functions (nPDFs) together with the initial-state quark energy loss effect are in good agreement with the Drell-Yan data, especially for low-mass Drell-Yan measurements (E906-120GeV, NA3150GeV and NA10-140GeV), and the fitting degree is better than the results acquired with using EPPS16 nPDF and the fully coherent regime q = 0.07 − 0.09 GeV2/fm extracted from J/ψ measurements[2]
In the range 0.22 < xF < 0.73 at Ebeam = 120GeV, the initial-state quark energy loss is the dominant effect which induces the suppression of Compton scattering rations, the nuclear effects of gluon leading to the rise of Compton scattering rations are obvious, and the initial-state gluon energy loss has an influence on the suppression in small xF
Summary
The nuclear Drell-Yan production of leptons provides an ideal tool to study the parton dynamics and the nuclear effects in cold nuclear matter. By firstly including data constraints from the new LHC experiments, neutrino DIS measurements and low-mass Drell-Yan data (NA3[6], NA10[7] and E615[21]), EPPS16[22] is given, which significantly extends the kinematic reach of the data constraints and leads to a more reliable modification about the nuclear effects of nPDFs. The initial-state parton energy loss in nuclear Drell-Yan process is sensitive to the Landau-Pomeranchuk-Migdal (LPM) regime[23] due to the gluon formation time tf (tf ∝ 1/qT2 as expressed in Ref.[14]) being much smaller than the medium length LA for large values of qT , which is different from the fully coherent energy loss (FCEL)[24]. The mechanism of the medium-induced parton energy loss has not been understood completely, and due to lack of the reliable determination of the nuclear PDFs or the global analysis for precision data at different incident energies, there is no consensus about the role and the transport coefficient of the initial-state parton energy loss in nuclear Drell-Yan process.
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