[Jlab-seminars] Virtual Physics Division Seminar: The MARATHON Marathon; Hainjie Liu, Christopher Cocuzza, & Efrain Segarra

[Stephanie Tysor]

Virtual Physics Division Seminar

The MARATHON Marathon

Hainjie Li, Christopher Cocuzza, Efrain Segarra

University of Massachusetts Amherst, Temple University, Massachusetts Institute of Technology


The recently released MARATHON results have generated considerable interest with two derivative papers already on the arXiv. This Friday we will have a MARATHON Marathon with Hainjie Li (Univ. of Mass. Amherst), Christopher Cocuzza (Temple), and Efrain Segarra (MIT) presenting these new results. We will loosely follow an APS invited session format with each presenter having thirty minutes to present though we have allow considerably more time for questions and discussions.

Friday, April 30, 2021
12:00 pm – 2:30 pm
https://bluejeans.com/245615984



Abstracts:

The Measurement of the Nucleon F2n/F2p Structure Function Ratio from the MARATHON Experiment



Hanjie Liu (Univ. of Mass. Amherst)



The ratio of neutron structure function to that of proton F2n/F2p is one of the best methods to extract d/u quark ratio.  While the F2n/F2p extracted from deuteron deep inelastic scattering data has large systematic uncertainty at high x (x>0.7) from model dependent nuclear corrections, the MARATHON experiment, which ran in spring 2018, uses a novel method. It performed deep inelastic electron scattering off tritium and helium-3 mirror nuclei to measure F2n/F2p over the range x=0.195 to x=0.825. Since tritium and helium-3 are mirror nuclei, theoretical uncertainties are expected to be largely canceled out in the ratio. The results of F2n/F2p from the MARATHON experiment was recently posted in arxiv. An overview of the MARATHON experiments and the results will be presented.




First Evidence of Isovector EMC effect from Global QCD Analysis with MARATHON Data


Christopher Cocuzza (Temple)


I will report the results of a Monte Carlo global QCD analysis of unpolarized parton distribution functions (PDFs), including for the first time constraints from ratios of 3He to 3H structure functions recently obtained by the MARATHON experiment at Jefferson Lab.  This simultaneous analysis of nucleon PDFs and nuclear effects in A=2 and A=3 nuclei reveals the first indication for an isovector nuclear EMC effect in light nuclei.  Thus, while the MARATHON data yield relatively weak constraints on the F2n/F2p neutron to proton structure function ratio and the d/u PDF ratio, the data suggest a strongly enhanced nuclear effect on the d-quark PDF in the bound proton.




Nucleon Off-shell Structure and the Free Neutron Valence Structure from A=3 Inclusive Electron Scattering


Efrain Segarra (MIT)


While there are large amounts of proton structure measurements, data on the structure of the neutron is much more spars as experiments typically extract the structure of neutrons from measurements of light atomic nuclei using model-dependent corrections for nuclear effects.   Here we evaluate the model dependence of this extraction by examining a wide range of models including the effect of using instant-form and light-cone nuclear wave functions and several different parameterizations of nucleon modification effects, including those with and without isospin dependence. We find that, while the data cannot differentiate among the different models of nuclear structure and nucleon modification, they consistently prefer a neutron-to-proton structure function ratio of at xB→1 of ∼0.4 with a typical uncertainty (1σ) of ∼0.05 and ∼0.10 for isospin-independent and isospin-dependent modification models, respectively. While strongly favoring SU(6) symmetry breaking models based on perturbative QCD and the Schwinger-Dyson equation calculation, the MARATHON data do not completely rule out the scalar di-quark models if an isospin-dependent modification exist.


Friday, April 30, 2021
12:00 pm – 2:30 pm
https://bluejeans.com/245615984




Stephanie Tysor
Hall A/C Administrative Assistant
Physics Division
Jefferson Lab
757-269-6005


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