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DOE OSTI2024

Significance of radiative corrections on measurements of the EMC effect

Deep inelastic scattering (DIS) from nuclear targets probes the parton distribution functions (PDFs) in nuclei. Comparisons of the PDFs from heavy nuclei and the deuteron show deviations that demonstrate a non-trivial nuclear dependence to these distributions, referred to as the EMC effect. A global analysis of the worlds data on the EMC effect reveals tensions between different extractions. Precise measurements at Jefferson Lab, studying the dependence on both the quark momentum fraction, x, and nuclear mass, show systematic discrepancies among experiments, making the extraction of the A dependence of the EMC effect sensitive to the selection of datasets. Further, by comparing various methods and assumptions used to calculate radiative corrections, we have identified differences that, while not large, significantly impact the EMC ratios and show that using a consistent radiative correction procedure resolves this discrepancy, leading to a more coherent global picture, and allowing for a more robust extraction of the EMC effect for infinite nuclear matter.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

New Insights into the EMC Effect

Deep-inelastic scattering cross section ratios plotted as a function of the Bjorken scaling variable, xB, show an unexpected structure indicating that partonic structure in nuclei is different than in free nucleons. This phenomenon is commonly referred to as the EMC effect. Recent Jefferson Lab experimental data showed that the slope of the EMC effect in the 0.3 $<$ xB $<$ 0.7 scales as the local nuclear density rather than the average nuclear density. This result lead to the comparison of xB $>$ 1 short-range correlation plateaus versus the magnitude of the EMC effect slope, which shows a clear linear relation. In this talk, I will discuss the EMC effect and the short-range correlation plateaus and what this phenomenological relationship between the two implies.

Higinbotham, Douglas↗
DOE OSTI2010

Nuclear Scaling and the EMC Effect

For over a quarter century, scientists have tried to understand the unexpected structure in the deep-inelastic electron scattering cross section ratios of heavy nuclei to deuterium: a phenomenon known as the EMC effect. Results of recent Jefferson Lab EMC effect measurements, as well as recent nuclear scaling measurements, have both been attributed to the local nuclear environment and not properties of the bulk nuclear system. Motivated by this observation, we have found a phenomenological relationship between the magnitude of the nuclear scaling (Q$^2 > 1$ [GeV/c]$^2$ and $x_B > 1$) and slope of the EMC effect in valence quark region $(0.3 < x_B < 0.7)$.

Higinbotham, Douglas↗
DOE OSTI2013

The EMC Effect and High Momentum Nucleons in Nuclei

Recent developments in understanding the influence of the nucleus on deep-inelastic structure functions, the EMC effect, are reviewed. A new data base which expresses ratios of structure functions in terms of the Bjorken variable x{sub A}=AQ{sup 2}/(2M{sub A}q{sub 0}) is presented. Information about two-nucleon short-range correlations from experiments is also discussed and the remarkable linear relation between short-range correlations and the EMC effect is reviewed. A convolution model that relates the underlying source of the EMC effect to modification of either the mean-field nucleons or the short-range correlated nucleons is presented. It is shown that both approaches are equally successful in describing the current EMC data.

2N-SRC↗
DOE OSTI2022

Gluon EMC effects in nuclear matter

In this work, we investigate the gluonic structure of nuclei within a mean-field model of nuclear structure based upon the modification of the structure of a bound nucleon, with the nucleon described by the Nambu–Jona-Lasinio model. This approach has been shown to reproduce the European Muon Collaboration (EMC) effect, involving the ratio of the spin-independent structure functions of a heavier nucleus to that of the deuteron. It also predicts a significant nuclear modification for the spin structure functions, known as the polarized EMC effect. Here we report sizeable nuclear modifications of the gluon distributions (a ‘gluon EMC effect’) for the ratios of both the unpolarized and polarized gluon distributions in nuclear matter to those of a free nucleon.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

New hints to the cause of the EMC effect

Deep-inelastic scattering cross section ratios plotted as a function of Bjorken x show that quark structure in nuclei is different than in free nucleons. Recent EMC type data from Jefferson Lab's Hall C show that the slope in the 0.3 < x < 0.7 region scales as the local nuclear density and not the average nuclear density. This result led to the comparison between x > 1 short-range correlation plateaus and the magnitude of the EMC effect slope. A clear linear relation between the two effects has now been shown. In this paper, the EMC effect, the short-range correlation plateaus and a possible reason for a relationship between the two is discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the EMC effect in the deuteron

We have determined the structure function ratio $R^d_{\rm EMC}=F_2^d/(F_2^n+F_2^p)$ from recently published $F_2^n/F_2^d$ data taken by the BONuS experiment using CLAS at Jefferson Lab. This ratio deviates from unity, with a slope $dR_{\rm EMC}^{d}/dx= -0.10\pm 0.05$ in the range of Bjorken $x$ from 0.35 to 0.7, for invariant mass $W>1.4$ GeV and $Q^2>1$ GeV$^2$. The observed EMC effect for these kinematics is consistent with conventional nuclear physics models that include off-shell corrections, as well as with empirical analyses that find the EMC effect proportional to the probability of short-range nucleon-nucleon correlations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

EMC Effect of Tritium and Helium-3 from the JLab MARATHON Experiment

Measurements of the EMC effect in the tritium and helium-3 mirror nuclei are reported. The data were obtained by the MARATHON Jefferson Lab experiment, which performed deep inelastic electron scattering from deuterium and the three-body nuclei, using a cryogenic gas target system and the high resolution spectrometers of the Hall A Facility of the Lab. The data cover the Bjorken 𝑥 range from 0.20 to 0.83, corresponding to a squared four-momentum transfer 𝑄 2 range from 2.7 to 11.9 (GeV/𝑐) 2 , and to an invariant mass 𝑊 of the final hadronic state greater than 1.84 GeV/𝑐 2 . The tritium EMC effect measurement is the first of its kind. The MARATHON experimental results are compared to results from previous measurements by DESY-HERMES and JLab–Hall C experiments, as well as with few-body theoretical predictions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

MEASUREMENT OF THE EMC EFFECT OF THE TRITIUM NUCLEUS AT JEFFERSON LAB

Experiment E12-10-103 (MARATHON) was conducted in the Hall A Facility of JLab in the winter/spring of 2018 during the initial phase of the 12 GeV energy upgrade of the Lab. One goal of the experiment was the first measurement of the EMC effect of 3H. Four sealed gas targets were used during the experiment, 1H, 2H, 3H, and 3He. All measurements were in the deep inelastic scattering kinematical regime with large Q2 and W2, which are the four-momentum transfer squared and invariant mass squared of the final hadronic state in the inelastic scattering interaction, respectively. The range of Q2 and W2 were 3 < Q2 <12 (GeV/c)2 and 3.2 < W2 < 12.3 GeV/c2, respectively. The measurements spanned a wide range of the Bjorken variable x, between 0.19 and 0.83, where x = Q2/2M(E-E') is the momentum fraction carried by the struck quark in the interaction, with M being the nucleon mass. Knowledge of the EMC effect of light nuclei, such as 3H, will provide an opportunity to better understand the origin of the EMC effect.

Nycz, Michael R.↗
DOE OSTI2020

Measurement of the Ratio of the Neutron to Proton Structure Functions, and the Three-Nucleon EMC Effect in Deep Inelastic Electron Scattering Off Tritium and Helium-3 Mirror Nuclei

The proton and neutron structure functions Fp 2 and Fn 2, respectively are fundamental to understanding many studies in nuclear physics. They provide important information about quark distributions. For example, the ratio Fn 2/Fp 2 is one of the best measurements to find the ratio of d quark over u quark distribution inside the proton. While the calculations of structure functions and quark distributions are non-perturbative, they can be determined by the parameterization of experimental data. The understanding of Fn 2/Fp 2 and d/u as x -> 1 has a large influence on global fits and parameterization, and can be used to distinguish the non-perturbative models which give different predictions. However, Fn 2/Fp 2 measured using deuteron and hydrogen targets has large nuclear uncertainties at large x, because the nuclear effects in the deuteron become significant at large x. The MARATHON experiment, which ran in spring 2018 using the upgraded 11 GeV Jefferson Lab electron beam, employs a novel method. It performed deep inelastic scattering off tritium and helium-3 mirror nuclei to measure Fn 2/Fp 2 over the range x = 0.17 to x = 0.82. Since tritium and helium-3 are mirror nuclei, theoretical uncertainties largely cancel out in the ratio. The extracted Fn 2/Fp 2 has much smaller uncertainties compared with previous experiments at large x. The MARATHON experiment also provided results on the EMC effect for tritium and helium-3 nuclei. The results are considered essential for understanding the EMC effect. This thesis describes the MARATHON experiment, and presents results for Fn 2/Fp 2, and the EMC effect for tritium and helium-3.

Liu, Hanjie↗
DOE OSTI2012

New results on the the nuclear dependence of the EMC effect at large xB

Protons and neutrons are complex bound states of quarks and gluons, held together by the strong interactions of quantum chromo dynamics (QCD). Their structure may be modified inside of the dense environment of a nucleus. Detailed study of the modification of hadron properties in the nuclear environment provide a wealth of information on the nature of QCD. These modifications (known as the EMC effect) have been extensively studied, since the European Muon Collaboration discovered in 1983 that the structure functions and thus the quark distributions in nuclei are modified compared to those of free nucleons. Jefferson lab experiment E03-103 was designed for a precision measurement of the EMC effect in light nuclei, where reliable calculations can be performed, and to improve the precision on the EMC ratio of medium to heavy nuclei. Results from this experiment suggest that the nuclear dependence of the high $x_{B}$ quark distribution may depend on the local nuclear environment, rather than being a purely bulk effect. In this talk, I will discuss the new results from the E03103 experiment and the insights being obtained to the cause of the EMC effect from these studies.

Daniel, Aji↗
DOE OSTI2022

Disentangling the EMC effect: from free to bound nucleon structure

Deep inelastic scattering experiments using electron beams on fixed targets allow for the study of the structure of nucleons. While the structure of the free proton has been well measured, the free neutron structure and the modification of nucleon structure in the nuclear environment, the EMC effect, remain open questions. Studies suggest that the EMC effect may arise due to strongly-interacting nucleon-nucleon systems, referred to as short-range correlations. The BAND experiment at the Thomas Jefferson National Accelerator Facility seeks to probe the bound proton structure when in a strongly-interacting state, using spectator-tagged deep inelastic scattering. This thesis presents the results of the BAND experiment, demonstrating the proton is modified when strongly-interacting with the spectator neutron in deuterium. This thesis also explores efforts to describe inclusive and tagged deep inelastic scattering data within a uniform theoretical framework to explore nucleon structure modification effects and extract the free neutron structure.

Segarra, Efrain↗
DOE OSTI2019

The EMC Effect in A=3 Nuclei

The European Muon Collaboration (EMC) discovered an unexpected and puzzling result in 1983 when comparing the deep inelastic scattering(DIS) nuclear structure functions of Deuterium and Iron. The per-nucleon structure functions were found to be different for the two nuclei, rather than a simple average over the proton and neutron structure functions. In subsequent experiments, this phenomenon was confirmed for additional nuclei, with the magnitude approximately scaling with the density. The exact mechanism leading to this in- medium structure function modification has not been identified. I will discuss recent results from JLab exploring the EMC effect by using an electron beam to probe two mirror nuclei, Helium-3 and Tritium. iv

Bane, Jason↗
DOE OSTI2018

New Measurements of the EMC Effect in Hall-C

The x dependence of the EMC effect has been measured for a variety of nuclei in a multitude of experiments conducted over the past 35 years. Previous EMC ratio measurements for light nuclei (A?12) have shown a dependence on the local nuclear structure of nucleons and the associated modification to nuclear structure functions. The newly commissioned Super High Momentum Spectrometer (SHMS) in Hall-C has been used to collect inclusive electron scattering measurements on various light nuclei utilizing the 12 GeV CEBAF facility at Jefferson Lab. These data obtained during a portion of E12-10-008 includes previously unmeasured nuclei, namely 10B and 11B, and will therefore provide a comparison of nuclei which differ by just one nucleon. This will facilitate the extraction of the nucleon structure function as modified by the nuclear medium. Status of the target-ratio analysis of recently acquired E12-10-008 data will be discussed.

Pooser, Eric↗
DOE OSTI2012

A detailed study of the nuclear dependence of the EMC effect and short-range correlations

Because nucleons are closely packed in medium-to-heavy nuclei, one expects to observe density-dependent effects in their structure. Such effects can be seen in the nucleon momentum distribution in the form of a significant high-momentum tail related to the short-range interaction between nucleons, generating high-momentum short-range correlations (SRCs). High nuclear densities also imply overlap between neighboring nucleons, leading to the possible modification of their internal quark structure, which may contribute to the EMC effect. Recent Jefferson Lab experiments provided detailed information on both SRC contributions [1] and the EMC effect [2] in a range of light and heavy nuclei. We examine these results and previous data to make a detailed comparison of the A dependence of SRCs and nuclear quark distributions, along with a detailed comparison of the nuclear dependence of these two effects. We also examine the correlation between these effects, first studied in [3], in the context of different pictures of the underlying connection between these observables [4]. \\[4pt] [1] N. Fomin, et al., PRL 108 (2012) 092502\\[0pt] [2] J. Seely, et al., PRL 103 (2009) 202301\\[0pt] [3] L. Weinstein, et al., PRL 106 (2011) 052301\\[0pt] [4] J. Arrington, et al., arXiv:1206.6364 (2012)

Arrington, John↗
DOE OSTI2015

EMC effect: Past, Present, and Future

Since the discovery of the EMC effect over 30 years ago, it has been of great theoretical interest and studied in several experimental measurements. No unified picture arose to explain the underlying cause of per nucleon structure function modification in nuclei. Precise measurements on light nuclei from JLab’s 6 GeV era revitalized this research by showing that traditional A or density dependent models of this nuclear modification do not work. The measurements will be reviewed, discussed and preliminary data on heavy targets from JLab’s E03-103 will be presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Nuclear EMC effect in non-extensive statistical model

In the present work, we attempt to describe the nuclear EMC effect by using the proton structure functions obtained from the non-extensive statistical quark model. We record that such model has three fundamental variables, the temperature T, the radius, and the Tsallis parameter q. By combining different small changes, a good agreement with the experimental data may be obtained. Another interesting point of the model is to allow phenomenological interpretation, for instance, with q constant and changing the radius and the temperature or changing the radius and q and keeping the temperature.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Deep inelastic scattering from A = 3 nuclei: Nucleon structure and the EMC effect

The MARATHON experiment ran at Jefferson Laboratory in 2018, measuring deep inelastic scattering of 10.6 GeV electrons from the proton (p), deuterium (D), tritium ( 3 H), and helium-3 ( 3 He). MARATHON's experimental observables are cross section ratios, most notably 3 H/ 3 He. This ratio of mirror nuclei is used for a novel extraction of the nucleon structure function ratio $F^n_2$ /$F^p_2$ with minimal nuclear corrections. Determining leading-order $F^n_2$ /$F^p_2$ at high x provides important constrains on the ratio of nucleon valence quark distributions d/u. The ratios 3 H/D and 3 He/D allow a determination of the EMC effect in the lightest nuclei sensitive to possible isospin dependence of nuclear effects. Lastly, the D/p ratio allows a comparison of the MARATHON experiment to SLAC measurements, and provides data to which the A = 3 ratios can be renormalized. The MARATHON results provide new constraints on d/u. Additionally, the results emphasize the importance of higher-order effects in extracting $F^n_2$ /$F^p_2$ from DIS measurements, and can help constrain said effects. In the renormalization scheme applied in the MARATHON analysis, no significant isospin dependence of the EMC effect is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗