最近的EMC效应测量和核标度测量的结果都归因于局部核密度效应，而不是体核系统的属性。这使我们观察到在0.3 < x_< 0.7 EMC data scale as the ratio of the x_B >B1的核标度平台中斜率的比值.利用这种关联，我们发展了一个唯象关系，再现了从3He到56Fe核的EMC效应的一般趋势和特征。
英文摘要：
Results of recent EMC effect measurements and nuclear scaling measurements have both been attributed to local nuclear density effects and not properties of the bulk nuclear system. This lead us to the phenomenological observation that the ratio of the slopes in the 0.3 < x_B < 0.7 EMC data scale as the ratio of the x_B > 1 nuclear scaling plateaus. Using this correlation, we developed a phenomenological relation which reproduces the general trends and features of the EMC effect for nuclei from 3He to 56Fe.
The relative contributions to the valence nuclear EMC effect in the deuteron arising from off-shell effects and Fermi motion are examined in models which include nuclear binding and off-shell effects. Contrary to expectations, the effect of Fermi motion overwhelms the off-shell effects for nucleons in short-range correlations (SRCs), calling into question the hypothesized causal connection between SRCs and the EMC effect.
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 di…
We study the parton distribution of nucleon and nuclear EMC effect in a statistical model. We find when we choose the parameters appropriately, the predictions given by pure statistical laws can fit the experimental data well in most range of $x$, this reveal statistical law play an important role in the parton distribution of nucleon.
We 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 $^3$He to $^3$H structure functions recently obtained by the MARATHON experiment at Jefferson Lab. Our 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. We find that while the MARATHON data yield relatively weak constraints on the $F_2^n/F_2^p$ neutron to proton structure function ratio and on the $d/u$ PDF ratio, …
The EMC effect in deuterium and helium-3 is studied using a convolution formalism that allows isolating the impact of high-momentum nucleons in short-ranged correlated (SRC) pairs. We assume that the modification of the structure function of bound nucleons is given by a universal (i.e. nucleus independent) function of their virtuality, and find that the effect of such modifications is dominated by nucleons in SRC pairs. This SRC-dominance of nucleon modifications is observed despite the fact that the bulk of the nuclear inelastic scattering cross-section comes from interacting with low-momentu…
We present our results for a flavor-dependent EMC effect based on the nIMParton nuclear PDFs, in which the $x$-dependence is described with a nucleon swelling model. The nuclear correction from nucleon swelling is considered through a modification of the initial valence quark distributions instead of a dynamical rescaling. To probe the flavor-dependence of the model, the experimental observables are calculated applying nIMParton nuclear modifications for various experiments: parity-violating deep inelastic scattering on nuclear target, pion-induced Drell-Yan, and W-boson production in proton-n…
Nuclear structure functions and EMC effect in a relativistic deuteron
University of Science and Technology of China（中国科学技术大学）；Lebedev Physical Institute（列别捷夫物理研究所）；Anhui Center for Fundamental Sciences in Theoretical Physics（安徽理论物理基础科学中心）
The EMC effect is studied by using the GLR-MQ-ZSR equation with minimum number of free parameters, where the nuclear shadowing effect is a dynamical evolution result of the equation, and nucleon swelling and Fermi motion in the nuclear environment deform the input parton distributions. Parton distributions of both proton and nucleus are predicted in a unified framework. We show that the parton recombination as a higher twist correction plays an essential role in the evolution of parton distributions either of proton or nucleus. We find that the nuclear antishadowing contributes a part of enhan…
Double parton scattering off nuclei and the double-EMC effect
Università degli Studi di Perugia（佩鲁贾大学）；INFN Sezione di Perugia（意大利国家核物理研究所佩鲁贾分部）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；Université de Liège（列日大学）；Università di Roma Tor Vergata（罗马第二大学）；INFN Sezione di Roma Tor Vergata（意大利国家核物理研究所罗马第二大学分部）；Istituto Nazionale di Fisica Nucleare Sezione di Perugia（意大利国家核物理研究所佩鲁贾分部）
In this article we employ the nuclear EMC effect to extract the parton distribution functions (PDFs) inside the Lead (Pb) and Gold (Au) nuclei. Extracted PDFs are utilized to obtain the transverse momentum dependent (TMD) ones, using the computing codes like Pythia 8 or MCFM-10. Through this procedure TMDPDFs for charm and bottom quarks in Au at $\sqrt{s_{NN}}=200\;GeV$, Pb at $\sqrt{s_{NN}}=2.76\;TeV$ and $\sqrt{s_{NN}}=5.02\;TeV$ are calculated. To evaluate the validity of results and investigate the influence of nuclear EMC effect, the numerated TMDs are used as input to estimate heavy quar…
The ratios of the in-medium to free nucleon structure functions for the unpolarized and polarized cases are obtained using the MIT bag model for the free case, along with the QMC model to incorporate the in-medium modifications of the structure functions. As discussed in earlier work, the observed nuclear EMC effect is reasonably well described. This gives us confidence to investigate the predictions of the model for the polarized EMC effect, the ratio $g_1^*(x)/g_1(x)$ for a bound proton to that of a free proton. This ratio is found to be substantially different from unity and very similar in…
The CLAS collaboration at Jefferson Laboratory has compared nuclear parton distributions for a range of nuclear targets and found that the EMC effect measured in deep inelastic lepton-nucleus scattering has a strongly "isophobic" nature. This surprising observation suggests short-range correlations between neighboring $n$ and $p$ nucleons in nuclear wavefunctions that are much stronger compared to $p-p$ or $n-n$ correlations. In this paper we propose a definitive experimental test of the nucleon-nucleon explanation of the isophobic nature of the EMC effect: the diffractive dissociation on a nu…
We show that the empirical linear relation between the magnitude of the EMC effect in deep inelastic scattering on nuclei and the short range correlation scaling factor $a_2$ extracted from high-energy quasi-elastic scattering at $x\ge 1$ is a natural consequence of scale separation and derive the relationship using effective field theory. While the scaling factor $a_2$ is a ratio of nuclear matrix elements that individually depend on the calculational scheme, we show that the ratio is independent of this choice. We perform Green's function Monte Carlo calculations with both chiral and Argonne…
In this paper, we examine the hypothesis that the nuclear EMC effect comes merely from the N-N SRC pairs inside the nucleus and that the properties of N-N SRC pair are universal among the various nuclei, using the conventional $x$-rescaling model for the EMC effect. With the previously determined effective mass of the short-range correlated nucleon and the number of N-N SRC pairs estimated, we calculate the EMC effect of various nuclei within the $x$-rescaling approach. From our calculations, the nuclear EMC effect due to the mass deficits of the SRC nucleons is not enough to reproduce the obs…
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 sho…
In this article, using Laplace transformation , an analytical solution is obtained for the DGLAP evolution equation at the next-to-leading order of perturbative QCD. The technique is also employed to extract, in the Laplace $s$-space, an analytical solution for the nuclear structure function, $F_2^A(x, Q^2)$. Firstly, the results for separate nuclear parton distributions for all parton types are presented which include valence quark densities, the anti-quark and strange sea PDFs and finally the gluon distribution. Based on the Laplace transformation, the obtained parton distribution functions …
Semi-inclusive Deep Inelastic Scattering off Few-Nucleon Systems: Tagging the EMC Effect and Hadronization Mechanisms with Detection of Slow Recoiling Nuclei
应用重子电荷和能量动量的精确QCD求和规则，我们证明了如果核子是核波函数的唯一自由度，则核的结构函数将是在相同的Bjorken x = AQ^2/2（p_Aq）0.05处核子分布的加和< 0.5 up to very small Fermi motion corrections if x>.因此，EMC比与1的差异揭示了原子核中存在非核子自由度。利用精确的QCD求和定则，我们证明了实验研究中所用的比值R_A（x_p，Q_2），其中x_p = Q_2/2q_0m_p，即使在一个核只由小动量核子组成的情况下，也偏离1。与x_p图相比，使用Bjorken x图可使R_A（x，Q^2）进一步减小。核库仑场的洛伦兹变换明确地给出了等效光子对核部分子波函数光子分量的相干贡献。对于A~200，光子携带原子核光动量的~0.0065部分，这几乎补偿了数据分析在Bjorken x和x_p方面的差异。直接观测原子核中大的、主要是核子的短程关联，对x>0.6的EMC效应的大多数模型提出了严重的挑战。这些数据与强子EMC效应反映核子间相互作用的涨落的情形是一致的，这种涨落是由于相互作用核子中颜色分布的涨落引起的。这种情况的动态实现是这样的模型，其中x > 0.5的3q（3qg）组态与附近核子的相互作用较弱，导致抑制这种组态，从而给出正确的EMC效应。展望了未来的研究方向和挑战性问题。
