Alka Upadhyay
We conclude that nucleon is a many body complex system whose low-energy behaviour is determined mainly by strong interaction. Non-perturbative approach to QCD, such as QCD sum rule and the QCD based effective theory, and the models such as a statistical model, have a complementary role in exposing different aspects of nucleonic properties.
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The eikonal model must be denoted as strongly preferable for the analysis of elastic high-energy hadron collisions. The given approach allows to derive corresponding impact parameter profiles that characterize important physical features of nucleon collisions, e.g., the range of different forces. The contemporary phenomenological analysis of experimental data is, however, not able to determine these profiles unambiguously, i.e., it cannot give the answer whether the elastic hadron collisions are more central or more peripheral than the inelastic ones. However, in the collisions of mass objects…
It is demonstrated that new JLAB proton polarization data, which are in a rather strong disagreement with the proton electric form factor data in the space-like region obtained by Rosenbluth technique, are consistent with all known form factor properties, including also the QCD asymptotics, but they require an existence of a zero (i.e. a diffraction minimum) around $t$=15 GeV$^2$ of the proton electric form factor. The latter leads to a change of our knowledge about the charge distribution inside of the proton.
Aspects of Nucleon Chiral Perturbation Theory
本文综述了重子CHPT框架下核子性质计算的最新进展。主题包括：康普顿散射，$πN$散射，低能量常数的解剖和诱导的赝标量形状因子。
Theory Aspects of Double-Spin Asymmetries in Proton-Nucleon Collisions
强子-强子碰撞中两种自旋不对称性的研究，以非极化碰撞机器无法实现的方式探索基本粒子相互作用的细节。质子自旋是如何通过$ΔG$和$Δ\bar{q}$在其组成部分之间分布的，这是可以理解的。测量耦合，进一步了解喷流结构和发现新的物理学都是偏振对撞机的可能性。自旋物理学也可以加深我们对更高扭曲行为以及微扰和非微扰物理学之间过渡的理解。本报告概述了双自旋物理学。(Talk 1995年8月28日至31日在德国DESY-Zeuthen举行的“HERA自旋物理学前景”讲习班上提出的。
Aspects of Nucleon Compton Scattering
本文研究了在包含${\cal O} (q^4)$阶所有项的重子手征微扰理论中自旋平均核子前向康普顿散射振幅。自旋平均前向康普顿散射振幅的手征预测与光子能量$ω\le 110$ MeV的数据吻合得很好。我们还评估了核子的电磁康普顿极化率，这个顺序，并讨论了进入这些量的手征展开的各种计数器项的不确定性。
The next-to-leading order chiral pion-nucleon Lagrangian contains seven finite low-energy constants. Two can be fixed from the nucleon anomalous magnetic moments and another one from the quark mass contribution to the neutron-proton mass splitting. We find a set of nine observables, which to one loop order do only depend on the remaining four dimension two couplings. These are then determined from a best fit. We also show that their values can be understood in terms of resonance exchange related to $Δ$ excitation as well as vector and scalar meson exchange. In particular, we discuss the role o…
The ETH model of the pion-nucleon ($πN$) interaction contains $t$-channel $σ$- and $ρ$-exchange graphs, as well as the $s$- and $u$-channel contributions with the well-established $s$ and $p$ baryon states with masses below $2$ GeV as virtual particles; the model amplitudes obey crossing symmetry and isospin invariance. In the present work, we give the analytical expressions for the model contributions to the $K$-matrix elements up to (and including) the $f$ waves. We also extract a new phase-shift solution after performing a partial-wave analysis of meson-factory $π^\pm p$ elastic-scattering …
A brief review of the pion-nucleon sigma-term is given. Aspects of both chiral perturbation theory and phenomenology are discussed.
Open problems in the study of the nucleon structure using electromagnetic probes are discussed. The focus is on experimental aspects in the regime of strong interaction QCD. Significant progress in our understanding of the nucleon structure in this domain of QCD may be expected in the first decade of the next millenium. This is due to major experimental and theoretical efforts currently underway in this field.
Our knowledge of the nucleon spin structure has greatly improved over the last twenty years or so, but still many fundamental questions remain unsolved. I will try to review some of the puzzling aspects of the structure of the nucleon spin, in particular, what is known, what remains to be discovered and the prospects for the near future. I will also focus on some current activities in QCD spin physics.
The paper presents an extension and a refinement of our previous work on the extraction of the doubly virtual forward Compton scattering amplitude on the lattice by using the background field technique, Phys. Rev. D 95, 031502 (2017) (arXiv:1610.05545). The zero frequency limit for the periodic background field is discussed, in which the well-known result is reproduced. Further, an upper limit for the magnitude of the external field is established for which the perturbative treatment is still possible. Finally, the framework is set for the evaluation of the finite-volume corrections allowing f…
Our knowledge on the nucleon spin structure has greatly improved over the last twenty years or so, but still many fundamental questions remain unsolved. I will try to review some of the puzzling aspects of the origin of the nucleon spin. I will emphasize the connection with several sum rules and, when using this tool, the relevance of some kinematic regions for testing them in the QCD dynamics framework.
We analyse the calculations of deep inelastic structure functions of free nucleons by QCD sum rules method,carried out by others.We present our results of calculation of the distribution of valence quarks in nucleon placed into the nuclear matter.We show that the change in distribution has typical EMC shape.We discuss possible application of the method to investiga- tion of other aspects of deep-inelastic processes.We analyse also the limits of possibilities of the approach.
PERTURBATIVE QCD AND NUCLEON STRUCTURE FUNCTIONS.
本文回顾了基于算子乘积展开的微扰QCD的基本内容，并以教学的方式分析了核子结构函数。我们解释了QCD结果与部分子模型之间的非平凡关系，特别是为了理解近年来备受关注的极化核子结构函数。
Several topics in hadron physics at different scales of resolution are discussed. First, deep-inelastic scattering from nucleons and nuclei is viewed in a light-cone coordinate space picture. Then the smooth transition from parton to hadron degrees of freedom is demonstrated by using a generalized Q^2-dependent polarizabilities of the nucleon. Turning to low energy QCD we summarize recent developments related to the role of strange quarks in Chiral SU(3) Dynamics, a non-perturbative coupled channel approach to hadronic processes. Finally we elaborate on a unification of QCD Sum Rules with aspe…
We review several aspects of flavour-diagonal CP violation, focussing on the role played by the electric dipole moments (EDMs) of leptons, nucleons, atoms and molecules, which consitute the source of several stringent constraints on new CP-violating physics. We dwell specifically on the calculational aspects of applying the hadronic EDM constraints, reviewing in detail the application of QCD sum-rules to the calculation of nucleon EDMs and CP-odd pion-nucleon couplings. We also consider the current status of EDMs in the Standard Model, and on the ensuing constraints on the underlying sources o…
The Spin Structure of the Nucleon
研究核子自旋结构，揭示其复杂性及QCD理论的发展。
Phenomenological Aspects of Isospin Violation in the Nuclear Force
唯象拉格朗日量和量纲幂计数被用来评估核子-核子力中的同位旋破坏。研究了$πNN$耦合常数（包括Goldberger-Treiman差异）、电荷对称性破缺和介子混合模型。利用手征微扰理论对同位旋破坏的$πNN$耦合常数进行了单圈分析。介子混合模型和$^3$ He - $^3$ H质量差也讨论了自然的背景下。
Physics and programming aspects are discussed for a Fortran 77 Monte Carlo program to simulate complete events in deep inelastic lepton-nucleon scattering. The parton level interaction is based on the standard model electroweak cross sections, which are fully implemented in leading order for any lepton of arbitrary polarization, and different parametrizations of parton density functions can be used. First order QCD matrix elements for gluon radiation and boson-gluon fusion are implemented and higher order QCD radiation is treated using parton showers. Hadronization is performed using the Lund …
This is the summary of the working group on Goldstone Boson Production and Decay of the Chiral Dynamics Workshop in Mainz, September 1-5, 1997. For the production aspects we discuss $π^0$ and $η$ production in nucleon-nucleon collisions and the behaviour of hadrons in various sum rules. For the decays we present a discussion on various $K$, $η$ and $π$ decay channels. Other aspects discussed are a new treatment of meson-meson scattering, the light-by-light contribution to the muon anomalous magnetic moment and progress in various aspects of the $p^6$ generating functional in the mesonic sector…
Some aspects of transversity
指出了超相对论费米子的横向极化与螺旋度的特殊性。对于无质量费米子，定义了一个协变的横向四维矢量，直到一种规范变换。定义了核子中夸克的横度分布。它可能与重子的磁偶极矩或电偶极矩有关。列举了硬过程中的横向自旋不对称性的近似手征不变性的后果。本文介绍了柯林斯提出的测量末位夸克横向极化的“剪切喷流效应”。
The problem of the structure of nucleons and their interaction in the concept of nonperturbative QCD is discussed as an approach to studying the transformation of current quarks into constituent ones and the search for the mechanism of such a transformation, creating the bulk of the nucleon mass. Attention is drawn to the possibilities offered by studying central nucleon-nucleon collisions in this aspect.
Hadron properties are studied at hot medium using the quark sigma model. The quark sigma model is extended to include eighth-order of mesonic interactions based on some aspects of quantum chromodynamic (QCD) theory. The extended effective potential tends to the original effective potential when the coupling between the higher order mesonic interactions equal to zero. The field equations have been solved in the mean-field approximation by using the extended iteration method. We found that the nucleon mass increases with increasing temperature and the magnetic moments of proton and neutron incre…
We consider one aspect of the theoretical foundations of polarization experiments on elastic scattering of electrons on protons yielding form factor ratios incompatible with those that are extracted from nonpolarization experiments. We analyze the consequences of abandoning the assumption that the nucleon is a Dirac particle. We show that the process of elastic scattering of electrons on nucleons is described by the same formulas, irrespective of the proper Lorentz group representation associated with the nucleon as a particle with the rest spin 1/2.
We report the current status of exploring the dynamical aspect of the excited nucleon states through the comprehensive coupled-channels analysis of meson production reactions at the Excited Baryon Analysis Center of Jefferson Lab.
The Strange Spin of the Nucleon
最近一系列关于极化轻子-核子散射的实验为核子的故事提供了一个奇怪的新转折，其中的一些方面将在这些讲座中进行回顾。在第一讲中，我们回顾了在分析极化结构函数数据时出现的一些问题，特别着重于高阶QCD微扰理论的重要性和处理。在第二讲中，对"EMC自旋效应”的一些可能的解释进行了综述，主要是在手征孤子（Skyrmion）方法中，但也有与轴向$U(1)$异常相关的解释。本讲座还讨论了从最近的LEAR数据中得到的核子波函数中的$\bar{s} s$成分的其他迹象，并讨论了对该成分模型的检验。最后，第三讲回顾了偏振结构函数测量的实验，以寻找冷暗物质粒子，如最轻的超对称粒子和轴子的影响，在简要回顾了冷暗物质的天体物理和宇宙学证据。
I review recent theoretical results on polarized deep inelastic lepton nucleon scattering. Some specific issues, like $Q^2$ evolution of structure functions, the small $x$ behaviour, and the determination of polarized parton densities, are discussed in some detail.
Spin effects in lepton-nucleon reactions
我们总结了在上述工作组会议的讨论中被认为特别重要的一些理论问题。
The equivalent photon content of polarized and unpolarized nucleons (protons, neutrons), utilized in Weizsäcker--Williams approximations, are presented. For this purpose a new expression for the elastic photon component of a polarized nucleon is derived. The inelastic photon components are obtained from the corresponding momentum evolution equations subject to the boundary conditions of their vanishing at some low momentum scale. The resulting photon asymmetries, important for estimating cross section asymmetries in photon induced subprocesses are also presented for some typical relevant momen…
A possible resolution to the question of where the nucleon gets some portion of its internal angular momentum, not carried by the valence quarks, is given in terms of the electromagnetic field angular momentum of the nucleon. This field angular momentum is similiar in origin to that of the Thomson dipole (an electric charge and a magnetic monopole), but arises from the interaction of the quark electric charges and magnetic dipoles. Rough, order of magnitude calculations show that such a field angular momentum could provide some of the nucleon's spin. Under certain assumptions QCD should also e…
In this opening talk I will address some issues that exemplify the theoretical progress that has been made and is to be expected in the field of meson-nucleon physics. My emphasis will be on performing precision calculations to test aspects of QCD, including also electroweak probes. In addition, I discuss the problems and opportunities related to the strange quark sector.
We analyse the calculations of deep inelastic structure functions of free nucleons by QCD sum rules method,carried out by others.We present our results of calculation of the distribution of valence quarks in nucleon placed into the nuclear matter.We show that the change in distribution has typical EMC shape.We discuss possible application of the method to investigation of other aspects of deep-inelastic processes.We analyse also the limits of possibilities of the approach.
In order to illustrate the capabilities of COMPASS using a hadronic beam, I review some of the azimuthal asymmetries in hadronic collisions, that allow for the extraction of transversity, Sivers and Boer-Mulders functions, necessary to explore the partonic spin structure of the nucleon. I also report on some Monte Carlo simulations of such asymmetries for the production of Drell-Yan lepton pairs from the collision of high-energy pions on a transversely polarized proton target.
While much attention has been focussed on the successes of perturbative QCD in describing the $Q^2$-dependence of deep-inelastic structure functions, the starting distributions themselves contain important, non-perturbative information on the structure of the nucleon, which has been somewhat neglected. We review some of the most important, recent discoveries resulting from studies of deep-inelastic scattering. There are important connections between these discoveries and low energy properties of the nucleon and wherever possible we shall make these clear. In particular, we shall see that well …
Chiral symmetry aspects for baryon properties are studied. After a brief discussion on general framework, we introduce two distinctive chiral group representations for baryons: the naive and mirror assignments. Using linear sigma models, nucleon properties are studied in both representations. Finally, we propose an experiment to distinguish the two assignments in the reactions of pion and eta productions.
Using the vacuum-to-pion matrix element of the correlation function of the interpolating fields of the two nucleons, the isospin splitting in the diagonal pion-nucleon coupling constant has been studied in the framework of the conventional QCD sum rule. Some of the implications of this splitting has also been discussed.
LOW ENERGY NUCLEON-NUCLEON SCATTERING IN THE SKYRME MODEL
本文研究了Skyrme拉格朗日量的动能对低能核子散射的主导贡献。这个经典的2体系统的动能计算使用的产品anxion和正确的低能量，分离Skyrmions。我们计算了Skyrmions的转动自由度，以便给它们正确的自旋和同位旋值。然后，我们能够计算一些角动量偏振的散射角解析。
Precise knowledge of the strange and antistrange quark distributions of the nucleon is a major step toward better understanding of the strong interaction and the nucleon structure. Moreover, the $ s-\bar s $ asymmetry in the nucleon plays an important role in some physical processes involving hadrons. The goal of this paper is the study of intrinsic strange contribution to the strange sea of the nucleon. To this aim, we calculate the intrinsic strange distributions from the various light-cone models including BHPS, scalar five-quark and meson-baryon models and then compare their results. These…
We evaluate the charged current neutrino-nucleon total cross section up to neutrino energies of 10^{12} GeV in the LO and NLO of perturbative QCD within the framework of two different factorization schemes. The numerical implications of some inconsistent QCD calculations are illustrated.
This talk is a natural continuation of that given by V.Vereshagin at this conference. We discuss some details not covered in that talk and review the calculational technique using the (πN)-elastic scattering as an example. Finally, we briefly mention some results of numerical comparison with experimental data. More technical details can be found in the talk by K.Semenov-Tian-Shansky (this conference)devoted to the analysis of elastic KN scattering.
A linear correlation is found between the magnitude of nucleon-nucleon short-range correlations and the nuclear binding energy per nucleon with pairing energy removed. By using this relation, the strengths of nucleon-nucleon short-range correlations of some unmeasured nuclei are predicted. Discussions on nucleon-nucleon pairing energy and nucleon-nucleon short-range correlations are made. The found nuclear dependence of nucleon-nucleon short-range correlations may shed some lights on the short-range structure of nucleus.
Several aspects of hadron physics are well described by a simple 5D effective field theory. Baryons arise in this scenario as "large" (and therefore calculable) 5D skyrmions. We extend and refine the existing analysis of this 5D soliton, which is fairly non-trivial due to the need of numerical methods. We perform the complete quantization of those collective coordinates which are relevant for computing the static observables like the nucleon form factors. We compare the result with simple expectations about large-N_c QCD and with the experimental data. An agreement within 30% is found.
The interaction of Nucleon-Nucleon (NN) has certain physical characteristics, which indicated by nucleon, and meson degrees of freedom. The main purpose of this work is calculating the ground state energies of 21 Deutron and Alfa through the two-body system with the exchange of mesons (Pi, segma, omega) that mediated between two nucleons. This paper investigates NN interaction based on the quasi-relativistic decoupled Dirac equation and self-consistent Hartree-Fock formulation. We construct one-boson exchange potential (OBEP) model, where each nucleon is treated as a Dirac particle and acts as…
These lectures give an introduction to baryon chiral perturbation theory. I show in detail how to construct the chiral effective pion-nucleon Lagrangian in the one loop approximation. Particular emphasis is put on the physics related to electromagnetic probes, as manifest in pion photo- and electroproduction, Compton scattering off nucleons and the electroweak form factors of the nucleon. Other topics discussed in some detail are the meaning of low-energy theorems, pion-nucleon scattering, the reaction $πN \to ππN$ and isospin violation in the pion-nucleon system. The chiral predictions are co…
A crucial input for recent meson hyperon cloud model estimates of the nucleon matrix element of the strangeness current are the nucleon-hyperon-K* (NYK*) form factors which regularize some of the arising loops. Prompted by new and forthcoming information on these form factors from hyperon-nucleon potential models, we analyze the dependence of the loop model results for the strange-quark observables on the NYK* form factors and couplings. We find, in particular, that the now generally favored soft N-Lambda-K* form factors can reduce the magnitude of the K* contributions in such models by more t…
We review the current status of Parton Distribution Function (PDF) determinations for unpolarized and longitudinally polarized protons and for unpolarized nuclei, which are probed by high-energy hadronic scattering in perturbative Quantum Chromodynamics (QCD). We present the established theoretical framework, the experimental information, and the methodological aspects inherent to any modern PDF extraction. Furthermore, we summarize the present knowledge of PDFs and discuss their limitations in both accuracy and precision relevant to advance our understanding of QCD proton substructure and pur…
We carefully examine all the four derivations of the renormalization group equation (RGE) for the so-called $\Vlk$ potential, given by Bogner, \textit{et. al.}[nucl-th/0111042]. Two derivations based on the ``semi-group composition law'' are shown to be unjustified, while the other two based on the completeness relation of the model space must be modified if there are bound states. It is however shown that the RGE is unchanged if the bound state wavefunctions in the reduced theory are required to have the same low-momentum components as those in the original theory. Several aspects of the $\Vl…
Some Aspects of Nuclear Deep Inelastic Scattering
在电流算符显式满足庞加莱不变性和电流守恒的模型框架下，研究了核的深度非弹性散射。在Bjorken变量$x$较小的情况下，结果与标准结果有很大的不同。特别是，在x<0.01的情况下，从氘核数据中提取中子结构函数是不可能的，我们预测，在低x和大动量转移的情况下，氘核结构函数的行为与核子结构函数的行为有很大的不同。我们还认为，对于较重的核的末态相互作用的影响是重要的，即使在比约肯极限。
I discuss low-energy pion-nucleon scattering in the framework of chiral perturbation theory. I argue that using this theoretical method one is able to handle the in some cases tremendous experimental accuracy (for the low partial waves). I then show how strong and electromagnetic isospin violation can be treated simultaneously. Some first results for neutral pion scattering and the $σ$-term are given.
This review gives a brief introduction to the chiral effective field theory of nuclear forces and atomic nuclei. We discuss the status of the nuclear Hamiltonian derived in this framework and some recent applications in few-nucleon systems. Nuclear lattice simulations as a new tool to address the many-body problem are introduced and some first results based on that method are presented.
We briefly review the key aspect of the QCD instanton vacuum in relation to the quantum breaking of conformal symmetry and the trace anomaly. We use Ji$^\prime s$ invariant mass decomposition of the energy momentum tensor together with the trace anomaly, to discuss the mass budget of the nucleon and pion in the QCD instanton vacuum. A measure of the gluon condensate in the nucleon, is a measure of the compressibility of the QCD instanton vacuum as a dilute topological liquid.
Considering the magnetic moment and polarizabilities of the nucleon we emphasize the need for relativistic chiral EFT calculations. Our relativistic calculations are done via the forward-Compton-scattering sum rules, thus ensuring the correct analytic properties. The results obtained in this way are equivalent to the usual loop calculations, provided no heavy-baryon expansion or any other manipulations which lead to a different analytic structure (e.g., infrared regularization) are made. The Baldin sum rule can directly be applied to calculate the sum of nucleon polarizabilities. In contrast, …
On the basis of the non-perturbative Heisenberg's quantization scheme and using some simplifications and assumptions the reduction from the gluon-quark Lagrangian to a scalar-fermion Lagrangian is made. The corresponding field equations have a regular spherically symmetric solution which can be interpret as a simplified model of nucleon. Some properties of such "nucleon" are discused: the presence of a mass gap and spin $\neq \hbar /2$. The mass gap describes the difference between the "nucleon" and the "nucleon" without quark field (a scalar glueball). The presence of spin $\neq \hbar /2$ can…
The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its {\it intrinsic} quadrupole moment which is first order moment of the charge density operator. With some experimental indications of a deformed nucleon, we have calculated the {\it intrinsic} quadrupole moment of the octet and decuplet baryons in the framework of chiral constituent quark model \chiCQM which is quite successful in explaining some of the important baryon properties in the nonperturbative regime.
We review some results obtained by the Coimbra-Ljubljana collaboration that reveal the important role of the pion cloud in the low- and intermediate-energy nucleon and delta resonances.
We present the results on non-perturbative quantum gravity effects related to extra dimensions which can be comparable, in some cases, with the SM contributions, e.g. in lepton-lepton or lepton-nucleon scattering. The case of cosmic neutrino gravitational interaction with atmospheric nucleons is considered in detail.
I review aspects of chiral dynamics pertinent to the structure of baryons and few-nucleon systems, such as chiral extrapolations for the nucleon and the delta mass, double pion photoproduction off protons, single neutral pion electroproduction off the deuteron, pion photoproduction in the delta region, the quark mass dependence of the nuclear forces and the possibility of an infrared limit cycle in QCD.
We discuss some problems with the large Nc approximation for nucleons which arise if the axial coupling of the nucleon to pions is large, g_A \sim Nc. While g_A \sim Nc in non-relativistic quark and Skyrme models, it has been suggested that Skyrmions may collapse to a small size, r \sim 1/f_pi \sim Lambda_QCD^{-1}/sqrt(Nc). (This is also the typical scale over which the string vertex moves in a string vertex model of the baryon.) We concentrate on the case of two flavors, where we suggest that to construct a nucleon with a small axial coupling, that most quarks are bound into colored diquark p…
We present a first exploratory study for hyperon-nucleon interactions using renormalization group techniques. The effective two-body low-momentum potential V_low-k is obtained by integrating out the high-momentum components from realistic Nijmegen YN potentials. A T-matrix equivalence approach is employed, so that the low-energy phase shifts are reproduced by V_low-k up to a momentum scale Lambda ~ 500 MeV. Although the various bare Nijmegen models differ somewhat from each other, the corresponding V_low-k interactions show convergence in some channels, suggesting a possible unique YN interact…
A review is presented of the antinucleon-nucleon interaction, and some related issues such as fundamental symmetries, annihilation mechanisms, antinucleon-nucleus scattering, antiprotonic atoms and neutron-antineutron oscillations. The overall perspective is historical but the modern approaches are also presented.
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