Using a symmetry-preserving treatment of a vector <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>×</mo></math> vector contact interaction at nonzero temperature, we compute the screening masses of flavor-SU(3) ground-state <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>J</mi><mi>P</mi></msup><mo>=</mo><msup><mn>0</mn><mo>±</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>1</mn><mo>±</mo></msup></math> mesons, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>J</mi><mi>P</mi></msup><mo>=</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>±</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>±</mo></msup></math> baryons. We find that all correlation channels allowed at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mo>=</mo><mn>0</mn></math> persist when the temperature increases, even above the QCD phase transition temperature. The results for mesons qualitatively agree with those obtained from the contemporary lattice-regularized quantum chromodynamics simulations. One of the most remarkable features is that each parity-partner-pair degenerates when <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mo>&gt;</mo><msub><mi>T</mi><mi>c</mi></msub></math>, with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mi>c</mi></msub></math> being the critical temperature. For each pair, the screening mass of the negative parity meson increases monotonously with temperature. In contrast, the screening mass of the meson with positive parity is almost invariant on the domain <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mo>≲</mo><msub><mi>T</mi><mi>c</mi></msub><mo>/</mo><mn>2</mn></math>; when <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math> gets close to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mi>c</mi></msub></math>, it decreases but soon increases again and finally degenerates with its parity partner, which signals the restoration of chiral symmetry. We also find that the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math>-dependent behaviors of baryon screening masses are quite similar to those of the mesons. For baryons, the dynamical, nonpointlike diquark correlations play a crucial role in the screening mass evolution. We further calculate the evolution of the fraction of each kind of diquark within baryons respective to temperature. We observe that, at high temperatures, only <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>=</mo><mn>0</mn></math> scalar and pseudoscalar diquark correlations can survive within <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>J</mi><mi>P</mi></msup><mo>=</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>±</mo></msup></math> baryons.

China

Chen Chen

Fei Gao

Si-xue Qin

Screening masses of positive- and negative-parity hadron ground states, including those with strangeness

We report a lattice QCD calculation of the parton distribution function (PDF) of a deuteronlike dibaryon system using large-momentum effective theory. The calculation is done on three Wilson-clover ensembles with a fixed lattice spacing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>a</mi><mo>=</mo><mn>0.105</mn><mtext> </mtext><mtext> </mtext><mi>fm</mi></mrow></math> and two pion masses. The lattice matrix elements are computed at proton momenta up to 2.46 GeV, with the signal of high-momentum modes being improved by applying the momentum smearing technique. The state-of-the-art renormalization, matching, and extrapolation are then applied to obtain the final result of the light-cone PDF. A comparison between the result of the dibaryon system and the sum of the proton and neutron PDFs is also given.

Yiqi Geng

Liuming Liu

Peng Sun

Yi-Bo Yang

Fei Yao

Jian-Hui Zhang

Kuan Zhang

Parton distribution function of a deuteronlike dibaryon system from lattice QCD

Using available information from Drell-Yan data on pion and kaon structure functions, an approach is described which enables the development of pointwise profiles for all pion and kaon parton distribution functions (DFs) without reference to theories of hadron structure. The key steps are construction of structure-function-constrained probability-weighted ensembles of valence DF replicas and use of an evolution scheme for parton DFs that is all-orders exact. The DFs obtained express qualitatively sound features of light-meson structure, <italic>e.g</italic>., the effects of Higgs boson couplings into QCD and the size of heavy-quark momentum fractions in light hadrons. In order to improve the results, additional and more precise data on the <italic>u</italic>-quark-in-kaon, <math altimg='si1.svg'><msup><mrow><mi mathvariant='script'>u</mi></mrow><mrow><mi>K</mi></mrow></msup></math>, to <italic>u</italic>-quark-in-pion, <math altimg='si105.svg'><msup><mrow><mi mathvariant='script'>u</mi></mrow><mrow><mi>&#960;</mi></mrow></msup></math>, DF ratio would be necessary. Of greater value would be extraction of <math altimg='si1.svg'><msup><mrow><mi mathvariant='script'>u</mi></mrow><mrow><mi>K</mi></mrow></msup></math> alone, thereby avoiding inference from the ratio: currently, the data-based form of <math altimg='si1.svg'><msup><mrow><mi mathvariant='script'>u</mi></mrow><mrow><mi>K</mi></mrow></msup></math> is materially influenced by results for <math altimg='si105.svg'><msup><mrow><mi mathvariant='script'>u</mi></mrow><mrow><mi>&#960;</mi></mrow></msup></math>.

Spain

Zhen-Ni Xu

Italy

Daniele Binosi

Khépani Raya

Craig D. Roberts

France

José Rodríguez-Quintero

Kaon distribution functions from empirical information

The 12C+ 12C fusion reaction at deep subbarrier energies is important for understanding the carbon burning process in massive star and explosive binary systems. However, its reaction rates are very difficult to measure directly or evaluate by simple extrapolation due to the extremely small cross sections and complex resonance structures near the Gamow window. In this work, we use one of its exit channels, <italic>i.e.</italic> 23Na+ <italic>p</italic> to populate the excited states of the compound nucleus 24Mg via the conventional thick-target inverse kinematics method. By applying <italic>&#947;</italic>-charged particle coincidence, we have obtained excitation functions for the proton and <italic>&#945;</italic> emission channels, respectively, and derived the resonance parameters through a simultaneous multi-channel R-matrix analysis. It is clear that a series of discrete resonances exist in the most relevant excitation energy region of 24Mg. The astrophysical <italic>S</italic>-factor of the 12C+ 12C fusion reaction is evaluated by adopting a systematic reduced width for the entrance channel. In particular, branching ratios of the dominant four decay channels are estimated across the entire Gamow window of the 12C+ 12C fusion reactions. Significant fluctuations are shown that may have strong impacts on the final outcome of the carbon burning process.

Weike Nan

Youbao Wang

Jun Su

Yaode Sheng

United States

Richard James deBoer

Yuqiang Zhang

Luyang Song

Fuqiang Cao

Chao Dong

Yunju Li

Zhihong Li

Gang Lian

Wei Nan

Yangping Shen

Na Song

Shengquan Yan

Seng Zeng

Bing Guo

Weiping Liu

Determination of resonances in Gamow window for 12C+ 12C fusion reaction via thick-target inverse kinematics method

A symmetry-preserving approach to the calculation of baryon properties in relativistic quantum field theory is used to predict all form factors associated with nucleon-to-<math><mi>Δ</mi></math> axial and pseudoscalar transition currents, thereby unifying them with many additional properties of these and other baryons. The new parameter-free predictions can serve as credible benchmarks for use in analyzing existing and anticipated data from worldwide efforts focused on elucidation of <math><mi>ν</mi></math> properties.

Germany

Christian S. Fischer

Nucleon-to-<math><mi>Δ</mi></math> Axial and Pseudoscalar Transition Form Factors

Abstract The open N = 2 string theory is defined on the 4D space-time with the split signature (+, +, −, −). The string field theory action of the open N = 2 string theory is described by the 4D Wess–Zumino–Witten (WZW$_{4}$) model. The equation of motion of the WZW$_{4}$ model is the Yang equation, which is equivalent to the anti-self-dual Yang–Mills equation. In this paper, we study soliton-type classical solutions of the WZW$_{4}$ model in the split signature by calculating the action density of the WZW$_{4}$ model. We find that the action density of the one-soliton solutions is localized on a 3D hyperplane. This shows that there would be codimension-one-solitonic objects, or equivalently some kind of three-branes in the open N = 2 string theory. We also prove that, in the asymptotic region of the space-time, the action density of the n-soliton solutions is a “non-linear superposition” of n one-solitons. This suggests the existence of n intersecting three-branes in the N = 2 strings. Finally we make a reduction to a (1 + 2)D real space-time to calculate the energy densities of the soliton solutions. We can successfully evaluate the energy distribution for the two-soliton solutions and find that there is no singularity in the interacting region. This implies the existence of smooth intersecting codimension-one branes in the whole region. Soliton solutions in the Euclidean signature are also discussed.

Japan

Masashi Hamanaka

Shan-Chi Huang

Hiroaki Kanno

Solitons in open = 2 String Theory Kahler-Chen-Simons theory A tour through N=2 strings On soliton solutions of the anti-self-dual Yang-Mills equations from the perspective of integrable systems Soliton solutions in an integrable chiral model in 2+1 dimensions On the space-time monopole equation A review on tachyon condensation in open string field theories Soliton equations as dynamical systems on infinite dimensional Grassmann manifold

Using a Poincaré-covariant <math><mrow><mi>quark</mi><mo>+</mo><mi>diquark</mi></mrow></math> Faddeev equation, we provide structural information on the four lightest <math><mo>(</mo><mi>I</mi><mo>,</mo><msup><mi>J</mi><mi>P</mi></msup><mo>)</mo><mo>=</mo><mo>(</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mo>,</mo><msup><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>∓</mo></msup><mo>)</mo></math> baryon multiplets. These systems may contain five distinct types of diquarks; but in order to obtain reliable results, it is sufficient to retain only isoscalar-scalar and isovector-axialvector correlations, with the latter being especially important. Viewed with low resolution, the Faddeev equation description of these states bears some resemblance to the associated quark model pictures; namely, they form a set of states related via orbital angular momentum excitation: the negative parity states are primarily <math><mrow><mi>P</mi></mrow></math>-wave in character, whereas the positive parity states are <math><mi>D</mi></math> wave. However, a closer look reveals far greater structural complexity than is typical of quark model descriptions, with <math><mi>P</mi></math>, <math><mi>D</mi></math>, <math><mi>S</mi></math>, <math><mi>F</mi></math> waves and interferences between them all playing a large role in forming observables. Large momentum transfer resonance electroexcitation measurements can be used to test these predictions and may thereby provide insights into the nature of emergent hadron mass.

Langtian Liu

Wave functions of <math><mrow><mo>(</mo><mi>I</mi><mo>,</mo><msup><mrow><mi>J</mi></mrow><mrow><mi>P</mi></mrow></msup><mo>)</mo><mo>=</mo><mo>(</mo><mfrac><mrow><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac><mo>,</mo><msup><mrow><mfrac><mrow><mn>3</mn></mrow><mrow><mn>2</mn></mrow></mfrac></mrow><mrow><mo>∓</mo></mrow></msup><mo>)</mo></mrow></math> baryons

Octet baryon axial, induced pseudoscalar, and pseudoscalar form factors are computed using a symmetry-preserving treatment of a vector <math><mo>×</mo></math> vector contact interaction (SCI), thereby unifying them with an array of other baryon properties and analogous treatments of semileptonic decays of pseudoscalar mesons. The baryons are treated as quark-plus-interacting-diquark bound states, whose structure is obtained by solving a Poincaré-covariant Faddeev equation. The approach is marked by algebraic simplicity and involves no free parameters, and, since it is symmetry preserving, all consequences of partial conservation of the axial current are manifest. It is found that SCI results are consistent with only small violations of SU(3)-flavor symmetry, an outcome which may be understood as a dynamical consequence of emergent hadron mass. The spin-flavor structure of the Poincaré-covariant baryon wave functions is expressed in the presence of both flavor-antitriplet–scalar diquarks and flavor-sextet–axial-vector diquarks and plays a key role in determining all form factors. Considering neutral axial currents, SCI predictions for the flavor separation of octet baryon axial charges and, therefrom, values for the associated SU(3) singlet, triplet, and octet axial charges are obtained. The results indicate that, at the hadron scale <math><msub><mi>ζ</mi><mi>H</mi></msub></math>, valence degrees of freedom carry roughly 50% of an octet baryon’s total spin. Since there are no other degrees of freedom at <math><msub><mi>ζ</mi><mi>H</mi></msub></math>, the remainder may be associated with <math><mrow><mi>quark</mi><mo>+</mo><mi>diquark</mi></mrow></math> orbital angular momentum.

Peng Cheng

Colombia

Brazil

Fernando E. Serna

Zhao-Qian Yao

Zhu-Fang Cui

Contact interaction analysis of octet baryon axial-vector and pseudoscalar form factors

A Poincaré-covariant <math><mrow><mi>quark</mi><mo>+</mo><mi>diquark</mi></mrow></math> Faddeev equation is used to develop insights into the structure of the four lightest <math><mo>(</mo><mi>I</mi><mo>,</mo><msup><mi>J</mi><mi>P</mi></msup><mo>=</mo><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>,</mo><msup><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>±</mo></msup><mo>)</mo></math> baryon multiplets. While these systems can contain isovector-axialvector and isovector-vector diquarks, one may neglect the latter and still arrive at a reliable description. The <math><mo>(</mo><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>,</mo><msup><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>+</mo></msup><mo>)</mo></math> states are the simpler systems, with features that bear some resemblance to quark model pictures, e.g., their most prominent rest-frame orbital angular momentum component is <math><mi>S</mi></math>-wave and the <math><mrow><mi>Δ</mi><mo>(</mo><mn>1600</mn><mo>)</mo><msup><mrow><mfrac><mrow><mn>3</mn></mrow><mrow><mn>2</mn></mrow></mfrac></mrow><mrow><mo>+</mo></mrow></msup></mrow></math> may reasonably be viewed as a radial excitation of the <math><mi>Δ</mi><mo>(</mo><mn>1232</mn><mo>)</mo><msup><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>+</mo></msup></math>. The <math><mo>(</mo><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>,</mo><msup><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>−</mo></msup><mo>)</mo></math> states are more complex: the <math><mi>Δ</mi><mo>(</mo><mn>1940</mn><mo>)</mo><msup><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>−</mo></msup></math> expresses little of the character of a radial excitation of the <math><mi>Δ</mi><mo>(</mo><mn>1700</mn><mo>)</mo><msup><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>−</mo></msup></math>; and while the rest-frame wave function of the latter is predominantly <math><mi>P</mi></math>-wave, the leading piece in the <math><mi>Δ</mi><mo>(</mo><mn>1940</mn><mo>)</mo><msup><mfrac><mn>3</mn><mn>2</mn></mfrac><mo>−</mo></msup></math> wave function is <math><mi>S</mi></math>-wave, in conflict with quark model expectations. Experiments that can test these predictions, such as large momentum transfer resonance electroexcitation, may shed light on the nature of emergent hadron mass.

Ya Lu

Jorge Segovia

Composition of low-lying <math><mrow><mi>J</mi><mo>=</mo><msup><mrow><mfrac><mrow><mn>3</mn></mrow><mrow><mn>2</mn></mrow></mfrac></mrow><mrow><mo>±</mo></mrow></msup></mrow></math> <math><mrow><mi>Δ</mi></mrow></math>-baryons

We use a continuum <math><mrow><mi>quark</mi><mo>+</mo><mi>diquark</mi></mrow></math> approach to the nucleon bound-state problem in relativistic quantum field theory to deliver parameter-free predictions for the nucleon axial and induced pseudoscalar form factors, <math><msub><mi>G</mi><mi>A</mi></msub></math> and <math><msub><mi>G</mi><mi>P</mi></msub></math>, and unify them with the pseudoscalar form factor <math><msub><mi>G</mi><mn>5</mn></msub></math> or, equivalently, the pion-nucleon form factor <math><msub><mi>G</mi><mrow><mi>π</mi><mi>N</mi><mi>N</mi></mrow></msub></math>. We explain how partial conservation of the axial-vector current and the associated Goldberger-Treiman relation are satisfied once all necessary couplings of the external current to the building blocks of the nucleon are constructed consistently; in particular, we fully resolve the seagull couplings to the diquark-quark vertices associated with the axial-vector and pseudoscalar currents. Among the results we describe, the following are worth highlighting. A dipole form factor defined by an axial charge <math><msub><mi>g</mi><mi>A</mi></msub><mo>=</mo><msub><mi>G</mi><mi>A</mi></msub><mo>(</mo><mn>0</mn><mo>)</mo><mo>=</mo><mn>1.25</mn><mo>(</mo><mn>3</mn><mo>)</mo></math> and a mass scale <math><msub><mi>M</mi><mi>A</mi></msub><mo>=</mo><mn>1.23</mn><mo>(</mo><mn>3</mn><mo>)</mo><msub><mi>m</mi><mi>N</mi></msub></math>, where <math><msub><mi>m</mi><mi>N</mi></msub></math> is the nucleon mass, can accurately describe the pointwise behavior of <math><msub><mi>G</mi><mi>A</mi></msub></math>. Concerning <math><msub><mi>G</mi><mi>P</mi></msub></math>, we obtain the pseudoscalar charge <math><msubsup><mi>g</mi><mi>p</mi><mo>*</mo></msubsup><mo>=</mo><mn>8.80</mn><mo>(</mo><mn>23</mn><mo>)</mo></math>, and find that the pion pole dominance approach delivers a reliable estimate of the directly computed result. Our computed value of the pion-nucleon coupling constant, <math><msub><mi>g</mi><mrow><mi>π</mi><mi>N</mi><mi>N</mi></mrow></msub><mo>/</mo><msub><mi>m</mi><mi>N</mi></msub><mo>=</mo><mn>14.02</mn><mo>(</mo><mn>33</mn><mo>)</mo><mo>/</mo><mi>GeV</mi></math> is consistent with recent precision determinations.

Nucleon axial-vector and pseudoscalar form factors and PCAC relations