The relativistic mean-field approach was implemented in the Lanzhou quantum molecular dynamics transport model(LQMD.RMF). Using the LQMD.RMF, the properties of collective flow and pion production were investigated sys...The relativistic mean-field approach was implemented in the Lanzhou quantum molecular dynamics transport model(LQMD.RMF). Using the LQMD.RMF, the properties of collective flow and pion production were investigated systematically for nuclear reactions with various isospin asymmetries. The directed and elliptic flows of the LQMD.RMF are able to describe the experimental data of STAR Collaboration. The directed flow difference between free neutrons and protons was associated with the stiffness of the symmetry energy, that is, a softer symmetry energy led to a larger flow difference. For various collision energies, the ratio between the π^(-) and π^(+) yields increased with a decrease in the slope parameter of the symmetry energy. When the collision energy was 270 MeV/nucleon, the single ratio of the pion transverse momentum spectra also increased with decreasing slope parameter of the symmetry energy in both nearly symmetric and neutron-rich systems.However, it is difficult to constrain the stiffness of the symmetry energy with the double ratio because of the lack of threshold energy correction on the pion production.展开更多
We investigate a neutral pion electromagnetic form factor in momentum space and obtain Gaussian-like function for it. The characteristic form of our neutral pion electromagnetic form factor is consistent with the resu...We investigate a neutral pion electromagnetic form factor in momentum space and obtain Gaussian-like function for it. The characteristic form of our neutral pion electromagnetic form factor is consistent with the results published by Jefferson Lab Hall A Collaboration. .展开更多
In previous articles (Guido) we demonstrated that Quarks (u, d) are represented by golden geometric structures of coupled quantum oscillators. In this article we show the geometric structure of the pion triplet and, i...In previous articles (Guido) we demonstrated that Quarks (u, d) are represented by golden geometric structures of coupled quantum oscillators. In this article we show the geometric structure of the pion triplet and, in particular, via the structure equation of neutral pion, we identify its decays and we solve the spin question in hadrons thanks also to introduction of algebraic operations [?, ⊕] on geometric structure. Moreover by means of the golden ratio between (u, d), we determine the values of bare masses of quarks (3.51 MeV for u-quark and 5.67 MeV for d-quark) and those ones bounded in a pion (53.31 MeV for u-quark and 85.26 MeV for d-quark). Finally, using algebraic operations [?, ⊕] we point out a new way to represent the processes of pions’ decay.展开更多
A new fit of the pion parton distribution functions is provided. Only valence quark distributions are used at a low evolution scale and are evolved with the modified Dokshitzer- Gribov-Lipatov-Altarelli-Parisi equatio...A new fit of the pion parton distribution functions is provided. Only valence quark distributions are used at a low evolution scale and are evolved with the modified Dokshitzer- Gribov-Lipatov-Altarelli-Parisi equation which is briefly introduced in this work, and the sea quark and gluon distributions are only generated by the quantum chromodynamics processes. We find that the patton distributions can explain the pion-nucleon experiments data well, and it can also be compared with the data from the leading neutron data of experiments at HERA. The momentum distributions among the partons are discussed and our results are consistent with some models.展开更多
Pion cloud effects on △-N mass splitting are studied based on quark models. Pseudo-scalar pion-quarkcoupling is discussed in the relativistic and nonrelativistic frameworks. We separately calculate the pion cloud eff...Pion cloud effects on △-N mass splitting are studied based on quark models. Pseudo-scalar pion-quarkcoupling is discussed in the relativistic and nonrelativistic frameworks. We separately calculate the pion cloud effects bythe one-pion exchange potential and by another method which is consistent with the baryon chiral perturbation theory.Remark able discrepancy in the mass splitting between the two methods is shown.展开更多
The nucleonic ~1S_0 superfluidity is investigated by solving the gap equation for the Reid soft-core potential as the nucleon-nucleon interaction in neutron star(NS) matter which is considered to be made up of p, e, ...The nucleonic ~1S_0 superfluidity is investigated by solving the gap equation for the Reid soft-core potential as the nucleon-nucleon interaction in neutron star(NS) matter which is considered to be made up of p, e, μ and condensed antikaon matter. We mainly study the influence of the soft pion-induced potential on the nucleonic^1S_0 pairing gaps in the above NS matter. It is found that the intensities of the nucleonic ~1S_0 pairing gaps including the soft pion-induced potential are smaller than those calculated in the case of not including the soft pion-induced potential. Furthermore, the nucleonic ~1S_0 pairing gaps with the soft pion-induced potential fall into decline with the deepening of the optical potential of antikaons in the above NS matter, whereas they increase with the parameter η for the fixed optical potential of antikaons. Due to the appearance of the soft pion-induced potential, the maximum values of nucleonic ~1S_0 pairing gaps at parameter η = 0.20,0.55 are suppressed by1.7%-6.8% with respect to the case without soft pion-induced potential in the above NS matter.展开更多
We study the asymmetric nuclear matter in a nonperturvative manner at finite temperatures using thermofield dynamics method. The nucleon-meson interaction is taken to examine the binding energy (EB), pressure (P) for ...We study the asymmetric nuclear matter in a nonperturvative manner at finite temperatures using thermofield dynamics method. The nucleon-meson interaction is taken to examine the binding energy (EB), pressure (P) for various proton fractions.展开更多
The space-time characters of the pion-emitting sources produced in the heavy ion collisions at the Large Hadron Collider (LHC) energies are investigated in a granular source model of quark-gluon plasma droplets. The...The space-time characters of the pion-emitting sources produced in the heavy ion collisions at the Large Hadron Collider (LHC) energies are investigated in a granular source model of quark-gluon plasma droplets. The results of two-pion interferometry indicate that the longi- tudinal interferometry radius is sensitive to the initial breakup time of the system. For a larger breakup time the values of the longitudinal interferometry radius for the LHC source are larger than that of the source produced in the collisions at the Relativistic Heavy Ion Collider's (RHIC) top energy. However, the values of the longitudinal radius are smaller if the source fragments at a smaller breakup time with a higher initial temperature of the droplets. The values of the transverse interferometry radius in the "side" direction for the LHC sources are larger than those for the RHIC source. The imaging analyses for the characteristic quantities of the granular sources are consistent with the interferometry radii.展开更多
A formula is derived for the central nucleon-nucleon potential, based on an analysis of the physical origin of the nucleon-nucleon attraction by pion exchange. The decrease of the dynamical mass of the interaction fie...A formula is derived for the central nucleon-nucleon potential, based on an analysis of the physical origin of the nucleon-nucleon attraction by pion exchange. The decrease of the dynamical mass of the interaction field, exchanged pion in this case, is the principal mechanism responsible for the nuclear attraction in a similar way that the decrease of the kinetic energy of the exchange electron in the diatomic molecule is directly responsible for the covalent molecular attraction. The minimum value of this central nucleon-nucleon potential and the position of the minimum are similar with the values reported in literature for a potential calculated by lattice QCD, which shares the features of the phenomenological nucleon-nucleon potentials. The Schrodinger equation with this central nucleon-nucleon potential was solved numerically for different values of the pion mass. The binding energy increases with the decrease of the pion mass. For masses higher than the real pion mass the nucleon-nucleon system is unbound. We discuss on the two pion exchange and hard core repulsion. The minimum value of the potential for two pion exchange is comparable with the minimum value of the CD Bonn potential. For a hard core radius of 0.5 fm the binding energy is equal to the deuteron binding energy.展开更多
We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a patton-jet nuclear modification factor at RHIC and LHC, and contrast the predictions based on a linear pQCD and a...We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a patton-jet nuclear modification factor at RHIC and LHC, and contrast the predictions based on a linear pQCD and a highly non-linear hybrid AdS holographic model of jet-energy loss. It is found that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In the case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extracted data can be characterized without a reduced jet-medium coupling at LHC energies. It is concluded that when the reconstructed jets are sensitive to both quarks and gluons and thus provide more information than the pion nuclear modification factor, their information regarding the jet-medium coupling is limited due to the superposition with NLO and medium effects. Hence, a detailed description of the underlying physics requires both the leading hadron and the reconstructed jet nuclear modification factor. Unfortunately, the results for both the pion and the parton-jet nuclear modification factor are insensitive to the jet-path dependence of the models considered.展开更多
The disappearance searching experiments ?use charged current quasielastic (CCQE) reaction to detect an arriving neutrino and reconstruct its energy, while the CC1π+ production can mimic the CCQE signal process. In ?a...The disappearance searching experiments ?use charged current quasielastic (CCQE) reaction to detect an arriving neutrino and reconstruct its energy, while the CC1π+ production can mimic the CCQE signal process. In ?appearance experiments, the NC1π0 production process can lead to a fake e-?event by the impossibility for the detector of distinguish an arriving electron or a photon. Here we present a consistent model, from the point of view of the construction of the elemental amplitude, for the mentioned pion production background processes including bounding, smearing and final state interaction (FSI) effects in a single fashion. Results are comparable with more evolved approaches based on Monte Carlo simulations.展开更多
The present article is a continuation of a recently published paper [1] in which we have modeled the composition and structure of neutrons and other hadrons using the Rotating Lepton Model (RLM) which is a Bohr type m...The present article is a continuation of a recently published paper [1] in which we have modeled the composition and structure of neutrons and other hadrons using the Rotating Lepton Model (RLM) which is a Bohr type model employing the relativistic gravitational attraction between three ultrafast rotating neutrinos as the centripetal force. The RLM accounts for special relativity and also for the De Broglie equation of quantum mechanics. In this way this force was shown to reach the value of the Strong Force while the values of the masses of the rotating relativistic neutrinos reach those of quarks. Masses computed for twelve hadrons and bosons are in very close (~2%) agreement with the experimental values. Here we use the same RLM approach to describe the composition and structure and to compute the masses of Pions and Kaons which are important zero spin mesons. Contrary to hadrons and bosons which have been found via the RLM to comprise the heaviest neutrino eigenmass m<sub>3</sub>, in the case of mesons the intermediate neutrino mass eigenstate m<sub>2</sub> is found to play the dominant role. This can explain why the lowest masses of mesons are generally smaller than those of hadrons and bosons. Thus in the case of Pions it is found that they comprise three rotating m<sub>2</sub> mass eigenstate neutrinos and the computed mass of 136.6 MeV/c<sup>2</sup> is in good agreement with the experimental value of 134.977 MeV/c<sup>2</sup>. The Kaon structure is found to consist of six m<sub>2</sub> mass eigenstate neutrinos arranged in two parallel pion-type rotating triads. The computed Kaon mass differs less that 2% from the experimental K<sup>±</sup> and K°values of 493.677 MeV/c<sup>2</sup> and 497.648 MeV/c<sup>2</sup> respectively. This, in conjunction with the experimentally observed decay products of the Kaons, provides strong support for the proposed K structure.展开更多
Taking into account the effects of shadowing and jet quenching, the large transverse momentum distribution of K+, π+ and K+/π+ ratios at s = 200 GeV originating from resolved photoproduction processes is calcula...Taking into account the effects of shadowing and jet quenching, the large transverse momentum distribution of K+, π+ and K+/π+ ratios at s = 200 GeV originating from resolved photoproduction processes is calculated based on perturbative quantum chromodynamics. It is found that the contribution of K+ and π+ produced by photoproduction processes is evident. The K+ /π+ ratios in Au-Au collisions show an obvious enhancement compared with p p collisions. The numerical results indicate that the photoproduetion processes are good modification for kaon and pion production.展开更多
基金This study was supported by the National Natural Science Foundation ofChina(Nos.12147106,12175072,and 11722546)the Talent Programof South China University of Technology(No.20210115).
文摘The relativistic mean-field approach was implemented in the Lanzhou quantum molecular dynamics transport model(LQMD.RMF). Using the LQMD.RMF, the properties of collective flow and pion production were investigated systematically for nuclear reactions with various isospin asymmetries. The directed and elliptic flows of the LQMD.RMF are able to describe the experimental data of STAR Collaboration. The directed flow difference between free neutrons and protons was associated with the stiffness of the symmetry energy, that is, a softer symmetry energy led to a larger flow difference. For various collision energies, the ratio between the π^(-) and π^(+) yields increased with a decrease in the slope parameter of the symmetry energy. When the collision energy was 270 MeV/nucleon, the single ratio of the pion transverse momentum spectra also increased with decreasing slope parameter of the symmetry energy in both nearly symmetric and neutron-rich systems.However, it is difficult to constrain the stiffness of the symmetry energy with the double ratio because of the lack of threshold energy correction on the pion production.
文摘We investigate a neutral pion electromagnetic form factor in momentum space and obtain Gaussian-like function for it. The characteristic form of our neutral pion electromagnetic form factor is consistent with the results published by Jefferson Lab Hall A Collaboration. .
文摘In previous articles (Guido) we demonstrated that Quarks (u, d) are represented by golden geometric structures of coupled quantum oscillators. In this article we show the geometric structure of the pion triplet and, in particular, via the structure equation of neutral pion, we identify its decays and we solve the spin question in hadrons thanks also to introduction of algebraic operations [?, ⊕] on geometric structure. Moreover by means of the golden ratio between (u, d), we determine the values of bare masses of quarks (3.51 MeV for u-quark and 5.67 MeV for d-quark) and those ones bounded in a pion (53.31 MeV for u-quark and 85.26 MeV for d-quark). Finally, using algebraic operations [?, ⊕] we point out a new way to represent the processes of pions’ decay.
文摘A new fit of the pion parton distribution functions is provided. Only valence quark distributions are used at a low evolution scale and are evolved with the modified Dokshitzer- Gribov-Lipatov-Altarelli-Parisi equation which is briefly introduced in this work, and the sea quark and gluon distributions are only generated by the quantum chromodynamics processes. We find that the patton distributions can explain the pion-nucleon experiments data well, and it can also be compared with the data from the leading neutron data of experiments at HERA. The momentum distributions among the partons are discussed and our results are consistent with some models.
文摘Pion cloud effects on △-N mass splitting are studied based on quark models. Pseudo-scalar pion-quarkcoupling is discussed in the relativistic and nonrelativistic frameworks. We separately calculate the pion cloud effects bythe one-pion exchange potential and by another method which is consistent with the baryon chiral perturbation theory.Remark able discrepancy in the mass splitting between the two methods is shown.
基金Supported by the Open Foundation of Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processingthe Youth Innovation Promotion Association of the Chinese Academy of Sciences under Grant No 2016056+1 种基金the Development Project of Science and Technology of Jilin Province under Grant No 20180520077JHthe National Natural Science Foundation of China under Grant Nos 11805022 and 11803057
文摘The nucleonic ~1S_0 superfluidity is investigated by solving the gap equation for the Reid soft-core potential as the nucleon-nucleon interaction in neutron star(NS) matter which is considered to be made up of p, e, μ and condensed antikaon matter. We mainly study the influence of the soft pion-induced potential on the nucleonic^1S_0 pairing gaps in the above NS matter. It is found that the intensities of the nucleonic ~1S_0 pairing gaps including the soft pion-induced potential are smaller than those calculated in the case of not including the soft pion-induced potential. Furthermore, the nucleonic ~1S_0 pairing gaps with the soft pion-induced potential fall into decline with the deepening of the optical potential of antikaons in the above NS matter, whereas they increase with the parameter η for the fixed optical potential of antikaons. Due to the appearance of the soft pion-induced potential, the maximum values of nucleonic ~1S_0 pairing gaps at parameter η = 0.20,0.55 are suppressed by1.7%-6.8% with respect to the case without soft pion-induced potential in the above NS matter.
文摘We study the asymmetric nuclear matter in a nonperturvative manner at finite temperatures using thermofield dynamics method. The nucleon-meson interaction is taken to examine the binding energy (EB), pressure (P) for various proton fractions.
基金supported by National Natural Science Foundation of China (Nos. 10775024, 11075027)
文摘The space-time characters of the pion-emitting sources produced in the heavy ion collisions at the Large Hadron Collider (LHC) energies are investigated in a granular source model of quark-gluon plasma droplets. The results of two-pion interferometry indicate that the longi- tudinal interferometry radius is sensitive to the initial breakup time of the system. For a larger breakup time the values of the longitudinal interferometry radius for the LHC source are larger than that of the source produced in the collisions at the Relativistic Heavy Ion Collider's (RHIC) top energy. However, the values of the longitudinal radius are smaller if the source fragments at a smaller breakup time with a higher initial temperature of the droplets. The values of the transverse interferometry radius in the "side" direction for the LHC sources are larger than those for the RHIC source. The imaging analyses for the characteristic quantities of the granular sources are consistent with the interferometry radii.
文摘A formula is derived for the central nucleon-nucleon potential, based on an analysis of the physical origin of the nucleon-nucleon attraction by pion exchange. The decrease of the dynamical mass of the interaction field, exchanged pion in this case, is the principal mechanism responsible for the nuclear attraction in a similar way that the decrease of the kinetic energy of the exchange electron in the diatomic molecule is directly responsible for the covalent molecular attraction. The minimum value of this central nucleon-nucleon potential and the position of the minimum are similar with the values reported in literature for a potential calculated by lattice QCD, which shares the features of the phenomenological nucleon-nucleon potentials. The Schrodinger equation with this central nucleon-nucleon potential was solved numerically for different values of the pion mass. The binding energy increases with the decrease of the pion mass. For masses higher than the real pion mass the nucleon-nucleon system is unbound. We discuss on the two pion exchange and hard core repulsion. The minimum value of the potential for two pion exchange is comparable with the minimum value of the CD Bonn potential. For a hard core radius of 0.5 fm the binding energy is equal to the deuteron binding energy.
基金Supported by the Helmholtz International Centre for FAIR within the Framework of the LOEWE Programthe US-DOE Nuclear Science under Grant Nos DE-FG02-93ER40764 and DE-AC02-05CH11231
文摘We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a patton-jet nuclear modification factor at RHIC and LHC, and contrast the predictions based on a linear pQCD and a highly non-linear hybrid AdS holographic model of jet-energy loss. It is found that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In the case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extracted data can be characterized without a reduced jet-medium coupling at LHC energies. It is concluded that when the reconstructed jets are sensitive to both quarks and gluons and thus provide more information than the pion nuclear modification factor, their information regarding the jet-medium coupling is limited due to the superposition with NLO and medium effects. Hence, a detailed description of the underlying physics requires both the leading hadron and the reconstructed jet nuclear modification factor. Unfortunately, the results for both the pion and the parton-jet nuclear modification factor are insensitive to the jet-path dependence of the models considered.
文摘The disappearance searching experiments ?use charged current quasielastic (CCQE) reaction to detect an arriving neutrino and reconstruct its energy, while the CC1π+ production can mimic the CCQE signal process. In ?appearance experiments, the NC1π0 production process can lead to a fake e-?event by the impossibility for the detector of distinguish an arriving electron or a photon. Here we present a consistent model, from the point of view of the construction of the elemental amplitude, for the mentioned pion production background processes including bounding, smearing and final state interaction (FSI) effects in a single fashion. Results are comparable with more evolved approaches based on Monte Carlo simulations.
文摘The present article is a continuation of a recently published paper [1] in which we have modeled the composition and structure of neutrons and other hadrons using the Rotating Lepton Model (RLM) which is a Bohr type model employing the relativistic gravitational attraction between three ultrafast rotating neutrinos as the centripetal force. The RLM accounts for special relativity and also for the De Broglie equation of quantum mechanics. In this way this force was shown to reach the value of the Strong Force while the values of the masses of the rotating relativistic neutrinos reach those of quarks. Masses computed for twelve hadrons and bosons are in very close (~2%) agreement with the experimental values. Here we use the same RLM approach to describe the composition and structure and to compute the masses of Pions and Kaons which are important zero spin mesons. Contrary to hadrons and bosons which have been found via the RLM to comprise the heaviest neutrino eigenmass m<sub>3</sub>, in the case of mesons the intermediate neutrino mass eigenstate m<sub>2</sub> is found to play the dominant role. This can explain why the lowest masses of mesons are generally smaller than those of hadrons and bosons. Thus in the case of Pions it is found that they comprise three rotating m<sub>2</sub> mass eigenstate neutrinos and the computed mass of 136.6 MeV/c<sup>2</sup> is in good agreement with the experimental value of 134.977 MeV/c<sup>2</sup>. The Kaon structure is found to consist of six m<sub>2</sub> mass eigenstate neutrinos arranged in two parallel pion-type rotating triads. The computed Kaon mass differs less that 2% from the experimental K<sup>±</sup> and K°values of 493.677 MeV/c<sup>2</sup> and 497.648 MeV/c<sup>2</sup> respectively. This, in conjunction with the experimentally observed decay products of the Kaons, provides strong support for the proposed K structure.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11065010 and 11465021
文摘Taking into account the effects of shadowing and jet quenching, the large transverse momentum distribution of K+, π+ and K+/π+ ratios at s = 200 GeV originating from resolved photoproduction processes is calculated based on perturbative quantum chromodynamics. It is found that the contribution of K+ and π+ produced by photoproduction processes is evident. The K+ /π+ ratios in Au-Au collisions show an obvious enhancement compared with p p collisions. The numerical results indicate that the photoproduetion processes are good modification for kaon and pion production.