Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and ...Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and consistent treatment of nuclear forces as inputs of modern many-body calculations,among which the in-medium similarity renormalization group(IMSRG)and its variants play a vital role.On the other hand,signifcant eforts have been made to provide a unifed description of the structure,decay,and reactions of the nuclei as open quantum systems.While a fully comprehensive and microscopic model has yet to be realized,substantial progress over recent decades has enhanced our understanding of open quantum systems around the dripline,which are often characterized by exotic structures and decay modes.To study these interesting phenomena,Gamow coupled-channel(GCC)method,in which the open quantum nature of few-body valence nucleons coupled to a deformed core,has been developed.This review focuses on the developments of the advanced IMSRG and GCC and their applications to nuclear structure and reactions.展开更多
The in-medium quark condensate is studied with an equivalent-mass approach in which one does not need to make assumptions on the derivatives of model parameters with respect to the quark current mass.It is shown that ...The in-medium quark condensate is studied with an equivalent-mass approach in which one does not need to make assumptions on the derivatives of model parameters with respect to the quark current mass.It is shown that the condensate is generally a decreasing function of both the density and temperature with the decreasing speed depending on the confinement parameter.Specially,at given density,the condensate decreases on increasing temperature.The decreasing speed is comparatively small at lower temperature,and becomes very fast at higher temperature.展开更多
Based on the fully dressed confining quark propagator, the pion decay constant fπ, local quark vacuum condensate, and the masses of light quarks and in-medlum Goldstone bosons are investigated. The pion decay constan...Based on the fully dressed confining quark propagator, the pion decay constant fπ, local quark vacuum condensate, and the masses of light quarks and in-medlum Goldstone bosons are investigated. The pion decay constant fπ is predicted and compared with its value of experimental measurement. A great agreement is obtained. With the predicted fπ and values of Goldstone boson masses measured by experiments in free configuration the current masses of light quarks and the masses of in-medium Goldstone bosons are obtained.展开更多
Extraction of the in-medium properties of strange particles from heavy-ion collisions is very complicated, since he nuclear density varies in the evolution of nucleus-nucleus collisions. To avoid the uncertainties of ...Extraction of the in-medium properties of strange particles from heavy-ion collisions is very complicated, since he nuclear density varies in the evolution of nucleus-nucleus collisions. To avoid the uncertainties of the baryon ensities during the stage of strange particle production, one can investigate proton-nucleus collisions where the uclear density is definite around the saturation density. Dynamics of strange particles produced in the protoninduced uclear the reactions near the threshold energies has been investigated within the Lanzhou quantum olecular dynamics (LQMD) transport model. The in-medium modifications on particle production in densenuclear matter are considered through the corrections to the elementary cross sections via the effective mass and he mean-field potentials[1].展开更多
The in-medium NN→N△ cross sections and its differential cross sections in isospin asymmetric nuclear medium are investigated in the framework of the one-boson exchange model by including isovector mesons, i.e., δan...The in-medium NN→N△ cross sections and its differential cross sections in isospin asymmetric nuclear medium are investigated in the framework of the one-boson exchange model by including isovector mesons, i.e., δand p mesons. Our results show that the in-medium NN→N△ cross sections are suppressed when the density increases, and the differential cross sections become isotropic with an increase in the density around the △ threshold energy. The isospin splitting on the medium correction factor, R =σ_(NN→N△)~*/σ_(NN→N△)^(free) is observed for different channels of NN→N△, especially around the threshold energy for all the effective Lagrangian parameters. By analyzing the selected effective Lagrangian parameters, our results show that the larger effective mass is, the weaker medium correction R is.展开更多
Three typical Pauli blocking algorithms in quantum molecular dynamics type models are investigated in the nuclear matter,the nucleus,and heavy ion collisions.In nuclear matter,the blocking ratios obtained with the thr...Three typical Pauli blocking algorithms in quantum molecular dynamics type models are investigated in the nuclear matter,the nucleus,and heavy ion collisions.In nuclear matter,the blocking ratios obtained with the three algorithms are underestimated by 13%-25%compared to the corresponding analytical values.For a finite nucleus,spurious collisions occur around the surface of the nucleus owing to the defects of the Pauli blocking algorithms.In the simulations of heavy ion collisions,the uncertainty of stopping power arising from the different Pauli blocking algorithms is less than 5%.Furthermore,the in-medium effects of nucleon-nucleon(NN)cross sections on the nuclear stopping power are discussed.Our results show that the transport model calculations with free NN cross sections result in the stopping power decreasing with beam energy when the beam energy is less than 300 MeV/u.To increase or decrease the values of the stopping power,the transport model calculations need enhanced or suppressed model dependent in-medium NN cross sections that are expected to be smaller than the true in-medium NN cross sections.展开更多
This study examines the impact of the squeezing effect caused by the in-medium mass modification of particles on the three-dimensional Hanbury Brown-Twiss(HBT)radii.An analysis is conducted on how the squeezing effect...This study examines the impact of the squeezing effect caused by the in-medium mass modification of particles on the three-dimensional Hanbury Brown-Twiss(HBT)radii.An analysis is conducted on how the squeezing effect impacts the three-dimensional HBT radii of,ϕϕ,D^(0)D^(0)and K^(+)K^(+).The squeezing effect suppresses the impact of transverse flow on the transverse source distribution and broadens the space-time rapidity distribution of the particle-emitting source,leading to an increase in the HBT radii,particularly in the out and longitudinal directions.This phenomenon becomes more significant for higher transverse pair momentum,resulting in a non-monotonic decrease in the HBT radii with increasing transverse pair momentum.The impact of the squeezing effect on the HBT radii is more pronounced for D^(0)D^(0)than forϕϕ.Furthermore,this effect is also more significant for D^(0)D^(0)than forϕϕ.The findings presented in this paper could offer fresh perspectives on investigating the squeezing effect.展开更多
High multipole electromagnetic transitions are rare in nature.The highest-multipole transition observed in atomic nuclei is the electric hexacontatetrapole E6 transition from the T_(1/2)=2.54(2)-min J^(π)=1_(9/2)-iso...High multipole electromagnetic transitions are rare in nature.The highest-multipole transition observed in atomic nuclei is the electric hexacontatetrapole E6 transition from the T_(1/2)=2.54(2)-min J^(π)=1_(9/2)-isomer to the 7/2^(-)ground state in^(53)Fe with an angular momentum change of six units.In the present work,we performed ab initio calculations for this unique case by employing chiral effective field theory(EFT)forces.The in-medium similarity renormalization group is used to derive the valence-space effective Hamiltonian and multipolar transition operators.Bare nucleon charges were used in all the multipolar transition rate calculations,providing good agreement with the experimental data.The valence space takes the full fp shell.In^(53)Fe,the low-lying states were dominated by the 0f_(7/2)component.Two different versions of the chiral EFT two-plus three-nucleon interaction were used to test the dependence on the interaction used.We also tested the convergence of the transition rate calculations against the harmonic oscillator parameter hΩand basis truncations e_(max)and E_(3max)for twoand three-nucleon forces,respectively.展开更多
In this review article,we first briefty introduce the transport theory and quantum molecular dynamics model applied in the study of the heavy ion collisions from low to intermediate energies.The developments of improv...In this review article,we first briefty introduce the transport theory and quantum molecular dynamics model applied in the study of the heavy ion collisions from low to intermediate energies.The developments of improved quantum molecular dynamics model(ImQMD)and ultra-relativistic quantum molecular dynamics model(UrQMD),are reviewed.The reaction mechanism and phenomena related to the fusion,multinucleon transrer,fragmentation,collective flow and particle production are reviewed and discussed within the framework of the two models.The constraints on the isospin asymmetric muclear equation of state and in-medium nucleon nucleon cross sections by comparing the heavy ion collision data with transport models calculations in last decades are also discussed,and the uncertainties of these constraints are analyzed as well.Finally,we discuss the future direction of the development of the transport models for improving the understanding of the reaction mechanism,the descriptions of various observables,the constraint on the nuclear equation of state,as well as for the constraint on in-medium nucleon-nucleon cross sections.展开更多
The relativistic mean field(RMF)model has achieved great success in describing various nuclear phenomena.However,several serious defects are common.For instance,the pseudo-spin symmetry of high-l orbits is distinctly ...The relativistic mean field(RMF)model has achieved great success in describing various nuclear phenomena.However,several serious defects are common.For instance,the pseudo-spin symmetry of high-l orbits is distinctly violated in general,leading to spurious shell closures N Z 58 and 92.This leads to problems in describing structure properties,including shell structures,nuclear masses,etc.Guided by the pseudo-spin symmetry restoration[Geng et al.,Phys.Rev.C,100:051301(2019)],a new RMF Lagrangian DD-LZ1 is developed by considering the density-dependent meson-nucleon coupling strengths.With the newly obtained RMF Lagrangian DD-LZ1,satisfactory descriptions can be obtained for the bulk properties of nuclear matter and finite nuclei.In particular,significant improvements on describing the single-particle spectra are achieved by DD-LZ1.In particular,the spurious shell closures Z 58 and 92,commonly found in previous RMF calculations,are eliminated by the new effective interaction DD-LZ1,and consistently the pseudo-spin symmetry(PSS)around the Fermi levels is reasonably restored for both low-l and high-l orbits.Moreover,the description of nuclear masses is also notably improved by DD-LZ1,as compared to the other RMF Lagrangians.展开更多
We study the near-threshold pion-induced production ofφmesons off nuclei in the kinematical conditions of the HADES experiment,recently performed at GSI.The calculations have been performed within a collision model b...We study the near-threshold pion-induced production ofφmesons off nuclei in the kinematical conditions of the HADES experiment,recently performed at GSI.The calculations have been performed within a collision model based on the nuclear spectral function.The model accounts for both the primaryπ^-meson–protonπ^-p→φn and the secondary pion–nucleonπN→φNφproduction processes as well as the effects of the nuclearφand nucleon mean-field potentials.We find that the primary reaction channelπ^-p→φn dominates in theφproduction off 12C and^（184）W target nuclei in the HADES acceptance window at incident pion momentum of 1.7 Ge V/c.We calculate the momentum dependence of the absolute and relative（transparency ratio）φmeson yields from the above direct channel.The calculations have been performed for this initial pion momentum allowing for different options for theφN absorption cross sectionσ（φN ）and different scenarios for the in-medium mass shifts of theφmeson and secondary neutron,produced together withφin this channel.We demonstrate that the transparency ratio for theφmesons has,contrary to the absolute cross sections,an insignificant sensitivity to theφmeson and secondary neutron in-medium mass shifts atφmomenta studied in the HADES experiment.On the other hand,we show that there are measurable changes in the transparency ratio due to theφN absorption cross section,which means that such a relative observable can be useful to help determine this cross section from the data taken in the HADES experiment.展开更多
ηN interactions are investigated in hot magnetized asymmetric nuclear matter using the chiral SU(3)model and chiral perturbation theory(ChPT).In the chiral modcl,thc in-medium properties of η-mesons are calcu-lated ...ηN interactions are investigated in hot magnetized asymmetric nuclear matter using the chiral SU(3)model and chiral perturbation theory(ChPT).In the chiral modcl,thc in-medium properties of η-mesons are calcu-lated using medium modified scalar densities under the influence of an extermal magnetic field.Further,in a com-bined chiral model and ChPT approach,off-shell contributions of the ηN interactions are evaluated from the ChPTeffective ηN Lagrangian,and the in-medium effect of scalar densities are incorporated from the chiral SU(3)model.We find that the magnetic field has a significant effect on the in-medium mass and optical potential of η mesons,andwe observe a deeper mass-shift in the combined chiral model and ChPT approach than in the solo chiral SU(3)model.In both approaches,no additional mass-shift is observed due to the uncharged nature of η mesons in the presenceof a magnetic field.展开更多
We study the inclusive production of strange vector K^∗(892)^+ mesons in π−A reactions at near-threshold laboratory incident pion momenta of 1.4-2.0 GeV/c via a nuclear spectral function approach.The approach account...We study the inclusive production of strange vector K^∗(892)^+ mesons in π−A reactions at near-threshold laboratory incident pion momenta of 1.4-2.0 GeV/c via a nuclear spectral function approach.The approach accounts for incoherent primary π−meson-proton π−p→K^∗(892)^+Σ^− production processes as well as the influence of the scalar K^∗(892)^+-nucleus potential(or the K^∗(892)^+ in-medium mass shift)on these processes.We calculate the absolute differential and total cross sections for the production of K∗(892)+mesons from carbon and tungsten nuclei at laboratory angles of 0∘-45∘and at the aforementioned momenta in five scenarios for the aforenoted shift.We show that the K^∗(892)^+ momentum distributions and their excitation functions(absolute and relative)possess a high sensitivity to changes in the in-medium K^∗(892)^+ mass shift in the low-momentum region of 0.1-0.6 GeV/c.Therefore,the measurement of such observables in a dedicated experiment at the GSI pion beam facility in the near-threshold momentum domain will allow us to get valuable information on the K^∗(892)^+ in-medium properties.展开更多
基金National Key R&D Program of China under Grant Nos.2023YFA1606400 and 2022YFA1602303National Natural Science Foundation of China under Grants Nos.12335007,12035001,11921006,12347106,12147101,and 12205340+1 种基金Gansu Natural Science Foundation under Grant No.22JR5RA123U.S.Department of Energy(DOE),Office of Science,under SciDAC-5(NUCLEI collaboration)。
文摘Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and consistent treatment of nuclear forces as inputs of modern many-body calculations,among which the in-medium similarity renormalization group(IMSRG)and its variants play a vital role.On the other hand,signifcant eforts have been made to provide a unifed description of the structure,decay,and reactions of the nuclei as open quantum systems.While a fully comprehensive and microscopic model has yet to be realized,substantial progress over recent decades has enhanced our understanding of open quantum systems around the dripline,which are often characterized by exotic structures and decay modes.To study these interesting phenomena,Gamow coupled-channel(GCC)method,in which the open quantum nature of few-body valence nucleons coupled to a deformed core,has been developed.This review focuses on the developments of the advanced IMSRG and GCC and their applications to nuclear structure and reactions.
基金Supported by National Natural Science Foundation of China under Grant Nos.11045006 and 11135011the Key Project from Chinese Academy of Sciences(12A0A0012)the President Foundation by the Graduate University of Chinese Academy of Sciences
文摘The in-medium quark condensate is studied with an equivalent-mass approach in which one does not need to make assumptions on the derivatives of model parameters with respect to the quark current mass.It is shown that the condensate is generally a decreasing function of both the density and temperature with the decreasing speed depending on the confinement parameter.Specially,at given density,the condensate decreases on increasing temperature.The decreasing speed is comparatively small at lower temperature,and becomes very fast at higher temperature.
基金The project supported in part by National Natural Science Foundation of China under Grant Nos. 10247004, 10565001, and the Natural Science Foundation of Guangxi Province of China undcr Grant Nos. 0481030, 0575020, and 0542042
文摘Based on the fully dressed confining quark propagator, the pion decay constant fπ, local quark vacuum condensate, and the masses of light quarks and in-medlum Goldstone bosons are investigated. The pion decay constant fπ is predicted and compared with its value of experimental measurement. A great agreement is obtained. With the predicted fπ and values of Goldstone boson masses measured by experiments in free configuration the current masses of light quarks and the masses of in-medium Goldstone bosons are obtained.
基金Major State Basic Research Development Program of China (2014CB845405, 2015CB856903), National NaturalScience Foundation of China(11175218, U1332207) and Youth Innovation Promotion Association of Chinese Academy of Sciences
文摘Extraction of the in-medium properties of strange particles from heavy-ion collisions is very complicated, since he nuclear density varies in the evolution of nucleus-nucleus collisions. To avoid the uncertainties of the baryon ensities during the stage of strange particle production, one can investigate proton-nucleus collisions where the uclear density is definite around the saturation density. Dynamics of strange particles produced in the protoninduced uclear the reactions near the threshold energies has been investigated within the Lanzhou quantum olecular dynamics (LQMD) transport model. The in-medium modifications on particle production in densenuclear matter are considered through the corrections to the elementary cross sections via the effective mass and he mean-field potentials[1].
基金Supported by National Natural Science Foundation of China(11875323,11875125,11475262,11365004,11375062,11790323,11790324,11790325)the National Key R&D Program of China(2018 YFA0404404)
文摘The in-medium NN→N△ cross sections and its differential cross sections in isospin asymmetric nuclear medium are investigated in the framework of the one-boson exchange model by including isovector mesons, i.e., δand p mesons. Our results show that the in-medium NN→N△ cross sections are suppressed when the density increases, and the differential cross sections become isotropic with an increase in the density around the △ threshold energy. The isospin splitting on the medium correction factor, R =σ_(NN→N△)~*/σ_(NN→N△)^(free) is observed for different channels of NN→N△, especially around the threshold energy for all the effective Lagrangian parameters. By analyzing the selected effective Lagrangian parameters, our results show that the larger effective mass is, the weaker medium correction R is.
基金This work was partly inspired by the transport code comparison project,and it was supported by the National Natural Science Foundation of China(11875323,11705163,11790320,11790323,11961141003)the National Key R&D Program of China(2018YFA0404404)+1 种基金the Continuous Basic Scientific Research Project(WDJC-2019-13,BJ20002501)the funding of China Institute of Atomic Energy。
文摘Three typical Pauli blocking algorithms in quantum molecular dynamics type models are investigated in the nuclear matter,the nucleus,and heavy ion collisions.In nuclear matter,the blocking ratios obtained with the three algorithms are underestimated by 13%-25%compared to the corresponding analytical values.For a finite nucleus,spurious collisions occur around the surface of the nucleus owing to the defects of the Pauli blocking algorithms.In the simulations of heavy ion collisions,the uncertainty of stopping power arising from the different Pauli blocking algorithms is less than 5%.Furthermore,the in-medium effects of nucleon-nucleon(NN)cross sections on the nuclear stopping power are discussed.Our results show that the transport model calculations with free NN cross sections result in the stopping power decreasing with beam energy when the beam energy is less than 300 MeV/u.To increase or decrease the values of the stopping power,the transport model calculations need enhanced or suppressed model dependent in-medium NN cross sections that are expected to be smaller than the true in-medium NN cross sections.
基金Supported by the National Natural Science Foundation of China(11905085)Guangdong Basic and Applied Basic Research Foundation(2022A1515110392)。
文摘This study examines the impact of the squeezing effect caused by the in-medium mass modification of particles on the three-dimensional Hanbury Brown-Twiss(HBT)radii.An analysis is conducted on how the squeezing effect impacts the three-dimensional HBT radii of,ϕϕ,D^(0)D^(0)and K^(+)K^(+).The squeezing effect suppresses the impact of transverse flow on the transverse source distribution and broadens the space-time rapidity distribution of the particle-emitting source,leading to an increase in the HBT radii,particularly in the out and longitudinal directions.This phenomenon becomes more significant for higher transverse pair momentum,resulting in a non-monotonic decrease in the HBT radii with increasing transverse pair momentum.The impact of the squeezing effect on the HBT radii is more pronounced for D^(0)D^(0)than forϕϕ.Furthermore,this effect is also more significant for D^(0)D^(0)than forϕϕ.The findings presented in this paper could offer fresh perspectives on investigating the squeezing effect.
基金supported by the National Key R&D Program of China(Nos.2024YFA1610900 and 2023YFA1606401)the National Natural Science Foundation of China(Nos.12335007 and 12035001)the United Kingdom Science and Technology Facilities Council(No.ST/V001108/1)。
文摘High multipole electromagnetic transitions are rare in nature.The highest-multipole transition observed in atomic nuclei is the electric hexacontatetrapole E6 transition from the T_(1/2)=2.54(2)-min J^(π)=1_(9/2)-isomer to the 7/2^(-)ground state in^(53)Fe with an angular momentum change of six units.In the present work,we performed ab initio calculations for this unique case by employing chiral effective field theory(EFT)forces.The in-medium similarity renormalization group is used to derive the valence-space effective Hamiltonian and multipolar transition operators.Bare nucleon charges were used in all the multipolar transition rate calculations,providing good agreement with the experimental data.The valence space takes the full fp shell.In^(53)Fe,the low-lying states were dominated by the 0f_(7/2)component.Two different versions of the chiral EFT two-plus three-nucleon interaction were used to test the dependence on the interaction used.We also tested the convergence of the transition rate calculations against the harmonic oscillator parameter hΩand basis truncations e_(max)and E_(3max)for twoand three-nucleon forces,respectively.
基金Yingxun Zhang acknowledges the supports in part by the National Natural Science Foundation of China(Grant Nos.11875323,11875125,11475262,10675172,11075215,11475262,11790323,11790324,11790325,and 11961141003)the National Key R&D Program of China(Grant No.2018YFA0404404)+15 种基金the Continuous Basic Scientific Research Project(No.WDJC-2019-13)Ning Wang acknowledges the supports in part by the National Natural Science Foundation of China(Nos.U1867212 and 11422548)the Guangxi Natural Science Foundation(Nos.2015G XNSFDA139004,2017G XNSFG A198001)Qingfeng Li acknowledges the supports in part by the National Natural Science Foundation of China(Nos.11875125,11847315,11375062,11505057,11947410,and 11747312)the Zhejiang Provincial Natural Science Foundation of China(No.LY18A050002)the“Ten-Thousand Talent Program”of Zhejiang ProvinceJunlong Tian acknowledges the supports in part by the National Science Foundation of China(Nos.11961131010 and 11475004)Li Ou acknowledges the supports in part by the National Natural Science Foundation of China(No.11965004)the Natural Science Foundation of Guangxi Province(No.2016GXNSFFA380001)Foundation of Guangxi Innovative Team and Distinguished Scholar in Institutions of Higher EducationMin Liu acknowledges the supports in part by the National Natural Science Foundation of China(No.11875323)Kai Zhao acknowledges the supports in part by the National Natural Science Foundation of China(Nos.11675266,11005155,11475262,11275052,11375062,11547312,and 11275068)the National Key Basic Research Developm ent Program of China(Nos.2007CB209900 and 2013CB834404)Xizhen Wu acknowledges the supports in part by the National Natural Science Foundation of China(Nos.10235020,10979023,11005155,11365004,11475004,and 11675266)Zhuxia Li acknowledges the supports in part by the National Natural Science Foundation of China(Nos.19975073,10175093,10175089,10235030,11275052,11375062,11475262,11475004,11875323,and 11875125)the National Key Basic Research Development Program of China(Nos.G20000774 and 2007CB209900).
文摘In this review article,we first briefty introduce the transport theory and quantum molecular dynamics model applied in the study of the heavy ion collisions from low to intermediate energies.The developments of improved quantum molecular dynamics model(ImQMD)and ultra-relativistic quantum molecular dynamics model(UrQMD),are reviewed.The reaction mechanism and phenomena related to the fusion,multinucleon transrer,fragmentation,collective flow and particle production are reviewed and discussed within the framework of the two models.The constraints on the isospin asymmetric muclear equation of state and in-medium nucleon nucleon cross sections by comparing the heavy ion collision data with transport models calculations in last decades are also discussed,and the uncertainties of these constraints are analyzed as well.Finally,we discuss the future direction of the development of the transport models for improving the understanding of the reaction mechanism,the descriptions of various observables,the constraint on the nuclear equation of state,as well as for the constraint on in-medium nucleon-nucleon cross sections.
基金Supported by National Natural Science Foundation of China(11675065,11875152,11905088)Fundamental Research Funds for the central universities(lzujbky-2019-11)the Supercompuer Center of HIRFL。
文摘The relativistic mean field(RMF)model has achieved great success in describing various nuclear phenomena.However,several serious defects are common.For instance,the pseudo-spin symmetry of high-l orbits is distinctly violated in general,leading to spurious shell closures N Z 58 and 92.This leads to problems in describing structure properties,including shell structures,nuclear masses,etc.Guided by the pseudo-spin symmetry restoration[Geng et al.,Phys.Rev.C,100:051301(2019)],a new RMF Lagrangian DD-LZ1 is developed by considering the density-dependent meson-nucleon coupling strengths.With the newly obtained RMF Lagrangian DD-LZ1,satisfactory descriptions can be obtained for the bulk properties of nuclear matter and finite nuclei.In particular,significant improvements on describing the single-particle spectra are achieved by DD-LZ1.In particular,the spurious shell closures Z 58 and 92,commonly found in previous RMF calculations,are eliminated by the new effective interaction DD-LZ1,and consistently the pseudo-spin symmetry(PSS)around the Fermi levels is reasonably restored for both low-l and high-l orbits.Moreover,the description of nuclear masses is also notably improved by DD-LZ1,as compared to the other RMF Lagrangians.
文摘We study the near-threshold pion-induced production ofφmesons off nuclei in the kinematical conditions of the HADES experiment,recently performed at GSI.The calculations have been performed within a collision model based on the nuclear spectral function.The model accounts for both the primaryπ^-meson–protonπ^-p→φn and the secondary pion–nucleonπN→φNφproduction processes as well as the effects of the nuclearφand nucleon mean-field potentials.We find that the primary reaction channelπ^-p→φn dominates in theφproduction off 12C and^（184）W target nuclei in the HADES acceptance window at incident pion momentum of 1.7 Ge V/c.We calculate the momentum dependence of the absolute and relative（transparency ratio）φmeson yields from the above direct channel.The calculations have been performed for this initial pion momentum allowing for different options for theφN absorption cross sectionσ（φN ）and different scenarios for the in-medium mass shifts of theφmeson and secondary neutron,produced together withφin this channel.We demonstrate that the transparency ratio for theφmesons has,contrary to the absolute cross sections,an insignificant sensitivity to theφmeson and secondary neutron in-medium mass shifts atφmomenta studied in the HADES experiment.On the other hand,we show that there are measurable changes in the transparency ratio due to theφN absorption cross section,which means that such a relative observable can be useful to help determine this cross section from the data taken in the HADES experiment.
文摘ηN interactions are investigated in hot magnetized asymmetric nuclear matter using the chiral SU(3)model and chiral perturbation theory(ChPT).In the chiral modcl,thc in-medium properties of η-mesons are calcu-lated using medium modified scalar densities under the influence of an extermal magnetic field.Further,in a com-bined chiral model and ChPT approach,off-shell contributions of the ηN interactions are evaluated from the ChPTeffective ηN Lagrangian,and the in-medium effect of scalar densities are incorporated from the chiral SU(3)model.We find that the magnetic field has a significant effect on the in-medium mass and optical potential of η mesons,andwe observe a deeper mass-shift in the combined chiral model and ChPT approach than in the solo chiral SU(3)model.In both approaches,no additional mass-shift is observed due to the uncharged nature of η mesons in the presenceof a magnetic field.
文摘We study the inclusive production of strange vector K^∗(892)^+ mesons in π−A reactions at near-threshold laboratory incident pion momenta of 1.4-2.0 GeV/c via a nuclear spectral function approach.The approach accounts for incoherent primary π−meson-proton π−p→K^∗(892)^+Σ^− production processes as well as the influence of the scalar K^∗(892)^+-nucleus potential(or the K^∗(892)^+ in-medium mass shift)on these processes.We calculate the absolute differential and total cross sections for the production of K∗(892)+mesons from carbon and tungsten nuclei at laboratory angles of 0∘-45∘and at the aforementioned momenta in five scenarios for the aforenoted shift.We show that the K^∗(892)^+ momentum distributions and their excitation functions(absolute and relative)possess a high sensitivity to changes in the in-medium K^∗(892)^+ mass shift in the low-momentum region of 0.1-0.6 GeV/c.Therefore,the measurement of such observables in a dedicated experiment at the GSI pion beam facility in the near-threshold momentum domain will allow us to get valuable information on the K^∗(892)^+ in-medium properties.
