Publications (66)217.58 Total impact
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ABSTRACT: A clustering aspect is explained for the $^9$Be nucleus in chargedlepton deep inelastic scattering. Nuclear modifications of the structure function $F_2$ are studied by the ratio $R_{\rm EMC} = F_2^A /F_2^D$, where $A$ and $D$ are a nucleus and the deuteron, respectively. In a JLab experiment, an unexpectedly large nuclear modification slope $dR_{\rm EMC}/dx$ was found for $^9$Be, which could be related to its clustering structure. We investigated a mean conventional part of a nuclear structure function $F_2^A$ by a convolution description with nucleon momentum distributions calculated by antisymmetrized (or fermionic) molecular dynamics (AMD) and also by a simple shell model. We found that clustering effects are small in the conventional part, so that the JLab result could be associated with an internal nucleon modification or a shortrange nuclear correlation which is caused by high densities due to cluster formation. 
Dataset: QMCReview PPNP58 1 2007
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ABSTRACT: The nucleon form factors in free space are usually thought to be modified when a nucleon is bound in a nucleus or immersed in a nuclear medium. We investigated effects of the densitydependent axial and weakvector form factors on the electroneutrino (ve) and antielectroneutrino (v̄e) reactions with incident energy Ev ≤ 80 MeV via neutral current (NC) and charged current (CC) for a nucleon in a nuclear medium or 12C. For the densitydependent form factors, we exploited the quarkmesoncoupling (QMC) model, and apply them to the v̄e and v̄e induced reactions by NC and CC. In CC reaction, about 5 % decrease of the electro neutrino (v̄e) reaction cross section on the nucleon is shown to be occurred in normal density, ρ=ρ0∼0.15fm 3, and also about 5 % reduction of total v̄e cross section on 12C is obtained by the modification of the weak form factors for bound nucleons. Density effects for both cases are relatively small, but they are as large as the effect by the Coulomb distortion of outgoing leptons in the νreaction. However, density effects in the antielectro neutrino (v̄e) reaction reduced significantly about 30 % the cross sections for both the nucleon and 12C cases. For NC, about 12 % decrease of the total cross section by the v̄e reaction on the nucleon is obtained at normal density, ρ=ρ0∼0.15fm3, as well as about 18 % reduction of the total v̄e cross section on 12C, by the modification of the weak form factors of the bound nucleon. However, similarly to the CC reaction, effects of the nucleon property change in the v̄e reaction reduce significantly the cross sections about 30 % for the nucleon in matter and 12C cases. In this talk, we address that such a large asymmetry in the v̄e cross sections in both reactions is originated from the different helicities of v̄e and v̄e.  [Show abstract] [Hide abstract]
ABSTRACT: Next generation neutrino oscillation experiments will need a quantitative understanding of neutrinonucleus interaction far better than ever. Kinematics covered by the relevant neutrinonucleus interaction spans wide region, from the quasielastic, through the resonance region, to the deeply inelastic scattering region. The neutrinonucleus interaction in each region has quite different characteristics. Obviously, it is essential to combine different expertise to construct a unified model that covers all the kinematical region of the neutrinonucleus interaction. Recently, several experimentalists and theorists got together to form a collaboration to tackle this problem. In this contribution, we report the collaboration’s recent activity and a goal in near future.  [Show abstract] [Hide abstract]
ABSTRACT: Using the quark–meson coupling (QMC) model, we study the density dependence of the quark and gluon condensates in nuclear matter. We show that the change of the quark condensate is mainly driven by the scalar field in the medium and that the reduction of the quark condensate is suppressed at high density, even in the meanfield approximation. The gluon condensate decreases by 4–6% at nuclear saturation density. We also give a simple relationship between the change of the quark condensate and that of a hadron mass in the medium.  [Show abstract] [Hide abstract]
ABSTRACT: Proposed a new method which is suitable for systematic calculations in fewbody systems, we call it the Jacobicoordinatebasis antisymmetrized molecular dynamics (JAMD). We show good abilities of the method by demonstrating some examples in atoms, molecules, nuclei, and baryons systems.  [Show abstract] [Hide abstract]
ABSTRACT: We report recent studies on structure functions of the nucleon and nuclei. First, clustering effects are investigated in the structure function F_2 of Be9 for explaining an unusual nuclear correction found in a JLab experiment. We propose that high densities created by formation of clustering structure like 2*alpha+neutron in Be9 is the origin of the unexpected JLab result by using the antisymmetrized molecular dynamics (AMD). There is an approved proposal at JLab to investigate the structure functions of light nuclei including the cluster structure, so that much details will become clear in a few years. Second, tensorpolarized quark and antiquark distributions are obtained by analyzing HERMES measurements on the structure function b_1 for the deuteron. The result suggests a finite tensor polarization for antiquark distributions, which is an interesting topic for further theoretical and experimental investigations. An experimental proposal exists at JLab for measuring b_1 of the deuteron as a new tensorstructure study in 2010's. Furthermore, the antiquark tensor polarization could be measured by polarized deuteron DrellYan processes at hadron facilities such as JPARC and GSIFAIR. Third, the recent CDF dijet anomaly is investigated within the standard model by considering possible modifications of the strangequark distribution. We find that the shape of a dijetmass spectrum changes depending on the strangequark distribution. It indicates that the CDF excess could be partially explained as a PDF effect, particularly by the strangeness in the nucleon, within the standard model if the excess at m_{jj}~140 GeV is not a sharp peak.  [Show abstract] [Hide abstract]
ABSTRACT: An anomalous nuclear modification was reported by JLab measurements on the beryllium9 structure function F_2. It is unexpected in the sense that a nuclear modification slope is too large to be expected from its average nuclear density. We investigated whether it is explained by a nuclear clustering configuration in Be9 with two \alpha nuclei and surrounding neutron clouds. Such clustering aspects are studied by using antisymmetrized molecular dynamics (AMD) and also by a simple shell model for comparison. We consider that nuclear structure functions F_2^A consist of a mean conventional part and a remaining one depending on the maximum local density. The first mean part does not show a significant cluster effect on F_2. However, we propose that the remaining one could explain the anonymous JLab slope, and it is associated with high densities created by the cluster formation in Be9. The JLab measurement is possibly the first signature of clustering effects in highenergy nuclear reactions. A responsible physics could be an internal nucleon modification, which is caused by the high densities due to the cluster configuration.  [Show abstract] [Hide abstract]
ABSTRACT: We report current status of global analyses on nuclear parton distribution functions (NPDFs). The optimum NPDFs are determined by analyzing highenergy nuclear reaction data. Due to limited experimental measurements, antiquark modifications have large uncertainties at x>0.2 and gluon modifications cannot be determined. A nuclear modification difference between u and d quark distributions could be an origin of the longstanding NuTeV sin^2 theta_w anomaly. There is also an issue of nuclear modification differences between the structure functions of chargedlepton and neutrino reactions. Next, nuclear clustering effects are discussed in structure functions F_2^A as a possible explanation for an anomalous result in the Be9 nucleus at the Thomas Jefferson National Accelerator Facility (JLab). Last, tensorpolarized quark and antiquark distribution functions are extracted from HERMES data on the polarized structure function b_1 of the deuteron, and they could be used for testing theoretical models and for proposing future experiments, for example, the one at JLab. Such measurements could open a new field of spin physics in spinone hadrons.  [Show abstract] [Hide abstract]
ABSTRACT: Prompted by the level of accuracy now being achieved in tests of the unitarity of the CKM matrix, we consider the possible modification of the Fermi matrix element for the $\beta$decay of a neutron, including possible inmedium and isospin violating corrections. While the nuclear modifications lead to very small corrections once the BehrendsSirlinAdemolloGatto theorem is respected, the effect of the $ud$ mass difference on the conclusion concerning $V_{ud}$ is no longer insignificant. Indeed, we suggest that the correction to the value of $V_{ud}^2 \, + \, V_{us}^2 \, + \, V_{ub}^2$ is at the level of $10^{4}$.  [Show abstract] [Hide abstract]
ABSTRACT: For understanding an anomalous nuclear effect experimentally observed for the beryllium9 nucleus at the Thomas Jefferson National Accelerator Facility (JLab), clustering aspects are studied in structure functions of deep inelastic leptonnucleus scattering by using momentum distributions calculated in antisymmetrized (or fermionic) molecular dynamics (AMD) and also in a simple shell model for comparison. According to the AMD, the Be9 nucleus consists of two alphalike clusters with a surrounding neutron. The clustering produces highmomentum components in nuclear wave functions, which affects nuclear modifications of the structure functions. We investigated whether clustering features could appear in the structure function F_2 of Be9 along with studies for other light nuclei. We found that nuclear modifications of F_2 are similar in both AMD and shell models within our simple convolution description although there are slight differences in Be9. It indicates that the anomalous Be9 result should be explained by a different mechanism from the nuclear binding and Fermi motion. If nuclearmodification slopes d(F_2^A/F_2^D)/dx are shown by the maximum local densities, the Be9 anomaly can be explained by the AMD picture, namely by the clustering structure, whereas it certainly cannot be described in the simple shell model. This fact suggests that the large nuclear modification in Be9 should be explained by large densities in the clusters. For example, internal nucleon structure could be modified in the highdensity clusters. The clustering aspect of nuclear structure functions is an unexplored topic which is interesting for future investigations.  [Show abstract] [Hide abstract]
ABSTRACT: We explain the current status of nuclear parton distribution functions in connection with neutrino‐nucleus interactions. Neutrino deep inelastic scattering (DIS) measurements have been done for heavy nuclear targets such as iron and lead. In order to extract structure functions of the nucleon, one needs to remove nuclear effects from the data. However, recent studies indicate that there are inconsistencies in nuclear modifications between charged‐lepton and neutrino scattering measurements. Nuclear medium effects could be also an origin for the NuTeV anomaly in the weak‐mixing angle. In addition, the modifications could affect neutrino‐oscillation experiments because some DIS events of neutrino‐oxygen nucleus interactions are contained. On the other hand, the nuclear medium effects themselves are interesting and important for describing nuclei in terms of quark and gluon degrees of freedom.  [Show abstract] [Hide abstract]
ABSTRACT: Proposed a new method which is suitable for systematic calculations in fewbody systems, we call it the Jacobicoordinatebasis antisymmetrized molecular dynamics (JAMD). We show good abilities of the method by demonstrating some examples in atoms, molecules, nuclei, and baryons systems. 
Article: Hyperons in nuclear matter
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ABSTRACT: The chiral version of the QMC model, in which the effect of gluon and pion exchanges is included selfconsistently, is applied to the hyperons in a nuclear medium. The hyperfine interaction due to the gluon exchange plays an important role in the inmedium baryon spectra, while the pioncloud effect is relatively small. At the quark meanfield level, the $\Lambda$ feels more attractive force than the \Sigma or \Xi in matter.  [Show abstract] [Hide abstract]
ABSTRACT: Using the volume coupling version of the cloudy bag model, the quark–meson coupling model is extended to study the role of pion field and the properties of nuclear matter. The extended model includes the effect of gluon exchange as well as the pioncloud effect, and provides a good description of the nuclear matter properties. The relationship between the extended model and the EFT approach to nuclear matter is also discussed. 
Article: A new molecular dynamics calculation and its application to the spectra of light and strange baryons
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ABSTRACT: A new approach based on antisymmetrized molecular dynamics is proposed to correctly take account of the manybody correlation. We applied it to the spectra of lowlying, light and strange baryons. The inclusion of the quarkquark correlation is vital to predict the precise spectra, and the semirelativistic kinematics is also important to correct the level ordering. The baryon spectra calculated by the present method is as precise as the Faddeev calculation.  [Show abstract] [Hide abstract]
ABSTRACT: We study the bound nucleon sigma term and the quark condensate in nuclear matter. In the quarkmeson coupling (QMC) model the nuclear correction to the sigma term is small and negative, i.e., it decelerates the decrease of the quark condensate in nuclear matter. However, the quark condensate in nuclear matter is controlled primarily by the scalarisoscalar $\sigma$ field. Compared to the leading term, it moderates the decrease more than that of the nuclear sigma term alone at densities around and larger than the normal nuclear matter density.  [Show abstract] [Hide abstract]
ABSTRACT: We review the effect of hadron structure changes in a nuclear medium using the quarkmeson coupling (QMC) model, which is based on a mean field description of nonoverlapping nucleon (or baryon) bags bound by the selfconsistent exchange of scalar and vector mesons. This approach leads to simple scaling relations for the changes of hadron masses in a nuclear medium. It can also be extended to describe finite nuclei, as well as the properties of hypernuclei and mesonnucleus deeply bound states. It is of great interest that the model predicts a variation of the nucleon form factors in nuclear matter. We also study the empirically observed, BloomGilman (quarkhadron) duality. Other applications of the model include subthreshold kaon production in heavy ion collisions, D and Dbar meson production in antiprotonnucleus collisions, and J/Psi suppression. In particular, the modification of the D and Dbar meson properties in nuclear medium can lead to a large J/Psi absorption cross section, which explains the observed J/Psi suppression in relativistic heavy ion collisions. 
Article: Twoscale scalar mesons in nuclei
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ABSTRACT: We generalize the linear sigma model in order to develop a chiralinvariant model of nuclear structure. The model is natural, and contains not only the usual sigma meson which is the chiral partner of the pion but also a new chiralsinglet that is responsible for the mediumrange nucleonnucleon attraction. This approach provides significant advantages in terms of its description of nuclear matter and finite nuclei in comparison with conventional models based on the linear sigma model. Comment: 12 pages, including 3 tables and 3 figures; preprint number is added  [Show abstract] [Hide abstract]
ABSTRACT: Effect of bound nucleon internal structure change on nuclear structure functions is investigated based on local quark–hadron duality. The bound nucleon structure functions calculated for chargedlepton and (anti)neutrino scattering are all enhanced in symmetric nuclear matter at large Bjorkenx (x≳0.85) relative to those in a free nucleon. This implies that a part of the enhancement observed in the nuclear structure function F2 (in the resonance region) at large Bjorkenx (the EMC effect) is due to the effect of the bound nucleon internal structure change. However, the x dependence for the chargedlepton and (anti)neutrino scattering is different. The former (latter) is enhanced (quenched) in the region 0.8≲x≲0.9 (0.7≲x≲0.85) due to the difference of the contribution from axial vector form factor. Because of these differences charge symmetry breaking in parton distributions will be enhanced in nuclei.
Publication Stats
2k  Citations  
217.58  Total Impact Points  
Top Journals
 Physics Letters B (23)
 Physical Review C (10)
 Nuclear Physics A (4)
 Australian Journal of Physics (2)
 Modern Physics Letters A (2)
Institutions

2014

JPARC Center
Ibaragi, Ōsaka, Japan


20032011

Tokyo University of Science
 Department of Fire Science and Technology
Edo, Tōkyō, Japan


19962000

University of Adelaide
 Special Research Centre for the Subatomic Structure of Matter
Tarndarnya, South Australia, Australia


1998

Sendai National College of Technology
Sendai, Kagoshima, Japan
