[Show abstract][Hide abstract] ABSTRACT: A clustering aspect is explained for the $^9$Be nucleus in charged-lepton
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
short-range nuclear correlation which is caused by high densities due to
cluster formation.
Journal of Physics Conference Series 08/2014; 569(1). DOI:10.1088/1742-6596/569/1/012021
[Show abstract][Hide abstract] ABSTRACT: Next generation neutrino oscillation experiments will need a
quantitative understanding of neutrino-nucleus interaction far better
than ever. Kinematics covered by the relevant neutrino-nucleus
interaction spans wide region, from the quasi-elastic, through the
resonance region, to the deeply inelastic scattering region. The
neutrino-nucleus 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 neutrino-nucleus 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 mean-field 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.
Modern Physics Letters A 11/2011; 13(10). DOI:10.1142/S0217732398000838 · 1.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Proposed a new method which is suitable for systematic calculations in few-body systems, we call it the Jacobi-coordinate-basis antisymmetrized molecular dynamics (JAMD). We show good abilities of the method by demonstrating some examples in atoms, molecules, nuclei, and baryons systems.
Modern Physics Letters A 11/2011; 24(11n13). DOI:10.1142/S0217732309000048 · 1.20 Impact Factor
[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
Be-9 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 Be-9 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, tensor-polarized 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 tensor-structure study in 2010's.
Furthermore, the antiquark tensor polarization could be measured by polarized
deuteron Drell-Yan processes at hadron facilities such as J-PARC and GSI-FAIR.
Third, the recent CDF dijet anomaly is investigated within the standard model
by considering possible modifications of the strange-quark distribution. We
find that the shape of a dijet-mass spectrum changes depending on the
strange-quark 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
beryllium-9 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 Be-9 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 Be-9. The JLab measurement is
possibly the first signature of clustering effects in high-energy 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 high-energy
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 long-standing NuTeV sin^2 theta_w
anomaly. There is also an issue of nuclear modification differences between the
structure functions of charged-lepton 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 Be-9 nucleus at the Thomas Jefferson
National Accelerator Facility (JLab). Last, tensor-polarized 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
spin-one 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 in-medium
and isospin violating corrections. While the nuclear modifications lead to very
small corrections once the Behrends-Sirlin-Ademollo-Gatto theorem is respected,
the effect of the $u-d$ 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
$10^{-4}$.
Physics Letters B 01/2011; 696(5). DOI:10.1016/j.physletb.2011.01.005 · 6.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: For understanding an anomalous nuclear effect experimentally observed for the
beryllium-9 nucleus at the Thomas Jefferson National Accelerator Facility
(JLab), clustering aspects are studied in structure functions of deep inelastic
lepton-nucleus 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 Be-9 nucleus consists of
two alpha-like clusters with a surrounding neutron. The clustering produces
high-momentum 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 Be-9 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 Be-9. It indicates that the anomalous Be-9
result should be explained by a different mechanism from the nuclear binding
and Fermi motion. If nuclear-modification slopes d(F_2^A/F_2^D)/dx are shown by
the maximum local densities, the Be-9 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 Be-9 should be explained by large densities in the clusters.
For example, internal nucleon structure could be modified in the high-density
clusters. The clustering aspect of nuclear structure functions is an unexplored
topic which is interesting for future investigations.
Physical Review C 08/2010; 83(3). DOI:10.1103/PhysRevC.83.035202 · 3.73 Impact Factor
[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. Comment: 8 pages, LaTeX, 9 eps files, to be published in AIP conference proceedings
[Show abstract][Hide abstract] ABSTRACT: The chiral version of the QMC model, in which the effect of gluon and
pion exchanges is included self-consistently, is applied to the hyperons
in a nuclear medium. The hyperfine interaction due to the gluon exchange
plays an important role in the in-medium baryon spectra, while the
pion-cloud effect is relatively small. At the quark mean-field 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 pion-cloud 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.
Physics Letters B 07/2008; 666(3-666):239-244. DOI:10.1016/j.physletb.2008.07.065 · 6.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new approach based on antisymmetrized molecular dynamics is proposed to correctly take account of the many-body correlation. We applied it to the spectra of low-lying, light and strange baryons. The inclusion of the quark-quark correlation is vital to predict the precise spectra, and the semi-relativistic kinematics is also important to correct the level ordering. The baryon spectra calculated by the present method is as precise as the Faddeev calculation.
Journal of Physics G Nuclear and Particle Physics 06/2008; 36(1). DOI:10.1088/0954-3899/36/1/015001 · 2.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study the bound nucleon sigma term and the quark condensate in nuclear matter. In the quark-meson 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 scalar-isoscalar $\sigma$ 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.
European Physical Journal A 09/2006; 31(4). DOI:10.1140/epja/i2006-10179-4 · 2.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Summary We have performed low-temperature heat capacity measurements on pellet samples of (DMe-DCNQI)2M (M=Li, Ag) which is known to show spin-Peierls transitions at 51 and 86 K, respectively. A linearly temperature-dependent term in the low-temperature heat capacity has been observed for both the samples: It is attributable to the spin-wave excitations induced by the inhomogeneous pressure effects produced in the pellet forming process. Although the temperature dependences of the magnetic susceptibility in both materials are almost the same, the coefficient of T-linear term of the Ag salt becomes three times larger that that of the Li salt. The peculiar electronic state originating from the competition of the spin-Peierls mechanism and the Coulomb repulsion is suggested.
Journal of Thermal Analysis and Calorimetry 08/2005; 81(3):587-590. DOI:10.1007/s10973-005-0828-x · 2.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Summary Using a thermal relaxation calorimetry technique, we have measured heat capacities of κ-(BEDT-TTF)4Hg2.89Br8 system under magnetic fields between 0 and 6 T. With the increase of cooling rate from room temperature to liquid helium temperature, we have observed a remarkable but systematic tendency that the thermal anomaly associated with the superconductive transition shifts to the lower temperatures. The course of this phenomenon is attributable to the degree of disorder in the mercury chains which give an incommensurate potential to the superconducting planes.
Journal of Thermal Analysis and Calorimetry 08/2005; 81(3):591-594. DOI:10.1007/s10973-005-0829-9 · 2.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Summary Thermogravimetry (TG) and Me2CO adsorption measurements for flexible porous crystalline coordination polymers with 2-dimensional (2-D) frameworks, {[Co(NCS)2(3-pia)2]·4Me2CO}n (1⊃4Me2CO, 3-pia=N-(3-pyridyl)isonicotinamide), were carried out. Taking advantages of capability of hydrogen bonding of amide groups for a dynamic properties, 1⊃4Me2CO show crystal (non-porous)-to-crystal (porous) structural rearrangement in Me2CO adsorption/desorption processes. The activation energy for the Me2CO desorption process of 1⊃4Me2CO was obtained using Flynn-Wall-Ozawa’s (FWO) method. The Me2CO adsorption isotherms on 1 have a threshold pressure (Pth) for abrupt accommodation of Me2CO molecules, which is regarded as the equilibrium pressure for the inclusion reaction of Me2CO
Journal of Thermal Analysis and Calorimetry 08/2005; 81(3). DOI:10.1007/s10973-005-0816-1 · 2.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We review the effect of hadron structure changes in a nuclear medium using the quark-meson coupling (QMC) model, which is based on a mean field description of non-overlapping nucleon (or baryon) bags bound by the self-consistent 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 meson-nucleus 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, Bloom-Gilman (quark-hadron) duality. Other applications of the model include subthreshold kaon production in heavy ion collisions, D and D-bar meson production in antiproton-nucleus collisions, and J/Psi suppression. In particular, the modification of the D and D-bar 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.
Progress in Particle and Nuclear Physics 07/2005; 58(1). DOI:10.1016/j.ppnp.2005.07.003 · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We generalize the linear sigma model in order to develop a chiral-invariant 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 chiral-singlet that is responsible for the medium-range nucleon-nucleon 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
European Physical Journal A 03/2005; 26(2). DOI:10.1140/epja/i2005-10170-7 · 2.74 Impact Factor