共查询到20条相似文献,搜索用时 31 毫秒
1.
Scales in nuclear matter: Chiral dynamics with pion nucleon form factors<Superscript>⋆</Superscript>
N. Kaiser M. Mühlbauer W. Weise 《The European Physical Journal A - Hadrons and Nuclei》2007,31(1):53-60
A systematic calculation of nuclear matter is performed which includes the long-range correlations between nucleons arising
from one- and two-pion exchange. Three-body effects from 2π exchange with excitations of virtual Δ(1232)-isobars are also
taken into account in our diagrammatic calculation of the energy per particle ˉ(k
f). In order to eliminate possible high-momentum components from the interactions we introduce at each pion-baryon vertex a
form factor of monopole type. The empirical nuclear matter saturation point, ρ0 ≃ 0.16fm^-3, ˉ0 ≃ - 16MeV, is well reproduced with a monopole mass of Λ ≃ 4πf
π ≃ 1.16GeV. As in the recent approach based on the universal low-momentum NN potential V
low-k, the inclusion of three-body effects is crucial in order to achieve saturation of nuclear matter. We demonstrate that the
dependence of the pion exchange contributions to ˉ(k
f) on the “resolution” scale Λ can be compensated over a wide range of Λ by counterterms with two “running” contact couplings.
As a further application we study the in-medium chiral condensate 〈ˉq〉(ρ) beyond the linear density approximation. For ρ ⩽ 1.5ρ0 we find small corrections from the derivative dˉ(k
f)/dm
π, which are stable against variations of the monopole regulator mass Λ. 相似文献
2.
B.-Q. Ma I. Schmidt J.-J. Yang 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):353-359
We investigate the spin structure of the nucleon in an extended Jaffe-Lipkin quark model. In addition to the conventional
3q structure, different (3q)(Q
) admixtures in the nucleon wave function are also taken into account. The contributions to the nucleon spin from various
components of the nucleon wave function are discussed. The effect due to the Melosh-Wigner rotation is also studied. It is
shown that the Jaffe-Lipkin term is only important when antiquarks are negatively polarized. We arrive at a new “minimal”
quark model, which is close to the naive quark model, in order to understand the proton spin “puzzle”.
Received: 4 November 2000 / Accepted: 23 October 2001 相似文献
3.
Qingrong Zheng Gang Su Jian Wang Hong Guo 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):233-238
We report a theoretical analysis of the phonon thermal conductance, κ(T), for single wall carbon nanotubes (SWCN). In a range of low temperatues up to 100 K, κ(T) of perfect SWCN is found to increase with temperature, approximately, in a parabolic fashion. This is qualitatively consistent
with recent experimental measurements where the tube-tube interactions are negligibly weak. When the carbon-carbon bond length
is slightly varied, κ(T) is found to be qualitatively unaltered which implies that the anharmonic effect does not change the qualitative behavior
of κ(T).
Received 12 June 2001 相似文献
4.
Shi-Lin Zhu 《The European Physical Journal A - Hadrons and Nuclei》1999,4(3):277-281
The light cone QCD sum rules are derived for the K
*
Kπ coupling g
K
*
Kπ and the ρππ coupling g
ρππ. The contribution from the excited states and the continuum is subtracted cleanly through the double Borel transform with
respect to the two external momenta, p
1
2, p
2
2= (p−q)2. Our result g
K
*
Kπ= (8.7 ± 0.5) and g
ρππ= (11.5 ± 0.8) is in good agreement with the experimental value.
Received: 31 July 1998 / Revised version: 20 November 1998 相似文献
5.
Hungchong Kim 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):121-125
Within the conventional QCD sum rules, we calculate the πNN coupling constant, g
πN, beyond the chiral limit using two-point correlation function with a pion. For this purpose, we consider the Dirac structure,
iγ5, at m
π
2 order in the expansion of the correlator in terms of the pion momentum. For a consistent treatment of the sum rule, we include
the linear terms in quark mass as they constitute the same chiral order as m
π
2. In this sum rule, we obtain g
πN= 13.3 ± 1.2, which is very close to the empirical πNN coupling. This demonstrates that going beyond the chiral limit is crucial in determining the coupling.
Received: 8 July 1999 / Revised version: 20 August 1999 相似文献
6.
Yun Chang Shin Bong Soo Han Myung Ki Cheoun K.S. Kim Il-Tong Cheon 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):269-276
A SU(2) effective Lagrangian is extended to a SU
L(3) ⊗SU
R(3) by including the vector and axial vector meson. With this effective Lagrangian, electromagnetic form factors of charged
pion and kaon are calculated in both time- and space-like regions. The pseudoscalar meson loops are taken into account. Good
agreement with experimental data is obtained for those form factors and charged pseudoscalar meson radii. Decay widths of
ρ→ππ and φ→K
+
K
- are also calculated and shown to agree with experimental data very well.
Received: 20 December 1999 / Accepted: 12 October 2000 相似文献
7.
K.C. Chung C.S. Wang A.J. Santiago J.W. Zhang 《The European Physical Journal A - Hadrons and Nuclei》2001,12(2):161-167
The parameters of the σ-ω-ρ model in the relativistic mean-field theory with nonlinear σ-meson self-interaction are determined
by nuclear-matter properties, which are taken as those extracted by fits to data based on nonrelativistic nuclear models.
The values of the relevant parameters are C
σ
2∼ 94, C
ω
2∼ 32, C
ρ
2∼ 26, b∼ - 0.09, c∼ 1, and the σ-meson mass m
σ∼ 370 MeV, while the value of the calculated nuclear- surface thickness is t∼ 1.4 fm. The field system is shown to be stable, since the σ-meson self-interaction energy is a lower bound in this whole
parameter region with positive c. On the other hand, the effective nucleon mass M* is larger than 0.73M, if the symmetry incompressibility Ks is assumed to be negative and the nuclear-matter incompressibility K0 is kept less than 300 MeV.
Received: 27 June 2001 / Accepted: 5 October 2001 相似文献
8.
A ππ, ˉKK, and ρρ(ωω) fully coupled channel model is used to predict the lowest isospin S, P, D, F-wave phase shifts and inelasticities
for elastic ππ scattering from threshold to 2.0 GeV. As input the S-matrix is required to exhibit poles corresponding to the
meson resonance table of the Particle Data Group. As expected, the ππ inelasticity is very strongly related to the opening
of the ˉK channel near 1 GeV, and the opening of ρρ(4π) and ωω(6π) channels in the 1.5 GeV region. The predictions of this model are
compared to the various elastic ππ→ππ amplitudes, that were obtained from analyses of π− p →π−π+n data. The role of the various resonances, in particular the glueball candidate f
0(1500) and the f
J(1710) is investigated.
Received: 19 November 1997 相似文献
9.
S. Choe 《The European Physical Journal A - Hadrons and Nuclei》1998,3(1):65-73
In the QCD sum rule approach we predict the Λ (1405) mass by choosing the π0Σ0 multiquark interpolating field. It is found that the mass is about 1.419 GeV from Π1 (q
2) sum rule which is more reliable than Πq (q
2) sum rule, where Πq (q
2) and Π1 (q
2) are two invariant functions of the correlator Π (q
2). We also present the sum rules for the K
+
p and the π+Σ+ multiquark states, and compare to those for the π0Σ0 multiquark state. The mass of the Λ (1600) can be also reproduced in our approach.
Received: 11 November 1997 / Revised version: 28 April 1998 相似文献
10.
Y.C. Shin M.K. Cheoun K.S. Kim T.K. Choi 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):87-93
A role of the axial-vector mesons, such as K1 and a1, on the emitted-photon spectrum in hot hadronic matter is studied through the channels πρ→a
1→πγ and Kρ→K
1→Kγ. Both channels could be dominant over the region lower than E
γ∼ 0.5 GeV, while the role of the K1 meson is diminished in the higher E
γ region. This study is carried out with an SU
L(3) ⊗SU
R(3) effective chiral Lagrangian which includes vector and axial-vector mesons systematically and explains well their hadronic
and radiative decays simultaneously.
Received: 8 August 2001 / Accepted: 4 February 2002 相似文献
11.
I.G. Alekseev N.A. Bazhanov Yu.A. Beloglazov P.E. Budkovsky E.I. Bunyatova V.P. Kanavets A.I. Kovalev L.I. Koroleva S.P. Kruglov B.V. Morozov V.M. Nesterov D.V. Novinsky V.V. Ryltsov V.A. Shchedrov A.D. Sulimov V.V. Sumachev D.N. Svirida V.Yu. Trautman V.V. Zhurkin 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):117-120
The spin rotation parameters A and R were measured for the elastic pion-proton scattering by the PNPI-ITEP collaboration in the D13(1700) resonance region. The main goal of the experimental program is to resolve the current partial-wave analyses (PWA) uncertainties.
Simultaneously with A and R the polarization parameter P was measured with the purpose to improve the experimental database and estimate systematic errors. The constraint which demands
a smooth energy dependence of all π-
p transverse amplitude zeros in the complex plane together with the new experimental data on A parameter can lead to the conclusion that the Barrelet branch of “zero trajectories" is chosen improperly in PWA of the Carnegie-Mellon-Lawrence-Berkely-Laboratory
groups at the range of the pion beam momentum near 1.0 GeV/c. The setup included a longitudinally polarized proton target with superconductive magnet, multiwire spark chambers and carbon
polarimeter with thick filter. The experiment was performed at the ITEP proton synchrotron, Moscow.
Received: 17 August 2001 / Accepted: 13 September 2001 相似文献
12.
We compute the dynamical structure factor S(q,τ) of an elastic medium where force dipoles appear at random in space and in time, due to “micro-collapses” of the structure.
Various regimes are found, depending on the wave vector q and the collapse time θ. In an early time regime, the logarithm of the structure factor behaves as (qτ)3/2, as predicted in (L. Cipelletti et al., Phys. Rev Lett. 84, 2275 (2000)) using heuristic arguments. However, in an intermediate-time regime we rather obtain a (qτ)5/4 behaviour. Finally, the asymptotic long-time regime is found to behave as q
3/2τ. We also give a plausible scenario for aging, in terms of a strain-dependent energy barrier for micro-collapses. The relaxation
time is found to grow with the age tw, quasi-exponentially at first, and then as t
w
4/5 with logarithmic corrections.
Received 15 April 2002 相似文献
13.
We compute the dynamical structure factor S(q,τ) of an elastic medium where force dipoles appear at random in space and in time, due to “micro-collapses” of the structure.
Various regimes are found, depending on the wave vector q and the collapse time θ. In an early-time regime, the logarithm of the structure factor behaves as (qτ)3/2, as predicted in L. Cipelletti, S. Manley, R.C. Ball, D.A. Weitz, Phys. Rev. Lett. 84, 2275 (2000) using heuristic arguments. However, in an intermediate-time regime we rather obtain a (qτ)5/4 behaviour. Finally, the asymptotic long-time regime is found to behave as q
3/2τ. We also give a plausible scenario for aging, in terms of a strain-dependent energy barrier for micro-collapses. The relaxation
time is found to grow with the age t
w, quasi-exponentially at first, and then as t
w
4/5 with logarithmic corrections.
Received 23 July 2001 相似文献
14.
L.V. Fil'kov V.L. Kashevarov E.S. Konobeevski M.V. Mordovskoy S.I. Potashev V.A. Simonov V.M. Skorkin S.V. Zuev 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):369-374
The analysis of new experimental data, obtained at the Proton Linear Accelerator of INR, with the aim to search for supernarrow
dibaryons in the pd↦ppX
1 and pd↦pdX
2 reactions is presented. Narrow peaks with an experimental width of 5 MeV at masses of 1904±2, 1926±2, and 1942±2 MeV have
been observed in missing mass M
pX1 spectra. In the missing mass M
X1 spectra, the peaks at M
X1 = 966±2, 986±2, and 1003±2 MeV have been found. The analysis of the data obtained leads to the conclusion that the observed
peaks in M
pX1 spectra are most likely supernarrow dibaryons, the decay of which into two nucleons is forbidden by the Pauli exclusion principle.
An alternative interpretation of the spectra by assuming a decay of the supernarrow dibaryons in “exotic baryon states” with
masses M
X1 is discussed.
Received: 22 October 2001 / Accepted: 15 November 2001 相似文献
15.
H. -W. Hammer D. R. Phillips L. Platter 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):335-347
We use an effective field theory (EFT) which contains only short-range interactions to study the dependence of a variety of
three-nucleon observables on the pion mass. The pion-mass dependence of input quantities in our “pionless” EFT is obtained
from a recent chiral EFT calculation. To the order we work at, these quantities are the 1
S
0 scattering length and effective range, the deuteron binding energy, the 3
S
1 effective range, and the binding energy of one three-nucleon bound state. The chiral EFT input we use has the inverse 3
S
1 and 1
S
0 scattering lengths vanishing at m
π
crit = 197.8577 MeV. At this “critical” pion mass, the triton has infinitely many excited states with an accumulation point at
the three-nucleon threshold. We compute the binding energies of these states up to next-to-next-to-leading order in the pionless
EFT and study the convergence pattern of the EFT in the vicinity of the critical pion mass. Furthermore, we use the pionless
EFT to predict how doublet and quartet nd scattering lengths depend on m
π in the region between the physical pion mass and m
π = m
π
crit . 相似文献
16.
Sun Guoya Xing D.Y. Shen R. Lin H.Q. 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):33-38
The Nambu spinor Green's function approach is applied to calculating the density of states (DOS) and superconducting order
parameter in normal-metal/insulator/ferromagnet/superconductor (NM/I/FM/SC) junctions. It is found that the s-wave superconductivity and ferromagnetism can coexist near the FM/SC interface, which is induced by proximity effect. On
the SC side, the spin-dependent DOS appears both within and without the energy gap. On the FM side, the superconducting order
parameter displays a damped oscillation and the DOS exhibits some superconducting behavior. The calculated result for the
DOS in FM for “0 state” and “π state” can reproduce recent tunneling spectra in Al/Al2O3/PdNi/Nb tunnel junctions.
Received 1st July 2002 Published online 19 November 2002 相似文献
17.
D. Cabrera D. Fernández-Fraile A. Gómez Nicola 《The European Physical Journal C - Particles and Fields》2009,61(4):879-892
We present a study of the π
π scattering amplitude in the σ and ρ channels at finite temperature and nuclear density within a chiral unitary framework. Meson resonances are dynamically generated
in our approach, which allows us to analyze the behavior of their associated scattering poles when the system is driven towards
chiral-symmetry restoration. Medium effects are incorporated in three ways: (a) by thermal corrections of the unitarized scattering
amplitudes, (b) by finite nuclear-density effects associated to a renormalization of the pion decay constant, and complementarily
(c) by extending our calculation of the scalar–isoscalar channel to account for finite nuclear-density and temperature effects
in a microscopic many-body implementation of pion dynamics. Our results are discussed in connection with several phenomenological
aspects relevant for nuclear-matter and heavy-ion collision experiments, such as ρ mass scaling versus broadening from dilepton spectra and chiral restoration signals in the σ channel. We also elaborate on the molecular nature of π
π resonances. 相似文献
18.
M. Bender T. Cornelius G.A. Lalazissis J.A. Maruhn W. Nazarewicz P.-G. Reinhard 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):23-28
Recent mass measurements show a substantial weakening of the binding-energy difference δ2p(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + 2, N) in the neutron-deficient Pb isotopes. As δ2p is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ2p is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms
of deformed ground states of Hg and Po isotopes.
Received: 25 October 2001 / Accepted: 28 February 2002 相似文献
19.
V.A. Pryamitsyn A.N. Semenov T.C.B. McLeish 《The European physical journal. E, Soft matter》2001,4(2):161-171
An analytical one-dimensional model of the microphase separation in symmetric diblock copolymers is developed. Three stages
of the process of the microphase segregation of a quenched diblock copolymer system into a lamella structure are predicted.
The first stage involves a fast increase of the amplitude of the quasi-periodical lamella structure (with the average wave
vector q0) up to a nearly equilibrium value; the second stage is a slow phase diffusion process which is characterized by increasing
coherency of the lamella structure; the third stage is the slow process of the lamella swelling, which is driven by the thermally
activated process of the spontaneous deletion of excessive lamellas, the lamella size increasing from the initial value 2π/q
0 to the equilibrium 2π/q
eq > 2π/q
0 during the process. The last two stages are described with the specially introduced coarse-grained “amplitude-phase” approximation.
It is shown that the relaxation of the gradient of the phase of the lamellar structure is the slowest relaxation process and,
thus, can be used as an effective order parameter of the lamellar structure at the later stages of the microphase segregation.
Received 10 March 2000 and Received in final form 5 June 2000 相似文献
20.
Verneuil E Clain J Buguin A Brochard-Wyart F 《The European physical journal. E, Soft matter》2003,10(4):345-353
A soft bead (radius R
b) is pressed with a force F against a hydrophobic glass plate through a water drop (“wet” JKR set-up). We observe with a fast camera the growth of the
contact zone bridging the rubber bead to the glass. Depending on the approach velocity V, two regimes are observed : i) at large V a liquid film is squeezed at the interface and dewets by nucleation and growth of a dry contact; ii) at low velocities, the
bead remains nearly spherical. As it comes into contact, the rubber bead spreads on the glass with a characteristic time (in
the range of one millisecond) τ ≈ ηR
b
2/F, where η is the liquid viscosity. The laws of spreading are interpreted by a balance of global mechanical and viscous forces.
Received: 22 December 2002 / Accepted: 24 March 2003 / Published online: 29 April 2003
RID="a"
ID="a"e-mail: brochard@curie.fr 相似文献