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1.
Few-body systems with large scattering length have universal properties that do not depend on the details of their interactions
at short distances. We study the universal bound-state properties of the four-boson system with large scattering length in
an effective quantum mechanics approach. We compute the four-body binding energies using the Yakubovsky equations for positive
and negative scattering length. Moreover, we study the correlation between three- and four-body energies and present a generalized
Efimov plot for the four-body system. These results are useful for understanding the cluster structure of nuclei and for the
creation of weakly bound tetramers with cold atoms close to a Feshbach resonance. 相似文献
2.
T. Mančal V. May 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):633-643
Non-Markovian dynamics in open quantum systems is characterized by a time-non-locality in the equation of motion valid for
the reduced density operator. An expansion of this density matrix equation with respect to Laguerre polynomials is used to
tackle the time-non-locality. The applicability and the numerical limitations of the method are discussed in detail. In order
to illuminate the characteristics of non-Markovian dynamics the reference example is studied of a single quantum degree of
freedom moving in a harmonic potential and being embedded in a heat bath. If interpreted as the photoinduced dynamics of nuclear
motion in polyatomic molecules we can suggest two clear signatures of non-Markovian dynamics observable in ultrafast optical
experiments, firstly a pronounced and somewhat irregular oscillatory behavior of the vibrational level populations, and secondly
a separation of the vibrational wavepacket into a double-structure.
Received 12 April 2000 and Received in final form 2 September 2000 相似文献
3.
Different momentum space Faddeev-like equations and their solutions for the radiative pd-capture and the three-nucleon photodisintegration of 3He are presented. Applications are based on the AV18 nucleon-nucleon and the Urbana IX three-nucleon forces. Meson exchange currents are included using the Siegert theorem. A very good agreement has been found in all cases indicating the reliability of the used numerical methods. Predictions for cross-sections and polarization observables in the pd-capture and the complete three-nucleon breakup of 3He at different incoming-deuteron/photon energies are presented. 相似文献
4.
The poor knowledge of the spin-dependent neutron scattering length of 3He has until now handicapped nuclear four body theory and the interpretation of excitations in the quantum liquid. We have measured, for the first time directly, the real part of the bound incoherent neutron scattering length, bi′ of 3He. A neutron spin echo spectrometer was used to detect pseudomagnetic precession of polarised neutrons passing through polarised 3He gas. Any absolute calibrations of sample and beam parameters were avoided using simple transmission measurements with non-polarised neutrons. The only a priory information required was the spin-dependent neutron absorption cross section of 3He. The result is bi′ = -2.365(20) fm, which reduces the prior uncertainty by a factor 30. The corresponding new value of the bound incoherent scattering cross section is σi = 1.532(12) barn. Including the known value of the coherent neutron scattering length, we obtain new values for the real parts of the free triplet and singlet neutron scattering lengths, a-′ = 7.370(58) fm and a+′ = 3.278(53) fm. 相似文献
5.
H. Arenhövel W. Leidemann E.L. Tomusiak 《The European Physical Journal A - Hadrons and Nuclei》2002,14(4):491-509
Formal expressions are derived for the multipole expansion of the structure functions of a general polarization observable
of exclusive electrodisintegration of the deuteron using a longitudinally polarized beam and/or an oriented target. This allows
one to exhibit explicitly the angular dependence of the structure functions by expanding them in terms of the small rotation
matrices d
j
m'm(θ), whose coefficients are given in terms of the electromagnetic multipole matrix elements. Furthermore, explicit expressions
for the coefficients of the angular distributions of the differential cross-section including multipoles up to L
max = 3 are listed in tabular form.
Received: 19 November 2002 / Accepted: 7 May 2002 相似文献
6.
The relativistic Faddeev equation for three-nucleon scattering is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial wave decomposition. Relativistic invariance is achieved by constructing a dynamical unitary representation of the Poincaré group on the three-nucleon Hilbert space. The exclusive breakup reaction at 508 MeV is calculated based on a Malfliet–Tjon type two-body interaction and the cross sections are compared to measured cross sections at this energy. We find that the magnitude of the relativistic effects can be quite large and depends on the configurations considered. In spite of the simple nature of the model interaction, the experimental cross sections are in surprisingly good agreement with the predictions of the relativistic calculations. We also find that although for specific configurations the multiple scattering series converges rapidly, this is in general not the case. 相似文献
7.
H. Arenhövel W. Leidemann E. L. Tomusiak 《The European Physical Journal A - Hadrons and Nuclei》2005,23(1):147-190
Polarization observables in inclusive and exclusive electrodisintegration of the deuteron using a polarized beam and an oriented target are systematically surveyed using the standard nonrelativistic framework of nuclear theory but with leading-order relativistic contributions included. The structure functions and the asymmetries corresponding to the various nucleon polarization components are studied in a variety of kinematic regions with respect to their sensitivity to realistic NN-potential models, to subnuclear degrees of freedom in terms of meson exchange currents, isobar configurations and to relativistic effects in different kinematical regions, serving as a benchmark for a test of present standard nuclear theory with effective degrees of freedom. 相似文献
8.
W. Ketter W. Heil G. Badurek M. Baron E. Jericha R. Loidl H. Rauch 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):243-256
Improved knowledge of the real part of the neutron scattering length of 3He is important for further development of nuclear few-body theory, as well as for a thorough understanding of neutron scattering
off quantum liquids. The real part of the bound incoherent neutron scattering length bi' has recently been measured directly with an experimental uncertainty of better than 1% by means of spin echo spectrometry.
The uncertainty of the more fundamental bound multiplet scattering lengths b±' is thus limited by today's 1.2% uncertainty of the spin-independent coherent part bc'. Employing the skew-symmetric perfect crystal Si-interferometer at the S18 experimental site at ILL, Grenoble, we have re-measured
the real part of the bound coherent neutron scattering length bc' of 3He. Our result bc' = 6.010(21)fm exhibits a significant deviation compared to the latest accepted value bc' = 5.74(7)fm (H. Kaiser, H. Rauch, G. Badurek, W. Bauspiess, U. Bonse, Z. Phys. A 291, 231 (1979)). Including the known value of the incoherent neutron scattering length, we obtain new values for the real parts
of the free singlet and triplet scattering lengths, a-' = 7.573(30)fm and a+' = 3.480(18)fm. Our result contravenes by more than 7 standard deviations the measurement of the same physical quantity that
has recently been performed by a group at NIST in a very similar experiment (P.R. Huffman, D.L. Jacobson, K. Schoen, M. Arif,
T.C. Black, W.M. Snow, S.A. Werner, Phys. Rev. C 70, 014004 (2004)) which yielded bc' = 5.853(7)fm. 相似文献
9.
H. Mardanpour H. R. Amir-Ahmadi A. Deltuva K. Itoh N. Kalantar-Nayestanaki T. Kawabata H. Kuboki Y. Maeda J. G. Messchendorp S. Sakaguchi H. Sakai N. Sakamoto Y. Sasamoto M. Sasano K. Sekiguchi K. Suda Y. Takahashi T. Uesaka H. Witała K. Yako 《The European Physical Journal A - Hadrons and Nuclei》2007,31(3):383-391
High-precision vector and tensor analyzing powers of elastic deuteron-proton ( d + p) scattering have been measured at intermediate energies to investigate effects of three-nucleon forces. Angular distributions
in the range of 70°-120° in the center-of mass frame for incident-deuteron energies E
d
lab = 130 and 180 MeV were obtained using the RIKEN facility. The beam polarization was unambiguously determined by measuring
the ^12C (d, α)^10B(2+) reaction at 0°. Results of the measurements are compared with state-of-the-art three-nucleon calculations. The present modeling of nucleon-nucleon
forces and its extension to the three-nucleon system is not sufficient to describe the high-precision data consistently and
requires, therefore, further investigation. 相似文献
10.
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
11.
12.
The reaction pn↦dφ is studied within a covariant boson exchange model. The behavior of polarization observables being accessible in forthcoming
experiments near threshold is predicted.
Received: 13 February 2001 / Accepted: 25 March 2002 相似文献
13.
M. Janek T. Saito V. P. Ladygin T. Uesaka M. Hatano A. Yu. Isupov H. Kato N. B. Ladygina Y. Maeda A. I. Malakhov J. Nishikawa T. Ohnishi H. Okamura S. G. Reznikov H. Sakai S. Sakoda N. Sakamoto Y. Satou K. Sekiguchi K. Suda A. Tamii N. Uchigashima T. A. Vasiliev K. Yako 《The European Physical Journal A - Hadrons and Nuclei》2007,33(1):39-46
The data on the tensor Ayy, Axx, Axz and vector Ay analyzing powers in the dd → ^3Hen obtained at T
d = 270 MeV in the angular range 0° - 110° in the c.m. are presented. The observed negative sign of the tensor analyzing powers Ayy, Axx and Axz at small angles clearly demonstrate the sensitivity to the ratio of the D - and S -wave component of the 3He wave function. However, the one-nucleon exchange calculations by using the standard 3He wave functions have failed to reproduce the strong variation of the tensor analyzing powers as a function of the angle
in the c.m. 相似文献
14.
15.
E. Epelbaum 《The European Physical Journal A - Hadrons and Nuclei》2007,34(2):197-214
We discuss in detail the derivation of the leading four-nucleon force in chiral effective field theory using the method of
unitary transformation. The resulting four-nucleon force is given in both momentum and configuration space. It does not contain
any unknown parameters and can be used in few- and many-nucleon studies. 相似文献
16.
M. Viviani 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):429-434
In this contribution a brief overview of the status and perspectives of the theoretical methods for studying light and heavy
nuclear systems is presented. 相似文献
17.
D. Andreasi S. Quaglioni V. D. Efros W. Leidemann G. Orlandini 《The European Physical Journal A - Hadrons and Nuclei》2006,27(1):47-52
The two-body knock-out reaction 4He(e, e'd )d is calculated at various momentum transfers. The full four-nucleon dynamics is taken into account microscopically both in
the initial and the final states. As NN interaction the central MT-I/III potential is used. The calculation shows a strong
reduction of the coincidence cross-section due to the final-state interaction. Nonetheless, the theoretical results exhibit
a considerable overestimation of the experimental cross-section at lower momentum transfer. Comparisons with other, less complete,
calculations suggest that consideration of a more realistic ground state might not be sufficient for a good agreement with
experiment, rather a more realistic final-state interaction could play an essential role. 相似文献
18.
19.
We address the construction of transition operators for electromagnetic, weak, and hadronic reactions of relativistic few-quark systems along the spectator model. While the problem is of relevance for all forms of relativistic quantum mechanics, we specifically adhere to the point form, since it preserves the spectator character of the corresponding transition operators in any reference frame. The conditions imposed on the construction of point-form spectator-model operators are discussed and their implications are exemplified for mesonic decays of baryon resonances within a relativistic constituent-quark model. 相似文献
20.
K. M. Nollett 《The European physical journal. Special topics》2007,144(1):155-160
Over the last fifteen years, there has been tremendous
progress in understanding how nuclear structure arises from the
nucleon-nucleon interaction. I describe the contribution to this
progress made by quantum Monte Carlo computational methods, as well as
directions to be taken in future work. Most effort in the past has
concentrated on energy spectra, and we have had good success in
computing the spectra of systems with A≤12. We are now shifting
our attention to off-diagonal and scattering/reaction properties of
the light nuclei. I also discuss briefly the relation of quantum
Monte Carlo methods to other ab initio methods and their
particular relevance for weakly-bound nuclei produced at
radioactive-beam facilities. 相似文献