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1.
2.
H. Krebs E. Epelbaum U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2007,32(2):127-137
We study the two-nucleon force at next-to-next-to-leading order in a chiral effective field theory with explicit Δ degrees of freedom. Fixing the appearing low-energy constants from a next-to-leading-order calculation of pion-nucleon threshold
parameters, we find an improved convergence of most peripheral nucleon-nucleon phases compared to the theory with pions and
nucleons only. In the delta-full theory, the next-to-leading-order corrections are dominant in most partial waves considered. 相似文献
3.
B. R. Holstein 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):505-511
The subject of hadronic parity violation is nearly fifty years old, but a good deal of uncertainty remains, despite many efforts
both theoretical and experimental. A brief summary of the field is presented and a plan is proposed for new experimental work
which, when combined with a new theoretical tack based on effective field theory, should lead to resolution of the present
difficulties. 相似文献
4.
D. G. Middleton J. R. M. Annand C. Barbieri P. Barneo H. P. Blok R. Böhm M. O. Distler J. Friedrich C. Giusti D. I. Glazier P. Grabmayr T. Hehl J. Heim W. H. A. Hesselink E. Jans M. Kohl L. Lapikás I. J. D. MacGregor I. Martin J. C. McGeorge H. Merkel F. Moschini G. Rosner M. Seimetz H. de Vries Th. Walcher D. P. Watts B. Zihlmann 《The European Physical Journal A - Hadrons and Nuclei》2006,29(3):261-270
This paper reports on the first measurement of the 16O(e, e'pn)14N reaction. Data were measured in kinematics centred on a super-parallel geometry at energy and momentum transfers of 215MeV
and 316MeV/c. The experimental resolution was sufficient to distinguish groups of states in the residual nucleus but not good enough to
separate individual states. The data show a strong dependence on missing momentum and this dependence appears to be different
for two groups of states in the residual nucleus. Theoretical calculations of the reaction using the Pavia code do not reproduce
the shape or the magnitude of the data.
An erratum to this article is available at. 相似文献
5.
We suggest a method of singular terms regularization in a potential model of the N¯ interaction. This method is free from uncertainties related to the usual cut-off procedure and is based on the fact that, in the presence of sufficiently strong short-range annihilation, N and ¯ never approach close enough to each other. In such a case the low-energy scattering is shown to be fully determined by the OBEP tail, while any details of the short-range core of the N¯ interaction are excluded from the observables. The obtained results for S- and P-wave scattering lengths are in agreement with the well-established theoretical models. 相似文献
6.
P. Klüpfel J. Erler P. -G. Reinhard J. A. Maruhn 《The European Physical Journal A - Hadrons and Nuclei》2008,37(3):343-355
We study nucleon-nucleon scattering on the lattice at next-to-leading order in chiral effective field theory. We determine
phase shifts and mixing angles from the properties of two-nucleon standing waves induced by a hard spherical wall in the center-of-mass
frame. At fixed lattice spacing we test model independence of the low-energy effective theory by computing next-to-leading-order
corrections for two different leading-order lattice actions. The first leading-order action includes instantaneous one-pion
exchange and same-site contact interactions. The second leading-order action includes instantaneous one-pion exchange and
Gaussian-smeared interactions. We find that in each case the results at next-to-leading order are accurate up to corrections
expected at higher order. 相似文献
7.
B. Borasoy E. Epelbaum H. Krebs D. Lee U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2007,34(2):185-196
We determine two-particle scattering phase shifts and mixing angles for quantum theories defined with lattice regularization.
The method is suitable for any non-relativistic effective theory of point particles on the lattice. In the center-of-mass
frame of the two-particle system we impose a hard spherical wall at some fixed large radius. For channels without partial-wave
mixing the partial-wave phase shifts are determined from the energies of the nearly spherical standing waves. For channels
with partial-wave mixing further information is extracted by decomposing the standing wave at the wall boundary into spherical
harmonics, and we solve coupled-channels equations to extract the phase shifts and mixing angles. The method is illustrated
and tested by computing phase shifts and mixing angles on the lattice for spin-1/2 particles with an attractive Gaussian potential
containing both central and tensor force parts. 相似文献
8.
T. Skorodko M. Bashkanov D. Bogoslawsky H. Calen F. Cappellaro H. Clement L. Demiroers E. Doroshkevich D. Duniec C. Ekström K. Franssen L. Gustafsson B. Höistad G. Ivanov M. Jacewicz E. Jiganov T. Johansson O. Khakimova M. Kaskulov S. Keleta I. Koch F. Kren S. Kullander A. Kupść A. Kuznetsov P. Marciniewski R. Meier B. Morosov C. Pauly H. Petterson Y. Petukhov A. Povtorejko K. Schönning W. Scobel B. Shwartz V. Sopov J. Stepeniak P. Thörngren-Engblom V. Tikhomirov G. J. Wagner M. Wolke A. Yamamoto J. Zabierowski J. Złomanczuk 《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):317-319
In most investigations the Roper resonance is sensed only very indirectly via complex partial-wave analyses. We find indications
for its excitation in the invariant nπ+ mass spectrum of the pp → npπ+ reaction at M ≈ 1360 MeV with a width of ≈ 150 MeV . The values fit very favorably to the most recent phase shift results as well as to
the observations at BES. In the near-threshold two-pion production pp → ppπ0π0 , where the Roper excitation and its subsequent decays via the routes N
* → Δπ → Nππ and N
* → Nσ are the only dominant processes, we find its direct decay into the Nσ channel to be the by far dominating decay process --in favor of a monopole excitation of the Roper resonance. 相似文献
9.
M. Abdel-Bary K. -Th. Brinkmann H. Clement E. Doroshkevich S. Dshemuchadse A. Erhardt W. Eyrich H. Freiesleben A. Gillitzer R. Jäkel L. Karsch K. Kilian E. Kuhlmann K. Möller H. P. Morsch L. Naumann N. Paul C. Pizzolotto J. Ritman E. Roderburg W. Schroeder M. Schulte-Wissermann Th. Sefzick A. Teufel A. Ucar W. Ullrich P. Wintz P. Wüstner P. Zupranski 《The European Physical Journal A - Hadrons and Nuclei》2008,36(1):7-16
The quasifree reaction
was studied in a kinematically complete experiment by bombarding a liquid-hydrogen target with a deuteron beam of momentum
1.85GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton
was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight
direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector
n which differed from event to event. A range of almost 90MeV excess energy above threshold was covered. Energy-dependent angular
distributions, invariant-mass spectra as well as fully covered Dalitz plots were deduced. Sizeable pp FSI effects were found as were contributions of p and d partial waves. In comparison with existing literature data the results provide a sensitive test of the spectator model. The
behavior of the elementary cross-section σ01 close to threshold is discussed in view of new cross-section data. 相似文献
10.
T. Otsuka Y. Utsuno R. Fujimoto B.A. Brown M. Honma T. Mizusaki 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):69-74
Two recent developments of the nuclear shell model are presented. One is a breakthrough in computational feasibility owing
to the Monte Carlo Shell Model (MCSM). By the MCSM, the structure of low-lying states can be studied with realistic interactions
for a wide, nearly unlimited basically, variety of nuclei. The magic numbers are the key concept of the shell model, and are
shown to be different in exotic nuclei from those of stable nuclei. Its novel origin and robustness will be discussed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
11.
T. Otsuka Y. Utsuno R. Fujimoto B.A. Brown M. Honma T. Mizusaki 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):151-155
Two recent developments of the nuclear shell model are presented. One is a breakthrough in computational feasibility owing
to the Monte Carlo Shell Model (MCSM). By the MCSM, the structure of low-lying states can be studied with realistic interactions
for a wide, nearly unlimited basically, variety of nuclei. The magic numbers are the key concept of the shell model, and are
shown to be different in exotic nuclei from those of stable nuclei. Its novel origin and robustness will be discussed.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: otsuka@phys.s.u-tokyo.ac.jp 相似文献
12.
H. Rohdjeß M. Altmeier F. Bauer J. Bisplinghoff R. Bollmann K. Büßer M. Busch O. Diehl F. Dohrmann H. P. Engelhardt J. Ernst P. D. Eversheim K. O. Eyser O. Felden R. Gebel A. Groß R. Groß-Hardt F. Hinterberger R. Langkau J. Lindlein R. Maier F. Mosel D. Prasuhn P. von Rossen N. Scheid M. Schulz-Rojahn F. Schwandt V. Schwarz W. Scobel H. -J. Trelle K. Ulbrich E. Weise A. Wellinghausen K. Woller R. Ziegler 《The European Physical Journal A - Hadrons and Nuclei》2006,28(1):115-124
Recently published excitation functions in proton-proton (pp) elastic scattering observables in the laboratory energy range 0.5-2.5GeV provide an excellent data base to establish firm
upper limits on the elasticities ηel = Γel/Γtot of possible isovector resonant contributions to the nucleon-nucleon (NN) system. Such contributions have been predicted to arise from dibaryonic states, with c.m. masses between 2.1-2.9GeV/c2, but have not been confirmed experimentally. A method to determine quantitatively the maximum value of ηel compatible with experimental data is presented. We use energy-dependent phase shift fits to the pp data base to model the non-resonant interaction. Based upon the differential cross-section data measured by the EDDA Collaboration
an unbiased statistical test is constructed to obtain upper limits on ηel, that exclude larger values with a 99% confidence level. Results in the c.m. mass range 2.05-2.85GeV/c2 and total widths of 10-100MeV/c2 in the partial waves 1S0, 1D2, 3P0, 3P1, and 3F3 are presented and discussed. 相似文献
13.
G. Chanfray D. Davesne M. Ericson M. Martini 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):191-198
We study the two-pion propagator in the nuclear medium. This quantity appears in the ππ T-matrix and we show that it also enters the QCD scalar susceptibility. The medium effects on this propagator are due to the
influence of the individual nucleon response to a scalar field through their pion clouds. This response is appreciably increased
by the nuclear environment. It produces an important convergence effect between the scalar and pseudoscalar susceptibilities,
reflecting the reshaping of the scalar strength observed in 2π production experiments. While a large modifications of the
σ propagator follows, due to its coupling to two pion states, we show that the NN potential remains instead unaffected. 相似文献
14.
We address the question whether the cut-off dependence, which has to be introduced in order to properly define the Lippmann-Schwinger
equation for the one-pion exchange potential plus local (δ-function) potentials, can be removed (up to inverse powers of it)
by a suitable tuning of the various (bare) coupling constants. We prove that this is indeed so both for the spin singlet and
for the spin triplet channels. However, the latter requires, in the limit when the cut-off is taken to infinity, such a strong
cut-off dependence of the coupling constant associated to the non-local term which breaks orbital angular momentum conservation,
that the renormalized amplitude lacks from partial-wave mixing. We argue that this is an indication that this term must be
treated perturbatively.
Received: 7 October 2002 / Accepted: 15 January 2003 / Published online: 5 May 2003 相似文献
15.
16.
General expressions, including the lepton mass, for the spin-averaged differential cross-section for the annihilation reaction
lepton-antilepton to proton-antiproton are given, as well as general formulae for the single- and double-spin asymmetries
in the centre-of-mass frame. In particular, we discuss the single-spin asymmetry, normal to the scattering plane, which measures
the relative phase difference between nucleon electromagnetic form factors GE and GM. Recent experimental investigations of these form factors in the space- and time-like region are reviewed. It is thought
that measurements of the phase of these form factors will provide fundamental information on the internal nucleon structure.
The phases between GE and GM are accessible through polarisation observables measured in the antiproton-proton-to-lepton-antilepton reaction, or in its
time-reversed process. 相似文献
17.
Excitation functions of the analyzing power in elastic proton-proton scattering from 0.45 to 2.5 GeV
M. Altmeier F. Bauer J. Bisplinghoff K. Büßer M. Busch T. Colberg L. Demirörs H. P. Engelhardt P. D. Eversheim K. O. Eyser O. Felden R. Gebel M. Glende J. Greiff F. Hinterberger E. Jonas H. Krause T. Lindemann J. Lindlein B. Lorentz R. Maier R. Maschuw A. Meinerzhagen D. Prasuhn H. Rohdjeß D. Rosendaal P. von Rossen N. Schirm V. Schwarz W. Scobel H. -J. Trelle K. Ulbrich E. Weise A. Wellinghausen R. Ziegler 《The European Physical Journal A - Hadrons and Nuclei》2005,23(2):351-364
Excitation functions AN(plab,c.m.) of the analyzing power in elastic proton-proton scattering have been measured in an internal target experiment at the Cooler Synchrotron COSY with an unpolarized proton beam and a polarized atomic hydrogen target. Data were taken continuously during the acceleration and deceleration for proton kinetic energies Tlab (momenta plab) between 0.45 and 2.5 GeV (1.0 and 3.3 GeV/c) and scattering angles 30 ° c.m. 90°. The results provide excitation functions and angular distributions of high precision and internal consistency. The data can be used as calibration standard between 0.45 and 2.5 GeV. They have significant impact on phase shift solutions, in particular on the spin triplet phase shifts between 1.0 and 1.8 GeV. 相似文献
18.
Within the Nuclear Nambu-Jona-Lasinio model of light nuclei (the NNJL model), describing strong low-energy nuclear interactions, we compute the width of the energy level of the ground state of pionic deuterium. The theoretical value fits well the experimental data. Using the cross-sections for the reactions e + d p + p + e- and e + d p + n + e, computed in the NNJL model, and the experimental values of the events of these reactions, detected by the SNO Collaboration, we compute the boron neutrino fluxes. The theoretical values agree well with the experimental data and the theoretical predictions within the Standard Solar Model by Bahcall. We argue the applicability of the constraints on the astrophysical factor for the solar proton burning, imposed by helioseismology, to the width of the energy level of the ground state of pionic deuterium. We show that the experimental data on the width satisfy these constraints. This testifies an indirect measurement of the recommended value of the astrophysical factor for the solar proton burning in terrestrial laboratories in terms of the width of the energy level of the ground state of pionic deuterium. 相似文献
19.
R. Ortega D. d'Enterria G. Martınez D. Baiborodin H. Delagrange J. Dıaz F. Fernández H. Löhner T. Matulewicz R. W. Ostendorf S. Schadmand Y. Schutz P. Tlusty R. Turrisi V. Wagner H. W. Wilschut N. Yahlali 《The European Physical Journal A - Hadrons and Nuclei》2006,28(2):161-171
Measured hard-photon multiplicities from second-chance nucleon-nucleon collisions are used in combination with a kinetic thermal
model to estimate the breakup times of excited nuclear systems produced in nucleus-nucleus reactions at intermediate energies.
The obtained nuclear breakup time for the 129Xe + natSn reaction at 50 A MeV is Δτ ≈ 100-300 fm/c for all reaction centralities. The lifetime of the radiating sources produced in seven other different heavy-ion reactions
studied by the TAPS experiment is consistent with Δτ ≈ 100 fm/c, such relatively long thermal photon emission times do not seemingly support the interpretation of nuclear breakup as due
to a fast spinodal process for the heavy nuclear systems studied. 相似文献
20.
B. Borasoy E. Epelbaum H. Krebs D. Lee U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):357-367
We discuss lattice simulations of the ground state of dilute neutron matter at next-to-leading order in chiral effective field
theory. In a previous paper the coefficients of the next-to-leading-order lattice action were determined by matching nucleon-nucleon
scattering data for momenta up to the pion mass. Here the same lattice action is used to simulate the ground state of up to
12 neutrons in a periodic cube using Monte Carlo simulations. We explore the density range from 2% to 8% of normal nuclear
density and analyze the ground-state energy as an expansion about the unitarity limit with corrections due to finite scattering
length, effective range, and P -wave interactions. 相似文献