共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Haidenbauer 《The European Physical Journal A - Hadrons and Nuclei》2007,33(3):287-290
We present a new model for the hyperon-nucleon (ΛN , ΣN interaction, derived within the meson exchange framework. The model incorporates the standard one-boson exchanges of the
lowest pseudoscalar and vector meson multiplets with coupling constants fixed by SU(6) flavor symmetry relations. As a new feature, the contribution in the scalar-isoscalar (σ sector is derived from a microscopic
model of correlated ππ and Kˉ exchange. The same model is also used to constrain the interaction resulting from the vector-isovector (ρ exchange channel.
Additional short-ranged ingredients of the model in the scalar-isovector (a0) and scalar-isospin-1/2 (κ channels are likewise viewed as arising from meson-meson correlations but are treated phenomenologically.
With this model a satisfactory reproduction of the available hyperon-nucleon data is achieved. 相似文献
2.
Yu.S. Surovtsev D. Krupa M. Nagy 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):409-416
In a combined analysis of the experimental data on the coupled processes ππ↦ππ, KˉK in the channel with I
G
J
PC = 0+0+ +, the various scenarios of these reactions (with different numbers of resonances) are considered. In a model-independent approach,
based only on analyticity and unitarity, a resonance is represented by a pole cluster (poles on the Riemann surface) of the
definite type that is defined by the state nature. The best scenario contains the resonances f
0(665) (with properties of the σ-meson), f
0(980) (with a dominant sˉs component), f
0(1500) (with a dominant flavour-singlet, e.g., glueball component) and the f
0(1710) (with a considerable sˉs component). If the f
0(1370) exists, it has a dominant sˉs component. The coupling constants of the observed states with the considered channels and the ππ and KˉK scattering lengths are obtained. The conclusion on the linear realization of chiral symmetry is drawn.
Received: 25 April 2002 / Accepted: 4 June 2002 / Published online: 26 November 2002
RID="a"
ID="a"e-mail: surovcev@thsun1.jinr.ru
RID="b"
ID="b"e-mail: krupa@savba.sk
RID="c"
ID="c"e-mail: fyzinami@nic.savba.sk
Communicated by V.V. Anisovich 相似文献
3.
We analyse the exclusive channel pˉ↦γπ0, assuming handbag dominance. The soft parts are parametrized in terms of CGLN amplitudes for the qˉ↦γπ0 transition and form factors for the pˉ↦qˉ ones; the latter represent moments of Generalized Distribution Amplitudes. We present a combined fit to Fermilab data from
E760 taking simultaneously into account information from other exclusive reactions, especially from pˉ↦γγ data. Overall a nicely consistent picture emerges, such that one can hope, that our theoretical analysis will be reliable
also for the kinematics of GSI/FAIR, which, hopefully, will provide much more precise and complete data. Consequently, data
from this facility should improve our knowledge both on the proton-antiproton distribution amplitudes and the pion production
mechanism. 相似文献
4.
It is shown that the list of unusual mesons that are planned to be studied in photoproduction reactions can be supplemented
with I
G (J
PC)=2+ (2++) exotic states X
±(1600), which are natural to seek as manifestations of the ρ±ρ0 decay channels in the reactions γN → ρ±ρ0
N and γN → ρ±ρ0Δ. A classification of the ρ±ρ0 states according to their quantum numbers is presented. A model for the spin structure of the amplitudes for the reactions
γp → f
2(1270)p, γp → a
2
0
(1320)p, and γN → X
±(N, Δ) is proposed, and estimates are obtained for the corresponding cross sections. At E
γ≈6 GeV, it is found that σ(γP → f
2(1270)p)≈0.12 μb, σ(γp → a
2
0
(1320)p)≈0.25 μb, σ(γN → X
±
N → ρ±ρ0
N) ≈ 0.018 μb, and σ(γp → X
−Δ++ → ρ−ρ0Δ++≈0.031 μb. The problem of isolating signals from X
± states against the natural background that is associated with other channels of π±π0π+π− production is discussed. It is deduced that searches for exotic states X
±(2+ (2++)) in experiments at JLAB will be quite efficient—for example, the yield of about 2.8×106 events per month is expected to correspond to the estimated cross sections for the reactions γN → X
±
N → ρ±ρ0
N.
__________
Translated from Yadernaya Fizika, Vol. 63, No. 10, 2000, pp. 1904–1912.
Original Russian Text Copyright ? 2000 by Achasov, Shestakov. 相似文献
5.
S.V. Golovkin A.P. Kozhevnikov V.P. Kubarovsky V.F. Kurshetsov L.G. Landsberg V.V. Molchanov V.A. Mukhin S.V. Petrenko V.A. Senko D.V. Vavilov V.A. Victorov V.Z. Kolganov G.S. Lomkatsi A.F. Nilov V.T. Smolyankin 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):409-416
New data for the diffractive reaction p+N→ [Σ0
K
+] +N at E
p= 70 GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous
study of this reaction. In the mass spectrum M(Σ0
K
+) a structure at the threshold region with a mass ∼1810 MeV and a distinct X(2000) peak with M= 1989 ± 6 MeV and γ= 91 ± 20 MeV are observed. Unusual features of the massive X(2000) state (narrow decay width, anomalously
large branching ratio for the decay channel with strange particle emission) make it a serious candidate for cryptoexotic pentaquark
baryon with hidden strangeness |qqqsˉs>. We also present new results on the narrow threshold structure X(1810) with M= 1807 ± 7 MeV and γ= 62 ± 19 MeV which is produced in the region of very small P
2
T < 0.01 GeV2. The possibility of the Coulomb production mechanism for X(1810) is discussed.
Received: 28 April 1999 相似文献
6.
A. Dzyuba V. Kleber M. Büscher V. P. Chernyshev S. Dymov P. Fedorets V. Grishina C. Hanhart M. Hartmann V. Hejny L. Kondratyuk V. Koptev P. Kulessa Y. Maeda T. Mersmann S. Mikirtychyants M. Nekipelov D. Prasuhn R. Schleichert A. Sibirtsev H. J. Stein H. Ströher I. Zychor 《The European Physical Journal A - Hadrons and Nuclei》2006,29(2):245-251
The reaction pp → dK
+ˉ has been investigated at excess energies Q = 47.4 and 104.7MeV above the K
+ˉ threshold at COSY Jülich. Coincident dK+ pairs were detected with the ANKE spectrometer, and subsequently ∼ 2000 events with a missing ˉ invariant mass were identified,
which fully populate the Dalitz plot. The joint analysis of invariant mass and angular distributions reveals s-wave dominance between the two kaons, in conjunction with a p-wave between the deuteron and the kaon pair, i.e.
Kˉ production via the a
0
+(980) channel. Integration of the differential distributions yields total cross-sections of σ(pp → dK
+ˉ) = (38±2stat±14syst)nb and (190±4stat±39syst)nb for the low and high Q value, respectively. 相似文献
7.
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
8.
Antiproton proton annihilation reactions allow unique access to the moduli and phases of nucleon electromagnetic form factors
in the time-like region. We present the helicity amplitudes for the unequal-mass single-photon reaction pˉ → l
+
l
- in the s channel including the lepton mass. The relative signs of these amplitudes are determined using simple invariance properties.
Helicity amplitudes for one-photon exchange annihilation reaction pˉ → Bˉ are also given, where B is any spin-one-half particle with structure. Crossing relations between the ep → ep scattering and the pˉ → l
+
l
- annihilation channels are discussed and the crossing matrix for the helicity amplitudes is given. This matrix may be used
to verify known expressions for the space-like helicity amplitudes due to one-photon exchange. 相似文献
9.
On the basis of the experimental data on diffractive processes in πp, pp and pˉp collisions at intermediate, moderately high and high energies, we restore the scattering amplitude related to the t-channel exchange by vacuum quantum numbers by taking account of the diffractive s-channel rescatterings. At intermediate and moderately high energies, the t-channel exchange amplitude turns, with a good accuracy, into an effective pomeron which renders the results of the additive
quark model. At superhigh energies the scattering amplitude provides a Froissart-type behaviour, with an asymptotic universality
of cross sections such as σtot
πp/σtot
pp→ 1 at s→∞. The quark structure of hadrons being taken into account at the level of constituent quarks, the cross sections of pion
and proton (antiproton) in the impact parameter space of quarks, σπ(r
1⊥, r
2⊥; s) and σp(r
1⊥, r
2⊥, r
3⊥; s), are found as functions of s. These cross sections implicate the phenomenon of colour screening: they tend to zero at |r
i⊥−r
k⊥|→ 0. The effective colour screening radius for pion (proton) is found for different s. The predictions for the diffractive cross sections at superhigh energies are presented.
Received: 15 December 1998 相似文献
10.
M. Schumacher 《The European Physical Journal A - Hadrons and Nuclei》2006,30(2):413-422
The t-channel contribution to the difference of electromagnetic polarizabilities of the nucleon, (α - β)t, can be quantitatively understood in terms of a σ-meson pole in the complex t-plane of the invariant scattering amplitude A
1(s, t) with properties of the σ-meson as given by the quark-level Nambu-Jona-Lasinio model (NJL). Equivalently, this quantity may
be understood in terms of a cut in the complex t-plane where the properties of the σ-meson are taken from the ππ → σ → ππ, γγ → σ → ππ and Nˉ → σ → ππ reactions. This equivalence may be understood as a sum rule where the properties of the σ-meson as predicted by
the NJL model are related to the f
0(600) particle observed in the three reactions. In the following, we describe details of the derivation of (α - β)t making use of predictions of the quark-level NJL model for the σ-meson mass.
An erratum to this article is available at . 相似文献
11.
M. N. Vinoslavskiĭ P. A. Belevskii A. V. Kravchenko 《Journal of Experimental and Theoretical Physics》2006,102(3):417-430
The self-organization of an electron-hole plasma (EHP) heated by an electric field in pure p-Ge samples at T = 77 K has been studied experimentally. The derived current-voltage characteristics (CVCs) and the distributions of the electric
field and IR emission of the hot carriers along the samples show that the segments of a steep rise or the S-shaped segments of the CVCs in samples with n-p junctions are related to the formation of longitudinal thermal-diffusion autosolitons (AS‖); as a result, thin (d = 2–20 μm in diameter), melted-through current channels appear. Such AS‖ are formed at high EHP densities (n ≥ 1 × 1016 cm−3), when the electron-hole scattering is dominant, and at electron temperatures T
e
= (2–4.5)T
0 (T
0 is the lattice temperature). The saturation segments and the N-shaped segments in the CVCs are attributable to the generation of transverse thermal-diffusion high-field autosolitons (AS⊥) in the form of narrow strata with electric field strengths
= 1–20 kV cm−1. High-field AS⊥ are formed at EHP densities n = 5 × 1013−1 × 1016 cm−3, when the electron-phonon scattering is dominant, and at electron temperatures T
e
∼ Θ ≥ 5T
0 (Θ is the Debye temperature). The generated longitudinal and transverse autosolitons have high temperatures (T
e
≥ 1000 K) and reduced carrier densities and can exist simultaneously in different parts of the sample.
Original Russian Text ? M.N. Vinoslavskiĭ, P.A. Belevskii, A.V. Kravchenko, 2006, published in Zhurnal éksperimental’noĭ i
Teoreticheskoĭ Fiziki, 2006, Vol. 129, No. 3, pp. 477–492. 相似文献
12.
We calculate target fragmentation in pp→nX and γp→nX reactions in the meson cloud picture of the nucleon. The pp→nX reaction is used to fix the pnπ+ form factor for three different models. We take into account the possible destruction of the residual neutron by the projectile.
Using the form factor from the hadronic reaction we calculate photoproduction and small x
Bj electroproduction of forward neutrons at HERA. Here the qˉq dipoles in the photon can rescatter on the residual neutron. In photoproduction we observe slightly less absorption than
in the hadronic reaction. For deep inelastic events (Q
2 > 10 GeV2) screening is weaker but still present at large Q
2. The signature for this absorptive rescattering is a shift of the dσ/dEn distribution to higher neutron energies for photofragmentation.
Received: 12 June 1999 / Revised version: 12 October 1999 相似文献
13.
L. Roca C. Hanhart E. Oset U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2006,27(3):373-380
The Λ(1520)-resonance has been recently studied in a unitarized coupled-channel formalism with πΣ(1385), KΞ(1530), ˉN and πΣ as constituents blocks. We provide a theoretical study of the predictions of this model in physical observables of
the pp → pK+K-p and pp → pK+π0π0Λ reactions. In particular, we show that the ratio between the π0π0Λ and K-p mass distributions can provide valuable information on the ratio of the couplings of the Λ(1520)-resonance to πΣ(1385) and
ˉN than the theory predicts. Calculations are done for energies which are accessible in an experimental facility like COSY at
Jülich or the developing CSR facility at Lanzhou. 相似文献
14.
A. A. Samokhvalov T. I. Arbuzova N. A. Viglin V. V. Osipov N. I. Solin S. V. Naumov V. G. Bamburov N. I. Lobachevskaya O. G. Reznitskikh 《Physics of the Solid State》1999,41(2):262-264
Mg1−x
CuxO solid solutions having an NaCl structure with 0⩽x⩽0.20 are synthesized and Cu-Mg1−x
CuxO structures are prepared for superconductivity studies. The magnetic susceptibility χ, electron paramagnetic resonance (EPR), and electrical conductivity of the solid solutions are studied at temperatures of
5–550 K. It is shown that χ
−1(T) obeys the Curie-Weiss law with a paramagnetic Curie temperature Θ close to zero and an effective magnetic moment μ
eff=1.9 μ
B, close to the 1.73 μ
B of a Cu2+ ion with spin S=1/2. The width ΔH of the EPR line depends weakly on temperature and increases as x is raised. The volume narrowing of the EPR linewidth ΔH is used to estimate the exchange interaction parameter, 3×10−4 eV. The g-factor is close to 2 and is temperature independent. The electrical conductivity of Mg1−x
CuxO at T=300 K is ≈10−11–10−12 Ω−1 cm−1 for x=0 and increases to 10−5–10−6 Ω−1 cm−1 for x=0.15–0.20. The conductivity is p-type. Magnetic shielding is observed in Cu-Mg1−x
CuxO structures with x=0.15 and 0.20. The possible connection of this phenomenon with interference superconductivity in the contact layer of the
structure is discussed.
Fiz. Tverd. Tela (St. Petersburg) 41, 293–296 (February 1999) 相似文献
15.
J. Haidenbauer G. Krein U. -G. Meißner A. Sibirtsev 《The European Physical Journal A - Hadrons and Nuclei》2007,33(1):107-117
We investigate the ˉN interaction at low energies using a meson exchange model supplemented with a short-distance contribution from one-gluon exchange.
The model is developed in close analogy to the meson-exchange KN interaction of the Jülich group utilizing SU(4) symmetry constraints. The main ingredients of the interaction are provided by vector meson (ρ , ω exchange and higher-order
box diagrams involving ˉ*
N , ˉΔ , and ˉ*Δ intermediate states. The short-range part is assumed to receive additional contributions from genuine quark-gluon processes.
The predicted cross-sections for ˉN for excess energies up to 150MeV are of the same order of magnitude as those for KN but with average values of around 20mb, roughly a factor two larger than for the latter system. It is found that the ω -exchange
plays a very important role. Its interference pattern with the ρ -exchange, which is basically fixed by the assumed SU(4) symmetry, clearly determines the qualitative features of the ˉN interaction --very similiar to what happens also for the KN system. 相似文献
16.
P. V. Fedorets M. Büscher V. P. Chernyshev S. N. Dymov V. Yu. Grishina C. Hanhart M. Hartmann V. Hejny V. Kleber H. R. Koch L. A. Kondratyuk V. P. Koptev A. E. Kudryavtsev P. Kulessa S. I. Merzliakov S. M. Mikirtychiants M. E. Nekipelov H. Ohm R. Schleichert H. Ströher V. E. Tarasov K. -H. Watzlawik I. Zychor 《Physics of Atomic Nuclei》2006,69(2):306-313
The reaction pp → dπ
+
η has been measured at a beam energy of T
p
= 2.65 GeV (p
p
= 3.46 GeV/c) using the ANKE spectrometer at COSY-Julich. The missing-mass distribution of the detected dπ
+ pairs exhibits a peak around the η mass on top of a strong background of multipion pp → dπ
+(nπ) events. The differential cross section d
4
σ/dΩd
dΩ
π
+
dp
d
dp
π
+ for the reaction pp → dπ
+
η has been determined model independently for two regions of phase space. Employing a dynamical model for the a
0
+
production allows one then to deduce a total cross section of σ(pp → da
0
+
→ dπ
+
η) = 1.1 ± 0.3stat ± 0.7syst μb for the production of π
+
η via the scalar a
0
+
(980) resonance and σ(pp → dπ
+
η) = 3.5 ± 0.3stat ± 1.0syst μb for the nonresonant production. Using the same model as for the interpretation of recent results from ANKE for the reaction
, the ratio of the total cross sections is
, which is in agreement with branching ratios in the literature.
The text was submitted by the authors in English. 相似文献
17.
O. G. Tchikilev S. A. Akimenko G. I. Britvich K. V. Datsko A. P. Filin A. V. Inyakin V. A. Khmelnikov A. S. Konstantinov I. Ya. Korolkov V. M. Leontiev V. P. Novikov V. F. Obraztsov V. A. Polyakov V. I. Romanovsky V. I. Shelikhov V. A. Uvarov O. P. Yushchenko V. N. Bolotov S. V. Laptev V. A. Duk A. Yu. Polyarush 《Physics of Atomic Nuclei》2007,70(1):29-34
Using data collected with the ISTRA+ spectrometer during the 2001 run of the U-70 proton synchrotron in Protvino, the first
observation of the radiative kaon decay K
− → μ−π0γν is reported. The ratio Br(K
μ3γ, 5 < E*γ < 30 MeV)/Br(K
μ3) is found to be [0.270 ± 0.029(stat.) ± 0.026(syst.)]% and the ratio Br(K
μ3γ, 30 < E*γ < 60 MeV)/Br(K
μ3) = [0.0448 ± 0.0068(stat.) ± 0.0099(syst.)]%. These ratios are consistent with the theoretical predictions 0.21 and 0.047%,
respectively. The measured angular distribution asymmetry for the region 5 < E*γ < 30 MeV, A(cos ϑ*μγ) = 0.093 ± 0.141, is two standard deviations away from the theoretical prediction of 0.354. The measured asymmetry in the
T-odd variable ξ = pγ · (pμ × pπ)/m
K
3
is −0.03 ± 0.13.
The text was submitted by the authors in English. 相似文献
18.
The mechanism of 1:1 dipolar complexation of some long-chain aliphatic alcohols with chlorobenzene and acetic acids in a non-polar
medium is studied. The interaction dipole moment △→μ, the excess molar polarization ΔP and apparent complex formation constantK
app are evaluated following two independent methods. It is observed from the value of △→μ that the complex formation is mostly due to polarization interaction and is of the same type as involving lower alcohols.
ΔP andK
app are, however, of different nature compared to those in lower alcohols suggesting that the unlike molecules form relatively
stable linear linkage resulting in antiparallel orientation prior to forming complexes. 相似文献
19.
O. B. Gusev M. S. Bresler B. P. Zakharchenya A. N. Kuznetsov P. E. Pak E. I. Terukov K. D. Tséndin I. N. Yassievich 《Physics of the Solid State》1999,41(2):185-191
A study of the electroluminescence of erbium-doped, amorphous hydrogenated silicon, a-Si:H 〈Er〉, is reported. It has been found that the electroluminescence intensity at the wavelength λ=1.54 μm corresponding to the 4
I
13/2→4
I
15/2 intra-4f shell transition in Er passes through a maximum near room temperature. The unusual temperature and field dependences of the
electroluminescence indicate electric-field induced multi-phonon tunneling emission of electrons from deep centers. The electroluminescence
of Er3+ ions is due to their becoming excited as conduction-band electrons are captured by neutral dangling bonds (D
0 centers), which form when erbium is incorporated into the amorphous matrix. This Auger process transforms the center from
its neutral state, D
0, to a negatively charged state, D
−, and the energy released in the capture is transferred by Coulomb interaction into the erbium-ion 4f shell. The steady-state current through the electroluminescent structure is supported by the reverse process of multi-phonon
tunneling-electron emission from the D
− center to the conduction band. The proposed theoretical model is in a good agreement with experimental data.
Fiz. Tverd. Tela (St. Petersburg) 41, 210–217 (February 1999) 相似文献
20.
The phase structure of the two-dimensional Gross-Neveu model in a spacetime of the form R
1×S
1 and in the presence of a chemical potential μ is investigated. The phase portrait of the model is constructed in the parameter
plane (μ, γ), where γ=1/L and L is the length of the circle S
1. In the portrait there exist two massive phases, with spontaneously broken chiral invariance, as well as infinitely many
massless symmetric phases. Such a vacuum structure leads to oscillations of the critical curve μ
c
(γ) of chiral phase transitions. In addition, the particle number density in the vacuum state of the model oscillates if μ<μ
c
(γl).
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 5, 431–436 (10 September 1998) 相似文献