共查询到20条相似文献,搜索用时 31 毫秒
1.
N. Kaiser 《The European Physical Journal A - Hadrons and Nuclei》2007,31(2):207-212
We calculate at two-loop order in chiral perturbation theory the electromagnetic corrections to the leading-order 2π exchange
NN interaction proportional to g
A
0 and g
A
2. The resulting 2πγ exchange potential contains isospin-breaking components which reach up to about -2% of the corresponding
isovector 2π exchange potential. With a value of only -17keV at r = m
π
-1 = 1.4fm the charge-independence breaking central potential obtained here is negligibly small in comparison to the one generated
by the isoscalar c3 contact vertex. Our calculation confirms that the largest long-range isospin-violating NN potentials arise from the 2πγ exchange diagrams involving the large low-energy constants c
4 ≃ - c
3 ≃ 3.3GeV^-1 representing the important Δ(1232) dynamics. 相似文献
2.
Sayipjamal Dulat Bing-Song Zou 《The European Physical Journal A - Hadrons and Nuclei》2005,26(1):125-134
With accumulation of high statistics data at BES and CLEO-c, many new interesting channels can get enough statistics for partial-wave
analysis (PWA). Among them, ψ↦γpˉ,γΛˉ,γΣˉ,γΞˉ channels provide a good place for studying baryon-antibaryon interactions; the double radiative decays ψ↦γγV with V ≡ ρ,ω,φ have a potential to provide information on the flavor content of any meson resonances (R) with positive charge parity
(C = +) and mass above 1 GeV through ψ↦γR↦γγV; ψ(2s)↦γχc0,1,2 with χc0,1,2↦Kˉπ+π- and 2π+2π- decays are good processes to study χcJ charmonium decays. Using the covariant tensor formalism, here we provide theoretical PWA formulae for these channels. 相似文献
3.
B. Kubis E.H. Müller J. Gasser M. Schmid 《The European Physical Journal C - Particles and Fields》2007,50(3):557-571
We re-investigate the radiative charged kaon decay K±→π0e±νeγ [Ke3γ
±] in chiral perturbation theory, merging the chiral expansion with Low’s theorem. We thoroughly analyze the precision of the
predicted branching ratio relative to the non-radiative decay channel. Structure dependent terms and their impact on differential
decay distributions are investigated in detail, and the possibility to see effects of the chiral anomaly in this decay channel
is emphasized.
PACS 13.20.Eb; 11.30.Rd; 12.39.Fe 相似文献
4.
H. Naik R.J. Singh R.H. Iyer 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):495-507
Charge distribution studies for heavy-mass fission products were carried out in the fast-neutron-induced fission of 232Th, 238U, 240Pu and 244Cm using radiochemical and gamma-ray spectrometric techniques. The width parameter( σZ/σA), the most probable charge/mass ( Z
P/A
P), the charge polarization (ΔZ) and the slope of charge polarization [ δ(ΔZ)/δA
′] as a function of the fragment mass (A
′) were deduced. The average charge dispersion parameter ( 〈σZ〉) and proton odd-even effect ( δp) were also obtained for these fissioning systems. The 〈σZ〉 and δp values in the fissioning systems 241Pu * and 245Cm * were determined for the first time. The δ(ΔZ)/δA
′ value is also determined for the first time in the fissioning systems 239U * , 241Pu * and 245Cm * . These data along with the literature data for even-Z fissioning systems such as 230Th * , 232Th * , 233U * , 234U * , 236U * , 238U * , 239Pu * , 240Pu*, 242Pu * , 246Cm * , 250Cf * and 252Cf(SF) are discussed in terms of nuclear structure effect and dynamics of descent from the saddle to the scission point. The
role of the excitation energy in low-energy fission is also discussed.
Received: 26 July 2002 / Accepted: 3 December 2002 / Published online: 3 April 2003
RID="a"
ID="a"Present address: Emeritus Scientist (CSIR) Bhabha Atomic Research Centre, Nuclear Recycle Group, WIP Building, Trombay, Mumbai-400085, India;
e-mail: rhiyer@magnum. barc.ernet.in
Communicated by D. Schwalm 相似文献
5.
A. A. Krutov A. P. Martynenko 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,62(2):163-175
On the basis of the perturbation theory in the fine structure constant α and the ratio of the electron to muon masses we calculate one-loop vacuum polarisation and electron vertex corrections and
the nuclear structure corrections to the hyperfine splitting of the ground state of the muonic helium atom (μ e
3
2He). We obtain total results for the ground state hyperfine splitting Δ
ν
hfs
= 4166.648 MHz which improves the previous calculation of Lakdawala and Mohr due to new corrections of orders α
5 and α
6. The remaining differences between our theoretical result and experimental value of the hyperfine splitting lie in the range
of theoretical and experimental errors and require the subsequent investigation of higher order corrections. 相似文献
6.
Doubly-charged scalars, predicted in many models having exotic Higgs rep-resentations, can in general have lepton-number violating
(LFV) couplings. We show that by using an associated monoenergetic final state photon seen at a future linear e
−
e
− collider, we can have a clear and distinct signature for a doubly-charged resonance. The strength of the ΔL = 2 coupling can also be probed quite effectively as a function of the recoil mass of the doubly-charged scalar.
相似文献
7.
G. Pancheri O. Shekhovtsova G. Venanzoni 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):458-460
Effects due to the non-pointlike behaviour of pions in the process e
+
e
-→π
+
π
-
γ can arise for hard photons in the final state. By means of a Monte Carlo event generator, which also includes the contribution
of the direct decay φ→π
+
π
-
γ, we estimate these effects in the framework of the resonance perturbation theory. We consider angular cuts used in the KLOE
analysis of the pion form factor at threshold. A method to reveal the effects of the non-pointlike behaviour of pions in a
model-independent way is proposed. 相似文献
8.
I. V. Glavanakov P. Grabmayr Yu. F. Krechetov A. N. Tabachenko 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):747-749
Experimental research on positive-pion photoproduction on the oxygen nucleus in the 16O(γ, π+p) reaction at high recoil momenta of the residual nuclear system was performed. The yield for the 16O(γ, π+p) reaction was analyzed using a model that takes Δ-isobar configurations in nuclei ground states into account, together with
the earlier-measured yield of the12C(γ, π+p) reaction. The estimated number of isobars per nucleon N
Δ = 0.012 ± 0.005 was obtained for the 12C nucleus, and 16O N
Δ = 0.018 ± 0.004 was obtained for the 16O nucleus. 相似文献
9.
V. Bernard B. Kubis U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2005,25(3):419-425
We analyze the Fubini-Furlan-Rosetti sum rule in the framework of covariant baryon chiral perturbation theory to leading one-loop
accuracy and including next-to-leading-order polynomial contributions. We discuss the relation between the subtraction constants
in the invariant amplitudes and certain low-energy constants employed in earlier chiral perturbation theory studies of threshold
neutral pion photoproduction off nucleons. In particular, we consider the corrections to the sum rule due to the finite pion
mass and show that below the threshold they agree well with determinations based on fixed-t dispersion relations. We also discuss the energy dependence of the electric dipole amplitude E0+. 相似文献
10.
We present the elastic scattering of the 6He+208Pb and the 6He+197Au systems at the laboratory energy of E
lab=27 MeV within the framework of the McIntyre parametrization, and systematically investigate χ
2/N analysis of both systems to obtain an excellent agreement between the theoretical results and the experimental data. We find
large diffusivity parameters indicating long range absorption mechanisms. We also show that both systems lack both the nuclear
and the Coulomb rainbow scattering for obtained S-matrix parameters. 相似文献
11.
A. V. Korolev M. I. Kurkin O. B. Sokolov N. B. Orlova 《Physics of the Solid State》2010,52(3):561-567
The dependences of the magnetization M and the magnetic susceptibility χ = ∂M/∂H of pure gadolinium (the concentration of foreign impurities is lower than 0.1 wt %) on the temperature T and the magnetic field H have been measured using a Quantum Design MPMS-5XL SQUID magnetometer. In this material, inhomogeneities of the atomic structure
should not lead to a nonuniform distribution of the magnetic characteristics (including the Curie temperature T
C) over the volume of the sample. The obtained dependences of M and χ have been used to investigate the possibility of suppressing magnetic inhomogeneities of other types by magnetic fields
with a strength of up to 50 kOe. It has been assumed that these inhomogeneities are suppressed when the specific relationship,
namely, the 21/3 rule is fulfilled. The rule relates the portions of the dependence χ(T, H) which at the temperature T = T
C and at the maximum in the curve χ(T) (T = T
m
) depend on H in accordance with the H
2/3 law. It has been shown that the portions separated from the experimental curves χ(T
C, H) and χ(T
m
, H) obey the 21/3 rule. 相似文献
12.
A. S. Kachan I. V. Kurguz I. S. Kovtunenko V. M. Mischenko V. A. Panin 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(11):1506-1510
The γ decay of the resonance-like structure observed in the 30Si(pγ)31P reaction in the energy range E
p = 1.4–2.7 MeV of accelerated protons has been investigated. The excitation function of this reaction and the spectra and
angular distributions of the γ rays formed in the decay of resonances with E
p = 1482, 2350, and 2505 keV have been measured. The M1 resonance on the ground and the first excited states of 31P with E
p = 1266 keV is identified. The total strength of the M1 resonance on the ground state of this nucleus is determined. The position and total strength of this resonance on the ground
state are explained taking into account pairing forces. 相似文献
13.
We discuss various aspects of resummed chiral perturbation theory, which was developed recently in order to consistently include
the possibility of large vacuum fluctuations of the s̄s pairs and the scenario with smaller value of the q̄q condensate for
Nf=3. The subtleties of this approach are illustrated using a concrete example of observables connected with πη scattering.
This process seems to be a suitable theoretical laboratory for this purpose due to its sensitivity to the values of the O(p4) LECs, namely to the values of the fluctuation parameters L4 and L6. We discuss several issues in detail, namely the choice of “good” observables and properties of their bare expansions, the
“safe” reparametrization in terms of physical observables, the implementation of exact perturbative unitarity and exact renormalization
scale independence, the role of higher order remainders and estimates of their influence. We make a detailed comparison with
standard chiral perturbation theory and use generalized χPT as well as resonance chiral theory to estimate the higher order
remainders. 相似文献
14.
E. N. Elekina A. A. Krutov A. P. Martynenko 《Physics of Particles and Nuclei Letters》2011,8(4):331-336
On the basis of quasi-potential approach to the bound state problem in QED we calculate the vacuum polarization, recoil and
structure corrections of orders α5 and α6 to the fine splitting interval ΔE
fs = E(2P
3/2) − E(2P
1/2) in muonic 24He ion. The resulting value ΔE
fs = 146180.68 μeV provides reliable guideline in performing a comparison with the relevant experimental data. 相似文献
15.
The concept of ‘D-Differentiation’, which, in the context of smooth manifolds, generalises Lie and covariant differentiation, is extended to
R
∞ -supermanifolds under the name of ‘Super D-Differentiation’. This is done by defining new (non-linear) mappings, called ‘μ-mappings’ and by relating their non-linearity to the Leibniz rule that a derivation must satisfy when it acts on a tensor
product. The resulting axiomatics, which is basis-independent and coordinate-free, is then expressed in a general basis (not
necessarily holonomic). Super Lie and Super covariant differentiation are, amongst others, special cases of Super D-Differentiation. In particular, the transformation rules for the connection coefficients and the commutation coefficients
of non-holonomic bases are obtained. These special cases are found to be in agreement with the DeWitt Super covariant and
Super Lie derivatives.
相似文献
16.
A. Sibirtsev J. Haidenbauer H. -W. Hammer U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2007,32(2):229-241
We utilize existing inclusive data on K+-meson momentum spectra of the reaction pp→K
+
X at T
p = 2.3-2.85GeV to deduce total cross-sections for pp→K
+
Σ
+
n. The method used to extract those cross-sections is explained and discussed in detail. Our result for T
p = 2.85GeV is consistent with the data point from a direct measurement at the same beam energy. The cross-section obtained
for T
p = 2.3GeV is with 13.7±2.3μb considerably smaller than the value found in a recent experiment by the COSY-11 Collaboration
at a somewhat lower beam energy, indicating that the pp→K
+
Σ
+
n reaction cross-section could exhibit a rather unusual energy dependence. 相似文献
17.
On the basis of quasipotential approach to the bound state problem in QED we calculate the vacuum polarization, relativistic,
recoil, structure corrections of orders α
5 and α
6 to the fine structure interval ΔE
fs = E(2P
3/2) − E(2P
1/2) and to the hyperfine structure of the energy levels 2P
1/2 and 2P
3/2 in muonic 23He ion. The resulting values ΔE
fs = 144 803.15 μeV, Δ$
\tilde E
$
\tilde E
hfs(2P
1/2) = −58 712.90 μeV, Δ$
\tilde E
$
\tilde E
hfs(2P
3/2) = −24 290.69 μeV provide reliable guidelines in performing a comparison with the relevant experimental data. 相似文献
18.
Observables of the elastic and inelastic scattering of 800- and 250-MeV protons on 20Ne and 24Mg nuclei were calculated on the basis of the theory of multiple diffractive scattering and the dispersive α-cluster model. The 20Ne and 24Mg nuclei were assumed to consist of a core (16O nucleus) and additional alpha-particle clusters, which could be situated with the highest probability both in the vicinity
of the center of mass of the core and outside the core. The multiparticle densities of these nuclei and single-particle nucleon-distribution
densities as obtained from the dispersive α-cluster model were used in the calculations. The differential cross sections and polarizations for elastic and inelastic
p
20Ne and p
24Mg scattering at the energy of 800 MeV are in better agreement with experimental data than the analogous calculations at the
energy of 250 MeV. The spin-rotation functions calculated in the singleparticle approximation for elastic p
20Ne and p
24Mg scattering at these two energy values differ qualitatively from their counterparts calculated on the basis of the dispersive
α-cluster model. 相似文献
19.
A. Yu. Mollaev I. K. Kamilov R. K. Arslanov T. R. Arslanov U. Z. Zalibekov V. M. Novotortsev S. F. Marenkin 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1107-1108
The dependences of the longitudinal magnetoresistance (Δρ
zz
/ρ0)(P), transverse magnetoresistance (Δρ
xx
/ρ0)(P), and magnetic susceptibility (χ/χ0(P)) on hydrostatic pressure P ≤ 7 GPa in the ferromagnetic semiconductor Cd0.7Mn0.3GeAs2 at room temperature were investigated. 相似文献
20.
Yu. V. Orlov L. I. Nikitina 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(4):446-449
We find the vertex constant for the synthesis α + α → 8Be and the corresponding asymptotic normalization coefficient of the Gamov wave function for 8Be in the ground state. We use modern data on the position and width of the narrow resonance of this state as well as the
energy dependence of the αα scattering phase shift in the s-wave known from the literature. The effective-range theory was applied with the Coulomb interaction taken into account. The
parameters of the standard effective-range function expansion up to the member with k
4 (k being the relative momentum) were found. 相似文献