共查询到20条相似文献,搜索用时 31 毫秒
1.
Yu. A. Simonov 《JETP Letters》2008,87(3):121-123
The dipion spectrum for the ϒ(nS) → ϒ(n′S) transition with n < 4 has the form dw/dq ∼ (phase space) |η − x|2, with x = q
2 − 4m
π2 / (ΔM)2 − 4m
π2 < q
2 ≡ M
ππ2, and ΔM = M(nS) − M(n′S). The parameter η is calculated and the spectrum is shown to reproduce the experimental data for all three types of decays:
3 → 1, 2 → 1, and 3 → 2 with η ≈ 0.5, 0, and −3, respectively.
The text was submitted by the author in English. 相似文献
2.
We point out that the equivalent-photon approximation (EPA) for processes with massive spin-1 particles in the final state would have validity in a more restricted kinematic domain
than for processes where it is commonly applied, viz., those with spin-1/2 or spin-0 particles in the final state. We obtain
the criterion for the validity ofEPA for the two-photon production of a pair of charged, massive, point-like spin-1 particlesV
±, each of massM and with a standard magnetic moment (κ=1). In a process in which one of the photons is real and the other virtual with four-momentumq, the condition for the validity ofEPA is |q
2|≪M
2, in addition to the usual condition |q
2|≪W
2,W being theV
+
V
− invariant mass. In a process in which both photons are virtual (with four-momentaq andq′), our condition is |q
2||q′2|W
4 ≪ 16M
8, in addition to |q
2| ≪M
2, |q′2| ≪M
2 and |q
2| ≪W
2, |q′2| ≪W
2. Even when these extra conditions permitting the use ofEPA are not fulfilled, convenient approximate expressions may still be obtained assuming merely |q
2| ≪W
2 and |q′2| ≪W
2.
We also discuss how the extra conditions are altered when the vector bosons are incorporated in a spontaneously broken gauge
theory. Examples ofW boson production in Weinberg-Salam model are considered for which the condition |q
2||q′2|W
4 ≪ 16M
8 is shown to be removed. 相似文献
3.
L. G. Moyano A. P. Majtey C. Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(4):493-500
We introduce, and numerically study, a system of N symplectically and globally coupled
standard maps localized in a d=1 lattice array. The global coupling is modulated
through a factor r-α, being
r the distance between maps. Thus, interactions are long-range (nonintegrable) when
0≤α≤1, and short-range (integrable) when α>1.
We verify that the largest Lyapunov exponent λM scales as λM ∝
N-κ(α), where κ(α) is positive when interactions are
long-range, yielding weak chaos in the thermodynamic
limit N↦∞ (hence λM→0). In the short-range case,
κ(α) appears to vanish,
and the behaviour corresponds to strong chaos. We show that, for certain
values of the control parameters of the system, long-lasting metastable states
can be present. Their duration tc scales as tc ∝Nβ(α),
where β(α) appears to be numerically in agreement with the following
behavior: β>0 for 0 ≤α< 1, and zero for α≥1.
These results are consistent with features typically found in nonextensive statistical mechanics.
Moreover, they exhibit strong similarity between the present
discrete-time system, and the α-XY Hamiltonian ferromagnetic model. 相似文献
4.
Yu Zhang 《Journal of statistical physics》2012,146(2):466-473
We consider bond percolation on the Z
d
lattice. Let M
n
be the number of open clusters in B(n)=[−n,n]
d
. It is well known that E
p
M
n
/(2n+1)
d
converges to the free energy function κ(p) at the zero field. In this paper, we show that s2p(Mn)/(2n+1)d\sigma^{2}_{p}(M_{n})/(2n+1)^{d} converges to −p(1−p)κ′(p). 相似文献
5.
S. Shlomo 《Physics of Atomic Nuclei》2010,73(8):1390-1397
We discuss a method of determining a modern energy density functional (EDF) in nuclei. We adopt a Skyrme type EDF and fit
the Skyrme parameters to an extensive set of experimental data on the ground-state binding energies, radii, and the breathing
mode energies of a wide range of nuclei. We further constrain the values of the Skyrme parameters by requiring positive values
for the slope of the symmetry energy S, the enhancement factor κ, associated with the isovector giant dipole resonance, and the Landau parameter G
0′. This is done within the approaches of Hartree-Fock (HF) and HF with the inclusion of correlation effects, using a simulated-annealing
based algorithm forminimizing χ
2.We also present results of HF based random phase approximation for the excitation strength function of the breathing mode
and discuss the current status of the nuclear matter incompressibility coefficient. 相似文献
6.
E.G. Drukarev M.G. Ryskin V.A. Sadovnikova 《The European Physical Journal A - Hadrons and Nuclei》1999,4(2):171-186
We calculate the contribution of pions to the $\bar qq$-expectation value κ(ρ) =<M|ˉq
q|M> in symmetric nuclear matter. We employ exact pion propagator renormalized by nucleon-hole and isobar-hole excitations. Conventional
straightforward calculation leads to the “pion condensation” at unrealistically small values of densities, causing even earlier
restoration of chiral symmetry. This requires a self-consistent approach, consisting in using the models, which include direct
dependence of in-medium mass values on κ(ρ), e.g. the Nambu–Jona-Lasinio–model. We show, that in the self-consistent approach
the ρ-dependence of the condensate is described by a smooth curve. The “pion condensate” point is removed to much higher values
of density. The chiral restoration does not take place at least while ρ < 2.8ρ0 with ρ0 being the saturation value. Validity of our approach is limited by possible accumulation of heavier baryons (delta isobars)
in the ground state of nuclear matter. For the value of effective nucleon mass at the saturation density we found m
*(ρ0) = 0.6m, consistent with nowadays results of other authors.
Received: 8 October 1998 相似文献
7.
José F. Cari?ena Manuel F. Ra?ada Mariano Santander 《International Journal of Theoretical Physics》2011,50(7):2170-2178
A nonlinear model representing the quantum harmonic oscillator on the three-dimensional spherical and hyperbolic spaces, Sk3S_{\kappa }^{3} (κ>0) and Hk3H_{k}^{3} (κ<0), is studied using geodesic spherical coordinates (r,θ,φ). The curvature κ is considered as a parameter and the results are formulated in explicit dependence of κ. The first part of the paper is concerned with the existence of Killing vectors, the existence of Noether symmetries and
the properties of the Noether momenta. The second part is devoted to the transition from classical to quantum mechanics. The
classical system is quantized by obtaining a κ-dependent invariant measure dμ
κ
and expressing the Hamiltonian as a function of the Noether momenta. 相似文献
8.
A possible minimal model of the gauge–Higgs unification based on the higher dimensional spacetime M
4⊗(S
1/Z
2) and the bulk gauge symmetry SU(3)
C
⊗SU(3)
W
⊗U(1)
X
is constructed in some detail. We argue that the Weinberg angle and the electromagnetic current can be correctly identified
if one introduces the extra U(1)
X
above and a bulk scalar triplet. The VEV of this scalar as well as the orbifold boundary conditions will break the bulk gauge
symmetry down to that of the standard model. A new neutral zero-mode gauge boson Z′ exists that gains mass via this VEV. We propose a simple fermion content that is free from all the anomalies when the extra
brane-localized chiral fermions are taken into account as well. The issues on recovering a standard model chiral-fermion spectrum
with the masses and flavor mixing are also discussed, where we need to introduce the two other brane scalars which also contribute
to the Z′ mass in the similar way as the scalar triplet. The neutrinos can get small masses via a type I seesaw mechanism. In this
model, the mass of the Z′ boson and the compactification scale are very constrained being, respectively, given in the ranges: 2.7 TeV<m
Z′<13.6 TeV and 40 TeV<1/R<200 TeV. 相似文献
9.
We construct the supersymmetric economical 3-3-1 model which contains inflationary scenario and avoids the monopole puzzle.
Based on the spontaneous symmetry breaking pattern (with three steps), the F-term inflation is derived. The slow-roll parameters ∈ and η are calculated. By imposing as experimental five-year WMAP data on the spectral index n, we have derived a constraint on the number of e-folding N
Q
to be in the range from 25 to 50. The scenario for large-scale structure formation implied by the model is a mixed scenario
for inflation and cosmic string, and the contribution to the CMBR temperature anisotropy depends on the ratio M
X
/M
Pl. From the COBE data, we have obtained the constraint on the M
X
to be M
X
∈ [1.22 × 1016, 0.98 × 1017] GeV. The upper value M
X
≃ 1017 GeV is a result of the analysis in which the inflationary contribution to the temperature fluctuations measured by the COBE
is 90%. The coupling α varies in the range: 10−7−10−1. This value is not so small, and it is a common characteristics of the supersymmetric unified models with the inflationary
scenario. The spectral index n is a little bit smaller than 0.98. The SUGRA corrections are slightly different from the previous consideration. When ξ ≪ 1 and α lies in the above range, the spectral index gets the value consistent with the experimental five-year WMAP data. Comparing
with string theory, one gets ξ < 10−8. Numerical analysis shows that α ≈ 10−6. To get inflation contribution to the CMBR temperature anisotropy ≈90%, the mass scale M
X
< 3.5 × 1014 GeV. 相似文献
10.
George W S Hou 《Pramana》2006,67(5):773-782
There are currently two hints for new physics involving CP violation in b → s transitions: ΔS ≡ S
f − S
J
ϕK
≠ 0, and difference in direct CP asymmetry ΔA
Kπ
≡ A
K+π
0
− A
K+π
−
≠ 0. We explore the two scenarios with a large and unique new CP phase in b ↔ s transitions. Motivated by ΔS ≠ 0, we update on the right-handed strange-beauty squark sb
1R at TeV scale. Motivated by ΔA
Kπ
≠ 0, we explore sequential fourth generation t′ and b′ quarks. Both scenarios can survive constraints such as SM level b → sγ, sll and B
s mixing, and predict sizable CP violation in B
s mixing. The fourth generation picture predicts sizable K
L → π
0
vv. Direct search for sb
R, b′ and t′ at hadronic colliders, such as Tevatron Run II and LHC, can complement further CP violation studies at these machines, as
well as at the future Super B factory. 相似文献
11.
We consider a large neutral molecule with total nuclear charge Z in non-relativistic quantum mechanics with a self-generated classical electromagnetic field. To ensure stability, we assume that Z α 2 ≤ κ 0 for a sufficiently small κ 0, where α denotes the fine structure constant. We show that, in the simultaneous limit Z → ∞, α → 0 such that κ = Z α 2 is fixed, the ground state energy of the system is given by a two term expansion c 1 Z 7/3 + c 2(κ) Z 2 + o(Z 2). The leading term is given by the non-magnetic Thomas-Fermi theory. Our result shows that the magnetic field affects only the second (so-called Scott) term in the expansion. 相似文献
12.
S. Descotes-Genon B. Moussallam 《The European Physical Journal C - Particles and Fields》2006,48(2):553-560
We discuss the existence of the light scalar meson K*
0(800) (also called κ) in a rigorous way, by showing the presence of a pole in the πK→πK amplitude on the second Riemann sheet. For this purpose, we study the domain of validity of two classes of Roy–Steiner representations in the complex energy plane. We prove that one of them is valid in a region sufficiently broad in the imaginary direction. From this representation, we compute the l=0 partial wave in the complex plane neither making any additional approximation nor having model dependence, relying only on experimental data. A scalar resonance with strangeness S=1 is found with the following mass and width: Mκ=658±13 MeV and Γκ=557±24 MeV. 相似文献
13.
A. A. Babich A. A. Pankov A. V. Tsytrinov N. V. Karpenko 《Physics of Atomic Nuclei》2010,73(5):773-784
The potential of the electron-positron International Linear Collider for searches for and the separation of signals induced
by new neutral gauge bosons predicted by various classes of models featuring an extended gauge sector is investigated. The
analysis presented in this article was performed for processes of annihilation fermion-pair production and was based on the
use of differential polarization observables, which ensure a higher sensitivity (in relation to integrated observables) of
the processes being considered to Z′-boson parameters. Thresholds for discovering and identifying new neutral gauge bosons associated with models belonging to
the E
6 and LR, as well as the ALR and SSM, classes are determined. In particular, it is shown that polarization experiments at a
0.5-TeV electron-positron collider of integrated luminosity 100 fb−1 would make it possible to identify unambiguously the entire set of Z′-boson models (Z′SSM, Z′
φ
, Z′
η
, Z′
χ
, Z′LRS, and Z′ALR) for M
Z′ < 6√s and to improve considerably the respective estimates expected from experiments with unpolarized particles. 相似文献
14.
N. Sh. Izmailian 《JETP Letters》1996,63(4):290-295
The spin-3/2 Ising model described by the most general Hamiltonian with up-down symmetry, −βH=Σ〈ij〉{JS
i
S
j
+KS
2
i
S
2
j
+LS
3
i
S
3
j
+M/2(S
i
S
3
j
+S
j
S
3
i
)}−ΔΣi
S
2
i
, is investigated on a square lattice. It is shown that this model is reducible to an eight-vertex model on a surface in the
parameter space spanned by the coupling constants J, K, L, and M. It is shown that this model is equivalent to an exactly solvable free fermion model along two lines in the parameter space.
Consequently, the critical behavior and, in particular, the critical temperature for the second-order phase transitions of
the model is found exactly.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 4, 270–275 (25 February 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
15.
Thomas Kerler 《Communications in Mathematical Physics》1998,198(3):535-590
We consider a generalization of the axioms of a TQFT, the so-called half-projective TQFT's, where we inserted an anomaly,
, in the composition law. Here μ0 is a coboundary (in a group cohomological sense) on the cobordism categories with non-negative, integer values. The element
of the ring over which the TQFT is defined does not have to be invertible. In particular, it may be zero.
This modification makes it possible to extend quantum-invariants, which vanish on S
1×S
2, to non-trivial TQFT's. Note, that a TQFT in the ordinary sense of Atiyah with this property has to be trivial all together.
We organize our discussions such that the notion of a half-projective TQFT is extracted as the only possible generalization
under a few very natural assumptions.
Based on separate work with Lyubashenko on connected TQFT's, we construct a large class of half-projective TQFT's with . Their invariants all vanish on S
1×S
2, and they coincide with the Hennings invariant for non-semisimple Hopf algebras and, more generally, with the Lyubashenko
invariant for non-semisimple categories.
We also develop a few topological tools that allow us to determine the cocycle μ0 and find numbers, ϱ(M), such that the linear map associated to a cobordism, M, is of the form . They are concerned with connectivity properties of cobordisms, as for example maximal non-separating surfaces. We introduce
in particular the notions of “interior” homotopy and homology groups,
and of coordinate graphs, which are functions on cobordisms with values in the morphisms of a graph category.
For applications we will prove that half-projective TQFT's with vanish on cobordisms with infinite interior homology, and we argue that the order of divergence of the TQFT on a cobordism,
M, in the “classical limit” can be estimated by the rank of its maximal free interior group, which coincides with ϱ(M).
Received: 20 October 1997 / Accepted: 18 March 1998 相似文献
16.
A. D. Martin W. J. Stirling R. S. Thorne G. Watt 《The European Physical Journal C - Particles and Fields》2009,64(4):653-680
We determine the uncertainty on the strong coupling α
S
due to the experimental errors on the data fitted in global analysis of hard-scattering data, within the standard framework
of leading-twist fixed-order collinear factorisation in the
[`(MS)]\overline{\mathrm{MS}}
scheme, finding that α
S
(M
Z
2)=0.1202−0.0015+0.0012 at next-to-leading order (NLO) and α
S
(M
Z
2)=0.1171−0.0014+0.0014 at next-to-next-to-leading order (NNLO). We do not address in detail the issue of the additional theory uncertainty on α
S
(M
Z
2), but an estimate is ±0.003 at NLO and at most ±0.002 at NNLO. We investigate the interplay between uncertainties on α
S
and uncertainties on parton distribution functions (PDFs). We show, for the first time, how both these sources of uncertainty
can be accounted for simultaneously in calculations of cross sections, and we provide eigenvector PDF sets with different
fixed α
S
values to allow further studies by the general user. We illustrate the application of these PDF sets by calculating cross
sections for W, Z, Higgs boson and inclusive jet production at the Tevatron and LHC. 相似文献
17.
Riccardo Barbieri Paolo Campli Gino Isidori Filippo Sala David M. Straub 《The European Physical Journal C - Particles and Fields》2011,71(12):1812
We study CP asymmetries in rare B decays within supersymmetry with a U(2)3 flavour symmetry, motivated by the SUSY flavour and CP problems, the hierarchies in the Yukawa couplings and the absence
so far of any direct evidence for SUSY. Even in the absence of flavour-blind phases, we find potentially sizable CP violating
contributions to b→s decay amplitudes. The effects in the mixing-induced CP asymmetries in B→ϕK
S
and B→η′K
S
, angular CP asymmetries in B→K
∗
μ
+
μ
− and the direct CP asymmetry in B→X
s
γ can be in the region to be probed by LHCb and next generation B factories. At the same time, these effects in B decays are compatible with CP violating contributions to meson mixing, including
a non-standard B
s
mixing phase hinted by current tensions in the CKM fit mostly between SyKS, eKS_{\psi K_{S}}, \epsilon_{K} and DMBs/DMBd\Delta M_{B_{s}}/\Delta M_{B_{d}}. 相似文献
18.
Hyperfine splittings (HFS) are calculated within the Field Correlator Method, taking into account relativistic corrections.
The HFS in bottomonium and the B
q
(q = n, s) mesons are shown to be in full agreement with experiment if a universal coupling α
HF = 0.310 is taken in perturbative spinspin potential. It gives M(B*) −M(B) = 45.7(3) MeV, M(B
s
* ) − M(B
s
) = 46.7(3) MeV (n
f
= 4), while in bottomonium ΔHF(b
$
\bar b
$
\bar b
) = M(Υ(9460)) − M(η
b
(1S)) = 63.4 MeV for n
f
= 4 and 71.1 MeV for n
f
= 5 are obtained; just the latter agrees with recent BaBar data. For unobserved excited states we predict M(Υ(2S))−M(η
b
(2S)) = 36(2)MeV,M(Υ(3S))−M(η
b
(3S)) = 28(2)MeV, and also M(B
c
*) = 6334(4) MeV, M(B
c
(2S)) = 6868(4) MeV, M(B
c
* (2S)) = 6905(4) MeV. The mass splittings between D(23
S
1) − D(21
S
0), D
s
(23
S
1) − D
s
(21
S
0) are predicted to be ∼75 MeV, which are significantly smaller than in several other studies but agree with the mass splitting
between recently observed D(2533) and D*(2610). 相似文献
19.
Line strengthS and radial matrix elementσ for the dipole allowed transitions withinn=2 complex of ions in the Be isoelectronic sequence have been fitted in the formsZ
2
S=A+B/(Z − C) andZσ=A′ + B′/(Z − C′). The constantsA, B, C andA′, B′, C′ have been calculated by employing a non-linear least square method. The relevant data forS andσ have been taken from calculations which includes correlation effects. It is shown that the fitted yalues ofA andA′ are in excellent accord with their hydrogenic values (Z →α) provided that we express the zeroth-order wavefunction of the ground state 1s22s2
1
S as a quantum-mechanical admixture of the Hartree-Fock (HF) state 1s22s2
1
S and the near-degenerate state 1s22p2
1
S. 相似文献
20.
H.Y. Wang Z.W. Ma E.Y. Jiang Y.J. He H.S. Huang 《Applied Physics A: Materials Science & Processing》1999,68(5):559-562
The structure and magnetic properties of Fe-N and Fe-Ti-N films have been studied as a function of annealing temperature Ta with a transmission electron microscope and a vibrating sample magnetometer. The as-prepared Fe-N films consist of the γ′-Fe4N and α′′-Fe16N2 phases, and the Fe-Ti-N films are composed of the γ′-Fe4N, α′′-Fe16N2, and TiN phases. The structural changes with annealing temperature in the Fe-N films are distinct. The α′′-Fe16N2 decomposes into α+γ′ phases in the Fe-N film annealed at about 300 °C, and it disappears in the film annealed at 350 °C. Annealing of the Fe-Ti-N
films shows no structural changes between room temperature (RT) and 500 °C. The saturation magnetization 4πMS and coercivity Hc of the Fe-N films change drastically with the annealing temperature Ta, whereas those of the Fe-Ti-N films do not change with Ta up to 500 °C. These results indicate that the additon of Ti may improve the thermal stability of Fe-N films.
Recieved: 6 Juli 1998 / Accepted: 19 Oktober 1998 / Published online: 10 March 1999 相似文献