共查询到20条相似文献,搜索用时 62 毫秒
1.
A. V. Derbin A. S. Kayunov V. N. Muratova 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):805-810
A search for the axioelectric absorption of 5.5-MeV solar axions produced in the p + d → 3He + γ (5.5 MeV) reaction was performed with two BGO detectors placed inside a low-background setup. Constraints on the axion-electron
coupling constant were obtained for axions with masses in the (0.1–1.0)-MeV range: g
Ae ≤ (1.8–9.0) × 10−7. The solar positron flux from A → e− + e+ decay was determined for axions with masses m
A
> 2m
e. Using the existing experimental data on the interplanetary positron flux, a new constraint on the axion-electron coupling
constant for axions with masses in the (1.2–5.4)-MeV range was obtained: g
Ae ≤ (1–5) × 10−17. 相似文献
2.
A. N. Ivanov H. Oberhummer N. I. Troitskaya M. Faber 《The European Physical Journal A - Hadrons and Nuclei》2000,8(2):223-250
A dynamics of low-energy nuclear forces is investigated for low-energy electromagnetic and weak nuclear reactions with the
deuteron in the Nambu-Jona-Lasinio model of light nuclei by example of the neutron-proton radiative capture (M1-capture) n
+ p → D + γ, the photomagnetic disintegration of the deuteron γ + D → n + p and weak reactions of astrophysical interest. These are the solar proton burning p + p → D + e+ + ν
e, the pep-process p + e− + p → D + ν
e and the neutrino and antineutrino disintegration of the deuteron caused by charged ν
e + D → e− + p + p, + D → e+ + n + n and neutral ν
e() + D → ν
e() + n + p weak currents. 相似文献
3.
Using the data of about 33 pb-1 collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied the exclusive semileptonic
decays D+→K-π+e+νe, D0→K̄0π-e+νe, D+→K̄*0e+νe and D0→K*-e+νe. The absolute branching fractions for the decays are measured to be BF(D+→K-π+e+νe)=(3.50±0.75±0.27)%, BF(D0→K̄0π-e+νe)=(2.61±1.04±0.28)%, BF(D+→K̄*0e+νe)=(5.06±1.21±0.40)% and BF(D0→K*-e+νe)=(2.87±1.48±0.39)%. The ratio of the vector to pseudoscalar semileptonic decay rates Γ(D+→K̄*0e+νe)/Γ(D+→K̄0e+νe) is determined to be 0.57±0.17±0.02. 相似文献
4.
Remco van der Hofstad Frank den Hollander Gordon Slade 《Communications in Mathematical Physics》2002,231(3):435-461
We construct the incipient infinite cluster measure (IIC) for sufficiently spread-out oriented percolation on ℤ
d
× ℤ+, for d +1 > 4+1. We consider two different constructions. For the first construction, we define ℙ
n
(E) by taking the probability of the intersection of an event E with the event that the origin is connected to (x,n) ℤ
d
× ℤ+, summing this probability over x ℤ
d
, and normalising the sum to get a probability measure. We let n → ∞ and prove existence of a limiting measure ℙ∞, the IIC. For the second construction, we condition the connected cluster of the origin in critical oriented percolation
to survive to time n, and let n → ∞. Under the assumption that the critical survival probability is asymptotic to a multiple of n
−1, we prove existence of a limiting measure ℚ∞, with ℚ∞ = ℙ∞. In addition, we study the asymptotic behaviour of the size of the level set of the cluster of the origin, and the dimension
of the cluster of the origin, under ℙ∞. Our methods involve minor extensions of the lace expansion methods used in a previous paper to relate critical oriented
percolation to super-Brownian motion, for d+1 > 4+1.
Received: 13 December 2001 / Accepted: 11 July 2002 Published online: 29 October 2002
RID="*"
ID="*" Present address: Department of Mathematics and Computer Science, Eindhoven University of Technology, P.O. Box 513,
5600 MB Eindhoven, The Netherlands. E-mail: rhofstad@win.tue.nl 相似文献
5.
Inequality of the rates for K
0 → π+
e
− υ− and K
0 → π−
e
+
ν transitions, reported by CPLEAR, and an asymmetry in the distribution of the dihedral angle between the π+π− and e
+
e
− planes in K
L → π+π−
e
+
e
− decays, found by KTeV, have been announced as demonstrations of T-noninvariance. These results are critically interpreted and compared as proofs of the failure of reciprocity. 相似文献
6.
N. N. Achasov 《JETP Letters》1996,63(8):601-606
It is shown that BR(χ
b1(1 P)→e
+
e
−)≃3.3· 10−7 and BR(χ
c1(1 P)→e
+
e
−)≃10−8. This gives realistic possibilities for searching for the production of χ
b1(1 P) and ξ
c1(1 P) states in e
+
e
− collisions, even on the present-day colliders, to say nothing of b and c-τ factories.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 569–574 (25 April 1996) 相似文献
7.
V. M. Aul’chenko M. N. Achasov A. V. Bozhenok A. D. Bukin D. A. Bukin S. V. Burdin I. A. Gaponenko V. B. Golubev T. V. Dimova S. I. Dolinskii V. P. Druzhinin M. S. Dubrovin V. N. Ivanchenko P. M. Ivanov A. A. Korol’ S. V. Koshuba A. A. Mamutkin E. V. Pakhtusova S. I. Serednyakov V. A. Sidorov Z. K. Silagadze Yu. V. Usov V. V. Sharyi Yu. M. Shatunov 《JETP Letters》1999,69(2):97-102
A search for the process e
+
e
−→φ(1020)→η″(958) γ in the decay channel η″→π
+
π
−
η, η→γγ was made in an experiment at the VEPP-2M e
+
e
− collider with the SND detector. Analysis confirms the occurrence of φ→η″γ decay with probability B(φ→η″ γ)=(6.7
−2.9
+3.4
)×10−5.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 2, 87–91 (25 January 1999) 相似文献
8.
We calculate the cross-section of the inverse beta decay process,v
e+n → p+e, in a background magnetic field which is much smaller than m
p
2/e
. Using exact solutions of the Dirac equation in a constant magnetic field, we find the cross-section for arbitrary polarization
of the initial neutrons. The cross-section depends on the direction of the incident neutrino even when the initial neutron
is assumed to be at rest and has no net polarization. Possible implications of the result are discussed. 相似文献
9.
M. N. Achasov K. I. Beloborodov A. V. Berdyugin A. G. Bogdanchikov A. V. Bozhenok A. D. Bukin D. A. Bukin T. V. Dimova V. P. Druzhinin V. B. Golubev A. A. Korol S. V. Koshuba E. V. Pakhtusova S. I. Serednyakov Yu. M. Shatunov V. A. Sidorov Z. K. Silagadze A. N. Skrinsky Yu. A. Tikhonov A. V. Vasiljev 《Journal of Experimental and Theoretical Physics》2006,103(3):380-384
The corrected cross section of the e
+
e
− → π+π− process measured in the spherical neutral detector experiment at the VEPP-2M e
+
e
− collider is presented. The update is necessary due to a flaw in the e
+
e
− → π+π− and e
+
e
− → μ+μ− Monte Carlo event generators used previously in data analysis.
The text was submitted by the authors in English. 相似文献
10.
Using a data sample of integrated luminosity of about 33 pb-1 collected around 3.773 GeV with the BESII detector at the BEPC collider, the semileptonic decays D+→φe+νe, D+→φμ+νμ and the hadronic decay D+→φπ+ are studied. The upper limits of the branching fractions are set to be BF(D+→φe+νe)<2.01% and BF(D+→φμ+νμ)<2.04% at the 90% confidence level. The ratio of the branching fractions for D+→φπ+ relative to D+→K-π+π+ is measured to be 0.057±0.011±0.003. In addition, the branching fraction for D+→φπ+ is obtained to be (5.2±1.0±0.4)×10-3. 相似文献
11.
S. S. Bulanov 《Physics of Atomic Nuclei》2004,67(2):314-327
The dependence of K
S, L
→ π
+
π
−
γ decay probabilities on photon polarization is calculated. The phases of the terms of the amplitude that arise from the pion-pion
interaction are obtained by using a simple realistic model of pion-pion interaction via virtual ρ meson, instead of chiral perturbation theory (ChPT). The results are compared with those of other authors and the origin
of the discrepancies is explained. It is shown that the standard ChPT approach for K
S, L
→ π
+
π
−
γ decays cannot reproduce the contribution of the ρ meson to the P-wave ππ interaction. The departure of the photon spectrum from pure bremsstrahlung due to the pion-loop contribution to the electric
direct emission amplitude is calculated. It is shown that the interference between the terms of amplitude with different CP parity appears only when the photon is polarized (linearly or circularly). Instead of measuring the linear polarization,
the angular correlation between the π
+
π
− and e
+
e
− planes in K
S, L
→ π
+
π
−
e
+
e
− decay can be studied.
From Yadernaya Fizika, Vol. 67, No. 2, 2004, pp. 332–345.
Original English Text Copyright ? 2004 by Bulanov.
This article was submitted by the author in English. 相似文献
12.
In the framework of the chiral perturbation theory we obtain the phenomenological relations between decay branches of rare
radiative kaon to pion and leptons K
+ → π+
l
+
l
− and K
S
0 → π0
l
+
l
− and meson form factors. The comparison of these results with the present-day experimental data shows us that the ChPT relations
for a charge kaon can determine meson form factors from already measured decay rates at high precision level. However, in
the case of the neutral kaon decays K
0 → π0
e
+
e
−(μ+μ−) the form factor data are known to a higher precision than data on the differential rates of radiative kaon decay K
0 π0
e
+
e
−(μ+μ−). 相似文献
13.
Preliminary data on the reactions e
+
e
−→φ→γ f
0(980)→γπ0π0 together with data on ππ scattering and the reactions J/ψ→φπ+π− and K
−
p→π +π−(Λ,Σ) are analyzed. The analysis shows that the mass of the f
0(980) meson is
= 950 MeV, and BR(φ→γf
0→γπ0π0)≃ 1× 10−4, indicating that the f
0(980) resonance is of a four-quark nature.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 445–449 (10 April 1998) 相似文献
14.
L. Cappiello O. Catà G. D’Ambrosio Dao-Neng Gao 《The European Physical Journal C - Particles and Fields》2012,72(1):1872
We study the decay K
+→π
+
π
0
e
+
e
−, currently under analysis by the NA62 Collaboration at CERN. In particular, we provide a detailed analysis of the Dalitz
plot for the long-distance, γ
∗-mediated, contributions (Bremsstrahlung, direct emission and its interference). We also examine a set of asymmetries to isolate
genuine short-distance effects. While we show that charge asymmetries are not required to test short distances, they provide
the best environment for its detection. This constitutes by itself a strong motivation for NA62 to study K
− decays in the future. We therefore provide a detailed study of different charge asymmetries and the corresponding estimated
signals. Whenever possible, we make contact with the related processes K
+→π
+
π
0
γ and K
L
→π
+
π
−
e
+
e
− and discuss the advantages of K
+→π
+
π
0
e
+
e
− over them. 相似文献
15.
A. I. Reznikov S. Ya. Umanskii Yu. F. Chaikina 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(2):203-209
Rate constants for electron-vibrational energy exchange Ar(3
P
2) + N2(X
1Σ
g
+, ν = 0) → Ar(1
S
0) + N2(C
3Π
u
, ν′), where ν′ = 0, 1, 2, were calculated. Calculations were performed taking into account the presence of a resonance in electron scattering
by N2(X
1Σ
g
+). As a result, the interaction of Ar(3
P
2) with N2(X
1Σ
g
+, ν = 0) was characterized by attraction and, in the end, intersection of electron-vibrational potential surfaces correlating
with Ar(3
P
2) + N2(X
1Σ
g
+, ν = 0) and Ar(1
S
0) + N2(C
3Π
u
, ν′) at interparticle distances of 2.5–3.5 ?. Exchange interaction at which electron-vibrational transitions in the region of
intersection of electron-vibrational transitions in the region of intersection of electron-vibrational potential surfaces
accompanied by spin exchange were induced was calculated by the asymptotic method. The rate constants determined at 300–600
K were on the order of 10−11−10−12 cm3/s and weakly increased as the temperature grew. Mainly the C
3Π
u
, ν′ = 0 state of the N2 molecule was populated. The calculation results were in satisfactory agreement with the experimental data obtained at 300
K. 相似文献
16.
A.W.K. Mok K.J. Sebastian 《The European Physical Journal C - Particles and Fields》2008,56(2):189-202
Using the helicity formulism, we calculate the combined angular distribution function of the polarized gamma photons and electron
in the cascade process pp̄→ψ’→χJ+γ1→ψ+γ2+γ1→e++e-+γ2+γ1 (J=0,1,2), when p̄ and p are unpolarized. We also present the partially integrated angular distribution functions in different
cases. Our results show that by measuring the two-particle angular distribution of γ1 and γ2 and that of γ2 and e- with the polarization of either one of the two particles, one can determine the relative magnitudes as well as the relative
phases of the helicity amplitudes in the radiative decay processes ψ’→χJ+γ1 and χJ→ψ+γ2.
PACS 11.80.Cr; 13.20.Fc; 13.60.Le; 14.40.Gx 相似文献
17.
Catherine Silvestre 《The European Physical Journal C - Particles and Fields》2009,61(4):841-845
In this paper, we calculate the decay rates of the D
+→D
0
e
+
ν, D
S
+→D
0
e
+
ν,
, D
S
+→D
+
e
−
e
+ and B
S
0→B
0
e
−
e
+ semileptonic decay processes, in which only the light quarks decay, while the heavy flavors remain unchanged. The branching
ratios of these decay processes are calculated with the flavor SU(3) symmetry. The uncertainties are estimated by considering
the SU(3) breaking effect. We find that the decay rates are very tiny in the framework of the standard model. We also estimate
the sensitivities of the measurements of these rare decays at future experiments, such as BES-III, super-B and LHC-b. 相似文献
18.
Using form factors derived from the light-cone sum rules, we investigate B
s
→φℓ
+
ℓ
− (ℓ=e,μ,τ) in a single universal extra dimension model (UED). In UED, there is only one new parameter with respect to the Standard
Model (SM), which is the inverse of the compactification radius R of the extra dimension. In this work, the branching ratios, the dilepton invariant mass spectra, the forward–backward asymmetries,
and the lepton polarization asymmetries of B
s
→φℓ
+
ℓ
− are calculated. For a lower value of 1/R, there are some considerable discrepancies between the UED and SM. However, with the increase of 1/R, the effect of UED tends to diminish; in particular for 1/R≥1000 GeV, two models have approximately the same predictions. Compared with data from CDF for B
s
→φμ
+
μ
−, we find that the 1/R tends to be larger than 350 GeV. We also find that the zero crossing point of the forward–backward asymmetry of B
s
→φμ
+
μ
− becomes smaller, which would be an important platform for probing the UED effect. These results could be tested in the Large
Hadron Collider (LHC) at CERN and the future super-B factory. 相似文献
19.
R. Riahi P. Teulet Y. Cressault A. Gleizes Z. Ben Lakhdar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):185-192
A method is presented to calculate the radiative transition probabilities and the radiative recombination rate coefficients
between electronic molecular states. Total transition probabilities are determined from vibrational transition probabilities
without considering the detailed rotational structure of the molecular electronic states. Radiative recombination rate coefficients
are obtained from the computation of vibrational photo-ionisation cross sections. Concerning spontaneous emission, Lyman (B
→ X) and Werner (C → X) band systems of H2 and Meinel (A → X), (B → A) and (B → X) band systems of OH are investigated. For radiative recombination, transitions between
H2+ (X) and H2(X), and between OH+(X, a, A, b, and c) and OH(X) are considered. Transition probabilities and recombination rate coefficients are calculated
as a function of temperature in the range 1500–15 000 K. 相似文献
20.
K. A. Bronnikov B. E. Meierovich 《Journal of Experimental and Theoretical Physics》2008,106(2):247-264
We consider (d
0 + 2)-dimensional configurations with global strings in two extra dimensions and a flat metric in d
0 dimensions, endowed with a warp factor e
2γ depending on the distance l from the string center. All possible regular solutions of the field equations are classified by the behavior of the warp
factor and the extradimensional circular radius r(l). Solutions with r → ∞ and r → const > 0 as l → ∞ are interpreted in terms of thick brane-world models. Solutions with r → 0 as l → l
c > 0, i.e., those with a second center, are interpreted as either multibrane systems (which are appropriate for large enough
distances l
c between the centers) or as Kaluza-Klein-type configurations with extra dimensions invisible due to their smallness. In the
case of the Mexican-hat symmetry-breaking potential, we build the full map of regular solutions on the (ɛ, Γ) parameter plane,
where ɛ acts as an effective cosmological constant and Γ characterizes the gravitational field strength. The trapping properties
of candidate brane worlds for test scalar fields are discussed. Good trapping properties for massive fields are found for
models with increasing warp factors. Kaluza-Klein-type models are shown to have nontrivial warp factor behaviors, leading
to matter particle mass spectra that seem promising from the standpoint of hierarchy problems.
The text was submitted by the authors in English. 相似文献