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1.
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
2.
Contact interactions are searched for using the differential cross sections for the reactions e
+
e
–e
+
e
–, e
+
e
–µ
+
µ
–, e
+
e
–
+
– and e
+
e
– measured at 12 energies around the Z peak and corresponding to about 20 pb –1 of cumulated luminosity. Four-fermion contact term models assuming various chiralities of lepton currents are fitted to the lepton data and lower limits on the energy scale of such terms are set at 95% c.l. The limits vary in the range 0.9–4.7 TeV, depending on the model and on the lepton flavour. The ee contact terms are searched for assuming various chiralities. Limits on the energy scale between 79 and 130 GeV are extracted from the data. The results are compared and combined with those reported at lower energies.Deceased 相似文献
3.
A model-independent analysis of anomalous gauge coupling constants of W
± bosons is presented and the corresponding restrictions on them and on the electromagnetic characteristics of W
± bosons following from the experiments on measuring the e+ e- ? W+ W- ? ( e | / |
m, [`(v)] ) ?( q,[`(q)] ) {e^{+} }{e^{-} } \to {W^{+} }{W^{-} } \to \left( {{{e} \left/ {{\mu, \bar{v}}} \right.}} \right) \oplus \left( {q,\bar{q}} \right) process on the e
+
e
− International Linear Collider are obtained. The method of obtaining the model-independent restrictions on the anomalous gauge
constants is based on the use of the polarization scattering cross sections for different initial and final polarization states. 相似文献
4.
利用QCISD(T),SAC-CI方法和cc-pVQZ,aug-cc-pVTZ,6-311++G及6-311++G(3df,2pd)基组,对MgH分子的基态 X2Σ+,第一简并激发态 A2Π和第二激发态 B2Σ+的结构进行优化计算.通过对4个基组计算结果进行比较,得出6-311++G(3df,2pd)基组为最优基组.使用
关键词:
分子结构与势能函数
激发态
Murrell-Sorbie函数
C 6函数')" href="#">Murrell-Sorbie+ C6函数 相似文献
5.
By studying the scattering process of scalar particle pion on the noncommutative scalar quantum electrodynamics, the non-commutative amendment of differential scattering cross-section is found, which is dependent of polar-angle and the results are significantly different from that in the commutative scalar quantum electrodynamics, particularly when cos θ∼±1. The non-commutativity of space is expected to be explored at around Λ NC∼TeV. 相似文献
6.
CLEO-c measurements of the timelike form factors F
π
, F
K
at ? s=3.671\sqrt{s}=3.671 GeV provide a direct probe of power corrections (PC’s) at energies near m
B
. PC’s in F
π,K
and B→ Kπ, ππ are separated into perturbative and soft parts. In F
π,K
the latter are ≥ O(10) larger. A PC fit to the B→ Kπ, ππ data also yields a ≥ O(10) soft-to-perturbative hierarchy for the QCD penguin PC’s. Hence, both can be attributed to dominance of the soft-overlap
between energetic (approximately) back-to-back collinear partons, and consistency of the B→ Kπ, ππ fit with the Standard Model appears to be naturally realized. The CP asymmetries SKs p0S_{K_{s} \pi^{0}}, CKs p0C_{K_{s} \pi^{0}} are well determined, providing a clean test for new physics. 相似文献
7.
The cross-section for the π
+
π
−
π
0 invariant mass distribution in the γp reaction in the GeV region is calculated. This reaction is assumed to proceed through the formation of the ω-meson in the intermediate state, because the production cross-section for this meson in the γp reaction in the GeV region is significant and it has a large branching ratio (88.8%) in the π
+
π
−
π
0 channel. The cross-sections for this reaction are calculated using the energy-dependent reaction amplitude, f
γp→ωp(0), extracted from the latest ω-meson photoproduction data. We use established procedure to calculate other factors, like width and propagator of the ω-meson, so that our calculation can provide reliable cross-section. The calculated results reproduce the measured π
+
π
−
π
0 invariant mass distribution spectra in the γp reaction. 相似文献
8.
Light gravitino productions in association with a neutralino (selectron) in e
+
e
− ( e
−
γ) collisions are restudied in a scenario that the lightest supersymmetric particle is a gravitino and the produced neutralino
(selectron) promptly decays into a photon (electron) and a gravitino. We explicitly give the helicity amplitudes for the production
processes by using the effective goldstino interaction Lagrangian, and present the cross sections with different collision
energies and mass spectra. We also examine selection efficiencies by kinematical cuts and beam polarizations for the signal
and background processes, and show that the energy and angular distributions of the photon (electron) can explore the mass
of the t-channel exchange particle as well as the mass of the decaying particle at a future e
+
e
− ( e
−
γ) collider. 相似文献
9.
The decays η → 3 π
0 and η → π
0
π
+
π
− are considered within the isobar model. It is shown that, in order to explain the branching ratio and the shape of the Dalitz
plot for the decay η′ → 3 π
0, it is sufficient to take into account the contributions of the σ and a
0 mesons. The inclusion of the σ meson is necessary for reproducing the shape of the distribution over the Dalitz plot. The branching ratio for the decay
η′ → π
0
π
+
π
− is obtained. The predictions for the distributions over the Dalitz plot for this decay are presented. These predictions depend
strongly on model parameters. 相似文献
10.
We develop a systematic framework for exclusive rare B decays of the type B→ K
(∗)
l
+
l
− at large dilepton invariant mass q
2. It is based on an operator product expansion (OPE) for the required matrix elements of the nonleptonic weak Hamiltonian
in this kinematic regime. Our treatment differs from previous work by a simplified operator basis, the explicit calculation
of matrix elements of subleading operators, and by a quantitative estimate of duality violation. The latter point is discussed
in detail, including the connection with the existence of an OPE and an illustration within a simple toy model. 相似文献
11.
We present measurements of the hadronic photon structure function F
2
( x), in two Q
2 ranges with mean values of 5.9 GeV 2 and 14.7 GeV 2. The data were taken by the OPAL experiment at LEP, with
close to the Z
0 mass and correspond to an integrated e
+
e
– luminosity of 44.8 pb –1. In the context of a QCD-based model we find the quark transverse momentum cutoff separating the vector meson dominance (VMD) and perturbative QCD regions to be 0.27±0.10 GeV. We confirm that there is a significant pointlike component of the photon when the probe photon has Q
2>4 GeV 2. Our measurements extend to lower values of x than any previous experiment, and no increase of F
2
( x) is observed. 相似文献
12.
The T-odd correlation
in the decays K
+ → π
0
l
+
νγ ( l = e, μ) is investigated as a function of the parameters of the effective Lagrangian. It is shown that the T-odd correlation offers a good indicator of new physics in the vector and pseudovector sectors of the model under consideration.
In the scalar and pseudoscalar sectors, investigation of the T-odd correlation gives no way to improve the current limits on the parameters of various extensions of the Standard Model.
__________
Translated from Yadernaya Fizika, Vol. 67, No. 5, 2004, pp. 1025–1032.
Original Russian Text Copyright ? 2004 by Braguta, Likhoded, Chalov. 相似文献
13.
The emission spectrum of the A
2
Π
r
- X
2
Σ
+ band system of MgCl molecule (360–380 nm) has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution
of 0.035 cm −1. The spectra have been excited under flowing conditions in a demountable stainless steel hollow cathode lamp (400 V, 250
mA) containing anhydrous MgCl 2 and Ar. The resulting spectra are very intense and the 0-0, 1-1, 1-0 bands of A
2
Π
1/2- X
2
Σ
+ sub-transition and the 0-0 band of A
2
Π
3/2- X
2
Σ
+ sub-transition have been rotationally analyzed. Improved molecular constants have been derived using a least-squares fit
program in which optical data of earlier analyzed 0-1 and 0-2 bands ( A
2
Π
1/2- X
2
Σ
+) was also included. The Λ-doubling constants in the v′ = 0, 1 levels of the A
2
Π
1/2 sub-state are as expected, i.e. p
1 > p
0, where as it is found that the spin-doubling constants of the v″ = 0, 1 and 2 levels of the ground state X
2
Σ
+, decrease with the increase in v, i.e.
γ
0 > γ
1 > γ
2. This is indicative of the presence of some nearby state, influencing the spin-doubling. 相似文献
14.
We study the possibilities to analyse the data on leading neutrons production at first LHC runs. These data could be used
to extract from it π
+
p and π
+
π
+ cross-sections. In this note we estimate relative contributions of π, ρ and a
2 reggeons to charge exchanges and discuss related problems of measurements. 相似文献
15.
The results of recent experiments performed at KEK, Brookhaven National Laboratory, the Institute for High-Energy Physics
(Protvino), and CERN to study the reaction π
−
p → π
0
π
0
n are analyzed in detail. For S-wave pion-pion scattering in the channel of isospin I=0, new data are obtained for the phase shift δ
0
0
and the inelasticity parameter η
0
0
. Difficulties that arise in using, for the amplitudes of the S and D waves of the final π
0
π
0 system, physical solutions selected on the basis of partial-wave analyses are discussed. It is noteworthy that other solutions
are preferable in principle in the region of the invariant mass m of the π
0
π
0 system above 1 GeV. With the aim of clarifying the situation and further studying the properties of the f
0(980) resonance, it is proposed to perform, in the reaction π
−
p → π
0
π
0
n, an especially careful examination of the m region in the vicinity of the
threshold.
__________
Translated from Yadernaya Fizika, Vol. 67, No. 7, 2004, pp. 1380–1391.
Original Russian Text Copyright ? 2004 by Achasov, Shestakov. 相似文献
16.
Radiative decays π
0( π
0′) → γ + γ, π
0′ → ρ
0( ω) + γ, ρ
0′( ω′) → π
0 + γ, ρ
0′( ω′) → π
0′ + γ, and some processes of π
0′ production at lepton colliders are considered in the framework of the nonlocal SU(2) × SU(2) Nambu-Jona-Lasinio model. Mixing of the radially excited and the ground meson states is taken into account. Numerical
results for the decay and production processes are presented. 相似文献
18.
Due to its sensitivity to New Physics contributions, the branching ratio of the very rare decay B
s
0 → μ
+
μ
− is one of the most interesting measurements using the first data from the LHC accelerator. The analysis strategy for the
study of this channel in the LHCb experiment is presented, as well as a review of the potential of the experiment in such
study, using the latest simulations. With four months of nominal data taking, any enhancement from the Standard Model prediction
can be excluded. 相似文献
19.
The excitation of transitions from the 2
S
∘, 2
P
∘, and 2
D
∘ levels of the cobalt atom is studied by the method of extended crossing beams. Seventy-six excitation cross sections are
measured at an exciting electron energy of 50 eV. Nine optical excitation functions are recorded in the electron energy region
of 0–200 eV. Possible channels of excitation of levels under study are discussed. 相似文献
20.
BaBar’s observation of significant deviations of the pion transition form factor (TFF) from the asymptotic expectation with
Q
2>9 GeV 2 has brought about a serious crisis to the fundamental picture established for such a simple q[`( q)]q\bar{q} system by perturbative QCD, i.e. the dominance of collinear factorization at high momentum transfers for the pion TFF. We
show that non-factorizable contributions due to open flavors in γγ
∗→ π
0 could be an important source that contaminates the pQCD asymptotic limit and causes such deviations with Q
2>9 GeV 2. Within an effective Lagrangian approach, the non-factorizable amplitudes can be related to intermediate hadron loops, i.e.
K
(∗) and D
(∗) etc., and their corrections to the π
0 and η TFFs can be estimated. 相似文献
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