共查询到20条相似文献,搜索用时 703 毫秒
1.
A.A. Bagneid 《The European Physical Journal C - Particles and Fields》2008,54(4):547-553
We examine distributions of leptons produced in e+e- collisions, by a family nonuniversal extra gauge boson Z′, suggested by the model, and by other neutral gauge bosons occurring in left–right symmetric models and in superstring-inspired E6 models. We discuss how to distinguish the models by examining the couplings to fermions of the extra Z-boson through its
leptonic production cross sections and asymmetries. We show how the universality violation inherent in the model enhances the discovery potential of Z′ at future planned and proposed e+e- colliders. 相似文献
2.
Chong-Xing Yue Shuang Zhao 《The European Physical Journal C - Particles and Fields》2007,50(4):897-903
The littlest Higgs (LH) model predicts the existence of the doubly charged scalars , which generally have large flavor changing couplings to leptons. We calculate the contributions of Φ±± to the lepton flavor violating (LFV) processes li→ljγ and li→ljlklk, and we compare our numerical results with the current experimental upper limits on these processes. We find that some of
these processes can give severe constraints on the coupling constant Yij and the mass parameter MΦ. Taking into account the constraints on these free parameters, we further discuss the possible lepton flavor violating signals
of at high energy linear e+e- collider (ILC) experiments. Our numerical results show that the possible signals of might be detected via the subprocesses e±e±→l±l± in future ILC experiments. 相似文献
3.
A.E. Dorokhov E.A. Kuraev Yu.M. Bystritskiy M. Sečanský 《The European Physical Journal C - Particles and Fields》2008,55(2):193-198
We reconsider QED radiative corrections (RC) to the π0→e+e- decay width. One kind of RC investigated earlier has a renormalization group origin and can be associated with the final
state interaction of electron and positron. It determines the distribution of lepton pair invariant masses in the whole kinematic
region. The other type of RC has a double-logarithmic character and is related to almost on-mass-shell behavior of the lepton
form factors. The total effect of RC for π0→e+e- decay is estimated to be 3.2%, and for η→e+e- decay it is 4.3%.
PACS 13.25.Cq; 12.38.Lg; 12.38.-t 相似文献
4.
Chong-Xing Yue Nan Zhang Shi-Hai Zhu 《The European Physical Journal C - Particles and Fields》2008,53(2):215-219
The littlest Higgs model with T-parity predicts the existence of the T-odd particles, which can only be produced in pairs.
We consider pair production of the T-odd leptons in a future high energy linear e+e- collider (ILC). Our numerical results show that, as long as the T-odd leptons are not too heavy, they can be copiously produced
and their possible signals might be detected via the processes e+e-→L̄iLj in future ILC experiments. 相似文献
5.
N. Oshimo 《The European Physical Journal C - Particles and Fields》2005,39(3):383-388
The measurability of generation mixing is studied on pair production of sneutrinos in e
+
e
- collisions and their subsequent decays into two different charged leptons e and μ with two lighter charginos. The analyses are made systematically in a general framework of the supersymmetric extension
of the standard model. The production and decay process depends on the parameters of the chargino sector as well as those
of the sneutrino sector. Although generation-changing interactions are severely constrained by radiative charged-lepton decays,
sizable regions in the parameter space could still be explored at e
+
e
- colliders in the near future.
Received: 6 October 2004, Revised: 14 November 2004, Published online: 14 January 2005
PACS:
11.30.Hv, 12.15.Ff, 12.60.Jv, 14.80.Ly 相似文献
6.
We present an estimate of the cross-section for the exclusive production of a ρL
0-meson pair in e+e- scattering, which will be studied in the future high-energy International Linear Collider. For this aim, we complete calculations
of the Born order approximation of the amplitudes γ*
L,T(Q1
2)γ*
L,T(Q2
2)→ρL
0ρL
0, for arbitrary polarization of virtual photons and longitudinally polarized mesons, in the kinematical region s≫-t,Q1
2,Q2
2. These processes are completely calculable in the hard region Q1
2,Q2
2≫Λ2
QCD, and we perform most of the calculations in an analytical way. The resulting cross-section turns out to be large enough for
this process to be measurable with foreseen luminosity and energy, for Q1
2 and Q2
2 in the range of a few GeV2. 相似文献
7.
Oxyfluoroborate glass co-doped with Eu and Yb ions has been prepared and characterized for its optical properties through
photoluminescence, absorption and lifetime measurements. An intense red upconversion is observed from the 5D0 level of Eu3+ ions through energy transfer from Yb3+ to Eu3+ ion when excited with 980 nm. The Judd–Ofelt parameters have been evaluated to estimate the local site symmetry around the
Eu3+ ions. These parameters have been used to derive radiative properties such as transition probabilities, branching ratios,
radiative lifetimes and stimulated emission cross-sections for the 5D0–7FJ transitions. Decay of excitation of the 5D0 level has been measured by monitoring the 5D0→7F2 transition (613 nm) at room temperature. Quantum efficiency for this transition is found to be 73%. We also monitored the
effect of temperature on the fluorescence emission of Eu3+.
PACS 42.70.Ce; 42.70.Hj 相似文献
8.
V. E. Tarasov V. V. Khabarov A. E. Kudryavtsev V. M. Weinberg 《Physics of Atomic Nuclei》2008,71(8):1410-1423
The Kd reactions are considered in the impulse approximationwithNN final-state interactions (FSI) taken into account. Realistic parameters for the KN phase shifts are used. The “quasi-elastic” energy region, in which the elementary KN interaction is predominantly elastic, is considered. The theoretical predictions are compared with the data on the K
+
d → K
+
pn, K
+
d → K0
pp, K
+
d → K
+
d, and K
+
d total cross sections. The NN FSI effect in the reaction K
+
d → K
+
pn has been found to be large. The predictions for the Kd cross sections are also given for slow kaons, produced from ϕ(1020) decays, as the functions of the isoscalar KN scattering length a
0. These predictions can be used to extract the value of a
0 from the data.
The text was submitted by the authors in English. 相似文献
9.
K. Terasaki 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):676-678
Although assigning D
s0
+(2317) to the I
3 = 0 component
of iso-triplet four-quark mesons is favored by experiments, its neutral and doubly charged partners have not yet been observed.
It is discussed why they were not observed in inclusive e
+
e
-→cˉ experiment and that they can be observed in B decays. 相似文献
10.
Xuelei Wang Yaobei Liu Jihong Chen Hua Yang 《The European Physical Journal C - Particles and Fields》2007,49(2):593-597
The littlest Higgs model is the most economical one among various little Higgs models. In the context of the littlest Higgs
model, we study the process e+e-→e+e-H at the ILC and calculate the correction of the littlest Higgs model to the cross section of this process. The results show
that, in the favorable parameter spaces preferred by the electroweak precision data, the value of the relative correction
is in the range from a few percent to tens percent. In most cases, the correction is large enough to reach the measurement
precision of the ILC. Therefore, the correction of the littlest Higgs model to the process e+e-→e+e-H might be detected at the ILC, which will give an ideal way to test the model.
PACS 12.60.Nz; 14.80.Mz; 12.15.Lk; 14.65.Ha 相似文献
11.
Complementing the preceding study of charged scalar leptons, the sector of the neutral scalar leptons, sneutrinos, is investigated in a high-precision analysis for future e
+
e
- linear colliders. The theoretical predictions for the cross-sections are calculated at the thresholds for non-zero widths and in the continuum including higher-order corrections at the one-loop level. Methods for measuring the sneutrino masses and the electron-sneutrino-gaugino Yukawa couplings are presented, addressing theoretical problems specific for the sneutrino channels.Received: 10 September 2004, Revised: 11 October 2004, Published online: 3 March 2005 相似文献
12.
W. Zhang S. You C. Sun Y. Zhang J. Xu Z. Ma Y. Feng H. Liu P. Quinet é. Biémont Z. Dai 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):1-8
First laser spectroscopic measurements of the 6s5d3D1-6s6p1P1 and 6s5d3D2-6s6p1P1 transitions in several isotopes of atomic barium have been performed. The hyperfine structure of these transitions was optically
resolved and isotope shifts for even and odd isotopes were determined. The isotope shifts show a deviation from their expected
behavior for odd isotopes in an analysis based on King-plots. This observation puts atomic structure calculations at test
because available theories do not predict this. A profound understanding of the wavefunctions for heavy alkaline earth systems
like barium (Ba) and radium (Ra) is essential for a theoretical evaluation of their sensitivity to fundamental symmetry breaking
effects such as they could be observed, e.g., through permanent electric dipole moments. Further the absolute frequency of
the 6s2
1S0-6s6p3P1 intercombination line in 138Ba was determined to be 12 636.6232(1) cm-1. 相似文献
13.
The top-pions (Πt
0,±) and the top-Higgs (ht
0) are the typical particles predicted by the topcolor-assisted technicolor (TC2) model and the observation of these particles
can be regarded as direct evidence of the TC2 model. In this paper, we study three pair production processes of these new
particles at the next generation eγ colliders, i.e., e-γ→e-Πt
+Πt
-, e-γ→νeΠt
-Πt
0 and e-γ→νeΠt
-ht
0. The results show that the production rates can reach the level 100–101 fb with reasonable parameter values. So one can expect that enough signals could be produced in future high- energy linear
collider experiments. Furthermore, the flavor-changing (FC) decay modes Πt
-→bc̄, Πt
0(ht
0)→tc̄ can provide us with the typical signal to detect these new particles.
PACS 12.60Nz; 14.80.Mz; 12.15.LK; 14.65.Ha 相似文献
14.
M. A. Baig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):437-442
We report new high resolution photoabsorption measurements of the
5d-subshell excitation spectra of mercury using a 3-meter normal incidence
spectrograph equipped with a 6000 line/mm holographic grating and
synchrotron radiation emitted by the Bonn 2.5 GeV electron accelerator as
the background source of continuum. The observed spectra reveal autoionizing
resonances attached to the 5d9(2D5/2)6s2 and
5d9(2D3/2)6s2 parent ion levels of mercury. We have
analysed the line shapes of the lower members of the 5d96s2 np and
nf J = 1 autoionizing resonances using the phase shifted formulation of the
MQDT and extracted the interaction parameters. 相似文献
15.
The highly charged ion 40Ar16+ with the velocity (kinetic energy E
K=150 keV, velocity V=8.5×105 m/s) smaller than Bohr velocity (V
Bohr=2.9×106 m/s) was found to hove impacts on the surfaces of metals Ni, Mo, Au and Al, and the Ar atomic infrared light lines and X-rays
spectra were simultaneously measured. The experimental results show that the highly charged ion that captures electrons is
neutralized, and the multiply-excited hollow atom forms. The hollow atom cascade decay radiates lights from infrared to X-ray
spectrum. The intensity of infrared lights shows that the metallic work functions play an important role in the neutralization
process of highly charged ions during their interaction with metallic surfaces, which verifies the classical over-the-barrier
model.
Supported by the National Natural Science Foundation of China (Grant No. 10574132), the Natural Science Foundation of Shaanxi
Province (Grant No. 2007A05) and the Talents Introduction Project of Xianyang Normal University (Grant No. 05XSYK103) 相似文献
16.
N. Yongram 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):71-74
Spin correlations are carefully investigated in elastic e+e- scattering in QED, for initially polarized as well as unpolarized particles,
with emphasis placed on energy or speed of the underlying particles involved in the process. An explicit expression is derived
for the corresponding transition probabilities in closed form to the leading order. These expressions differ from those
obtained from simply combining the spins of the relevant particles, which are of kinematic nature.
It is remarkable that these explicit results obtained from quantum field theory show a clear violation of Bell's inequality
at all energies, in support of
quantum theory in the relativistic regime. We hope that our explicit expression will lead to experiments, of the type described
in the bulk of this paper, that monitor speed. 相似文献
17.
M. G. Nikolic M. S. Rabasovic J. Krizan S. Savic-Sevic M. D. Rabasovic B. P. Marinkovic A. Vlasic D. Sevic 《Optical and Quantum Electronics》2018,50(6):258
In this paper we study the possibility of using the synthesized nanopowder samples of Gd2Zr2O7:Eu3+ for temperature measurements by analyzing the temperature effects on its photoluminescence. The nanopowder was prepared by solution combustion synthesis method. The photoluminescence spectra used for analysis of Gd2Zr2O7:Eu3+ nano phosphor optical emission temperature dependence were acquired using continuous laser diode excitation at 405 nm. The temperature dependencies of line emission intensities of transitions from 5D0 and 5D1 energy levels to the ground state were analyzed. Based on this analysis we use the two lines intensity ratio method for temperature sensing. Our results show that the synthesized material can be efficiently used as thermographic phosphor up to 650 K. 相似文献
18.
A new evaluation of the hadronic vacuum polarization contribution to the muon magnetic moment is presented. We take into account the reanalysis of the low-energy e
+
e
-annihilation cross section into hadrons by the CMD-2 Collaboration. The agreement between e
+
e
-and
spectral functions in the
channel is found to be much improved. Nevertheless, significant discrepancies remain in the center-of-mass energy range between 0.85 and
, so that we refrain from averaging the two data sets. The values found for the lowest-order hadronic vacuum polarization contributions are
where the errors have been separated according to their sources: experimental, missing radiative corrections in e
+
e
-data, and isospin breaking. The corresponding Standard Model predictions for the muon magnetic anomaly read
where the errors account for the hadronic, light-by-light (LBL) scattering and electroweak contributions. The deviations from the measurement at BNL are found to be
(1.9
) and
(0.7
) for the e
+
e
-- and
-based estimates, respectively, where the second error is from the LBL contribution and the third one from the BNL measurement.Received: 7 September 2003, Published online: 30 October 2003 相似文献
19.
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
20.
Electron paramagnetic resonance (EPR) spectra of Gd3+ aqua complexes are measured in dilute aqueous solutions of Gd(NO3)3 (C<0.2 M) at room temperature. A partial resolution of the fine structure observed in the spectra is characteristic of solid disordered systems and results in an increase in the effective width of the EPR line with a decrease in the Gd3+ concentration. This phenomenon is explained in terms of adsorption of Gd3+ aqua ions on the surface of the measuring capillaries. The fine structure is revealed in the EPR spectra of Gd(NO3)3 aqueous solutions, namely, the Gd(NO3)3 solutions vitrified at a temperature of 77 K (with an addition of 10–15 vol % glycerol) and Gd(NO3)3 solutions quasi-vitrified at 298 K (with an addition of 70–90 vol % glycerol). Analysis of the EPR spectra demonstrates that these solutions contain two types of aqua complexes with fine structure parameters D1=180 G and D2=580 G. Reasoning from a comparison with x-ray diffraction data, the fine structure parameters D1 and D2 are assigned to higher symmetric eight-coordinate and lower symmetric nine-coordinate Gd3+ aqua complexes, respectively. 相似文献