共查询到20条相似文献,搜索用时 15 毫秒
1.
D. Buskulic D. Decamp C. Goy J. -P. Lees M. -N. Minard B. Mours B. Pietrzyk R. Alemany F. Ariztizabal P. Comas et al. 《Zeitschrift fur Physik C Particles and Fields》1993,59(2):215-229
Contact interactions are searched for using the differential cross sections for the reactionse
+
e
–e
+
e
–,e
+
e
–µ
+
µ
–,e
+
e
–
+
– ande
+
e
– measured at 12 energies around theZ 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. Theee 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
2.
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
3.
Murugesh Duraisamy Alexander L. Kagan 《The European Physical Journal C - Particles and Fields》2010,70(4):921-925
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
4.
Jianhua Wang Kang Li Sayipjamal Dulat Yi Yuan Kai Ma 《International Journal of Theoretical Physics》2012,51(8):2639-2647
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 cosθ∼±1. The non-commutativity of space is expected to be explored at around ΛNC∼TeV. 相似文献
5.
K. Mawatari B. Oexl Y. Takaesu 《The European Physical Journal C - Particles and Fields》2011,71(11):1783
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
6.
Swapan Das 《Pramana》2010,75(4):665-674
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
7.
Damir Be?irevi? Benjamin Haas 《The European Physical Journal C - Particles and Fields》2011,71(8):1734
The axial coupling and the magnetic moment of D
∗-meson or, more specifically, the couplings gD*Dpg_{D^{\ast}D\pi} and gD*Dgg_{D^{\ast}D\gamma }, encode the non-perturbative QCD effects describing the decays D
∗→Dπ and D
∗→Dγ. We compute these quantities by means of lattice QCD with N
f=2 dynamical quarks, by employing the Wilson (“clover”) action. On our finer lattice (a≈0.065 fm) we obtain gD*Dp+=20±2g_{D^{\ast}D\pi^{+}}=20\pm2, and gD*0 D0g=2.0±0.6 GeV-1g_{D^{\ast0} D^{0}\gamma}=2.0\pm 0.6~{\rm GeV}^{-1}. This is the first determination of gD*0 D0gg_{D^{\ast0} D^{0}\gamma} on the lattice. We also provide a short phenomenological discussion and the comparison of our result with experiment and
with the results quoted in the literature. 相似文献
8.
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