共查询到20条相似文献,搜索用时 15 毫秒
1.
《Physics letters. [Part B]》1987,193(1):147-150
A search for the lepton family number violating decay D0→μe is reported. No signal is observed in a data sample of 9.3 pb−1 collected at the ζ (3770) resonance with the MARK III detector, where 0.18±0.06±0.05 background events are expected. A 90% confidence level upper limit on the branching fraction B(D0→μe) of 1.5 × 10−4 is obtained. 相似文献
2.
We analyzeK decays in the framework of Chiral Perturbation Theory. We study the different Dalitz plot distributions, trying to find regions whereo(p
6) contributions could be more easily detected. To fulfill this program we compute all theo(p
4) loop and counterterm contributions, finding a substantial agreement with the existing calculations and adding some small missing terms inK
S
+–.Work supported in part by the Human Capital and Mobility Program, EEC Contract N. CHRX-CT920026 相似文献
3.
We continue our endeavor to investigate lepton number violating(LNV) processes at low energies in the framework of effective field theory(EFT).In this work we study the LNV tau decays τ~+→l~-P_i~+P_j~+,where l=e,μand P_(i,j)~+denote the lowest-lying charged pseudoscalars π~+,K~+.We analyze the dominant contributions in a series of EFTs from high to low energy scales,namely the standard model EFT(SMEFT),the low-energy EFT(LEFT),and the chiral perturbation theory(χPT).The decay branching ratios are expressed in terms of the Wilson coefficients of dimension-five and-seven operators in SMEFT and the hadronic low-energy constants.These Wilson coefficients involve the first and second generations of quarks and all generations of leptons;thus,they cannot be explored in low-energy processes such as nuclear neutrinoless double beta decay or LNV kaon decays.Unfortunately,the current experimental upper bounds on the branching ratios are too weak to set useful constraints on these coefficients.Alternatively,if we assume the new physics scale is larger than 1 TeV,the branching ratios are well below the current experimental bounds.We also estimate the hadronic uncertainties incurred in applying χPT to τ decays by computing one-loop chiral logarithms and attempt to improve the convergence of chiral perturbation by employing dispersion relations in the short-distance part of the decay amplitudes. 相似文献
4.
5.
A method is proposed for the determination of the Lorentz structure of the electroweak interaction in semi-hadronic τ decays. Spin correlations in the process $$e^ + e^ - \to \tau ^ + \tau ^ - \to \bar v_\tau \pi ^ + \pi ^0 v_\tau \pi ^ - \pi ^0 $$ are exploited for a measurement of the normalized product, γAV = 2Re{gAg V * }/(|gV|2 + |gV|2), of the vector (g V ) and axial vector (g A ) coupling of the τ lepton. The contribution of scalar (g S ) or pseudo-scalar (g P ) couplings is also investigated. Since in the above process the direction of flight of the τ leptons can be reconstructed up to a twofold ambiguity a likelihood method using the whole kinematic information can be employed. The matrix element entering the likelihood function has been evaluated in terms of the momenta and angles of the observed pions. The sensitivity of the derived method in ane + e ? energy region around 10 GeV has been investigated for the ARGUS experiment using Monte Carlo simulations. 相似文献
6.
M. Benayoun S. I. Eidelman V. N. Ivanchenko 《Zeitschrift fur Physik C Particles and Fields》1996,72(2):221-230
Data one + e ?→η/π 0 γ collected by the Neutral Detector at Novosibirsk in a c.m. energy range up to 1.04 GeV have been studied with a purpose to single out of the scattering amplitude the triangle anomaly contribution predicted byqcd, pcac and Chiral Theories. We show that the cross section fore + e ?→π 0 γ exhibits no sensitivity to theπ 0 triangle anomaly; instead, the cross section fore + e ?→ηγ shows a clear sensitivity to the value of theη triangle anomaly and the best fit corresponds to a value for theη width in good correspondence with the world average value. It is also shown that the value of theρ→ηγ branching fraction is noticeably influenced by the existence of the anomaly. Finally, we give for the first time the absolute value for the hadronic phases of the vector mesons for the decay modesηγ andπ 0 γ. 相似文献
7.
《Physics letters. [Part B]》1986,166(4):473-478
A search for decays of heavy neutrinos was conducted by the CHARM Collaboration in a prompt neutrino beam produced by dumping 400 GeV protons in a Cu target, and in the CERN wide-band neutrino beam produced by 400 GeV primary protons. No candidate event was found. In the beam-dump experiment heavy neutrinos have been assumed to be produced by mixing in charmed D meson decays. Neutrinos decaying into e+e−ve, μ+e−vμ, and μ+μ−vμ were searched for. Limits of |Uei|2, |Uμi|2 < 10−7 were obtained for neutrino masses around 1.5 GeV. In the wide-band experiment heavy neutrinos were assumed to be produced by neutral-current neutrino interactions in the CHARM calorimeter. Here a search was made for neutrinos decaying into a μ and hadrons. This experiment is sensitive to decays of neutrinos with mass in the range 0.5–2.8 GeV with limits of |Uμi|2 < 3 × 10−4 for masses around 2.5 GeV. These measurements extend our previous results in the mass range 10–400 MeV. 相似文献
8.
We estimate the rates ofB 0 decays into neutral charmed final states \(B^0 \to \overline {D^{ * 0} } \gamma ,B^0 \to \overline {D^{ * 0} } \pi ^0 ,B^0 \to \overline {D^0 } \pi ^0 ,B^0 \to \overline {D^0 } \omega \) , by considering factorizable, vector meson dominance and long distance contributions. We also discuss the role of these decay modes as a source of background events in the search for exclusiveb→sγ transitions in very high energy experiments, e.g. at LEP. 相似文献
9.
10.
M. P. Rekalo 《Russian Physics Journal》1987,30(4):341-344
The general structure is obtained of the polarization effects for the single-photon mechanism in the decays AB+++–.This structure takes into account possible violations of the P- and T-invariances in the electromagnetic interaction of hadrons. Use is made only of the principal properties of the electrodynamics of hadrons, such as the conservation of the hadronic electromagnetic current and the symmetry properties of the current under spatial and temporal reflections.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 87–91, April, 1987. 相似文献
11.
V. V. Barmin A. E. Asratyan V. S. Borisov C. Curceanu G. V. Davidenko A. G. Dolgolenko C. Guaraldo M. A. Kubantsev I. F. Larin V. A. Matveev V. A. Shebanov N. N. Shishov L. I. Sokolov G. K. Tumanov V. S. Verebryusov 《Physics of Atomic Nuclei》2010,73(7):1164-1167
The data on the reactions K +Xe → K 0 γX and K +Xe → K + γX, obtained with the bubble chamber DIANA, have been analyzed for possible radiative decays of the Θ+(1540) baryon: Θ+ → K 0 pγ and Θ+ → K + nγ. No signals have been observed, and we derive the upper limits Γ(Θ+ → K 0 pγ)/Γ(Θ+ → K 0 p) < 0.032 and Γ(Θ+ → K + nγ)/Γ(Θ+ → K + nγ) < 0.041 which, using our previous measurement of Γ(Θ+ → KN) = 0.39 ± 0.10 MeV, translate to Γ(Θ+ → K 0 pγ) < 8 keV and Γ(Θ+ → K + nγ) < 11 keV at 90% confidence level. We have also measured the cross sections of K +-induced reactions involving emission of a neutral pion: σ(K + n → K 0 pπ 0) = 68 ± 18 µb and σ(K + N → K + Nπ 0) = 30 ± 8 µb for incident K + momentum of 640 MeV. 相似文献
12.
《Physics letters. [Part B]》1988,213(3):400-404
Excited electrons, e1's, have been searched for by making use of the processes e+e−→e+e−γγ and eγ(e) (quasi-real Compton scattering). From the former process, we have obtained the lower limit for the mass of e1', 27.9 GeV/c. A good agreement with QED is observed in the latter process, and new upper limits have been set for the coupling strength λ as a function of the mass of e1. 相似文献
13.
M. K. Volkov M. Nagy A. N. Ivanov N. I. Troitskaya 《Czechoslovak Journal of Physics》1989,39(11):1256-1262
In the special type of the quark model we obtain the ratio=h
A/hV of the axial (hA) and vector (hV) form factors for the decays – e– ¯ve and K– e–¯ve different from unity. The low-energy theorem, relating the electric polarizability of the charged pion with the ratio, is analyzed. It is shown that
< 1 corresponds to , calculated by accounting the contribution of the scalar meson(700) into the amplitude of the Compton effect on the pion. In the absence of the(700) contribution we have=1.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday. 相似文献
14.
Aaltonen T Adelman J Alvarez González B Amerio S Amidei D Anastassov A Annovi A Antos J Apollinari G Appel J Apresyan A Arisawa T Artikov A Asaadi J Ashmanskas W Attal A Aurisano A Azfar F Badgett W Barbaro-Galtieri A Barnes VE Barnett BA Barria P Bartos P Bauer G Beauchemin PH Bedeschi F Beecher D Behari S Bellettini G Bellinger J Benjamin D Beretvas A Bhatti A Binkley M Bisello D Bizjak I Blair RE Blocker C Blumenfeld B Bocci A Bodek A Boisvert V Bortoletto D Boudreau J Boveia A Brau B 《Physical review letters》2010,105(19):191801
We present a search for supersymmetric neutrino ν production using the Tevatron pp collision data collected with the CDF II detector and corresponding to an integrated luminosity of 1 fb-1. We focus on the scenarios predicted by the R-parity violating (RPV) supersymmetric models in which sneutrinos decay to two charged leptons of different flavor. With the data consistent with the standard model expectations, we set upper limits on σ(pp→ν)×BR(ν→eμ,μτ,eτ) and use these results to constrain the RPV couplings as a function of the sneutrino mass. 相似文献
15.
16.
In the supersymmetric left-right model, the light neutrino masses are given by the Type-Ⅱ seesaw mechanism. A duality property of this mechanism indicates that there exist eight possible Higgs triplet Yukawa couplings which result in the same neutrino mass matrix. In this paper, we work out the one-loop renormalization group equations for the effective neutrino mass matrix in the supersymmetric left-right model. The stability of the Type-Ⅱ seesaw scenario is briefly discussed. We also study the lepton-flavor-violating processes (τ→ μγ and τ→eγ) by using the reconstructed Higgs triplet Yukawa couplings. 相似文献
17.
CHAO Wei 《中国物理C(英文版)》2011,35(3)
In the supersymmetric left-right model,the light neutrino masses are given by the Type-II seesaw mechanism.A duality property of this mechanism indicates that there exist eight possible Higgs triplet Yukawa couplings which result in the same neutrino ma6s matrix.In this paper,we work out the one-loop renormalization group equations for the effective neutrino mass matrix in the supersymmetric left-right model.The stability of the Type-II seesaw scenario is briefly discussed.We also study the lepton-flavor-violating processes (τ→μγ and τ→eγ)by using the reconstructed Higgs triplet Yukawa couplings. 相似文献
18.
《Physics letters. [Part B]》1986,167(1):138-140
A new value of the upper limit for the branching ratio of the decay of K0S into e+e− has been experimentally obtained using a lead glass detector. The value is BR (K0S → e+e−) < 1.1 × 10−4 (90% CL). 相似文献
19.
R. Bernabei P. Belli F. Cappella R. Cerulli C. J. Dai A. d’Angelo H. L. He A. Incicchitti H. H. Kuang X. H. Ma F. Montecchia F. Nozzoli D. Prosperi X. D. Sheng Z. P. Ye 《The European Physical Journal C - Particles and Fields》2009,62(2):327-332
In this paper a new search for non-Paulian nuclear processes, i.e. processes normally forbidden by the Pauli Exclusion Principle
(PEP), is presented. It has been carried out at the Gran Sasso National Laboratory of the INFN by means of the highly radiopure
DAMA/LIBRA set-up (sensitive mass of about 250 kg highly radiopure NaI(Tl)). In particular, a new improved upper limit for
the spontaneous non-Paulian emission rate of protons with energy E
p
≥ 10 MeV in 23Na and 127I has been obtained: 1.63 × 10−33 s−1 (90% C.L.). The corresponding limit on the relative strength (δ
2) for the searched non-Paulian transition is δ
2≲(3–4)×10−55 (90% C.L.). Moreover, PEP-violating electron transitions in iodine atoms have also been investigated. Lifetimes shorter than
4.7×1030 s are excluded at 90% C.L.; this allows us to derive the limit δ
e
2<1.28×10−47 (90% C.L.). This latter limit can also be related to a possible finite size of the electron in composite models of quarks
and leptons providing superficial violation of the PEP; the obtained upper limit on the electron size is r
0<5.7×10−18 cm (energy scale of E≳3.5 TeV). 相似文献
20.
G. A. Akopdzhanov V. B. Anikeev V. A. Bezzubov I. A. Vasilyev Yu. V. Gilitsky S. N. Gurzhiev S. P. Denisov A. A. Durum S. A. Zvyagintsev A. V. Kozelov E. A. Kozlovsky V. M. Korablev V. I. Koreshev V. I. Kurbakov V. V. Lipaev V. A. Onuchin A. M. Rybin Yu. M. Sapunov M. M. Soldatov D. A. Stoyanova K. I. Trushin A. A. Schukin V. I. Yakimchuk 《Physics of Atomic Nuclei》2008,71(12):2074-2086
K ± → e ± νπ 0 decays have been studied using the KMN setup at the Institute for High Energy Physics (Protvino). The experiment has been performed in the 36-GeV/c hadron beams of the IHEP accelerator. The accumulated data allow us to select ~1.08M candidates for K e3 decays. Analyzing the Dalitz plot of these events, we estimate the linear slope of the charge form factor to be λ + = [30.44 ± 0.83(stat.) ± 0.74(syst.)] × 10?3. 相似文献