共查询到20条相似文献,搜索用时 31 毫秒
1.
An effective quark-gluon-photon operator is considered as the mechanism for radiative weak decays of hyperons. The coefficient function is unsuppressed by GIM cancellations, suggesting a significant decay rate, and a substantial amount of parity violation (large decay asymmetry) is expected. Attempted model calculations confirm this last feature but fail to provide an adequate absolute decay rate. 相似文献
2.
Xue-qian LI 《理论物理通讯》1988,9(1):89-108
We calculate the rates and asymmetry parameters of radiative hyperon decays based on the hybrid structure of hyperons.We exploit an effective Hamiltonian derived from a penguin-Like Feynman diagram. We also consider a model of a static mean gluon field. A plausible recoil effect is taken into account in the final results. The resultant asymmetry parameters are reasonably consistent with data. 相似文献
3.
The purely leptonic decays of the tau and the radiative decay of the pion provide determinations of the tau neutrino and muon neutrino masses, respectively. The shift of the energy at which the tau decay spectrum attains its maximum and the forward-backward ratio are both large enough to determine tau neutrino masses of about 100 MeV. The photon endpoint energy and partially integrated differential decay rate in pion decay are sensitive to a neutrino mass as small as 100 keV. Thus, the present bounds on neutrino masses can be significantly improved. 相似文献
4.
Robert L. Thews 《Physics letters. [Part B]》1976,65(4):343-345
It is noted that recent experiments on φ decays indicate a suppression of the radiative decay by about a factor of 3 less than the vector-meson-dominance model predictions. FESR's on pion compton scattering amplitudes with identical t-channels but different direct channel resonances are shown to relate radiative decays of A2 and ω. This again leads to a suppression factor of 3 to 4 for the A2 radiative decay relative to the VMD prediction. 相似文献
5.
Luk KB Diehl HT Duryea J Guglielmo G Heller K Ho PM James C Johns K Longo MJ Rameika R Teige S Thomson GB Zou Y 《Physical review letters》2000,85(23):4860-4863
A search for direct CP violation in the nonleptonic decays of hyperons has been performed. In comparing the product of the decay parameters, alpha(Xi)alpha(Lambda), in terms of an asymmetry parameter, A(XiLambda), between hyperons and antihyperons in the charged Xi-->Lambdapi and Lambda-->ppi decay sequence, we found no evidence of direct CP violation. The parameter A(XiLambda) was measured to be 0.012+/-0.014. 相似文献
6.
We propose a way of measuring the photon polarization in radiative B decays into K resonance states decaying to Kpipi, which can test the standard model and probe new physics. The photon polarization is shown to be measured by the up-down asymmetry of the photon direction relative to the Kpipi decay plane in the K resonance rest frame. The integrated asymmetry in K1(1400)-->Kpipi, calculated to be 0.34 plus/minus 0.05 in the standard model, is measurable at currently operating B factories. 相似文献
7.
We study in the one-loop approximation the decays of the pion and the pion electromagnetic form factor at low q2 in the framework of a σ-model with quarks. The theory has a free parameters the quark and σ masses and the results are very insensitive to their values. We get good approximation for all processes considered except for the ratio of the axial to the vector form factor that appear in the electronic radiative decay of the charged pion. The reason is probably that our model includes the pion-pion interaction only in the isoscalar s-wave at the one-loop level. 相似文献
8.
We have studied the radiative corrections to the lepton energy spectrum in semileptonic hyperon decays. The calculation is performed relativistically for the baryons as well as for the leptons, under the assumption of the effective current-current interaction of the V-?A type for the baryonic part. We obtain the explicit formula of radiative corrections to the lepton energy spectrum which we can exactly evaluate in case of charged hyperon decays. Numerical values of the radiative corrections to the decays rate and the shape of the lepton energy spectrum are also given for some decay modes. It is shown that the spectral shape is little affected by the radiative corrections. 相似文献
9.
Aushev T Iwasaki Y Abe K Abe K Adachi I Aihara H Akatsu M Asano Y Aziz T Bahinipati S Bakich AM Bay A Bedny I Bitenc U Bizjak I Blyth S Bondar A Bozek A Bracko M Brodzicka J Chang P Chao Y Chen A Chen WT Cheon BG Chistov R Choi Y Chuvikov A Danilov M Dash M Dong LY Dragic J Drutskoy A Eidelman S Eiges V Enari Y Fang F Fratina S Gabyshev N Garmash A Gershon T Gokhroo G Golob B Hastings NC Hayasaka K Hazumi M Higuchi T Hinz L Hokuue T Hoshi Y Hou S Hou WS Iijima T Imoto A Inami K Ishikawa A 《Physical review letters》2004,93(20):201802
We report a search for CP-violating asymmetry in B0-->D(*+/-)D-/+ decays. The analysis employs two methods of B0 reconstruction: full and partial. In the full reconstruction method all daughter particles of the B0 are required to be detected; the partial reconstruction technique requires a fully reconstructed D- and only a slow pion from the D(*+)-->D0pi(+)(slow) decay. From a fit to the distribution of the time interval corresponding to the distance between two B meson decay points we calculate the CP-violating parameters and find the significance of nonzero CP asymmetry to be 2.7 standard deviations. 相似文献
10.
Rene Unterdorfer Hannes Pichl 《The European Physical Journal C - Particles and Fields》2008,55(2):273-283
A reanalysis of the radiative pion decay together with the calculation of the radiative corrections within chiral perturbation
theory (CHPT) is performed. The amplitude of this decay contains an inner Bremsstrahlung contribution and a structure-dependent
part, which are both accessible in experiments. In order to obtain a reliable estimate of the hadronic contributions we combine
the CHPT result with a large-Nc expansion and experimental data on other decays, which makes it possible to determine the occurring coupling constants.
PACS 13.20.Cz; 12.39.Fe 相似文献
11.
The dependence of inclusive weak decay rates of heavy hadrons on the flavors of spectator light quarks is revisited with application to decays of charmed and b hyperons. It is pointed out that the differences in the semileptonic decay rates, the differences in the Cabibbo-suppressed decay rates of the charmed hyperons, and the splitting of the total decay rates of the b hyperons are all related to the differences in the lifetimes of the charmed hyperons independently of poor knowledge of hadronic matrix elements. The approximations used in these relations are the applicability of the expansion in the inverse of the charmed quark mass and the flavor SU(3) symmetry. 相似文献
12.
In detail we analyse possible ways for measuring the hidden phase in ΔS=1 weak, radiative decays of hyperons and have found that any measurement on the kinematic quantities of the decays cannot determine the phase. The only possibility is to measure the CP non-invariannce in decays, even though it is very difficult. Our analysis is fully model-independent. 相似文献
13.
Peter Truöl 《Czechoslovak Journal of Physics》1991,41(11):1061-1073
Experimental data on pion-proton bremsstrahlung, radiative pion decay and radiative muon capture are reviewed to demonstrate that the study of intermediate energy bremsstrahlung processes can reveal additional information on hadron structure inaccessible in their non-radiative counterparts.Dedicated to the memory of M. Gmitro. 相似文献
14.
F.P. Calaprice D.F. Schreiber M.B. Schneider M. Green R.E. Pollock 《Physics letters. [Part B]》1981,106(3):175-178
If neutrinos possess non-zero mass, pion decay might have small decay branches to neutrino states with large masses. We have searched for such branches in the decay of pions produced at the Indiana University Cyclotron. The energy spectrum of decay muons shows no evidence for such neutrino branches and if these decays do exist, their branching ratios must be less than 10?2 to 10?3 for neutrino masses in the ranFge 7–33 MeV. 相似文献
15.
《Nuclear Physics B》1986,263(2):475-492
Feynman diagram calculations are considerably simpler in the framework of Weyl-Van der Waerden spinors than in the standard formalism. We collect the basic formulae and illustrate the method by a few examples. We study pion pair decay in considerable detail and find that the long-standing ambiguity in determining the ratio of axial vector to vector structure term that hampered pion radiative decay can be resolved in the pair decay. 相似文献
16.
Nils Dalarsson 《International Journal of Theoretical Physics》1998,37(3):1067-1080
We suggest a quantum stabilization method forthe SU(2) -model, based on the constant-cutofflimit of the cutoff quantization method developed byBalakrishna et al., which avoids the difficulties with the usual soliton boundary conditions pointedout by Iwasaki and Ohyama. We investigate the baryonnumber B = 1 sector of the model and show that after thecollective-coordinate quantization it admits a stable soliton solution which depends on asingle dimensional arbitrary constant. We then study theradiative decays of J = 3+/2 baryonsusing the constant-cutoff approach to the SU(3)collective treatment of the Skyrme model for hyperons. Thus weinvestigate the radiative hyperon decays and thevariation of the decay widths with strangeness, showingthat the present results are in qualitative agreementwith the results obtained using the complete Skyrmemodel. 相似文献
17.
Sato Y Yamamoto H Aihara H Asner DM Aulchenko V Aushev T Aziz T Bakich AM Bhardwaj V Bhuyan B Bischofberger M Bondar A Bozek A Bračko M Browder TE Chang P Chen P Cheon BG Chilikin K Chistov R Cho IS Cho K Choi SK Choi Y Dalseno J Doležal Z Drásal Z Eidelman S Epifanov D Fast JE Gaur V Gabyshev N Goh YM Golob B Haba J Hara T Hayasaka K Hayashii H Horii Y Hoshi Y Hou WS Hyun HJ Ishikawa A Itoh R Iwabuchi M Iwasaki Y Iwashita T Julius T Kapusta P Kawasaki T Kichimi H Kiesling C Kim HJ Kim HO 《Physical review letters》2012,108(17):171801
We report a measurement of the CP-violation parameter sin2φ1 at the Υ(5S) resonance using a new tagging method, called "B-π tagging." In Υ(5S) decays containing a neutral B meson, a charged B, and a charged pion, the neutral B is reconstructed in the J/ψK(S)(0) CP-eigenstate decay channel. The initial flavor of the neutral B meson at the moment of the Υ(5S) decay is opposite to that of the charged B and may thus be inferred from the charge of the pion without reconstructing the charged B. From the asymmetry between B-π(+) and B-π(-) tagged J/ψK(S)(0) yields, we determine sin2φ1=0.57±0.58(stat)±0.06(syst). The results are based on 121 fb(-1) of data recorded by the Belle detector at the KEKB e(+)e(-) collider. 相似文献
18.
H.J. Lipkin 《Physics letters. [Part B]》1985,151(2):155-160
Sum rules previously derived for proton decay are extended and applied to treat effects of bound states spectroscopy on radiative quarkonium decays. The transition involves boson (photon or pion) emission followed by quark annihilation. Sum rules for the contributions from different intermediate bound states are derived by using closure and the assumptions (1) that the boson emission is described by a plane wave or multipole operator which satisfies a wave equation, and (2) that the annihilation depends on the bound state wave function or its derivative at the origin. 相似文献
19.
K. Fujii H. Hayashii S. Iwata R. Kajikawa A. Miyamoto T. Nakanishi Y. Ohashi S. Okumi H. Ozaki T. Tauchi T. Yamaki K. Mori Y. Takeuchi 《Nuclear Physics B》1981,187(1):53-70
The polarized target asymmetry for γn→π?p was measured over the second resonance region from 0.55 to 0.9 GeV at pion c.m. angles between 60° and 120°. A double-arm spectrometer was used with a deuterated butanol target to detect both the pion and the proton, thus considerably improving the data quality. Including the new data in the amplitude analysis, the radiative decay widths of three resonances were determined more accurately than before. The results are compared with various quark models. 相似文献
20.
W. A. Perkins 《International Journal of Theoretical Physics》2008,47(5):1316-1321
Long ago an unexpected and unexplainable phenomena was observed. The distribution of muons from positive pion decay at rest
was anisotropic with an excess in the backward direction relative to the direction of the proton beam from which it was produced.
Although this effect was observed by several different groups with pions produced by different means and detected by different
methods, the result was not accepted by the physics community, because it is in direct conflict with a large set of other
experiments indicating that the pion is a pseudoscalar particle. It is possible to satisfy both sets of experiments if helicity-zero
vector particles exist and the pion is such a particle. Helicity-zero vector particles have direction but no net spin. For
the neutral pion to be a vector particle requires an additional modification to conventional theory as discussed herein. An
experiment is proposed which can prove that the asymmetry in the distribution of muons from pion decay is a genuine physical
effect because the asymmetry can be modified in a controllable manner. A positive result will also prove that the pion is
not a pseudoscalar particle. 相似文献