共查询到20条相似文献,搜索用时 15 毫秒
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Thomas Becher Stephan Braig Matthias Neubert Alexander L. Kagan 《Physics letters. [Part B]》2002,540(3-4):278-288
The presence of a light
squark (
GeV) and gluino (
GeV) might explain the observed excess in b-quark production at the Tevatron. Though provocative, this model is not excluded by present data. The light supersymmetric particles can induce large flavor-changing effects in radiative decays of B mesons. We analyze the decays B→Xsγ and B→Xsg in this scenario and derive restrictive bounds on the flavor-changing quark–squark–gluino couplings. 相似文献
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Using the diquark model and a model of flavour dependent non-perturbative quark pari creation we calculate the exclusive baryonic decay rates of bottom mesons into baryon-antibaryon pairs. 相似文献
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We study the effects of mass-averaging over the width of the ρ-meson on branching ratios ofD/D s→VV decays. This smearing effect ensures lowering of these ratios in the required direction by about 15–25%, and enables us to choose the form-factorA 1(0)=0.6, thereby giving a good agreement with experimental results. We calculate the smeared branchings for the Cabibbo-enhanced and-suppressedD→VV decays in the presence of final state interactions. 相似文献
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V.L. Highland M. Salomon M.D. Hasinoff E. Mazzucato D.F. Measday J.-M. Poutissou T. Suzuki 《Nuclear Physics A》1981,365(3):333-348
The ratios has been measured for negative pions stopping in deuterium gas at pressures up to 100 atm. The result is S = 2.83 ± 0.04 which is a factor of two more accurate than previous measurements. 相似文献
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A vast body of experimental data accumulated in the past few years in hadronic Z 0 decays allows one to check quark-combinatorics relations for a new type of processes-namely, quark jets in the decays Z 0 → $q\bar q$ → hadrons. In this paper, we review quark-combinatorics rules for the yields of vector and pseudoscalar mesons, V/P, in the central and fragmentation regions of hadronic Z 0 decays. It is emphasized that, in the central region, a direct verification of quark-combinatorics rules is rather problematic because of a considerable background associated with the decay of highly excited resonances; however, such a verification is possible in the fragmentation region, at x hadron~0.5–1, where the contribution of resonance decays is suppressed owing to a fast decrease of the spectra with increasing x hadron. It is shown that, in the fragmentation region, experimental data on ρ0/π0 and p/π+ are in reasonable agreement with the predictions of quark combinatorics. The ratios of the heavy-meson yields, B*/B and D*/D, are also discussed: the data demonstrate good agreement with the quark combinatorial results. We analyze the structure of the suppression parameters for strange-and heavy-quark production in soft processes and estimate their orders of magnitude in multiperipheral processes; the ratio K ±/π± at x hadron~0.5–0.8 and the production probabilities for $c\bar c$ and $b\bar b$ mesons are in good agreement with the estimates. 相似文献
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Binding-energy spectra obtained using the dipole (e, 2e) electron impact coincidence method have been used to derive the 3s/3p cross-section ratios for the photoionization of argon up to 75 eV. The 3s and 3p photoionization branching ratios have been obtained by making use of recently determined double photoionization yields. The partial photoionization cross-section (oscillator strength) for 3s ionization, obtained using the branching ratio and the known total photoionization cross-section, shows the deep minimum ca. 10 eV above threshold which has been predicted by those theoretical calculations which include electron correlation effects. Below 50 eV the cross-section is in excellent agreement with the SRPAE calculation. The results are in close agreement with recent measurements made using synchrotron radiation but are consistently smaller below the minimum and larger at the higher energies. 相似文献
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Alam MS Katayama N Kim IJ Sun CR Tanikella V Bortoletto D Chen A Goldberg M Holmes R Horwitz N Jawahery A Lubrano P Moneti GC Sharma V Thoma P Csorna SE Mestayer MD Panvini RS Word GB Bean A Bobbink GJ Brock IC Engler A Ferguson T Kraemer RW Rippich C Vogel H Bebek C Berkelman K Blucher E Cassel DG Copie T DeSalvo R DeWire JW Ehrlich R Galik RS Gilchriese MG Gittelman B Gray SW Halling AM Hartill DL Heltsley BK Holzner S Ito M Kandaswamy J Kowalewski R Kreinick DL Kubota Y Mistry NB Mueller J 《Physical review letters》1987,58(18):1814-1817
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Owing to the significant difference between the experimental measurements and the theoretical predictions of the standard model (SM) for the value of \begin{document}$ {\cal{R}}(D) $\end{document} ![]()
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of the semileptonic decay \begin{document}$ B\to D\ell\bar{\nu}_{\ell} $\end{document} ![]()
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, researchers speculate that this decay may be evidence of new physics beyond the SM. Usually, the D-meson twist-2, 3 distribution amplitudes (DAs) \begin{document}$ \phi_{2;D}(x,\mu) $\end{document} ![]()
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, \begin{document}$ \phi_{3;D}^p(x,\mu) $\end{document} ![]()
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, and \begin{document}$ \phi_{3;D}^\sigma(x,\mu) $\end{document} ![]()
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are the main error sources when perturbative QCD factorization and light-cone QCD sum rules are used to study \begin{document}$ B\to D\ell\bar{\nu}_{\ell} $\end{document} ![]()
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. Therefore, it is important to obtain more reasonable and accurate behaviors for these DAs. Motivated by our previous work [Phys. Rev. D 104, no.1, 016021 (2021)] on pionic leading-twist DA, we revisit D-meson twist-2, 3 DAs \begin{document}$ \phi_{2;D}(x,\mu) $\end{document} ![]()
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, \begin{document}$ \phi_{3;D}^p(x,\mu) $\end{document} ![]()
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, and \begin{document}$ \phi_{3;D}^\sigma(x,\mu) $\end{document} ![]()
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. New sum rule formulae for the \begin{document}$\xi $\end{document} ![]()
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-moments of these three DAs are suggested for obtaining more accurate values. The light-cone harmonic oscillator models for the DAs are improved, and their parameters are determined by fitting the values of ξ -moments via the least squares method. 相似文献
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We study the semileptonic branching fraction of the B-meson into the higher resonance of the charmed meson D** by using the Bjorken sum rule and the heavy quark effective theory (HQET). This sum rule and the current experiment of the B-meson semileptonic decay into D and D* predict that the branching ratio D**lνl is about 1.7%. This predicted value is larger than the value obtained by various models. 相似文献
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Nils Dalarsson 《International Journal of Theoretical Physics》1997,36(4):935-947
We suggest a quantum stabilization method for theSU(2) σ-model, based on the constant-cutoff limit of the cutoff quantization method developed by Balakrishnaet al., which avoids the difficulties with the usual soliton boundary conditions pointed out by Iwasaki and Ohyama. We investigate
the baryon numberB=1 sector of the model and show that after the collective coordinate quantization it admits a stable soliton solution which
depends on a single dimensional arbitrary constant. We then study the radiative decays ofJ
π=3/2+ baryons using the constant-cutoff approach to theSU(3) collective treatment of the Skyrme model for hyperons. Thus we evaluate the widths and E2/M1 ratios, showing that there
is a general qualitative agreement with the results obtained using the complete Skyrme model, as well as the nonrelativistic
quark model and quenched lattice model, for the total widths. 相似文献
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I.I. Bigi 《The European Physical Journal C - Particles and Fields》2002,24(2):271-274
The B factories are expected to provide huge samples of single B decay events with little background by reconstructing one of the B mesons produced in decays. This represents a new experimental paradigm: such samples will allow to make measurements of a quality previously
thought unrealistic. As example we discuss how absolute branching ratios for exclusive as well as inclusive charm baryon decays
can be extracted. One starts out by observing decays like as a signature for etc. and then exploits various correlations of the flavour of the B meson with the baryon number of the (anti)proton and other observables like the charge of a lepton, baryon number of another
baryon etc. An integrated luminosity of about 500 fb-1 as could be available by 2005 should be sufficient for the task.
Received: 21 December 2001 / Published online: 8 May 2002 相似文献
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A. Heister et al. 《The European Physical Journal C - Particles and Fields》2002,22(4):613-626
A measurement of the inclusive semileptonic branching ratios of b hadrons produced in Z decay is presented, using four million
hadronic events collected by the ALEPH detector from 1991 to 1995. Electrons and muons are selected opposite to b-tagged hemispheres.
Two different methods are explored to distinguish the contributions from direct and cascade decays to the total lepton yield. One is based on the lepton transverse momentum spectrum, the other makes use of the correlation
between the charge of the lepton and charge estimators built from tracks in the opposite hemisphere of the event. The latter
method reduces the dependence on the modelling of semileptonic b decays. The results obtained by averaging the two techniques
are
Received: 1 August 2001 / Published online: 14 December 2001 相似文献
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用BESⅠ的7.8×106J/ψ数据更为精确地测定了J/ψ→π03(π+π-)和J/ψ→ω2(π+π-)的分支比(Br(J/ψ→π03(π+π-))=(2.52±0.06±0.43)%,Br(J/ψ→π03(π+π-))=(1.31±0.09±0.21)%.同时对4π不变质量谱和ωππ不变质量谱进行研究分析,试图观察是否存在有兴趣的信号. 相似文献