957 research outputs found

    Hadronic B Decays to Charmed Baryons

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    We study exclusive B decays to final states containing a charmed baryon within the pole model framework. Since the strong coupling for ΛbBˉN\Lambda_b\bar B N is larger than that for ΣbBˉN\Sigma_b \bar BN, the two-body charmful decay BΣc0pˉB^-\to\Sigma_c^0\bar p has a rate larger than Bˉ0Λc+pˉ\bar B^0\to\Lambda_c^+\bar p as the former proceeds via the Λb\Lambda_b pole while the latter via the Σb\Sigma_b pole. By the same token, the three-body decay Bˉ0Σc++pˉπ\bar B^0\to\Sigma_c^{++}\bar p\pi^- receives less baryon-pole contribution than BΛc+pˉπB^-\to\Lambda_c^+\bar p\pi^-. However, because the important charmed-meson pole diagrams contribute constructively to the former and destructively to the latter, Σc++pˉπ\Sigma_c^{++}\bar p\pi^- has a rate slightly larger than Λc+pˉπ\Lambda_c^+\bar p\pi^-. It is found that one quarter of the BΛc+pˉπB^-\to \Lambda_c^+\bar p\pi^- rate comes from the resonant contributions. We discuss the decays Bˉ0Σc0pˉπ+\bar B^0\to\Sigma_c^0\bar p\pi^+ and BΣc0pˉπ0B^-\to\Sigma_c^0\bar p\pi^0 and stress that they are not color suppressed even though they can only proceed via an internal W emission.Comment: 25 pages, 6 figure

    Study of f_0(980) and f_0(1500) from B_s \to f_0(980)\pi, f_0(1500)\pi Decays

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    In this paper, we analyze the scalar mesons f0(980)f_0(980) and f0(1500)f_0(1500) from the decays Bˉs0f0(980)π0,f0(1500)π0\bar B^0_s \to f_0(980)\pi^0, f_0(1500)\pi^0 within Perturbative QCD approach. From the leading order calculations, we find that (a) in the allowed mixing angle ranges, the branching ratio of Bˉs0f0(980)π0\bar B^0_s\to f_0(980)\pi^0 is about (1.01.6)×107(1.0\sim1.6)\times 10^{-7}, which is smaller than that of Bˉs0f0(980)K0\bar B^0_s\to f_0(980)K^0 (the difference is a few times even one order); (b) the decay Bˉs0f0(1500)π0\bar B^0_s \to f_0(1500)\pi^0 is better to distinguish between the lowest lying state or the first excited state for f0(1500)f_0(1500), because the branching ratios for two scenarios have about one-order difference in most of the mixing angle ranges; and (c) the direct CP asymmetries of Bˉs0f0(1500)π0\bar B^0_s \to f_0(1500)\pi^0 for two scenarios also exists great difference. In scenario II, the variation range of the value ACPdir(Bˉs0f0(1500)π0){\cal A} ^{dir}_{CP}(\bar B^0_s \to f_0(1500)\pi^0) according to the mixing angle is very small, except for the values corresponding to the mixing angles being near 9090^\circ or 270270^\circ, while the variation range of ACPdir(Bˉs0f0(1500)π0){\cal A} ^{dir}_{CP}(\bar B^0_s \to f_0(1500)\pi^0) in scenario I is very large. Compared with the future data for the decay Bˉs0f0(1500)π0\bar B^0_s \to f_0(1500)\pi^0, it is ease to determine the nature of the scalar meson f0(1500)f_0(1500).Comment: 16 pages, 3 figures, Revte

    Impact of Subleading Corrections on Hadronic B Decays

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    We study the subleading corrections originating from the 3-parton (q\bar q g) Fock states of final-state mesons in B decays. The corrections could give significant contributions to decays involving an \omega or \eta^{(\prime)} in the final states. Our results indicate the similarity of \omega K and \omega \pi^- rates, of order 5\times 10^{-6}, consistent with the recent measurements. We obtain a_2(B\to J/\psi K)\approx 0.27+0.05i, in good agreement with data. Without resorting to the unknown singlet annihilation effects, 3-parton Fock state contributions can enhance the branching ratios of K\eta' to the level above 50\times 10^{-6}.Comment: 5 pages, 5 figures, revtex4; some typos corrected, a new figure and a reference added, more explanations for the calculation provided, to appear in Phys. Rev.

    Implications of Recent Measurements of Hadronic Charmless B Decays

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    Implications of recent CLEO measurements of hadronic charmless B decays are discussed. (i) Employing the Bauer-Stech-Wirbel (BSW) model for form factors as a benchmark, the Bπ+πB\to\pi^+\pi^- data indicate that the form factor F0Bπ(0)F_0^{B\pi}(0) is smaller than that predicted by the BSW model, whereas the data of Bωπ,KηB\to\omega\pi, K^*\eta imply that the form factors A0Bω(0),A0BK(0)A_0^{B\omega}(0), A_0^{BK^*}(0) are greater than the BSW model's values. (ii) The tree-dominated modes Bπ+π,ρ0π±,ωπ±B\to\pi^+\pi^-, \rho^0\pi^\pm, \omega\pi^\pm imply that the effective number of colors N_c(LL) for (V-A)(V-A) operators is preferred to be smaller, while the current limit on BϕKB\to\phi K shows that N_c(LR)>3. The data of BKηB\to K\eta' and KηK^*\eta clearly indicate that Nc(LR)Nc(LL)N_c(LR)\gg N_c(LL). (iii) In order to understand the observed suppression of π+π\pi^+\pi^- and non-suppression of KπK\pi modes, both being governed by the form factor F0BπF_0^{B\pi}, the unitarity angle γ\gamma is preferred to be greater than 9090^\circ. By contrast, the new measurement of B±ρ0π±B^\pm\to\rho^0\pi^\pm no longer strongly favors cosγ<0\cos\gamma<0. (iv) The observed pattern K^-\pi^+\sim \ov K^0\pi^-\sim {2\over 3}K^-\pi^0 is consistent with the theoretical expectation: The constructive interference between electroweak and QCD penguin diagrams in the Kπ0K^-\pi^0 mode explains why {\cal B}(B^-\to K^-\pi^0)>{1\over 2}{\cal B}(\ov B^0\to K^-\pi^+). (v) The observation \nc(LL)<3<\nc(LR) and our preference for \nc(LL)\sim 2 and \nc(LR)\sim 6 are justified by a recent perturbative QCD calculation of hadronic rare B decays in the heavy quark limit.Comment: 21 pages; CLEO measurements of several charmless B decay modes are updated. Discussion of the unitarity angle gamma in the \rho\pi mode is revise

    The lifetime of B_c-meson and some relevant problems

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    The lifetime of the B_c-meson is estimated with consistent considerations on all of the heavy mesons (B0,B±,Bs,D0,D±DsB^0, B^\pm, B_s, D^0, D^\pm D_s) and the double heavy meson B_c. In the estimate, the framework, where the non-spectator effects for nonleptonic decays are taken into account properly, is adopted, and the parameters needed to be fixed are treated carefully and determined by fitting the available data. The bound-state effects in it are also considered. We find that in decays of the meson B_c, the QCD correction terms of the penguin diagrams and the main component terms c_1O_1, c_2O_2 of the effective interaction Lagrangian have direct interference that causes an enhancement about 3 ~ 4% in the total width of the B_c meson.Comment: 27 pages, 0 figur

    Light-Front Approach for Heavy Pentaquark Transitions

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    Assuming the two diquark structure for the pentaquark state as advocated in the Jaffe-Wilczek model, there exist exotic parity-even anti-sextet and parity-odd triplet heavy pentaquark baryons. The theoretical estimate of charmed and bottom pentaquark masses is quite controversial and it is not clear whether the ground-state heavy pentaquark lies above or below the strong-decay threshold. We study the weak transitions of heavy pentaquark states using the light-front quark model. In the heavy quark limit, heavy-to-heavy pentaquark transition form factors can be expressed in terms of three Isgur-Wise functions: two of them are found to be normalized to unity at zero recoil, while the third one is equal to 1/2 at the maximum momentum transfer, in accordance with the prediction of the large-Nc approach or the quark model. Therefore, the light-front model calculations are consistent with the requirement of heavy quark symmetry. Numerical results for form factors and Isgur-Wise functions are presented. Decay rates of the weak decays Theta_b+ to Theta_c0 pi+ (rho+), Theta_c0 to Theta+ pi- (rho-), Sigma'_{5b}+ to Sigma'_{5c}0 pi+ (rho+) and Sigma'_{5c}0 to N_8+ pi- (rho-) with Theta_Q, Sigma'_{5Q} and N_8 being the heavy anti-sextet, heavy triplet and light octet pentaquarks, respectively, are obtained. For weakly decaying Theta_b+ and Theta_c0, the branching ratios of Theta_b+ to Theta_c0 pi+, Theta_c0 to Theta+ pi- are estimated to be at the level of 10^{-3} and a few percents, respectively.Comment: 33 pages, 3 figures, version to be published in Phys. Rev.

    Asymmetry Parameter of the K1(1270,1400)K_{1} (1270, 1400) by Analyzing the BK1ννˉB\to K_{1}\nu \bar{\nu} Transition Form Factors within QCD

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    Separating the mixture of the K1(1270) K_{1}(1270) and K1(1400)K_{1}(1400) states, the BK1(1270,1400)ννˉB\to K_{1}(1270, 1400)\nu\bar{\nu} transition form factors are calculated in the three-point QCD sum rules approach. The longitudinal, transverse and total decay widths as well as the asymmetry parameter, characterizing the polarization of the axial K1(1270,1400)K_{1}(1270, 1400) and the branching ratio for these decays are evaluated.Comment: 25 pages, 3 figures, 3 table

    Hadronic Charmed Meson Decays Involving Axial Vector Mesons

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    Cabibbo-allowed charmed meson decays into a pseudoscalar meson and an axial-vector meson are studied. The charm to axial-vector meson transition form factors are evaluated in the Isgur-Scora-Grinstein-Wise quark model. The dipole momentum dependence of the DKD\to K transition form factor and the presence of a sizable long-distance WW-exchange are the two key ingredients for understanding the data of DKˉa1D\to \bar Ka_1. The K1AK1BK_{1A}-K_{1B} mixing angle of the strange axial-vector mesons is found to be ±37\approx \pm37^\circ or ±58\pm58^\circ from τK1ντ\tau\to K_1\nu_\tau decays. The study of DK1(1270)π,K1(1400)πD\to K_1(1270)\pi, K_1(1400)\pi decays excludes the positive mixing-angle solutions. It is pointed out that an observation of the decay D0K1(1400)π+D^0\to K_1^-(1400)\pi^+ at the level of 5×1045\times 10^{-4} will rule out θ37\theta\approx -37^\circ and favor the solution θ58\theta\approx -58^\circ. Though the decays D0Kˉ10π0D^0\to \bar K_1^0\pi^0 are color suppressed, they are comparable to and even larger than the color-allowed counterparts: Kˉ10(1270)π0K1(1270)π+\bar K_1^0(1270)\pi^0\sim K_1^-(1270)\pi^+ and Kˉ10(1400)π0>K1(1400)π+\bar K_1^0(1400)\pi^0> K_1^-(1400)\pi^+. The finite width effect of the axial-vector resonance is examined. It becomes important for a1(1260)a_1(1260) in particular when its width is near 600 MeV.Comment: 19 page
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