403 research outputs found

    Charm multiplicity and the branching ratios of inclusive charmless b quark decays in the general two-Higgs-doublet models

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    In the framework of general two-Higgs-doublet models, we calculate the branching ratios of various inclusive charmless b decays by using the low energy effective Hamiltonian including next-to-leading order QCD corrections, and examine the current status and the new physics effects on the determination of the charm multiplicity ncn_c and semileptonic branching ratio BSLB_{SL}. Within the considered parameter space, the enhancement to the ratio BR(bsg)BR(b \to s g) due to the charged-Higgs penguins can be as large as a factor of 8 (3) in the model III (II), while the ratio BR(bnocharm)BR(b \to no charm) can be increased from the standard model prediction of 2.49% to 4.91% (2.99%) in the model III (II). Consequently, the value of BSLB_{SL} and ncn_c can be decreased simultaneously in the model III. The central value of BSLB_{SL} will be lowered slightly by about 0.003, but the ratio ncn_c can be reduced significantly from the theoretical prediction of nc=1.28±0.05n_c= 1.28 \pm 0.05 in the SM to nc=1.23±0.05n_c= 1.23 \pm 0.05, 1.18±0.051.18 \pm 0.05 for mH+=200,100m_{H^+}=200, 100 GeV, respectively. We find that the predicted ncn_c and the measured ncn_c now agree within roughly one standard deviation after taking into account the effects of gluonic charged Higgs penguins in the model III with a relatively light charged Higgs boson.Comment: 25 pages, Latex file, axodraw.sty, 6 figures. Final version to be published in Phys.Rev.

    Observation of Two New N* Peaks in J/psi -> ppinˉp pi^- \bar n and pˉπ+n\bar p\pi^+n Decays

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    The πN\pi N system in decays of J/ψNˉNπJ/\psi\to\bar NN\pi is limited to be isospin 1/2 by isospin conservation. This provides a big advantage in studying NπNN^*\to \pi N compared with πN\pi N and γN\gamma N experiments which mix isospin 1/2 and 3/2 for the πN\pi N system. Using 58 million J/ψJ/\psi decays collected with the Beijing Electron Positron Collider, more than 100 thousand J/ψpπnˉ+c.c.J/\psi \to p \pi^- \bar n + c.c. events are obtained. Besides two well known NN^* peaks at 1500 MeV and 1670 MeV, there are two new, clear NN^* peaks in the pπp\pi invariant mass spectrum around 1360 MeV and 2030 MeV. They are the first direct observation of the N(1440)N^*(1440) peak and a long-sought "missing" NN^* peak above 2 GeV in the πN\pi N invariant mass spectrum. A simple Breit-Wigner fit gives the mass and width for the N(1440)N^*(1440) peak as 1358±6±161358\pm 6 \pm 16 MeV and 179±26±50179\pm 26\pm 50 MeV, and for the new NN^* peak above 2 GeV as 2068±340+152068\pm 3^{+15}_{-40} MeV and 165±14±40165\pm 14\pm 40 MeV, respectively

    Charmless hadronic decays BPP,PV,VVB \to PP, PV, VV and new physics effects in the general two-Higgs doublet models

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    Based on the low-energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to the branching ratios of the two-body charmless hadronic decays of BuB_u and BdB_d mesons induced by the new gluonic and electroweak charged-Higgs penguin diagrams in the general two-Higgs doublet models (models I, II and III). Within the considered parameter space, we find that: (a) the new physics effects from new gluonic penguin diagrams strongly dominate over those from the new γ\gamma- and Z0Z^0- penguin diagrams; (b) in models I and II, new physics contributions to most studied B meson decay channels are rather small in size: from -15% to 20%; (c) in model III, however, the new physics enhancements to the penguin-dominated decay modes can be significant, (30200)\sim (30 -200)%, and therefore are measurable in forthcoming high precision B experiments; (d) the new physics enhancements to ratios {\cal B}(B \to K \etap) are significant in model III, (3570)\sim (35 -70)%, and hence provide a simple and plausible new physics interpretation for the observed unexpectedly large B \to K \etap decay rates; (e) the theoretical predictions for B(BK+π){\cal B}(B \to K^+ \pi) and B(BK0π+){\cal B}(B \to K^0 \pi^+) in model III are still consistent with the data within 2σ2\sigma errors; (f) the significant new physics enhancements to the branching ratios of BK0π0,Kη,K+π,K+ϕ,K0ω,K+ϕB \to K^0 \pi^0, K^* \eta, K^{*+} \pi^-, K^+ \phi, K^{*0} \omega, K^{*+} \phi and K0ϕK^{*0} \phi decays are helpful to improve the agreement between the data and the theoretical predictions; (g) the theoretical predictions of B(BPP,PV,VV){\cal B}(B \to PP, PV, VV) in the 2HDM's are generally consistent with experimental measurements and upper limits (9090% C.L.)Comment: 55 pages, Latex file, 17 PS and EPS figures. With minor corrections, final version to be published in Phys.Rev. D. Repot-no: PKU-TH-2000-4

    Search for Invisible Decays of η\eta and η\eta^\prime in J/ψϕηJ/\psi \to \phi\eta and ϕη\phi \eta^\prime

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    Using a data sample of 58×10658\times 10^6 J/ψJ/\psi decays collected with the BES II detector at the BEPC, searches for invisible decays of η\eta and η\eta^\prime in J/ψJ/\psi to ϕη\phi\eta and ϕη\phi\eta^\prime are performed. The ϕ\phi signals, which are reconstructed in K+KK^+K^- final states, are used to tag the η\eta and η\eta^\prime decays. No signals are found for the invisible decays of either η\eta or η\eta^\prime, and upper limits at the 90% confidence level are determined to be 1.65×1031.65 \times 10^{-3} for the ratio B(ηinvisible)B(ηγγ)\frac{B(\eta\to \text{invisible})}{B(\eta\to\gamma\gamma)} and 6.69×1026.69\times 10^{-2} for B(ηinvisible)B(ηγγ)\frac{B(\eta^\prime\to \text{invisible})}{B(\eta^\prime\to\gamma\gamma)}. These are the first searches for η\eta and η\eta^\prime decays into invisible final states.Comment: 5 pages, 4 figures; Added references, Corrected typo

    B_c meson rare decays in the light-cone quark model

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    We investigate the rare decays BcDs(1968)ˉB_c \rightarrow D_s(1968) \ell \bar{\ell} and BcDs(2317)ˉB_c\rightarrow D_s^*(2317) \ell \bar{\ell} in the framework of the light-cone quark model (LCQM). The transition form factors are calculated in the space-like region and then analytically continued to the time-like region via exponential parametrization. The branching ratios and longitudinal lepton polarization asymmetries (LPAs) for the two decays are given and compared with each other. The results are helpful to investigating the structure of BcB_c meson and to testing the unitarity of CKM quark mixing matrix. All these results can be tested in the future experiments at the LHC.Comment: 9 pages, 11 figures, version accepted for publication in EPJ

    Measurements of the Mass and Full-Width of the ηc\eta_c Meson

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    In a sample of 58 million J/ψJ/\psi events collected with the BES II detector, the process J/ψγηc\psi\to\gamma\eta_c is observed in five different decay channels: γK+Kπ+π\gamma K^+K^-\pi^+\pi^-, γπ+ππ+π\gamma\pi^+\pi^-\pi^+\pi^-, γK±KS0π\gamma K^\pm K^0_S \pi^\mp (with KS0π+πK^0_S\to\pi^+\pi^-), γϕϕ\gamma \phi\phi (with ϕK+K\phi\to K^+K^-) and γppˉ\gamma p\bar{p}. From a combined fit of all five channels, we determine the mass and full-width of ηc\eta_c to be mηc=2977.5±1.0(stat.)±1.2(syst.)m_{\eta_c}=2977.5\pm1.0 ({stat.})\pm1.2 ({syst.}) MeV/c2c^2 and Γηc=17.0±3.7(stat.)±7.4(syst.)\Gamma_{\eta_c} = 17.0\pm3.7 ({stat.})\pm7.4 ({syst.}) MeV/c2c^2.Comment: 9 pages, 2 figures and 4 table. Submitted to Phys. Lett.

    A Measurement of Psi(2S) Resonance Parameters

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    Cross sections for e+e- to hadons, pi+pi- J/Psi, and mu+mu- have been measured in the vicinity of the Psi(2S) resonance using the BESII detector operated at the BEPC. The Psi(2S) total width; partial widths to hadrons, pi+pi- J/Psi, muons; and corresponding branching fractions have been determined to be Gamma(total)= (264+-27) keV; Gamma(hadron)= (258+-26) keV, Gamma(mu)= (2.44+-0.21) keV, and Gamma(pi+pi- J/Psi)= (85+-8.7) keV; and Br(hadron)= (97.79+-0.15)%, Br(pi+pi- J/Psi)= (32+-1.4)%, Br(mu)= (0.93+-0.08)%, respectively.Comment: 8 pages, 6 figure

    Partial wave analysis of J/\psi \to \gamma \phi \phi

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    Using 5.8×107J/ψ5.8 \times 10^7 J/\psi events collected in the BESII detector, the radiative decay J/ψγϕϕγK+KKS0KL0J/\psi \to \gamma \phi \phi \to \gamma K^+ K^- K^0_S K^0_L is studied. The ϕϕ\phi\phi invariant mass distribution exhibits a near-threshold enhancement that peaks around 2.24 GeV/c2c^{2}. A partial wave analysis shows that the structure is dominated by a 0+0^{-+} state (η(2225)\eta(2225)) with a mass of 2.240.02+0.030.02+0.032.24^{+0.03}_{-0.02}{}^{+0.03}_{-0.02} GeV/c2c^{2} and a width of 0.19±0.030.04+0.060.19 \pm 0.03^{+0.06}_{-0.04} GeV/c2c^{2}. The product branching fraction is: Br(J/ψγη(2225))Br(η(2225)ϕϕ)=(4.4±0.4±0.8)×104Br(J/\psi \to \gamma \eta(2225))\cdot Br(\eta(2225)\to \phi\phi) = (4.4 \pm 0.4 \pm 0.8)\times 10^{-4}.Comment: 11 pages, 4 figures. corrected proof for journa
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