Analysis of Bs→φμ+μ- decay within supersymmetry

Motivated by the rst measurement on B(B_s→φμ⁺μ^-) by the CDF Collaboration, we study the supersymmetric e ects in semi-leptonic B_s→φμ⁺μ^- decay. In our evaluations, we analyze the dependences of the dimuon invariant mass spectrum and the forward-backward asymmetry on relevant supersymmetric couplings in the MSSM with and without R-parity. The analyses show that the new experimental upper limits of B(B_s→φμ⁺μ^-)from the LHCb Collaboration could further improve the bounds on sneutrino exchange couplings and (δ_LL^u)₂₃ as well as (δ_LL,RR^u)₂₃ mass insertion couplings. In addition, within the allowed ranges of relevant couplings under the constraints from B(B_s→φμ⁺μ^-), B(B→K^(*)μ⁺μ^-) and (B_s→φμ⁺μ^-), the dimuon forward-backward asymmetry and the di erential dimuon forward-backward asymmetry of B_s→φμ⁺μ^-are highly sensitive to the squark exchange contribution and the (δ_LL^u)₂₃ mass insertion contribution. The results obtained in this work will be very useful in searching for supersymmetric signals at the LHC.     

The study of B→K()l+l- decays in family non-universal Z' models

In a combined investigation of B→K^(*)l⁺l^- decays, constraints on the related couplings in family non-universal Z' models are derived. We find that within the allowed parameter space, the recently observed forward-backward asymmetry in the B→K^(*)l⁺l^- decay can be explained by flipping the signs of the Wilson coefficients C₉^eff and C₁₀. With the obtained constraints, we also calculate the branching ratio of the B_s→μ⁺μ^- decay. The upper bound of our prediction is nearly an order of magnitude smaller than the upper bound given by the CDF Collaboration recently.     

Analysis of Λb→pK- and pπ- decays in a flavor changing Z' mode

In this paper, we calculate the branching ratios of Λ_b→pK^- and pπ^- decays in the avor changing Z' model. We nd that the branching ratios for these two decay modes are sensitive to the contributions of the Z' boson. For Λ_b→pK^- decay, if the left-handed couplings are equal to the right-handed couplings, the branching ratio of this decay could match up to the currently experimental data for ξ_s=0.01 and -52°<φ_s^L<132°, or ξ_s=0.004 and 0°<φ_s^L<84°; if only the left-handed couplings are considered, it could match up to the experimental data for ξ_s=0.01 and -10°φ_s^L<138°. And for Λ_b→pK^- decay, if the left-handed and right-handed couplings are equal, the branching ratio of Λ_b→pK^- decay may be consistent with the currently experimental data with ξ_d=0.05 and -135°φ_d^L<43°, if only the left-handed couplings are considered, it may be consistent with ξ_d=0.05 and -114°φ_d^L<8°.     

The study of B→K*l+l- decays in family non-universal Z′ models

In a combined investigation of B → K ( * ) l + l - decays, constraints on the related couplings in family non-universal Z′ models are derived. We find that within the allowed parameter space, the recently observed forward-backward asymmetry in the B → K * l + l - decay can be explained by flipping the signs of the Wilson coefficients C eff 9 and C 10 . With the obtained constraints, we also calculate the branching ratio of the B s →μ + μ - decay. The upper bound of our prediction is nearly an order of magnitude smaller than the upper bound given by the CDF Collaboration recently.     

Study of Ds±→μ±νμ at Belle

We present a preliminary measurement of the B(D_s→μν_μ) with the Belle     

Searching for new physics in D0→μ+μ-, e+e-,μ±e干 at BES and/or the super charm-tau factory

In contrast with B⁰-B⁰, B_s-B_s mixing where the standard model (SM) contributions overwhelm that of the new physics beyond standard model (BSM), a measured relatively large D⁰-D⁰ mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D⁰→μ⁺μ^- could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D⁰. Concretely we discuss the contributions of unparticle or an extra gauge boson Z' while imposing the constraints set by fitting the D⁰- D⁰ mixing data. We find that the long-distance SM effects for D⁰→l1 still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D⁰→μ^±e⁺, the new physics contribution would be significant.     

Pure annihilation type decays B0→Ds- K2+ and Bs→Da2 in perturbative QCD approach

We calculate the branching ratios of pure annihilation type decays B⁰→D_s^- K₂^*+ and B_s→Da₂ using the perturbative QCD approach based on k_T factorization. The branching ratios are predicted to be (60.6_{-16.5-10.4-2.1}^{+17.3+4.3+3.2} )× 10^-6 for B⁰→D_s^- K₂^*+, (1.1_-0.4-0.2-0.1^+0.4+0.1+0.1)×10^-6 for B_s→D⁰a₂⁰ and (2.3_-0.8-0.4-0.1^+0.8+0.2+0.1)×10^-6 for B_s→D^-a₂⁺. They are large enough to be measured in the ongoing experiment. Due to the shortage of contributions from penguin operators, there are no direct CP asymmetries for these decays in the Standard Model. We also derive simple relations among these decay channels to reduce theoretical uncertainties for the experiments to test the accuracy of theory and search of new physics signal.     

EC/β+ decay of six medium-heavy nuclei

Previous experimental results of (EC+β⁺) decay for the medium-heavy nuclei reported by our group since 1996, including ¹⁵³Er, ¹⁵⁷Yb, ²⁰⁹Fr, ¹²⁸Ce, ¹³⁰Ce, and ¹²⁸Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion.     

A note on Ξc(3055)+ and Ξc(3123)+

The Babar Collaboration announced two new excited charmed baryons Ξ_c(3055)⁺ and Ξ_c(3123)⁺. We study their strong decays assuming they are D-wave states. Some assignments are excluded by comparing our numerical results with the experimental values of the total widths of Ξ_c(3055)⁺ and Ξ_c(3123)⁺. We also suggest some possible decay modes, which will be helpful to     

Branching ratio and CP asymmetry of Bs→K0(1430)η(') decays in the PQCD approach

In the two-quark model supposition for K0*(1430), which can be viewed as either the first excited state (ScenarioⅠ) or the lowest lying state (Scenario Ⅱ), the branching ratios and the direct CP-violating asymmetries for decays s0 → K0*0(1430)η (’) are studied by employing the perturbative QCD factorization approach. We find the following results: (a) The CP averaged branching ratios ofs0 → K0*0 (1430)η ands0→ K0*0(1430)η’ are small and both in the order of 10-7 . If one views K0* (1430) as the lowest lying state, B(s0→K0*0(1430)η) ≈ 3.9×10-7 and B(s0→K0*0(1430)η’) ≈ 7.8×10-7.(b) While the direct CP-violating asymmetries of these two decays are not small: if we still take the parameters of K0* (1430) in scenario , ACPdir(s0→K0*0(1430)η) ≈ 56.2% and ACPdir(s0→ K0*0(1430)η’) ≈ 42.4%. (c) The annihilation contributions will play an important role in accounting for future data, because both the branching ratios and the direct CP asymmetries of these two decays are sensitive to the annihilation type contributions.     

Study of semileptonic decays Bs→Ds1(2536)lν and Bs→Ds2(2573) lν in the CQM model

Based on the assumption that D_s1(2536) and D_s2(2573) belong to T doublet (1⁺,2⁺), we calculate the semileptonic decays of B_s to D_s1(2536) and D_s2(2573) in terms of the Constituent Quark Meson (CQM) model. For B_s→D_s1(2536)+lν and B_s→D_s2(2573)+lν, the order of magnitude of the obtained branching ratios is 10^－3. Our numerical results of the semileptonic decays of B_s to D_s1(2536) and D_s2(2573) are large, which implies that two semileptonic decays should be seen     

Event generators for η/η' rare decays into π+π-l+l- and e+e-μ+μ-

Study of the rare and forbidden decays of η/η' offers a sensitive probe to test fundamental symmetries of quantum chromodynamics and search for new physics beyond the Standard Model. To study the rare decays of η/η' to π⁺π^-e⁺e^-, π⁺π^-μ⁺μ^- and e⁺e^-μ⁺μ^- at the BESⅢ detector, we developed several event generators based on the vector meson dominant model with finite-width corrections and the pseudoscalar mesons mixing theory. The various distributions from event generators are in good agreement with the theoretical predictions, which indicates that the event generators work very well after implemention in the BESⅢ Monte Carlo simulation package. In the BESⅢ physics analysis, the performance of the event generators will be improved in accordance with the distributions of different variables of η/η' from data and the improvement on the theoretical calculations.     

Determination of J/φ Event Number via J/φ→μ+μ- and J/φ→ e+e- at BESIII

The decays of J/φ→μ⁺μ^- and J/φ→ e⁺e^- are studied by Monte-Carlo simulation, based on the Beijing Spectrometer (BES)Ⅲ offline software system. The methods of determination of the J/φ event number via J/φ→μ⁺μ^- and J/φ→ e⁺e^- are presented, respectively. These methods can be used to determine the J/φevent number for the coming BESⅢ J/φ data sample.     

Off-Shell Effect of Quarks in Bs→γe+e-

We evaluate the rare decays B_s→γe⁺e^- in the standard model, considering the off-shell effect of quarks in B_s meson as well as some contributions neglected in previous works. It is found that the quarks off-shell are large. With the predicted branching ratios at order of 10^-8, it is expected that the radiative dileptonic decays will be detected in the LHC-b experiments.     

Study of Ds±→μ±νμ at Belle

We present a preliminary measurement of the B(D_s→μν_μ) with the Belle
experiment at the KEKB collider. We select D_s→μν_μ decays with a method that provides a high-purity of the selected sample and an absolute measurement of the branching fraction. The results are based on a data sample of 550fb^－1 and are compared to similar measurements by other experiments as well as to the predictions of LQCD. We conclude with short prospects for improvements in the accuracy of the measurement.

     

Prospects for searching the η→e+e- rare decay at the CSR

We study the possibility of searching the η→e+e- rare decay on the Cooling Storage Ring (CSR) at Lanzhou. The main features of the proposed Internal Target Experiment (ITE) and External Target Facility (ETF) are included in the Monte Carlo simulation. Both the beam condition at the CSR and the major physics backgrounds are carefully taken into account. We conclude that the ITE is more suitable for such a study due to better detector acceptance and higher beam density. At the maximum designed luminosity (1034cm-2s-1 ), η→e+e- events can be collected every～400 seconds at the CSR. With a mass resolution of 1 MeV, the expected signal-to-background (S/B) ratio is around 1.     

Production of the new gauge boson BH via e－ collision in the littlest Higgs model

The lightest new gauge boson B_H with mass of hundreds GeV is predicted in the littlest Higgs model. B_H should be accessible in the planned ILC and the observation of such particle can strongly support the littlest Higgs model. The realization of γγ and e^－γ collisions would open a wider window to probe B_H. In this paper, we study the new gauge boson B_H production processes e－γ→e－γ     

Three Body Amplitude Analysis of the Process a2(1320)→π+π+π－

We analyze the decay amplitudes of the process a₂(1320)→π⁺π⁺π^－ using the tensor analysis method and show how to obtain three body amplitudes.     

Measurement of J/ψ decays into ΛΛ π+π-

Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π⁺π^- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π⁺π^-)=(4.30±0.13±0.99)×10^-3, excluding the decays to intermediate states, namely J/ψ→Ξ^-Ξ⁺, J/ψ→Σ(1385)^-Σ(1385)⁺, and J/ψ→Σ(1385)⁺Σ(1385)^-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ^-Ξ⁺)=（0.90±0.03±0.18）×10^-3, Br(J/ψ→Σ(1385)^-Σ(1385)⁺)=(1.23±0.07±0.30)×10^-3,and Br(J/ψ→Σ(1385)⁺Σ(1385)^-)=(1.50±0.08±0.38)×10^-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos²θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ^-Ξ⁺, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)^-Σ(1385)⁺, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)⁺Σ(1385)^-.     

A Study of the Processes of e+e－→e+e－,μ+μ－ at Large Angle and Measured Luminosities

Using the BES data collected at √S=4.03GeV.the QED processes of e⁺e^－→e⁺e^－,μ⁺μ^－ have been studied. Our measurements agree with the QED prediction,and luminosities obtained from these two final states are compatible at a level of 4%.The total integrated luminosity of 23.1pb^－1 was given for all data collected at this energy region from the calculation.