Comprehensive analysis of e+e-→γηc(2S)

We discuss the production of η_c(2S) through the process e⁺e^-→γη_c(2S), where the leading contribution originates from 1-loop electroweak corrections. Adopting some reasonable light-cone distribution amplitudes, we analyze the cross section of this process. As the electron-positron center of mass energy √s=3770 MeV, the typical production cross section of this process is about 1 fb.     

Semileptonic decays Bc→(ηc,J/Ψ)lv in the perturbative QCD approach

In this paper we study the semileptonic decays of B_c^-→(η_c,J/Ψ)l^-v_l. We first evaluate the B_c→(η_c,J/Ψ) transition form factors F₀(q²), F₊(q²), V(q²) and A_0,1,2(q²) by employing the pQCD factorization approach, and then we calculate the branching ratios for all considered semileptonic decays. Based on the numerical results and the phenomenological analysis, we find that: (a) the pQCD predictions for the values of the B_c→η_c and B_c→J/Ψ transition form factors agree well with those obtained by using other methods; (b) the pQCD predictions for the branching ratios of the considered decays are Br(B_c^-→η_c e^-v_e(μ^-v_μ)=(4.41_-1.09^+1.22)×10^-3, Br(B_c^-→η_cτ^-v_τ) =(1.37_-0.34^+0.37)×10^-3, Br(B_c^-→J/Ψ e^-v_e(μ^-v_μ)) =(10.03_-1.18^+1.33)×10^-3, and Br(B_c^-→J/Ψτ^-v_τ) =(2.92_-0.34^+0.40)×10^-3; and (c) we also define and calculate two ratios of the branching ratios R_ηc and R_J/Ψ, which will be tested by LHCb and the forthcoming Super-B experiments.     

T2K indication of relatively large θ13 and a natural perturbation to the democratic neutrino mixing pattern

The T2K Collaboration has recently reported a remarkable indication of the ν→ν oscillation which is consistent with a relatively large value of θ₁₃ in the three-flavor neutrino mixing scheme. We show that it is possible to account for such a result of θ₁₃ by introducing a natural perturbation to the democratic neutrino mixing pattern, without or with CP violation. A testable correlation between θ₁₃ and θ₂₃ is predicted in this ansatz. We also discuss the Wolfenstein-like parametrization of neutrino mixing, and comment on other possibilities of generating sufficiently large θ₁₃ at the electroweak scale.     

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     

O(α_sv~2) correction to J/ψ plus η_c production in e~+e~- annihilation at √s=10.6 GeV

Based on the nonrelativistic QCD factorization approach, O(α_sv2) corrections to J/ψ plus η_c production in m e⁺e^- annihilation at √s=10.6 ≥v are calculated in this work. The numerical results show that the correction at α_sv2 order is only about a few percent of the total theoretical result. This indicates that the perturbative expansions become convergent and that a higher order correction will be smaller. The uncertainties from the long-distance matrix elements, renormalization scale and the measurement in the experiment are also discussed. Our result is in agreement with the previous result by Jia.     

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     

Signals of the littlest Higgs model with T-parity at eγ and ep collisions

The littlest Higgs model with T-parity predicts the existence of the neutral, weakly interacting, new gauge boson B_H, which can be seen as an attractive dark matter candidate. We study production of the new gauge boson B_H via eγ and ep collisions. We find that B_H can be abundantly produced via the subprocesses e^－γ→L^－B_H and γq→B_HQ, which might give rise to characteristic signals. Some discussions about the SM backgrounds for this kind of signals are also given.     

Measuring D0-D0 mixing in D→f0(980) K and more

We investigate the D⁰-D⁰ mixing through the doubly Cabibbo suppressed (DCS) channel D0→f₀(980)K^*0 and its charge conjugate channel, in which the K^*0 meson is reconstructed in both K⁺π^－ and K_Sπ⁰ final state. Although the decay D⁰→f₀(980)K^* has a small branching ratio, the final state mesons are relatively easy to identify. The f₀(980) meson can be replaced by the S-wave π⁺π^－ state, or a longitudinally polarized vector meson ρ⁰. All mixing parameters, including the mass difference and decay width difference, can be extracted by studying the time-dependent decay width of these channels. We show that the method is valid in all regions for mixing parameters and it does not depend on the strong phase difference.     

Systematic analysis of DJ(2580), DJ(2650), DJ(2740), DJ(2760), DJ(3000) and DJ(3000) in the D meson family

In this work, we tentatively assign the charmed mesons D_J(2580), D_J^*(2650), D_J(2740), D_J^*(2760), D_J(3000) and D_J^*(3000) observed by the LHCb collaboration according to their spin, parity and masses, then systematically study their strong decays to ground state charmed mesons plus pseudoscalar mesons with the ³P₀ decay model. Based on these studies, we assign the D_J^*(2760) as the 1D(5/2)3^- state, the D_J^*(3000) as the 1F(5/2)2⁺ or 1F(7/2)4⁺ state, the D_J(3000) as the 1F(7/2)3⁺ or 2P(1/2)1⁺ state in the D meson family. As a byproduct, we also study the strong decays of the states 2P(1/2)0⁺, 2P(3/2)2⁺, 3S(1/2)1^-, 3S(1/2)0^- etc, which will be valuable in searching for the partners of these D mesons.     

Mini-review of rare charmonium decays at BESⅢ

Recently, the LHCb experiment announced 3.5σ evidence for direct CP violation in D⁰ decay by looking at the difference between A_CP(D⁰→K⁺K^-) and A_CP(D⁰→π⁺π^-). This is the rst evidence of CP violation in a charm system, which may indicate new physics beyond the Standard Model. Motivated by this measurement, we review rare processes in charmonium decay, especially, the weak decay, C or P violated decay, and lepton avor violated decays. In case the new physics appears in charm sector, these rare decays of charmonium states will provide an opportunity to search for signi cant contributions from physics beyond the Standard Model. With huge J/ψ and ψ(2S) samples in BES0 experiment, the rare decays may be feasible.     

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.     

Astrophysical S-factor of the d(p,γ)3He processby

We summarize the recent effective field theory (EFT) studies of low-energy electroweak reactions of astrophysical interest, relevant to big-bang nucleosynthesis. The zero energy astrophysical S(0) factor for the thermal proton radiative capture by deuteron is calculated with pionless EFT. The astrophysical S(0) factor is accurately determined to be S(0)=0.243 eV·b up to the leading order (LO). At zero energies, magnetic transition M₁ gives the dominant contribution. The M₁ amplitude is calculated up to the LO. A good, quantitative agreement between theoretical and experimental results is found for all observables. The demonstrations of cutoff independent calculation have also been presented.     

Study of Λ decay parameter in J/ψ→ΛΛ decay

The helicity amplitudes for J/ψ→ΛΛ and the relevant background decays are presented for measuring the Λ decay parameter α₊(Λ→pπ⁺) in J/ψ→ΛΛ . The Monte Carlo (MC) simulations based on the helicity amplitudes information are carried out. The likelihood fit method to determine the Λ decay parameter is presented. Based on the MC generated sample, the sensitivity of the measurement for α₊ has been estimated, which shows that the J/ψ→ΛΛ channel can be used to measure the Λ decay parameter α₊(Λ→pπ⁺) well.     

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.     

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     

Evidence for e+e-→γχc1,2 at center-of-mass energies from 4.009 to 4.360 GeV

Using data samples collected at center-of-mass energies of √s=4.009, 4.230, 4.260, and 4.360 GeV with the BES0 detector operating at the BEPC/ collider, we perform a search for the process e⁺e^-→γχ_c,j (J =0, 1, 2) and find evidence for e⁺e^-→γχ_c1 and e⁺e^-→γχ_c2 with statistical significances of 3.0σ and 3.4σ, respectively. The Born cross sections σ^B(e⁺e^-→γχ_c,j), as well as their upper limits at the 90% con dence level (C.L.) are determined at each center-of-mass energy.     

Study of pure and semileptonic decays of D_s meson within R-parity violating supersymmetric model

We present the comaprative study of semileptonic and leptonic decays of D_s,D^± and D⁰ meson ( D→ M l_α ⁺l_β^-,D→l_α⁺l_β^-,D→l_α⁺v_α ;α,β=e,μ) within the framework of R-parity violating the (R_p) Minimal Supersymmetric Standard Model (MSSM). The comparison shows that combination and product couplings, (λ_βiαλ''_ijq^* or λ''_βqk^*λ''_{α jk}^*) contribution to the branching fractions of the said processes (under consideration) is consistent with or comparable to the experimental measurements in most of the cases. However, some cases exist where these contributions are highly suppressed. We identify such cases in our analysis and single out the important ones suitable for exploring in the future and current experiments.     

PAC investigation of qudropole interaction in nano-soft magnetic material Fe73.5Cu1Nb3Si13.5B9

The quadrupole interaction in nano-soft magnetic material Fe_73.5Cu₁Nb₃Si_13.5B₉ has been studied by perturbed angular correlation using ⁶²Zn probe nuclei from the ISOL radioactive nuclear beam facility at CIAE HI-13 tandem accelerator. Two quadrupole interaction frequencies ω₀₁=440 Mrad/s with a distribution width σ=0 and ω₀₂=90 Mrad/s with a width σ=0.48 are obtained. The fractions of ω₀₁ and ω₀₂ are 38% and 62%, respectively. The measured quadruple interaction parameters indicate that 62% of the implanted ⁶²Zn are located in the grain boundary and 32% in the grain.     

Strange magnetic moments of octet baryons under SU (3) breaking

Magnetic moments of octet baryons are parameterized to all orders of the flavor SU(3) breaking with the irreducible tensor technique in order to extract the contribution of each flavor quark to the magnetic moments of the octet baryons. The not-yet measured magnetic moment of ∑⁰ is predicted to be 0.649μ_N. Our parameterized forms for the magnetic moments are explicitly flavor-dependent, and hence each flavor component of the magnetic moments can be evaluated directly via the flavor projection operator. It is found that the strange magnetic moment of the nucleon is suppressed due to the small isoscalar anomalous magnetic moment of the nucleon. In particular, the strange magnetic form factor of the nucleon turns out to be positive, G_N^s(0)=0.428μ_N, which is consistent with recent data.