Direct CP violation in B(s)→J/ψP(V)

In the framework of factorization, we study direct CP violation in the decays of B_(s)→J/ψP(V) (P(V) refer to the pseudoscalar (vector) meson). The CP violation depends strongly on Cabibbo-Kobayashi- Maskawa (CKM) matrix elements and the effective parameter, N_c. The recent experimental data for the branching ratios of B_(s)→J/ψP(V) are accurate enough and we can give a strong constraint on the range of N_c. We nd that the CP violating asymmetry is consistent with the available experiment values for the b→d transition, and a little smaller than the b→s transition. We also predict the CP violation of other decay channels for B_(s)→J/ψP(V). We expect our results can give valuable guidance for experiments.     

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.     

Geometry of the effective Majorana neutrino mass in the 0νββ decay

The neutrinoless double-beta (0νββ) decay is a unique process used to identify the Majorana nature of massive neutrinos, and its rate depends on the size of the effective Majorana neutrino mass <m>_ee. We put forward a novel ‘coupling-rod’ diagram to describe <m>_ee in the complex plane, by which the effects of the neutrino mass ordering and CP-violating phases on <m>_ee are intuitively understood. We show that this geometric language allows us to easily obtain the maximum and minimum of |<m>_ee|. It remains usable even if there is a kind of new physics contributing to <m>_ee, and it can also be extended to describe the effective Majorana masses <m>_eμ, <m>_eτ, <m>_μμ, <m>_μτ and <m>_ττ which may appear in some other lepton-number violating processes.     

Measurement of the liquid scintillator nonlinear energy response to electron

Nonlinearity of the liquid scintillator energy response is a key to measuring the neutrino energy spectrum in reactor neutrino experiments such as Daya Bay and JUNO. We measured the nonlinearity of the linear alkyl benzene based liquid scintillator in the laboratory, which is used in Daya Bay and will be used in JUNO, via the Compton scattering process. By tagging the scattered gamma from the liquid scintillator sample simultaneously at seven angles, the instability of the system was largely cancelled. The accurately measured nonlinearity will improve the precision of the θ₁₃, Δm², and reactor neutrino spectrum measurements at Daya Bay.     

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.     

Model with strong γ4 T-violation

We extend the T violating model of the paper on ``Hidden symmetry of the CKM and neutrino-mapping matrices" by assuming its T-violating phases χ_↑ and χ_↓ to be large and the same, with χ=χ_↑=χ_↓. In this case, the model has 9     

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.     

Discrimination of converted photons and neutral pions at high energies

In the LHC experiment, the H→γγ channel provides a clean nal state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H→γγ channel is one of the most promising channels for the Higgs discovery in the very low mass region. In order to increase the sensitivity of the Higgs search, background rejection rate is very important, so γ/π⁰ discrimination is one of the key points in the analysis. At least 40% of photons will convert with the experience of ATLAS and CMS. We constructed electromagnetic calorimeter (ECAL) in GEANT4 simulation, using 6 variables which have different shapes between converted γ and π⁰, with the TMVA (Toolkit for Multivariate Data Analysis) to do the separation. With this method we can get 30% to 60% π⁰ rejection efficiency when keeping 90% converted γ efficiency, in the region of transverse momentum 15 GeV to 75 GeV, not only in MC sumulation but also in real data.     

Using a LaBr3:Ce scintillator for positron annihilation lifetime spectroscopy

A LaBr₃:Ce scintillator has a high light output (~60000 p.e/MeV) and a short decay constant (<25 ns), which makes it good for time spectrometry. Compared with a BaF₂ scintillator, it can bear a much higher count rate, and can be coupled to photomultipliers without using a quartz window. In this work, a positron annihilation lifetime spectrometer (PALS) consisting of two bulks of φ25 mm×25 mm LaBr₃:Ce scintillator coupled to two XP20D0 photomultipliers, respectively, was built. A time resolution of FWHM=206 ps was measured for the PALS with a ⁶⁰Co source at the energy window for ²²Na. With this spectrometer, a reasonable lifetime value τ=221±4 ps in a pure Si sample is obtained, which means that the utilization of LaBr₃:Ce as the detector for a PALS is feasible.     

Cs2 Te photocathode fabrication system at Peking University

A cesium telluride (Cs₂Te) photocathode with a quantum efficiency of 13% at 253.7 nm (radiant incidence 200 μ/cm²) is fabricated by tellurium and cesium vapor deposition onto a stainless-steel substrate. The cesium telluride cathode will be used to provide a high-brightness electron beam source for the 3+1/2 photo-injector at Peking University. The design of the system, the fabrication procedures and the preliminary experimental results are presented in this paper.     

Structure of A=11 double-Λ hypernuclei studied withthree-body forces

The energy levels and ΛΛ bond energy of the double-Λ hypernucleus ¹¹Be are calculated considering two- and three-nucleon forces. The interactions between the constituent particles are contact interactions that reproduce the low-energy binding energy of the nuclei. Effective action is constructed to involve the three-body forces. In this paper, we compare the binding energy result that is obtained with the experimental and other modern nucleon-nucleon potentials. The results of all the schemes agree very well, showing the high accuracy of our present ability to calculate the many-nucleon bound state with three-body forces. The experimental value of B_{Λ Λ}(_ΛΛ¹¹Be)=20.83 MeV seems to be more compatible with our calculated value of B_ΛΛ(_ΛΛ¹¹Be)=19.31 MeV in comparison with the calculated result of 18.23 MeV by Hiyama et al.     

Earthquake forecast via neutrino tomography

We discuss the possibility of forecasting earthquakes by means of (anti)neutrino tomography. Antineutrinos emitted from reactors are used as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomography of the vicinity of the region. In this preliminary work, we adopt a simplified model for the geometrical profile and matter density in a fault zone. We calculate the survival probability of electron antineutrinos for cases without and with an anomalous accumulation of electrons which can be considered as a clear signal of the coming earthquake, at the geological region with a fault zone, and find that the variation may reach as much as 3% for ν_e emitted from a reactor. The case for a ν_e beam from a neutrino factory is also investigated, and it is noted that, because of the typically high energy associated with such neutrinos, the oscillation length is too large and the resultant variation is not practically observable. Our conclusion is that with the present reactor facilities and detection techniques, it is still a difficult task to make an earthquake forecast using such a scheme, though it seems to be possible from a theoretical point of view while ignoring some uncertainties. However, with the development of the geology, especially the knowledge about the fault zone, and with the improvement of the detection techniques, etc., there is hope that a medium-term earthquake forecast would be feasible.     

Neutrino mixing matrix and masses from a particular two-zero texture based on A4 symmetry

The current study aims to investigate the particular case of two zeros in a Majorana neutrino mass matrix based on A₄ symmetry,where charged lepton mass matrix is diagonal.The texture is ■ with(μ,μ) and(τ,τ) vanishing element of the neutrino mass matrix.The texture ■ has magic and μ-τ symmetry,with a tribimaximal form of the mixing matrix,which leads to θ₁₃=0 that it is not consistent with experimental data and at first,does not seem to be allowed.Since θ₁₃ a sma...     

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.     

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.     

Developments in accelerator mass spectrometry (AMS) method for 182Hf

The present detection limit for ¹⁸²Hf at CIAE HI-13 AMS systems could not satisfy various applications (e. g. detection of a nearby supernovae signal). Therefore, techniques were developed in this work to improve the AMS measurement of ¹⁸²Hf mainly on building a new injector and using a method that based on solid-phase reaction for the preparation of HfF₄ samples from HfO₂. The experimental results show that mass resolution of the injector can reached 630, and the F^－/O－ and beam current of ¹⁸⁰HfF₅^－ for HfF₄ samples produced by dry method is about 2—3 times and 1.5 times of that by previously method, respectively.     

Implications of fermionic dark matter on recent neutrino oscillation data

We investigate flavor phenomenology and dark matter in the context of the scotogenic model.In this model,the neutrino masses are generated through radiative corrections at the one-loop level.Considering the neutrino mixing matrix to be of tri-bimaximal form with additional perturbations to accommodate the recently observed nonzero value of the reactor mixing angle θ_(13),we obtain the relation between various neutrino oscillation parameters and the model parameters.Working in a degenerate heavy neutrino mass spectrum,we obtain light neutrino masses obeying the normal hierarchy and also study the relic abundance of fermionic dark matter candidates,including coannihilation effects.A viable parameter space is thus obtained,consistent with neutrino oscillation data,relic abundance and various lepton flavor violating decays such as 1_α→1_(βγ) and 1_α→31_β.