Study of pure annihilation decays B_(d,s)→D~0~0

Within the heavy quark limit and the hierarchy approximation λQCD mD mB, we analyze the B → D00 and Bs → D00 decays, which occur purely via annihilation type diagrams. As a rough estimate, we calculate their branching ratios and CP asymmetries in the perturbative QCD (PQCD) approach. The branching ratio of B → D00 is about 3.8×10-5 that is just below the latest experimental upper limit. The branching ratio of Bs → D00 is about 6.8×10-4, which could be measured in LHC-b. From the calculation, it is found that this branching ratio is not sensitive to the weak phase angle γ. In these two decay modes, there exist CP asymmetries because of the interference between weak and strong interaction. However, these asymmetries are too small to be measured easily.     

B_(s,d)→μ~+μ_- decays in a flavor changing Z′ model

We study the pure leptonic decays Bs,d →μ+μ- in a Flavor Changing Z′ Model.From the recent measurements of the branching ratios B(Bs,d →μ+μ-),we have derived the bounds on the effective μ-μ-Z′ lepton coupling BμLμ.We find that,(i) if neglecting the contribution from the right-handed lepton coupling BμRμ,we obtain 1.32 < BμLμ < 3.32;(ii) if considering the contribution from the right-handed lepton coupling BμRμ and setting BμLμ =BμRμ,we obtain 0.99相似文献   

Observation of D(1285)→φγ radiative decay

The D(1285) radiative decay has been observed, 19±5 events of this type have been detected. The branching ratio Br[D(1285)→φγ] = (0.9±0.2±0.4) × 10⁻³ and the partial width γ [D(1285)→φγ] = 23 ±5±10) keV have been determined. The conclusion has been made that, most probably, the E(1420) meson does not belong to the axial nonet.     

Observation of X(3872)→J/ψγ and search for X(3872)→ψ'γ in B decays

We report a study of B→(J/ψγ)K and B→(ψ'γ)K decay modes using 772×10? B ?B events collected at the Υ(4S) resonance with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. We observe X(3872)→J/ψγ and report the first evidence for χ(c2)→J/ψγ in B→(X_{c ?cγ)K decays, while in a search for X(3872)→ψ'γ no significant signal is found. We measure the branching fractions, B(B(±)→X(3872)K(±))B(X(3872)→J/ψγ)=(1.78(-0.44)(+0.48)±0.12)×10(-6), B(B(±)→χ(c2)K(±))=(1.11(-0.34)(+0.36)±0.09)×10(-5), B(B(±)→X(3872)K(±))B(X(3872)→ψ'γ)<3.45×10? (upper limit at 90% C.L.), and also provide upper limits for other searches.     

Measurement of various decay modes of charmed particlesD 0,D +,D s + andΛ s c

In the CERN NA 32 experiment a high-resolution silicon vertex detector and a purely topological approach have been used to investigate various decays of charmed particles. We observe ～620 fully reconstructed decays ofD ⁰ in 12 channels and determine the branching ratios. For fourD ⁰ decay modes involving a single (unseen) π⁰ the small and narrowD ^*+?D ⁰ mass difference is used to measure their branching ratios. We also observe ～280 fully reconstructedD ⁺ decays in 10 channels, ～90D _s ⁺ decays in 11 channels as well as 160Λ _s ^c and 18 decay channels ofD ⁺. For theD _s ⁺ , we measure the branching fractions within a subset of 16 three- and five-prong decay channels. For theΛ _s ^c , we determine the branching fractions within a sample of 11 three- and five-prong decay channels, nearly all involving a proton.     

Fe(5D/3D)+CH2(1A1)→FeC+H2的理论研究

采用密度泛函理论(DFT)中的UB3LYP方法在6-311 G(2d,2p)水平上研究了五重态和三重态的Fe与单重态CH2反应的机理,在UB3LYP结构优化的基础上用耦合簇理论方法UCCSD(T)在相同水平下对各驻点进行了单点能校正.结果表明,该反应在三重态和五重态上的势能面非常相似,都经过两个过渡态(TS1、TS2)和三个中间体(FeCH2、HFeCH、H2FeC),五重态和三重态势能面在形成中间体FeCH2前发生交叉,整个反应沿三重态路径进行,最后得到三重态的FeC和H2.该反应是一个四步反应,其中由HFeCH到H2FeC的反应步骤为整个反应的速率控制步骤,反应的活化能为176.3 kJ/mol.     

Search for CP violation in the decays D(0)→K(S)(0)P(0)

We have searched for CP violation in the decays D(0)→K(S)(0)P(0) where P(0) denotes a neutral pseudoscalar meson that is either a π(0), η, or η' using KEKB asymmetric-energy e(+)e(-) collision data corresponding to an integrated luminosity of 791 fb(-1) collected with the Belle detector. No evidence of significant CP violation is observed. We report the most precise CP asymmetry measurement in the decay D(0)→K(S)(0)π(0) to date: A(CP)(D(0)→K(S)(0)π(0))=(-0.28±0.19±0.10)%. We also report the first measurements of CP asymmetries in the decays D(0)→K(S)(0)η and D(0)→K(S)(0)η': A(CP)(D(0)→K(S)(0)η)=(+0.54±0.51±0.16)% and A(CP)(D(0)→K(S)(0)η')=(+0.98±0.67±0.14)%, respectively.     

Properties of the coupling constants of J/ψ→VP decays

Based on the branching fractions of J/ψ→VP from different experiments, we investigate the properties of the coupling constants of J/ψ→VP decays using a model-dependent approach. We find that the octet coupling constant, g8, of strong interaction is about twice larger than that of the singlet coupling constant g₁; the electromag- netic breaking parameters g_Eⁱ are larger than the mass breaking parameters g_Mⁱ, moreover, the three parameters of the electromagnetic effect are about equal, but the three parameters of the mass effect are obviously different and their uncertainties are also large; and the phase angle between strong and electromagnetic interactions is in the range of 70°-80°. It deepens our understanding of the coupling constant of J/ψ→VP decays.     

Uncertainty study of D_s~- (D~-)→ γl (l = e,μ) decays determined by wave function

Wave function is important for determining decay constants f_(D_s~-) and f_(D~-). Using the 5 types of D meson wave functions in the heavy quark limit, we studied the uncertainties of radiative pure-leptonic decays of D_s~- (D~-) mesons. The branching ratios are (1.025390-1.706812) ×10~5 and (0.953498-1.576725) ×10~6 for D_s~- and D~- decays, respectively, which are sensitive to the type of wave function.     

Measurement of the D0, D+ and Ds+ meson lifetimes at √s = 10.58 GeV

We have measured the lifetimes of the D⁰, D⁺ and D_s⁺ mesons with data from the CLEO detector. We find τ_D⁰ = (5.0 ± 0.7 ± 0.4) × 10⁻¹³s, τ_D⁺ = (11.4 ± 1.6 ± 0.7) × 10⁻¹³s and τ_Ds⁺ = (4.7 ± 2.2 ± 0.5) × 10⁻¹³s, giving lifetime ratios τ_D⁺/τ_D⁰ = 2.3 ± 0.5 and τ_Ds⁺/τ_D⁰ = 0.9 ± 0.5.     

Observation of D+ → K(+)η(') and search for CP violation in D+ → π(+)η(') decays

We report the first observation of the doubly Cabibbo-suppressed decays D(+)→K(+)η((')) using a 791 fb(-1) data sample collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The ratio of the branching fractions of doubly Cabibbo-suppressed relative to singly Cabibbo-suppressed D(+)→π(+)η((')) decays are B(D(+)→K(+)η)/B(D(+)→π(+)η)=(3.06±0.43±0.14)% and B(D(+)→K(+)η')/B(D(+)→π(+)η')=(3.77±0.39±0.10)%. From these, we find that the relative final-state phase difference between the tree and annihilation amplitudes in D(+) decays, δ(TA), is (72±9)° or (288±9)°. We also report the most precise measurements of CP asymmetries to date: A(CP)(D(+)→π(+)η)=(+1.74±1.13±0.19)% and A(CP)(D(+)→π(+)η')=(-0.12±1.12±0.17)%.     

Long-distance dominance of the CP asymmetry in B→X(s,d)γ decays

We show that in the standard model the parametrically leading (by a factor 1/α(s)) contribution to the inclusive CP asymmetry in B→X(s,d)γ decays arises from a long-distance effect in the interference of the electromagnetic dipole amplitude with the amplitude for an up-quark penguin transition accompanied by soft gluon emission. Using model estimates for the associated hadronic parameter Λ(17)(u), we predict a value in the range -0.6% < A(X(s)γ)(SM) < 2.8%. In view of current experimental data, a future precision measurement of the flavor-averaged CP asymmetry would signal the presence of new physics only if a value below -2% was found. A cleaner probe of new physics is offered by the difference of the CP asymmetries in charged versus neutral B→X(s,d)γ decays.     

Observation of B(s)(0) → D(s)(*)+ D(s)(*)- using e+ e- collisions and a determination of the B(s)-B(s) width difference ΔΓ(s)

We have made the first observation of B(s)(0)→D(s)(*)+ D(s)(*)- decays using 23.6 fb(-1) of data recorded by the Belle experiment running on the Υ(5S) resonance. The branching fractions are measured to be B(B(s)(0)→D(s)+ D(s)-)=(1.03(-0.32-0.25)(+0.39+0.26))%, B(B(s)(0)→D(s)(*±) D(s)(?))=(2.75(-0.71)(+0.83)±0.69)%, and B(B(s)(0)→D(s)*+ D(s)*-)=(3.08(-1.04-0.86)(+1.22+0.85))%; the sum is B[B(s)(0)→D(s)(*)+ D(s)(*)-]=(6.85(-1.30-1.80)(+1.53+1.79))%. Assuming B(s)(0)→D(s)(*)+ D(s)(*)- saturates decays to CP-even final states, the branching fraction determines the ratio ΔΓ(s)/cosφ, where ΔΓ(s) is the difference in widths between the two B(s)-B(s) mass eigenstates, and φ is a CP-violating weak phase. Taking CP violation to be negligibly small, we obtain ΔΓ(s)/Γ(s)=0.147(-0.030)(+0.036)(stat)(-0.041)(+0.042)(syst), where Γ(s) is the mean decay width.     

A test of the Lorentz structure of semi-hadronic τ decays

A method is proposed for the determination of the Lorentz structure of the electroweak interaction in semi-hadronic τ decays. Spin correlations in the process $$e^ + e^ - \to \tau ^ + \tau ^ - \to \bar v_\tau \pi ^ + \pi ^0 v_\tau \pi ^ - \pi ^0 $$ are exploited for a measurement of the normalized product, γ_AV = 2Re{g_Ag _V ^* }/(|g_V|² + |g_V|²), of the vector (g _V ) and axial vector (g _A ) coupling of the τ lepton. The contribution of scalar (g _S ) or pseudo-scalar (g _P ) couplings is also investigated. Since in the above process the direction of flight of the τ leptons can be reconstructed up to a twofold ambiguity a likelihood method using the whole kinematic information can be employed. The matrix element entering the likelihood function has been evaluated in terms of the momenta and angles of the observed pions. The sensitivity of the derived method in ane ⁺ e ^? energy region around 10 GeV has been investigated for the ARGUS experiment using Monte Carlo simulations.     

Studying the Fourth Generation Quark Contributions to the Double Charm Decays B(s)→D(s)(∗)Ds(∗)

Almost all branching ratios and longitudinal polarization fractions of the double charm decays \(B_{(s)} \to D_{(s)}^{(*)} D_{s}^{(*)}\) have been measured, and the experimental central value of \(f_{L}({B^{0}_{s}}\to D^{*+}_{s}D^{*-}_{s})\) is quite small comparing to its Standard Model prediction. We study the fourth generation quark contributions to the double charm decays \(B_{(s)} \to D_{(s)}^{(*)} D_{s}^{(*)}\). We find that the loop diagrams involving the fourth generation quark t′ have great effects on all branching ratios and CP asymmetries, which are very sensitive to the fourth generation parameter \(\lambda ^{s}_{t^{\prime }}\) and \(\phi _{t^{\prime }}\). Nevertheless, the experimental measurements of all branching ratios can not give effective constraints on relevant new physics parameters. In addition, they have no obvious effect on the relevant polarization fractions. These results could be used to search for the fourth heavy quark t′ via its indirect manifestations in loop diagrams.     

Rare decays B_(s,d)~O→e~+e~- in a top quark two-Higgs-doublet model

In the framework of T2HDM, we calculated the new physics contributions involving neutral Higgs bosons to the branching ratios of B_(s,d)~0→e~+e~-(e=e,μ) decays. Comparing the theoretical predictions with the experimental upper-limits, we found that (a) The data of Br(B_d~0→e~+e~-)give the upper bound on tanβ: tanβ≤ 22, while Br(B_s~0→e~+e~-)give tanβ≤12 for fixed δ = 0°, m_H+=350 GeV, m_Ho = 160 GeV, m_Ho= 115 GeV and m_Ao=120 GeV; (b) A light neutral Higgs boson mass m_Ho (m_Ao) less than 50 GeV (120 GeV) is excluded by the data of branching ratios for B_(s,d)~0→e~+e~-(e=μ) decays with tanβ=10; (c) The bounds on m_(h~0) and tanβ, or m_(A~0) and tanβ are strongly correlated: a smaller (larger) tanβ means a lighter (heavier) neutral Higgs boson.     

Investigation of rare semileptonic B_c→(D_(s,d)~((*))μ~+μ~- decays with non-universal Z' effect

We analyze different decay observables of semileptonic decays B_c→(D_(s,d)~((*)))μ~+μ~-,such as the branching ratio,forward-backward asymmetry,polarization fraction,and lepton polarization asymmetry in the non-universal Z'model.We further study the dependence of the branching fraction to the new model parameters and find that the values of different decay parameters increase in the Z' model,which indicates a possible approach for the search of new physics as well as for the unknown phenomena of the charm B meson.