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41.
Based on a systematic investigation of J/ψ(ψ) → VP,where V and P stand for light vector and pseudoscalar mesons,we identify the role played by the electromagnetic(EM) transitions and intermediate meson loop transitions,which are essential ingredients for understanding the J/ψ and ψ couplings to VP.We show that on the one hand,the EM transitions have relatively larger interferences in ψ→ρπ and K*K+c.c.as explicitly shown by vector meson dominance(VMD).On the other hand,the strong decay of ψ receives relatively larger destructive interferences from the intermediate meson loop transitions.By identifying these mechanisms in an overall study of J/ψ(ψ)→VP,we provide a coherent understanding of the so-called "ρπ puzzle". 相似文献
42.
Chao-Hsi Chang 《Pramana》2000,55(1-2):283-288
The properties of the meson B
c are outlined. The leptonic radiative decays for B
c meson are presented. An outlook on the studies of the meson is given. 相似文献
43.
Bing An Li 《The European Physical Journal A - Hadrons and Nuclei》2001,10(2):237-244
An effective theory of large-NC QCD of pseudoscalar, vector, and axial-vector mesons has been used to study six Kl4 decay modes. It has been found that the matrix elements of the axial-vector current dominate the Kl4 decays. PCAC is satisfied. A relationship between three form factors of the axial-vector current has been predicted. Partial-wave
analysis has been done. Non-zero phase shifts are originated in ρ→ππ. The decay rates are calculated in the chiral limit.
In this study there is no adjustable parameter.
Received: 17 October 2000 / Accepted: 20 February 2001 相似文献
44.
The recent observations of the purely leptonic decay Ds+→μ+νμ and τ+ντ at CLEO-c and B factory may allow a possible contribution from a charged Higgs bosom One such measurement of the decay constant fDs differs from the most precise unquenched lattice QCD calculation by a level of 4σ.Meanwhile,the measured ratio,BR(D+s+→μ.+νμ)/BR(D+→μ+νμ),is larger than the standard model prediction at a 2.0σ level.We discuss that the precise measurement of the ratio BR(Ds+→μ+νμ)/BR(D+μ+νμ) at BES-Ⅲ will shed light on the presence of new intermediate particles by comparing the data with the theoretical predictions,especially,the predictions of high precise unquenched lattice QCD calculations. 相似文献
45.
Valery V. Kiselev 《Central European Journal of Physics》2004,2(3):523-534
We calculate the leptonic constant for the pseudoscalar ground state of the B
c
meson in the framework of a QCD-motivated potential model taking into account the two-loop anomalous dimension for the heavy
quark current in nonrelativistic QCD as matched with full QCD. 相似文献
46.
We investigate the spectrum and decay rates of charmonium states within the framework of the non relativistic quark model by employing a Coulomb like potential from the perturbative one gluon exchange and the linear confining potential along with the potential derived from instanton vacuum to account for the hyperfine mass splitting of charmonium states in variational approach. We predict radiative E1, M1, two-photon, lepton and two-gluon decay rates of low lying charmonium states. An overall agreement is obtained with the experimental masses and decay widths.We have estimated the branching ratio of two gluons decaying into light hadrons. 相似文献
47.
Ikaros I. Bigi 《Frontiers of Physics》2015,10(3):101203
We know that our Universe is composed of only ~4.5% “known” matter; therefore, our understanding is incomplete. This can be seen directly in the case of neutrino oscillations (without even considering potential other universes). Charm quarks have had considerable impact on our understanding of known matter, and quantum chromodynamics (QCD) is the only local quantum field theory to describe strong forces. It is possible to learn novel lessons concerning strong dynamics by measuring rates around the thresholds of [Q ˉ Q ] states with Q = b, c. Furthermore, these states provide us with gateways towards new dynamics (ND), where we must transition from “accuracy” to “precision” eras. Finally, we can make connections with τ transitions and, perhaps, with dark matter. Charm dynamics acts as a bridge between the worlds of light- and heavy-flavor hadrons (namely, beauty hadrons), and finding regional asymmetries in many-body final states may prove to be a “game changer”. There are several different approaches to achieving these goals: for example, experiments such as the Super Tau-Charm Factory, Super Beauty Factory, and the Super Z0 Factory act as gatekeepers – and deeper thinking regarding symmetries. 相似文献
48.
By employing the perturbative QCD (pQCD) factorization approach, we calculate some important next- to-leading-order (NLO) contributions to the two-body charmless hadronic decays B^+ →ρ^+η(') and B^0 → ρ^0(ω, φ)η('), induced by the vertex QCD corrections, the quark-loops as well as the chromo-magnetic penguins. From the numerical results and phenomenological analysis we find that (a) for B^± → ρ^±η(') (B^0 → ρ^0(ω, φ)η(')decays, the partial NLO contributions to branching ratios are small (large) in magnitude; and (b) the pQCD predictions for ACP^dir(B^± → ρ^±η(')) are consistent with the data, while the predicted .ACP(B^0 → ρ^0(ω)η(')) are generally large in magnitude and could be tested by the forthcoming LHCb experiments. 相似文献
49.
Considering the experimental constraints on the free parameters of the 331 model with a leptonic sector consistent of five triplets, we investigate the lepton flavor violation (LFV) tau decays τ→μM with M=P and V, where P and V denote a pseudoscalar meson (π,η or η') and a vector meson (ρ0,ω or φ), respectively. We find that the contributions of the 331 model to the LFV decays τ→μM mainly come from the new neutral gauge boson Z'. The 331 model considered in this paper can not make the values of the branching ratio Br(τ→μM) approach the corresponding experimental upper limits. 相似文献
50.
Motivated by the recently updated experimental measurement on \bar{B}_d→μ+μ- and B-→π-μ+μ- decays by CDF and Belle collaborations, we revisit these
decays, as well as B-→ρ-μ+μ- decay, within the Standard Model, and evaluate the effects of a family non-universal Z' boson. Under the constraint from {\cal B}(B-→π-μ+μ-), we find the ranges of the Z' couplings SLRμμ< -5.2×10-2 or DLRμμ < -8.1× 10-2 are excluded. Within the allowed Z' parameters spaces, comparing with the SM predictions, we find that {\cal B}(\bar{B}_d→ μ+μ-, {\cal B}(B-→ π-μ+μ-), and {\cal B}(B-→ρ-μ+μ-) could be enhanced by a factor about
226%, 245%, and 254%, respectively, byZ' contributions. However, they are hardly to be reduced. Furthermore, the zero crossing in the normalized forward-backward asymmetry spectrum of B- →ρ-μ+μ- decay at low dimuon mass always exists. 相似文献