| Beijing Spectrometer (BES III) operates at the Beijing electron-positron collider (BEPC Ⅱ). BES III has collected data samples at several different energy points, such as J/Ψ, Ψ’, Ψ(3770),Ψ(4040), Y(4260), and Y(4360). And lots of continuum data at3.650GeV were also collected. All these data samples can be used to study the physical topics at γ—charm energy region.Until now BES III detector at BEPC II has collected2.9fb-1data at S1/23.773GeV. With these data, we made some studies of D'VV and D'V-γ. The data used by default in this thesis are collected by BESIII.When a D meson decays to2vector mesons, the helicity angle of the2vector are with great interest. To measure the branching ratio and the longitudinal polar-ization fraction fL of decay of D+'κ*(892)0ρ+(+c.c.), a multi-variable fitting toolkit named DVV Tools was developed. Variables△.E, mBC, mK*and mp are used to distinguish backgrounds from signal, and the helicity angle of K*(892)0and p+(θ1and θ2) are used to distinguish the longitudinal polarized components from the transverse polarized components. So, totally6variables are used in DVV Tools. The parameterized PDF (probability density function) of each variable is determined by MC data samples. In order to describe the data distribution precisely, besides the back-ground, the signal are divided into true-signal and self-cross-feed(SCF) components. It’s assumed that the6variables are uncorrelated, so the joint PDF for each component can be obtained by the product of single-variable PDFs. We mixed60%longitudinal and40%transverse polarized MC signal data to test the D2vvTools toolkit, and get fL=(60.3±0.6)%. Currently we only made some simple check to the background. More studies of the background will undertake in the future.We also search for D+'K*+γ and D+'ρ+γ decays in this thesis. The theoretical prediction of the decay rates of D+'K*+γ and D+'ρ+γ decays are estimated to be10-6. In this thesis, we use△E, mass and cos θH to distinguish backgrounds from signal,and use Double D-Tag method to suppress the non-peaking backgrounds.We give detailed studies of the backgrounds and the systematic uncer-tainties,and use Toy MC study to validate the fitter and fit resuIts of our analysis.All the studies are based on MC simulations,the experimental sensitivities reach a few of10-2.Based on2.9fb-1data atΨ(3770),we obtain the branching fractions at90%confidence level for D+'K+γ and D+'+ρ+γ: B(D+'+K*+γ)<1.8×10-5@90%C.L.(0.7) B(D+'+ρ+γ)<2.2×10-5@90%C.L.(0.8)This is the first search of the rare decays D+'K*+γ and D+'ρ+γ.We still try to estimate the main peaking backgrounds of D+'K*+γ and D+'ρ+γ decays at the mean while,and give our estimation of these decays. B(D+'K*+π0)<1.65×10-4@90%C.L.(0.9) B(D+'K*+π0π0)=(6.77±1.57)×10-4(0.10) B(D+'ρ+π0)=(3.94±0.17)×10-3(0.11) B(D+'π+π0π0)<3.25×10-4@90%C.L.(0.12)... |
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