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Study of Dynamics of $D^0 to K^- e^+ u_{e}$ and $D^0topi^- e^+ u_{e}$ Decays

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 Added by Gang Rong
 Publication date 2015
  fields
and research's language is English




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In an analysis of a 2.92~fb$^{-1}$ data sample taken at 3.773~GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be $mathcal B(D^0 to K^-e^+ u_e)=(3.505pm 0.014 pm 0.033)%$ and $mathcal B(D^0 to pi^-e^+ u_e)=(0.295pm 0.004pm 0.003)%$. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element $f_{+}^K(0)|V_{cs}|=0.7172pm0.0025pm 0.0035$ and $f_{+}^{pi}(0)|V_{cd}|=0.1435pm0.0018pm 0.0009$. Combining these products with the values of $|V_{cs(d)}|$ from the SM constraint fit, we extract the hadronic form factors $f^K_+(0) = 0.7368pm0.0026pm 0.0036$ and $f^pi_+(0) = 0.6372pm0.0080pm 0.0044$, and their ratio $f_+^{pi}(0)/f_+^{K}(0)=0.8649pm 0.0112pm 0.0073$. These form factors and their ratio are used to test unquenched Lattice QCD calculations of the form factors and a light cone sum rule (LCSR) calculation of their ratio. The measured value of $f_+^{K(pi)}(0) |V_{cs(d)}|$ and the lattice QCD value for $f^{K(pi)}_+(0)$ are used to extract values of the CKM matrix elements of $|V_{cs}|=0.9601 pm 0.0033 pm 0.0047 pm 0.0239$ and $|V_{cd}|=0.2155 pm 0.0027 pm 0.0014 pm 0.0094$, where the third errors are due to the uncertainties in lattice QCD calculations of the form factors. Using the LCSR value for $f_+^pi(0)/f_+^K(0)$, we determine the ratio $|V_{cd}|/|V_{cs}|=0.238pm 0.004pm 0.002pm 0.011$, where the third error is from the uncertainty in the LCSR normalization. In addition, we measure form factor parameters for three different theoretical models that describe the weak hadronic charged currents for these two semileptonic decays. All of these measurements are the most precise to date.



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The charm semileptonic decays $D^+toeta e^+ u_{e}$ and $D^+toetae^+ u_{e}$ are studied with a sample of $e^+e^-$ collision data corresponding to an integrated luminosity of 2.93 fb$^{-1}$ collected at $sqrt{s}$ = 3.773 GeV with the BESIII detector. We measure the branching fractions for $D^+toeta e^+ u_{e}$ to be $(10.74pm0.81pm0.51)times10^{-4}$, and for $D^+toetae^+ u_{e}$ to be $(1.91pm0.51pm0.13)times10^{-4}$, where the uncertainties are statistical and systematic, respectively. In addition, we perform a measurement of the form factor in the decay $D^+toeta e^+ u_{e}$. All the results are consistent with those obtained by the CLEO-c experiment.
By analyzing 2.93 fb$^{-1}$ data collected at the center-of-mass energy $sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay $D^+rightarrowbar K^0 e^{+} u_{e}$ to be ${mathcal B}(D^{+}rightarrowbar K^0 e^{+} u_{e})=(8.59 pm 0.14 pm 0.21)%$ using $bar K^0to K^0_Sto pi^0pi^0$, where the first uncertainty is statistical and the second systematic. Our result is consistent with previous measurements within uncertainties.
Using 1.8 million DDbar pairs and a neutrino reconstruction technique, we have studied the decays D^0 -> K^- e^+ nu_e, D^0 -> pi^- e^+ nu_e, D^+ -> Kbar^0 e^+ nu_e, and D^+ -> pi^0 e^+ nu_e. We find B(D^0 -> pi^- e^+ nu_e) = 0.299(11)(9)%, B(D^+ -> pi^0 e^+ nu_e) = 0.373(22)(13)%, B(D^0 -> K^- e^+ nu_e) = 3.56(3)(9)%, and B(D^+ -> Kbar^0 e^+ nu_e) = 8.53(13)(23)%. In addition, form factors are studied through fits to the partial branching fractions obtained in five q^2 ranges. By combining our results with recent unquenched lattice calculations, we obtain |Vcd| = 0.217(9)(4)(23) and |Vcs| = 1.015(10)(11)(106).
Using 2.92 fb$^{-1}$ of electron-positron annihilation data collected at a center-of-mass energy of $sqrt{s}= 3.773$ GeV with the BESIII detector, we present an improved measurement of the branching fraction $mathcal{B}(D^+ to omega e^+ u_{e}) = (1.63pm0.11pm0.08)times 10^{-3}$. The parameters defining the corresponding hadronic form factor ratios at zero momentum transfer are determined for the first time, we measure them to be $r_V = 1.24pm0.09pm0.06$ and $r_2 = 1.06pm0.15 pm 0.05$. The first and second uncertainties are statistical and systematic, respectively. We also search for the decay $D^+ to phi e^+ u_{e}$. An improved upper limit $mathcal{B}(D^+ to phi e^+ u_{e}) < 1.3 times 10^{-5}$ is set at 90% confidence level.
Using a sample of $2.25times 10^8$ $J/psi$ events collected with the BESIII detector at the BEPCII collider, we search for the $J/psi$ semi-leptonic weak decay $J/psi to D^{-}_{s} e^{+} u_{e}+c.c.$ with a much higher sensitivity than previous searches. We also perform the first search for $J/psi to D^{*-}_{s} e^{+} u_{e}+c.c.$ No significant excess of a signal above background is observed in either channel. At the $90%$ confidence level, the upper limits are determined to be $mathcal{B}(J/psi to D^{-}_{s}e^{+} u_{e}+c.c.)<1.3times10^{-6}$ and $mathcal{B}(J/psi to {D^{*}_{s}}^{-}e^{+} u_{e}+c.c.)<1.8times10^{-6}$, respectively. Both are consistent with Standard Model predictions.
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