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Register a new userNew physics in singly Cabibbo-suppressed D decays
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Mchael Gronau
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A U-spin relation among four ratios of amplitudes for $D^0 to pi^+K^-$, $K^+pi^-$, $K^+K^-, pi^+pi^-$, including first, second and third order U-spin breaking, has been derived recently with a precision of $10^{-3}$. We study effects of new $|Delta C|=1$ operators on this relation. We find that it is not affected by U-spin scalar operators, including QCD penguin and chromomagnetic dipole operators occurring in supersymmetric and extra-dimensional models. The relation is modified by new $U=1$ operators with a sensitivity of a few percent characteristic of second order U-spin breaking. Combining this relation with CP asymmetries in $D^0to K^+K^-, pi^+pi^-$ leads to a more solid constraint on $U=1$ operators than from asymmetries alone.
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Using 2.93 fb$^{-1}$ of $e^{+}e^{-}$ collision data taken at a center-of-mass energy of 3.773 GeV by the BESIII detector at the BEPCII, we measure the branching fractions of the singly Cabibbo-suppressed decays $D to omega pi pi$ to be $mathcal{B}(D^0 to omega pi^+pi^-) = (1.33 pm 0.16 pm 0.12)times 10^{-3}$ and $mathcal{B}(D^+ to omega pi^+pi^0) =(3.87 pm 0.83 pm 0.25)times 10^{-3}$, where the first uncertainties are statistical and the second ones systematic. The statistical significances are $12.9sigma$ and $7.7 sigma$, respectively. The precision of $mathcal{B}(D^0 to omega pi^+pi^-)$ is improved by a factor of 2.1 over the CLEO measurement, and $mathcal{B}(D^+ to omega pi^+pi^0)$ is measured for the first time. No significant signal of $mathcal{B}(D^0 to omega pi^0pi^0)$ is observed, and the upper limit on the branching fraction is $mathcal{B}(D^0 to omega pi^0pi^0) < 1.10 times 10^{-3}$ at the $90%$ confidence level. The branching fractions of $Dto eta pi pi$ are also measured and consistent with existing results.
We report on a search for direct CP asymmetry in the singly Cabibbo-suppressed decay D+- --> K+ K- pi+- using a data sample of 476 fb-1 accumulated with the BaBar detector running at and just below the Y(4S) resonance. The CP-violating decay rate asymmetry A_CP is determined to be (0.35 +- 0.30 +- 0.15)%. Model-dependent and model-independent Dalitz plot analysis techniques are used to search for CP-violating asymmetries in the various intermediate states.
Doubly Cabibbo-suppressed (DCS) nonleptonic weak decays of antitriplet charmed baryons are studied systematically in this work. The factorizable and nonfactorizable contributions can be classified explicitly in the topological-diagram approach and treated separately. In particular, the evaluation of nonfactorizable terms is based on the pole model in conjunction with current algebra. All three types of relevant non-perturbative parameters contributing factorizable and nonfactorizable terms are estimated in the MIT bag model. Branching fractions of all the DCS decays are predicted to be of order $10^{-4}sim 10^{-6}$. In particular, we find that the three modes $Xi_c^+to Sigma^+ K^0, Sigma^0 K^+$ and $Xi_c^0to Sigma^- K^+$ are as large as $(1sim 2)times 10^{-4}$, which are the most promising DCS channels to be measured. We also point out that the two DCS modes $Xi_c^+to Sigma^+ K^0$ and $Xi_c^0to Sigma^0 K^0$ are possible to be distinguished from $Xi_c^+to Sigma^+ K_S$ and $Xi_c^0to Sigma^0 K_S$. The decay asymmetries for all the channels with a kaon in their final states are found to be large in magnitude and negative in sign.
Based on 2.93 fb$^{-1}$ $e^+e^-$ collision data taken at center-of-mass energy of 3.773 GeV by the BESIII detector, we report searches for the singly Cabibbo-suppressed decays $D^{+}toomegapi^{+}$ and $D^{0}toomegapi^{0}$. A double tag technique is used to measure the absolute branching fractions $mathcal{B}(D^{+}toomegapi^{+})=(2.79pm0.57pm0.16)times 10^{-4}$ and $mathcal{B}(D^{0}toomegapi^{0})=(1.17pm0.34pm0.07)times 10^{-4}$, with statistical significances of $5.5sigma$ and $4.1sigma$, respectively. We also present measurements of the absolute branching fractions for the related $eta pi$ decay modes. We find $mathcal{B}(D^{+}toetapi^{+})=(3.07pm0.22pm0.13)times10^{-3}$ and $mathcal{B}(D^{0}toetapi^{0})=(0.65pm0.09pm0.04)times10^{-3}$, which are consistent with the current world averages. The first and second uncertainties are statistical and systematic, respectively.
Using 567 $pb^{-1}$ of data collected with the BESIII detector at a center-of-mass energy of $sqrt{s}=$ 4.599 $GeV$, near the $Lambda_{c}^{+}Lambda_{c}^{-}$ threshold, we study the singly Cabibbo-suppressed decays $Lambda_c^{+}to ppi^{+}pi^{-}$ and $Lambda_c^{+}to pK^{+}K^{-}$. By normalizing with respect to the Cabibbo-favored decay $Lambda_c^{+}to pK^{-}pi^{+}$, we obtain ratios of branching fractions: $frac{mathcal{B}(Lambda_c^{+}to ppi^{+}pi^{-})}{mathcal{B}(Lambda_c^{+}to pK^{-}pi^{+})}$ = $(6.70 pm 0.48 pm 0.25)%$, $frac{mathcal{B}(Lambda_c^{+}to pphi)}{mathcal{B}(Lambda_c^{+}to pK^{-}pi^{+})}$ = $(1.81 pm 0.33 pm 0.13)%$, and $frac{mathcal{B}(Lambda_c^{+}to pK^{+}K^{-}_{text{non-}phi})}{mathcal{B}(Lambda_c^{+}to pK^{-}pi^{+})}$ = $(9.36 pm 2.22 pm 0.71)times10^{-3}$, where the uncertainties are statistical and systematic, respectively. The absolute branching fractions are also presented. Among these measurements, the decay $Lambda_c^{+}to ppi^{+}pi^{-}$ is observed for the first time, and the precision of the branching fraction for $Lambda_c^{+}to pK^{+}K^{-}_{text{non-}phi}$ and $Lambda_c^{+}to pphi$ is significantly improved.
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