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Register a new userDoubly Cabibbo-suppressed decays of antitriplet charmed baryons
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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.
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The hadronic two-body weak decays of the doubly charmed baryons $Xi_{cc}^{++}, Xi_{cc}^+$ and $Omega_{cc}^+$ are studied in this work. To estimate the nonfactorizable contributions, we work in the pole model for the $P$-wave amplitudes and current algebra for $S$-wave ones. For the $Xi_{cc}^{++}to Xi_c^+pi^+$ mode, we find a large destructive interference between factorizable and nonfactorizable contributions for both $S$- and $P$-wave amplitudes. Our prediction of $sim 0.70%$ for its branching fraction is smaller than the earlier estimates in which nonfactorizable effects were not considered, but agrees nicely with the result based on an entirely different approach, namely, the covariant confined quark model. On the contrary, a large constructive interference was found in the $P$-wave amplitude by Dhir and Sharma, leading to a branching fraction of order $(7-16)%$. Using the current results for the absolute branching fractions of $(Lambda_c^+,Xi_c^+)to p K^-pi^+$ and the LHCb measurement of $Xi_{cc}^{++}toXi_c^+pi^+$ relative to $Xi_{cc}^{++}toLambda_c^+ K^- pi^+pi^+$, we obtain $B(Xi_{cc}^{++}toXi_c^+pi^+)_{rm expt}approx (1.83pm1.01)%$ after employing the latest prediction of $B(Xi_{cc}^{++}toSigma_c^{++}overline{K}^{*0})$. Our prediction of $mathcal{B}(Xi_{cc}^{++}toXi_c^+pi^+)approx 0.7%$ is thus consistent with the experimental value but in the lower end. It is important to pin down the branching fraction of this mode in future study. Factorizable and nonfactorizable $S$-wave amplitudes interfere constructively in $Xi_{cc}^+toXi_c^0pi^+$. Its large branching fraction of order 4% may enable experimentalists to search for the $Xi_{cc}^+$ through this mode. That is, the $Xi_{cc}^+$ is reconstructed through the $Xi_{cc}^+toXi_c^0pi^+$ followed by the decay chain $Xi_c^0to Xi^-pi^+to ppi^-pi^-pi^+$.
There has been important experimental progress in the sector of heavy baryons in the past several years. We study the strong decays of the S-wave, P-wave, D-wave and radially excited charmed baryons using the $^3P_0$ model. After comparing the calcul
ated decay pattern and total width with the available data, we discuss the possible internal structure and quantum numbers of those charmed baryons observed recently.
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.
The chiral corrections to the magnetic moments of the spin-$frac{1}{2}$ doubly charmed baryons are systematically investigated up to next-to-next-to-leading order with heavy baryon chiral perturbation theory (HBChPT). The numerical results are calculated up to next-to-leading order: $mu_{Xi^{++}_{cc}}=-0.25mu_{N}$, $mu_{Xi^{+}_{cc}}=0.85mu_{N}$, $mu_{Omega^{+}_{cc}}=0.78mu_{N}$. We also calculate the magnetic moments of the other doubly heavy baryons, including the doubly bottomed baryons (bbq) and the doubly heavy baryons containing a light quark, a charm quark and a bottom quark (${bc}q$ and $[bc]q$): $mu_{Xi^{0}_{bb}}=-0.84mu_{N}$, $mu_{Xi^{-}_{bb}}=0.26mu_{N}$, $mu_{Omega^{-}_{bb}}=0.19mu_{N}$, $mu_{Xi^{+}_{{bc}q}}=-0.54mu_{N}$, $mu_{Xi^{0}_{{bc}q}}=0.56mu_{N}$, $mu_{Omega^{0}_{{bc}q}}=0.49mu_{N}$, $mu_{Xi^{+}_{[bc]q}}=0.69mu_{N}$, $mu_{Xi^{0}_{[bc]q}}=-0.59mu_{N}$, $mu_{Omega^{0}_{[bc]q}}=0.24mu_{N}$.
In this work, we evaluate the lifetimes of the doubly charmed baryons $Xi_{cc}^{+}$, $Xi_{cc}^{++}$ and $Omega_{cc}^{+}$. We carefully calculate the non-spectator contributions at the quark level where the Cabibbo-suppressed diagrams are also include
d. The hadronic matrix elements are evaluated in the simple non-relativistic harmonic oscillator model. Our numerical results are generally consistent with that obtained by other authors who used the diquark model. However, all the theoretical predictions on the lifetimes are one order larger than the upper limit set by the recent SELEX measurement. This discrepancy would be clarified by the future experiment, if more accurate experiment still confirms the value of the SELEX collaboration, there must be some unknown mechanism to be explored.
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