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Register a new userObservation of the decay $Lambda_c^+rightarrow Sigma^- pi^+pi^+pi^0$
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We report the first observation of the decay $Lambda^+_{c}rightarrow Sigma^- pi^+pi^+pi^0$, based on data obtained in $e^+e^-$ annihilations with an integrated luminosity of 567~pb$^{-1}$ at $sqrt{s}=4.6$~GeV. The data were collected with the BESIII detector at the BEPCII storage rings. The absolute branching fraction $mathcal{B}(Lambda^+_{c}rightarrowSigma^-pi^+pi^+pi^0)$ is determined to be $(2.11pm0.33({rm stat.})pm0.14({rm syst.}))%$. In addition, an improved measurement of $mathcal{B}(Lambda^+_{c}rightarrowSigma^-pi^+pi^+)$ is determined as $(1.81pm0.17({rm stat.})pm0.09({rm syst.}))%$.
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Using a low-background sample of $2.6times 10^5$ $J/psirightarrowomegaeta(omegarightarrowpi^{+}pi^{-}pi^{0},etarightarrowgammagamma)$ events, about 5 times larger statistics than previous experiments, we present a Dalitz plot analysis of the decay $omegarightarrowpi^{+}pi^{-}pi^{0}$. It is found that the Dalitz plot distribution differs from the pure $P$-wave phase space with a statistical significance of $18.9sigma$. The parameters from the fit to data are in reasonable agreement with those without the cross-channel effect within the dispersive framework, which indicates that the cross-channel effect in $omegarightarrowpi^+pi^-pi^0$ is not significant.
The decay $D^{+}_{s}rightarrow pi^{+}pi^{+}pi^{-}eta$ is observed for the first time, using $e^+e^-$ collision data corresponding to an integrated luminosity of 6.32 fb$^{-1}$, collected by the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV. The absolute branching fraction for this decay is measured to be $mathcal{B}(D^+_s to pi^+ pi^+ pi^- eta) = (3.12pm0.13_{rm stat.}pm0.09_{rm syst.})$%. The first amplitude analysis of this decay reveals the sub-structures in $D^{+}_{s}rightarrow pi^{+}pi^{+}pi^{-}eta$ and determines the relative fractions and the phases among these sub-structures. The dominant intermediate process is $D^{+}_{s}rightarrow a_1(1260)^+ eta, a_1(1260)^+ rightarrow rho(770)^0pi^+$ with a branching fraction of $(1.73 pm 0.14_{rm stat.} pm 0.08_{rm syst.})$%. We also observe the W-annihilation process $D^{+}_{s}rightarrow a_0(980)^+rho(770)^0$, $a_0(980)^+ to pi^+ eta$ with a branching fraction of $(0.21pm0.08_{rm stat.}pm0.05_{rm syst.})$%, which is larger than the branching fractions of other measured pure W-annihilation decays by one order of magnitude.
The decay $Lambda_b^0 to Lambda_c^+ p overline{p} pi^-$ is observed using $pp$ collision data collected with the LHCb detector at centre-of-mass energies of $sqrt{s}=$ 7 and 8 TeV, corresponding to an integrated luminosity of 3 $fb^{-1}$. The ratio of branching fractions between $Lambda_b^0 to Lambda_c^+ p overline{p} pi^-$ and $Lambda_b^0 to Lambda_c^+ pi^-$ decays is measured to be begin{equation*} frac{mathcal{B}(Lambda_b^0 to Lambda_c^+ p overline{p}pi^-)}{mathcal{B}(Lambda_b^0 to Lambda_c^+ pi^-)} = 0.0540 pm 0.0023 pm 0.0032. end{equation*} Two resonant structures are observed in the $ Lambda_c^+ pi^-$ mass spectrum of the ${Lambda_b^0 to Lambda_c^+ poverline{p} pi^-}$ decays, corresponding to the $Sigma_c(2455)^0$ and $Sigma_c^{*}(2520)^0$ states. The ratios of branching fractions with respect to the decay $Lambda_b^0 to Lambda_c^+ p overline{p} pi^-$ are begin{align*} frac{mathcal{B}(Lambda_b^0 to Sigma_c^0 poverline{p})timesmathcal{B}(Sigma_c^0to Lambda_c^+ pi^-)}{mathcal{B}(Lambda_b^0 to Lambda_c^+ p overline{p}pi^-)} = 0.089pm0.015pm0.006, frac{mathcal{B}(Lambda_b^0 to Sigma_c^{*0} poverline{p})timesmathcal{B}(Sigma_c^{*0}to Lambda_c^+ pi^-)}{mathcal{B}(Lambda_b^0 to Lambda_c^+ p overline{p}pi^-)} = 0.119pm0.020pm0.014. end{align*} In all of the above results, the first uncertainty is statistical and the second is systematic. The phase space is also examined for the presence of dibaryon resonances. No evidence for such resonances is found.
The results of an amplitude analysis of the charmless three-body decay $B^+ rightarrow pi^+pi^+pi^-$, in which $C!P$-violation effects are taken into account, are reported. The analysis is based on a data sample corresponding to an integrated luminosity of $3 text{fb}^{-1}$ of $pp$ collisions recorded with the LHCb detector. The most challenging aspect of the analysis is the description of the behaviour of the $pi^+ pi^-$ S-wave contribution, which is achieved by using three complementary approaches based on the isobar model, the K-matrix formalism, and a quasi-model-independent procedure. Additional resonant contributions for all three methods are described using a common isobar model, and include the $rho(770)^0$, $omega(782)$ and $rho(1450)^0$ resonances in the $pi^+pi^-$ P-wave, the $f_2(1270)$ resonance in the $pi^+pi^-$ D-wave, and the $rho_3(1690)^0$ resonance in the $pi^+pi^-$ F-wave. Significant $C!P$-violation effects are observed in both S- and D-waves, as well as in the interference between the S- and P-waves. The results from all three approaches agree and provide new insight into the dynamics and the origin of $C!P$-violation effects in $B^+ rightarrow pi^+pi^+pi^-$ decays.
Utilizing the data set corresponding to an integrated luminosity of $3.19$ fb$^{-1}$ collected by the BESIII detector at a center-of-mass energy of 4.178 GeV, we perform an amplitude analysis of the $D_s^+topi^+pi^-pi^+$ decay. The sample contains 13
,797 candidate events with a signal purity of $sim$80%. We use a quasi-model-independent approach to measure the magnitude and phase of the $D_s^+topi^+pi^-pi^+$ decay, where the ${cal P}$ and ${cal D}$ waves are parameterized by a sum of three Breit-Wigner amplitudes $rho(770)^0$, $rho(1450)^0$, and $f_2(1270)$. The fit fractions of different decay channels are also reported.
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