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Register a new userAmplitude analysis of the $chi_{c1} to etapi^+pi^-$ decays
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M. Ablikim
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Using $448.0 times 10^6$~$psi(3686)$ events collected with the BESIII detector, an amplitude analysis is performed for $psi(3686)togammachi_{c1}$, $chi_{c1}toetapi^+pi^-$ decays. The most dominant two-body structure observed is $a_0(980)^{pm}pi^{mp}$; $a_0(980)^{pm}toetapi^{pm}$. The $a_0(980)$ line shape is modeled using a dispersion relation, and a significant non-zero $a_0(980)$ coupling to the $eta^{prime}pi$ channel is measured. We observe $chi_{c1}to a_2(1700)pi$ production for the first time, with a significance larger than 17$sigma$. The production of mesons with exotic quantum numbers, $J^{PC}=1^{-+}$, is investigated, and upper limits for the branching fractions $chi_{c1}to pi_1(1400)^{pm}pi^{mp}$, $chi_{c1}to pi_1(1600)^{pm}pi^{mp}$, and $chi_{c1}topi_1(2015)^{pm}pi^{mp}$, with subsequent $pi_1(X)^{pm} to etapi^{pm}$ decay, are determined.
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The decays $chi_{c1} rightarrow J/psi mu^+ mu^-$ and $chi_{c2} rightarrow J/psi mu^+ mu^-$ are observed and used to study the resonance parameters of the $chi_{c1}$ and $chi_{c2}$ mesons. The masses of these states are measured to be m(chi_{c1}) = 3510.71 pm 0.04(stat) pm 0.09(syst)MeV,, m(chi_{c2}) = 3556.10 pm 0.06(stat) pm 0.11(syst)MeV,, where the knowledge of the momentum scale for charged particles dominates the systematic uncertainty. The momentum-scale uncertainties largely cancel in the mass difference m(chi_{c2}) - m(chi_{c1}) = 45.39 pm 0.07(stat) pm 0.03(syst)MeV,. The natural width of the $chi_{c2}$ meson is measured to be $$Gamma(chi_{c2}) = 2.10 pm 0.20(stat) pm 0.02(syst)MeV,.$$ These results are in good agreement with and have comparable precision to the current world averages.
The Dalitz plot analysis technique is used to study the resonant substructures of $B^{-} to D^{+} pi^{-} pi^{-}$ decays in a data sample corresponding to 3.0 ${rm fb}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high $D^{+}pi^{-}$ mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the $D^{+}pi^{-}$ S-wave together with virtual contributions from the $D^{*}(2007)^{0}$ and $B^{*0}$ states, and components corresponding to the $D^{*}_{2}(2460)^{0}$, $D^{*}_{1}(2680)^{0}$, $D^{*}_{3}(2760)^{0}$ and $D^{*}_{2}(3000)^{0}$ resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in $B^{-} to D^{+} pi^{-} pi^{-}$ decays. The $D^{+}pi^{-}$ S-wave has phase motion consistent with that expected due to the presence of the $D^{*}_{0}(2400)^{0}$ state. These results constitute the first observations of the $D^{*}_{3}(2760)^{0}$ and $D^{*}_{2}(3000)^{0}$ resonances.
We report the first observation of the radiative decay of the $Upsilon(1S)$ into a charmonium state. The statistical significance of the observed signal of $Upsilon(1S) to gamma chi_{c1}$ is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br($Upsilon(1S) to gamma chi_{c1}$) = (4.7^{+2.4}_{-1.8} (stat) ^{+0.4}_{-0.5} (sys)) * 10^{-5}. We also searched for $Upsilon(1S)$ radiative decays into $chi_{c0,2}$ and $eta_c(1S,2S)$ and set upper limits on their branching fractions. These results are obtained from a 24.9 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at a center-of-mass energy equal to the $Upsilon(2S)$ mass using $Upsilon(1S)$ tagging by the $Upsilon(2S) to Upsilon(1S) pi^+pi^-$ transitions.
Using a total of $9.0~mathrm{fb}^{-1}$ of $e^+e^-$ collision data with center-of-mass energies between 4.15 and 4.30 GeV collected by the BESIII detector, we search for the processes $e^+e^-to gamma X(3872)$ with $X(3872)topi^0chi_{cJ}$ for $J=0,1,2$. We report the first observation of $X(3872)topi^{0}chi_{c1}$, a new decay mode of the $X(3872)$, with a statistical significance of more than 5$sigma$. Normalizing to the previously established process $e^+e^-to gamma X(3872)$ with $X(3872)topi^+pi^-J/psi$, we find ${cal B}(X(3872) to pi^0 chi_{c1})/{cal B}(X(3872) to pi^+pi^- J/psi) = 0.88^{+0.33}_{-0.27}pm0.10$, where the first error is statistical and the second is systematic. We set 90% confidence level upper limits on the corresponding ratios for the decays to $pi^0chi_{c0}$ and $pi^0chi_{c2}$ of 19 and 1.1, respectively.
We report inclusive and exclusive measurements for $chi_{c1}$ and $chi_{c2}$ production in $B$ decays. We measure $mathcal{B}(B to chi_{c1} X)$= $(3.03 pm 0.05(mbox{stat}) pm 0.24(mbox{syst})) times 10^{-3}$ and $mathcal{B}(B to chi_{c2} X)$= $(0.70 pm 0.06(mbox{stat}) pm 0.10(mbox{syst})) times 10^{-3}$. For the first time, $chi_{c2}$ production in exclusive $B$ decays in the modes $B^0 to chi_{c2}pi^- K^+$ and $B^+ to chi_{c2} pi^+ pi^- K^+$ has been observed, along with first evidence for the $B^+ to chi_{c2} pi^+ K_S^0$ decay mode. For $chi_{c1}$ production, we report the first observation in the $B^+ to chi_{c1} pi^+ pi^- K^+$, $B^0 to chi_{c1} pi^+ pi^- K_S^0$ and $B^0 to chi_{c1} pi^0 pi^- K^+$ decay modes. Using these decay modes, we observe a difference in the production mechanism of $chi_{c2}$ in comparison to $chi_{c1}$ in $B$ decays. In addition, we report searches for $X(3872)$ and $chi_{c1}(2P)$ in the $B^+ to (chi_{c1} pi^+ pi^-) K^+$ decay mode. The reported results use $772 times 10^{6}$ $Boverline{B}$ events collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider.
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