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The process e+e- ->pi+pi- has been studied with the SND detector at VEPP-2M e+e- collider in the vicinity of phi(1020) resonance. From the analysis of the energy dependence of measured cross section the branching ratio B(phi->pi+pi-)=(7.1+-1.1+-0.9)*10^{-5} and the phase psi_pi=-(34+-4+-3)degrees of interference with the non-resonant pi+pi- production amplitude were obtained.
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We present a study of the reaction e+e- --> pi+pi-pi0 at the phi peak W=M(phi)=1019.4 MeV observed with the KLOE detector at Dafne. The reaction is dominated by phi production and decay, e+e- --> phi --> pi+pi-pi0. From a fit to the Dalitz plot density distribution we obtain the rho-meson parameters for its three charge states. We also find the relative amplitudes for phi --> rhopi and phi -> pi+pi-pi0 and the cross-section for e+e- --> omega pi0 with omega --> pi+pi-.
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.
Based on a sample of $2.25times 10^{8} J/psi$ events taken with the BESIII detector at the BEPCII collider, we present the results of a study of the decay $J/psito eta phipi^{+}pi^{-}$. The $Y(2175)$ resonance is observed in the invariant mass spectrum of $phi f_{0}(980)$ with a statistical significance of greater than $10sigma$. The corresponding mass and width are determined to be $M=2200pm 6 mathrm{(stat.)} pm 5mathrm{(syst.)} mathrm{MeV}/c^{2}$ and $Gamma=104pm 15mathrm{(stat.)}pm 15mathrm{(syst.)}$ MeV, respectively, and the product branching fraction is measured to be $mathcal{B}(J/psitoeta Y(2175)$, $Y(2175)to phi f_{0}(980)$, $f_{0}(980)to pi^{+}pi^{-})= (1.20pm 0.14mathrm{(stat.)}pm 0.37 mathrm{(syst.)})times 10^{-4}$. The results are consistent within errors with those of previous experiments. We also measure the branching fraction of $J/psito phi f_1(1285)$ with $f_1(1285)to etapi^{+}pi^{-}$ and set upper limits on the branching fractions for $J/psito phieta(1405)$/$phi X(1835)$/$phi X(1870)$ with $eta(1405)$/$X(1835)$/$X(1870)to etapi^{+}pi^{-}$ at the 90% confidence level.
A measurement of the rate for the wrong-sign decay D0 -> K+ pi- pi+ pi- relative to that for the right-sign decay D0 -> K- pi+ pi+ pi- is presented. Using 791 fb-1 of data collected with the Belle detector, we obtain a branching fraction ratio of R_WS = [0.324 +- 0.008 (stat) +- 0.007 (sys)]%. Multiplying this ratio by the world average value for the branching fraction B(D0 -> K- pi+ pi+ pi-) gives a branching fraction B(D0 -> K+ pi- pi+ pi-) = (2.61 +- 0.06 +0.09 -0.08) x 10-4.
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