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Register a new userInvestigation of the Lightest Hybrid Meson Candidate with a Coupled-Channel Analysis of $bar{p}p$-, $pi^- p$- and $pipi$-Data
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Based on new insights from two recent coupled-channel analyses of $bar{p}p$ annihilation together with $pipi$-scattering data and of $pi^- p$ data, this paper aims at a better understanding of the spin-exotic $pi_1$ resonances in the light meson sector. The Crystal Barrel Collaboration observed the $pi_1$-wave in $bar{p}p$ annihilations in flight for the first time with the coupling to $pi^0eta$ in the reaction $bar{p}p,rightarrow,pi^0pi^0eta$ with a sophisticated coupled-channel approach. Another refined coupled-channel analysis of the P- and D-waves in the $pieta$ and $pieta^prime$ system based on data measured at COMPASS has been performed by the JPAC group. In that study the two spin-exotic signatures listed in the PDG, the $pi_1(1400)$ and $pi_1(1600)$, with a separate coupling to $pieta$ and $pieta^prime$ can be described by a single pole. In this paper, both analyses, the one with the three $bar{p}p$ annihilation channels into $pi^0pi^0eta$, $pi^0etaeta$ and $K^+K^-pi^0$ and 11 different $pipi$-scattering data sets and the one with the P- and D-wave data in the $pieta$ and $pieta^prime$ systems measured at COMPASS, are subjected to a combined coupled channel analysis. By utilizing the K-matrix approach and realizing the analyticity via Chew-Mandelstam functions the $pi_1$ wave can be well described by a single pole for both systems, $pieta$ and $pieta^prime$. The mass and width of the $pi_1$-pole are measured to be $(1561.6 , pm , 3.0 , ^{+6.6}_{-2.6},), mathrm{MeV/c}^2$ and $(388.1 , pm , 5.4 , ^{+0.2}_{-14.1},), mathrm{MeV}$.
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A partial wave analysis of antiproton-proton annihilation data in flight at 900 $MeV/c$ into $pi^0 pi^0 eta$ , $pi^0 eta eta$ and $K^+ K^- pi^0$ is presented. The data were taken at LEAR by the Crystal Barrel experiment in 1996. The three channels have been coupled together with $pipi$-scattering isospin I=0 S- and D-wave as well as I=1 P-wave data utilizing the K-matrix approach. Analyticity is treated using Chew-Mandelstam functions. In the fit all ingredients of the K-matrix, including resonance masses and widths, were treated as free parameters. In spite of the large number of parameters, the fit results are in the ballpark of the values published by the Particle Data Group. In the channel $pi^0 pi^0 eta$ a significant contribution of the spin exotic $I^G=1^-$ $J^{PC}=1^{-+}$ $pi_1$-wave with a coupling to $pi^0 eta$ is observed. Furthermore the contributions of $phi(1020) pi^0$ and $K^*(892)^pm K^mp$ in the channel $K^+ K^- pi^0$ have been studied in detail. The differential production cross section for the two reactions and the spin-density-matrix elements for the $phi(1020)$ and $K^*(892)^pm$ have been extracted. No spin-alignment is observed for both vector mesons. The spin density matrix elements have been also determined for the spin exotic wave.
Using a data sample of $772 times 10^6$ BB pairs collected on the ${Upsilon}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we report the observations of $B^0to p{bar p}pi^+pi^-$ and $B^+ to p{bar p}pi^+pi^0$. We measure a decay branching fraction of $(0.83 pm 0.17 pm 0.17) times 10^-6$ in $B^0to p{bar p}pi^+pi^-$ for $M_{pi^+pi^-} < 1.22 GeV/c^2$ with a significance of 5.5 standard deviations. The contribution from $B0 to p{bar p}K^0$ is excluded. We measure a decay branching fraction of $(4.58 pm 1.17 pm 0.67) times 10^-6$ for $B^+ to p{bar p}pi^+pi^0$ with $M_{pi^+pi^0} < 1.3 GeV/c^2$ with a significance of 5.4 standard deviations. We study the difference of the $M_{p{bar p}}$ distributions in $B^0to p{bar p}pi^+pi^-$ and $B^+ to p{bar p}pi^+pi^0$.
The s-channel annihilation of proton and antiproton into a neutral pion and a real or virtual photon followed by lepton pair emission is studied. Such mechanism is expected to play a role at moderate values of the total energy $sqrt{s}$, when the pion is emitted around $90^{circ}$ in the center of mass. A fair comparison with the existing data is obtained taking into account scattering and annihilation channels. The cross section is calculated and numerical results are given in the kinematical range accessible in the PANDA experiment at FAIR.
We report a new extraction of nucleon resonance couplings using pi- photoproduction cross sections on the neutron. The world database for the process gamma n --> pi- p above 1 GeV has quadrupled with the addition of new differential cross sections from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab in Hall B. Differential cross sections from CLAS have been improved with a new final-state interaction determination using a diagramatic technique taking into account the NN and piN final-state interaction amplitudes. Resonance couplings have been extracted and compared to previous determinations. With the addition of these new cross sections, significant changes are seen in the high-energy behavior of the SAID cross sections and amplitudes.
In this work, the triangle singularity mechanism is investigated in the $psi(2S) to p bar{p} eta / p bar{p} pi^0$ process. The triangle loop composed by $J/psi$, $eta$ and $p$ has a singularity in the physical kinematic range for the $psi(2S) to p bar{p} eta / p bar{p} pi^0$ process, and it would generate a very narrow peak in the invariant mass spectrum of $peta (pi)$ around $1.56387$ GeV, which is far away from both the threshold and relative resonances. In these processes, all the involved vertices are constrained by the experimental data. Thus, we can make a precise model independent prediction here. It turns out that the peak in the $peta$ invariant mass spectrum is visible, while it is very small in the $ppi^0$ invariant mass spectrum. We expect this effect shown in $p bar{p} eta$ final state can be observed by the Beijing Spectrometer (BESIII) and Super Tau-Charm Facility (STCF) in the future.
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