Nine-channel unitary three-body fits to COMPASS lineshapes reproduce the a1(1420) enhancement by triangle singularity without requiring a genuine a1(1420) pole.
A Discussion on Triangle Singularities in the $\Lambda_b \to J/\psi K^{-} p$ Reaction
7 Pith papers cite this work. Polarity classification is still indexing.
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abstract
We have analyzed the singularities of a triangle loop integral in detail and derived a formula for an easy evaluation of the triangle singularity on the physical boundary. It is applied to the $\Lambda_b \rightarrow J/\psi K^{-} p$ process via $\Lambda^*$-charmonium-proton intermediate states. Although the evaluation of absolute rates is not possible, we identify the $\chi_{c1}$ and the $\psi(2S)$ as the relatively most relevant states among all possible charmonia up to the $\psi(2S)$. The $\Lambda(1890)\, \chi_{c1}\, p$ loop is very special as its normal threshold and triangle singularities merge at about 4.45 GeV, generating a narrow and prominent peak in the amplitude in the case that the $\chi_{c1}\, p$ is in an $S$-wave. We also see that loops with the same charmonium and other $\Lambda^*$ hyperons produce less dramatic peaks from the threshold singularity alone. For the case of $\chi_{c1}\, p \rightarrow J/\psi\, p$ and quantum numbers $3/2^-$ or $5/2^+$ one needs $P$- and $D$-waves, respectively, in the $\chi_{c1}\, p$, which drastically reduce the strength of the contribution and smooth the threshold peak. In this case we conclude that the singularities cannot account for the observed narrow peak. In the case of $1/2^+$, $3/2^+$ quantum numbers, where $\chi_{c1}\, p \rightarrow J/\psi\, p$ can proceed in an $S$-wave, the $\Lambda(1890)\,\chi_{c1}\,p$ triangle diagram could play an important role, though can neither assert their strength without further input from experiments and lattice QCD calculations.
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Fitting a spectator-isobar three-body unitary amplitude to BESIII K0S K0S pi0 data yields poles at (1277±2±1)-i(12±1±0) MeV for f1(1285) and (1435±2±7)-i(40±2±1) MeV for f1(1420), with the latter traced to a K Kbar* quasi-bound state.
The M1 radiative decay width Pc(4457)(3/2-) → Pc(4312)(1/2-)γ is computed as 6.7 keV (range 2-9 keV) via 19 triangle loops with photon coupling to molecular components.
Measuring the ratio of radiative decay branching fractions from Ds1(2460) can probe the nature of Ds0*(2317) and Ds1(2460) mesons.
Triangle singularities mimicking resonances are analyzed in the presence of final-state rescattering using Landau equations and a scattering formalism enforcing two- and three-body unitarity.
Chiral EFT derivation of the Δ⁻ → p e⁻ e⁻ amplitude including long-range neutrino loops, short-range counterterms, pion-mass dependence for collinear electrons, and a long-range prediction in the degenerate Δ-nucleon mass limit.
Coupled-channel calculations show Pc and Pcs states as molecular bound states with RMS radii 0.5-2 fm when heavy-quark spin symmetry is respected across all channels.
citing papers explorer
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The $a_1(1420)$ in a Unitary Coupled-Channel Three-Body Approach
Nine-channel unitary three-body fits to COMPASS lineshapes reproduce the a1(1420) enhancement by triangle singularity without requiring a genuine a1(1420) pole.
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Three-body unitary determination of the $f_1(1285)$ and $f_1(1420)$ pole positions
Fitting a spectator-isobar three-body unitary amplitude to BESIII K0S K0S pi0 data yields poles at (1277±2±1)-i(12±1±0) MeV for f1(1285) and (1435±2±7)-i(40±2±1) MeV for f1(1420), with the latter traced to a K Kbar* quasi-bound state.
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Radiative decays of dynamically generated pentaquarks in the chiral unitary approach: the $P_c(4457)\to P_c(4312)\,\gamma$ transition
The M1 radiative decay width Pc(4457)(3/2-) → Pc(4312)(1/2-)γ is computed as 6.7 keV (range 2-9 keV) via 19 triangle loops with photon coupling to molecular components.
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What can we learn from the radiative decays of the $D_{s1}(2460)$ meson?
Measuring the ratio of radiative decay branching fractions from Ds1(2460) can probe the nature of Ds0*(2317) and Ds1(2460) mesons.
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Effects of Final State Interactions on Landau Singularities
Triangle singularities mimicking resonances are analyzed in the presence of final-state rescattering using Landau equations and a scattering formalism enforcing two- and three-body unitarity.
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Neutrinoless double-beta decay of the $\Delta^-$ resonance
Chiral EFT derivation of the Δ⁻ → p e⁻ e⁻ amplitude including long-range neutrino loops, short-range counterterms, pion-mass dependence for collinear electrons, and a long-range prediction in the degenerate Δ-nucleon mass limit.
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Study of the molecular Properties of the $P_c$ and $P_{cs}$ States
Coupled-channel calculations show Pc and Pcs states as molecular bound states with RMS radii 0.5-2 fm when heavy-quark spin symmetry is respected across all channels.