The Hadronic Decay Ratios of η′ → 5π at NLO in χPT (original) (raw)

Chiral dynamics predictions for η′ → ηππ

Journal of High Energy Physics, 2011

The hadronic decays η ′ → ηππ are studied in the frameworks of large-N C Chiral Perturbation Theory, at lowest and next-to-leading orders, and Resonance Chiral Theory in the leading 1/N C approximation. Higher order effects such as ππ final state interactions are taken into account through a detailed unitarization procedure. The inclusion of finite-width effects in the case of RChT is also discussed. The Dalitz plot distribution and the differential branching ratio are computed in both approaches. The predicted Dalitz plot parameters obtained from the different treatments are compared with the most recent measured values. We find that the η ′ → ηππ branching ratios are easily understood, while the Dalitz plot parameters require the inclusion of ππ loops in order to achieve a reasonable agreement. Our final predictions agree with the experimental measurements. We hope our results to be of relevance for present and future experimental analyses of these decays.

Chiral dynamics predictions for η ′ → ηpipi

2016

The hadronic decays η ′ → ηππ are studied in the frameworks of large-N C Chiral Perturbation Theory, at lowest and next-to-leading orders, and Resonance Chiral Theory in the leading 1/N C approximation. Higher order effects such as ππ final state interactions are taken into account through a detailed unitarization procedure. The inclusion of finite-width effects in the case of RChT is also discussed. The Dalitz plot distribution and the differential branching ratio are computed in both approaches. The predicted Dalitz plot parameters obtained from the different treatments are compared with the most recent measured values. We find that the η ′ → ηππ branching ratios are easily understood, while the Dalitz plot parameters require the inclusion of ππ loops in order to achieve a reasonable agreement. Our final predictions agree with the experimental measurements. We hope our results to be of relevance for present and future experimental analyses of these decays.

Prepared for submission to JHEP η and η ′ decays into lepton pairs

2018

In this work, we calculate the branching ratios for the η(η′)→ `` decays, where ` = e, μ. These processes have tiny rates in the Standard Model due to spin flip, loop and electromagnetic suppressions, which could make them sensitive to New Physics effects. In order to provide a reliable input for the Standard Model, we exploit the general analytical properties of the amplitude. For that purpose, we invoke the machinery of Canterbury approximants, which provides a systematic description of the underlying hadronic physics in a data-driven fashion. Given the current experimental discrepancies, we discuss in detail the role of the resonant region and comment on the reliability of χPT calculations. Finally, we discuss the kind of new physics which we think would be relevant to account for them. ar X iv :1 51 2. 09 29 2v 2 [ he pph ] 1 9 Se p 20 16

Η and Η ′ Decays Into Lepton Pairs

Journal of High Energy Physics, 2016

In this work, we calculate the branching ratios for the η(η) → decays, where = e, µ. These processes have tiny rates in the Standard Model due to spin flip, loop and electromagnetic suppressions, which could make them sensitive to New Physics effects. In order to provide a reliable input for the Standard Model, we exploit the general analytical properties of the amplitude. For that purpose, we invoke the machinery of Canterbury approximants, which provides a systematic description of the underlying hadronic physics in a data-driven fashion. Given the current experimental discrepancies, we discuss in detail the role of the resonant region and comment on the reliability of χPT calculations. Finally, we discuss the kind of new physics which we think would be relevant to account for them.

Comment on the η→3π, η→2γ decay rates

Physics Letters B, 1982

The main decay modes of the eta meson are discussed with emphasis on large symmetry breaking effects induced by the mass of the strange quark. It is argued that these SU3-breaking effects amount to corrections involving factors of 2 to 3 in rate in the above decay modes. This is in line with the well-known large correction factors in the nonleptonic decays K S 21r and D O ~ K+K -, zr+Tr -.

The isospin-violating decay η' → 3π0

Physics Letters B, 1984

In an experiment performed at the 70 GeV IHEP accelerator the rare decay r~'(958) ~ 37tO,which violates isospin conservation, has been observed. The six final decay gamma rays are detected in the hodoscope spectrometer GAMS-2000. The branching ratio of this decay is BR(r~' ~ 37r °) = (1.6 ± 0.4) × 10 -3. An estimate of the ratio of the masses of u and d quarks is given. 0.370-2693/84/$ 03.00

η→ 3π at two loops in Chiral Perturbation Theory

Journal of High Energy Physics, 2007

We calculate the decay η → 3π at next-to-next-to-leading order or order p 6 in Chiral Perturbation Theory. The corrections are somewhat larger than was indicated by dispersive estimates. We present numerical results for the Dalitz plot parameters, the ratio r of the neutral to charged decay and the total decay rate. In addition we derive an inequality between the slope parameters of the charged and neutral decay. The experimental charged decay rate leads to central values for the isospin breaking quantities R = 42.2 and Q = 23.2.

Η→Π^0 Γγ Decay Within Unitarized Chiral Perturbation Theory

2003

We improve the calculations of the η→π^0 γγ decay within the context of meson chiral lagrangians. We use a chiral unitary approach for the meson-meson interaction, thus generating the a_0(980) resonance and fixing the longstanding sign ambiguity on its contribution. This also allows us to calculate the loops with one vector meson exchange, thus removing a former source of uncertainty. In addition we ensure the consistency of the approach with other processes. First, by using vector meson dominance couplings normalized to agree with radiative vector meson decays. And, second, by checking the consistency of the calculations with the related γγ→π^0 η reaction. We find an η→π^0 γγ decay width of 0.47± 0.10 eV, in clear disagreement with published data but in remarkable agreement with the most recent measurement.

Η→ Π^{0} Γγ Decay Within a Chiral Unitary Approach Revisited

2008

In view of the recent experimental developments on the experimental side in the η → π 0 γγ decay, and the fact that the Particle Data Group in the on line edition of 2007 reports sizable changes of the radiative decay widths of vector mesons used as input in the theoretical calculations of [1], a reevaluation of the decay width of the η in this channel has been done, reducing its uncertainty by almost a factor of two. The new input of the PDG is used and invariant mass distributions and total widths are compared with the most recent results from AGS, MAMI and preliminary ones of KLOE. The agreement of the theory with the AGS and MAMI data is very good, both for the total rates as well as for the invariant mass distributions of the two photons.

Η→Π0ΓΓ Decay Within a Chiral Unitary Approach

Physical Review D, 2003

We improve the calculations of the η → π 0 γγ decay within the context of meson chiral lagrangians. We use a chiral unitary approach for the meson-meson interaction, thus generating the a 0 (980) resonance and fixing the longstanding sign ambiguity on its contribution. This also allows us to calculate the loops with one vector meson exchange, thus removing a former source of uncertainty. In addition we ensure the consistency of the approach with other processes. First, by using vector meson dominance couplings normalized to agree with radiative vector meson decays. And, second, by checking the consistency of the calculations with the related γγ → π 0 η reaction. We find an η → π 0 γγ decay width of 0.47 ± 0.10 eV, in clear disagreement with published data but in remarkable agreement with the most recent measurement.