The COMPASS Collaboration experiment recently discovered a new isovector resonancelike signal with axial-vector quantum numbers, the a(1)(1420), decaying to f(0)(980)(pi). With a mass too close to and a width smaller than the axial-vector ground state a(1)(1260), it was immediately interpreted as a new light exotic meson, similar to the X, Y, Z states in the hidden-charm sector. We show that a resonancelike signal fully matching the experimental data is produced by the decay of the a(1) (1260) resonance into K* (-> K pi) (K) over bar and subsequent rescattering through a triangle singularity into the coupled f(0)(980)p channel. The amplitude for this process is calculated using a new approach based on dispersion relations. The triangle-singularity model is fitted to the partial-wave data of the COMPASS experiment. Despite having fewer parameters, this fit shows a slightly better quality than the one using a resonance hypothesis and thus eliminates the need for an additional resonance in order to describe the data. We thereby demonstrate for the first time in the lightmeson sector that a resonancelike structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect.

Triangle Singularity as the Origin of the a1(1420)

Bradamante, F.;Bressan, A.;Chatterjee, C.;D’Ago, D.;Dalla Torre, S.;Dasgupta, S.;Kerbizi, A.;Levorato, S.;Makke, N.;Martin, A.;Moretti, A.;Sbrizzai, G.;
2021-01-01

Abstract

The COMPASS Collaboration experiment recently discovered a new isovector resonancelike signal with axial-vector quantum numbers, the a(1)(1420), decaying to f(0)(980)(pi). With a mass too close to and a width smaller than the axial-vector ground state a(1)(1260), it was immediately interpreted as a new light exotic meson, similar to the X, Y, Z states in the hidden-charm sector. We show that a resonancelike signal fully matching the experimental data is produced by the decay of the a(1) (1260) resonance into K* (-> K pi) (K) over bar and subsequent rescattering through a triangle singularity into the coupled f(0)(980)p channel. The amplitude for this process is calculated using a new approach based on dispersion relations. The triangle-singularity model is fitted to the partial-wave data of the COMPASS experiment. Despite having fewer parameters, this fit shows a slightly better quality than the one using a resonance hypothesis and thus eliminates the need for an additional resonance in order to describe the data. We thereby demonstrate for the first time in the lightmeson sector that a resonancelike structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect.
2021
Pubblicato
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.082501
File in questo prodotto:
File Dimensione Formato  
2021_prl127_082501.pdf

accesso aperto

Descrizione: Articolo
Tipologia: Documento in Versione Editoriale
Licenza: Creative commons
Dimensione 463.03 kB
Formato Adobe PDF
463.03 kB Adobe PDF Visualizza/Apri
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2994511
Citazioni
  • ???jsp.display-item.citation.pmc??? 0
  • Scopus 13
  • ???jsp.display-item.citation.isi??? 12
social impact