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SUMMARY:Light-Meson Spectroscopy at COMPASS
DTSTART:20260623T130000Z
DTEND:20260623T134500Z
DTSTAMP:20260630T115500Z
UID:indico-event-18316@indico.global
DESCRIPTION:Speakers: David Spülbeck (University of Bonn)\n\nAbstract:\nT
 he COMPASS experiment at the CERN SPS is a multi-purpose fixed-target expe
 riment designed to study the strong interaction. Using a $190$ GeV/c hadro
 n beam\, COMPASS has recorded the world’s largest data set of diffractiv
 e scattering reactions. These data provide a unique opportunity to study t
 he excitation spectrum of non-strange and strange light mesons with masses
  up to about $2.5$ GeV/c${}^2$\, as well as to search for exotic states be
 yond the constituent quark model. This is achieved through comprehensive p
 artial-wave analyses of various final states\, in which the data are decom
 posed into amplitudes with well-defined quantum numbers\, allowing for the
  extraction of resonance parameters of the contributing mesonic states.\nI
 n this talk\, recent experimental results from the light isovector sector 
 arepresented. Results on the exotic $\\pi_1(1600)$\, the lightest hybrid-m
 eson candidate with $J^{PC} = 1^{−+}$\, are highlighted. This state has 
 been observed at COMPASS in all predicted dominant decay channels\, includ
 ing $\\eta′\\pi^-$ and $f_1(1285)\\pi^-$ (both in the $\\pi^-\\pi^-\\pi^
 +\\eta$ final state)\, as well as $b_1(1235)\\pi^-$ (observed in the $\\om
 ega\\pi^-\\pi^0$ final state). The $K^0_SK^−$ final state allows for a p
 recise determination of excited $a_J$ states with even spin $J$ and enable
 s an exclusive study of these mesons at high masses\, a hitherto unexplore
 d region. The analysis of the $K^−\\pi^-\\pi^+$ final state is further p
 resented\, representing the most comprehensive measurement of the strange-
 meson spectrum to date and providing first evidence for a supernumerary $J
 ^P = 0^−$ state.\nIn addition\, the analysis of non-resonant double-Regg
 e exchange processesusing $\\eta(′)\\pi$ data in the high-mass region is
  discussed. This constitutes the first event-based likelihood fit to the 
 full COMPASS data set in this regime and improves the understanding of no
 n-resonant production mechanisms in light meson spectroscopy.\n\nhttps://i
 ndico.global/event/18316/
LOCATION:NB2/158 (RUB)
URL:https://indico.global/event/18316/
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