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SUMMARY:New insights into strong dynamics and $CP$ violation effects in $B
  \\to K \\pi \\pi$ decays at LHCb
DTSTART:20260421T090000Z
DTEND:20260421T100000Z
DTSTAMP:20260526T081000Z
UID:indico-event-1675176@indico.cern.ch
CONTACT:ep-seminars.colloquia@cern.ch
DESCRIPTION:Speakers: Youhua Yang (University of Chinese Academy of Scienc
 es (CN))\n\nPLEASE NOTE THIS SEMINAR WILL BE VIA ZOOM ONLY - the speaker w
 ill connect remotely\n \n \nAn amplitude analysis of the charmless three
 -body decay $B^+ \\to K^+ \\pi^+ \\pi^-$ is presented\, based on $pp$ coll
 ision data recorded with the LHCb detector at $\\sqrt{s}=7$ and $8\\\,\\te
 xt{TeV}$\, corresponding to an integrated luminosity of $3\\\,\\text{fb}^{
 -1}$.\nThe dominant $K^+\\pi^-$ and $\\pi^+\\pi^-$ S-wave contributions po
 se the greatest modelling challenge.  Results are presented with three co
 mplementary approaches to these contributions: a physically motivated isob
 ar model incorporating advanced dispersive $\\pi\\pi$ scattering amplitude
 s\, the K-matrix formalism\, and a quasi-model-independent method in which
  magnitudes and phases representing individual S-waves are free to vary in
  bins of the $K^+\\pi^-$ and $\\pi^+\\pi^-$ mass. The results from all thr
 ee approaches are consistent.\nImproved treatment of the scalar sector res
 olves several long-standing puzzles. Relaxing assumptions related to the $
 K^*_0(1430)^0$ resonance reduces its branching fraction by a factor of 4-8
 \, bringing it into agreement with QCD factorisation expectations.  As a 
 consequence of the improved S-wave modelling\, the ad-hoc $f_X(1300) \\to 
 \\pi\\pi$ component\, introduced in previous amplitude analyses of $B^+ \\
 to K^+ \\pi^+ \\pi^-$ decays\, is no longer required. \nSix $CP$-violatin
 g phenomena are established or observed for the first time. These include 
 short-distance $CP$ violation in $B^+ \\to \\rho(770)^0 K^+$\, $CP$ violat
 ion mediated by long-distance final-state interactions in $B^+ \\to f_2(12
 70) K^+$\, the first evidence for $CP$ violation involving a spin-3 resona
 nce\, and significant effects in the interference between different $\\pi\
 \pi$ partial waves (S-P and S-D).  \nThe results offer new insight into s
 trong dynamics as well as the origin of $CP$ violation in $B \\to K\\pi\\p
 i$ decays.\n \n \n \n\nhttps://indico.cern.ch/event/1675176/\n\nZoom: h
 ttps://cern.zoom.us/j/63147586874?pwd=xJkAKWXRT5uzhaeJNsZc8mUBasJpYM.1
LOCATION:CERN
URL:https://indico.cern.ch/event/1675176/
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