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SUMMARY:Recent results  on kaon physics from  the OKA experiment
DTSTART;VALUE=DATE-TIME:20241022T123000Z
DTEND;VALUE=DATE-TIME:20241022T130000Z
DTSTAMP;VALUE=DATE-TIME:20260517T032123Z
UID:indico-contribution-4080@cern.ch
DESCRIPTION:Speakers: Vladimir Obraztsov (Institute for High Energy Physic
 s - "NRC KI")\nThe talk is devoted to the latest results from the OKA coll
 aboration. The OKA setup is using the RF-separated 17.7 GeV/c momentum kao
 n beam of the U-70 accelerator.  The data corresponds to the flux of $2.62
 ·10^{10}$ «live» kaons entering the decay volume.\nA missing mass analy
 sis is performed to search for an  invisible pseudoscalar axion-like  part
 icle(ALP) in the decay $K^+ \\rightarrow \\pi^+\\pi^0 a $. No signal is ob
 served\,the 90% CL upper limit is changing from $2.5·10^{-6}$  to $2·10^
 {-7}$  for the ALP mass from 0 to 200 MeV.   \nSeveral rare EM decays are 
 investigated:\nA new precise measurement of the vector and axial-vector fo
 rm factor difference $F_V − F_A$  in the    $K^+ \\rightarrow \\mu^+ \\n
 u \\gamma$  decay is reported. About 144K events are selected. The prelimi
 nary result is $F_V − F_A = 0.135 \\pm  0.017(stat)\\pm 0.024(syst)$ whi
 ch differs by $\\sim 3 \\sigma$ from $χPT(O(p^4))$ and by 1.5 σ from the
  Lattice calculations.    \nThe  $K^+ \\rightarrow \\mu^+ \\nu \\pi^0 \\ga
 mma (K\\mu3\\gamma)$ decay  is studied with the high statistics of  more t
 han 1000 signal events  with  the energy of the emitted photon in the rest
  frame of the decaying kaon $E_\\gamma > 30$ MeV.                         
   Using       $4.48 · 10^6$ events of the decay  the  ratio Br($K\\mu3\\g
 amma$)/Br($K\\mu3$) is found to be $(4.45 \\pm 0.25(stat)) · 10^{−4}$. 
 From this value\, using Br(Kµ3) = 3.352% we get Br($K\\mu3\\gamma) = (1.4
 92 ± 0.085(stat)) · 10^{−5}$. Our result  is preliminary\, with system
 atic errors being estimated.    \nA rare EM decay  $K^+ \\rightarrow \\pi^
 + \\pi^0 \\pi^0  \\gamma$  is observed for the first time on the statistic
 s of ~50 events with $E_\\gamma >10$ MeV. The branching is measured to be 
                                                                           
               Br$ = (3.7 \\pm 0.9 \\pm 0.3 ) · 10^{-6}   E_\\gamma > 10$ 
 МэВ \nA super-rare EM decay $K^+ \\rightarrow e^+ \\nu \\pi^0 \\pi^0 \\
 pi^0 $     is searched for\, no events were observed\, the upper limit set
   is:  Br$ \n\nhttps://indico.particle.mephi.ru/event/436/contributions/40
 80/
LOCATION: Petrovskiy hall
URL:https://indico.particle.mephi.ru/event/436/contributions/4080/
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