اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA new search for the $K_{L} to pi^0 u overline{ u}$ and $K_{L} to pi^{0} X^{0}$ decays
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We searched for the $CP$-violating rare decay of neutral kaon, $K_{L} to pi^0 u overline{ u}$, in data from the first 100 hours of physics running in 2013 of the J-PARC KOTO experiment. One candidate event was observed while $0.34pm0.16$ background events were expected. We set an upper limit of $5.1times10^{-8}$ for the branching fraction at the 90% confidence level (C.L.). An upper limit of $3.7times10^{-8}$ at the 90% C.L. for the $K_{L} to pi^{0} X^{0}$decay was also set for the first time, where $X^{0}$ is an invisible particle with a mass of 135 MeV/$c^{2}$.
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A search for the rare decay $K_L !to! pi^0 u overline{ u}$ was performed. With the data collected in 2015, corresponding to $2.2 times 10^{19}$ protons on target, a single event sensitivity of $( 1.30 pm 0.01_{rm stat} pm 0.14_{rm syst} ) times 10^{
-9}$ was achieved and no candidate events were observed. We set an upper limit of $3.0 times 10^{-9}$ for the branching fraction of $K_L !to! pi^0 u overline{ u}$ at the 90% confidence level (C.L.), which improved the previous limit by almost an order of magnitude. An upper limit for $K_L !to! pi^0 X^0$ was also set as $2.4 times 10^{-9}$ at the 90% C.L., where $X^0$ is an invisible boson with a mass of $135~{rm MeV}/c^2$.
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A search for charmless three-body decays of $B^0$ and $B_{s}^0$ mesons with a $K_{rm S}^0$ meson in the final state is performed using the $pp$ collision data, corresponding to an integrated luminosity of $1.0,mbox{fb}^{-1}$, collected at a centre-of
-mass energy of $7mathrm{,Tekern -0.1em V}$ recorded by the LHCb experiment. Branching fractions of the $B_{(s)}^0 to K_{rm S}^0 h^{+} h^{prime -}$ decay modes ($h^{(prime)} = pi, K$), relative to the well measured $B^0 to K_{rm S}^0 pi^{+} pi^{-}$ decay, are obtained. First observation of the decay modes $B_s^0 to K_{rm S}^0 K^{pm} pi^{mp}$ and $B_s^0 to K_{rm S}^0 pi^{+} pi^{-}$ and confirmation of the decay $B^0 to K_{rm S}^0 K^{pm} pi^{mp}$ are reported. The following relative branching fraction measurements or limits are obtained begin{eqnarray*} onumber frac{{cal B}(B^0 to K_{rm S}^0 K^{pm} pi^{mp})}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &=& 0.128 pm 0.017 , ({rm stat.}) pm 0.009 , ({rm syst.}) ,, onumber frac{{cal B}(B^0 to K_{rm S}^0 K^{+} K^{-} )}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &=& 0.385 pm 0.031 , ({rm stat.}) pm 0.023 , ({rm syst.}) ,, onumber frac{{cal B}(B_s^0 to K_{rm S}^0 pi^{+} pi^{-} )}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &=& 0.29phantom{0} pm 0.06phantom{0} , ({rm stat.}) pm 0.03phantom{0} , ({rm syst.}) pm 0.02 , (f_s/f_d) ,, onumber frac{{cal B}(B_s^0 to K_{rm S}^0 K^{pm} pi^{mp})}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &=& 1.48phantom{0} pm 0.12phantom{0} , ({rm stat.}) pm 0.08phantom{0} , ({rm syst.}) pm 0.12 , (f_s/f_d) ,, onumber frac{{cal B}(B_s^0 to K_{rm S}^0 K^{+} K^{-} )}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &in& [0.004;0.068] ; {rm at ;; 90% ; CL} ,. end{eqnarray*}
The $K^+ to pi^0 pi^0 e^+ u$ ($K_{e4}^{00}$) decay has been measured with stopped positive kaons for a data sample of 216 events. A comparison of the observed spectra with a Monte Carlo simulation determined the $K_{e4}^{00}$ form factor. The result
s are compatible with the $K^+ to pi^+ pi^- e^+ u$ data, as estimated from the $Delta I=1/2$ rule. We also established that the $K_{e4}^{00}$ channel can be used to determine the $pi$-$pi$ scattering lengths.
Using an $e^{+}e^{-}$ annihilation data sample corresponding to an integrated luminosity of $3.19~mathrm{fb}^{-1}$ and collected at a center-of-mass energy $sqrt{s} = 4.178~mathrm{GeV}$ with the BESIII detector, we measure the absolute branching frac
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