Observation of K+→π+π0π0γ decay Artamonov, A. V.; Bychkov, V. N.; Donskov, S. V. ...
The European physical journal. C, Particles and fields,
04/2024, Volume:
84, Issue:
4
Journal Article
Peer reviewed
Open access
The
K
+
→
π
+
π
0
π
0
γ
decay is observed by the OKA collaboration. About 60 events of the decay observed with signal:noise
≈
1
. The branching ratio obtained by normalization to
K
+
→
π
+
π
0
π
0
is ...measured to be
(
3.7
±
0.9
(
s
t
a
t
)
±
0.3
(
s
y
s
t
)
)
×
10
-
6
for
E
γ
∗
>
10
MeV
. The branching ratio,
γ
energy spectrum and angular distribution are consistent with ChPT prediction.
A high-statistics data sample of the
K
+
decays is recorded by the OKA collaboration. A missing mass analysis is performed to search for a light invisible pseudoscalar axion-like particle (ALP)
a
in ...the decay
K
+
→
π
+
π
0
a
. No signal is observed, and the upper limits for the branching ratio of the decay are calculated. The
90
%
confidence level upper limit changes from
2.5
·
10
-
6
to
2
·
10
-
7
for the ALP mass from 0 to 200 MeV/
c
2
, except for the region of
π
0
mass, where the upper limit is
4.4
·
10
-
6
.
Abstract A high statistics data sample of the decays of $$K^+$$ K+ mesons to three charged particles was accumulated by the OKA experiment in 2012 and 2013. This allowed to select a clean sample of ...about 450 events with $$K^{+}\rightarrow \pi ^{+}\pi ^{-}\pi ^{+}\gamma $$ K+→π+π-π+γ decays with the energy of the photon in the kaon rest frame greater than 30 MeV. The measured branching fraction of the $$K^{+}\rightarrow \pi ^{+}\pi ^{-}\pi ^{+}\gamma $$ K+→π+π-π+γ , with $$E_{\gamma }^{*} > 30\ \hbox {MeV}$$ Eγ∗>30MeV is equal to $$(0.71 \pm 0.05) \times 10^{-5}$$ (0.71±0.05)×10-5 . The measured differential branching fraction over photon energy is compared with the prediction of the chiral perturbation theory to $${\mathcal {O}}(p^{4})$$ O(p4) . A search for an up-down asymmetry of the photon with respect to the hadronic system decay plane is also performed.
Abstract A high statistics data sample of the $$K^{+}\rightarrow \mu ^{+}\nu _{\mu }$$ K+→μ+νμ decay was accumulated by the OKA experiment in 2012. The missing mass analysis was performed to search ...for the decay channel $$K^{+}\rightarrow \mu ^{+}\nu _{H}$$ K+→μ+νH with a hypothetic stable heavy neutrino in the final state. The obtained missing mass spectrum does not show peaks that could be attributed to existence of stable heavy neutrinos in the mass range $$(270< m_{\nu _{H}} < 375)$$ (270<mνH<375) MeV$$/c^{2}$$ /c2 . As a result, upper limits on the branching ratio and on the value of the mixing element $$|U_{\mu H}|^{2}$$ |UμH|2 are obtained.
Study of K+→π0e+νγ decay with OKA setup Polyarush, A. Yu; Akimenko, S. A.; Artamonov, A. V. ...
The European physical journal. C, Particles and fields,
02/2021, Volume:
81, Issue:
2
Journal Article
Peer reviewed
Open access
Results of a study of the
K
+
→
π
0
e
+
ν
γ
decay at OKA setup are presented. More than 32,000 events of this decay are observed. The differential spectra over the photon energy and the ...photon–electron opening angle in kaon rest frame are presented. The branching ratios, normalized to that of
K
e
3
decay are calculated for different cuts on
E
γ
∗
and
c
o
s
Θ
e
γ
∗
. In particular, the branching ratio for
E
γ
∗
>
30
MeV and
Θ
e
γ
∗
>
20
∘
is measured R =
B
r
(
K
+
→
π
0
e
+
ν
e
γ
)
B
r
(
K
+
→
π
0
e
+
ν
e
)
= = (0.587±0.010(
stat
.)±0.015(
syst
.))
×
10
-
2
, which is in a good agreement with ChPT
O
(
p
4
)
calculations.
The
T
-odd correlation
, which is the mixed product of the momenta of
,
, and γ in the system of rest of the kaon divided by
, has been measured in the
K
+
→ π
0
e
+
ν
e
γ radiative decay among 101 ...200 candidate events detected at the OKA setup. The asymmetry of the distribution in
is characterized by the ratio
, where
is the number of events with positive (negative) ξ. The value
= (+0.1 ± 3.9(stat.) ± 1.7(syst.)) × 10
–3
or
(90% C.L.) has been obtained.
On the statistics of ~1.7 × 10
8
interactions of positively charged kaons on copper nuclei, coherent events of the
K
+
π
0
system production are selected. The cross sections for the Coulomb and ...coherent strong components and their interference in the region of the
K
*(892) meson are measured. The partial width for the decay
K
*(892) →
K
+
γ is determined. When studying the mass spectrum of the
K
+
π
0
system, an effect which can be interpreted as the interference of the chiral anomaly and the
K
*(892)
s
-channel amplitudes is found. This gives an estimate for the ratio of the observed amplitude of the chiral anomaly to the theoretical one:
A
exp
/
A
th
= 0.9 ± 0.24(stat.) ± 0.3(syst.).
Abstract Results of a study of the $$K^+ \rightarrow \pi ^{0} e^{+} \nu \gamma $$ K + → π 0 e + ν γ decay at OKA setup are presented. More than 32,000 events of this decay are observed. The ...differential spectra over the photon energy and the photon–electron opening angle in kaon rest frame are presented. The branching ratios, normalized to that of $$K_{e3}$$ K e 3 decay are calculated for different cuts on $$E^*_\gamma $$ E γ ∗ and $$cos\Theta ^{*}_{e\gamma }$$ c o s Θ e γ ∗ . In particular, the branching ratio for $$E^{*}_{\gamma }>30$$ E γ ∗ > 30 MeV and $$\Theta ^{*}_{e \gamma }>20^{\circ }$$ Θ e γ ∗ > 20 ∘ is measured R = $$\frac{Br(K^+ \rightarrow \pi ^{0} e^{+} \nu _{e} \gamma ) }{Br(K^+ \rightarrow \pi ^{0} e^{+} \nu _{e})} $$ B r ( K + → π 0 e + ν e γ ) B r ( K + → π 0 e + ν e ) = = (0.587±0.010(stat.)±0.015(syst.)) $$\times 10^{-2}$$ × 10 - 2 , which is in a good agreement with ChPT $$O(p^{4})$$ O ( p 4 ) calculations.
Abstract A precise measurement of the vector and axial-vector form factors difference $$F_V-F_A$$ FV-FA in the $$K^+\rightarrow {\mu ^+}{\nu _{\mu }}{\gamma }$$ K+→μ+νμγ decay is presented. About 95K ...events of $$K^+\rightarrow {\mu ^+}{\nu _{\mu }}{\gamma }$$ K+→μ+νμγ are selected in the OKA experiment. The result is $$F_V-F_A=0.134\pm 0.021(stat)\pm 0.027(syst)$$ FV-FA=0.134±0.021(stat)±0.027(syst) . Both errors are smaller than in the previous $$F_V-F_A$$ FV-FA measurements.
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