Measurement of the K+ → π+γγ decay Kleimenova, A.; Padolski, S.; Petrov, Y. ...
Physics letters. B,
March 2024, 2024-03-00, 2024-03-01, Letnik:
850
Journal Article
Recenzirano
Odprti dostop
A sample of 3984 candidates of the K+→π+γγ decay, with an estimated background of 291±14 events, was collected by the NA62 experiment at CERN during 2017–2018. In order to describe the observed ...di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be (9.61±0.17)×10−7. The first search for production and prompt decay of an axion-like particle with gluon coupling in the process K+→π+a, a→γγ is also reported.
Measurement of the very rare K+→π+νν¯ decay Cortina Gil, E.; Minucci, E.; Padolski, S. ...
The journal of high energy physics,
15/6, Letnik:
2021, Številka:
6
Journal Article
Recenzirano
Odprti dostop
A
bstract
The NA62 experiment reports the branching ratio measurement
BR
K
+
→
π
+
ν
ν
¯
=
10.6
−
3.4
+
4.0
stat
±
0.9
syst
×
10
−
11
at 68% CL, based on the observation of 20 signal candidates with ...an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016–2018. This provides evidence for the very rare
K
+
→
π
+
ν
ν
¯
decay, observed with a significance of 3.4
σ
. The experiment achieves a single event sensitivity of (0
.
839
±
0
.
054)
×
10
−
11
, corresponding to 10.0 events assuming the Standard Model branching ratio of (8
.
4
±
1
.
0)
×
10
−
11
. This measurement is also used to set limits on BR(
K
+
→ π
+
X
), where
X
is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.
Search for π0 decays to invisible particles Cortina Gil, E.; Minucci, E.; Padolski, S. ...
The journal of high energy physics,
02/2021, Letnik:
2021, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A
bstract
The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 10
9
tagged
π
0
mesons from
K
+
→
π
+
π
0
(
γ
), searching for the decay of the
π
0
to invisible particles. No signal ...is observed in excess of the expected background fluctuations. An upper limit of 4
.
4 × 10
−
9
is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay
K
+
→
π
+
X
, where
X
is a particle escaping detection with mass in the range 0.110–0.155 GeV
/c
2
and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming
X
to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.
A
bstract
The NA62 experiment reports an investigation of the
$$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$
K
+
→
π
+
ν
ν
¯
mode from a sample of
K
+
decays collected in 2017 at the CERN SPS. The ...experiment has achieved a single event sensitivity of (0
.
389
±
0
.
024)
×
10
−
10
, corresponding to 2.2 events assuming the Standard Model branching ratio of (8
.
4
±
1
.
0)
×
10
−
11
. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1
.
78
×
10
−
10
for the
$$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$
K
+
→
π
+
ν
ν
¯
branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of (
$$ {0.48}_{-0.48}^{+0.72} $$
0.48
−
0.48
+
0.72
)
×
10
−
10
, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.
Abstract
We report the results of a search for dark photon in-flight decays to
μ
+
μ
−
pairs at NA62. Dark photons could be produced by dumping protons onto a copper-iron absorber, reach the NA62 ...decay volume more than 80 m downstream of the dump and decay therein. The measurement is based on data collected in 2021 which correspond to 1.4 × 10
17
dumped protons.
The NA62 experiment at the CERN SPS reports the first search for K+→π+νν¯ using the decay-in-flight technique, based on a sample of 1.21×1011K+ decays collected in 2016. The single event sensitivity ...is 3.15×10−10, corresponding to 0.267 Standard Model events. One signal candidate is observed while the expected background is 0.152 events. This leads to an upper limit of 14×10−10 on the K+→π+νν¯ branching ratio at 95% CL.
The NA62 experiment at the CERN SPS reports the first search for K+ → π+ν ν ¯ using the decay-in-flight technique, based on a sample of 1.21 x 1011 K+ decays collected in 2016.
A
bstract
The results of a search for
π
0
decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported. From a total of 4.12 × 10
8
tagged
π
0
mesons, ...no signal is observed. Assuming a kinetic-mixing interaction, limits are set on the dark photon coupling to the ordinary photon as a function of the dark photon mass, improving on previous searches in the mass range 60–110 MeV/
c
2
. The present results are interpreted in terms of an upper limit of the branching ratio of the electro-weak decay
π
0
→
γ
ν
ν
¯
, improving the current limit by more than three orders of magnitude.
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