The NA62 experiment at the CERN SPS provides unique opportunity to study rare and forbidden decays of K+ mesons. Using the data collected in 2017 a search for the lepton number violating decays K+ → ...π−µ+µ+ and K+ → π−e+e+ has been performed. New upper limits on the branching ratio have been obtained: 4.2×10−11 for the muon and 2.2×10−10 for the electron mode (90% confidence level). These results improve the existing limits by factors of 2 and 3 respectively.
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.
The role of the NA62 RICH in the BR(K+→π+νν̄) measurement Volpe, R.; Anzivino, G.; Aisa, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Volume:
952
Journal Article
Peer reviewed
The NA62 experiment aims to measure the BR(K+→π+νν̄) with a 10% precision. One of the main backgrounds comes from the decay K+→μ+ν, therefore a highly powerful pion/muon separation is needed. The ...NA62 RICH, together with the calorimeter system, provides an accurate particle identification which has been essential to obtain the first results of the NA62 K+→π+νν̄ analysis, based on 2016 data. Two different algorithms have been exploited which, used in combination, allowed to get a pion reconstruction and identification efficiency of 75%, with a muon suppression factor of about 500, in the momentum range 15–35 GeV/c.
NA62 RICH performance: measurement and optimization Anzivino, G.; Barbanera, M.; Bizzeti, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Volume:
952
Journal Article
Peer reviewed
Open access
The Ring Imaging Cherenkov detector of the NA62 experiment at CERN SPS was commissioned in 2014, but the optimal performance was achieved in 2016 after the precise mirror alignment with reconstructed ...tracks. The measurement and monitoring of basic performance parameters is discussed: ring radius resolution, ring centre resolution, single hit resolution and mean number of hits per ring. The performance is measured with 2016 data on the positron sample. Different contributions to the resolutions are calculated.
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.).
Status of the NA62 ring imaging Cherenkov detector Cenci, P.; Anzivino, G.; Aisa, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Volume:
952
Journal Article
Peer reviewed
The Ring Imaging Cherenkov detector of the NA62 experiment at the CERN SPS is a key element of particle identification in the NA62 experimental strategy. The detector fulfills different conditions: ...to distinguish pions from muons with a muon rejection factor of O(102) in the NA62 momentum range of operation, between 15 and 35 GeV/c; to measure particle arrival time in the decay region with a precision better than 100 ps; to provide fast signals and reference time to the NA62 trigger system. The main design aspects and functional characteristics, as well as the performance of the detector measured with the data taken in the first NA62 physics runs, will be summarized in this paper.
•The NA62 experiment aims to measure the branching ratio of the K+→π+νν¯ decay.•The NA62 RICH performance fulfills the experiment requirements.•Pion–muon identification is performed with a muon rejection factor of O(102).•Time resolution with precision better than 100 ps is achieved.•The RICH is a key element to select charged particles in the trigger system.
Commissioning and performance of the NA62 RICH detector Anzivino, G.; Aisa, D.; Barbanera, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2017, Volume:
876
Journal Article
Peer reviewed
NA62 is the last generation kaon experiment at CERN SPS aiming to study the decay K+→π+νν¯. The goal of the experiment is to measure the decay branching ratio, O(10−10), with 10% precision collecting ...about 100 K+→π+νν¯ events in three years of data taking and assuming a 10% signal acceptance. The weak signal and the huge background make the experiment very challenging. The NA62 detector must be able to reject background events from decay channels with branching ratios up to 10 orders of magnitude higher than the signal one and with similar experimental signature. In order to achieve the designed goal, good Particle Identification (PID), kinematic rejection and precise timing are required. The key element of the PID in NA62 is the Ring Imaging Cherenkov detector (RICH) to identify pions and muons and to measure the particle arrival time. After a pilot run in 2014, installation and commissioning of the detector were completed in 2015, when also the first physics run took place. Results on the detector performance will be presented together with preliminary results from the 2015 and 2016 physics runs.
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