A precision measurement of the ratio RK of the rates of kaon leptonic decays K±→e±ν and K±→μ±ν with the full data sample collected by the NA62 experiment at CERN in 2007–2008 is reported. The result, ...obtained by analysing ∼150000 reconstructed K±→e±ν candidates with 11% background contamination, is RK=(2.488±0.010)×10−5, in agreement with the Standard Model expectation.
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.
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.
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.
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.
We report results from a new measurement of the K
e4
decay K
±
→π
+
π
-
e
±
ν by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670 000 K
e4
decays in both charged ...modes collected in 2003. The form factors of the hadronic current (F,G,H) and ππ phase difference (δ=δ
s
-δ
p
) have been measured in ten independent bins of the ππ mass spectrum to investigate their variation. A sizeable acceptance at large ππ mass, a low background and a very good resolution contribute to an improved experimental accuracy, a factor two better than in the previous measurement, when extracting the ππ scattering lengths a
0
0
and a
0
2
. Under the assumption of isospin symmetry and using numerical solutions of the Roy equations, the following values are obtained in the plane (a
0
0
,a
0
2
): a
0
0
=0.233±0.016stat±0.007syst,a
0
2
=-0.0471±0.011stat±0.004syst. The presence of potentially large isospin effects is also considered and will allow comparison with precise predictions from Chiral Perturbation Theory.
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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