A study of the K + → π 0 e + νγ decay The NA62 collaboration; A. Kleimenova; S. Padolski ...
The journal of high energy physics,
09/2023, Letnik:
2023, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Abstract A sample of 1.3 × 105 K + → π 0 e + νγ candidates with less than 1% background was collected by the NA62 experiment at the CERN SPS in 2017–2018. Branching fraction measurements are obtained ...at percent relative precision in three restricted kinematic regions, improving on existing results by a factor larger than two. An asymmetry, possibly related to T-violation, is investigated with no evidence observed within the achieved precision.
Abstract 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 $$ \mathrm{BR}\left({K}^{+}\to {\pi}^{+}\nu ...\overline{\nu}\right)=\left({10.6}_{-3.4}^{+4.0}\left|{}_{\mathrm{stat}}\right.\pm {0.9}_{\mathrm{syst}}\right)\times {10}^{-11} $$ 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 ¯ $$ {\pi}^{+}\nu \overline{\nu} $$ decay, observed with a significance of 3.4σ. 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.
The K+→π+νν‾ decay is theoretically one of the cleanest meson decays and so a good place to look for indirect effects of new physics complementary to LHC searches. The NA62 experiment at CERN is ...designed to measure the branching ratio of this decay with 10% precision. NA62 was commissioned in October 2014, took data in pilot runs in 2014 and 2015. The NA62 experimental setup is illustrated and data quality is reported.
Status of the NA62 Experiment Piccini, M.
EPJ Web of Conferences,
2020, Letnik:
234
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The decay $ {K^ + } \to {\pi ^ + }v\bar v $, with a very precisely predicted branching ratio of less than 10
−10
in the Standard Model framework, is one of the best candidates to reveal indirect ...effects of new physics at the highest mass scales. The NA62 experiment at CERN SPS is designed to measure the branching ratio of such decay with a decay-in-flight technique, novel for this channel. The main goal of NA62 is to measure such Branching Ratio of $ {K^ + } \to {\pi ^ + }v\bar v $ with an accuracy better than 20%. This will be achieved by collecting up to 100 $ {K^ + } \to {\pi ^ + }v\bar v $ events with a background contamination at the level of 10%. The NA62 detector was commissioned in 2014 and 2015 and the experiment took physics data from 2015 to 2018. NA62 has already published the result of the 2016 data analysis. The 2017 data analysis is in progress, the single event sensitivity reached and the evaluation of the main backgrounds will be shown in this contribution.
A
bstract
The NA62 experiment reports an investigation of the
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
+
→
π
+
ν
ν
¯
branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of (
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 The NA62 experiment reports an investigation of the K + → π + ν ν ¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ 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 + → π + ν ν ¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ 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.
Search for K+→π+νν‾ at NA62 Aglieri Rinella, G.; Angelucci, B.; Antonelli, A. ...
Nuclear and particle physics proceedings,
January-March 2017, Letnik:
282-284
Journal Article
Recenzirano
Among the meson decays, K→πνν‾ are the cleanest environment, from the theoretical point of view, where to search for new physics effects. The NA62 Experiment at CERN SPS aims to measure the ...BR(K+→π+νν‾) with a 10% precision by the end of 2018. It has been commissioned with technical runs in 2014 and 2015, and some preliminary results of the detector performances and quality of data are here reported.
In 2007 the NA62 experiment at CERN collected a large sample of charged kaon decays with a highly efficient trigger selecting events with electrons in the final state. The kaon beam represents a rich ...source of tagged neutral pion decays in vacuum. The electromagnetic transition form factor slope of the π0 in the time-like region has been measured from about 106 fully reconstructed π0 Dalitz decays collected in 2007. The preliminary result a = (3.68 ± 0.51stat ± 0.25syst) × 10-2 is the most precise to date. This value is compatible with theoretical expectations and consistent with the previous measurements.
The RICH detector of the NA62 experiment is one of the key detectors to achieve the muon rejection needed in the search for the {K^ + } \to {\pi ^ + }\nu \bar \nu decay, performed by NA62. Since ...BR({K^ + } \to {\mu ^ + }\nu ) is higher than BR({K^ + } \to {\pi ^ + }\nu \bar \nu ) by more than 9 orders of magnitude, it represents one of the most relevant background contributions. Its rejection is performed with kinematic reconstruction of the event and identification of the charged particles in the final state (pions against muons). The Ring Imaging Cherenkov detector (RICH) gives a muon rejection higher than a factor 100 in the momentum range 15-35 GeV/c, and measures the track crossing time with a resolution better than 100 ps. It is also exploited to provide trigger for charged particles. In this contribution the RICH detector will be described, together with its basic performance, the mirrors alignment procedure and its usage in {K^ + } \to {\pi ^ + }\nu \bar \nu search.
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