A plastic scintillator bar with dimensions 300 cm × 2.5 cm × 11 cm was exposed to a focused muon beam to study its light yield and timing characteristics as a function of position and angle of ...incidence. The scintillating light was read out at both ends by photomultiplier tubes whose pulse shapes were recorded by waveform digitizers. Results obtained with the WAVECATCHER and SAMPIC digitizers are analyzed and compared. A discussion of the various factors affecting the timing resolution is presented. Prospects for applications of plastic scintillator technology in large-scale particle physics detectors with timing resolution around 100 ps are provided in light of the results.
A search for heavy neutral lepton (N) production in K+→e+N decays using the data sample collected by the NA62 experiment at CERN in 2017–2018 is reported. Upper limits of the extended neutrino mixing ...matrix element |Ue4|2 are established at the level of 10−9 over most of the accessible heavy neutral lepton mass range 144–462 MeV/c2, with the assumption that the lifetime exceeds 50 ns. These limits improve significantly upon those of previous production and decay searches. The |Ue4|2 range favoured by Big Bang Nucleosynthesis is excluded up to a mass of about 340 MeV/c2.
The NA62 experiment at CERN reports searches for K+→μ+N and K+→μ+νX decays, where N and X are massive invisible particles, using the 2016–2018 data set. The N particle is assumed to be a heavy ...neutral lepton, and the results are expressed as upper limits of O(10−8) of the neutrino mixing parameter |Uμ4|2 for N masses in the range 200–384 MeV/c2 and lifetime exceeding 50 ns. The X particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for X masses in the range 10–370 MeV/c2 are reported for the first time, ranging from O(10−5) to O(10−7). An improved upper limit of 1.0×10−6 is established at 90% CL on the K+→μ+ννν¯ branching fraction.
A search for heavy neutral lepton production in K+ decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the 10−7 to ...10−6 level are established on the elements of the extended neutrino mixing matrix |Ue4|2 and |Uμ4|2 for heavy neutral lepton mass in the ranges 170–448 MeV/c2 and 250–373 MeV/c2, respectively. This improves on the previous limits from HNL production searches over the whole mass range considered for |Ue4|2, and above 300 MeV/c2 for |Uμ4|2.
Present study reports the cultivation of potato seedlings on ionite substrates in pot culture. The possibility of using these substrates to preserve the qualitative characteristics of the potato ...genotype was studied. The research was conducted on hybrid seed potatoes produced in VNIIKH named after A. G. Lorch. During the growing season, the intensity of seedlings development in terms of stem height (every 2 weeks) was taken into account. At the end of the growing season, the number of leaves was analyzed, and after harvesting, the yield and its contributing components were taken into account. Dispersion analysis was performed to study the quantitative assessment of phenotypic factors. In peat soil, depending on their origin and year of cultivation, the percentage of seedling death varied from 26.0 to 41.6%. On ionite substrates, the survival rate of seedlings significantly increased - only 4.0-14.4% died when grown in cuvettes. After picking in pots, the full survival of seedlings was observed both in the control and in the experimental variants. The best of the experimental options for growing seedlings in pot culture was the substrate IS-2E, prepared on the basis of IS-2V and clinoptilolite in a volume ratio of 3:1. Growth and survival rate of seedlings on ionite substrates significantly increased by 19.3-30.2% over control and thus reduces percentage of seedlings elimination. Growing seedlings is one of the first and most important stages in the general scheme of potato breeding 1,2. The pot culture of seedlings in greenhouses, which provides separate cultivation of genotypes, high planting density and the ability to eliminate the seasonality of this process, has acquired great importance 3. However, the mixtures used as a substrate for growing plants do not provide optimal conditions for the growth and development of seedlings and the preservation of all genotypes 4,5. Identifying optimal substrates and methods for obtaining hybrid seedlings of potatoes and improving the efficiency of selecting high-yielding genotypes at an early stage of selection is considered as an important researchable issue to increase the effectiveness of the entire selection process 6,7. All this leads to strengthen the research in this direction, which has not yet developed and reported 8.
Studies had been carried out to study the possibility of using ionite substrates for growing potato seedlings in tube culture, to analyze the variability of hybrid potato populations by ...morphobiological and economically valuable characteristics depending on the substrate, to analyze the effectiveness of the selection of high-yielding forms at the early stage of the breeding process. The experiment included 7 different modifications of the nutrient medium composition. Seed germination, seedling survival rate, tuber formation rate, percentage of tuber-forming seedlings, number of tubers per seedling, size, and shape of tubers were taken into account. Quantitative assessment of factors in phenotypic manifestation of signs was carried out by the method of dispersion analysis. Sterile microtubers were stored at 2-4°C in the dark before planting. As a result of the research, a different tuber-forming ability was found in seedlings of populations of different variants. The tube culture of seedlings ensures full survival of seedlings. For the growth and development of seedlings in a tube culture, the best of those studied was the nutrient medium based on the ion-exchange substrate IS-2V, containing 1% sucrose and 500 mg / 1 CCC. Two-stage cultivation of seedlings (the initial increase in the above-ground mass, then the induction of tuberization) had a positive effect on the pace and quality of tuberization. 30-40 days after induction, tuberization was observed in 90-100% of seedlings, regardless of their origin, and the size of microtubers was on average 6.7-8.7 mm.
The NA62 experiment at CERN reports a search for the lepton number violating decays K+→π−e+e+ and K+→π−μ+μ+ using a data sample collected in 2017. No signals are observed, and upper limits on the ...branching fractions of these decays of 2.2×10−10 and 4.2×10−11 are obtained, respectively, at 90% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively.
A measurement of the K+→ π+μ+μ− decay Cortina Gil, E.; Kleimenova, A.; Minucci, E. ...
The journal of high energy physics,
11/2022, Letnik:
2022, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
A sample of 2
.
8 × 10
4
K
+
→
π
+
μ
+
μ
−
candidates with negligible background was collected by the NA62 experiment at the CERN SPS in 2017–2018. The model-independent branching fraction ...is measured to be (9
.
15 ± 0
.
08) × 10
−
8
, a factor three more precise than previous measurements. The decay form factor is presented as a function of the squared dimuon mass. A measurement of the form factor parameters and their uncertainties is performed using a description based on Chiral Perturbation Theory at
O
(
p
6
).
A
bstract
The NA62 experiment at CERN, designed to study the ultra-rare decay
K
+
→
π
+
ν
ν
¯
, has also collected data in beam-dump mode. In this configuration, dark photons may be produced by ...protons dumped on an absorber and reach a decay volume beginning 80 m downstream. A search for dark photons decaying in flight to
μ
+
μ
−
pairs is reported, based on a sample of 1
.
4 × 10
17
protons on dump collected in 2021. No evidence for a dark photon signal is observed. A region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon masses between 215 and 550 MeV
/c
2
.
The first search for ultra-rare K+ decays into the π+e+e−e+e− final state is reported, using a dataset collected by the NA62 experiment at CERN in 2017–2018. An upper limit of 1.4×10−8 at 90% CL is ...obtained for the branching ratio of the K+→π+e+e−e+e− decay, predicted in the Standard Model to be (7.2±0.7)×10−11. Upper limits at 90% CL are obtained at the level of 10−9 for the branching ratios of two prompt decay chains involving pair-production of hidden-sector mediators: K+→π+aa, a→e+e− and K+→π+S, S→A′A′, A′→e+e−.
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