Propagation of whistler-mode waves in magnetized plasma in the presence of small-scale field-aligned irregularities with enhanced or depressed plasma density is simulated numerically. The numerical ...experiments have demonstrated the effect of guided propagation of whistler-mode waves in plasma regions occupied by irregularities with transverse dimensions smaller than the whistler wavelength in uniform plasma. It is shown that not only individual irregularities but also the entire modified region, which serves as a specific guiding structure, exhibit waveguide properties.
Parameters of pulsed electric discharges arising between insulated metal parts of helicopter rotor blades, which generate electromagnetic interferences for onboard radio stations operating in the ...very short wave (VSW) and ultrashort wave (USW) bands have been studied. These discharges appear as a result of the in-flight engine-driven differential charging of helicopters. In-flight and laboratory experiments were used to determine the range of discharge voltages and currents and the amplitude and spectral characteristic of electromagnetic interferences produced by these discharges for onboard antennas.
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
).
Krot device is a unique installation of the scientific infrastructure of the Russian Federation. It is a source of highly uniform low-temperature plasma that takes up to several tens of cubic meters. ...The setup makes it possible to perform both scaling laboratory simulations of ionospheric and magnetospheric phenomena in the approximation of unbound plasma, as well as plasma tests of full-size samples of the onboard equipment of spacecraft (SC). The simulation results of the dynamics and interaction of small-scale thermal plasma irregularities occurring during ionospheric heating experiments are presented. The impedance of the small-size models of RESONANCE and STRANNIK SC electric antennas in plasma is measured. The possible use of free-space calibration of antennas in the magnetospheric portions of the orbit in the ELF and VLF ranges is confirmed. The efficiency of a new plasma parameters resonance sensor for the TRABANT SC in the ionospheric range of electron densities is shown.
—
A compact pulsed plasma generator of simple design made of a coaxial cable with polyethylene insulation has been described. A plasma gun generates a cloud of carbon-hydrogen plasma with an electron ...density of more than 10
13
cm
–3
, including in a magnetic field produced of up to 500 G and also in the presence of the background plasma with a density of about 10
12
cm
–3
, which is produced by an independent source. The high resource of the gun and stability of plasma parameters from one pulse to another allows using such a gun in laboratory experiments simulating dynamic processes in space.
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
.
Abstract The $$K^{+} \rightarrow \pi ^{+}\pi ^{0}\pi ^{0}\gamma $$ K + → π + π 0 π 0 γ decay is observed by the OKA collaboration. About 60 events of the decay observed with signal:noise $$\approx ...1$$ ≈ 1 . The branching ratio obtained by normalization to $$K^{+} \rightarrow \pi ^{+}\pi ^{0}\pi ^{0}$$ K + → π + π 0 π 0 is measured to be $$(3.7 \pm 0.9(stat) \pm 0.3(syst))\times 10^{-6}$$ ( 3.7 ± 0.9 ( s t a t ) ± 0.3 ( s y s t ) ) × 10 - 6 for $$E_{\gamma }^*>10\,\textrm{MeV}$$ E γ ∗ > 10 MeV . The branching ratio, $$\gamma $$ γ energy spectrum and angular distribution are consistent with ChPT prediction.
Details of application of Si avalanche photodiode read-out for scintillator pad detector are discussed. The detection of charged particles using scintillator pads read-out with embedded WLS fiber is ...explored in many HEP experiments. The 12
cm×12
cm and 4
cm×4
cm scintillator counter design developed for LHC-b experiment LHC-b Calorimeters Technical Design Report, CERN/LHCC/, 2000-0036 is being explored for the “OKA” experiment (Protvino) V.F. Obraztsov, OKA: the experimental program with RF-separated K+-beam, KAON-05, Evanston, 2005, 〈
http://www.oka.ihep.su〉 aimed to K-meson rare decays study. Recently developed multi-pixel avalanche photodiodes operating in Geiger mode have definitive advantages with respect to conventional multi-anode PMT, i.e. larger quantum efficiency, compact detector design and small light losses, lower supply voltage. All this allows one to achieve a high light response of more than 100 photo-electrons per MIP with a simple and economical detector design.
In this paper we describe characteristics of 3 batches of MRS APD, produced by the CPTA, Moscow Center of Perspective Technologies and Apparatus (CPTA), Moscow; Photonique SA, Geneva 〈
http://www.photonique.ch〉. We tested 3 types of photodiodes with a sensitive area of 1
mm
2 with 556 pixels, defining the noise counting rate and detection efficiency as a function of electronics threshold.
Abstract A high-statistics data sample of the $$K^{+}$$ K + decays is recorded by the OKA collaboration. A missing mass analysis is performed to search for a light invisible pseudoscalar axion-like ...particle (ALP) a in the decay $$K^{+} \rightarrow \pi ^{+} \pi ^{0} a$$ K + → π + π 0 a . No signal is observed, and the upper limits for the branching ratio of the decay are calculated. The $$90\%$$ 90 % confidence level upper limit changes from $$2.5\cdot 10^{-6}$$ 2.5 · 10 - 6 to $$2\cdot 10^{-7}$$ 2 · 10 - 7 for the ALP mass from 0 to 200 MeV/ $$c^{2}$$ c 2 , except for the region of $$\pi ^{0}$$ π 0 mass, where the upper limit is $$4.4\cdot 10^{-6}$$ 4.4 · 10 - 6 .
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