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Precise test of lepton flavour universality in Formula omitted-boson decays into muons and electrons in Formula omitted collisions at Formula omitted with the ATLAS detector
The ratio of branching ratios of the W boson to muons and electrons, [Formula omitted]/ [Formula omitted], has been measured using [Formula omitted] of pp collision data at [Formula omitted] [Formula omitted] collected with the ATLAS detector at the LHC, probing the universality of lepton couplings. The ratio is obtained from measurements of the [Formula omitted] production cross-section in the ee, [Formula omitted] and [Formula omitted] dilepton final states. To reduce systematic uncertainties, it is normalised by the square root of the corresponding ratio [Formula omitted] for the Z boson measured in inclusive [Formula omitted] and [Formula omitted] events. By using the precise value of [Formula omitted] determined from [Formula omitted] colliders, the ratio [Formula omitted] is determined to be RW/e=0.9995±0.0022(stat)±0.0036(syst)±0.0014(ext).The three uncertainties correspond to data statistics, experimental systematics and the external measurement of [Formula omitted], giving a total uncertainty of 0.0045, and confirming the Standard Model assumption of lepton flavour universality in W-boson decays at the 0.5% level.
Journal Article
Possible evidence for the production of ArFormula omitted metastable negative molecular ions in gaseous argon of two-phase detectors for dark matter searches
Our recent studies of electroluminescence (EL) properties in two-phase argon detectors for dark matter searches have revealed the presence of unusual delayed pulses in the EL signal in the form of two slow components with time constants of about 5 and 50 [Formula omitted]. These components were shown to be present in the charge signal itself, which clearly indicates that drifting electrons are temporarily trapped on two states of metastable negative argon ions which have never been observed before. In this work, using the pressure dependence of the ratio of slow component contributions measured in experiment, it is deduced that these states are those of two types of metastable negative molecular ions, [Formula omitted] and [Formula omitted] for the higher and lower energy level respectively.
Journal Article
Azimuthal correlations of heavy-flavor hadron decay electrons with charged particles in pp and p-Pb collisions at Formula omitted = 5.02 TeV
The azimuthal ( [Formula omitted]) correlation distributions between heavy-flavor decay electrons and associated charged particles are measured in pp and p-Pb collisions at [Formula omitted] TeV. Results are reported for electrons with transverse momentum [Formula omitted] [Formula omitted] and pseudorapidity [Formula omitted]. The associated charged particles are selected with transverse momentum [Formula omitted] [Formula omitted], and relative pseudorapidity separation with the leading electron [Formula omitted]. The correlation measurements are performed to study and characterize the fragmentation and hadronization of heavy quarks. The correlation structures are fitted with a constant and two von Mises functions to obtain the baseline and the near- and away-side peaks, respectively. The results from p-Pb collisions are compared with those from pp collisions to study the effects of cold nuclear matter. In the measured trigger electron and associated particle kinematic regions, the two collision systems give consistent results. The [Formula omitted] distribution and the peak observables in pp and p-Pb collisions are compared with calculations from various Monte Carlo event generators.
Journal Article
ZnPSe 3 as ultrabright indirect band-gap system with microsecond excitonic lifetimes
ZnPSe 3 was identified as a two-dimensional material wherein valley and spin can be optically controlled in technologically relevant timescales. We report an optical characterization of ZnPSe 3 crystals that show indirect band-gap characteristics in combination with unusually strong photoluminescence. We found evidence of interband recombination from photoexcited electron–hole states with lifetimes in a microsecond timescale. Through a comparative analysis of photoluminescence and photoluminescence excitation spectra, we reconstructed the electronic band scheme relevant to fundamental processes of light absorption, carrier relaxation, and radiative recombination through interband pathways and annihilation of defect-bound excitons. The investigation of the radiative processes in the presence of a magnetic field revealed spin splitting of electronic states contributing to the ground excitonic states. Consequently, the magnetic field induces an imbalance in the number of excitons with the opposite angular momentum according to the thermal equilibrium as seen in the photoluminescence decay profiles resolved by circular polarization.
Journal Article
Multiple mobile excitons manifested as sidebands in quasi-one-dimensional metallic TaSe 3
Charge neutrality and their expected itinerant nature makes excitons potential transmitters of information. However, exciton mobility remains inaccessible to traditional optical experiments that only create and detect excitons with negligible momentum. Here, using angle-resolved photoemission spectroscopy, we detect dispersing excitons in the quasi-one-dimensional metallic trichalcogenide, TaSe
. The low density of conduction electrons and the low dimensionality in TaSe
combined with a polaronic renormalization of the conduction band and the poorly screened interaction between these polarons and photo-induced valence holes leads to various excitonic bound states that we interpret as intrachain and interchain excitons, and possibly trions. The thresholds for the formation of a photo-hole together with an exciton appear as side valence bands with dispersions nearly parallel to the main valence band, but shifted to lower excitation energies. The energy separation between side and main valence bands can be controlled by surface doping, enabling the tuning of certain exciton properties.
Journal Article
ELECTRON PARAMAGNETIC RESONANCE OF MnIn.sub.2S.sub.4 SINGLE CRYSTALS
Electron paramagnetic resonance (EPR) spectra of Mn[In.sub.2][S.sub.4] single crystals were studied at different temperatures. The EPR lines were found to have a Lorentz shape. A strong increase in the width of the resonance line AH and a shift in the g-factor occur in the paramagnetic phase with a temperature decrease in the region of 60-6.8 K. This shift is proportional to the line width: Ag(T) ~ AAH(T). The relaxation time is ~[10.sup.-10] s and increases with increasing temperature.
Journal Article
Convergence of Plasmon and Electron Transition Energies in Crystal Bi.sub.0.6Sb.sub.1.4Te.sub.3
The temperature dependences of the reflection coefficient spectra in the range of effects caused by the resonant behavior of the plasma of free charge carriers of the Bi.sub.0.6Sb.sub.1.4Te.sub.3 crystal, in the temperature dependences of the magnetic susceptibility of which features are observed, are investigated. A change in the shape of the plasma edge and the resulting splitting of the peak of the energy loss function were detected, which allows us to conclude that an electron-plasmon interaction affecting the state of the electronic system has been observed.
Journal Article
Localized pi-Electron States in the Optical Absorption Spectrum of Tetrahedrally Coordinated Amorphous Carbon
The paper presents result of ab initio methods exploiting to calculate the molar extinction spectrum of some model clusters, the molecular hybrid C.sub.24H.sub.30 included. Based on the comparison of the calculation with the experimental spectra of the main allotropic modifications of carbon, the absorption maximum with an energy of ~6 eV in the absorption spectrum of highly tetrahedral amorphous carbon (ta-C) attributed to the [pi] [right arrow] [pi]* optical transitions of electrons in a single aromatic ring. The edge sites of the ring covalently bonded with the sp.sup.3-hybridised carbon atoms of the amorphous matrix. The manifestation of a shoulder in the spectrum of the imaginary part of the refractive index of a film of highly tetrahedral amorphous carbon (ta-C), 4.6 eV, is assigned to [pi] [right arrow] [pi]* optical transitions of clusters distorted with hybrid Stone-Wallace-like defect, also covalently bonded with the amorphous matrix.
Journal Article
Preliminary Exploration of Low Frequency Low-Pressure Capacitively Coupled Ar-Osub.2 Plasma
Non-thermal plasma as an emergent technology has received considerable attention for its wide range of applications in agriculture, material synthesis, and the biomedical field due to its low cost and portability. It has promising antimicrobial properties, making it a powerful tool for bacterial decontamination. However, traditional techniques for producing non-thermal plasma frequently rely on radiofrequency (RF) devices, despite their effectiveness, are intricate and expensive. This study focuses on generating Ar-O[sub.2] capacitively coupled plasma under vacuum conditions, utilizing a low-frequency alternating current (AC) power supply, to evaluate the system’s antimicrobial efficacy. A single Langmuir probe diagnostic was used to assess the key plasma parameters such as electron density (ne), electron temperature (Te), and electron energy distribution function (EEDF). Experimental results showed that n[sub.e] increases (7 × 10[sup.15] m[sup.−3] to 1.5 × 10[sup.16] m[sup.−3]) with a rise in pressure and AC power. Similarly, the EEDF modified into a bi-Maxwellian distribution with an increase in AC power, showing a higher population of low-energy electrons at higher power. Finally, the generated plasma was tested for antimicrobial treatment of Xanthomonas campestris pv. Vesicatoria. It is noted that the plasma generated by the AC power supply, at a pressure of 0.5 mbar and power of 400 W for 180 s, has 75% killing efficiency. This promising result highlights the capability of the suggested approach, which may be a budget-friendly and effective technique for eliminating microbes with promising applications in agriculture, biomedicine, and food processing.
Journal Article