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A bstract The inclusion of an additional U(1) gauge L μ − L τ symmetry would release the tension between the measured and the predicted value of the anomalous muon magnetic moment: this paradigm assumes the existence of a new, light Z ′ vector boson, with dominant coupling to μ and τ leptons and interacting with electrons via a loop mechanism. The L μ − L τ model can also explain the Dark Matter relic abundance, by assuming that the Z ′ boson acts as a “portal” to a new Dark Sector of particles in Nature, not charged under known interactions. In this work we present the results of the Z ′ search performed by the NA64- e experiment at CERN SPS, that collected ~ 9 × 10 11 100 GeV electrons impinging on an active thick target. Despite the suppressed Z ′ production yield with an electron beam, NA64- e provides the first accelerator-based results excluding the g − 2 preferred band of the Z ′ parameter space in the 1 keV < m Z ′ ≲ 2 MeV range, in complementarity with the limits recently obtained by the NA64- μ experiment with a muon beam.

Development of materials possessing the ability to recover their main function(s) in response to destructive impacts is, today, one of most rapidly growing fields in material science. In particular, protective organic coatings with the features to heal or restore their protective function autonomously are of great interest in fighting surface deterioration processes like corrosion, biofouling, and other affecting metallic structures. Embedding of micro- and nanocontainers in protective coatings is a frequently used technique nowadays to provide them one or several feedback-active functionalities. Depending on the container's morphology and active agent(s) filled, coatings with specifically aimed self-recovering functionalities (anticorrosive, water-repelling, antifouling, etc.) or multifunctional coatings can be created. In the present paper, different types of containers for self-recovering functional coatings synthesized by use of mesoporous nano- and microparticles or on the emulsion basis are presented. L-b-L polyelectrolyte deposition, interfacial polymerization, surface precipitation, Pickering emulsions, and in situ emulsion polymerization were utilized for the preparation of nano- or micro-scaled containers. Morphology of containers, efficiency of encapsulation, and kinetics of active agents release were investigated using modern techniques such as transmission mode in the scanning electron microscopy (T-SEM), cryo scanning electron microscopy (Cryo-SEM), etc. Incorporation of containers in the coating matrix was followed by the experimental modeling of external impacts, leading to simultaneous container damage. Subsequent release of the active agent at the affected site caused the active feedback of the coating and self-recovery of its specific protective function. The advantages of novel container-based protective coatings as compared to conventional ones are illustrated by corrosion tests results according to ASTM Standard B117.

Recent research on phase change materials promising to reduce energy losses in industrial and domestic heating/air-conditioning systems is reviewed. In particular, the challenges q fphase change material applications such as an encapsulation strategy for active ingredients, the stability of the obtained phase change materials, and emerging corrosion complications are discussed. Moreover, phase change materials could be employed in refrigerators to increase the efficiency and in storage facilities to reduce evaporative losses of fuels and industrial liquid products. Promising areas for using these materials are highlighted. Ways of solving possible problems are outlined.

We plan to develop an advanced Transition Radiation Detector (TRD) for hadron identification in the TeV momentum range, based on the simultaneous measurement of the energies and of the emission angles of the Transition Radiation (TR) X-rays with respect to the radiating particles. To study the feasibility of this project, we have carried out a beam test campaign at the CERN SPS facility with 20 GeV/c electrons and muons up to 300 GeV/c. To detect the TR X-rays and the radiating particles, we used a 300 μm thick double-sided silicon strip detector, with a strip readout pitch of 50 μm. A 2 m long helium pipe was placed between the radiators and the detector, in order to ensure adequate separation between the TR X-rays and the radiating particle on the detector plane and to limit the X-ray absorption before the detector. We measured the double-differential (in energy and angle) spectra of the TR emitted by several radiators. The results are in good agreement with the predictions obtained from the TR theory.

AbstractWorks devoted to studying the effect of active environments on damageability of surfaces of solid bodies and materials upon contact actions (Rehbinder effect) have been briefly reviewed. A novel procedure, which combines microscratching and electrochemical reduction of an active component on a studied material surface, has been described. This procedure enables one to simulate and study the liquid-metal embrittlement of the material in the absence of a liquid metal phase on its surface.

The ATLAS experiment at the Large Hadron Collider has an ambitious program of the detector upgrade to meet an expected rise of accelerator luminosity. The first large system which supposed to be installed in 2019 is the New Small Wheel (NSW) for ATLAS muon spectrometer. In order to ensure high quality and reliability of NSW chambers an X-ray scanning technique is being developed. One of the main components of the X-ray scanner is a special software visualization tool which would allow a fast and clear representation of scanning results and an identification of possible chamber defects.

The innermost station of the ATLAS muon end-cap system will be replaced during the forthcoming Phase-I upgrade of the ATLAS detector. The small-strip Thin Gap Chambers (sTGC) are supposed to operate at harsh radiation conditions of super LHC. X-ray scanning technique for production quality control is proposed to ensure long-term reliability of these chambers. It allows to reveal different types of technological defects critical for sTGC chambers operation.

sTGC chambers are designed to operate at super-LHC conditions and will be installed in place during Phase-I upgrade of the ATLAS muon spectrometer. These chambers will provide precise coordinate measurements of the charged particle tracks and level 1 trigger for high pT muons. It is critical for the ATLAS detector to ensure a robust operation of these chambers during entire sLHC period. A quality control procedure based on X-ray scanner is being developed. Choice of the active gas for these tests is a very important issue. On one hand it should allow to find different types of chamber production defects, on the other hand one has to be sure that found problems are essential for the detector operation in future. Studies of the operation of the sTGC chamber prototype under X-ray irradiation with two gas mixtures (n- pentane/CO2 and CO2) were performed. The prototype was irradiated by X-rays with energy up to 50 keV. Particular attention was paid to the study of the \"hot\" chamber regions.

This review considers the regularities of manifestations of the Rebinder effect in surface damageability. The general physico-chemical fundamentals of such surface phenomena (predominantly, in contact interactions) are stated, and examples of versatility and specifics of their manifestations in nature and technology are given for minerals, ionic structures, metals, and catalysts.

We report the results of a search for a new vector boson (A′) decaying into two dark matter particles χ1χ2 of different mass. The heavier χ2 particle subsequently decays to χ1 and an off-shell Dark Photon A′∗→e+e-. For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay A′→χχ¯ and axion-like or pseudo-scalar particles a→γγ. With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for A′ masses from 2me up to 390 MeV and mixing parameter ε between 3×10-5 and 2×10-2.