Search

Abstract 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 × 1011 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 ′ $$ {m}_{Z^{\prime }} $$ ≲ 2 MeV range, in complementarity with the limits recently obtained by the NA64-μ experiment with a muon beam.

Abstract We report the results of a search for a new vector boson ( $$ A'$$ A ′ ) decaying into two dark matter particles $$\chi _1 \chi _2$$ χ 1 χ 2 of different mass. The heavier $$\chi _2$$ χ 2 particle subsequently decays to $$\chi _1$$ χ 1 and an off-shell Dark Photon $$ A'^* \rightarrow e^+e^-$$ 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 $$A'\rightarrow \chi \overline{\chi }$$ A ′ → χ χ ¯ and axion-like or pseudo-scalar particles $$a \rightarrow \gamma \gamma $$ a → γ γ . 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 $$A'$$ A ′ masses from 2 $$m_e$$ m e up to 390 MeV and mixing parameter $$\varepsilon $$ ε between $$3\times 10^{-5}$$ 3 × 10 - 5 and $$2\times 10^{-2}$$ 2 × 10 - 2 .

Abstract Recently, the ATOMKI experiment has reported new evidence for the excess of $$e^+e^-$$ e + e - events with a mass $$\sim $$ ∼ 17 MeV in the nuclear transitions of $$^4$$ 4 He, that they previously observed in measurements with $$^8$$ 8 Be. These observations could be explained by the existence of a new vector $$X17$$ X 17 boson. So far, the search for the decay $$X17 \rightarrow e^+ e^-$$ X 17 → e + e - with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining $$X17$$ X 17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the $$X17$$ X 17 decay with the proposed method. To reach this goal an optimization of the $$X17$$ X 17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [1], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate show that the goal of the proposed search is feasible.

This paper aims to introduce the concept and objectives of a recently supported European project entitled “Geomatics and Civil Engineering Innovative Research on Heritage”, in short ENGINEER. The ENGINEER project visions to enhance and extend inter-departmental multidisciplinary research activities of the Department of Civil Engineering & Geomatics of the Cyprus University of Technology through coordination and support actions as well as through targeted research activities with the support of European leading institutions. Project tasks aim to fill research multidisciplinary gaps, push, and extend knowledge into new and innovative fields dealing with the monitoring, digitization, visualization, and preservation of ancient monuments and cultural heritage sites, assisting their protection, promotion, and safeguarding.

The intentional damages to local Cultural Heritage sites carried out in recent months by the Islamic State (IS) have received wide coverage from the media worldwide. Earth Observation data is an important tool to assess these damages in such non-accessible areas: If a fast response is desired, automated image processing techniques would be needed to speed up the analysis. This paper shows the first results of applying fast and robust change detection techniques to sensitive areas. A map highlighting potentially damaged buildings is derived, which could help experts at timely assessing the damages to the Cultural Heritage sites in the observed images.

We report the results of a search for a new vector boson ( A ' ) decaying into two dark matter particles χ 1 χ 2 of different mass. The heavier χ 2 particle subsequently decays to χ 1 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 ' → χ χ ¯ and axion-like or pseudo-scalar particles a → γ γ . 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 2 m e up to 390 MeV and mixing parameter ε between 3 × 10 - 5 and 2 × 10 - 2 ., (© The Author(s) 2021.)

Recently, the ATOMKI experiment has reported new evidence for the excess of e + e - events with a mass ∼ 17 MeV in the nuclear transitions of 4 He, that they previously observed in measurements with 8 Be. These observations could be explained by the existence of a new vector X 17 boson. So far, the search for the decay X 17 → e + e - with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining X 17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the X 17 decay with the proposed method. To reach this goal an optimization of the X 17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [1], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate show that the goal of the proposed search is feasible., (© The Author(s) 2020.)