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NA64 Papers

$X_{17}$ anomaly and prospects for its verification with NA64 experiment / Molina Bueno, Laura (Zurich, ETH) /NA64 Collaboration
The ATOMKI collaboration reported a 7$\sigma$ excess in the angular distribution of $e^{+}e^{-}$ events in the nuclear de-excitation of $^8$Be, which was recently confirmed by new results on other nuclei, $^4$He. This anomaly could be explained by the existence of a new boson $X_{17}$ with a mass around 17 MeV and spin 0 or 1. [...]
SISSA, 2021 - 6 p. - Published in : PoS LHCP2020 (2021) 177 Fulltext: PDF;
In : 8th Conference of Large Hadron Collider Physics (LHCP), Online, 25 - 30 May 2020, pp.177

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Search for pseudoscalar bosons decaying into $e^+e^-$ pairs / NA64 Collaboration
We report the results of a search for a light pseudoscalar particle $a$ that couples to electrons and decays to $e^+e^-$ performed using the high-energy CERN SPS H4 electron beam. [...]
- 6 p.

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Search for pseudoscalar bosons decaying into e+e- pairs / Banerjee, D ; Bernhard, J ; Burtsev, V ; Chumakov, A ; Cooke, D ; Crivelli, P ; Depero, E ; Dermenev, A ; Donskov, S ; Dusaev, R et al. /NA64
We report the results of a search for a light pseudoscalar particle $a$ that couples to electrons and decays to $e^+e^-$ performed using the high-energy CERN SPS H4 electron beam. If such pseudoscalar with a mass $\simeq 17$ MeV exists, it could explain the ATOMKI anomaly. [...]
CERN-EP-2021-069.- Geneva : CERN, 2021 - 6. Draft (restricted): PDF; Fulltext: PDF;

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Search for Dark Sector Physics in Missing Energy Events in the NA64 Experiment / Kirsanov, Mikhail (Moscow, INR)
A search is performed for a new sub-GeV vector boson (A′) mediated production of Dark Matter (χ) in the fixed-target experiment, NA64, at the CERN SPS. The A′, called dark photon, could be generated in the reaction e−Z → e−ZA′ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay A′→χχ¯. [...]
2019 - 17 p. - Published in : 10.1142/9789811202339_0066
In : 18th Lomonosov Conference on Elementary Particle Physics : Particle Physics at the Silver Jubilee of Lomonosov Conferences, Moscow, Russia, 24 - 30 Aug 2017, pp.353-369

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The Search for Light Dark Matter at NA64 Experiment / Krasnikov, N V (Moscow, INR ; Dubna, JINR)
This minireview aim is to outline the main experimental results related to the search for LDM (light dark matter) at NA64 experiment at CERN. We discuss current results and the NA64 perspectives. [...]
2020 - 6 p. - Published in : Phys. Part. Nucl. 51 (2020) 697-702
In : International Bogolyubov Conference Problems of Theoretical and Mathematical Physics (BOG), Moscow, Russian Federation, 9 - 13 Sep 2019, pp.697-702

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Constraints on New Physics in the Electron g-2 from a Search for Invisible Decays of a Scalar, Pseudoscalar, Vector, and Axial Vector / NA64 Collaboration
We performed a search for a new generic $X$ boson, which could be a scalar ($S$), pseudoscalar ($P$), vector ($V$) or an axial vector ($A$) particle produced in the 100 GeV electron scattering off nuclei, $e^- Z \to e^- Z X$, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such process was found in the full NA64 data set of $2.84\times 10^{11}$ electrons on target. [...]
arXiv:2102.01885; CERN-EP-2021-017.- 2021-05-26 - 6 p. - Published in : Phys. Rev. Lett. 126 (2021) 21 Article from SCOAP3: PDF;

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Hunting down the X17 boson at the CERN SPS / NA64 Collaboration
Recently, the ATOMKI experiment has reported new evidence for the excess of $e^+ e^-$ events with a mass $\sim$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 $X17$ boson. [...]
arXiv:2009.02756.- 2020-12-15 - 17 p. - Published in : Eur. Phys. J. C 80 (2020) 1159

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Photoproduction of axionlike particles in the NA64 experiment / Dusaev, R.R. (Tomsk State U.) ; Kirpichnikov, D.V. (Moscow, INR) ; Kirsanov, M.M. (Moscow, INR)
Axion-like particles $a$ (ALPs) that couple to the Standard Model (SM) gauge fields could be observed in the high-energy photon scattering $\gamma N\to N a$ off nuclei followed by the $a\to \gamma\gamma$ decay. In the present paper we describe the calculation of the ALP production cross-section and the properties of this production. [...]
arXiv:2004.04469.- 2020-09-29 - 8 p. - Published in : Phys. Rev. D 102 (2020) 055018 Article from SCOAP3: PDF; Fulltext: PDF;

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Status and Plans for the NA64 Experiment / Bernhard, J (CERN) /NA64 Collaboration ; Physics Beyond Collider Conventional Beams working group Collaboration
The NA64 experiment at the CERN North Area searches for dark matter production via both visible and invisible decays of sub-GeV vector mediators, such as the dark photon $A$´. In a first data taking period from 2016-2018, $A$' generation from the reaction e Z $\rightarrow$ e Z $A$' and subsequent decays $A$´ $\rightarrow x\overline{x}$ and $A$´ $\rightarrow$ e$^+$e$^-$ was studied with the help of an active dump set-up using 100 GeV/$c$ and 150 GeV/$c$ electrons. [...]
IOP, 2020 - 4 p. - Published in : J. Phys.: Conf. Ser. 1468 (2020) 012023 Published fulltext: PDF;
In : 16th International Conference on Topics in Astroparticle and Underground Physics, Toyama, Japan, 9 - 13 Sep 2019, pp.012023

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Search for Axionlike and Scalar Particles with the NA64 Experiment / NA64 Collaboration
We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. [...]
arXiv:2005.02710; CERN-EP-2020-068.- 2020-08-17 - 7 p. - Published in : Phys. Rev. Lett. 125 (2020) 8 Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: PDF;

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