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Improved exclusion limit for light dark matter from $e^+e^-$ annihilation in NA64
/ Andreev, Yu.M. (Moscow, INR) ; Banerjee, D. (CERN) ; Bernhard, J. (CERN) ; Bondi, M. (INFN, Genoa) ; Burtsev, V.E. (Dubna, JINR) ; Celentano, A. (INFN, Genoa) ; Charitonidis, N. (CERN) ; Chumakov, A.G. (Tomsk Polytechnic U. ; Tomsk Pedagogical Inst.) ; Cooke, D. (U. Coll. London) ; Crivelli, P. (Zurich, ETH) et al.
The current most stringent constraints for the existence of sub-GeV dark matter coupling to Standard Model via a massive vector boson $A^\prime$ were set by the NA64 experiment for the mass region $m_{A^\prime}\lesssim 250$ MeV, by analyzing data from the interaction of $2.84\cdot10^{11}$ 100-GeV electrons with an active thick target and searching for missing-energy events. In this work, by including $A^\prime$ production via secondary positron annihilation with atomic electrons, we extend these limits in the $200$-$300$ MeV region by almost an order of magnitude, touching for the first time the dark matter relic density constrained parameter combinations. [...]
arXiv:2108.04195; CERN-EP-2021-164.-
2021-11-01 - 7 p.
- Published in : Phys. Rev. D 104 (2021) L091701
Fulltext: PDF;
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2.
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Probing the explanation of the muon (g-2) anomaly and thermal light dark matter with the semi-visible dark photon channel
/ Cazzaniga, C. (Zurich, ETH) ; Odagiu, P. (Zurich, ETH ; EPFL, Lausanne, FSL) ; Depero, E. (Zurich, ETH) ; Bueno, L. Molina (Zurich, ETH ; Valencia U., IFIC) ; Andreev, Yu. M. (Moscow, INR) ; Banerjee, D. (CERN ; Illinois U., Urbana (main)) ; Bernhard, J. (CERN) ; Burtsev, V.E. (Dubna, JINR) ; Charitonidis, N. (CERN) ; Chumakov, A.G. (Tomsk Pedagogical Inst. ; Tomsk Polytechnic U.) et al.
We report the results of a search for a new vector boson ($\gp$) decaying into two dark matter particles $\chi_1 \chi_2$ of different mass. The heavier $\chi_2$ particle subsequently decays to $\chi_1$ and $\gp \to \pair$. [...]
arXiv:2107.02021.-
Geneva : CERN, 2021-10-30 - 6 p.
- Published in : Eur. Phys. J. C 81 (2021) 959
Draft (restricted): PDF; Fulltext: CERN-EP-2021-129 - PDF; 2107.02021 - PDF; document - PDF;
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3.
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4.
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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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5.
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6.
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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
Article from SCOAP3: PDF; Fulltext: PDF;
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7.
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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: CERN-EP-2020-068 - PDF; 2005.02710 - PDF;
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8.
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Improved limits on a hypothetical X(16.7) boson and a dark photon decaying into $e^+e^-$ pairs
/ NA64 Collaboration
The improved results on a direct search for a new $X$(16.7 MeV) boson which could explain the anomalous excess of $e^+e^-$ pairs observed in the excited $^8Be^*$ nucleus decays ("Berillium anomaly") are reported. Due to its coupling to electrons, the $X$ boson could be produced in the bremsstrahlung reaction $e^-Z\rightarrow e^-ZX$ by a high-energy beam of electrons incident on active target in the NA64 experiment at the CERN SPS and observed through its subsequent decay into $e^+e^-$ pair. [...]
arXiv:1912.11389; CERN-EP-2019-284.-
2020-04-17 - 7 p.
- Published in : Phys. Rev. D 101 (2020) 071101
Article from SCOAP3: PDF; Fulltext: PDF;
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9.
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Dark matter search in missing energy events with NA64
/ NA64 Collaboration
A search for sub-GeV dark matter production mediated by a new vector boson $A'$, called dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with $2.84\times10^{11}$ electrons on target no evidence of such a process has been found. [...]
arXiv:1906.00176; CERN-EP-2019-116.-
2019-09-19 - 7 p.
- Published in : Phys. Rev. Lett. 123 (2019) 121801
Article from SCOAP3: PDF; Fulltext: PDF; Fulltext from Publisher: PDF;
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10.
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Search for a new X(16.7) boson and dark photons in the NA64 experiment at CERN
/ Banerjee, D. (Illinois U., Urbana (main)) ; Burtsev, V.E. (Tomsk Pedagogical Inst.) ; Chumakov, A.G. (Tomsk Pedagogical Inst.) ; Cooke, D. (Zurich, ETH) ; Crivelli, P. (Zurich, ETH) ; Depero, E. (Zurich, ETH) ; Dermenev, A.V. (Moscow, INR) ; Donskov, S.V. (Serpukhov, IHEP) ; Dusaev, R.R. (Tomsk Pedagogical Inst.) ; Enik, T. (Dubna, JINR) et al.
We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e+e- pairs observed in the excited 8Be* nucleus decays. Due to its coupling to electrons, the X could be produced in the bremsstrahlung reaction e-Z -> e-ZX by a 100 GeV e- beam incident on an active target in the NA64 experiment at the CERN SPS and observed through the subsequent decay into a e+e- pair. [...]
arXiv:1803.07748; CERN-EP-2018-043.-
Geneva : CERN, 2018-06-09 - 6 p.
- Published in : Phys. Rev. Lett. 120 (2018) 231802
Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: CERN-EP-2018-043 - PDF; 1803.07748 - PDF; Fulltext from Publisher: PDF;
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