002287528 001__ 2287528
002287528 005__ 20240613055847.0
002287528 0248_ $$aoai:cds.cern.ch:2287528$$pcerncds:CERN$$pcerncds:CERN:FULLTEXT$$pcerncds:FULLTEXT
002287528 0247_ $$2DOI$$a10.1103/PhysRevD.97.072002
002287528 037__ $$9arXiv$$aarXiv:1710.00971$$chep-ex
002287528 035__ $$9arXiv$$aoai:arXiv.org:1710.00971
002287528 035__ $$9Inspire$$aoai:inspirehep.net:1628408$$d2024-06-12T09:39:35Z$$h2024-06-13T02:00:56Z$$mmarcxml$$ttrue$$uhttps://inspirehep.net/api/oai2d
002287528 035__ $$9Inspire$$a1628408
002287528 041__ $$aeng
002287528 100__ $$aBanerjee, D.$$uZurich, ETH$$vETH Zürich, Institute for Particle Physics , CH-8093 Zürich, Switzerland
002287528 245__ $$9arXiv$$aSearch for vector mediator of Dark Matter production in invisible decay mode
002287528 269__ $$c2017-10-02
002287528 260__ $$c2018-04-04
002287528 300__ $$a21 p
002287528 500__ $$9arXiv$$a22 pages, 17 figures, version accepted for publication in PRD
002287528 520__ $$9APS$$aA search is performed for a new sub-GeV vector boson (A′) mediated production of dark matter (χ) in the fixed-target experiment, NA64, at the CERN SPS. The A′, called dark photon, can be generated in the reaction e-Z→e-ZA′ of 100 GeV electrons dumped against an active target followed by its prompt invisible decay A′→χχ¯. The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to 4.3×1010 electrons on target no evidence of such a process has been found. New stringent constraints on the A′ mixing strength with photons, 10-5≲ε≲10-2, for the A′ mass range mA′≲1 GeV are derived. For models considering scalar and fermionic thermal dark matter interacting with the visible sector through the vector portal the 90% C.L. limits 10-11≲y≲10-6 on the dark-matter parameter y=ε2αD(mχmA′)4 are obtained for the dark coupling constant αD=0.5 and dark-matter masses 0.001≲mχ≲0.5 GeV. The lower limits αD≳10-3 for pseudo-Dirac dark matter in the mass region mχ≲0.05 GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using exact tree level calculations of the A′ production cross sections, which turn out to be significantly smaller compared to the one obtained in the Weizsäcker-Williams approximation for the mass region mA′≳0.1 GeV.
002287528 520__ $$9arXiv$$aA search is performed for a new sub-GeV vector boson ($A'$) mediated production of Dark Matter ($\chi$) in the fixed-target experiment, NA64, at the CERN SPS. The $A'$, called dark photon, could be generated in the reaction $ e^- Z \to e^- Z A'$ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay $A' \to \chi \overline{\chi}$. The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to $4.3\times10^{10}$ electrons on target no evidence of such a process has been found. New stringent constraints on the $A'$ mixing strength with photons, $10^{-5}\lesssim \epsilon \lesssim 10^{-2}$, for the $A'$ mass range $m_{A'} \lesssim 1$ GeV are derived. For models considering scalar and fermionic thermal Dark Matter interacting with the visible sector through the vector portal the 90% C.L. limits $10^{-11}\lesssim y \lesssim 10^{-6}$ on the dark-matter parameter $y = \epsilon^2 \alpha_D (\frac{m_\chi}{m_{A'}})^4 $ are obtained for the dark coupling constant $\alpha_D = 0.5$ and dark-matter masses $0.001 \lesssim m_\chi \lesssim 0.5 $ GeV. The lower limits $\alpha_D \gtrsim 10^{-3} $ for pseudo-Dirac Dark Matter in the mass region $m_\chi \lesssim 0.05 $ GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using tree level, exact calculations of the $A'$ production cross-sections, which turn out to be significantly smaller compared to the one obtained in the Weizs\"{a}cker-Williams approximation for the mass region $m_{A'} \gtrsim 0.1$ GeV.
002287528 540__ $$aarXiv nonexclusive-distrib. 1.0$$barXiv$$uhttp://arxiv.org/licenses/nonexclusive-distrib/1.0/
002287528 542__ $$3Publication$$dauthors$$g2018
002287528 65017 $$2arXiv$$ahep-ph
002287528 65017 $$2SzGeCERN$$aParticle Physics - Phenomenology
002287528 65017 $$2arXiv$$ahep-ex
002287528 65017 $$2SzGeCERN$$aParticle Physics - Experiment
002287528 693__ $$aCERN SPS$$eNA64
002287528 690C_ $$aCERN
002287528 690C_ $$aARTICLE
002287528 700__ $$aBurtsev, V.E.$$uTomsk Polytechnic U.$$uZurich, ETH$$vTomsk Polytechnic University, 634050 Tomsk, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aChumakov, A.G.$$uTomsk Polytechnic U.$$uZurich, ETH$$vTomsk Polytechnic University, 634050 Tomsk, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aCooke, D.$$uZurich, ETH$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aCrivelli, P.$$uZurich, ETH$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aDepero, E.$$uZurich, ETH$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aDermenev, A.V.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aDonskov, S.V.$$uSerpukhov, IHEP$$uZurich, ETH$$vState Scientific Center of the Russian Federation Institute for High Energy Physics of National Research Center 'Kurchatov Institute' (IHEP), 142281 Protvino, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aDubinin, F.$$uLebedev Inst.$$uZurich, ETH$$vP. N. Lebedev Physics Institute, Moscow, Russia, 119 991 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aDusaev, R.R.$$uTomsk Polytechnic U.$$uZurich, ETH$$vTomsk Polytechnic University, 634050 Tomsk, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aEmmenegger, S.$$uZurich, ETH$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aFabich, A.$$uCERN$$uZurich, ETH$$vCERN, European Organization for Nuclear Research, CH-1211 Geneva, Switzerland$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aFrolov, V.N.$$uDubna, JINR$$uZurich, ETH$$vJoint Institute for Nuclear Research, 141980 Dubna, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aGardikiotis, A.$$uPatras U.$$uZurich, ETH$$vPhysics Department, University of Patras, Patras, Greece$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aGerassimov, S.G.$$uMunich, Tech. U.$$uLebedev Inst.$$uZurich, ETH$$vTechnische UniversitätMünchen, Physik Dept., 85748 Garching, Germany$$vP. N. Lebedev Physics Institute, Moscow, Russia, 119 991 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aGninenko, S.N.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aHösgen, M.$$uBonn U., HISKP$$uZurich, ETH$$vUniversität Bonn, Helmholtz-Institut für Strahlen-und Kernphysik, 53115 Bonn, Germany$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKarneyeu, A.E.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKetzer, B.$$uBonn U., HISKP$$uZurich, ETH$$vUniversität Bonn, Helmholtz-Institut für Strahlen-und Kernphysik, 53115 Bonn, Germany$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKirpichnikov, D.V.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKirsanov, M.M.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKonorov, I.V.$$uMunich, Tech. U.$$uLebedev Inst.$$uZurich, ETH$$vTechnische UniversitätMünchen, Physik Dept., 85748 Garching, Germany$$vP. N. Lebedev Physics Institute, Moscow, Russia, 119 991 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKovalenko, S.G.$$uCCTVal, Valparaiso$$uZurich, ETH$$vUniversidad Técnica Federico Santa María, 2390123 Valparaíso, Chile$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKramarenko, V.A.$$uSINP, Moscow$$uDubna, JINR$$uZurich, ETH$$vSkobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia$$vJoint Institute for Nuclear Research, 141980 Dubna, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKravchuk, L.V.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKrasnikov, N.V.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aKuleshov, S.V.$$uCCTVal, Valparaiso$$uZurich, ETH$$vUniversidad Técnica Federico Santa María, 2390123 Valparaíso, Chile$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aLyubovitskij, V.E.$$uSanta Maria U., Valparaiso$$uTomsk Polytechnic U.$$uZurich, ETH$$vUniversidad Técnica Federico Santa María, 2390123 Valparaíso, Chile$$vTomsk Polytechnic University, 634050 Tomsk, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aLysan, V.$$uDubna, JINR$$uZurich, ETH$$vJoint Institute for Nuclear Research, 141980 Dubna, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aMatveev, V.A.$$uDubna, JINR$$uZurich, ETH$$vJoint Institute for Nuclear Research, 141980 Dubna, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aMikhailov, Yu.V.$$uSerpukhov, IHEP$$uZurich, ETH$$vState Scientific Center of the Russian Federation Institute for High Energy Physics of National Research Center 'Kurchatov Institute' (IHEP), 142281 Protvino, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aPeshekhonov, D.V.$$uDubna, JINR$$uZurich, ETH$$vJoint Institute for Nuclear Research, 141980 Dubna, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aPolyakov, V.A.$$uSerpukhov, IHEP$$uZurich, ETH$$vState Scientific Center of the Russian Federation Institute for High Energy Physics of National Research Center 'Kurchatov Institute' (IHEP), 142281 Protvino, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aRadics, B.$$uZurich, ETH$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aRubbia, A.$$uZurich, ETH$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aSamoylenko, V.D.$$uSerpukhov, IHEP$$uZurich, ETH$$vState Scientific Center of the Russian Federation Institute for High Energy Physics of National Research Center 'Kurchatov Institute' (IHEP), 142281 Protvino, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aTikhomirov, V.O.$$uLebedev Inst.$$uZurich, ETH$$vP. N. Lebedev Physics Institute, Moscow, Russia, 119 991 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aTlisov, D.A.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aToropin, A.N.$$uMoscow, INR$$uZurich, ETH$$vInstitute for Nuclear Research, 117312 Moscow, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aTrifonov, A.Yu.$$uTomsk Polytechnic U.$$uZurich, ETH$$vTomsk Polytechnic University, 634050 Tomsk, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aVasilishin, B.I.$$uTomsk Polytechnic U.$$uZurich, ETH$$vTomsk Polytechnic University, 634050 Tomsk, Russia$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aVasquez Arenas, G.$$uSanta Maria U., Valparaiso$$uZurich, ETH$$vUniversidad Técnica Federico Santa María, 2390123 Valparaíso, Chile$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 700__ $$aUlloa, P.$$uSanta Maria U., Valparaiso$$uZurich, ETH$$vUniversidad Técnica Federico Santa María, 2390123 Valparaíso, Chile$$vETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland
002287528 710__ $$gNA64 Collaboration
002287528 773__ $$c072002$$pPhys. Rev. D$$v97$$xPhys.Rev. D 97 (2018) no.7, 072002$$y2018
002287528 8564_ $$82216329$$s155262$$uhttp://cds.cern.ch/record/2287528/files/HCvsEC-2366-2436-nocuts.png$$y00006 Event distribution in the ($E_{ECAL}$;$E_{HCAL}$) plane from the runs II(top row) and III (bottom row) data. The left panels show the measured distribution of events at the earlier phase of the analysis. Plots in the middle show the same distribution after applying all selection criteria, but the cut against upstream interactions. The right plots present the final event distributions after all cuts applied. The dashed area is the signal box region which is open. The side bands A and C are the one used for the background estimate inside the signal box. For illustration purposes the size of the signal box along $E_{HCAL}$-axis is increased by a factor five.
002287528 8564_ $$82216330$$s54575$$uhttp://cds.cern.ch/record/2287528/files/HCvsEC-2366-2436-upper-nostats.png$$y00007 Event distribution in the ($E_{ECAL}$;$E_{HCAL}$) plane from the runs II(top row) and III (bottom row) data. The left panels show the measured distribution of events at the earlier phase of the analysis. Plots in the middle show the same distribution after applying all selection criteria, but the cut against upstream interactions. The right plots present the final event distributions after all cuts applied. The dashed area is the signal box region which is open. The side bands A and C are the one used for the background estimate inside the signal box. For illustration purposes the size of the signal box along $E_{HCAL}$-axis is increased by a factor five.
002287528 8564_ $$82216331$$s32511$$uhttp://cds.cern.ch/record/2287528/files/variant10.png$$y00012 Selected dimuon events in the $(E_{ECAL};E_{HCAL})$ plane.
002287528 8564_ $$82216332$$s12109$$uhttp://cds.cern.ch/record/2287528/files/invis_dimu2443_2445_smeared_var.png$$y00015 Distribution of energy deposited in the ECAL target by the scattered electron from the reaction \eqref{dimu} for the selected dimuon events from the data sample of the run III (red points) and MC events (green histogram). Spectra are normalized to the same number of events. The unnormalized MC distribution (top histogram) is also shown with corresponding errors for the each bin.
002287528 8564_ $$82216333$$s4196$$uhttp://cds.cern.ch/record/2287528/files/inh-tldra-20-2-0609.png$$y00025 The NA64 constraints in the ($\alpha_D$;$m_{A'}$) plane on the pseudo-Dirac (the left panel) and Majorana ( right panel) type light thermal DM shown in comparison with bounds obtained in Ref. \cite{report2} from the results of the LSND~\cite{deNiverville:2011it,Batell:2009di}, E137 \cite{e137th}, BaBar \cite{babarg-2} and MiniBooNE \cite{minib2017} experiments.
002287528 8564_ $$82216334$$s2053721$$uhttp://cds.cern.ch/record/2287528/files/scoap3-fulltext.pdf$$yArticle from SCOAP3
002287528 8564_ $$82216335$$s1348379$$uhttp://cds.cern.ch/record/2287528/files/arXiv:1710.00971.pdf
002287528 8564_ $$82216336$$s54540$$uhttp://cds.cern.ch/record/2287528/files/NA64_top_2016.png$$y00004 Schematic illustration of the setup to search for $\ainv$ decays of the bremsstrahlung $A'$s produced in the reaction $eZ\rightarrow eZ A'$ of 100 GeV e$^-$ incident on the active ECAL target.
002287528 8564_ $$82216337$$s3015$$uhttp://cds.cern.ch/record/2287528/files/diagrinv.png$$y00000 Diagram contributing to the $A'$ production in the reaction $e^- Z \rightarrow e^- Z A', A' \rightarrow dark~sector$. The produced $A'$ decays invisibly into dark sector particles.
002287528 8564_ $$82216338$$s4617$$uhttp://cds.cern.ch/record/2287528/files/tldra-19-2-2.png$$y00022 The NA64 limits in the (y;$m_{\chi}$) plane obtained for $\alpha_D=0.5$ (left panel) and $\alpha_D=0.005$ (right panel) from the full 2016 data set shown in comparison with limits obtained in Refs.\cite{report1,Izaguirre:2014bca,Iza2015,Iza2017} from the results of the LSND~\cite{deNiverville:2011it,Batell:2009di}, E137 \cite{e137th}, BaBar \cite{babarg-2}, MiniBooNE \cite{minib2017} and direct detection \cite{mardon}experiments. The favoured parameters to account for the observed relic DM density for the scalar, pseudo-Dirac and Majorana type of light thermal DM are shown as the lowest solid line.
002287528 8564_ $$82216339$$s8329$$uhttp://cds.cern.ch/record/2287528/files/signal_spectra.png$$y00005 The MC distributions of energy deposited in the ECAL target from the reaction $eZ\rightarrow eZ A'$ induced by 100 GeV e$^-$s and accompanied by the emission of the bremsstrahlung $A'$s with the mass 2 (green), 20(blue) and 200 (red) MeV.
002287528 8564_ $$82216340$$s31253$$uhttp://cds.cern.ch/record/2287528/files/d-ratio-mk.png$$y00015 Double ratio $RR$ as a function of the ECAL energy.
002287528 8564_ $$82216341$$s26055$$uhttp://cds.cern.ch/record/2287528/files/plot-opt.png$$y00019 The sensitivity, defined as an average expected limit, as a function of the ECAL energy cut for the case of the $A'$ detection with the mass $\ma \simeq 20 $ MeV.
002287528 8564_ $$82216342$$s6945$$uhttp://cds.cern.ch/record/2287528/files/HCAL3_dimu2351-1.png$$y00014 Comparison of expected (solid) and measured (dots) distributions of dimuon events in the HCAL2 (left panel) and HCAL module 3 (right panel). The small bump at $\simeq2.5$ GeV originates from a single muon of the pair when the other one stops in the previous module. The spectra are normalised to the same number of events.
002287528 8564_ $$82216343$$s45036$$uhttp://cds.cern.ch/record/2287528/files/d-ratio-new-2.png$$y00016 Double ratio $RR$ as a function of the ECAL energy. The color curves represent an example of the empirical fitting functions.
002287528 8564_ $$82216344$$s153572$$uhttp://cds.cern.ch/record/2287528/files/HCvsEC-2441-2457-nocuts.png$$y00009 Event distribution in the ($E_{ECAL}$;$E_{HCAL}$) plane from the runs II(top row) and III (bottom row) data. The left panels show the measured distribution of events at the earlier phase of the analysis. Plots in the middle show the same distribution after applying all selection criteria, but the cut against upstream interactions. The right plots present the final event distributions after all cuts applied. The dashed area is the signal box region which is open. The side bands A and C are the one used for the background estimate inside the signal box. For illustration purposes the size of the signal box along $E_{HCAL}$-axis is increased by a factor five.
002287528 8564_ $$82216345$$s57286$$uhttp://cds.cern.ch/record/2287528/files/r2366-2436-4.png$$y00019 Energy distribution of events in the side band C collected in the run II with intensity $\simeq 3.5\times 10^6~e^-$/spill and obtained with pileup algorithm. The curve shows single exponential fit to the data, while the dashed one represents extrapolation to the signal region which predicts $n_b = 0.041\pm 0.02$ background events.
002287528 8564_ $$82216346$$s40354$$uhttp://cds.cern.ch/record/2287528/files/HCvsEC-2441-2457-aftercuts.png$$y00011 Event distribution in the ($E_{ECAL}$;$E_{HCAL}$) plane from the runs II(top row) and III (bottom row) data. The left panels show the measured distribution of events at the earlier phase of the analysis. Plots in the middle show the same distribution after applying all selection criteria, but the cut against upstream interactions. The right plots present the final event distributions after all cuts applied. The dashed area is the signal box region which is open. The side bands A and C are the one used for the background estimate inside the signal box. For illustration purposes the size of the signal box along $E_{HCAL}$-axis is increased by a factor five.
002287528 8564_ $$82216347$$s14773$$uhttp://cds.cern.ch/record/2287528/files/SpectraOfDarkPhotonVariousMA.png$$y00003 The $A'$ emission spectra from the 100 GeV electron beam interactions in the thick Pb target ($t\gg X_0$, see Sec.III)) calculated for the masses $m_{A'}=10$ and 100~MeV without and with the IWW approximation. The spectra are normalized to the same number of EOT.
002287528 8564_ $$82216348$$s60939$$uhttp://cds.cern.ch/record/2287528/files/DiFFCrossSectionNoWW-2.png$$y00002 The differential $A'$ spectra from the electron beam interactions in the thin ($\ll X_0)$ Pb target calculated for the mass $m_{A'}=100$~MeV as a function of $x=E_{A'}/ E_e$. The spectra are computed for different electron energies as indicated in the legend. The spectra are normalized to the same number of EOT.
002287528 8564_ $$82216349$$s44896$$uhttp://cds.cern.ch/record/2287528/files/HCvsEC-2441-2457-upper-nostats.png$$y00010 Event distribution in the ($E_{ECAL}$;$E_{HCAL}$) plane from the runs II(top row) and III (bottom row) data. The left panels show the measured distribution of events at the earlier phase of the analysis. Plots in the middle show the same distribution after applying all selection criteria, but the cut against upstream interactions. The right plots present the final event distributions after all cuts applied. The dashed area is the signal box region which is open. The side bands A and C are the one used for the background estimate inside the signal box. For illustration purposes the size of the signal box along $E_{HCAL}$-axis is increased by a factor five.
002287528 8564_ $$82216350$$s8451$$uhttp://cds.cern.ch/record/2287528/files/Exact_IWW_Vs_E0.png$$y00001 The $k$-factor for the $A'$ production in the reaction $e^- Z \rightarrow e^- Z A'$ as a function of the electron energy $E_0$ for different values of the $A'$ masses.
002287528 8564_ $$82216351$$s41002$$uhttp://cds.cern.ch/record/2287528/files/sensopt.png$$y00020 The sensitivity, defined as an average expected limit, as a function of the ECAL energy cut for the case of the $A'$ detection with the mass $\ma \simeq 20 $ (blue) and 2 (green) MeV.
002287528 8564_ $$82216352$$s45844$$uhttp://cds.cern.ch/record/2287528/files/HCvsEC-2366-2436-aftercuts.png$$y00008 Event distribution in the ($E_{ECAL}$;$E_{HCAL}$) plane from the runs II(top row) and III (bottom row) data. The left panels show the measured distribution of events at the earlier phase of the analysis. Plots in the middle show the same distribution after applying all selection criteria, but the cut against upstream interactions. The right plots present the final event distributions after all cuts applied. The dashed area is the signal box region which is open. The side bands A and C are the one used for the background estimate inside the signal box. For illustration purposes the size of the signal box along $E_{HCAL}$-axis is increased by a factor five.
002287528 8564_ $$82216353$$s8184$$uhttp://cds.cern.ch/record/2287528/files/HCAL2_dimu2351-1.png$$y00013 Comparison of expected (solid) and measured (dots) distributions of dimuon events in the HCAL2 (left panel) and HCAL module 3 (right panel). The small bump at $\simeq2.5$ GeV originates from a single muon of the pair when the other one stops in the previous module. The spectra are normalised to the same number of events.
002287528 8564_ $$82216354$$s47528$$uhttp://cds.cern.ch/record/2287528/files/zero-energy.png$$y00018 The left hand side panel shows distribution of the leak energy from the ECAL to the HCAL from the 100 GeV e-. The right hand side panel represents the 100 GeV $e^-$ detection efficiencies as a function of the HCAL energy threshold.
002287528 8564_ $$82216355$$s4691$$uhttp://cds.cern.ch/record/2287528/files/tldra-19-2-0110.png$$y00023 The NA64 limits in the (y;$m_{\chi}$) plane obtained for $\alpha_D=0.5$ (left panel) and $\alpha_D=0.005$ (right panel) from the full 2016 data set shown in comparison with limits obtained in Refs.\cite{report1,Izaguirre:2014bca,Iza2015,Iza2017} from the results of the LSND~\cite{deNiverville:2011it,Batell:2009di}, E137 \cite{e137th}, BaBar \cite{babarg-2}, MiniBooNE \cite{minib2017} and direct detection \cite{mardon}experiments. The favoured parameters to account for the observed relic DM density for the scalar, pseudo-Dirac and Majorana type of light thermal DM are shown as the lowest solid line.
002287528 8564_ $$82216356$$s3657$$uhttp://cds.cern.ch/record/2287528/files/exclusionInvisible-1909.png$$y00021 The NA64 90\% C.L. exclusion region in the ($m_{A'}, \epsilon$) plane. Constraints from the BaBar \cite{babarg-2}, E787 and E949 experiments \cite{hd,Essig:2013vha}, as well as the muon $\alpha_\mu$ favored area are also shown. Here, $\alpha_\mu =\frac{g_\mu-2}{2}$. For more limits obtained from indirect searches and planned measurements see e.g. Ref. \cite{report1,report2}.
002287528 8564_ $$82216357$$s8460$$uhttp://cds.cern.ch/record/2287528/files/DarkPhotonKfSpectra100MeV-1.png$$y00002 The $A'$ emission spectra from the 100 GeV electron beam interactions in the thick Pb target ($t\gg X_0$) calculated for the mass $m_{A'}=100$~MeV without (green ) and with (red) WW approximation. The spectra are normalized to the same number of EOT.
002287528 8564_ $$82216358$$s8600$$uhttp://cds.cern.ch/record/2287528/files/HCAL0_2363.png$$y00017 The left hand side panel shows distribution of the leak energy from the ECAL to the HCAL from the 100 GeV e-. The right hand side panel represents the 100 GeV $e^-$ detection efficiencies as a function of the HCAL energy threshold.
002287528 8564_ $$82216359$$s3100$$uhttp://cds.cern.ch/record/2287528/files/inh-tldra-20-1-k025-0609.png$$y00024 The NA64 constraints in the ($\alpha_D$;$m_{A'}$) plane on the pseudo-Dirac (the left panel) and Majorana ( right panel) type light thermal DM shown in comparison with bounds obtained in Ref. \cite{report2} from the results of the LSND~\cite{deNiverville:2011it,Batell:2009di}, E137 \cite{e137th}, BaBar \cite{babarg-2} and MiniBooNE \cite{minib2017} experiments.
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