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CERN Document Server 2,050 záznamov nájdených  1 - 10ďalšíkoniec  skoč na záznam: Hľadanie trvalo 2.10 sekúnd. 
1.
Search for Light Dark Matter with NA64 at CERN / NA64 Collaboration
Thermal dark matter models with particle $\chi$ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble interaction between the dark and ordinary matter. [...]
arXiv:2307.02404; CERN-EP-2023-130.- 2023-10-16 - 7 p. - Published in : Phys. Rev. Lett. 131 (2023) 161801 Fulltext: 2307.02404 - PDF; Publication - PDF;
2.
First Results in the Search for Dark Sectors at NA64 with the CERN SPS High Energy Muon Beam / NA64 Collaboration
We report on a search for a new $Z'$ ($L_\mu-L_\tau$) vector boson performed at the NA64 experiment employing a high energy muon beam and a missing energy-momentum technique. Muons from the M2 beamline at the CERN Super Proton Synchrotron with a momentum of 160 GeV/c are directed to an active target. [...]
arXiv:2401.01708; CERN-EP-2023-306.- Geneva : CERN, 2024-05-21 - 5 p. - Published in : Phys. Rev. Lett. 132 (2024) 211803 Draft (restricted): PDF; Fulltext: CERN-EP-2023-306 - PDF; Publication - PDF; 2401.01708 - PDF;
3.
Probing light dark matter with positron beams at NA64 / NA64 Collaboration
We present the results of a missing-energy search for Light Dark Matter which has a new interaction with ordinary matter transmitted by a vector boson, called dark photon ($A^\prime$). For the first time, this search is performed with a positron beam by using the significantly enhanced production of $A^\prime$ in the resonant annihilation of positrons with atomic electrons of the target nuclei, followed by the invisible decay of $A^\prime$ into dark matter. [...]
arXiv:2308.15612; CERN-EP-2023-192.- Geneva : CERN, 2024-02-01 - 6 p. - Published in : Phys. Rev. D 109 (2024) L031103 Draft (restricted): PDF; Fulltext: CERN-EP-2023-192 - PDF; 2308.15612 - PDF; Publication - PDF;
4.
Measurement of the intrinsic hadronic contamination in the NA64<math altimg="si2.svg" display="inline" id="d1e670"><mrow><mo>−</mo><mi>e</mi></mrow></math> high-purity <math altimg="si3.svg" display="inline" id="d1e678"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>/</mo><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> beam at CERN / Andreev, Yu.M. (Unlisted) ; Banerjee, D. (CERN) ; Oberhauser, B. Banto (Zurich, ETH) ; Bernhard, J. (CERN) ; Bisio, P. (INFN, Genoa ; Genoa U.) ; Bondí, M. (INFN, Catania) ; Celentano, A. (INFN, Genoa) ; Charitonidis, N. (CERN) ; Chumakov, A.G. (Unlisted) ; Cooke, D. (University Coll. London) et al.
In this study, we present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c momentum. The analysis was performed using data collected by the NA64-$e$ experiment in 2022. [...]
arXiv:2305.19411; CERN-EP-2023-108.- Geneva : CERN, 2023-10-12 - 8 p. - Published in : Nucl. Instrum. Methods Phys. Res., A 1057 (2023) 168776 Draft (restricted): PDF; Fulltext: 2305.19411 - PDF; Publication - PDF; CERN-EP-2023-108 - PDF;
5.
First constraints on the L$_{μ}$− L$_{τ}$ explanation of the muon g-2 anomaly from NA64-e at CERN / NA64 Collaboration
The inclusion of an additional $U(1)$ gauge $L_\mu-L_\tau$ 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 $Z^\prime$ vector boson, with dominant coupling to $\mu$ and $\tau$ leptons and interacting with electrons via a loop mechanism. The $L_\mu-L_\tau$ model can also explain the Dark Matter relic abundance, by assuming that the $Z^\prime$ boson acts as a ``portal'' to a new Dark Sector of particles in Nature, not charged under known interactions. [...]
arXiv:2404.06982; CERN-EP-2024-103.- Geneva : CERN, 2024-07-23 - 15 p. - Published in : JHEP 2407 (2024) 212 Draft (restricted): PDF; Fulltext: CERN-EP-2024-103 - PDF; document - PDF; NA64-PAPER-24-02 - PDF; 2404.06982 - PDF;
6.
Discovering heavy neutrino oscillations in rare $B^\pm_c$ meson decays at HL-LHCb / Tapia, Sebastian (Iowa State U.) ; Vidal-Bravo, Marcelo (Andres Bello Natl. U. ; Unlisted, CL) ; Zamora-Saa, Jilberto (Andres Bello Natl. U. ; Unlisted, CL)
In this work, we study the lepton flavor and lepton number violating $B_{c}$ meson decays via two intermediate on-shell Majorana neutrinos $N_j$ into two charged leptons and a charged pion $B_{c}^{\pm} \to \mu^{\pm} \ N_j \to \mu^{\pm} \tau^{\pm} \pi^{\mp}$. We evaluated the possibility to measure the modulation of the decay width along the detector length produced as a consequence of the lepton flavor violating process, in a scenario where the heavy neutrinos masses range between $2.0$ GeV $\leq M_N \leq 6.0$ GeV. [...]
arXiv:2109.06027.- 2022-02-01 - 15 p. - Published in : Phys. Rev. D 105 (2022) 035003 Fulltext: PhysRevD.105.035003 - PDF; 2109.06027 - PDF;
7.
Dark-Sector Search via Pion-Produced η and η′ Mesons Decaying Invisibly in the NA64h Detector / NA64 Collaboration
We present the first results from a proof-of-concept search for dark sectors via invisible decays of pseudoscalar η and η′ mesons in the NA64h experiment at the CERN SPS. Our novel technique uses the charge-exchange reaction of 50 GeV π- on nuclei of an active target as the source of neutral mesons. [...]
2024 - 6 p. - Published in : Phys. Rev. Lett. 133 (2024) 121803 Fulltext: PDF;
8.
Shedding light on Dark Sectors with high-energy muons at the NA64 experiment at the CERN SPS / Andreev, Yu.M. (Unlisted) ; Banerjee, D. (CERN) ; Banto Oberhauser, B. (Zurich, ETH) ; Bernhard, J. (CERN) ; Bisio, P. (Kobe U. ; INFN, Genoa) ; Charitonidis, N. (CERN) ; Crivelli, P. (Zurich, ETH) ; Depero, E. (Zurich, ETH) ; Dermenev, A.V. (Unlisted) ; Donskov, S.V. (Unlisted) et al. /NA64
A search for Dark Sectors is performed using the unique M2 beam line at the CERN Super Proton Synchrotron. New particles ($X$) could be produced in the bremsstrahlung-like reaction of high energy 160 GeV muons impinging on an active target, $\mu N\rightarrow\mu NX$, followed by their decays, $X\rightarrow\text{invisible}$. [...]
arXiv:2409.10128; CERN-EP-2024-236.- Geneva : CERN, 2024 - 24 p. Draft (restricted): PDF; Fulltext: CERN-EP-2024-236 - PDF; 2409.10128 - PDF;
9.
Search for a New $B$ - $L$ $Z'$ Gauge Boson with the NA64 Experiment at CERN / NA64 Collaboration
A search for a new $Z'$ gauge boson associated with (un)broken B-L symmetry in the keV-GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22e11 electrons on target collected during 2016-2021 runs no signal events were found. [...]
arXiv:2207.09979; CERN-EP-2022-156.- 2022-10-12 - 6 p. - Published in : Phys. Rev. Lett. 129 (2022) 161801 Fulltext: PDF;
10.
Model-independent measurement of charm mixing parameters in $\bar{B} \rightarrow D^0 ( \rightarrow K_S^0 \pi^+ \pi^-) \mu^- \bar{\nu}_\mu X$ decays / LHCb Collaboration
A measurement of charm mixing and $CP$-violating parameters is reported, using $\bar{B} \rightarrow D^0 ( \rightarrow K_S^0 \pi^+ \pi^-) \mu^-\bar{\nu}_\mu X$ decays reconstructed in proton-proton collisions collected by the LHCb experiment during the years 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb$^{-1}$. The measured mixing and $CP$-violating parameters are $x_{\rm CP} = [ \,\,\,\,\,4.29 \pm 1.48 \mbox{(stat)} \pm 0.26 \mbox{(syst)} ] \times 10^{-3}\,, $ $y_{\rm CP} = [ \,\,12.61 \pm 3.12 \mbox{(stat)} \pm 0.83 \mbox{(syst)} ] \times 10^{-3} \,, $ $\Delta x \,\,= [ -0.77 \pm 0.93 \mbox{(stat)} \pm 0.28 \mbox{(syst)} ] \times 10^{-3} \,,$ $\Delta y \, = [ \,\,\,\,\,3.01 \pm 1.92 \mbox{(stat)} \pm 0.26 \mbox{(syst)} ] \times 10^{-3} \,.$ The results are complementary to and consistent with previous measurements. [...]
arXiv:2208.06512; LHCb-PAPER-2022-020; CERN-EP-2022-160.- 2023-09-01 - 17 p. - Published in : Phys. Rev. D 108 (2023) 052005 Fulltext: LHCb-PAPER-2022-020_EBFinal - PDF; 2208.06512 - PDF; Publication - PDF; Related data file(s): ZIP;

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