Author
A. Kleimenova
Bio: A. Kleimenova is an academic researcher from Université catholique de Louvain. The author has contributed to research in topics: Branching fraction & Lepton. The author has an hindex of 7, co-authored 11 publications receiving 147 citations.
Papers
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TL;DR: In this article, the upper limits of the | U e 4 | 2 matrix were established at the level of 10 − 9 over most of the accessible heavy neutral lepton mass range with the assumption that the lifetime exceeds 50 ns.
76 citations
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TL;DR: In this paper, the results of a search for π$^{0}$ decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported.
Abstract: The results of a search for π$^{0}$ decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported. From a total of 4.12 × 10$^{8}$ tagged π$^{0}$ mesons, no signal is observed. Assuming a kinetic-mixing interaction, limits are set on the dark photon coupling to the ordinary photon as a function of the dark photon mass, improving on previous searches in the mass range 60–110 MeV/c$^{2}$. The present results are interpreted in terms of an upper limit of the branching ratio of the electro-weak decay $ {\pi}^0\to \gamma
u \overline{
u} $ , improving the current limit by more than three orders of magnitude.
66 citations
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TL;DR: The NA62 experiment at CERN reported a search for the lepton number violating decays K+ → π − e + e + and K + → ε − μ + μ + using a data sample collected in 2017 as discussed by the authors.
35 citations
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TL;DR: The NA62 experiment at CERN reports searches for K + → μ + N and K+ → μ+ ν X decays, where N and X are massive invisible particles, using the 2016-2018 data set.
33 citations
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TL;DR: In this paper, the NA62 experiment achieved a single event sensitivity of (0.389 ± 0.024) × 10−10, corresponding to 2.2 events, assuming the standard model branching ratio of (8.4 ± 1.0)× 10−11.
Abstract: The NA62 experiment reports an investigation of the $$ {K}^{+}\to {\pi}^{+}
u \overline{
u} $$
mode from a sample of K+ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10−10, corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10−10 for the $$ {K}^{+}\to {\pi}^{+}
u \overline{
u} $$
branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of (
$$ {0.48}_{-0.48}^{+0.72} $$
) × 10−10, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.
28 citations
Cited by
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TL;DR: The dark photon is a new gauge boson whose existence has been conjectured as mentioned in this paper, and it is dark because it arises from a symmetry of a hypothetical dark sector comprising particles completely neutral under the Standard Model interactions.
Abstract: The dark photon is a new gauge boson whose existence has been conjectured. It is dark because it arises from a symmetry of a hypothetical dark sector comprising particles completely neutral under the Standard Model interactions. Dark though it is, this new gauge boson can be detected because of its kinetic mixing with the ordinary, visible photon. We review its physics from the theoretical and the experimental point of view. We discuss the difference between the massive and the massless case. We explain how the dark photon enters laboratory, astrophysical and cosmological observations as well as dark matter physics. We survey the current and future experimental limits on the parameters of the massless and massive dark photons together with the related bounds on milli-charged fermions.
200 citations
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CERN1, University of Illinois at Urbana–Champaign2, Joint Institute for Nuclear Research3, Tomsk State Pedagogical University4, University College London5, ETH Zurich6, Kurchatov Institute7, University of Patras8, Technische Universität München9, Lebedev Physical Institute10, University of Bonn11, Federico Santa María Technical University12, Moscow State University13, Andrés Bello National University14
TL;DR: In this article, a search for sub-GeV dark matter production mediated by a new vector boson A^{'}, called a dark photon, is performed by the NA64 experiment in missing energy events from 100GeV electron interactions in an active beam dump at the CERN SPS.
Abstract: A search for sub-GeV dark matter production mediated by a new vector boson A^{'}, called a 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 2.84×10^{11} electrons on target no evidence of such a process has been found. The most stringent constraints on the A^{'} mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range ≲0.2 GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search.
156 citations
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TL;DR: In this article, both prompt-like and long-lived dark photons, A^{'}, produced in proton-proton collisions at a center-of-mass energy of 13 TeV, were searched using a data sample corresponding to an integrated luminosity of 5.5
Abstract: Searches are performed for both promptlike and long-lived dark photons, A^{'}, produced in proton-proton collisions at a center-of-mass energy of 13 TeV. These searches look for A^{'}→μ^{+}μ^{-} decays using a data sample corresponding to an integrated luminosity of 5.5 fb^{-1} collected with the LHCb detector. Neither search finds evidence for a signal, and 90% confidence-level exclusion limits are placed on the γ-A^{'} kinetic mixing strength. The promptlike A^{'} search explores the mass region from near the dimuon threshold up to 70 GeV and places the most stringent constraints to date on dark photons with 214
140 citations
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University of Oxford1, Durham University2, Duke University3, New York University4, University of Zaragoza5, University of Santiago de Compostela6, CERN7, Université catholique de Louvain8, California Institute of Technology9, University of Miami10, Russian Academy of Sciences11, Santa Cruz Institute for Particle Physics12, University of Birmingham13, University of Virginia14, University of Valencia15, Perimeter Institute for Theoretical Physics16, University of Minnesota17, Heidelberg University18, RWTH Aachen University19, University of Chicago20, Royal Holloway, University of London21, University of Massachusetts Amherst22, University of Bologna23, University of Florence24, University of Hamburg25, Niels Bohr Institute26, Princeton University27, SLAC National Accelerator Laboratory28, École Polytechnique Fédérale de Lausanne29, University of Illinois at Urbana–Champaign30, Technion – Israel Institute of Technology31, Institute for the Physics and Mathematics of the Universe32, KEK33, Florida State University34
TL;DR: FIPs 2020 as mentioned in this paper was the first workshop dedicated to the physics of feebly-interacting particles and was held virtually from 31 August to 4 September 2020 at CERN, where experts from collider, beam dump, fixed target experiments, as well as from astrophysics, axions/ALPs searches, current/future neutrino experiments, and dark matter direct detection communities participated.
Abstract: With the establishment and maturation of the experimental programs searching for new physics with sizeable couplings at the LHC, there is an increasing interest in the broader particle and astrophysics community for exploring the physics of light and feebly-interacting particles as a paradigm complementary to a New Physics sector at the TeV scale and beyond. FIPs 2020 has been the first workshop fully dedicated to the physics of feebly-interacting particles and was held virtually from 31 August to 4 September 2020. The workshop has gathered together experts from collider, beam dump, fixed target experiments, as well as from astrophysics, axions/ALPs searches, current/future neutrino experiments, and dark matter direct detection communities to discuss progress in experimental searches and underlying theory models for FIPs physics, and to enhance the cross-fertilisation across different fields. FIPs 2020 has been complemented by the topical workshop "Physics Beyond Colliders meets theory", held at CERN from 7 June to 9 June 2020. This document presents the summary of the talks presented at the workshops and the outcome of the subsequent discussions held immediately after. It aims to provide a clear picture of this blooming field and proposes a few recommendations for the next round of experimental results.
91 citations
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TL;DR: The Forward Physics Facility (FPF) as mentioned in this paper is a suite of experiments to probe standard model processes and search for physics beyond the standard model (BSM) beyond the acceptance of existing LHC experiments.
Abstract:
High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing LHC experiments. The proposed Forward Physics Facility (FPF), to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe standard model (SM) processes and search for physics beyond the standard model (BSM). In this report, we review the status of the civil engineering plans and the experiments to explore the diverse physics signals that can be uniquely probed in the forward region. FPF experiments will be sensitive to a broad range of BSM physics through searches for new particle scattering or decay signatures and deviations from SM expectations in high statistics analyses with TeV neutrinos in this low-background environment. High statistics neutrino detection will also provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. We report here on these physics topics, on infrastructure, detector, and simulation studies, and on future directions to realize the FPF’s physics potential.
86 citations