002801063 001__ 2801063
002801063 005__ 20241012091517.0
002801063 0248_ $$aoai:cds.cern.ch:2801063$$pcerncds:FULLTEXT$$pcerncds:CERN:FULLTEXT$$pcerncds:CERN
002801063 0247_ $$2DOI$$9arXiv$$a10.1088/1361-6633/ac9cee$$qpublication
002801063 037__ $$9arXiv$$aarXiv:2201.07805$$chep-ph
002801063 037__ $$aFERMILAB-PUB-22-057-T
002801063 035__ $$9arXiv$$aoai:arXiv.org:2201.07805
002801063 035__ $$9Inspire$$aoai:inspirehep.net:2014186$$d2024-10-11T12:58:07Z$$h2024-10-12T03:47:16Z$$mmarcxml$$ttrue$$uhttps://inspirehep.net/api/oai2d
002801063 035__ $$9Inspire$$a2014186
002801063 041__ $$aeng
002801063 100__ $$aGoudzovski, Evgueni$$uBirmingham U.$$vSchool of Physics and Astronomy, University of Birmingham, Edgbaston, B15 2TT, United Kingdom$$vEditors.
002801063 245__ $$9IOP$$aNew Physics Searches at Kaon and Hyperon Factories
002801063 269__ $$c2022-01-19
002801063 260__ $$c2023-01-06
002801063 300__ $$a68 p
002801063 500__ $$9arXiv$$a108 pages, 25 figures, 9 tables, matches the published version
002801063 520__ $$9IOP$$aRare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.
002801063 520__ $$9arXiv$$aRare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.
002801063 540__ $$3preprint$$aCC BY 4.0$$uhttp://creativecommons.org/licenses/by/4.0/
002801063 542__ $$3publication$$dIOP Publishing Ltd.$$g2022
002801063 65017 $$2SzGeCERN$$aParticle Physics - Phenomenology
002801063 690C_ $$aCERN
002801063 690C_ $$aARTICLE
002801063 700__ $$aRedigolo, Diego$$uCERN$$uINFN, Florence$$vCERN, Theory Division, CH-1211 Geneva 23, Switzerland$$vINFN Sezione di Firenze, Via G. Sansone 1, 59100 Sesto F.No, Italy$$vEditors.
002801063 700__ $$aTobioka, Kohsaku$$jORCID:0000-0003-2540-9649$$uFlorida State U.$$uKEK, Tsukuba$$vDepartment of Physics, Florida State University, Tallahassee, FL 32306, United States of America$$vHigh Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan$$vEditors.
002801063 700__ $$aZupan, Jure$$uCincinnati U.$$vDepartment of Physics, University of Cincinnati, Cincinnati, Ohio 45221, United States of America$$vEditors.
002801063 700__ $$aAlonso-Álvarez, Gonzalo$$jORCID:0000-0002-5206-1177$$uMcGill U.$$vCERN, Theory Division, CH-1211 Geneva 23, Switzerland$$vMcGill University Department of Physics & McGill Space Institute, 3600 Rue University, Montréal, QC, H3 2T8, Canada
002801063 700__ $$aAlves, Daniele S.M.$$jORCID:0000-0002-4447-6305$$uLos Alamos$$vTheoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545,United States of America
002801063 700__ $$aBansal, Saurabh$$uCincinnati U.$$vDepartment of Physics, University of Cincinnati, Cincinnati, Ohio 45221, United States of America
002801063 700__ $$aBauer, Martin$$uDurham U., ICC$$vInstitute for Particle Physics Phenomenology, Department of Physics Durham University, Durham, DH1 3LE, United Kingdom
002801063 700__ $$aBrod, Joachim$$uCincinnati U.$$vDepartment of Physics, University of Cincinnati, Cincinnati, Ohio 45221, United States of America
002801063 700__ $$aChobanova, Veronika$$uSantiago de Compostela U., IGFAE$$vIGFAE, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
002801063 700__ $$aD'Ambrosio, Giancarlo$$uINFN, Naples$$vINFN Sezione di Napoli, Complesso Universitario di Monte S. Angelo, ed. 6 via Cintia, 80126, Napoli, Italy
002801063 700__ $$aDatta, Alakabha$$uMississippi U.$$vDepartment of Physics and Astronomy, 108 Lewis Hall, University of Mississippi, Oxford, MS 38677-1848, United States of America
002801063 700__ $$aDery, Avital$$uCornell U., LEPP$$vDepartment of Physics, LEPP, Cornell University, Ithaca, NY 14853, United States of America
002801063 700__ $$aDettori, Francesco$$uCagliari U.$$vUniversità degli studi di Cagliari and INFN, Cagliari, Italy
002801063 700__ $$aDobrescu, Bogdan A.$$uFermilab$$vFermilab, Particle Theory Department, PO Box 500, Batavia, IL 60510, United States of America
002801063 700__ $$aDöbrich, Babette$$jORCID:0000-0002-6008-8601$$uCERN$$vCERN, Esplanade des Particules 1, 1211 Geneva 23, Switzerland
002801063 700__ $$aEgana-Ugrinovic, Daniel$$uPerimeter Inst. Theor. Phys.$$vPerimeter Institute for Theoretical Physics, Waterloo, ON N2J 2W9, Canada
002801063 700__ $$aElor, Gilly$$uU. Mainz, PRISMA$$vPRISMA + Cluster of Excellence & Mainz Institute for Theoretical Physics Johannes Gutenberg University, 55099 Mainz, Germany
002801063 700__ $$aEscudero, Miguel$$jORCID:0000-0002-4487-8742$$uMunich, Tech. U.$$vPhysik-Department, Technische Universität, München, James-Franck-Straße, 85748 Garching, Germany
002801063 700__ $$aFabbrichesi, Marco$$uINFN, Trieste$$vINFN Sezione di Trieste, Via Valerio 2, 34127 Trieste, Italy
002801063 700__ $$aFornal, Bartosz$$uBarry U.$$vDepartment of Chemistry and Physics, Barry University, Miami Shores, FL 33161,United States of America
002801063 700__ $$aFox, Patrick J.$$uFermilab$$vFermilab, Particle Theory Department, PO Box 500, Batavia, IL 60510, United States of America
002801063 700__ $$aGabrielli, Emidio$$uINFN, Trieste$$uTrieste U.$$uNICPB, Tallinn$$vINFN Sezione di Trieste, Via Valerio 2, 34127 Trieste, Italy$$vDepartment of Physics, University of Trieste, Strada Costiera 11-34151, Trieste, Italy$$vLaboratory of High Energy and Computational Physics, NICPB, Rävala pst 10, 10143 Tallinn, Estonia
002801063 700__ $$aGeng, Li-Sheng$$jORCID:0000-0002-5626-0704$$uBeihang U.$$vSchool of Physics, Beihang University, Beijing 102206, People’s Republic of China
002801063 700__ $$aGligorov, Vladimir V.$$uParis U., VI-VII$$vLPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris, France
002801063 700__ $$aGorbahn, Martin$$uLiverpool U.$$vTheoretical Physics Division, Department of Mathematical Sciences, University of Liverpool, Liverpool L69 3BX, United Kingdom
002801063 700__ $$aGori, Stefania$$jORCID:0000-0003-1073-6591$$uUC, Santa Cruz, Inst. Part. Phys.$$vSanta Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States of America
002801063 700__ $$aGrinstein, Benjamín$$uUC, San Diego$$vDepartment of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, United States of America
002801063 700__ $$aGrossman, Yuval$$uCornell U., LEPP$$vDepartment of Physics, LEPP, Cornell University, Ithaca, NY 14853, United States of America
002801063 700__ $$aGuadagnoli, Diego$$uAnnecy, LAPTH$$vLAPTh, CNRS et Université Savoie Mont-Blanc, Annecy, France
002801063 700__ $$aHomiller, Samuel$$jORCID:0000-0002-0063-6856$$uHarvard U.$$vDepartment of Physics, Harvard University, Cambridge, MA 02138, United States of America
002801063 700__ $$aHostert, Matheus$$uPerimeter Inst. Theor. Phys.$$uMinnesota U.$$uU. Minnesota, Minneapolis (main)$$vPerimeter Institute for Theoretical Physics, Waterloo, ON N2J 2W9, Canada$$vSchool of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455,United States of America$$vWilliam I. Fine Theoretical Physics Institute, School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States of America
002801063 700__ $$aKelly, Kevin J.$$uCERN$$uFermilab$$vCERN, Theory Division, CH-1211 Geneva 23, Switzerland$$vFermilab, Particle Theory Department, PO Box 500, Batavia, IL 60510, United States of America
002801063 700__ $$aKitahara, Teppei$$jORCID:0000-0002-4847-9511$$uNagoya U. (main)$$vInstitute for Advanced Research & Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602, Japan
002801063 700__ $$aKnapen, Simon$$uCERN$$uUC, Berkeley$$uLBNL, Berkeley$$vCERN, Theory Division, CH-1211 Geneva 23, Switzerland$$vBerkeley Center for Theoretical Physics, Department of Physics, University of California, Berkeley, CA 94720, United States of America$$vTheoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,United States of America
002801063 700__ $$aKrnjaic, Gordan$$uFermilab$$uChicago U.$$uChicago U., KICP$$vFermi National Accelerator Laboratory, Batavia, IL, United States of America$$vUniversity of Chicago, Department of Astronomy and Astrophysics, Chicago, IL,United States of America$$vKavli Institute for Cosmological Physics, University of Chicago, Chicago, IL,United States of America
002801063 700__ $$aKupsc, Andrzej$$jORCID:0000-0003-4937-2270$$uUppsala U.$$uNCBJ, Warsaw$$vDepartment of Physics and Astronomy, Uppsala University, Uppsala, Sweden$$vNational Centre for Nuclear Research, Warsaw, Poland
002801063 700__ $$aKvedaraitė, Sandra$$uCincinnati U.$$vDepartment of Physics, University of Cincinnati, Cincinnati, Ohio 45221, United States of America
002801063 700__ $$aLanfranchi, Gaia$$jORCID:0000-0002-9467-8001$$uFrascati$$vINFN Laboratori Nazionali di Frascati, 00044 Frascati RM, Italy
002801063 700__ $$aMarfatia, Danny$$uHawaii U.$$vDepartment of Physics & Astronomy, University of Hawaii at Manoa, 2505 Correa Rd., Honolulu, HI 96822, United States of America
002801063 700__ $$aMartin Camalich, Jorge$$uIAC, La Laguna$$uLaguna U., Tenerife$$vInstituto de Astrofísica de Canarias, C/ Vía Láctea, s/n E38205-La Laguna, Tenerife, Spain$$vUniversidad de La Laguna, Departamento de Astrofísica-La Laguna, Tenerife, Spain
002801063 700__ $$aMartínez Santos, Diego$$uSantiago de Compostela U., IGFAE$$vIGFAE, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
002801063 700__ $$aMassri, Karim$$uCERN$$vCERN, Esplanade des Particules 1, 1211 Geneva 23, Switzerland
002801063 700__ $$aMeade, Patrick$$uStony Brook U.$$vC. N. Yang Institute for Theoretical Physics, Stony Brook University, Stony Brook, NY 11794,United States of America
002801063 700__ $$aMoulson, Matthew$$jORCID:0000-0002-3951-4389$$uFrascati$$vINFN Laboratori Nazionali di Frascati, 00044 Frascati RM, Italy
002801063 700__ $$aNanjo, Hajime$$uOsaka U.$$vDepartment of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
002801063 700__ $$aNeubert, Matthias$$uU. Mainz, PRISMA$$vPRISMA + Cluster of Excellence & Mainz Institute for Theoretical Physics Johannes Gutenberg University, 55099 Mainz, Germany
002801063 700__ $$aPospelov, Maxim$$uMinnesota U.$$uU. Minnesota, Minneapolis (main)$$vSchool of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455,United States of America$$vWilliam I. Fine Theoretical Physics Institute, School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States of America
002801063 700__ $$aRenner, Sophie$$uCERN$$vCERN, Theory Division, CH-1211 Geneva 23, Switzerland
002801063 700__ $$aSchacht, Stefan$$jORCID:0000-0003-2181-8779$$uManchester U.$$vDepartment of Physics and Astronomy, University of Manchester, Manchester, M13 9PL,United Kingdom
002801063 700__ $$aSchnubel, Marvin$$uU. Mainz, PRISMA$$vPRISMA + Cluster of Excellence & Mainz Institute for Theoretical Physics Johannes Gutenberg University, 55099 Mainz, Germany
002801063 700__ $$aShi, Rui-Xiang$$uParis U., VI-VII$$uBeihang U.$$vSchool of Physics, Beihang University, Beijing 102206, People’s Republic of China$$vSchool of Space and Environment, Beihang University, Beijing 102206, People’s Republic of China
002801063 700__ $$aShuve, Brian$$uHarvey Mudd Coll.$$vHarvey Mudd College, 301 Platt Blvd., Claremont, CA 91711, United States of America
002801063 700__ $$aSpadaro, Tommaso$$uFrascati$$vINFN Laboratori Nazionali di Frascati, 00044 Frascati RM, Italy
002801063 700__ $$aSoreq, Yotam$$uTechnion$$vPhysics Department, Technion, Israel Institute of Technology, Haifa 3200003, Israel
002801063 700__ $$aStamou, Emmanuel$$uDortmund U.$$vFakultät für Physik, TU Dortmund, D-44221 Dortmund, Germany
002801063 700__ $$aSumensari, Olcyr$$uIJCLab, Orsay$$vUniversité Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France
002801063 700__ $$aTammaro, Michele$$uStefan Inst., Ljubljana$$vJožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
002801063 700__ $$aTerol-Calvo, Jorge$$uIAC, La Laguna$$uLaguna U., Tenerife$$vInstituto de Astrofísica de Canarias, C/ Vía Láctea, s/n E38205-La Laguna, Tenerife, Spain$$vUniversidad de La Laguna, Departamento de Astrofísica-La Laguna, Tenerife, Spain
002801063 700__ $$aThamm, Andrea$$uMelbourne U.$$vSchool of Physics, The University of Melbourne, Victoria 3010, Australia
002801063 700__ $$aTung, Yu-Chen$$uTaiwan, Natl. Taiwan U.$$vNational Taiwan University, No. 1, Section 4, Roosevelt Rd, Da’an District, Taipei City, 10617, Taiwan
002801063 700__ $$aWang, Dayong$$uPeking U., SKLNPT$$vSchool of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, People’s Republic of China
002801063 700__ $$aYamamoto, Kei$$uHiroshima U. (main)$$vCore of Research for the Energetic Universe, Hiroshima University, Higashi-Hiroshima 739-8526,Japan
002801063 700__ $$aZiegler, Robert$$mktobioka@fsu.edu$$uKarlsruhe U., TTP$$vInstitut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology, Karlsruhe, Germany$$vEditors.
002801063 773__ $$c016201$$n1$$pRep. Prog. Phys.$$v86$$y2023
002801063 8564_ $$uhttps://lss.fnal.gov/archive/2022/pub/fermilab-pub-22-057-t.pdf$$yFermilab Accepted Manuscript
002801063 8564_ $$82458474$$s10022639$$uhttp://cds.cern.ch/record/2801063/files/20769f2ea1acd21399f56329734230a9.pdf
002801063 8564_ $$82349683$$s19084$$uhttp://cds.cern.ch/record/2801063/files/Fig4b.png$$y00004 \small Constraints on the axion decay constant $f_a$ for the flavor anarchic (left) and minimal flavor violation (right) benchmarks. The constraints from NA62 are showed as colored regions, cf. Fig.~\ref{fig:BRKpiinv}. The SN1987A constraints (grey region) are taken from Ref.~\cite{Lee:2018lcj} for SN cooling through nucleon bremsstrahlung $NN \to NN +{\rm inv}$, and from Ref.~\cite{MartinCamalich:2020dfe} for cooling via hyperon decays $\Lambda\to n +{\rm inv}$. The $K-\bar K$ mixing constraints assume that the dimension-6 UV contributions are small. Also shown in the right panel are the contour lines below which the ALP is no longer long-lived ($c \tau_a < 1$~m) and above which its lifetime is stringently constrained by cosmology ($\tau_a > 1$~s).
002801063 8564_ $$82349684$$s17165$$uhttp://cds.cern.ch/record/2801063/files/Fig4a.png$$y00003 \small Constraints on the axion decay constant $f_a$ for the flavor anarchic (left) and minimal flavor violation (right) benchmarks. The constraints from NA62 are showed as colored regions, cf. Fig.~\ref{fig:BRKpiinv}. The SN1987A constraints (grey region) are taken from Ref.~\cite{Lee:2018lcj} for SN cooling through nucleon bremsstrahlung $NN \to NN +{\rm inv}$, and from Ref.~\cite{MartinCamalich:2020dfe} for cooling via hyperon decays $\Lambda\to n +{\rm inv}$. The $K-\bar K$ mixing constraints assume that the dimension-6 UV contributions are small. Also shown in the right panel are the contour lines below which the ALP is no longer long-lived ($c \tau_a < 1$~m) and above which its lifetime is stringently constrained by cosmology ($\tau_a > 1$~s).
002801063 8564_ $$82349685$$s94233$$uhttp://cds.cern.ch/record/2801063/files/plot-alp1.png$$y00024 \small Constraints on the plane $C_{e\mu}^A/f_a$ vs.~$C_{sd}^{V(A)}/f_a$ derived from $\mathcal{B}(K^+\to\pi^+ \mu^+ e^-)<1.3\times 10^{-11}$~\cite{Ambrose:1998us} (orange) and $\mathcal{B}(K_L\to \mu^\mp e^\pm)<4.7\times 10^{-12}$~\cite{Sher:2005sp} (blue) for three values of ALP mass: (i) $m_a=20$~MeV (left), (ii) $m_a=200$~MeV (center) and $m_a=2$~GeV. For simplicity, we assume that $C_{sd}^{V}=C_{sd}^{A}$, as predicted by a left-handed operator. We superimpose in the same plot constraints derived from $\mu\to e+\mathrm{inv}$~\cite{Calibbi:2020jvd} (gray), $\Delta m_K$~\cite{MartinCamalich:2020dfe} (red) and muonium-antimuonium oscillation~\cite{Masiero:2020vxk,Endo:2020mev} (green).
002801063 8564_ $$82349686$$s17805$$uhttp://cds.cern.ch/record/2801063/files/kaon_multi_lepton_bosons.png$$y00020 \small Kaon decay diagrams in minimal and extended $U(1)_d$ dark sectors, as well as in the MeV QCD axion model. The subsequent prompt decays of $A'=\gamma_d$ and $\varphi=h_d$ lead to observable four-lepton signatures.
002801063 8564_ $$82349687$$s21025$$uhttp://cds.cern.ch/record/2801063/files/ALPtargetKplus_v4.png$$y00011 \small Target branching ratios for $K^+\to\pi^+a(\to \gamma\gamma)$ (left) and $K_L\to \pi^0 a(\to \gamma\gamma)$ (right) decay searches for four different benchmark scenarios: the ALP coupling only to gluons (scenario (a), black dashed line), only to $SU(2)_L$ gauge bosons ((b), blue dashed line), to up quarks ((c), light blue dashed line) and to down quarks ((d), orange dashed line). In each case the regions below the dashed lines are excluded by the beam-dump constraints. The shaded regions are excluded by prompt searches, as indicated.
002801063 8564_ $$82349688$$s23695$$uhttp://cds.cern.ch/record/2801063/files/kaon_multi_lepton_hnls.png$$y00021 Kaon decays to heavy neutral leptons with multi-lepton final states. All dark sector particles, $N$, $A'=\gamma_d$, and $\varphi=h_d$, are produced on shell. Experimental reconstruction of the dark sector masses is possible for the first two diagrams. The flavor indices $\alpha$ and $\beta$ can be $e$ or $\mu$, depending on the process.
002801063 8564_ $$82349689$$s42865$$uhttp://cds.cern.ch/record/2801063/files/HNLe_WhitePaper.png$$y00017 \small Experimental constraints on electron-coupled (left) and muon-coupled (right) heavy neutral leptons as functions of their mass and the mixing $|U_{\ell N}|^2$, along with the na\"{i}ve seesaw target (grey bands).
002801063 8564_ $$82349690$$s29808$$uhttp://cds.cern.ch/record/2801063/files/BR_Kplus_MeV_ALP_fa1TeV.png$$y00001 \small Branching ratios of the $K^+\to\pi^+a$ (left) and $K_L\to\pi^0a$ (right) decays as functions of the ALP mass, taking only a single coupling in the ALP Lagrangian~\eqref{eq:alpgauge}, \eqref{eq:ALP-f} to be nonzero as shown by the labels, and setting $f_a=1$~TeV and $\Lambda_{\rm UV}= 4\pi f_a$. For a different value of the ALP decay constant, the branching ratios should be rescaled by $1/f_a^2$.
002801063 8564_ $$82349691$$s36802$$uhttp://cds.cern.ch/record/2801063/files/downplotrenner.png$$y00010 \small Bounds on flavor-diagonal pseudoscalar quark couplings of ALP to the first generation quarks: coupling to up quarks (left) and down quarks (right). In each case, it is assumed that only the relevant coupling is nonzero in the EFT Lagrangian. The coupling to photons is induced at loop level through Eq.~\eqref{eq:cgamgameff}, allowing the ALP to decay to two photons. In both plots, the ALP has proper lifetime longer than a second in the parameter space region below the dashed line, and is therefore disfavoured by Big Bang Nucleosynthesis.
002801063 8564_ $$82349692$$s44779$$uhttp://cds.cern.ch/record/2801063/files/Fig6.png$$y00006 \small Constraints on the QCD axion in the $m_a(f_a)$--$g_{a \gamma \gamma}$ plane. Shown in gray are the usual constraints from existing and planned halo- and helioscopes and from HB star cooling, overlaid is the standard QCD axion band in yellow. In addition, we show the constraints on $m_a/f_a$ for various couplings of order unity; displayed in blue are the HB/CAST bounds~\cite{CAST:2017uph, Ayala:2014pea} for $N_1 = N_2 = 0$ (i.e. the ``hadronic axion'' which couples to photons through its mixing with $\pi^0$), the bounds from star cooling via nucleon bremsstrahlung in SN1987A for $C_N =1$ \cite{Carenza:2019pxu}, and via electron bremsstrahlung in white dwarfs (WD) for $C^A_{ee} =1$ \cite{MillerBertolami:2014rka}. Red solid (dashed) lines show the present (future) constraints from NA62 for $C^V_{sd} =1$. In orange we indicate the values of $m_a$ (and $f_a$) for which the QCD axion can fully account for the observed dark matter abundance, depending on whether the PQ symmetry is broken before or after inflation (taken from Ref.~\cite{Gorghetto:2020qws}).
002801063 8564_ $$82349693$$s42540$$uhttp://cds.cern.ch/record/2801063/files/HeavyZp.png$$y00027 \small Constraints on $Z'$ flavor-violating couplings to quarks, $g_{sd}$, and leptons, $g_{e\mu}$. Orange and blue lines represent the bounds from current limits on ${\cal B}(K^+\to\pi^+\mu^-e^+)$ and ${\cal B}(K_L\to\mu^\pm e^\mp)$, respectively (Section~\ref{sec:exp:lfv}). Red and green regions show the exclusions from $K-\bar K$ and $M-\bar M$ mixing, respectively. The dark grey region in the central plot shows the range of $g_{e\mu}$ values that could include displaced $Z'$ vertex decays.
002801063 8564_ $$82349694$$s49518$$uhttp://cds.cern.ch/record/2801063/files/gluonplotrenner.png$$y00007 \small Left: Bounds on the ALP coupling only to gluons ($N_3(\Lambda_{\rm UV})\ne 0$ only) scenario. The coupling of ALP to photons is induced at one loop, cf. Eq.~\eqref{eq:cgamgameff}, allowing for the $a\to \gamma\gamma$ decays. {The Babar bound was derived assuming $\Lambda_{\rm UV}=1$~TeV.} Right: Bounds on the ALP coupling to only $SU(2)_L$ gauge bosons ($N_2(\Lambda_{\rm UV})\ne 0$ only) scenario~\cite{Gori:2020xvq}. In this case $a\to \gamma\gamma$ is generated already at tree level. In the parameter space region below the dashed line in both plots, the ALP has proper lifetime longer than a second, and is therefore disfavoured by Big Bang Nucleosynthesis considerations. The red dashed lines on the right-hand plot trace the points at which the ALP has an average lab frame decay length of 100~m and 10~m at NA62. These illustrate why the $K^+\to\pi^+X$ bound where $X$ is invisible in the laboratory does not extend to larger couplings, since the ALP becomes too prompt for the search to be sensitive.
002801063 8564_ $$82349695$$s53638$$uhttp://cds.cern.ch/record/2801063/files/HNLmu_WhitePaper.png$$y00018 \small Experimental constraints on electron-coupled (left) and muon-coupled (right) heavy neutral leptons as functions of their mass and the mixing $|U_{\ell N}|^2$, along with the na\"{i}ve seesaw target (grey bands).
002801063 8564_ $$82349696$$s147015$$uhttp://cds.cern.ch/record/2801063/files/dark_HNLs_1.png$$y00022 The mixing of the HNLs with muon neutrinos as a function of the HNL mass (left) and the dark photon mass (right) for a given choice of dark sector parameters~\cite{Ballett:2019pyw}. We show the NA62 sensitivity to $K^+\to \mu^+ \nu e^+e^-$ as well as $K^+\to \mu^+ \nu \mu^+\mu^-$ decays arising from CC kaon decays followed by prompt HNL decays $N\to \nu (A^\prime\to\ell^+\ell^-)$.
002801063 8564_ $$82349697$$s137116$$uhttp://cds.cern.ch/record/2801063/files/dark_HNLs_2.png$$y00023 The mixing of the HNLs with muon neutrinos as a function of the HNL mass (left) and the dark photon mass (right) for a given choice of dark sector parameters~\cite{Ballett:2019pyw}. We show the NA62 sensitivity to $K^+\to \mu^+ \nu e^+e^-$ as well as $K^+\to \mu^+ \nu \mu^+\mu^-$ decays arising from CC kaon decays followed by prompt HNL decays $N\to \nu (A^\prime\to\ell^+\ell^-)$.
002801063 8564_ $$82349698$$s91644$$uhttp://cds.cern.ch/record/2801063/files/plot-alp3.png$$y00025 \small Constraints on the plane $C_{e\mu}^A/f_a$ vs.~$C_{sd}^{V(A)}/f_a$ derived from $\mathcal{B}(K^+\to\pi^+ \mu^+ e^-)<1.3\times 10^{-11}$~\cite{Ambrose:1998us} (orange) and $\mathcal{B}(K_L\to \mu^\mp e^\pm)<4.7\times 10^{-12}$~\cite{Sher:2005sp} (blue) for three values of ALP mass: (i) $m_a=20$~MeV (left), (ii) $m_a=200$~MeV (center) and $m_a=2$~GeV. For simplicity, we assume that $C_{sd}^{V}=C_{sd}^{A}$, as predicted by a left-handed operator. We superimpose in the same plot constraints derived from $\mu\to e+\mathrm{inv}$~\cite{Calibbi:2020jvd} (gray), $\Delta m_K$~\cite{MartinCamalich:2020dfe} (red) and muonium-antimuonium oscillation~\cite{Masiero:2020vxk,Endo:2020mev} (green).
002801063 8564_ $$82349699$$s17497$$uhttp://cds.cern.ch/record/2801063/files/ALPtargetKL_v4.png$$y00012 \small Target branching ratios for $K^+\to\pi^+a(\to \gamma\gamma)$ (left) and $K_L\to \pi^0 a(\to \gamma\gamma)$ (right) decay searches for four different benchmark scenarios: the ALP coupling only to gluons (scenario (a), black dashed line), only to $SU(2)_L$ gauge bosons ((b), blue dashed line), to up quarks ((c), light blue dashed line) and to down quarks ((d), orange dashed line). In each case the regions below the dashed lines are excluded by the beam-dump constraints. The shaded regions are excluded by prompt searches, as indicated.
002801063 8564_ $$82349700$$s11273579$$uhttp://cds.cern.ch/record/2801063/files/2201.07805.pdf$$yFulltext
002801063 8564_ $$82349701$$s47178$$uhttp://cds.cern.ch/record/2801063/files/LightZp.png$$y00026 \small Constraints on $Z'$ flavor-violating couplings to quarks, $g_{sd}$, and leptons, $g_{e\mu}$. Orange and blue lines represent the bounds from current limits on ${\cal B}(K^+\to\pi^+\mu^-e^+)$ and ${\cal B}(K_L\to\mu^\pm e^\mp)$, respectively (Section~\ref{sec:exp:lfv}). Red and green regions show the exclusions from $K-\bar K$ and $M-\bar M$ mixing, respectively. The dark grey region in the central plot shows the range of $g_{e\mu}$ values that could include displaced $Z'$ vertex decays.
002801063 8564_ $$82349702$$s39428$$uhttp://cds.cern.ch/record/2801063/files/wwplotrenner.png$$y00008 \small Left: Bounds on the ALP coupling only to gluons ($N_3(\Lambda_{\rm UV})\ne 0$ only) scenario. The coupling of ALP to photons is induced at one loop, cf. Eq.~\eqref{eq:cgamgameff}, allowing for the $a\to \gamma\gamma$ decays. {The Babar bound was derived assuming $\Lambda_{\rm UV}=1$~TeV.} Right: Bounds on the ALP coupling to only $SU(2)_L$ gauge bosons ($N_2(\Lambda_{\rm UV})\ne 0$ only) scenario~\cite{Gori:2020xvq}. In this case $a\to \gamma\gamma$ is generated already at tree level. In the parameter space region below the dashed line in both plots, the ALP has proper lifetime longer than a second, and is therefore disfavoured by Big Bang Nucleosynthesis considerations. The red dashed lines on the right-hand plot trace the points at which the ALP has an average lab frame decay length of 100~m and 10~m at NA62. These illustrate why the $K^+\to\pi^+X$ bound where $X$ is invisible in the laboratory does not extend to larger couplings, since the ALP becomes too prompt for the search to be sensitive.
002801063 8564_ $$82349703$$s34361$$uhttp://cds.cern.ch/record/2801063/files/wwplotllrenner.png$$y00014 \small Left: Bounds on the coupling of an ALP to gluons for a scenario in which only the couplings to gluons and to leptons are nonzero in the Lagrangian. The coupling to leptons is set by $C^A_{ll}=N_3$ and is lepton universal. The coupling to photons is induced at loop level through equation~\eqref{eq:cgamgameff}, allowing the ALP to decay to two photons. Right: Bounds on the coupling of an ALP to $SU(2)_L$ gauge bosons for a scenario in which only this coupling and the coupling to leptons are nonzero in the Lagrangian~\cite{Gori:2020xvq}. The coupling to leptons is set by $C^A_{ll}=N_2$ and is lepton universal. The ALP decay to photons occurs at tree level through the $N_2$ coupling.
002801063 8564_ $$82349704$$s8407$$uhttp://cds.cern.ch/record/2801063/files/DPMasslessLimits.png$$y00019 \small Experimental limits on the parameter space of the massless dark photon, with $\Lambda$ the new physics scale and $\mathbb{D}$ the effective dipole coupling (adapted from Refs.~\cite{Camalich:2020wac}, \cite{Fabbrichesi:2020wbt}).
002801063 8564_ $$82349705$$s9633$$uhttp://cds.cern.ch/record/2801063/files/ALPtargetKLee_v1.png$$y00016 \small Target branching ratios for $K^+\to\pi^+a(\to e^+e^-)$ (left) and $K_L\to \pi^0 a(\to e^+e^-)$ (right) decay searches for two different benchmark scenarios: the ALP couplings to gauge bosons, either $N_2$ or $N_3$, where the ALP also couples (diagonally and flavour-universally) to leptons. In each case, the regions below the dashed lines are excluded by the beam-dump searches. The shaded regions are excluded by prompt decay searches, as indicated. Due to the displacement of the ALP decay, there is sometimes a discrepancy between the bound assuming prompt decay and the effective bound on each scenario. The dotted lines show the effective bounds for the $N_3=C_{ll}^A$ scenario of $K^+\to\pi^+ e^+e^-$, and the $N_2=C_{ll}^A$ scenario of $K_L\to\pi^0 e^+e^-$.
002801063 8564_ $$82349706$$s87386$$uhttp://cds.cern.ch/record/2801063/files/higgs_portal_summary_plot.png$$y00000 \small Constraints on the Higgs portal scalar in the mixing angle vs mass plane. The NA62 and E949 limits extend down to $m_\varphi=0$ with almost no deterioration.
002801063 8564_ $$82349707$$s16740$$uhttp://cds.cern.ch/record/2801063/files/ALPtargetKplusee_v1.png$$y00015 \small Target branching ratios for $K^+\to\pi^+a(\to e^+e^-)$ (left) and $K_L\to \pi^0 a(\to e^+e^-)$ (right) decay searches for two different benchmark scenarios: the ALP couplings to gauge bosons, either $N_2$ or $N_3$, where the ALP also couples (diagonally and flavour-universally) to leptons. In each case, the regions below the dashed lines are excluded by the beam-dump searches. The shaded regions are excluded by prompt decay searches, as indicated. Due to the displacement of the ALP decay, there is sometimes a discrepancy between the bound assuming prompt decay and the effective bound on each scenario. The dotted lines show the effective bounds for the $N_3=C_{ll}^A$ scenario of $K^+\to\pi^+ e^+e^-$, and the $N_2=C_{ll}^A$ scenario of $K_L\to\pi^0 e^+e^-$.
002801063 8564_ $$82349708$$s35652$$uhttp://cds.cern.ch/record/2801063/files/upplotrenner.png$$y00009 \small Bounds on flavor-diagonal pseudoscalar quark couplings of ALP to the first generation quarks: coupling to up quarks (left) and down quarks (right). In each case, it is assumed that only the relevant coupling is nonzero in the EFT Lagrangian. The coupling to photons is induced at loop level through Eq.~\eqref{eq:cgamgameff}, allowing the ALP to decay to two photons. In both plots, the ALP has proper lifetime longer than a second in the parameter space region below the dashed line, and is therefore disfavoured by Big Bang Nucleosynthesis.
002801063 8564_ $$82349709$$s17991$$uhttp://cds.cern.ch/record/2801063/files/Fig5.png$$y00005 \small Laboratory and astrophysiccal constraints on the inverse axion couplings for the case of a massless ALP, $m_a = 0$. These apply unchanged also to the standard QCD axion. The SN1987A bounds are taken from Ref.~\cite{MartinCamalich:2020dfe} for the case of $C^V_{sd}$ and $C^A_{sd}$ (cooling via hyperon decays) and from Ref.~\cite{Carenza:2019pxu} for the case of $C_{qq}$ (cooling via nucleon bremsstrahlung). In contrast to the bounds from hyperon decays the nucleon bremsstrahlung has a trapping regime for smaller values of $f_a$. These values are excluded by Kamiokande constraints~\cite{Engel:1990zd}, leaving an open parameter space only for very small values of $f_a$, outside the plotted range. The laboratory bounds for $C^V_{sd}$ and $C_{qq}$ ($K \to \pi$ decays) are discussed in the main text, while the bounds on $C^A_{sd}$ ($K \to\pi\pi$ decays)~\cite{MartinCamalich:2020dfe} are from the ISTRA+ experiment~\cite{Tchikilev:2003ai}.
002801063 8564_ $$82349710$$s16929$$uhttp://cds.cern.ch/record/2801063/files/Fig3.png$$y00002 \small Constraints on ${\cal B}(K^+\to\pi^+X)$ with the $X$ particle decaying invisibly or escaping the detector as a function of $X$ mass up to the kinematic endpoint (vertical dotted line). Red regions are excluded by the NA62 search for $K^+\to\pi^+X$~\cite{NA62:2021zjw}, the blue region by $\pi^0\to{\rm inv}$~\cite{NA62:2020pwi}, and grey regions by the BNL E949 experiment~\cite{Artamonov:2009sz}.
002801063 8564_ $$82349711$$s45561$$uhttp://cds.cern.ch/record/2801063/files/gluonplotllrenner.png$$y00013 \small Left: Bounds on the coupling of an ALP to gluons for a scenario in which only the couplings to gluons and to leptons are nonzero in the Lagrangian. The coupling to leptons is set by $C^A_{ll}=N_3$ and is lepton universal. The coupling to photons is induced at loop level through equation~\eqref{eq:cgamgameff}, allowing the ALP to decay to two photons. Right: Bounds on the coupling of an ALP to $SU(2)_L$ gauge bosons for a scenario in which only this coupling and the coupling to leptons are nonzero in the Lagrangian~\cite{Gori:2020xvq}. The coupling to leptons is set by $C^A_{ll}=N_2$ and is lepton universal. The ALP decay to photons occurs at tree level through the $N_2$ coupling.
002801063 8564_ $$82432058$$s8648962$$uhttp://cds.cern.ch/record/2801063/files/jt.pdf$$yFulltext
002801063 8564_ $$82456363$$s21420$$uhttp://cds.cern.ch/record/2801063/files/ALPtargetKplus_v5.png$$y00011 \small Target branching ratios for $K^+\to\pi^+a(\to \gamma\gamma)$ (left) and $K_L\to \pi^0 a(\to \gamma\gamma)$ (right) decay searches for four different benchmark scenarios: the ALP coupling only to gluons (scenario (a), black dashed line), only to $SU(2)_L$ gauge bosons ((b), blue dashed line), to up quarks ((c), light blue dashed line) and to down quarks ((d), orange dashed line). In each case the regions below the dashed lines are excluded by the beam-dump constraints. The shaded regions are excluded by prompt searches, as indicated.
002801063 8564_ $$82456364$$s18684$$uhttp://cds.cern.ch/record/2801063/files/ALPtargetKL_v5.png$$y00012 \small Target branching ratios for $K^+\to\pi^+a(\to \gamma\gamma)$ (left) and $K_L\to \pi^0 a(\to \gamma\gamma)$ (right) decay searches for four different benchmark scenarios: the ALP coupling only to gluons (scenario (a), black dashed line), only to $SU(2)_L$ gauge bosons ((b), blue dashed line), to up quarks ((c), light blue dashed line) and to down quarks ((d), orange dashed line). In each case the regions below the dashed lines are excluded by the beam-dump constraints. The shaded regions are excluded by prompt searches, as indicated.
002801063 8564_ $$82456365$$s9680$$uhttp://cds.cern.ch/record/2801063/files/ALPtargetKLee_v2.png$$y00016 \small Target branching ratios for $K^+\to\pi^+a(\to e^+e^-)$ (left) and $K_L\to \pi^0 a(\to e^+e^-)$ (right) decay searches for two different benchmark scenarios: the ALP couplings to gauge bosons, either $N_2$ or $N_3$, where the ALP also couples (diagonally and flavour-universally) to leptons. In each case, the regions below the dashed lines are excluded by the beam-dump searches. The shaded regions are excluded by prompt decay searches, as indicated. Due to the displacement of the ALP decay, there is sometimes a discrepancy between the bound assuming prompt decay and the effective bound on each scenario. The dotted lines show the effective bounds for the $N_3=C_{ll}^A$ scenario of $K^+\to\pi^+ e^+e^-$, and the $N_2=C_{ll}^A$ scenario of $K_L\to\pi^0 e^+e^-$.
002801063 8564_ $$82456366$$s10041$$uhttp://cds.cern.ch/record/2801063/files/ALPtargetKplusee_v2.png$$y00015 \small Target branching ratios for $K^+\to\pi^+a(\to e^+e^-)$ (left) and $K_L\to \pi^0 a(\to e^+e^-)$ (right) decay searches for two different benchmark scenarios: the ALP couplings to gauge bosons, either $N_2$ or $N_3$, where the ALP also couples (diagonally and flavour-universally) to leptons. In each case, the regions below the dashed lines are excluded by the beam-dump searches. The shaded regions are excluded by prompt decay searches, as indicated. Due to the displacement of the ALP decay, there is sometimes a discrepancy between the bound assuming prompt decay and the effective bound on each scenario. The dotted lines show the effective bounds for the $N_3=C_{ll}^A$ scenario of $K^+\to\pi^+ e^+e^-$, and the $N_2=C_{ll}^A$ scenario of $K_L\to\pi^0 e^+e^-$.
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