Leptophilic dark matter from gauged lepton number: Phenomenology and gravitational wave signatures

New gauge symmetries often appear in theories beyond the Standard Model. Here we study a model where lepton number is promoted to a gauge symmetry. Anomaly cancellation requires the introduction of additional leptons, the lightest of which is a natural leptophilic dark matter candidate. We perform a comprehensive study of both collider and dark matter phenomenology. Furthermore we find that the model exhibits a first order lepton number breaking phase transition in large regions of parameter space. The corresponding gravitational wave signal is computed, and its detectability at LISA and other future GW detectors assessed. Finally we comment on the complementarity of dark matter, collider and gravitational wave observables, and on the potential reach of future colliders.Comment: 36 pages + appendix, 24 figures. Version accepted for publication in JHE

Probing new physics through entanglement in diboson production

Pair production of heavy vector bosons is a key process at colliders: it allows to test our understanding of the Standard Model and to explore the existence of new physics through precision measurements of production rates and differential distributions. New physics effects can be subtle and often require observables specifically designed for their detection. In this study, we focus on quantum information observables that characterise the spin states of the final diboson system. We analyse concurrence bounds, purity, and Bell inequalities for a bipartite qutrit system representing two massive gauge bosons. Our findings show that quantum spin observables can serve as complementary probes for heavy new physics as parametrised by higher dimensional operators in the Standard Model effective field theory. In particular, we find that these observables offer increased sensitivity to operators whose contributions do not interfere with the Standard Model amplitudes at the level of differential cross sections.Comment: 42 pages, 18 figures; v2: added ancillary file

Quantum SMEFT tomography: top quark pair production at the LHC

Quantum information observables, such as entanglement measures, provide a powerful way to characterize the properties of quantum states. We propose to use them to probe the structure of fundamental interactions and to search for new physics at high energy. Inspired by recent proposals to measure entanglement of top quark pairs produced at the LHC, we examine how higher-dimensional operators in the framework of the SMEFT modify the Standard Model expectations. We explore two regions of interest in the phase space where the Standard Model produces maximally entangled states: at threshold and in the high-energy limit. We unveil a non-trivial pattern of effects, which depend on the initial state partons, $q\bar q$ or $gg$, on whether only linear or up to quadratic SMEFT contributions are included, and on the phase space region. In general, we find that higher-dimensional effects lower the entanglement predicted in the Standard Model.Comment: 8 pages, 5 figures + appendix; v2: minor changes, published versio

Discovering the h→Zγh\to Z \gamma Decay in ttˉt \bar t Associated Production

We explore the prospects to discover the $h \to Z \gamma$ decay in $t\bar t$-associated production, featuring a signal-to-background ratio of ${\cal O}(1)$. Performing a detailed analysis of the semi-leptonic $t \bar t$-decay channel, we demonstrate that the production mode could lead to a $\sim5\,\sigma$ discovery at the high-luminosity LHC, while the effective $h Z \gamma$ coupling could be extracted with a $\sim15\,\%$ accuracy. Extending the analysis to potential future $pp$ colliders with 27 TeV and 100 TeV center-of-mass energies, we also show that the latter would allow precision measurements at the few percent level, rendering possible precise extractions of the spin and CP properties of the Higgs boson.Comment: 7 pages, 4 figures, updated version matches the one published is Phys. Rev.

Dark, Cold, and Noisy: Constraining Secluded Hidden Sectors with Gravitational Waves

We explore gravitational wave signals arising from first-order phase transitions occurring in a secluded hidden sector, allowing for the possibility that the hidden sector may have a different temperature than the Standard Model sector. We present the sensitivity to such scenarios for both current and future gravitational wave detectors in a model-independent fashion. Since secluded hidden sectors are of particular interest for dark matter models at the MeV scale or below, we pay special attention to the reach of pulsar timing arrays. Cosmological constraints on light degrees of freedom restrict the number of sub-MeV particles in a hidden sector, as well as the hidden sector temperature. Nevertheless, we find that observable first-order phase transitions can occur. To illustrate our results, we consider two minimal benchmark models: a model with two gauge singlet scalars and a model with a spontaneously broken $U(1)$ gauge symmetry in the hidden sector.Comment: 37 pages, 12 figures. Noise and PLI sensitivity curves are included in the source director

Cosmology with the Laser Interferometer Space Antenna

254 pags:, 44 figs.The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universe.This work is partly supported by: A.G. Leventis Foundation; Academy of Finland Grants 328958 and 345070; Alexander S. Onassis Foundation, Scholarship ID: FZO 059-1/2018-2019; Amaldi Research Center funded by the MIUR program “Dipartimento di Eccellenza” (CUP: B81I18001170001); ASI Grants No. 2016-24-H.0 and No. 2016-24-H.1-2018; Atracción de Talento Grant 2019-T1/TIC-15784; Atracción de Talento contract no. 2019-T1/TIC-13177 granted by the Comunidad de Madrid; Ayuda ‘Beatriz Galindo Senior’ by the Spanish ‘Ministerio de Universidades’, Grant BG20/00228; Basque Government Grant (IT-979-16); Belgian Francqui Foundation; Centre national d’Etudes spatiales; Ben Gurion University Kreitman Fellowship, and the Israel Academy of Sciences and Humanities (IASH) & Council for Higher Education (CHE) Excellence Fellowship Program for International Postdoctoral Researchers; Centro de Excelencia Severo Ochoa Program SEV-2016-0597; CERCA program of the Generalitat de Catalunya; Cluster of Excellence “Precision Physics, Fundamental Interactions, and Structure of Matter” (PRISMA? EXC 2118/1); Comunidad de Madrid, Contrato de Atracción de Talento 2017-T1/TIC-5520; Czech Science Foundation GAČR, Grant No. 21-16583M; Delta ITP consortium; Department of Energy under Grant No. DE-SC0008541, DE-SC0009919 and DESC0019195; Deutsche Forschungsgemeinschaft (DFG), Project ID 438947057; Deutsche Forschungsgemeinschaft under Germany’s Excellence Strategy - EXC 2121 Quantum Universe - 390833306; European Structural and Investment Funds and the Czech Ministry of Education, Youth and Sports (Project CoGraDS - CZ.02.1.01/0.0/0.0/15 003/0000437); European Union’s H2020 ERC Consolidator Grant “GRavity from Astrophysical to Microscopic Scales” (Grant No. GRAMS-815673); European Union’s H2020 ERC, Starting Grant Agreement No. DarkGRA-757480; European Union’s Horizon 2020 programme under the Marie Sklodowska-Curie Grant Agreement 860881 (ITN HIDDeN); European Union’s Horizon 2020 Research and Innovation Programme Grant No. 796961, “AxiBAU” (K.S.); European Union’s Horizon 2020 Research Council grant 724659 MassiveCosmo ERC-2016-COG; FCT through national funds (PTDC/FIS-PAR/31938/2017) and through project “BEYLA – BEYond LAmbda” with Ref. Number PTDC/FIS-AST/0054/2021; FEDER-Fundo Europeu de Desenvolvimento Regional through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI-01-0145- FEDER-031938) and research Grants UIDB/04434/2020 and UIDP/04434/2020; Fondation CFM pour la Recherche in France; Foundation for Education and European Culture in Greece; French ANR project MMUniverse (ANR-19-CE31-0020); FRIA Grant No.1.E.070.19F of the Belgian Fund for Research, F.R. S.-FNRS Fundação para a Ciência e a Tecnologia (FCT) through Contract No. DL 57/2016/CP1364/ CT0001; Fundação para a Ciência e a Tecnologia (FCT) through Grants UIDB/04434/2020, UIDP/04434/ 2020, PTDC/FIS-OUT/29048/2017, CERN/FIS-PAR/0037/2019 and “CosmoTests – Cosmological tests of gravity theories beyond General Relativity” CEECIND/00017/2018; Generalitat Valenciana Grant PROMETEO/2021/083; Grant No. 758792, project GEODESI; Government of Canada through the Department of Innovation, Science and Economic Development and Province of Ontario through the Ministry of Colleges and Universities; Grants-in-Aid for JSPS Overseas Research Fellow (No. 201960698); I?D Grant PID2020-118159GB-C41 of the Spanish Ministry of Science and Innovation; INFN iniziativa specifica TEONGRAV; Israel Science Foundation (Grant No. 2562/20); Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Nos. 20H01899 and 20H05853; IFT Centro de Excelencia Severo Ochoa Grant SEV-2; Kavli Foundation and its founder Fred Kavli; Minerva Foundation; Ministerio de Ciencia e Innovacion Grant PID2020-113644GB-I00; NASA Grant 80NSSC19K0318; NASA Hubble Fellowship grants No. HST-HF2-51452.001-A awarded by the Space Telescope Science Institute with NASA contract NAS5-26555; Netherlands Organisation for Science and Research (NWO) Grant Number 680-91-119; new faculty seed start-up grant of the Indian Institute of Science, Bangalore, the Core Research Grant CRG/2018/002200 of the Science and Engineering; NSF Grants PHY-1820675, PHY-2006645 and PHY-2011997; Polish National Science Center Grant 2018/31/D/ ST2/02048; Polish National Agency for Academic Exchange within the Polish Returns Programme under Agreement PPN/PPO/2020/1/00013/U/00001; Pró-Reitoria de Pesquisa of Universidade Federal de Minas Gerais (UFMG) under Grant No. 28359; Ramón y Cajal Fellowship contract RYC-2017-23493; Research Project PGC2018-094773-B-C32 [MINECO-FEDER]; Research Project PGC2018-094773-B-C32 [MINECO-FEDER]; ROMFORSK Grant Project. No. 302640; Royal Society Grant URF/R1/180009 and ERC StG 949572: SHADE; Shota Rustaveli National Science Foundation (SRNSF) of Georgia (Grant FR/18-1462); Simons Foundation/SFARI 560536; SNSF Ambizione grant; SNSF professorship Grant (No. 170547); Spanish MINECO’s “Centro de Excelencia Severo Ochoa” Programme Grants SEV-2016- 0597 and PID2019-110058GB-C22; Spanish Ministry MCIU/AEI/FEDER Grant (PGC2018-094626-BC21); Spanish Ministry of Science and Innovation (PID2020-115845GB-I00/AEI/10.13039/ 501100011033); Spanish Proyectos de I?D via Grant PGC2018-096646-A-I00; STFC Consolidated Grant ST/T000732/1; STFC Consolidated Grants ST/P000762/1 and ST/T000791/1; STFC Grant ST/ S000550/1; STFC Grant ST/T000813/1; STFC Grants ST/P000762/1 and ST/T000791/1; STFC under the research Grant ST/P000258/1; Swiss National Science Foundation (SNSF), project The Non-Gaussian Universe and Cosmological Symmetries, Project Number: 200020-178787; Swiss National Science Foundation Professorship Grants No. 170547 and No. 191957; SwissMap National Center for Competence in Research; “The Dark Universe: A Synergic Multi-messenger Approach” Number 2017X7X85K under the MIUR program PRIN 2017; UK Space Agency; UKSA Flagship Project, Euclid.Peer reviewe

Probing new physics through entanglement in diboson production

Abstract Pair production of heavy vector bosons is a key process at colliders: it allows to test our understanding of the Standard Model and to explore the existence of new physics through precision measurements of production rates and differential distributions. New physics effects can be subtle and often require observables specifically designed for their detection. In this study, we focus on quantum information observables that characterise the spin states of the final diboson system. We analyse concurrence bounds, purity, and Bell inequalities for a bipartite qutrit system representing two massive gauge bosons. Our findings show that quantum spin observables can serve as complementary probes for heavy new physics as parametrised by higher dimensional operators in the Standard Model effective field theory. In particular, we find that these observables offer increased sensitivity to operators whose contributions do not interfere with the Standard Model amplitudes at the level of differential cross sections

Probing Higgs-portal dark matter with vector-boson fusion

We constrain the Higgs-portal model employing the vector-boson fusion channel at the LHC. In particular, we include the phenomenologically interesting parameter region near the Higgs resonance, where the Higgs-boson mass is close to the threshold for dark-matter production and a running-width prescription has to be employed for the Higgs-boson propagator. Limits for the Higgs-portal coupling as a function of the dark-matter mass are derived from the CMS search for invisible Higgs-boson decays in vector-boson fusion at 13 TeV. Furthermore, we perform projections for the 14 TeV HL-LHC and the 27 TeV HE-LHC taking into account a realistic estimate of the systematic uncertainties. The respective upper limits on the invisible branching ratio of the Higgs boson reach a level of 2 % and constrain perturbative Higgs-portal couplings up to dark-matter masses of about 110 GeV.Comment: 22 pages, 8 figures, minor revisions in introduction and appendix, version published in JHE

Probing new physics through entanglement in diboson production

Acknowledgements: RA’s research was supported by the F.R.S.-FNRS project no. 40005600 and the FSR Program of UCLouvain. FM is partially supported by the F.R.S.- FNRS under the “Excellence of Science” EOS be.h project no. 30820817. LM is supported by the European Research Council under the European Union’s Horizon 2020 research and innovation Programme (grant agreement n.950246).Abstract Pair production of heavy vector bosons is a key process at colliders: it allows to test our understanding of the Standard Model and to explore the existence of new physics through precision measurements of production rates and differential distributions. New physics effects can be subtle and often require observables specifically designed for their detection. In this study, we focus on quantum information observables that characterise the spin states of the final diboson system. We analyse concurrence bounds, purity, and Bell inequalities for a bipartite qutrit system representing two massive gauge bosons. Our findings show that quantum spin observables can serve as complementary probes for heavy new physics as parametrised by higher dimensional operators in the Standard Model effective field theory. In particular, we find that these observables offer increased sensitivity to operators whose contributions do not interfere with the Standard Model amplitudes at the level of differential cross sections.</jats:p