A new physics interpretation of the IceCube data

IceCube has recently observed 37 events of TeV-PeV energies. The angular distribution, with a strong preference for downgoing directions, the spectrum, and the small muon to shower ratio in the data can not be accommodated assuming standard interactions of atmospheric neutrinos. We obtain an excellent fit, however, if a diffuse flux of ultrahigh energy (cosmogenic) neutrinos experiences collisions where only a small fraction of the energy is transferred to the target nucleon. We show that consistent models of TeV gravity or other non-Wilsonian completions of the standard model provide cross sections with these precise features. An increased statistics could clearly distinguish our scenario from the one assumed by IceCube (a diffuse flux of astrophysical neutrinos with a E^{-2} spectrum) and establish the need for new physics in the interpretation of the data.Comment: 13 pages, version to appear in Astroparticle Physic

Phenomenological implications of the new Littlest Higgs model with T-parity

Acknowledgments We would like to thank M. Chala, A. Djouadi, T. Hahn, M. Masip and J. Santiago for very helpful discussions. This work was supported in part by the Spanish Ministry of Science, Innovation and Universities (PID2019-107844GB-C21/AEI/10.13039/501100011033), and by Junta de Andalucía (FQM 101, SOMM17/6104/UGR, P18-FR-5057).We investigate the parameter space of the new Littlest Higgs model with T-parity (NLHT) recently introduced to cure some pathologies of the original LHT. The model requires extra fermion content and additional pseudo-Goldstone bosons. While the heavy top quark sector is similar, there are both T-odd and T-even heavy quarks and leptons with masses proportional to just two sets of Yukawa matrices in flavor space, one more than in the LHT. The new scalars are a singlet and real triplet, T-odd, with masses controlled by gauge and Yukawa couplings, independent of the spontaneous symmetry breaking scale f, and hence potentially light. Imposing that no mass exceeds the cutoff scale, applying current lower bounds on vector-like quarks and assuming a simplified model with mass degenerate heavy fermions compatible with the heavy photon as dark matter constituent, we find that f gets constrained within the interval between 2 and 3TeV, the common Yukawa coupling of heavy leptons gets fixed and the Yukawa coupling of heavy quarks becomes greatly correlated to the top quark Yukawa couplings. The particle spectrum is then bounded from below and above, with the (lightest) heavy photon at about 0.5TeV, not far from the heavy leptons, the new scalars below 1TeV, the usual complex scalar triplet close to the heavy weak bosons at about 1.5 to 2.5TeV, and the heavy quarks and top quark partners between 2 and 5TeV. The new scalars decay predominantly to a standard and a T-odd lepton and have a width comparable to that of the Higgs.Spanish Ministry of Science, Innovation and Universities (PID2019-107844GB-C21/AEI/10.13039/501100011033)Junta de Andalucía (FQM 101, SOMM17/6104/UGR, P18-FR-5057

Neutrino mixing and lepton flavour violation in SUSY-gut models

Presented at the XXVII International Conference of Theoretical Physics, "Matter to the Deepest", Ustron, Poland, september 15-21, 2003.In supersymmetric (SUSY) models the misalignment between fermion and sfermion families introduces unsuppressed flavour-changing processes. Even if the mass parameters are chosen to give no flavour violation, family dependent radiative corrections make this adjustment not stable. In par- ticular, due to the observed large neutrino mixings and potentially large neutrino Yukawa couplings, sizable lepton flavour violation (LFV) is ex- pected. After introducing the basic concepts, the framework and the main assumptions, we report on a recent study of rare leptonic decays in a class of SUSY–GUT models with three quasi-degenerate neutrinos. We show that LFV effects are likely visible in forthcoming experiments.This work has been supported by the Spanish CICYT, the Junta de Andalucía and the European Union under contracts FPA2000-1558, FQM 101, and HPRN-CT-2000-00149, respectively

ρ parameter and H 0 → ℓ i ℓ j in models with TeV sterile neutrinos

The presence of massive sterile neutrinos N mixed with the active ones induces flavor violating processes in the charged lepton sector at the loop level. In particular, the amplitude of H 0 → ¯ ℓ i ℓ j is expected to be proportional to the product of heavy-light Yukawa couplings y i y j = 2 s ν i s ν j m 2 N / v 2 , where s ν i , j express the heavy-light neutrino mixings. Here, we revisit these Higgs decays in the most generic extension of the neutrino sector, focusing on large values of y i . We show that decoupling effects and a cancellation between the two dominant contributions to these processes makes the amplitude about 100 times smaller than anticipated. We find that perturbative values of y i giving an acceptable contribution to the ρ parameter imply B ( H 0 → ¯ ℓ i ℓ j ) < 10 − 8 for any lepton flavors, a rate that is not accessible at current colliders.Spanish Ministry of Science, Innovation and Universities FPA2016-78220-C3 PID2019-107844GB-C21/AEI/10.13039/501100011033Junta de Andalucia FQM 101 SOMM17/6104/UGR P18-FR-1962 P18-FR-5057Consejo Nacional de Ciencia y Tecnologia (CONACyT

Quantum gravity phenomenology at the dawn of the multi-messenger era—A review

The exploration of the universe has recently entered a new era thanks to the multimessenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 ‘‘Quantum gravity phenomenology in the multi-messenger approach", is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.Talent Scientific Research Program of College of Physics, Sichuan University 1082204112427Fostering Program in Disciplines Possessing Novel Features for Natural Science of Sichuan University 2020SCUNL2091000 Talent program of Sichuan province 2021Xunta de GaliciaEuropean Commission European Union ERDF, "Maria de Maeztu'' Units of Excellence program MDM-2016-0692Red Tematica Nacional de Astroparticulas RED2018-102661-TLa Caixa Foundation 100010434European Commission 847648 LCF/BQ/PI21/11830030 754510Ministry of Education, Science & Technological Development, Serbia 451-03-9/2021-14/200124FSR Incoming Postdoctoral Fellowship Ministry of Education, Science and Technological Development, Serbia 451-03-9/2021-14/200124University of Rijeka grant uniri-prirod-18-48Croatian Science Foundation (HRZZ) IP-2016-06-9782Villum Fonden 29405 DGA-FSE 2020-E2117REuropean Regional Development Fund through the Center of Excellence (TK133) "The Dark Side of the Universe'' European Regional Development Fund (ESIF/ERDF)Ministry of Education, Youth & Sports - Czech Republic CoGraDS-CZ.02.1.01/0.0/0.0/15 003/0000437Blavatnik grantBasque Government IT-97916 Basque Foundation for Science (IKERBASQUE)European Space Agency C4000120711 4000132310FNRS (Belgian Fund for Research)Programa de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT)Universidad Nacional Autonoma de Mexico TA100122National University of La Plata X909 DICYT 042131GRNational Research, Development & Innovation Office (NRDIO) - Hungary 123996FQXiSwiss National Science Foundation (SNSF)European Commission 181461 199307Netherlands Organization for Scientific Research (NWO) 680-91-119 15MV71Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of ScienceGrants-in-Aid for Scientific Research (KAKENHI) 20H01899 20H05853 JP21F21789Estonian Research Council PRG356Julian Schwinger FoundationGeneralitat Valenciana Excellence PROMETEO-II/2017/033 PROMETEO/2018/165Istituto Nazionale di Fisica Nucleare (INFN)European ITN project HIDDeN H2020-MSCA-ITN-2019//860881-HIDDeNSwedish Research CouncilEuropean Commission 2016-05996 European Research Council (ERC) European Commission 668679Advanced ERC grant TReXMinistry of Education, Universities and Research (MIUR) 2017X7X85KFonds de la Recherche Scientifique - FNRS 4.4501.18Ministry of Research, Innovation and Digitization - Romania PN19-030102-INCDFM PN-III-P4ID-PCE-2020-2374United States Department of Energy (DOE) DE-SC0020262Ministry of Science, ICT & Future Planning, Republic of Korea 075-15-2020-778German Academic Scholarship Foundation German Research Foundation (DFG) 408049454 420243324 425333893 445990517 Germany's Excellence Strategy (EXC 2121 "Quantum Universe'') 390833306 390837967 Federal Ministry of Education & Research (BMBF) 05 A20GU2 05 A20PX1Centro de Excelencia "Severo Ochoa'' SEV-2016-0588CERCA program of the Generalitat de CatalunyaAgencia de Gestio D'Ajuts Universitaris de Recerca Agaur (AGAUR) Generalitat de Catalunya 2017-SGR-1469 2017-SGR-929 ICCUB CEX2019-000918-MNational Science Centre, Poland 2019/33/B/ST2/00050 2017/27/B/ST2/01902Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) 306414/2020-1Dicyt-USACH 041931MFNational Science Fund of Bulgaria KP-06-N 38/11 RCN ROMFORSK 302640Comunidad de Madrid 2018-T1/TIC-10431 2019-T1/TIC-13177 S2018/NMT-4291UK Research & Innovation (UKRI)Science & Technology Facilities Council (STFC) ST/T000759/1 ST/P000258/1 ST/T000732/1 ST/V005596/1Portuguese Foundation for Science and Technology UIDB/00618/2020 UIDB/00777/2020 UIDP/00777/2020 CERN/FIS-PAR/0004/2019 PTDC/FIS-PAR/29436/2017 PTDC/FISPAR/31938/2017 PTDC/FIS-OUT/29048/2017 SFRH/BD/137127/2018Centre National de la Recherche Scientifique (CNRS), LabEx UnivEarthS ANR-10-LABX-0023 ANR18-IDEX-0001Junta de Andalucia European Commission A-FQM-053-UGR18Natural Sciences and Engineering Research Council of Canada (NSERC) RGPIN-2021-03644National Science Centre Poland Sonata Bis 2019/33/B/ST2/00050 DEC-2017/26/E/ST2/00763Natural Sciences and Engineering Research Council of Canada (NSERC) DGIID-DGA 2015-E24/2Spanish Research State Agency and Ministerio de Ciencia e Innovacion MCIN/AEI PID2019-104114RB-C32 PID2019-105544GB-I00 PID2019-105614GB-C21 PID2019106515GB-I00 PID2019-106802GB-I00 PID2019-107394GB-I00 PID2019-107844GB-C21 PID2019-107847RB-C41 MCIN/AEI PGC2018-095328-B-I00 PGC2018-094856-B-I00 PGC2018-096663-B-C41 PGC2018-096663-B-C44 PGC2018-094626-BC21 PGC2018-101858-B-I00 FPA2017-84543-P FPA2016-76005-C2-1-PSpanish 'Ministerio de Universidades' BG20/00228 Spanish Government PID2020-115845GBI00 Generalitat de Catalunya Comunidad de Madrid S2018/NMT-4291 Spanish Government PID2019-105544GB-I00Perimeter Institute for Theoretical PhysicsGovernment of Canada through the Department of Innovation, Science and Economic DevelopmentProvince of Ontario through the Ministry of Colleges and UniversitiesIstituto Nazionale di Fisica Nucleare (INFN)Centre National de la Recherche Scientifique (CNRS)Netherlands Organization for Scientific Research (NWO)Fundamental Questions Institute (FQXi)European Cooperation in Science and Technology (COST) CA18108Research Council of University of GuilanIniziativa Specifica TEONGRAV Iniziativa Specifica QGSKY Iniziativa Specifica QUAGRAP Iniziativa Specifica GeoSymQFTthe Spanish Research State Agency and Ministerio de Ciencia e Innovacion MCIN/AEI PID2020-115845GBI00 PID2019-108485GB-I00 PID2020-113334GB-I00 PID2020-113701GB-I00 PID2020-113775GB-I00 PID2020-118159GB-C41 PID2020-118159GA-C42 PRE2019-089024Rothchild grant UID/MAT/00212/2020 FPU18/0457

Neutrino events within muon bundles at neutrino telescopes

This work was partially supported by the Spanish Ministry of Sci-ence, Innovation and Universities (PID2019-107844GB-C21/AEI/10.13039/501100011033) and by the Junta de Andalucia, Spain (FQM 101, SOMM17/6104/UGR, P18-FR-1962, P18-FR-5057) . MGG acknowledges a grant from Programa Operativo de Empleo Juvenil (Junta de Andalucia) . The work of GHT has been funded by the program Es-tancias Postdoctorales en el Extranjero 2019-2020 of CONACYT, Mexico. GHT also acknowledges Prof. Pablo Roig for partial support through Catedra Marcos Moshinsky (Fundacion Marcos Moshinsky) . Funding for open access charge: Universidad de Granada/CBUA.The atmospheric neutrino flux includes a component from the prompt decay of charmed hadrons that becomes significant only at E >= 10 TeV. At these energies, however, the diffuse flux of cosmic neutrinos discovered by IceCube seems to be larger than the atmospheric one. Here we study the possibility to detect a neutrino interaction in down-going atmospheric events at km3 telescopes. The neutrino signal will always appear together with a muon bundle that reveals its atmospheric origin and, generically, it implies an increase in the detector activity with the slant depth. We propose a simple algorithm that could separate these events from regular muon bundles.Spanish Ministry of Science, Innovation and Universities PID2019-107844GB-C21/AEI/10.13039/501100011033Junta de Andalucia European Commission FQM 101- SOMM17/6104/UGR- P18-FR-1962- P18-FR-5057Junta de AndaluciaProgram Es-tancias Postdoctorales en el Extranjero 2019-2020 of CONACYT, MexicoUniversidad de Granada/CBUACatedra Marcos Moshinsky (Fundacion Marcos Moshinsky

Cosmology of an Axion-Like Majoron

We propose a singlet majoron model that defines an inverse seesaw mechanism in the v sector. The majoron phi has a mass m(phi) approximate to 0.5 eV and a coupling to the tau lepton similar to the one to neutrinos. In the early universe it is initially in thermal equilibrium, then it decouples at T approximate to 500 GeV and contributes with just Delta N-eff = 0.026 during BBN. At T = 26 keV (final stages of BBN) a primordial magnetic field induces resonant gamma phi oscillations that transfer 6% of the photon energy into majorons, implying Delta N-eff = 0.55 and a 4.7% increase in the baryon to photon ratio. At T approximate to m(phi) the majoron enters in thermal contact with the heaviest neutrino and it finally decays into v (v) over bar pairs near recombination, setting Delta N-eff = 0.85. The boost in the expansion rate at later times may relax the Hubble tension (we obtain H-0 = (71.4 +/- 0.5) km/s/Mpc), while the processes v (v) over bar phi suppress the free streaming of these particles and make the model consistent with large scale structure observations. Its lifetime and the fact that it decays into neutrinos instead of photons lets this axion-like majoron avoid the strong bounds that affect other axion-like particles of similar mass and coupling to photons.We would like to thank Mar Bastero, Adrián Carmona, Mikael R. Chala, Miguel Escudero, Javier Olmedo, José Santiago and Samuel Witte for discussions. This work was partially supported by the Spanish Ministry of Science, Innovation and Universities (PID2019-107844GB-C21/AEI/10.13039/501100011033) and by the Junta de Andalucía (FQM 101, SOMM17/6104/UGR, P18-FR-1962, P18-FR-5057)

Effects of heavy Majorana neutrinos on lepton flavor violating processes

The observation of lepton flavor violating processes at colliders could be a clear signal of a non-minimal neutrino sector. We define a 5-parameter model with a pair of TeV fermion singlets and arbitrary mixings with the three active neutrino flavors. Then we analyze several flavor violating transitions (ℓ→ℓ′γ,ℓ′ℓ′′ℓ¯′′′ or μ−e conversions in nuclei) and Z→ℓ¯ℓ′ decays induced by the presence of heavy neutrinos. In particular, we calculate all the one-loop contributions to these processes and present their analytic expressions. We focus on the genuine effects of the heavy Majorana masses, comparing the results in that case with the ones obtained when the two heavy neutrinos define a Dirac field. Finally, we use our results to update the bounds on the heavy-light mixings in the neutrino sector.This work was supported in part by the Spanish Ministry of Science, Innovation and Universities, under Grant No. FPA2016-78220-C3-1,2,3- P (fondos FEDER), and Junta de Andalucía, Grants No. FQM 101 and No. SOMM17/6104/UGR. G. H. T. wants to acknowledge financial support from Conacyt through the program “Estancia Postdoctoral en el Extranjero.” The work of P. R. has been partially funded by Conacyt through the Project No. 250628 (Ciencia Básica) and Fondo SEP-Cinvestav 2018 (Project No. 142)

The full lepton flavor of the littlest Higgs model with T-parity

We thank useful discussions and comments by A. Blondel, A. Falkowski, G. Hernández- Tomé, J. Hubisz, I. Low and J.M. Pérez-Poyatos. This work has been supported in part by the Ministry of Science, Innovation and Universities, under grant numbers FPA2016- 78220-C3-1,2,3-P (fondos FEDER), and by the Junta de Andalucía grant FQM 101 as well as by the Juan de la Cierva program. J.S. and R.V.M. thank the Mainz Institute for Theoretical Physics (MITP) for its hospitality and partial support during the completion of this work. R.V.M. would also like to thank the Fermilab National Accelerator Laboratory and Northwestern University for their hospitality.We re-examine lepton flavor violation (LFV) in the Littlest Higgs model with T-parity (LHT) including the full T-odd (non-singlet) lepton and Goldstone sectors. The heavy leptons induce two independent sources of LFV associated with the couplings necessary to give masses to the T-odd mirror fermions and to their partners in right-handed SO(5) multiplets, respectively. The latter, which have been neglected in the past, can be decoupled from gauge mediated processes but not from Higgs mediated ones and must therefore also be included in a general analysis of LFV in the LHT. We also further extend previous analyses by considering on-shell Z and Higgs LFV decays together with the LFV processes at low momentum transfer. We show that current experimental limits can probe the LHT parameter space up to global symmetry breaking scales f ∼ 10 TeV. For lower f values ≳ 1 TeV, μ − e transitions require the misalignment between the heavy and the Standard Model charged leptons to be ≲ 1%. Future LFV experiments using intense muon beams should be sensitive to misalignments below the per mille level. For τ LFV transitions, which could potentially be observed at Belle II and the LHC as well as future lepton colliders, we find that generically they can not discriminate between the LHT and supersymmetric models though in some regions of parameter space this may be possible.This work has been supported in part by the Ministry of Science, Innovation and Universities, under grant numbers FPA2016- 78220-C3-1,2,3-P (fondos FEDER), and by the Junta de Andalucía grant FQM 10

Atmospheric lepton fluxes at ultrahigh energies

In order to estimate the possibility to observe exotic physics in a neutrino telescope, it is essential to first understand the flux of atmospheric neutrinos, muons and dimuons. We study the production of these leptons by high-energy cosmic rays. We identify three main sources of muons of energy E > 10^6 GeV: the weak decay of charm and bottom mesons and the electromagnetic decay of unflavored mesons. Contrary to the standard assumption, we find that eta mesons, not the prompt decay of charm hadrons, are the dominant source of atmospheric muons at these energies. We show that, as a consequence, the ratio between the neutrino and muon fluxes is significantly reduced. For dimuons, which may be a background for long-lived staus produced near a neutrino telescope, we find that pairs of E ~ 10^7 GeV forming an angle above 10^-6 rad are produced through D (80%) or B (10%) meson decay and through Drell-Yan proceses (10%). The frequency of all these processes has been evaluated using the jet code PYTHIA.Comment: 10 pages, 4 figures; published versio