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Author Arbelaez, C.; Helo, J.C.; Hirsch, M. url  doi
openurl 
  Title (down) Long-lived heavy particles in neutrino mass models Type Journal Article
  Year 2019 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 100 Issue 5 Pages 055001 - 15pp  
  Keywords  
  Abstract All extensions of the standard model that generate Majorana neutrino masses at the electroweak scale introduce some heavy mediators, either fermions and/or scalars, weakly coupled to leptons. Here, by “heavy,” we mean implicitly the mass range between a few 100 GeV up to, say, roughly 2 TeV, such that these particles can be searched for at the LHC. We study decay widths of these mediators for several different tree-level neutrino mass models. The models we consider range from the simplest d = 5 seesaw up to d = 11 neutrino mass models. For each of the models, we identify the most interesting parts of the parameter space, where the heavy mediator fields are particularly long lived and can decay with experimentally measurable decay lengths. One has to distinguish two different scenarios, depending on whether fermions or scalars are the lighter of the heavy particles. For fermions, we find that the decay lengths correlate with the inverse of the overall neutrino mass scale. Thus, since no lower limit on the lightest neutrino mass exists, nearly arbitrarily long decay lengths can be obtained for the case in which fermions are the lighter of the heavy particles. For charged scalars, on the other hand, there exists a maximum value for the decay length in these models. This maximum value depends on the model and on the electric charge of the scalar under consideration but can at most be of the order of a few millimeters. Interestingly, independent of the model, this maximum occurs always in a region of parameter space, where leptonic and gauge boson final states have similar branching ratios, i.e., where the observation of lepton number-violating final states from scalar decays is possible.  
  Address [Arbelaez, Carolina] Univ Tecn Federico Santa Maria, Casilla 110-V, Valparaiso, Chile, Email: carolina.arbelaez@usm.cl;  
  Corporate Author Thesis  
  Publisher Amer Physical Soc Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2470-0010 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000483583000006 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 4127  
Permanent link to this record
 
 
Author Cottin, G.; Helo, J.C.; Hirsch, M.; Pena, C.; Wang, C.S.A.; Xie, S. url  doi
openurl 
  Title (down) Long-lived heavy neutral leptons with a displaced shower signature at CMS Type Journal Article
  Year 2023 Publication Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.  
  Volume 02 Issue 2 Pages 011 - 16pp  
  Keywords New Light Particles; Sterile or Heavy Neutrinos  
  Abstract We study the LHC discovery potential in the search for heavy neutral leptons (HNL) with a new signature: a displaced shower in the CMS muon detector, giving rise to a large cluster of hits forming a displaced shower. A new Delphes module is used to model the CMS detector response for such displaced decays. We reinterpret a dedicated CMS search for neutral long-lived particles decaying in the CMS muon endcap detectors for the minimal HNL scenario. We demonstrate that this new strategy is particularly sensitive to active-sterile mixings with tau leptons, due to hadronic tau decays. HNL masses between similar to 1-6 GeV can be accessed for mixings as low as vertical bar V-tau N vertical bar(2) similar to 10(-7), probing unique regions of parameter space in the tau sector.  
  Address [Cottin, Giovanna] Univ Adolfo Ibanez, Fac Artes Liberales, Dept Ciencias, Diagonal Torres, 2640, Santiago, Chile, Email: giovanna.cottin@uai.cl;  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1029-8479 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000924750700002 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 5474  
Permanent link to this record
 
 
Author Beltran, R.; Cottin, G.; Helo, J.C.; Hirsch, M.; Titov, A.; Wang, Z.S. url  doi
openurl 
  Title (down) Long-lived heavy neutral leptons from mesons in effective field theory Type Journal Article
  Year 2023 Publication Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.  
  Volume 01 Issue 1 Pages 015 - 38pp  
  Keywords New Light Particles; SMEFT; Sterile or Heavy Neutrinos  
  Abstract In the framework of the low-energy effective field theory of the Standard Model extended with heavy neutral leptons (HNLs), we calculate the production rates of HNLs from meson decays triggered by dimension-six operators. We consider both lepton number-conserving and lepton-number-violating four-fermion operators involving either a pair of HNLs or a single HNL. Assuming that HNLs are long-lived, we perform simulations and investigate the reach of the proposed far detectors at the high-luminosity LHC to (i) active-heavy neutrino mixing and (ii) the Wilson coefficients associated with the effective operators, for HNL masses below the mass of the B-meson. We further convert the latter to the associated new-physics scales. Our results show that scales in excess of hundreds of TeV and the active-heavy mixing squared as small as 10(-15 )can be probed by these experiments.  
  Address [Beltran, Rebeca; Hirsch, Martin] Univ Valencia, AHEP Grp, Inst Fis Corpuscular, CSIC, Apartado 22085, E-46071 Valencia, Spain, Email: rebeca.beltran@ific.uv.es;  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1029-8479 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000909520000005 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 5455  
Permanent link to this record
 
 
Author Beltran, R.; Cottin, G.; Helo, J.C.; Hirsch, M.; Titov, A.; Wang, Z.S. url  doi
openurl 
  Title (down) Long-lived heavy neutral leptons at the LHC: four-fermion single-N-R operators Type Journal Article
  Year 2022 Publication Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.  
  Volume 01 Issue 1 Pages 044 - 18pp  
  Keywords Beyond Standard Model; Effective Field Theories; Neutrino Physics  
  Abstract Interest in searches for heavy neutral leptons (HNLs) at the LHC has increased considerably in the past few years. In the minimal scenario, HNLs are produced and decay via their mixing with active neutrinos in the Standard Model (SM) spectrum. However, many SM extensions with HNLs have been discussed in the literature, which sometimes change expectations for LHC sensitivities drastically. In the N-R SMEFT, one extends the SM effective field theory with operators including SM singlet fermions, which allows to study HNL phenomenology in a “model independent” way. In this paper, we study the sensitivity of ATLAS to HNLs in the N-R SMEFT for four-fermion operators with a single HNL. These operators might dominate both production and decay of HNLs, and we find that new physics scales in excess of 20 TeV could be probed at the high-luminosity LHC.  
  Address [Beltran, Rebeca; Hirsch, Martin] Univ Valencia, AHEP Grp, Inst Fis Corpuscular, CSIC, Apartado 22085, E-46071 Valencia, Spain, Email: rebeca.beltran@ifis.uv.es;  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1029-8479 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000742012500001 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 5079  
Permanent link to this record
 
 
Author Dercks, D.; Dreiner, H.K.; Hirsch, M.; Wang, Z.S. url  doi
openurl 
  Title (down) Long-lived fermions at AL3X Type Journal Article
  Year 2019 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 99 Issue 5 Pages 055020 - 10pp  
  Keywords  
  Abstract Recently Gligorov et al. [V. V. Gligorov et al., Phys. Rev. D 99, 015023 (2019)] proposed to build a cylindrical detector named AL3X close to the ALICE experiment at interaction point (IP) 2 of the LHC, aiming for discovery of long-lived particles (LLPs) during Run 5 of the HL-LHC. We investigate the potential sensitivity reach of this detector in the parameter space of different new-physics models with long-lived fermions namely heavy neutral leptons (HNLs) and light supersymmetric neutralinos, which have both not previously been studied in this context. Our results show that the AL3X reach can be complementary or superior to that of other proposed detectors such as CODEX-b, FASER, MATHUSLA and SHiP.  
  Address [Dercks, Daniel] DESY, Notkestr 85, D-22607 Hamburg, Germany, Email: daniel.dercks@desy.de;  
  Corporate Author Thesis  
  Publisher Amer Physical Soc Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2470-0010 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000461906400007 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 3949  
Permanent link to this record
 
 
Author Arbelaez, C.; Cottin, G.; Helo, J.C.; Hirsch, M. url  doi
openurl 
  Title (down) Long-lived charged particles and multilepton signatures from neutrino mass models Type Journal Article
  Year 2020 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 101 Issue 9 Pages 095033 - 13pp  
  Keywords  
  Abstract Lepton number violation (LNV) is usually searched for by the LHC collaborations using the same-sign dilepton plus jet signature. In this paper, we discuss multilepton signals of LNV that can arise with experimentally interesting rates in certain loop models of neutrino mass generation. Interestingly, in such models, the observed smallness of the active neutrino masses, together with the high multiplicity of the final states, leads in large parts of the viable parameter space of such models to the prediction of long-lived charged particles, which leave highly ionizing tracks in the detectors. We focus on one particular one-loop neutrino mass model in this class and discuss its LHC phenomenology in some detail.  
  Address [Arbelaez, Carolina] Univ Tecn Federico Santa Maria, Av Espana 1680,Casilla 110-5, Valparaiso 2340000, Chile, Email: carolina.arbelaez@usm.cl;  
  Corporate Author Thesis  
  Publisher Amer Physical Soc Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1550-7998 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000535451000011 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 4403  
Permanent link to this record
 
 
Author Arbelaez, C.; Romao, J.C.; Hirsch, M.; Malinsky, M. url  doi
openurl 
  Title (down) LHC-scale left-right symmetry and unification Type Journal Article
  Year 2014 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 89 Issue 3 Pages 035002 - 19pp  
  Keywords  
  Abstract We construct a comprehensive list of nonsupersymmetric standard model extensions with a low-scale left-right (LR)-symmetric intermediate stage that may be obtained as simple low-energy effective theories within a class of renormalizable SO(10) grand unified theories. Unlike the traditional “minimal” LR models many of our example settings support a perfect gauge coupling unification even if the LR scale is in the LHC domain at a price of only (a few copies of) one or two types of extra fields pulled down to the TeV-scale ballpark. We discuss the main aspects of a potentially realistic model building conforming the basic constraints from the quark and lepton sector flavor structure, proton decay limits, etc. We pay special attention to the theoretical uncertainties related to the limited information about the underlying unified framework in the bottom-up approach, in particular, to their role in the possible extraction of the LR-breaking scale. We observe a general tendency for the models without new colored states in the TeV domain to be on the verge of incompatibility with the proton stability constraints.  
  Address [Arbelaez, Carolina; Romao, Jorge C.] Univ Lisbon, Inst Super Tecn, Dept Fis, P-1049001 Lisbon, Portugal, Email: carolina@ific.uv.es;  
  Corporate Author Thesis  
  Publisher Amer Physical Soc Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1550-7998 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000331878400006 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 1703  
Permanent link to this record
 
 
Author Helo, J.C.; Hirsch, M. url  doi
openurl 
  Title (down) LHC dijet constraints on double beta decay Type Journal Article
  Year 2015 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 92 Issue 7 Pages 073017 - 7pp  
  Keywords  
  Abstract We use LHC dijet data to derive constraints on neutrinoless double beta decay. Upper limits on cross sections for the production of “exotic” resonances, such as a right-handed W boson or a diquark, can be converted into lower limits on the double beta decay half-life for fixed choices of other parameters. Constraints derived from run-I data are already surprisingly strong and complementary to results from searches using same-sign dileptons plus jets. For the case of the left-right symmetric model, in case no new resonance is found in future runs of the LHC and assuming g(L) = g(R), we estimate a lower limit on the double beta decay half-life larger than 10(27) yr can be derived from future dijet data, except in the window of relatively light right-handed neutrino masses in the range 0.5 MeV to 50 GeV. Part of this mass window will be tested in the upcoming SHiP experiment. We also discuss current and future limits on possible scalar diquark contributions to double beta decay that can be derived from dijet data.  
  Address [Helo, J. C.] Univ Tecn Federico Santa Maria, Ctr Cient Tecnol Valparaiso, Valparaiso, Chile, Email: juancarlos.helo@usm.cl;  
  Corporate Author Thesis  
  Publisher Amer Physical Soc Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1550-7998 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000363526700004 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 2419  
Permanent link to this record
 
 
Author Esteves, J.N.; Romao, J.C.; Hirsch, M.; Vicente, A.; Porod, W.; Staub, F. url  doi
openurl 
  Title (down) LHC and lepton flavour violation phenomenology of a left-right extension of the MSSM Type Journal Article
  Year 2010 Publication Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.  
  Volume 12 Issue 12 Pages 077 - 44pp  
  Keywords Supersymmetry Phenomenology  
  Abstract We study the phenomenology of a supersymmetric left-right model, assuming minimal supergravity boundary conditions. Both left-right and (B-L) symmetries are broken at an energy scale close to, but significantly below the GUT scale. Neutrino data is explained via a seesaw mechanism. We calculate the RGEs for superpotential and soft parameters complete at 2-loop order. At low energies lepton flavour violation (LFV) and small, but potentially measurable mass splittings in the charged scalar lepton sector appear, due to the RGE running. Different from the supersymmetric “pure seesaw” models, both, LFV and slepton mass splittings, occur not only in the left-but also in the right slepton sector. Especially, ratios of LFV slepton decays, such as Br((tau) over bar (R) -> μchi(0)(1))/Br((tau) over bar (L) -> μchi(0)(1)) are sensitive to the ratio of (B-L) and left-right symmetry breaking scales. Also the model predicts a polarization asymmetry of the outgoing positrons in the decay mu(+) -> e(+)gamma, A similar to [0, 1], which differs from the pure seesaw “prediction” A = 1. Observation of any of these signals allows to distinguish this model from any of the three standard, pure (mSugra) seesaw setups.  
  Address [Esteves, J. N.; Romao, J. C.] Inst Super Tecn, Dept Fis, P-1049001 Lisbon, Portugal, Email: joaomest@cftp.ist.utl.pt  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1126-6708 ISBN Medium  
  Area Expedition Conference  
  Notes ISI:000285964200015 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 532  
Permanent link to this record
 
 
Author Fonseca, R.M.; Hirsch, M. url  doi
openurl 
  Title (down) Lepton number violation in 331 models Type Journal Article
  Year 2016 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 94 Issue 11 Pages 115003 - 16pp  
  Keywords  
  Abstract Different models based on the extended SU(3)(C) x SU(3)(L) x U(1)(X) (331) gauge group have been proposed over the past four decades. Yet, despite being an active research topic, the status of lepton number in 331 models has not been fully addressed in the literature, and furthermore many of the original proposals can not explain the observed neutrino masses. In this paper we review the basic features of various 331 models, focusing on potential sources of lepton number violation. We then describe different modifications which can be made to the original models in order to accommodate neutrino (and charged lepton) masses.  
  Address [Fonseca, Renato M.; Hirsch, Martin] Univ Valencia, AHEP Grp, CSIC, Inst Fis Corpuscular, Parc Cient Paterna,Calle Catedrat Jose Beltran 2, E-46980 Paterna, Valencia, Spain, Email: renato.fonseca@ific.uv.es;  
  Corporate Author Thesis  
  Publisher Amer Physical Soc Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2470-0010 ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000389026700005 Approved no  
  Is ISI yes International Collaboration no  
  Call Number IFIC @ pastor @ Serial 2874  
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