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Author (up) Cottin, G.; Helo, J.C.; Hirsch, M. url  doi
openurl 
  Title Displaced vertices as probes of sterile neutrino mixing at the LHC Type Journal Article
  Year 2018 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 98 Issue 3 Pages 035012 - 6pp  
  Keywords  
  Abstract We investigate the reach at the LHC to probe light sterile neutrinos with displaced vertices. We focus on sterile neutrinos N with masses m(N) similar to (5-30) GeV that are produced in rare decays of the standard model gauge bosons and decay inside the inner trackers of the LHC detectors. With a strategy that triggers on the prompt lepton accompanying the N displaced vertex and considers charged tracks associated with it, we show that the 13 TeV LHC with 3000/fb is able to probe active-sterile neutrino mixings down to vertical bar V-lN vertical bar(2) approximate to 10(-9), with l = e, mu, which is an improvement of up to 4 orders of magnitude when comparing with current experimental limits from trileptons and proposed lepton-jets searches. In the case when tau mixing is present, mixing angles as low as vertical bar V-tau N vertical bar(2) approximate to 10(-8) can be accessed.  
  Address [Cottin, Giovanna] Natl Taiwan Univ, Dept Phys, Taipei 10617, Taiwan, Email: gcottin@phys.ntu.edu.tw;  
  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:000441109800001 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 3684  
Permanent link to this record
 

 
Author (up) Cottin, G.; Helo, J.C.; Hirsch, M.; Pena, C.; Wang, C.S.A.; Xie, S. url  doi
openurl 
  Title 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 (up) Cottin, G.; Helo, J.C.; Hirsch, M.; Silva, D. url  doi
openurl 
  Title Revisiting the LHC reach in the displaced region of the minimal left-right symmetric model Type Journal Article
  Year 2019 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 99 Issue 11 Pages 115013 - 4pp  
  Keywords  
  Abstract We revisit discovery prospects for a long-lived sterile neutrino N at the LHC in the context of left-right symmetric theories. We focus on a displaced vertex search strategy sensitive to O(GeV) neutrino masses produced via a right-handed W-R boson. Both on-shell and off-shell Drell-Yan production of W-R are considered. We estimate the reach as a function of m(N) and m(WR). With root s = 13 TeV and 300/fb of integrated luminosity, the LHC can probe neutrino masses as high as approximately 30 GeV and m(wR) around 6 TeV. The reach goes up to 11.5 TeV with 3000/tb and m(N) similar to 45 GeV. This represents an improvement of a factor of 2 in sensitivity with respect to earlier work.  
  Address [Cottin, Giovanna] Natl Taiwan Univ, Dept Phys, Taipei 10617, Taiwan, Email: gcottin@phys.ntu.edu.tw  
  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:000470867500008 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 4055  
Permanent link to this record
 

 
Author (up) Cottin, G.; Helo, J.C.; Hirsch, M.; Titov, A.; Wang, Z.S. url  doi
openurl 
  Title Heavy neutral leptons in effective field theory and the high-luminosity LHC Type Journal Article
  Year 2021 Publication Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.  
  Volume 09 Issue 9 Pages 039 - 34pp  
  Keywords Beyond Standard Model; Effective Field Theories; Neutrino Physics  
  Abstract Heavy neutral leptons (HNLs) with masses around the electroweak scale are expected to be rather long-lived particles, as a result of the observed smallness of the active neutrino masses. In this work, we study long-lived HNLs in NRSMEFT, a Standard Model (SM) extension with singlet fermions to which we add non-renormalizable operators up to dimension-6. Operators which contain two HNLs can lead to a sizable enhancement of the production cross sections, compared to the minimal case where HNLs are produced only via their mixing with the SM neutrinos. We calculate the expected sensitivities for the ATLAS detector and the future far-detector experiments: AL3X, ANUBIS, CODEX-b, FASER, MATHUSLA, and MoEDAL-MAPP in this setup. The sensitive ranges of the HNL mass and of the active-heavy mixing angle are much larger than those in the minimal case. We study both, Dirac and Majorana, HNLs and discuss how the two cases actually differ phenomenologically, for HNL masses above roughly 100 GeV.  
  Address [Cottin, Giovanna] Univ Adolfo Ibanez, Fac Artes Liberales, Dept Ciencias, Diagonal Las 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:000694840800001 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 4970  
Permanent link to this record
 

 
Author (up) Dib, C.; Helo, J.C.; Hirsch, M.; Kovalenko, S.; Schmidt, I. url  doi
openurl 
  Title Heavy sterile neutrinos in tau decays and the MiniBooNE anomaly Type Journal Article
  Year 2012 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 85 Issue 1 Pages 011301 - 4pp  
  Keywords  
  Abstract Current results of the MiniBooNE experiment show excess events that indicate neutrino oscillations, but only if one goes beyond the standard 3 family scenario. Recently a different explanation of the events has been given, not in terms of oscillations but by the production and decay of a massive sterile neutrino with large transition magnetic moment. We study the effect of such a sterile neutrino in the rare decays tau(-) -> mu(-)mu(+)pi(-)nu and tau(-) -> mu(-)mu(+)e(-)nu nu. We find that searches for these decays, featuring displaced vertices between the mu(-) and the other charged particles, constitute reliable tests for the existence of the sterile neutrino proposed to explain the MiniBooNE anomaly. These searches could be done with already existing experimental data.  
  Address [Dib, Claudio; Carlos Helo, Juan; Kovalenko, Sergey; Schmidt, Ivan] Univ Tecn Federico Santa Maria, Ctr Cient Tecnol Valparaiso, Valparaiso, Chile  
  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:000298925800001 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 869  
Permanent link to this record
 

 
Author (up) Gonzalez, L.; Helo, J.C.; Hirsch, M.; Kovalenko, S.G. url  doi
openurl 
  Title Scalar-mediated double beta decay and LHC Type Journal Article
  Year 2016 Publication Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.  
  Volume 12 Issue 12 Pages 130 - 15pp  
  Keywords Beyond Standard Model; Neutrino Physics  
  Abstract The decay rate of neutrinoless double beta (0 nu beta beta) decay could be dominated by Lepton Number Violating (LNV) short-range diagrams involving only heavy scalar intermediate particles, known as “topology-II” diagrams. Examples are diagrams with diquarks, leptoquarks or charged scalars. Here, we compare the LNV discovery potentials of the LHC and 0 nu beta beta-decay experiments, resorting to three example models, which cover the range of the optimistic-pessimistic cases for 0 nu beta beta decay. We use the LHC constraints from dijet as well as leptoquark searches and find that already with 20/fb the LHC will test interesting parts of the parameter space of these models, not excluded by the current limits on 0 nu beta beta-decay.  
  Address [Gonzalez, L.; Helo, J. C.; Kovalenko, S. G.] Univ Tecn Federico Santa Maria, Ctr Cient Tecnol Valparaiso, Casilla 110-5, Valparaiso, Chile, Email: lorena.gonzalez@alumnos.usm.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:000399774600001 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 3060  
Permanent link to this record
 

 
Author (up) Helo, J.C.; Hirsch, M. url  doi
openurl 
  Title 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 (up) Helo, J.C.; Hirsch, M.; Ota, T. url  doi
openurl 
  Title Proton decay at one loop Type Journal Article
  Year 2019 Publication Physical Review D Abbreviated Journal Phys. Rev. D  
  Volume 99 Issue 9 Pages 095021 - 14pp  
  Keywords  
  Abstract Proton decay is usually discussed in the context of grand unified theories. However, as is well known, in the standard model effective theory proton decay appears in the form of higher-dimensional non-renormalizable operators. Here, we study systematically the one-loop decomposition of the d = 6 B + L violating operators. We exhaustively list the possible one-loop ultraviolet completions of these operators and discuss that, in general, two distinct classes of models appear. Models in the first class need an additional symmetry in order to avoid tree-level proton decay. These models necessarily contain a neutral particle, which could act as a dark matter candidate. For models in the second class the loop contribution dominates automatically over the tree-level proton decay, without the need for additional symmetries. We also discuss possible phenomenology of two example models, one from each class, and their possible connections to neutrino masses, LHC searches and dark matter.  
  Address [Helo, Juan Carlos] Univ La Serena, Dept Fis, Fac Ciencias, Ave Cisternas 1200, La Serena 1200, Chile, Email: jchelo@userena.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:000469019900005 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 4035  
Permanent link to this record
 

 
Author (up) Helo, J.C.; Hirsch, M.; Ota, T. url  doi
openurl 
  Title Proton decay and light sterile neutrinos Type Journal Article
  Year 2018 Publication Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.  
  Volume 06 Issue 6 Pages 047 - 15pp  
  Keywords Beyond Standard Model; Neutrino Physics  
  Abstract Within the standard model, non-renormalizable operators at dimension six (d = 6) violate baryon and lepton number by one unit and thus lead to proton decay. Here, we point out that the proton decay mode with a charged pion and missing energy can be a characteristic signature of d = 6 operators containing a light sterile neutrino, if it is not accompanied by the standard pi(0)e(+) final state. We discuss this effect first at the level of effective operators and then provide a concrete model with new physics at the TeV scale, in which the lightness of the active neutrinos and the stability of the proton are related.  
  Address [Helo, Juan C.] Univ La Serena, Fac Ciencias, Dept Fis, Ave Cisternas 1200, La Serena, Chile, Email: jchelo@userena.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:000435023100004 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 3610  
Permanent link to this record
 

 
Author (up) Helo, J.C.; Hirsch, M.; Ota, T. url  doi
openurl 
  Title Long-range contributions to double beta decay revisited Type Journal Article
  Year 2016 Publication Journal of High Energy Physics Abbreviated Journal J. High Energy Phys.  
  Volume 06 Issue 6 Pages 006 - 32pp  
  Keywords Beyond Standard Model; Neutrino Physics  
  Abstract We discuss the systematic decomposition of all dimension-7 (d = 7) lepton number violating operators. These d = 7 operators produce momentum enhanced contributions to the long-range part of the 0 nu beta beta decay amplitude and thus are severely constrained by existing half-live limits. In our list of possible models one can find contributions to the long-range amplitude discussed previously in the literature, such as the left-right symmetric model or scalar leptoquarks, as well as some new models not considered before. The d = 7 operators generate Majorana neutrino mass terms either at tree-level, 1-loop or 2-loop level. We systematically compare constraints derived from the mass mechanism to those derived from the long-range 0 nu beta beta decay amplitude and classify our list of models accordingly. We also study one particular example decomposition, which produces neutrino masses at 2-loop level, can fit oscillation data and yields a large contribution to the long-range 0 nu beta beta decay amplitude, in some detail.  
  Address [Helo, J. C.] Univ Tecn Federico Santa Maria, Ctr Cient Tecnol Valparaiso, Casilla 110-5, Valparaiso, Chile, Email: juancarlos.helo@usm.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:000377413400001 Approved no  
  Is ISI yes International Collaboration yes  
  Call Number IFIC @ pastor @ Serial 2721  
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