Neutrino Models at Colliders Bhupal Dev Washington University in - PowerPoint PPT Presentation

Neutrino Models at Colliders Bhupal Dev Washington University in St. Louis SUSY2019 Corpus Christi May 22, 2019

Harbinger of New Physics Non-zero neutrino mass = ⇒ physics beyond the Standard Model 2

Harbinger of New Physics Non-zero neutrino mass = ⇒ physics beyond the Standard Model neutrinos d s b u c t e µ τ meV eV keV MeV GeV TeV Perhaps something beyond the standard Higgs mechanism... 2

Harbinger of New Physics Non-zero neutrino mass = ⇒ physics beyond the Standard Model neutrinos d s b u c t e µ τ meV eV keV MeV GeV TeV Perhaps something beyond the standard Higgs mechanism... Can we probe the origin of neutrino mass at colliders? 2

Neutrino Mass Models [see Tuesday plenary talk by S. King] From pheno point of view, can broadly categorize into Tree-level (seesaw) vs loop-level (radiative) Minimal (SM gauge group) vs gauge-extended [e.g. U (1) B − L , Left-Right] Non-supersymmetric vs Supersymmetric 3

Neutrino Mass Models [see Tuesday plenary talk by S. King] From pheno point of view, can broadly categorize into Tree-level (seesaw) vs loop-level (radiative) Minimal (SM gauge group) vs gauge-extended [e.g. U (1) B − L , Left-Right] Non-supersymmetric vs Supersymmetric New fermions, gauge bosons, and/or scalars – messengers of neutrino mass physics . Rich phenomenology. For messenger scale � O ( few TeV ), accessible at the LHC and/or future colliders. Connection to other puzzles (e.g. baryogenesis, dark matter). 3

New Fermions (aka sterile neutrinos/heavy neutrinos/heavy neutral leptons) 4

Type-I Seesaw [Minkowski (PLB ’77); Mohapatra, Senjanovi´ c (PRL ’80); Yanagida ’79; Gell-Mann, Ramond, Slansky ’79; Glashow ’80] Introduce SM-singlet Majorana fermions ( N ). −L ⊃ Y ν L φ c N + 1 c N + H . c . 2 M N N After EWSB, m ν ≃ − M D M − 1 N M T D , where M D = vY ν . [Figure from Antusch, Cazzato, Fischer (IJMPA ’17)] Y top Neutrino Yukawa coupling y n 2 =D m atm 2 m n GUT 10 - 3 L EW 2 =D m sol 2 m n Y e 10 - 7 10 - 9 10 - 11 reactor & LSND anomaly eV keV GeV PeV ZeV M GUT M Pl Sterile neutrino mass scale 5

Type-I Seesaw [Minkowski (PLB ’77); Mohapatra, Senjanovi´ c (PRL ’80); Yanagida ’79; Gell-Mann, Ramond, Slansky ’79; Glashow ’80] Introduce SM-singlet Majorana fermions ( N ). −L ⊃ Y ν L φ c N + 1 c N + H . c . 2 M N N After EWSB, m ν ≃ − M D M − 1 N M T D , where M D = vY ν . [Figure from Antusch, Cazzato, Fischer (IJMPA ’17)] Y top Neutrino Yukawa coupling y n 2 =D m atm 2 m n GUT 10 - 3 L EW 2 =D m sol 2 m n Y e 10 - 7 10 - 9 10 - 11 reactor & LSND anomaly eV keV GeV PeV ZeV M GUT M Pl Sterile neutrino mass scale Naturalness of Higgs mass suggests M N � 10 7 GeV. [Vissani (PRD ’98); Clarke, Foot, Volkas (PRD ’15); Bambhaniya, BD, Goswami, Khan, Rodejohann (PRD ’17)] 5

Heavy Majorana Neutrinos at the LHC [Keung, Senjanovi´ c (PRL ’83); Datta, Guchait, Pilaftsis (PRD ’94); Panella, Cannoni, Carimalo, Srivastava (PRD ’02); Han, Zhang (PRL ’06); del Aguila, Aguilar-Saavedra, Pittau (JHEP ’07); Atre, Han, Pascoli, Zhang (JHEP ’09)] Same-sign dilepton plus jets (without / E T ) q W ' q q' N V N W + + V N + q -1 35.9 fb (13 TeV) 1 Mixing CMS Preliminary 95% CL upper limit 1 10 − − 2 10 2 3 Observed V 10 − eN 2 Observed V µ N − 4 10 * 2 V V eN N µ Observed 2 2 V + V eN N µ 5 10 − 2 3 10 10 m (GeV) [CMS PAS EXO-17-028] N Probes (sub) TeV-scale heavy Majorana neutrinos with ‘large’ active-sterile mixing. 6

Low-scale Seesaw with Large Mixing Naively, active-sterile neutrino mixing is small for EW-scale seesaw: � � m ν 100 GeV V ℓ N ≃ M D M − 1 � 10 − 6 ≃ N M N M N ‘Large’ mixing effects possible with special structures of M D and M N . [Pilaftsis (ZPC ’92); Gluza (APPB ’02); de Gouvea ’07; Kersten, Smirnov (PRD ’07); Gavela, Hambye, Hernandez, Hernandez (JHEP ’09); Ibarra, Molinaro, Petcov (JHEP ’10); Adhikari, Raychaudhuri (PRD ’11); Mitra, Senjanovi´ c, Vissani (NPB ’12); BD, Lee, Mohapatra (PRD ’13);...] 7

Low-scale Seesaw with Large Mixing Naively, active-sterile neutrino mixing is small for EW-scale seesaw: � � m ν 100 GeV V ℓ N ≃ M D M − 1 � 10 − 6 ≃ N M N M N ‘Large’ mixing effects possible with special structures of M D and M N . [Pilaftsis (ZPC ’92); Gluza (APPB ’02); de Gouvea ’07; Kersten, Smirnov (PRD ’07); Gavela, Hambye, Hernandez, Hernandez (JHEP ’09); Ibarra, Molinaro, Petcov (JHEP ’10); Adhikari, Raychaudhuri (PRD ’11); Mitra, Senjanovi´ c, Vissani (NPB ’12); BD, Lee, Mohapatra (PRD ’13);...] One example: [Kersten, Smirnov (PRD ’07)]     m 1 δ 1 ǫ 1 0 M 1 0 with ǫ i , δ i ≪ m i . M D = m 2 δ 2 ǫ 2 and M N = M 1 0 0     m 3 δ 3 ǫ 3 0 0 M 2 7

Low-scale Seesaw with Large Mixing Naively, active-sterile neutrino mixing is small for EW-scale seesaw: � � m ν 100 GeV V ℓ N ≃ M D M − 1 � 10 − 6 ≃ N M N M N ‘Large’ mixing effects possible with special structures of M D and M N . [Pilaftsis (ZPC ’92); Gluza (APPB ’02); de Gouvea ’07; Kersten, Smirnov (PRD ’07); Gavela, Hambye, Hernandez, Hernandez (JHEP ’09); Ibarra, Molinaro, Petcov (JHEP ’10); Adhikari, Raychaudhuri (PRD ’11); Mitra, Senjanovi´ c, Vissani (NPB ’12); BD, Lee, Mohapatra (PRD ’13);...] One example: [Kersten, Smirnov (PRD ’07)]     m 1 δ 1 ǫ 1 0 M 1 0 with ǫ i , δ i ≪ m i . M D = m 2 δ 2 ǫ 2 and M N = M 1 0 0     m 3 δ 3 ǫ 3 0 0 M 2 But the steriles with large mixing are ‘quasi-Dirac’ with suppressed LNV. Generic requirement in order to satisfy neutrino oscillation data and 0 νββ constraints. [Abada, Biggio, Bonnet, Gavela, Hambye (JHEP ’07); Ibarra, Molinaro, Petcov (JHEP ’10); Fernandez-Martinez, Hernandez-Garcia, Lopez-Pavon, Lucente (JHEP ’15); Drewes, Garbrecht, Gueter, Klaric (JHEP ’16)] Should also look for lepton number conserving channels at the LHC. 7

Inverse Seesaw Provides a (technically) natural low-scale seesaw framework. Two sets of SM-singlet fermions with opposite lepton numbers. [Mohapatra, Valle (PRD ’86)] Y ν L φ c N + M N SN + 1 2 µ S SS c + H . c . −L Y ⊃ ( M D M − 1 N ) µ S ( M D M − 1 N ) T m ν ≃ Naturally allows for large mixing: � � m ν 1 keV ≈ 10 − 2 V ℓ N ≃ µ S µ S 8

Inverse Seesaw Provides a (technically) natural low-scale seesaw framework. Two sets of SM-singlet fermions with opposite lepton numbers. [Mohapatra, Valle (PRD ’86)] Y ν L φ c N + M N SN + 1 2 µ S SS c + H . c . −L Y ⊃ ( M D M − 1 N ) µ S ( M D M − 1 N ) T m ν ≃ Naturally allows for large mixing: � � m ν 1 keV ≈ 10 − 2 V ℓ N ≃ µ S µ S But again quasi-Dirac heavy neutrinos. Should look for both lepton number conserving and violating channels at the LHC. Ratio of same-sign to opposite-sign dilepton signal could test the Majorana vs. Dirac nature. [Gluza, Jelinski (PLB ’15); BD, Mohapatra (PRL ’15); Gluza, Jelinski, Szafron (PRD ’16); Anamiati, Hirsch, Nardi (JHEP ’16); Das, BD, Mohapatra (PRD ’17)] 8

Heavy (Pseudo) Dirac Neutrinos at the LHC [del Aguila, Aguilar-Saavedra (PLB ’09; NPB ’09); Chen, BD (PRD ’12); Das, Okada (PRD ’13); Das, BD, Okada (PLB ’14); Izaguirre, Shuve (PRD ’15); Dib, Kim (PRD ’15); Dib, Kim, Wang (PRD ’17; CPC ’17); Dube, Gadkari, Thalapillil (PRD ’17)] Trilepton plus / E T q l + W + l − N q ′ ¯ W + l + ν -1 -1 35.9 fb (13 TeV) 35.9 fb (13 TeV) 1 1 2 2 | | eN 95% CL upper limits N 95% CL upper limits CMS CMS µ |V |V Expected Expected − 1 − 1 10 10 ± 2 std. deviation ± 2 std. deviation ± 1 std. deviation ± 1 std. deviation 2 2 10 − 10 − Observed Observed Observed, Observed, − 3 − 3 10 10 prompt N prompt N DELPHI prompt DELPHI prompt decays decays DELPHI long-lived DELPHI long-lived − 4 − 4 10 10 L3 CMS 8 TeV ATLAS CMS 8 TeV ATLAS 5 5 − − 10 10 3 3 2 2 1 10 10 10 1 10 10 10 m (GeV) m (GeV) N N 2 2 [CMS Collaboration, Phys. Rev. Lett. 120 , 221801 (2018)] 9

Importance of VBF for Heavy Neutrino Production [BD, Pilaftsis, Yang (PRL ’14); Alva, Han, Ruiz (JHEP ’15); Degrande, Mattelaer, Ruiz, Turner (PRD ’16); Das, Okada (PRD ’16)] [fb] ± N l - NLO 4 10 N - NLO ν 2  N ± l N l +1j - NLO V 3 10  ± X) / N l j - VBF NLO 2 N +0,1j - GF LO 10 ν N → 10 (pp 14 TeV LHC σ 1 200 400 600 800 1000 1.4 LO 1.2 σ 1 / 0.8 NLO 200 400 600 800 1000 σ Heavy Neutrino Mass, m [GeV] [Cai, Han, Li, Ruiz (Front. in Phys. ’18)] N 10

Higgs Decay [BD, Franceschini, Mohapatra (PRD ’12); Cely, Ibarra, Molinaro, Petcov (PLB ’13)] ¯ ν ν ¯ h h ` + N ` + N W + Z ` − ν ` − ν � h < 13 MeV � h < 13 MeV 0.100 0.100 � h < 1.1 � SM � h < 1.1 � SM ( 100 TeV ) 0.001 h decay 0.001 h decay W decay ( 14 TeV ) 10 - 5 10 - 5 W decay V ) 2 4 T e 2 ( 1 0 ��� | V eN | V � N 10 - 7 10 - 7 ( 100 TeV ) 10 - 9 10 - 9 FCC - ee FCC - ee 10 - 11 10 - 11 50 100 150 200 50 100 150 200 M N ( GeV ) M N ( GeV ) � h < 13 MeV 0.100 � h < 1.1 � SM * V � N | 0.001 h decay | V eN 10 - 5 ( 14 TeV ) MEG 2 ( 100 TeV ) 10 - 7 50 100 150 200 [Das, BD, Kim (PRD ’17)] M N ( GeV ) 11