Sterile neutrinos: unifying cosmology with particle physics Oleg - PowerPoint PPT Presentation

Sterile neutrinos: unifying cosmology with particle physics Oleg Ruchayskiy Oleg.Ruchayskiy @ nbi.ku.dk Live Theoretical Physics Colloquium Oleg Ruchayskiy (NBI) HNLs May 27, 2020 1 / 56

Once upon a time . . . . . . the model of particles and interactions was simple . . . atoms could transform into each other Proton 1  . . . physicists built quantum theory of   Electron 2  radioactivity Atom Photon 3 . . . the theory described experiments    Neutron really well but predicted existence of 4 additional heavy particles these particles were eventually discovered but the structure of the theory dictated existence of yet other particles . . . Oleg Ruchayskiy (NBI) HNLs May 27, 2020 2 / 56

Once upon a time . . . . . . the Standard Model was deemed complicated . . . Of course our model has too many arbitrary features for these predictions to be taken very seriously. . . S. Weinberg (1967) “A model of leptons” 12’400 citations at the time of writing Oleg Ruchayskiy (NBI) HNLs May 27, 2020 3 / 56

Once upon a time . . . . . . all major predictions of the Standard Model were confirmed ATLAS collaboration (2018) Oleg Ruchayskiy (NBI) HNLs May 27, 2020 4 / 56

BSM problem I: Neutrino oscillations What makes neutrinos disappear and then re-appear in a different form? Why they have mass? Predicted by Pontekorvko 1957 soon after the kaon oscillation story (why - because neutrinos are neutral ) Observed in the 1960s as solar neutrino deficit Verified by many experiments both in appearance and disappearance What mediates neutrino oscillations? Oleg Ruchayskiy (NBI) HNLs May 27, 2020 5 / 56

BSM problem II: Baryon asymmetry of the Universe Space around us consists of matter with no evidence of primordial antimatter Standard cosmological scenario predicts symmetrical initial conditions Physics is (mostly) symmetric w.r.t. particles ↔ antiparticles Matter-antimatter symmetric universe would be filled predominantly with photons and neutrinos Observed CP-violations would lead to many billion times smaller asymmetry What particles/processes created tiny matter-antimatter disbalance in the early Universe? Oleg Ruchayskiy (NBI) HNLs May 27, 2020 6 / 56

BSM problem III: Dark matter What is the most prevalent kind of matter in our Universe? Density contrast Observed Dark Halo Stellar Disk Gas M33 rotation curve z ≃ ≃ ≃ 1100 Gives mass to galaxies Does not emit or absorb light Drives cosmological expansion Drives formation of structures What particles is dark matter made of? Oleg Ruchayskiy (NBI) HNLs May 27, 2020 7 / 56

Once upon a time . . . . . . we thought we knew where to look for BSM phenomena We ambitiously wanted to discover new physics alongside the Higgs boson Some even thought we have a compeling reason for that Oleg Ruchayskiy (NBI) HNLs May 27, 2020 8 / 56

. . . Yet our expectations were proven to be wrong ATLAS Preliminary ATLAS SUSY Searches* - 95% CL Lower Limits √ s = 13 TeV July 2019 Model Signature � L dt [fb − 1 ] Mass limit Reference χ 0 E miss χ 0 ˜ q ˜ q , ˜ q → q ˜ 0 e , µ 2-6 jets 36.1 q q ˜ ˜ [2 × , 8 × Degen.] [2 × , 8 × Degen.] 0.9 1.55 m( ˜ 1 ) < 100 GeV 1712.02332 1 T mono-jet 1-3 jets E miss χ 0 36.1 q q ˜ ˜ [1 × , 8 × Degen.] [1 × , 8 × Degen.] 0.43 0.71 m( ˜ q )-m( ˜ 1 ) = 5 GeV 1711.03301 Inclusive Searches T χ 0 ˜ g ˜ g , ˜ g → q ¯ q ˜ 0 e , µ 2-6 jets E miss 36.1 ˜ g 2.0 m( ˜ χ 0 1712.02332 1 T 1 ) < 200 GeV g g ˜ ˜ Forbidden 0.95-1.6 m( ˜ χ 0 1 ) = 900 GeV 1712.02332 q ( ℓℓ )˜ χ 0 3 e , µ 4 jets ˜ g m( ˜ χ 0 g ˜ ˜ g , ˜ g → q ¯ 36.1 1.85 1 ) < 800 GeV 1706.03731 1 ee , µµ 2 jets E miss 36.1 g ˜ 1.2 g )-m( ˜ χ 0 m( ˜ 1 ) = 50 GeV 1805.11381 T χ 0 E miss χ 0 ˜ g ˜ g , ˜ g → qqWZ ˜ 0 e , µ 7-11 jets 36.1 ˜ g 1.8 m( ˜ 1 ) < 400 GeV 1708.02794 1 T χ 0 SS e , µ 6 jets 139 ˜ g 1.15 m( ˜ g )-m( ˜ 1 ) = 200 GeV ATLAS-CONF-2019-015 g → t ¯ t ˜ χ 0 0-1 e , µ 3 b E miss 79.8 g ˜ 2.25 m( ˜ χ 0 ATLAS-CONF-2018-041 g ˜ ˜ g , ˜ 1 T 1 ) < 200 GeV SS e , µ 6 jets 139 g ˜ 1.25 m( ˜ g )-m( ˜ χ 0 1 ) = 300 GeV ATLAS-CONF-2019-015 ˜ b 1 ˜ b 1 , ˜ b 1 → b ˜ χ 0 1 / t ˜ χ ± Multiple 36.1 ˜ ˜ Forbidden 0.9 m( ˜ χ 0 1 ) = 300 GeV, BR( b ˜ χ 0 1708.09266, 1711.03301 b 1 b 1 1 ) = 1 1 Multiple 36.1 b 1 b 1 ˜ ˜ Forbidden 0.58-0.82 m( ˜ χ 0 1 ) = 300 GeV, BR( b ˜ χ 0 1 ) = BR( t ˜ χ ± 1708.09266 1 ) = 0.5 Multiple 139 b 1 b 1 ˜ ˜ Forbidden 0.74 m( ˜ χ 0 1 ) = 200 GeV, m( ˜ χ ± 1 ) = 300 GeV, BR( t ˜ χ ± 1 ) = 1 ATLAS-CONF-2019-015 ˜ b 1 ˜ b 1 , ˜ b 1 → b ˜ χ 0 2 → bh ˜ χ 0 0 e , µ 6 b E miss 139 ˜ ˜ Forbidden 0.23-1.35 ∆ m( ˜ χ 0 2 , ˜ χ 0 1 ) = 130 GeV, m( ˜ χ 0 b 1 b 1 1 ) = 100 GeV SUSY-2018-31 3 rd gen. squarks direct production 1 T ˜ ˜ 0.23-0.48 ∆ m( ˜ χ 0 2 , ˜ χ 0 1 ) = 130 GeV, m( ˜ χ 0 SUSY-2018-31 b 1 b 1 1 ) = 0 GeV χ 0 χ 0 0-2 jets/1-2 b E miss χ 0 ˜ t 1 ˜ t 1 , ˜ t 1 → Wb ˜ 1 or t ˜ 0-2 e , µ 36.1 t 1 ˜ 1.0 m( ˜ 1 )=1 GeV 1506.08616, 1709.04183, 1711.11520 1 T t 1 → Wb ˜ χ 0 1 e , µ 3 jets/1 b E miss 139 ˜ 0.44-0.59 m( ˜ χ 0 t 1 ˜ ˜ t 1 , ˜ t 1 1 )=400 GeV ATLAS-CONF-2019-017 1 T t 1 ˜ ˜ t 1 , ˜ t 1 → ˜ τ 1 b ν , ˜ τ 1 → τ ˜ G 1 τ + 1 e , µ , τ 2 jets/1 b E miss 36.1 ˜ t 1 1.16 m( ˜ τ 1 ) = 800 GeV 1803.10178 T χ 0 χ 0 E miss χ 0 ˜ t 1 ˜ t 1 , ˜ t 1 → c ˜ 1 / ˜ c ˜ c , ˜ c → c ˜ 0 e , µ 2 c 36.1 ˜ c 0.85 m( ˜ 1 ) = 0 GeV 1805.01649 1 T ˜ χ 0 t 1 0.46 m( ˜ t 1 , ˜ c )-m( ˜ 1 ) = 50 GeV 1805.01649 0 e , µ mono-jet E miss ˜ c )-m( ˜ χ 0 36.1 t 1 0.43 m( ˜ t 1 , ˜ 1 ) = 5 GeV 1711.03301 T E miss χ 0 χ 0 ˜ t 2 ˜ t 2 , ˜ t 2 → ˜ t 1 + h 1-2 e , µ 4 b 36.1 ˜ t 2 0.32-0.88 m( ˜ 1 ) = 0 GeV, m( ˜ t 1 )-m( ˜ 1 ) = 180 GeV 1706.03986 T t 2 ˜ ˜ t 2 , ˜ t 2 → ˜ t 1 + Z 3 e , µ E miss 139 ˜ ˜ 0.86 m( ˜ χ 0 t 1 )-m( ˜ χ 0 1 b t 2 t 2 Forbidden 1 ) = 360 GeV, m( ˜ 1 ) = 40 GeV ATLAS-CONF-2019-016 T χ 0 E miss χ ± χ 0 χ ± ˜ 1 ˜ 2 via WZ 2-3 e , µ 36.1 ˜ 1 / ˜ 0.6 m( ˜ χ 0 1 ) = 0 1403.5294, 1806.02293 T 2 ee , µµ E miss χ ± χ 0 χ 0 ≥ 1 139 ˜ 1 / ˜ 0.205 m( ˜ χ ± 1 )-m( ˜ 1 ) = 5 GeV ATLAS-CONF-2019-014 T 2 χ ± ˜ 1 ˜ χ ∓ 2 e , µ E miss 139 χ ± ˜ 0.42 m( ˜ χ 0 ATLAS-CONF-2019-008 1 via WW 1 ) = 0 T 1 χ 0 E miss χ ± χ ± χ 0 χ 0 ˜ χ ± 1 ˜ 2 via Wh 0-1 e , µ 2 b /2 γ 139 ˜ ˜ 1 / ˜ 1 / ˜ Forbidden 0.74 m( ˜ χ 0 1 ) = 70 GeV ATLAS-CONF-2019-019, ATLAS-CONF-2019-XYZ T 2 2 direct ˜ χ ± 1 ˜ χ ∓ 1 via ˜ 2 e , µ E miss χ ± ˜ χ ± χ 0 EW ℓ L / ˜ ν 139 1.0 m( ˜ ℓ , ˜ ν )=0.5(m( ˜ 1 )+m( ˜ 1 )) ATLAS-CONF-2019-008 T 1 τ → τ ˜ χ 0 2 τ E miss 139 ˜ τ ˜ τ [ ˜ [ ˜ τ L , ˜ τ L , ˜ τ R,L ] τ R,L ] 0.16-0.3 0.12-0.39 m( ˜ χ 0 ATLAS-CONF-2019-018 τ ˜ ˜ τ , ˜ 1 ) = 0 1 T χ 0 E miss ˜ ℓ L , R ˜ ℓ L , R , ˜ ℓ → ℓ ˜ 2 e , µ 0 jets 139 ℓ ˜ 0.7 m( ˜ χ 0 1 ) = 0 ATLAS-CONF-2019-008 1 T E miss χ 0 2 e , µ ≥ 1 139 ℓ ˜ 0.256 m( ˜ ℓ )-m( ˜ 1 ) = 10 GeV ATLAS-CONF-2019-014 T ˜ H ˜ H , ˜ H → h ˜ G / Z ˜ G 0 e , µ ≥ 3 b E miss 36.1 ˜ ˜ 0.13-0.23 0.29-0.88 BR( ˜ χ 0 1 → h ˜ 1806.04030 H H G )=1 T 4 e , µ 0 jets E miss 36.1 ˜ 0.3 BR( ˜ χ 0 1 → Z ˜ 1804.03602 H G )=1 T Long-lived Direct ˜ χ + 1 ˜ χ − 1 prod., long-lived ˜ χ ± Disapp. trk 1 jet E miss χ ± ˜ particles 36.1 0.46 Pure Wino 1712.02118 1 T 1 χ ± ˜ 0.15 Pure Higgsino ATL-PHYS-PUB-2017-019 1 Stable ˜ g R-hadron Multiple 36.1 g ˜ 2.0 1902.01636,1808.04095 g → qq ˜ χ 0 Multiple m( ˜ χ 0 Metastable ˜ g R-hadron, ˜ 36.1 ˜ g g ˜ [ τ (˜ [ τ (˜ g ) = 10 ns, 0.2 ns] g ) = 10 ns, 0.2 ns] 2.05 2.4 1 ) = 100 GeV 1710.04901,1808.04095 1 e µ , e τ , µτ LFV pp → ˜ ν τ + X , ˜ ν τ → e µ/ e τ/µτ 3.2 ν τ ˜ 1.9 λ ′ 311 =0.11, λ 132 / 133 / 233 =0.07 1607.08079 χ ± χ ∓ χ 0 4 e , µ 0 jets E miss χ ± χ ± χ 0 χ 0 χ 0 ˜ 1 ˜ 1 / ˜ 2 → WW / Z ℓℓℓℓνν 36.1 ˜ ˜ 1 / ˜ 1 / ˜ [ λ i 33 � 0 , λ 12 k � 0 ] [ λ i 33 � 0 , λ 12 k � 0 ] 0.82 1.33 m( ˜ 1 ) = 100 GeV 1804.03602 T 2 2 g → qq ˜ χ 0 1 , ˜ χ 0 4-5 large- R jets 36.1 [m (˜ [m (˜ χ 0 χ 0 1.3 1.9 Large λ ′′ 1804.03568 ˜ g ˜ g , ˜ 1 → qqq g ˜ ˜ g 1 )=200 GeV, 1100 GeV] 1 )=200 GeV, 1100 GeV] 112 RPV Multiple 36.1 ˜ g g ˜ [ λ ′′ [ λ ′′ 112 =2e-4, 2e-5] 112 =2e-4, 2e-5] 1.05 2.0 m (˜ χ 0 ATLAS-CONF-2018-003 1 )=200 GeV, bino-like χ 0 χ 0 Multiple g g ˜ ˜ [ λ ′′ [ λ ′′ 323 =2e-4, 1e-2] 323 =2e-4, 1e-2] χ 0 t , ˜ t ˜ ˜ t → t ˜ 1 , ˜ 1 → tbs 36.1 0.55 1.05 m (˜ 1 )=200 GeV, bino-like ATLAS-CONF-2018-003 ˜ t 1 ˜ t 1 , ˜ t 1 → bs 2 jets + 2 b 36.7 t 1 ˜ t 1 ˜ [ qq , bs ] [ qq , bs ] 0.42 0.61 1710.07171 ˜ t 1 ˜ t 1 , ˜ t 1 → q ℓ 2 e , µ 2 b 36.1 t 1 ˜ 0.4-1.45 BR( ˜ t 1 → be / b µ ) > 20% 1710.05544 ˜ ˜ [1e-10 < λ ′ [1e-10 < λ ′ 23 k < 1e-8, 3e-10 < λ ′ 23 k < 1e-8, 3e-10 < λ ′ 1 µ DV 136 t 1 t 1 23 k < 3e-9] 23 k < 3e-9] 1.0 1.6 BR( ˜ t 1 → q µ ) = 100%, cos θ t =1 ATLAS-CONF-2019-006 10 − 1 *Only a selection of the available mass limits on new states or 1 Mass scale [TeV] phenomena is shown. Many of the limits are based on simplified models, c.f. refs. for the assumptions made. Oleg Ruchayskiy (NBI) HNLs May 27, 2020 9 / 56