Lecture II: Neutrino Mass Models in Context M.J. Ramsey-Musolf U Mass Amherst http://www.physics.umass.edu/acfi/ ACFI NLDBD School 10/31-11/3 2017 � 1
Lecture II Goals • Provide broader BSM context for 0 νββ decay • Provide a simple overview of classes of neutrino mass models with example illustrations • Discuss implications for the interpretation of 0 νββ decay searches • Invite questions ! 2
Lecture II Outline I. The BSM Context II. 0 νββ -decay: General Considerations III. Neutrino Mass Models IV. Implications for 0 νββ -decay 3
I. The BSM Context 4
Fundamental Questions MUST answer SHOULD answer 5
Fundamental Questions MUST answer SHOULD answer ϕ NEW Δ m 2 ~ λ Λ 2 H 0 H 0 Λ Cosmological θ QCD , parity, unification... 6
Fundamental Questions MUST answer SHOULD answer ϕ NEW Δ m 2 ~ λ Λ 2 H 0 H 0 Λ Cosmological θ QCD , parity, unification... Origin of m ν 7 flavor…
Naturalness Problem 8
Scalar Fields in Particle Physics
Scalar Fields in Particle Physics Scalar fields are a simple Scalar fields are theoretically problematic ϕ NEW Δ m 2 ~ λ Λ 2 H 0 H 0 Discovery of a (probably) fundamental 125 GeV scalar : Is it telling us anything about Λ ? Naturalness?
Scalar Fields in Particle Physics Scalar fields are a simple Scalar fields are theoretically problematic ϕ NEW Δ m 2 ~ λ Λ 2 H 0 H 0 Discovery of a (probably) fundamental 125 GeV scalar : m h 2 ~ λ v 2 & G F ~ 1/v 2 : what keeps G F “large” ?
LHC Implications • Weak scale BSM physics (e.g., SUSY) is there but challenging for the hadronic collider • BSM physics is there but a bit heavy (some fine tuning) • We are thinking about the problem incorrectly (cosmological constant???)
The Origin of Matter Cosmic Energy Budget Dark Matter 27 % Baryons Baryons 5 % 68 % Dark Energy Explaining the origin, identity, and relative fractions of the cosmic energy budget is one of the most compelling motivations for physics beyond the Standard Model
Neutrino Masses 14
Neutrino Masses Partners Partners 15
Neutrino Masses Partners Partners Higgs Mechanism 16
Neutrino Masses Partners Partners Higgs Mechanism Something else ? 17
Neutrino Masses Partners Partners “See saw mechanism” New heavy neutrino-like particle = its own anti-particle 18
Neutrino Masses Partners Partners � “See saw mechanism” Physical state masses m 1 ⇡ m 2 D ~ eV M N m 2 ⇡ M N ~ 10 12 – 10 15 GeV New heavy neutrino-like particle = its own anti-particle 19
Neutrino Masses Partners Partners “See saw mechanism” “Leptogenesis” Heavy neutrino decays in early universe generate baryon asym New heavy neutrino-like particle = its own anti-particle 20
BSM Physics: Where Does it Live ? BSM ? Mass Scale M W BSM ? Coupling 21
BSM Physics: Where Does it Live ? BSM ? SUSY, see-saw, BSM Higgs sector… Mass Scale M W Sterile ν ’s, axions, BSM ? dark U(1)… Coupling 22
BSM Physics: Where Does it Live ? BSM ? SUSY, see-saw, BSM Higgs sector… Mass Scale M W Sterile ν ’s, axions, BSM ? dark U(1)… Coupling 23
II. 0 νββ -Decay: General Considerations 24
What Questions Does It Address ? Is the neutrino its own antiparticle ? • Why is there more matter than antimatter ? • Why are neutrino masses so small? • 25
What Questions Does It Address ? Is the neutrino its own antiparticle ? • Why is there more matter than antimatter ? • Why are neutrino masses so small? • “See saw mechanism” “Leptogenesis” Heavy neutrino decays in early universe generate baryon asym New heavy neutrino-like particle = its own anti-particle 26
What Questions Does It Address ? Is the neutrino its own antiparticle ? • Why is there more matter than antimatter ? • Why are neutrino masses so small? • ν = ν “See saw mechanism” “Leptogenesis” Heavy neutrino decays in early universe generate baryon asym New heavy neutrino-like particle = its own anti-particle 27
Neutrinos and the Origin of Matter • Heavy neutrinos decay out of equilibrium in early universe • Majorana neutrinos can decay to particles and antiparticles • Rates can be slightly different (CP violation) Γ ( N ! ` H ) 6 = Γ ( N ! ¯ ` H ∗ ) ( • Resulting excess of leptons over anti-leptons partially converted into excess of quarks over anti-quarks by Standard Model sphalerons 28
Neutrinos and the Origin of Matter • Heavy neutrinos decay out of equilibrium in early universe • Majorana neutrinos can decay to particles and antiparticles • Rates can be slightly different (CP violation) Γ ( N ! ` H ) 6 = Γ ( N ! ¯ ` H ∗ ) ( • Resulting excess of leptons over anti-leptons partially converted into excess of quarks over anti-quarks by Standard Model sphalerons 29
What Questions Does It Address ? Is the neutrino its own antiparticle ? • Why is there more matter than antimatter ? • Why are neutrino masses so small? • � “See saw mechanism” Physical state masses m 1 ⇡ m 2 D ~ eV M N m 2 ⇡ M N ~ 10 12 – 10 15 GeV New heavy neutrino-like particle = its own anti-particle 30
III. Neutrino Mass Models • Type I see-saw “ ν SM”, “ ν MSSM” LRSM • Type II see-saw GUTs • Type III see-saw LRSM • Inverse see-saw MSSM • Radiative + combinations & many other examples 31
νββ -Decay: LNV? Mass Term? 0 νβ L mass = y ¯ L mass = y ¯ L ˜ L c HH T L + h . c . H ν R + h . c . Λ Dirac Majorana 32
Neutrino Mass Models • Type I see-saw “ ν SM”, “ ν MSSM” LRSM • Type II see-saw GUTs • Type III see-saw LRSM • Inverse see-saw MSSM • Radiative + combinations & many other examples 33
νββ -Decay: Type I See-Saw 0 νβ L mass = y ¯ L mass = y ¯ L ˜ L c HH T L + h . c . H ν R + h . c . Λ Dirac Majorana One generation: SM + one N R L mass = y ¯ L ˜ HN R + h . c . + M N ¯ N C R N R � � � ¯ � ✓ ◆ ✓ ◆ 0 m D ⌫ L ¯ N C L mass = ⌫ L R m D M N N R 34
νββ -Decay: Type I See-Saw 0 νβ L mass = y ¯ L mass = y ¯ L ˜ L c HH T L + h . c . H ν R + h . c . Λ Dirac Majorana One generation: SM + one N R Lepton number violating L mass = y ¯ L ˜ HN R + h . c . + M N ¯ N C R N R � � � ¯ � ✓ ◆ ✓ ◆ 0 m D ⌫ L ¯ N C L mass = ⌫ L R m D M N N R 35
νββ -Decay: Type I See-Saw 0 νβ L mass = y ¯ L mass = y ¯ L ˜ L c HH T L + h . c . H ν R + h . c . Λ Dirac Majorana One generation: SM + one N R Lepton number violating L mass = y ¯ L ˜ HN R + h . c . + M N ¯ N C R N R � � Eigenvalues � ¯ � ✓ ◆ ✓ ◆ 0 m D ⌫ L ¯ m 1 ⇡ m 2 N C L mass = ⌫ L D R m D M N N R M N m 2 ⇡ M N 36
νββ -Decay: Type I See-Saw 0 νβ L mass = y ¯ L mass = y ¯ L ˜ L c HH T L + h . c . H ν R + h . c . Λ Dirac Majorana Low-energy eff theory H H Λ = m N N R ν L ν L 37
νββ -Decay: Type I See-Saw 0 νβ L mass = y ¯ L mass = y ¯ L ˜ L c HH T L + h . c . H ν R + h . c . Λ Dirac Majorana “ ν MSM” “ ν MSSM” P. Mermod ⇣ ⌘ N R , ˜ + N R 38
Neutrino Mass Models • Type I see-saw “ ν SM”, “ ν MSSM” LRSM • Type II see-saw GUTs • Type III see-saw LRSM • Inverse see-saw MSSM • Radiative + combinations & many other examples 39
νββ -Decay: Type II See-Saw 0 νβ L mass = y ¯ L mass = y ¯ L ˜ L c HH T L + h . c . H ν R + h . c . Λ Dirac Majorana ⇣ ⌘ Introduce “Complex Triplet”: Δ L ~ (1, 3, 2) ∆ + √ ✓ ◆ ∆ + 2 Δ 0 vev ! Majorana m ν ∆ L = − ∆ + √ ⇥ ⇤ ∆ 0 2 L = g ⇥ ¯ L C i " ∆ L L j ⇤ 2 h ij + h . c . Lepton number violating 40
Left-Right Symmetric Model 41
BSM Mass Scale Parity Breaking Scale ~ M W R ? Energy Scale Weak Scale ~ M W L 42
Left-Right Symmetric Model Parity Breaking Scale ~ M W R ? Energy Scale Weak Scale ~ M W L SU(2) L x SU(2) R x U(1) B-L 43
Left-Right Symmetric Model See-saw scale ? Parity Breaking Scale ~ M W R ? Energy Scale Weak Scale ~ M W L SU(2) L x SU(2) R x U(1) B-L 44
Left-Right Symmetric Model Gauge boson mass eigenstates CKM Matrices for LH & RH sectors: quarks u I Li = ( S u ) ij u mass V L CKM = S † Lj u S d u I Ri = ( T u ) ij u mass Rj d I Li = ( S d ) ij d mass V R CKM = T † u T d Lj d I Ri = ( T d ) ij d mass Rj 45
Left-Right Symmetric Model Gauge boson mass eigenstates PMNS Matrices for LH & RH sectors: leptons Li = ( S ⌫ ) ij ⌫ diag ⌫ I Lj V L PMNS = S † ⌫ S ` Ri = ( T N ) ij N diag N I Rj Li = ( S ` ) ij ` diag ` I Lj Ri = ( T ` ) ij ` diag ` I Rj 46
Left-Right Symmetric Model Two sources of m ν : L = g ⇥ ¯ L C i " ∆ L L j ⇤ 2 h ij + ( L $ R ) + h . c . Type I see-saw Type II see-saw � ¯ � ✓ ◆ ✓ ◆ 0 m D ⌫ L ¯ ⌫ C N C L mass = ⌫ L + m L ¯ L ⌫ L R m D M N N R m L ⇠ gh L h ∆ 0 L i m N ⇠ gh R h ∆ 0 R i 47
Neutrino Mass Models • Type I see-saw “ ν SM”, “ ν MSSM” LRSM • Type II see-saw GUTs • Type III see-saw LRSM • Inverse see-saw MSSM • Radiative + combinations & many other examples 48
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