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Tests of “Other” SeesawsThree Neutrinos and Beyond, Rencontres du Vietnam 2019
Richard Ruiz
Center for Cosmology, Particle Physics, and Phenomenology (CP3)Universite Catholique de Louvain
8 August 2019
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 1 / 35
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Acknowledgements, Apologies, and Disclaimersfinite time constraints =⇒ many omissions
Topic is on models beyond “Minimum Type I Seesaw Model”Focus largely on tests at now-operating colliders, e.g., LHC
▶ Lots of expt’l synergy; see talks by Deppisch, de Gouvea, Kayser, etc
source material:1 Review on Nu Mass Models at Colliders,
Y. Cai, T. Han, T. Li, RR, [1711.02180]
2 European Strategy Update 2019 Chapter on Nu Mass Models,T. Han, T. Li, X. Marcano, S. Pascoli, RR, C. Weiland [1812.07831]
3 Other community documents and some new results
humble reminder: RH neutrinos are not the only explanation for tiny νmasses nor are they necessary (e.g., Type II Seesaw)
Lack of guidance from data and theory =⇒ broad approach needed(careful about putting all eggs in one basket!)
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 2 / 35
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motivation for new physics from ν physics
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 3 / 35
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Nu Masses and New ParticlesNonzero neutrino masses =⇒ new degrees of freedom exist [Ma’98]:
mν 6= 0 + left− handed (LH) Weak currents
LH Majorana Mass : mLν νLν
cL Dirac Mass : mD
ν νLνR
mLν = y〈∆〉 or new dynamics m
Dν = y〈ΦSM〉
(renormalizability)
(gauge invariance)
mν = 0 + renormalizability + gauge inv. =⇒ new particles!
New particles might be charged under new or old gauge symmetriesTypically manifests as processes that do not conserve lepton number(LNV) and/or lepton flavor (LFV) quantum numbers
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 4 / 35
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Nu Masses and New ParticlesNonzero neutrino masses =⇒ new degrees of freedom exist [Ma’98]:
mν 6= 0 + left− handed (LH) Weak currents
LH Majorana Mass : mLν νLν
cL Dirac Mass : mD
ν νLνR
mLν = y〈∆〉 or new dynamics m
Dν = y〈ΦSM〉
(renormalizability)
(gauge invariance)
mν = 0 + renormalizability + gauge inv. =⇒ new particles!
New particles might be charged under new or old gauge symmetries
Typically manifests as processes that do not conserve lepton number(LNV) and/or lepton flavor (LFV) quantum numbers
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 4 / 35
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Nu Masses and New ParticlesNonzero neutrino masses =⇒ new degrees of freedom exist [Ma’98]:
mν 6= 0 + left− handed (LH) Weak currents
LH Majorana Mass : mLν νLν
cL Dirac Mass : mD
ν νLνR
mLν = y〈∆〉 or new dynamics m
Dν = y〈ΦSM〉
(renormalizability)
(gauge invariance)
mν = 0 + renormalizability + gauge inv. =⇒ new particles!
New particles might be charged under new or old gauge symmetriesTypically manifests as processes that do not conserve lepton number(LNV) and/or lepton flavor (LFV) quantum numbers
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 4 / 35
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Theory Developments:
Clarity on Lepton Number Violation at Colliders
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 5 / 35
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Whether or not Ni decouple from collider experiments is now clear:Theorem: In SM + arbitrary number of sterile fermions,mν = 0 =⇒ lepton number (L) conservation Pascoli, et al, [1712.07611]
See also, Pilaftsis [hep-ph/9901206], Kersten and Smirnov [0705.3221 ], + others
In pure Type I scenarios, L-violating processes decouple in two ways:1 High-scale seesaw: µM ≫ ⟨ΦSM⟩ =⇒ mν ∼ mD
(mDµM
), mN ∼ µM
2 Low-scale seesaw: µM ≪ ⟨ΦSM⟩ =⇒ mν ∼ µM
(mDmR
)2, mN ∼ mR
Known also in literature as Inverse Seesaw, Linear Seesaw, Protective Symmetries, etc.
Corollary: Low-scale Type I + if ν approx. massless on expt scale,m2
ν/Q2 ≈ 0 =⇒ approximate L conservation Pascoli, RR, et al, [1812.08750]
=⇒ In Type I models, EW/TeV-scale Dirac-like Ni do not decouple
Collider observation of Ni+ L-violation =⇒ more new particles!Notable since examples of Type II Seesaw mimicking Type I collidersignature known RR, [1703.04669]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 6 / 35
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Whether or not Ni decouple from collider experiments is now clear:Theorem: In SM + arbitrary number of sterile fermions,mν = 0 =⇒ lepton number (L) conservation Pascoli, et al, [1712.07611]
See also, Pilaftsis [hep-ph/9901206], Kersten and Smirnov [0705.3221 ], + others
In pure Type I scenarios, L-violating processes decouple in two ways:1 High-scale seesaw: µM ≫ ⟨ΦSM⟩ =⇒ mν ∼ mD
(mDµM
), mN ∼ µM
2 Low-scale seesaw: µM ≪ ⟨ΦSM⟩ =⇒ mν ∼ µM
(mDmR
)2, mN ∼ mR
Known also in literature as Inverse Seesaw, Linear Seesaw, Protective Symmetries, etc.
Corollary: Low-scale Type I + if ν approx. massless on expt scale,m2
ν/Q2 ≈ 0 =⇒ approximate L conservation Pascoli, RR, et al, [1812.08750]
=⇒ In Type I models, EW/TeV-scale Dirac-like Ni do not decouple
Collider observation of Ni+ L-violation =⇒ more new particles!Notable since examples of Type II Seesaw mimicking Type I collidersignature known RR, [1703.04669]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 6 / 35
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Whether or not Ni decouple from collider experiments is now clear:Theorem: In SM + arbitrary number of sterile fermions,mν = 0 =⇒ lepton number (L) conservation Pascoli, et al, [1712.07611]
See also, Pilaftsis [hep-ph/9901206], Kersten and Smirnov [0705.3221 ], + others
In pure Type I scenarios, L-violating processes decouple in two ways:1 High-scale seesaw: µM ≫ ⟨ΦSM⟩ =⇒ mν ∼ mD
(mDµM
), mN ∼ µM
2 Low-scale seesaw: µM ≪ ⟨ΦSM⟩ =⇒ mν ∼ µM
(mDmR
)2, mN ∼ mR
Known also in literature as Inverse Seesaw, Linear Seesaw, Protective Symmetries, etc.
Corollary: Low-scale Type I + if ν approx. massless on expt scale,m2
ν/Q2 ≈ 0 =⇒ approximate L conservation Pascoli, RR, et al, [1812.08750]
=⇒ In Type I models, EW/TeV-scale Dirac-like Ni do not decouple
Collider observation of Ni+ L-violation =⇒ more new particles!Notable since examples of Type II Seesaw mimicking Type I collidersignature known RR, [1703.04669]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 6 / 35
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Tests of High-Scale Type I Seesaw:1
heavy Majorana neutrinos
1Explicitly not topic of this talk :) See talks by F Deppisch, SK Kang, D TrocinoR. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 7 / 35
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Tests of Low-Scale Type I Seesaw:2
heavy Dirac neutrinos (N)
2Also known as Linear Seesaw, Inverse Seesaw, Protective Symmetries, etc.R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 8 / 35
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Heavy Dirac Neutrinos (N) at Hadron Colliders
... can be produced via mixing through a number of mechanisms
γ W+∗
ℓ+/νℓ
N
(a) (b)
(c)
W+∗/Z∗
gZ∗ h∗
q q′
q
q′
Major recent effort to modernize collider predictions / tools3
Clarity needed on (i) mN ,√
s dependence and (ii) conflicting claims=⇒ more physical/robust collider definitions + public Monte Carlo tools4
3DY@NLO [*1509.06375]; GF [1408.0983, *1602.06957] @NNNLL [*1706.02298]; VBF [1308.2209, *1411.7305,
*1602.06957]; DY,VBF Automation@NLO [*1602.06957]. For details, see review: [*1711.02180]; (*) = U.Pitt. and/or Durham4Event generation up to NLO+PS with HeavyN libraries + MG5aMC@NLO, [feynrules.irmp.ucl.ac.be/wiki/HeavyN]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 9 / 35
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Across√
s, wild interplay of PDF and matrix elements Pascoli, RR, et al [1812.08750]
200 400 600 800 1000
[fb
]
2
lNV
) /
NX
→
pp
(σ
1
10
210
310
410
VBF (NLO)
CC DY (NLO)
NC DY (NLO)
LL)3
GF (N
14 TeV LHC
[GeV]NmHeavy Neutrino Mass,
200 400 600 800 1000
LO
σ/σ
=K
0
1
2
3
VBF (NLO)
NC DY (NLO) CC DY (NLO)LL
3N 500 1000 1500 2000
[fb
]
2
lNV
) /
NX
→
pp
(σ
1
10
210
310
410
VBF (NLO)
CC DY (NLO)
NC DY (NLO)
LL)
3
GF (N
27 TeV HELHC
[GeV]NmHeavy Neutrino Mass,
500 1000 1500 2000
LO
σ/σ
=K
0
1
2
3
VBF (NLO)
NC DY (NLO) CC DY (NLO)LL
3N
Plotted: Flavor-independent heavy N production rate (σ/|V |2) vs massGF and VBF dominate at larger
√s, mN
At√
s = 100 TeV and |VℓN |2 ∼ 10−3, about one N(10 TeV)/ab−1
If roughly BR×ε×A× L ∼ 13 × 30 ab−1, then
√NObs. > 3σ
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 10 / 35
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310 410Heavy Neutrino Mass [GeV]
5−10
4−10
3−10
2−10
1−102 | 4τ
= |V
2 |e4
|V
µe / 2e / 3Xelhτ →95% Sensitivity - pp
[1802.02965]-113 TeV, 35.9 fb
2|e4
CMS upper limit on |V
=02|4µ|V
-1
LHC 14, 300 fb
-1
LHC 14, 3 ab
-1
LHC 27, 3 ab
-1
LHC 27, 15 ab-1
LHC 100, 15 ab
-1
LHC 100, 30 ab
| [1605.08774]*4τVe4on |V
Indirect upper limit
> 5%NmNΓ
After 3 yrs, total rewrite of pp → 3ℓX search for Dirac N!10 − 11× improved sensitivity to cLFV at LHC Pascoli, RR, et al, [1805.09335, 1812.08750]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 11 / 35
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LHC Searches for N
See Talk by D. Trocino
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 12 / 35
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Tests of Type II Seesaw
H++ (H+)γ∗/Z∗q
H−− (H−)
H++
H−−
q (a)
(d)
W±
W±
H±±
H∓
W±∗
H++
H−−
Z∗/h∗ H++ (H+)
H−− (H−)
g
g
γ
γ
(b) (c)
q
q′(e)
H0
H±±
(f)
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 13 / 35
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The Type II Seesaw Mechanism is very special: solves neutrino massproblem without hypothesizing right-handed neutrinos
Important example that mν = 0 ⇒ that νR exist
Add one scalar multiplet with SU(2)L⊗U(1)Y quantum numbers (3, 2)
Lν Yuk. = −y∆Lc(iσ2)∆L = −y∆(νc
L ℓcL)(⟨∆⟩+ δ0 δ+
δ+ δ++
)(νLℓL
)= −y∆⟨∆⟩︸ ︷︷ ︸
=mν
νcLνL + . . . , ⟨∆⟩ < few GeV
Light νm possess tiny LH Majorana mass (NO νR NEEDED!)Neutrino mixing matrix is precisely the 3 × 3 PMNS matrix
After mixing with SM Higgs sector, characterized by existence of scalarswith exotic charges: H0, H±, H±±
Couple to W ,Z ,γ via gauge couplings, NOT through mixing!Interact through new L-violating and cLF-violating couplings
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 14 / 35
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The Type II Seesaw Mechanism is very special: solves neutrino massproblem without hypothesizing right-handed neutrinos
Important example that mν = 0 ⇒ that νR exist
Add one scalar multiplet with SU(2)L⊗U(1)Y quantum numbers (3, 2)
Lν Yuk. = −y∆Lc(iσ2)∆L = −y∆(νc
L ℓcL)(⟨∆⟩+ δ0 δ+
δ+ δ++
)(νLℓL
)= −y∆⟨∆⟩︸ ︷︷ ︸
=mν
νcLνL + . . . , ⟨∆⟩ < few GeV
Light νm possess tiny LH Majorana mass (NO νR NEEDED!)Neutrino mixing matrix is precisely the 3 × 3 PMNS matrix
After mixing with SM Higgs sector, characterized by existence of scalarswith exotic charges: H0, H±, H±±
Couple to W ,Z ,γ via gauge couplings, NOT through mixing!Interact through new L-violating and cLF-violating couplings
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 14 / 35
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Limited number of parameters =⇒ rich experimental predictionsFileviez Perez, Han, Li, et al, [0805.3536], Crivellin, et al [1807.10224] + others
E.g., Higgs branching rates that encode inverse (L) vs normal (R)ordering of light neutrino masses
BR(H±± → ℓ±i ℓ±j ) ∼ (U∗
PMNSmdiagν U†
PMNS)ij
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 15 / 35
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What is new?
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 16 / 35
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Theory studies and LHC searches for H++H−− pairs use Pythia6×KNLO
Okay but limited to Drell-Yan (DY) / (qq)-annihilation channel,=⇒ no EW boson fusion (VBF) or gluon fusion (GF)
Unnecessarily suffer from leading order theory unc., O(15 − 40%)
H++ (H+)γ∗/Z∗q
H−− (H−)
H++
H−−
q (a)
(d)
W±
W±
H±±
H∓
W±∗
H++
H−−
Z∗/h∗ H++ (H+)
H−− (H−)
g
g
γ
γ
(b) (c)
q
q′(e)
H0
H±±
(f)
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 17 / 35
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NEW: NLO- software libraries (UFO model files) Nemevsek, RR, [1909.yyyyy]
Fully exclusive event generation up to NLO(QCD)+PS usingmainstream generators: HERWIG, mg5amc@nlo, SHERPA
0.5 1 1.5
4−10
3−10
2−10
1−10
1
10
210
310
X)
[fb
] ±
±∆
→p
p(
σ
14 TeV LHC
PRELIMINARY
(NLO)
±∆±±∆
(NLO)
∆++∆
(LO)
∆++∆→γγ
jj (NLO)
0∆±±∆
(LO)
∆++∆→gg
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
[TeV]∆mTriplet Scalar Mass,
0
1
2
3
LO
σ /
σ
=
K
jj (NLO)0
∆±±∆
(NLO)
∆++∆ (NLO)
±
∆±±∆
1 2 3 4
4−10
2−10
1
210
410
X)
[fb
] ±
±∆
→p
p(
σ
100 TeV VLHC
PRELIMINARY
(NLO)
±∆±±∆
(NLO)
∆++∆
(LO)∆
++∆→γγ
jj (NLO)
0∆±±∆
(LO)
∆++∆→gg
0.5 1 1.5 2 2.5 3 3.5 4 4.5
[TeV]∆mTriplet Scalar Mass,
0
1
2
3
LO
σ /
σ
=
K
jj (NLO)0
∆±±∆
(NLO)
∆++∆ (NLO)
±
∆±±∆
Watch this space! (or see the review and references therein!!)
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 18 / 35
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Type III Seesaw
γ
T+
T−(0)
T+(±)
(a)(b)
γ∗/Z∗ (W±∗) gZ∗ h∗
q
q (q′)
(c)γ
T−
T± T±
ℓ∓ ℓ∓
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 19 / 35
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Type III Seesaw combines main features of Types I and II Seesaws:Idea: add SU(2)L fermion triplet (Y = 0) with mass mΣ
Key to reconciling GUTs with proton decay E.g., Bajc, Senjanovic [hep-ph/0612029], . . .
Lν Yuk. = −yΣLΣΦSM = −yΣ(νL ℓL
)( Σ0 √2Σ+
√2Σ− −Σ0
)(⟨ΦSM⟩+ h
0
)= −yΣ⟨ΦSM⟩︸ ︷︷ ︸
=mD
νLΣ0 + ...
Assuming that mΣ (Majorana mass) ≫ yΣ⟨Φ⟩ (Dirac mass)
mlight ≈ y2Σv2/2mΣ, mheavy ≈ −mΣ
For mlight = 0.1 eV, if yΣ ∼ O(ye) ∼ 1 · 10−6, mheavy ≈ 300 GeV!
After rotating into the mass basis, mixing-induced cLFV:
|T 0⟩ = cos θ |Σ0⟩+ sin θ |νℓ⟩ ≈ (1 − ε2/2) |Σ0⟩+ ϵ |νℓ⟩|T±⟩ = cosϕ |Σ±⟩+ sinϕ |ℓ±⟩ ≈ (1 − ε2/2) |Σ±⟩+ ϵ |ℓ±⟩
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 20 / 35
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Type III Seesaw combines main features of Types I and II Seesaws:Idea: add SU(2)L fermion triplet (Y = 0) with mass mΣ
Key to reconciling GUTs with proton decay E.g., Bajc, Senjanovic [hep-ph/0612029], . . .
Lν Yuk. = −yΣLΣΦSM = −yΣ(νL ℓL
)( Σ0 √2Σ+
√2Σ− −Σ0
)(⟨ΦSM⟩+ h
0
)= −yΣ⟨ΦSM⟩︸ ︷︷ ︸
=mD
νLΣ0 + ...
Assuming that mΣ (Majorana mass) ≫ yΣ⟨Φ⟩ (Dirac mass)
mlight ≈ y2Σv2/2mΣ, mheavy ≈ −mΣ
For mlight = 0.1 eV, if yΣ ∼ O(ye) ∼ 1 · 10−6, mheavy ≈ 300 GeV!
After rotating into the mass basis, mixing-induced cLFV:
|T 0⟩ = cos θ |Σ0⟩+ sin θ |νℓ⟩ ≈ (1 − ε2/2) |Σ0⟩+ ϵ |νℓ⟩|T±⟩ = cosϕ |Σ±⟩+ sinϕ |ℓ±⟩ ≈ (1 − ε2/2) |Σ±⟩+ ϵ |ℓ±⟩
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 20 / 35
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Collider prediction: heavy charged (T±) and neutral (T 0) leptons:Production through gauge couplings to W ,Z , γ
Decays to SM leptons through mixing, e.g., T± → ℓ±ν
) [f
b]
±
l± o
r T
-T
+T
→pp(
σ
2−10
1−10
1
10
210
310
LL)3
- GF (N±
l±T
LL)3
GF (N
- DY (NLO)-T+T
(LO)-T+ T→γγ
(LO)γγ
= 500 GeVTm
= 1 TeVTm
-2 = 102TlV
[TeV]sCollider Energy, 0 20 40 60 80 100
LOσ/
σ 0123
LL)3GF (N
DY (NLO)
[TeV]E = mNm0 1 2 3 4 5
]1
Lu
min
osi
ty [
fb
1
10
210
310
410
Discovery
E+ + E±NE
Type III Seesaw
14 TeV 27 TeV
13 ab
15 ab
115 ab
σ5
σ2σ5
σ2
TeV-scale heavy charged and neutral leptons discoverable at LHCR. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 21 / 35
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Grand Unified Theories and
Theories with Gauged Lepton Number5
No time! Arise when UV completing simplified Seesaw Models
5Many, many omissions: e.g., SO(10), U(1)B−L, etcR. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 22 / 35
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Gauged Left-Right Parity[Pati, Salam, Mohapatra, Senjanovic, etc., (’74-’79)]
ui
dj
WR
N
ℓ1
um
dn
ℓ2
W∗
R
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 23 / 35
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Left-Right Symmetric ModelLRSM asks what is the origin of (V − A) structure in the SM?
Why is nature weird and differentiates between LH and RH particles?
Idea: suppose nature was once parity symmetric:
G =SU(3)c⊗SU(2)L
⊗SU(2)R⊗U(1)B−L⊗PLR
Ask about parity and automatically learn about B − L!Larger Higgs sector needed to breakdown “right-handed” sector to SMLight neutrino masses are complicated
mνlight = yL⟨∆L⟩︸ ︷︷ ︸
Type II
−(
yDy−1R yT
D
)⟨Φ⟩2⟨∆R⟩−1︸ ︷︷ ︸
Type I a la Type II
Collider predictions: Majorana N, ZR ,WR guage bosons, Type II ScalarsAll enable collider-scale LNV and cLFV
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 24 / 35
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Left-Right Symmetric ModelLRSM asks what is the origin of (V − A) structure in the SM?
Why is nature weird and differentiates between LH and RH particles?
Idea: suppose nature was once parity symmetric:
G =SU(3)c⊗SU(2)L⊗SU(2)R
⊗U(1)B−L⊗PLR
Ask about parity and automatically learn about B − L!Larger Higgs sector needed to breakdown “right-handed” sector to SMLight neutrino masses are complicated
mνlight = yL⟨∆L⟩︸ ︷︷ ︸
Type II
−(
yDy−1R yT
D
)⟨Φ⟩2⟨∆R⟩−1︸ ︷︷ ︸
Type I a la Type II
Collider predictions: Majorana N, ZR ,WR guage bosons, Type II ScalarsAll enable collider-scale LNV and cLFV
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 24 / 35
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Left-Right Symmetric ModelLRSM asks what is the origin of (V − A) structure in the SM?
Why is nature weird and differentiates between LH and RH particles?
Idea: suppose nature was once parity symmetric:
G =SU(3)c⊗SU(2)L⊗SU(2)R⊗U(1)B−L⊗PLR
Ask about parity and automatically learn about B − L!Larger Higgs sector needed to breakdown “right-handed” sector to SMLight neutrino masses are complicated
mνlight = yL⟨∆L⟩︸ ︷︷ ︸
Type II
−(
yDy−1R yT
D
)⟨Φ⟩2⟨∆R⟩−1︸ ︷︷ ︸
Type I a la Type II
Collider predictions: Majorana N, ZR ,WR guage bosons, Type II ScalarsAll enable collider-scale LNV and cLFV
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 24 / 35
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Hallmark Collider Test: Searching for pp → W±R → Nℓ± → ℓ±ℓ±jj
Keung, Senjanovic PRL(’83)
Signature: same-sign ℓ±1 ℓ±2 +2j+ no MET, with pℓ,j
T ≳ O(MWR )
ui
dj
WR
N
ℓ1
um
dn
ℓ2
W∗
R
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 25 / 35
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Hallmark Collider Test: Searching for pp → W±R → Nℓ± → ℓ±ℓ±jj
Keung, Senjanovic PRL(’83)
Signature: same-sign ℓ±1 ℓ±2 +2j+ no MET, with pℓ,j
T ≳ O(MWR )
For (mN/MWR ) ≪ 1, i.e., boosted N, searches are losing sensitivity!R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 26 / 35
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For a 1 → 2 decay, m2ij = (pi + pj)
2 ≈ 2EiEj(1 − cos θij) ≈ EiEjθ2ij
⇒ Angle between e and (qq′)-system = θe(qq′) ∼mN√Ei Ej
∼ 4mNMWR
As (mN/MWR ) shrinks, N is more boosted, and its decay more collimated:
For(
mNMWR
)< 0.1, θe(qq′) falls below det. isolation threshold, θmin
ℓX = 0.4
ui
dj
WR
N
ℓ1
um
dn
ℓ2
W∗
R
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 27 / 35
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For a 1 → 2 decay, m2ij = (pi + pj)
2 ≈ 2EiEj(1 − cos θij) ≈ EiEjθ2ij
⇒ Angle between e and (qq′)-system = θe(qq′) ∼mN√Ei Ej
∼ 4mNMWR
As (mN/MWR ) shrinks, N is more boosted, and its decay more collimated:
For(
mNMWR
)< 0.1, θe(qq′) falls below det. isolation threshold, θmin
ℓX = 0.4
q′
e±
N → jN
|~pN | ∼ MWR≫ mN
qW±
R
Fun Idea: Why not treat second e± like any other poorly isolatedparticle bathed in QCD radiation and label it as constituent of a jet?w/ Mitra, Scott, Spannowsky, PRD (’17) [1607.03504], w/ Mitra, Mattelaer [1607.03504]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 28 / 35
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Search for Neutrino Jets
See Talk by D. Trocino
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 29 / 35
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Can a gauge boson be too heavy for the LHC?
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 30 / 35
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If new gauge mediators are too heavy, light N are still accessible
q
q′
W±
R N
ℓ+q′
q N
ℓ+
When MWR ≫√
s but mN ≲ O(1) TeV, pp → Nℓ+ X production in theLRSM and minimal Type I Seesaw are not discernibleHan, Lewis, RR, Si, [1211.6447]; RR, [1703.04669]
Signature: pp → ℓ±ℓ± + nj + X +pℓ
T ≳ O(mN) + no MET
At 14 (100) TeV with L = 1 (10)ab−1, MWR ≲ 9 (40) TeV probed
DO NOT STOP SEARCHINGFOR HEAVY MAJORANA N 10 20 30 40 50
[TeV]RWM
500
1000
1500
2000
[G
eV]
Nm
Channel±µ±µ95% CLs Exclusion
(Expected)-1100 TeV, 30 ab
(Expected)
-127 TeV, 15 ab
(Expected)-114 TeV, 3 ab
←
(Expected)-1 14 TeV, 100 fb←
-18 TeV, 20.3 fbATLAS Observed←
-18 TeV, 19.7 fbCMS Observed
←
RW = MN m←
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 31 / 35
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If new gauge mediators are too heavy, light N are still accessible
q
q′
W±
R N
ℓ+q′
q N
ℓ+
When MWR ≫√
s but mN ≲ O(1) TeV, pp → Nℓ+ X production in theLRSM and minimal Type I Seesaw are not discernibleHan, Lewis, RR, Si, [1211.6447]; RR, [1703.04669]
Signature: pp → ℓ±ℓ± + nj + X +pℓ
T ≳ O(mN) + no MET
At 14 (100) TeV with L = 1 (10)ab−1, MWR ≲ 9 (40) TeV probed
DO NOT STOP SEARCHINGFOR HEAVY MAJORANA N 10 20 30 40 50
[TeV]RWM
500
1000
1500
2000
[G
eV]
Nm
Channel±µ±µ95% CLs Exclusion
(Expected)-1100 TeV, 30 ab
(Expected)
-127 TeV, 15 ab
(Expected)-114 TeV, 3 ab
← (Expected)-1 14 TeV, 100 fb←
-18 TeV, 20.3 fbATLAS Observed←
-18 TeV, 19.7 fbCMS Observed
←
RW = MN m←
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 31 / 35
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LNV at Higgs FactoriesIf Higgs that breaks U(1)B−L is too heavy, light N are still accessible
N
N
ΦSM
ΦSM ∆B−L
〈ΦSM〉
hSM
N
N
SM-invariant effective field theories with sterile neutrinos exist!Heavy Neutrino Effective Field Theory (NEFT) Aparici, et al [0904.3244]
LNEFT = LType I +∑
5∑
iα(d)i
Λ(d−4)O(d)i , O(5)
S =(Φ†
SMΦSM
) (Nc
RNR)
One subtlety: NR here is chiral/interaction state RR [1703.04669]
Must decompose into mass basis: NR =∑
Xℓmνm +∑
Yℓm′Nm′
After EWSB, NEFT operators map onto light neutrino NSI operators!Can mediate hSM → NN decays! See, e.g., Caputo, et al [1704.08721]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 32 / 35
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LNV at Higgs FactoriesIf Higgs that breaks U(1)B−L is too heavy, light N are still accessible
N
N
ΦSM
ΦSM ∆B−L
〈ΦSM〉
hSM
N
N
SM-invariant effective field theories with sterile neutrinos exist!Heavy Neutrino Effective Field Theory (NEFT) Aparici, et al [0904.3244]
LNEFT = LType I +∑
5∑
iα(d)i
Λ(d−4)O(d)i , O(5)
S =(Φ†
SMΦSM
) (Nc
RNR)
One subtlety: NR here is chiral/interaction state RR [1703.04669]
Must decompose into mass basis: NR =∑
Xℓmνm +∑
Yℓm′Nm′
After EWSB, NEFT operators map onto light neutrino NSI operators!Can mediate hSM → NN decays! See, e.g., Caputo, et al [1704.08721]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 32 / 35
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LNV at Higgs FactoriesIf Higgs that breaks U(1)B−L is too heavy, light N are still accessible
N
N
ΦSM
ΦSM ∆B−L
〈ΦSM〉
hSM
N
N
SM-invariant effective field theories with sterile neutrinos exist!Heavy Neutrino Effective Field Theory (NEFT) Aparici, et al [0904.3244]
LNEFT = LType I +∑
5∑
iα(d)i
Λ(d−4)O(d)i , O(5)
S =(Φ†
SMΦSM
) (Nc
RNR)
One subtlety: NR here is chiral/interaction state RR [1703.04669]
Must decompose into mass basis: NR =∑
Xℓmνm +∑
Yℓm′Nm′
After EWSB, NEFT operators map onto light neutrino NSI operators!Can mediate hSM → NN decays! See, e.g., Caputo, et al [1704.08721]
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 32 / 35
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Summary
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 33 / 35
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Lack of clear guidance from data and theory means we must take a broad,open approach to uncovering the origin of tiny ν masses.
1 Colliders are incredibly complementary to oscillation facilities:▶ Direct production of Seesaw particles▶ Test UV realizations of low-scale neutrino EFTs / NSIs
2 e+e− and DIS machines explore new depths for light N▶ Searches for B, τ → N + X , Z → Nν, h → NN▶ Baseline luminosities at
√s = 240 GeV sufficient to go beyond LHC
3 pp machines offers many opportunites:▶ New analysis techniques =⇒ new territory for cLFV and LNV at LHC▶ N, H±± ZB−L, T 0,± masses up to 10-15 TeV scale at
√s = 100 TeV
4 Lots not covered today, so see the review [1711.02180]
5 Be encouraged! More data soon! Be prepared for a discovery.
R. Ruiz - CP3, Universite Catholique de Louvain “Other Seesaws” - Vietnam 2019 34 / 35