Guideline Storage of Sterile and Non-Sterile Supply within ...
Higgs Production through Sterile...
Transcript of Higgs Production through Sterile...
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Higgs Production through Sterile Neutrinos
based on arXiv:1512.06035
Oliver FischerUniversity of Basel, Switzerland
IAS Conference, “The Future of High Energy Physics 2016”Hongkong, January the 19th, 2016
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Motivation for sterile neutrinos
I Observation of neutrino oscillations requires at least two ofthe light neutrinos to be massive.
I Neutrino masses can be accounted for efficiently byright-handed or “sterile neutrinos”.
I Seesaw formula: (mν)αβ = −12v2EW(Y Tν ·M−1Yν
)αβ
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The Seesaw Mechanism
I Näıve (1 νL, 1 νR) version: mν =12v2EW|yν |
2
MR
I More realistic example, the (2 νL, 2 νR) version:
Yν =
(O(yν) 0
0 O(yν)
),
(MR 0
0 MR + ε
)
⇒ mνi =v2EWO(y2ν )
MR(1 + ε)
⇒ Knowledge of mνi implies a relation between yν and MR .
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Lowscale Seesaw
I This example uses a specific structure of the Yukawa and massmatrices that can be realised by symmetries (no fine tuning).
I A (2 νL, 2 νR) example:
Yν =
(O(yν) 0O(yν) 0
),
(0 MRMR ε
)
⇒ mνi = 0 + εv2EWO(y2ν )
M2R
⇒ In general: no fixed relation between yν and MR .⇒ Large yν are compatible with neutrino oscillations.
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The Big Picture
GUT
Leptogenesis also
for larger masses
EW scale
models
ë
reactor
anomaly
ø
øø
warm Dark Matter
Lowscale Leptogenesis
mΝ2=Dmatm
2
mΝ2=Dmsol
2
eV keV MeV GeV TeV PeV EeV ZeV MGUT MPl
perturbativity
Ytop
Ye
10-5
10-7
10-9
10-11
Majorana Mass MR
Neu
trin
oY
ukaw
aco
upli
ng
y î
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Symmetry Protected Seesaw Scenario
I Assumption: collider phenomenology dominated by two sterileneutrinos Ni with protective symmetry, such that
LN = −1
2N1RM(N
2R)
c − yναN1R φ̃† Lα + H.c.
I The active-sterile mixing parameter: θα =yναvEW√
2M
I The leptonic mixing matrix to leading order in θα
U =
Ne1 Ne2 Ne3 − i√2θe1√2θe
Nµ1 Nµ2 Nµ3 − i√2θµ1√2θµ
Nτ1 Nτ2 Nτ3 − i√2θτ √2θτ0 0 0 i√
21√2
−θ∗e −θ∗µ −θ∗τ − i√2(
1− θ22)
1√2
(1− θ22
)
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Interactions between heavy neutrinos and the SM
I Charged current (CC):
j±µ =g
2θα ¯̀α γµ (−iN1 + N2)
I Neutral current (NC):
j0µ =g
2 cW
[θ2N̄2γµN2 + (ν̄i γµ ξα1N1 + ν̄i γµ ξα2N2 + H.c)
]I Higgs boson Yukawa interaction:
LYukawa =3∑
i=1
ξα2
√2M
vEWνiφ
0(N1 + N2
)I With the mixing parameters: ξα1 = (−i)N ∗αβ
θβ√2, ξα2 = i ξα1
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Combination of present bounds
50 100 150 200
1
10-1
10-2
10-3
10-4
10-5
10-6
M @GeVD
Q2
50 100 150 200
1
10-1
10-2
10-3
10-4
M @GeVD
ÈyÈ
Direct searches
Delphi HZ pole searchesL 2Σ: ÈyÈ= ÚΑ yΝΑ2 , Q2=ÚΑÈΘΑ
2
LHC HHiggs decays*L 1Σ: ÈyÈ= ÚΑ yΝΑ2 , Q2=ÚΑÈΘΑ
2
Aleph He+e- ® 4 leptonsL 1Σ: ÈyÈ=ÈyΝe È, Q2=ÈΘe
2
Other Hglobal fitLÈyÈ= ÈyΝe È, Q
2=ÈΘe2
ÈyÈ= ÈyΝΜ È, Q2=ÈΘΜ
2
ÈyÈ= ÈyΝΤ È, Q2=ÈΘΤ
2
Antusch, OF; arXiv:1502.05915 (2015)
∗ Currently dominated by h → γγ.
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Resonant mono-Higgs from sterile neutrinos
ν
W ν
hN
e+
e−
Z
ν
ν
h
N
e+
e−
I Generally: σhνν = σSMhνν + σ
Non-Uhνν + σ
Directhνν .
I σDirecthνν from on-shell production of sterile neutrinos.
? Interference with SM-background strongly suppressed.? W -exchange process effective at larger centre-of-mass
energies, but sensitive only to yνe .? s-channel production (Z boson) produces all flavours.
I σNon-Uhνν : indirect effect (via input parameters) from theinduced non-unitarity of the PMNS matrix.
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Resonant mono-Higgs-production cross section
200 400 600 800 1000
10
20
30
40
50
M @GeVD
ΣhΝΝ
Direct HÈΘe
2L@fbD
200 400 600 800 1000
0.05
0.10
0.15
0.20
0.25
M @GeVD
ΣhΝΝ
Direct HÈΘΤ2L@fbD
Ecm @GeVD
240
350
500
1000
Antusch, Cazzato, OF, arXiv:1512.06035 (2015)
I Using present upper bounds at 68% Bayesian confidence level.
I Mono Higgs production cross section in the SM is ∼ 54 fb at250 and 350 GeV
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Simulation, reconstruction and kinematic cuts
I Event simulation: WHIZARD 2.2.7
I Showering: PYTHIA 6.427
I Reconstruction: Delphes 3.2.0 (ILD card)
I Anaylsis: Madanalysis5
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The Higgs Peak: |yνe | = 0.036 & M = 152 GeV, 10 ab−1
Ecm=240 GeV
100 105 110 115 120 125 1300
10000
20000
30000
40000
di-jet invariant mass @GeVD
EventsBin10ab-1
e+e-®ΝN®ΝΝh®jj
e+e-®ΝΝh SM®jj
e+e-®4f SM®jj
Antusch, Cazzato, OF, arXiv:1512.06035 (2015)
Our cuts (not fully optimised):
I Pre selection: Nj = 2,N` = 0, 110 < Mjj < 125 GeV
I For the example:Pjj > 70,�ET > 15 GeV
Event counts: (starting with pre selection)
BKG 548.584 → 18.627σDirecthνν 15.335 → 4.846
⇒ S√S+B' 30!
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Contamination of SM parameters
150 200 250 300 350
0.001
0.002
0.005
0.010
0.020
0.050
0.100
M @GeVD
ΣhΝΝΣ
hΝΝ
SM-1
Ecm = 240 GeV
Ecm = 350 GeV
HΣbbΝΝH240 GeVL´10ab-1L-12
HΣbbΝΝH350 GeVL´3.5ab-1L-12
Antusch, Cazzato, OF, arXiv:1512.06035 (2015)
Standard cuts for Higgs events at lepton colliders:√s 240 GeV 350 GeV
Missing Mass [GeV] 80 ≤ Mmiss ≤ 140 50 ≤ Mmiss ≤ 240Transverse P [GeV] 20 ≤ PT ≤ 70 10 ≤ PT ≤ 140Longitudinal P [GeV] |PL| < 60 |PL| < 130Maximum P [GeV] |P| < 30 |P| < 60Di-jet Mass [GeV] 100 ≤ Mjj ≤ 130 100 ≤ Mjj ≤ 130Angle (jets) [Rad] α > 1.38 α > 1.38
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Sensitivity of the mono-Higgs channel to neutrino mixing
Case I
150 200 250 300 350 400 450 5000.002
0.005
0.010
0.020
0.050
0.100
0.200
M @GeVD
ÈyΝeÈ
Ecm @GeVD
240, reconstructed
350, reconstructed
500, reconstructed
240, parton
350, parton
500, parton
Present upper bound
Antusch, Cazzato, OF, arXiv:1512.06035 (2015)
Considered:10 ab−1 for 240 GeV, 3.5 ab−1 for 350 GeV, 1 ab−1 for 500 GeV
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Summary and conclusions
I Sterile neutrinos are well motivated extensions of the SM.
I Symmetry protected scenarios allow for large Yukawacouplings and masses in the interesting range.
I Higher center-of-mass energies lead to increasedmono-Higgs production cross sections from sterileneutrinos.
I√s = 350 GeV is even more sensitive than 240 GeV.
I A contamination of the Higgs sample can lead to a 3σdeviation of the SM parameters.
I Sensitivity to |yνe | down to 6× 10−3 is possible.? Important for understanding the data.? Complementarity to other searches for sterile Neutrinos.
I For other search channels, see: Antusch, OF; arXiv:1502.05915 (2015)
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Thank you for your attention.
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Backup I: Prospects of Sensitivity at the CEPC
L>10m CEPC
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10-2
10-4
10-6
10-8
10-10
10-12
M @GeVD
Q2
L>10m CEPC
50 100 150 200 250
10-1
10-2
10-3
10-4
10-5
10-6
10-7
M @GeVD
ÈyÈ
Direct searches
Z pole search 2Σ: ÈyÈ= ÚΑ yΝΑ2 , Q2=ÚΑÈΘΑ
2
Higgs ®WW 1Σ: ÈyÈ= ÚΑ yΝΑ2 , Q2=ÚΑÈΘΑ
2
e+e-® h +MEHTL 1Σ: ÈyÈ=ÈyΝe È, Q2=ÈΘe
2
e+e-® lΝlΝ* 1Σ: ÈyÈ=ÈyΝe È, Q2=ÈΘe
2
Other
Precision constraints: ÈyÈ= yΝe2 + yΝΜ
2 , Q2=ÈΘe2+ÈΘΜ
2
Precision constraints: ÈyÈ=ÈyΝΤ È, Q2=ÈΘΤ
2
’’Unprotected’’ type-I seesaw
Antusch, OF; arXiv:1502.05915 (2015)
∗ Preliminary estimate using statistical uncertainty only.
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Backup II: Higgs Boson Branching Ratio into Neutrinos
I From “indirect” tests andDelphi.
I O(1) branching ratiopossible.
⇒ Possible effect on Higgsdecay rates into StandardModel particles.
i=1«Θe
i=3«ΘΤ
i=2«ΘΜ
DELPHI
0 20 40 60 80 100 12010-6
10-5
10-4
0.001
0.01
0.1
1
M @GeVD
BrHh®ΝiNL
Antusch, OF; arXiv:1502.05915 (2015)
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Backup III: Cross sections for SM background
Final state σSM@240 GeV σSM@350 GeV σSM@500 GeV
bb̄νν 146.492 134.614 183.594cc̄νν 88.0172 73.7956 82.7041jjνν 528.8 463.1 500.3bb̄bb̄ 81.2629 47.6152 25.5571bb̄cc̄ 146.566 87.6518 51.6446bb̄jj 6820.6 4259.5 2537.8bb̄e+e− 2080.87 2500.82 2920.9bb̄τ+τ− 34.1905 19.7975 11.0619cc̄τ+τ− 25.2553 15.0695 9.15227jjτ+τ− 116.0 72.4 37.6τ+τ−νν 235.89 163.851 119.989single top 0.012 63.3 1092tt̄ — 322. 574.
All cross sections in fb.
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Backup IVa: High Energy Physics Time Scales
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