Maverick Top Partners 1 with a Dark U(1) Based on arXiv:1904.05893, - - PowerPoint PPT Presentation

Maverick Top Partners1 with a Dark U(1)

Based on arXiv:1904.05893, Jeong Han Kim, Samuel D. Lane, Hye-Sung Lee, Ian M. Lewis, Matthew Sullivan Matthew Sullivan

University of Kansas

5/6/2019

1We thank KC Kong and Doug McKay for the term ‘maverick top partner’

The Typical Top Partners

Top and top partner mass eigenstates will be mixtures of SM-like top and new vector like quark (VLQ) Common in composite Higgs and Little Higgs models VLQ will typically be SU(2) singlets or doublets VLQ is still an SU(3) triplet

Production and Decay Processes of Typical Top Partners

Pair production via QCD processes; depends only on mass

T T T T T T q q

Single production via EW processes; involves mixing and model details

b T u d W + b T d u W +

Typically decays via electroweak (EW) channels, exact branching ratios depends on model details

t h1 T t Z T b W + T

Harsh Experimental Limits

CMS: J. High Energ. Phys. (2018) 2018: 177 ATLAS: Phys. Rev. Lett. 121, 211801

LHC hasn’t seen any top partners! Pair production limits rules out MT 1.1 − 1.4 TeV But: limits are for typical electroweak decay channels

Getting Around Electroweak Decays

‘Maverick’ top partners decay predominantly via channels

• ther than T → Zt, T → ht, and T → bW

Most Many ideas in the literature: gluons, photons, new scalar particles Our idea: dark photon (and dark higgs) decays, T → γdt and T → hdt

t h2 T t γd T

See also T. Rizzo’s talk

Dark Photon Crash Course

Dark matter might interact through new short-ranged forces New fields, dark matter or otherwise, might be charged under such a U(1)d A kinetic mixing term can mix the SM U(1)Y and U(1)d bosons: L ⊃

ε′ 2 cos ˆ θW B′ d,µνB′µν

The new ‘dark photon’ gets mass from a dark higgs mechanism For very small mixing, the dark photon inherits couplings to SM fields proportional to electromagnetic charge

Decays of the Maverick Top Partner: Quick Version

VLQ is charged under dark U(1) VLQ and SM-like top mix with a mixing angle θ Using the Goldstone equivalence theorem, we can get the widths to the different final states Γ(T → b/t + W /Z/h) ∼ sin2 θ M3

T

v2

EW

Γ(T → t + γd/hd) ∼ sin2 θ M3

T

v2

d

We examine dark photon masses Mγd 10 GeV, naturally expect comparable vev vd 10 GeV

Γ(T→t+γd/hd) Γ(T→t/b+W /Z/h) ∼

• vEW

vd

2 O(100) Dark decays can easily dominate by orders of magnitude.

Benchmark Model Field Content and Charges

SU(3) SU(2)L Y Yd t1R 3 1 2/3 bR 3 1

• 1/3

QL = t1L bL

• 3

2 1/6 Φ 1 2 1/2 t2L 3 1 2/3 1 t2R 3 1 2/3 1 Hd 1 1 1 SM-like quarks t1R, bR, and QL t2R, t2L with same charges is a singlet VLQ Dark higgs Hd and SM-like higgs Φ for symmetry breaking in dark and electroweak sectors, resp.

Maverick Top Partner Production

σ []

• =

/ + [θ

]=

/ + [θ

]=

/ + [θ

]=

/ + [θ

]=

[]

Same story as a typical top partner Pair production depends on mass only Single production is determined by top sector mixing

Maverick Top Partner Dark Decays

• 500

1000 1500 2000 5 10 50 100 500 1000

[]

• []

(⟶ + ) + (⟶ + γ) = γ = ϵ =

• = =

γ = ϵ =

⟶ ⟶ ⟶ ⟶ γ ⟶

[]

Summary and Discussion

Current experimental limits strongly constrain mass of typical top partners Maverick top partners with dark decays reopen the low mass region New collider signatures for maverick top partner New avenue for dark photon searches

See next talk by Sam Lane for details on the dark photon side