Vectorlike Confinement and its Signatures at the LHC

Can Kılıçwork done with Takemichi Okui and Raman Sundrum

arXiv: 0906.0577

Introduction

• LHC coming, expectations shaped by the hierarchy problem.

• Known solutions constrained by experiment. Possible scenarios.

• Concept of meso-tuning. Impact on discovery potential at the LHC. Part of NP may be accessible. Need guiding principle.

• Theoretical simplicity / safety from PO at low energy. (rich phenomenology at higher energies)

• Define Vectorlike Confinement: – new vectorlike fermions– a new strong gauge force – (very weak interactions relevant for decay)

• LHC phenomenology dominated by hyperhadrons.

Attractive features

• Precedent: Analogy to QED + low energy QCD. Signatures: pair production, resonance. can decay, is stable up to weak interactions. Mirrored in VC.

• Safety: “Gauge-mediation” is flavor blind. Mass scale set by confinement, separated from EWSB.

• Rich phenomenology: A minimal theory naturally gives rise to an array of distinct collider signatures (multi GB, CHAMPs, other exotica), some new features.

Deja-Vu?

• Not TC. Different motivation / structure / signatures.

• TC must have chiral fermions for EWSB, which impacts PEW.

• Generating masses leads to flavor problems in TC.

• Connected in the bigger picture?

• Can use same tools (analog computer)

• VC as a strawman model

Outline

• Theoretical Structure• Phenomenological Lagrangian• Representative Case Studies

– A subtlety in the minimal model– CHAMPs and EW gauge bosons– Multijets– R Hadrons– DM, cascades, other possibilities

• Conclusion

A Brief History of QCD

• Begin by strongest interactions (u,d only)• Focus on ,ρ• Confinement, flavor symmetry

• (Pseudo) Goldstones:

transform in adjoint of flavor group. ’s and baryons stable• ρ lightest state, decays to

2 , becomes special once we add U(1)em

A Brief History of QCD

Consequences of turning on U(1)em

(qu = 2/3 , qd = -1/3)

• ρ is the lightest meson which can be interpolated by – ρ/γ mixing– resonant production

• charges–

• anomalous,

• Both up and down number still conserved, stable, turn on weak interactions. (4-fermion operators)

• Up and down numbers no longer conserved, baryon number still conserved.

• Need light particles for to decay, introduce non-strongly interacting particles.

induces as well as neutron decay (proton stable)

A Brief History of QCD

Could Lightning Strike Twice?From a simple UV theory to rich IR Physics

• Hypercolor: SU(N) gauge theory with F vectorlike flavors in the fundamental representation. Scale ΛHC.

(F chosen such that theory confines) • Flavor symmetry

Conserved number for each flavor. • (Pseudo)Goldstones:

we consider• and baryons stable at this point• is the lightest meson, decays

to 2 , becomes special as we turn on SM.

Could Lightning Strike Twice?From a simple UV theory to rich IR Physics

• Turn on

hyperfermions charged under SM. • SM breaks many of the flavor numbers, introduce

“species” of hyperfermions. (e.g. color triplet)• Changes running of SM couplings,

for one species in to avoid QCD Landau-pole in the UV.

• interpolated by can mix with SM gauge bosons, resonant production.

• charges. • Radiative masses for• Anomaly of can decay with zero species

number ( - short)• Species number unbroken. Leads to stable .

Could Lightning Strike Twice?From a simple UV theory to rich IR Physics

• - long stable, SM charged. UV physics analogous to weak interactions can decay them to non-hypercolored particles (SM).

or

breaks species numbers.• Straightforward to break hyperbaryon

number as well. Model dependent.• Models constrained, there must exist

a SM final state with matching quantum numbers. (simple choice: GUT-like representations)

Constraints (I)

• Vectorlike fermions: Confinement preserves vector part of flavor symmetry, SM unaffected. Choose quantum numbers such that Yukawa terms with the SM Higgs forbidden, PEW safe.

• “Gauge mediation” means that flavor violating effects from renormalizable part of the VC theory suppressed relative to the SM by loop factor.

• Nonrenormalizable operators can induce flavor violating SM operators. For generic coefficients, need M ~ O(104) TeV. For special flavor structure, M can be anything consistent with EFT description.

Phenomenological Lagrangian The

• Not literal EFT. Large N estimates.• Mixing/production:

where• Shift induces• Production from gluons• Dominant decay

from where• Rare decays

Phenomenological LagrangianMasses

Three sources of mass:

• SM gauge groups break the flavor symmetry

• Fundamental hyperquark masses

• From EWSB

Phenomenological Lagrangian-short and -long

• Chiral anomalies induce

those with no net species numbers decay to a pair

of gauge bosons. Here

• Higher dimensional operators decay with nonzero species number.

Phenomenological Lagrangian-long Decay Length

• Current-current decays suppressed by fermion masses

• Scalar-scalar decays are less suppressed

• Prospects for visibility tied to flavor structure.

Phenomenological LagrangianOverview

Constraints (II)• Many exotic states with SM charges. Ocean bottom searches

for charged particles:Plenty of room between bounds from cosmology and flavor.

• Fermion compositeness:

worst case is eeqq , OK as long as• -short decays at the Tevatron OK as long as • Resonant production and decay to SM: electroweak has

too small cross section/branching fraction, color is interesting – search strategy in a few slides.

• Singlet are axions. Forwe have (safe for SN cooling, beam dump)

decay not observablenot observable (BF too small)

A Few Simple ModelsSU(2) Doublet

• representation• Spectrum contains

with• , bleak collider phenomenology• There is a special that could keep the from decaying

because axial current is odd:• MDM candidate?• If decays, adding a singlet gives more generic structure,

without losing any features.

A Few Simple ModelsWhat a Singlet Can Do

• SM charge assignment:• The singlet as “strange”

• Masses (singlet is axion):

• After EWSB:

• -strahlung at LEP?

A Few Simple ModelsWhat a Singlet Can Do

• Resonances:

• Short-lived pions:

Lepton-rich, very good reconstruction in the channel.• Long lived pions

decays through the current operator (heavier states preferred).

When suppression scale is low, prompt or displaced same-sign tau-pair +MET as well as , otherwise CHAMP pairs.

too softto see

• Triggers like a muon.

• Experimental handles: curvature, dE/dx,ToF

• Tevatron Limits dictate

• Distributions

• more advanced

analysis by

Chen & Adams

(200 pb-1 at 10 TeV)

A Few Simple ModelsCHAMPs

• Associated production gives mode.(BF ~35% in CN)

• Resonant as well as nonresonant channels. (~65% in CC)

(GMSB searches) – work in progress. (~32% in CN)

• Distributions

• Hyperbaryon decay

A Few Simple ModelsMulti-photons

A Few Simple ModelsSU(3) Triplet

• Color triplet gives rise to color octet , .• Without any electroweak charges, can be as light as

300GeV. Possibly in Tevatron data, not excluded, discoverable. still easy at LHC, harder.

A Few Simple ModelsSU(3) Triplet + Singlet

• Add a singlet• Spectrum

• Decay modes

• Axion mode interesting but unobservable

A Few Simple ModelsR-Hadrons

• Triplet collider stable or decays through current-current operator, 3rd generation leptoquark

• R-hadrons will be charged with O(1) probability. Resonance easier to observe compared to EW model.

• 4 R-hadrons (leptoquarks) if g’ pair produced – fb cross section

• Hyperbaryon decay

A Few Simple ModelsSpectators

• DM candidates generic in VC models.• Exotic species have a much harder time decaying• and make up DM candidate• can decay to

“Squark” pair production with subsequent decay to “LSP”• More general cascades

Conclusions

• VC: New confining gauge interactions with vectorlike matter are theoretically simple and generic.

• “Gauge-mediated” setup with vectorlike matter ensures safety from low energy precision tests.

• Vector states can be resonantly produced, decay to naturally light PGB’s.

• Scalars have short-lived and collider stable species. – Short-lived scalars decay to a pair of SM gauge bosons. 4 GB

final states can be spectacular.– Long lived scalars appear as CHAMPs / R-hadrons. Resonance

reconstruction possible. Decays into heavy flavors can be preferred. (leptoquarks, di-taus, di-tops…)

• Unbroken species number or spectators can give DM candidates. Cascades possible.