The Lifetime Frontier: Search for New Physics with Long-Lived - PowerPoint PPT Presentation

Constraints from µ → e γ , µ to e conversion; Axionless solution to the strong CP problem . ⇓ From µ → e γ , µ to e conversion : g Sl < 10 − 4 Axionless solution to the strong CP problem : Constraint from the so-far absence of the neutron electric dipole moment: ¯ θ < 10 − 10 . Our solution: ¯ θ ∝ m ν . Small because neutrino masses are small. Deep connection between neutrino physics and QCD . g Sq < g Sl < 10 − 4 P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Constraints from µ → e γ , µ to e conversion; Axionless solution to the strong CP problem . ⇓ From µ → e γ , µ to e conversion : g Sl < 10 − 4 Axionless solution to the strong CP problem : Constraint from the so-far absence of the neutron electric dipole moment: ¯ θ < 10 − 10 . Our solution: ¯ θ ∝ m ν . Small because neutrino masses are small. Deep connection between neutrino physics and QCD . g Sq < g Sl < 10 − 4 Lightest mirror fermions are long-lived! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Lepton-number violating signals at high energy: Like-sign dileptons from the decays ν R ν R ( q ¯ q → Z → ν R ν R ) . Remember ν R : Majorana! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Lepton-number violating signals at high energy: Like-sign dileptons from the decays ν R ν R ( q ¯ q → Z → ν R ν R ) . Remember ν R : Majorana! ν Ri → e M Rj + W + followed by e M Rj → e Lk + φ S . P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Lepton-number violating signals at high energy: Like-sign dileptons from the decays ν R ν R ( q ¯ q → Z → ν R ν R ) . Remember ν R : Majorana! ν Ri → e M Rj + W + followed by e M Rj → e Lk + φ S . The appearance of like-sign dileptons ( e − e − , µ − µ − , τ − τ − , e − µ − , ... ) could be at displaced vertices > 1 mm . P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Search for mirror quarks QQ ( 1 S 0 ) gg q M R → q L + φ S . Example:: 0.04 Typical decay length ≫ Hadronization length 0.03 ∼ O (1 fermi ) (pb) 0.02 Formation of QCD bound states q M q M and Hybrid Mirror mesons:¯ 0.01 q M q get formed first mesons ¯ before they decay! 0.00 200 300 400 500 600 700 800 900 1000 m Q (GeV) P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Search for mirror quarks Mirror-meson decays P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Search for mirror quarks Mirror-meson decay lengths: Displaced Vertices > O ( cm ) for g Sq < 10 − 4 . Mirror meson decay length ( = 10 3 ) 10 3 CMS's Silicon Strip Tracker radius 10 2 decay length (cm) 10 1 10 0 m q M = 200 GeV 10 1 m q M = 400 GeV m q M = 600 GeV 10 2 m q M = 1000 GeV 10 4 10 3 g Sq P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Conclusions The EW- ν R model (mirror fermion model) is one of the class of models where characteristic signatures are Long-lived particles. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Conclusions The EW- ν R model (mirror fermion model) is one of the class of models where characteristic signatures are Long-lived particles. Long live the Lifetime Frontier! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Keep in mind... New Physics with Exotic and Long-lived Particles: A joint ICISE-CBPF workshop July 1-6, 2019, Quy Nhon, Vietnam P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

https://www.icisequynhon.com/conferences/2019/ICISE-CBPF- Workshop/ P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Thank you for staying awake P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Backup slides P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

What kind of new physics could there be hiding in the yet-unexplored regions of the detectors? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

What kind of new physics could there be hiding in the yet-unexplored regions of the detectors? Perhaps it is time to switch gear, going from theory-driven searches to signature-driven searches. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

What kind of new physics could there be hiding in the yet-unexplored regions of the detectors? Perhaps it is time to switch gear, going from theory-driven searches to signature-driven searches. Most importantly: Motivations, Predictability and Detectability! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The question then is why we have not seen any new physics signals yet if they are there. The answer to the aforementioned question might be the possibility that we have ”missed” new physics signals due to the fact that most experimental search algorithms focus mainly at prompt decays with decay lengths less than 1 mm and at stable particles. Long-lived particles (LLP) can be defined as (BSM) particles which decay into SM particles or give up all their energies inside the detector acceptance of the present LHC detectors LHCb, CMS, ATLAS as well as the proposed detectors MilliQan, MoEDAL, MATHUSLA, etc...Experimentalists and theorists got together recently to form The LHC LLP Community, a CERN initiative, which is growing and which hold regular workshops P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

What kind of new physics could there be hiding in the yet-unexplored regions of the detectors? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

What kind of new physics could there be hiding in the yet-unexplored regions of the detectors? Giant Isopod P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

A laundry list of BSM models with long-lived particles: R-parity violating SUSY; Split SUSY; L-R symmetric model,...,Neutrino mass P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

A laundry list of BSM models with long-lived particles: R-parity violating SUSY; Split SUSY; L-R symmetric model,...,Neutrino mass Why is ”neutrino mass” underlined? Because that is P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

A laundry list of BSM models with long-lived particles: R-parity violating SUSY; Split SUSY; L-R symmetric model,...,Neutrino mass Why is ”neutrino mass” underlined? Because that is CLEARLY THE ONLY EVIDENCE OF BSM PHYSICS WE HAVE SO FAR! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Most compelling way to generate tiny neutrino masses: seesaw mechanism m ν = m 2 D / M R with m D ( Dirac ) ≪ M R ( Majorana ) P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Most compelling way to generate tiny neutrino masses: seesaw mechanism m ν = m 2 D / M R with m D ( Dirac ) ≪ M R ( Majorana ) ⇒ Existence of right-handed neutrinos. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Most compelling way to generate tiny neutrino masses: seesaw mechanism m ν = m 2 D / M R with m D ( Dirac ) ≪ M R ( Majorana ) ⇒ Existence of right-handed neutrinos. Where are they? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Most compelling way to generate tiny neutrino masses: seesaw mechanism m ν = m 2 D / M R with m D ( Dirac ) ≪ M R ( Majorana ) ⇒ Existence of right-handed neutrinos. Where are they? Do they interact with W’s and Z or not? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Right-handed neutrinos are usually thought of as sterile under the SM gauge group. They don’t interact with W and Z. Usually very heavy and very, very hard to detect. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Right-handed neutrinos are usually thought of as sterile under the SM gauge group. They don’t interact with W and Z. Usually very heavy and very, very hard to detect. Main motivations for that assumption: Gauge extensions of the SM (Left-Right symmetry, Grand Unification...) So far no evidence. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Right-handed neutrinos are usually thought of as sterile under the SM gauge group. They don’t interact with W and Z. Usually very heavy and very, very hard to detect. Main motivations for that assumption: Gauge extensions of the SM (Left-Right symmetry, Grand Unification...) So far no evidence. Why should they be so??? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

What IF? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Right-handed neutrinos are non-sterile. They interact with W and Z. Their masses M R are proportional to Λ EW ∼ 246 GeV . P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Right-handed neutrinos are non-sterile. They interact with W and Z. Their masses M R are proportional to Λ EW ∼ 246 GeV . Advantages? A testable scenario! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Right-handed neutrinos are non-sterile. They interact with W and Z. Their masses M R are proportional to Λ EW ∼ 246 GeV . Advantages? A testable scenario! Experimental: They are ”light” (LHC-accessible) and have typical electroweak production cross sections ⇒ Direct test of seesaw. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

ν R s are parts of MIRROR FERMIONS, the lightest of which are long-lived P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

ν R s are parts of MIRROR FERMIONS, the lightest of which are long-lived Theoretical: Deep connection between neutrino masses and the strong CP problem, among others. With mirror fermions, one can now study EW phase transitions non-perturbatively on a lattice: Important for cosmology! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

ν R s are parts of MIRROR FERMIONS, the lightest of which are long-lived Theoretical: Deep connection between neutrino masses and the strong CP problem, among others. With mirror fermions, one can now study EW phase transitions non-perturbatively on a lattice: Important for cosmology! How does one construct a model in which M R ∝ Λ EW ∼ 246 GeV with ν R carrying SM quantum numbers? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Lee and Yang on Parity Violation: ”If such asymmetry is indeed found, the question could still be raised whether there could not exist corresponding elementary particles exhibiting opposite asymmetry such that in the broader sense there will still be over-all right-left symmetry..” PR104, 254, October 1956. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model (pqh, 2007) What is it? What has it accomplished? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model (pqh, 2007) What is it? What has it accomplished? Non-sterile ν R ’s? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model (pqh, 2007) What is it? What has it accomplished? Non-sterile ν R ’s? Members of right-handed mirror lepton doublets of � ν M � ν L � � SU (2), l M R R = ; SM: l L = e M e L R P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model (pqh, 2007) What is it? What has it accomplished? Non-sterile ν R ’s? Members of right-handed mirror lepton doublets of � ν M � ν L � � SU (2), l M R R = ; SM: l L = e M e L R M R ∝ Λ EW ? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model (pqh, 2007) What is it? What has it accomplished? Non-sterile ν R ’s? Members of right-handed mirror lepton doublets of � ν M � ν L � � SU (2), l M R R = ; SM: l L = e M e L R M R ∝ Λ EW ? From the VEV of a triplet χ = ( χ 0 , χ + , χ ++ ) and Higgs field ˜ lepton-number violating mass term L M = g M l M , T χ l M σ 2 τ 2 ˜ R . R P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model With � χ 0 � = v M < Λ EW , right-handed neutrino Majorana mass M R = g M v M ⇒ M Z / 2 < M R < O (Λ EW ∼ 246 GeV ) : Main point. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model With � χ 0 � = v M < Λ EW , right-handed neutrino Majorana mass M R = g M v M ⇒ M Z / 2 < M R < O (Λ EW ∼ 246 GeV ) : Main point. Wait! Isn’t it too complicated? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model With � χ 0 � = v M < Λ EW , right-handed neutrino Majorana mass M R = g M v M ⇒ M Z / 2 < M R < O (Λ EW ∼ 246 GeV ) : Main point. Wait! Isn’t it too complicated? If M R comes from symmetry breaking, it’s unavoidable to have a Higgs structure larger than that of the SM. E.g. 126 of SO(10) or a triplet ∆ R of L-R model. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model m D ? P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model m D ? From the VEV of a complex singlet Higgs field φ S . Lepton-number conserving term L S = − g Sl ¯ l L φ S l M R + H . c . m D = g Sl v S where � φ S � = v S . Crucial in the discussion of the phenomenology of the model and the strong CP problem P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

The EW- ν R model � ν M � l M R R = : Anomaly cancellation → e M R � u M � Mirror quarks: q M R R = d M R P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model Gauge group: SU (3) C × SU (2) W × U (1) Y . Notice the subscript W instead of L. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model Gauge group: SU (3) C × SU (2) W × U (1) Y . Notice the subscript W instead of L. � � � � ν L u L Fermions: SM: l L = ; q L = ; e R ; u R , d R ; Mirror: e L d L � ν M � � u M � l M R ; q M R ; e M L ; u M L , d M R = R = L . e M d M R R P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model Gauge group: SU (3) C × SU (2) W × U (1) Y . Notice the subscript W instead of L. � � � � ν L u L Fermions: SM: l L = ; q L = ; e R ; u R , d R ; Mirror: e L d L � ν M � � u M � l M R ; q M R ; e M L ; u M L , d M R = R = L . e M d M R R Scalars: * Doublet Higgs fields (similar to 2HDM): Φ SM 1 ( Y / 2 = − 1 / 2), Φ SM 2 ( Y / 2 = +1 / 2) coupled to SM fermions, and Φ M 1 ( Y / 2 = − 1 / 2), Φ M 1 ( Y / 2 = +1 / 2) coupled to mirror fermions √ √ with � Φ SM 2 , 0), � Φ SM 1 � = ( v 1 / 2 � = (0 , v 2 / 2) and √ √ � Φ M 1 � = ( v M 2 , 0), � Φ M 2 � = (0 , v M 1 / 2 / 2). P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model *Triplet Higgs fields:  χ 0 ξ + χ ++  χ − ξ 0 χ + χ =   χ −− ξ − χ 0 ∗ ξ ( Y / 2 = 0) = ( ξ + , ξ 0 , ξ − ) with � χ 0 � = � ξ 0 � = v M in order to preserve Z cos 2 θ W at tree level. Custodial Symmetry (that guarantees M 2 W = M 2 i + v M , 2 i =1 , 2 v 2 ) + 8 v 2 M = (246 GeV ) 2 . Here ( � i P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model *Triplet Higgs fields:  χ 0 ξ + χ ++  χ − ξ 0 χ + χ =   χ −− ξ − χ 0 ∗ ξ ( Y / 2 = 0) = ( ξ + , ξ 0 , ξ − ) with � χ 0 � = � ξ 0 � = v M in order to preserve Z cos 2 θ W at tree level. Custodial Symmetry (that guarantees M 2 W = M 2 i + v M , 2 i =1 , 2 v 2 ) + 8 v 2 M = (246 GeV ) 2 . Here ( � i *Singlet Higgs fields: φ S : Important scalars connecting the SM and Mirror worlds. Crucial in the search for mirror fermions → displaced vertices. Crucial for the strong CP problem. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model *Triplet Higgs fields:  χ 0 ξ + χ ++  χ − ξ 0 χ + χ =   χ −− ξ − χ 0 ∗ ξ ( Y / 2 = 0) = ( ξ + , ξ 0 , ξ − ) with � χ 0 � = � ξ 0 � = v M in order to preserve Z cos 2 θ W at tree level. Custodial Symmetry (that guarantees M 2 W = M 2 i + v M , 2 i =1 , 2 v 2 ) + 8 v 2 M = (246 GeV ) 2 . Here ( � i *Singlet Higgs fields: φ S : Important scalars connecting the SM and Mirror worlds. Crucial in the search for mirror fermions → displaced vertices. Crucial for the strong CP problem. *So many Higgs fields? Nothing to be afraid of. Good hunting ground! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model: Precision constraints Fig. 1 and 2 are the 1 σ and 2 σ constraints. ˜ T and ˜ S are the total contributions (mirror fermions plus scalars) after subtracting out the SM contributions. 0.5 0.4 0.3 0.2 0.1 ~ T 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 ~ S P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model: Precision constraints S S and ˜ ˜ S MF are the contributions to S from the scalars (mainly the triplets) and the mirror fermions. 0.6 σ + 1 constraint × σ 2 constraint 0.4 0.2 S ~ S 0 -0.2 -0.4 -0.6 -0.2 0 0.2 0.4 0.6 0.8 ~ S MF P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles ˜ ˜

Summary of the EW- ν R model: Precision constraints 2016 PDG value for ˜ S = 0 . 07 ± 0 . 08 P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model: Precision constraints 2016 PDG value for ˜ S = 0 . 07 ± 0 . 08 Notice that, for a large range of parameters, the contribution to ˜ S S from Triplet scalars is generally negative and large (see the previous figure)! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model: Precision constraints 2016 PDG value for ˜ S = 0 . 07 ± 0 . 08 Notice that, for a large range of parameters, the contribution to ˜ S S from Triplet scalars is generally negative and large (see the previous figure)! If only triplet scalar is present ⇒ very small region of parameter space for ˜ S S is allowed ⇒ fine-tuning problem! The much larger parameter space which allows mass splitting inside the triplet has large and negative values for ˜ S S which need to be cancelled by similar positive amount coming from another sector such as the mirror fermion sector! One cannot play around with triplet Higgs without experimental consequences! P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

0.00 FCC CEPC + ILC - 0.05 PDG - 0.10 S - 0.15 - 0.20 - 0.25 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 β = m' / m Figure: S vs the mass splitting ratio β = m ′ m . The dashed and the dotted lines represent the current precision (PDG) and the projected precision for the ILC and CEPC colliders. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model: 125-GeV scalar There are many choices of parameters which can accommodate the 125-GeV scalar. Some are more SM-like, some are not. P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles

Summary of the EW- ν R model: 125-GeV scalar There are many choices of parameters which can accommodate the 125-GeV scalar. Some are more SM-like, some are not. Some examples on the next slide P. Q. Hung The Lifetime Frontier: Search for New Physics with Long-Lived Particles