1. SUSY Searches at the LHC – Where do we stand?
Smaragda Lola
Dept. of Physics, University of Patras
HEP 2018
Recent Developments on Particle Physics and Cosmology

2. SUSY GUTs have very attractive features (talk by Q. Shafi)
Outline
We know that we need to go beyond the SM, due to
- Neutrino masses & mixing
- Baryon asymmetry in the universe
- Origin of dark matter
- Large number of arbitrary SM parameters (mostly in mass sector)
- Hierarchy problem , especially if further unification exists
SUSY GUTs have very attractive features (talk by Q. Shafi)
However: No signal found at the LHC
Severe constraints on at least the simplest models
(i.e. talks by V, Mitsou and N. Saoulidou)
What lies beyond the simplest models?
- Break unification conditions of minimal schemes &/or
- add new particles and interactions (softer fitting constraints)
W negative (more interesting…) need to simulate in the programme

3. Success of Unification
electric
planets
magnetic
apple
Electromagnetism
Quantum mechanics
Gravity
mechanics
Special Relativity
Quant. ElectroDynamics GR
Weak force
Th. of everything
Electroweak Theory
Grand Unification?
Strong force

4. Combine GUTs, SUSY and Flavour Symmetries
Different predictions in various GUTs
SO(10), SU(4) x SU(2)L x SU(2)R [422]
SU(5), Flipped SU(5) [non-universal sfermion masses]
Can we distinguish different scenarios?
What are the expected sparticle correlations in each scheme?
Several constraints from DM + LHC considerations
What can the LHC and DM tell us on the underlying symmetries?
Will start by briefly reviewing aspects of GUTS, SUSY and flavour symmetries that are useful for our discussion,
And will then proceed to discuss lepton flavour violation in various scenarios.

5. SUSY – new particles and interactions
Minimal SUSY Lagrangian– very simple rule: all SM interactions
+ those where 2 particles are substituted by sparticles
i.e.
Look at Simplest SUSY models first:
- Missing Energy Signature
- LSP as Dark Matter (one of our basic requirements)

6. SUSY has to be broken
Soft SUSY breaking terms

7. The simplest models are too restrictive!
To search for/exclude SUSY unification need to first consider
several alternative possibilities
Problem: Vast number of models
How to distinguish between them?
Try to address at the same time the origin of mass,
combining GUT and flavour symmetries

8. MINIMAL MODIFICATIOS TO SOFT TERM UNIVERSALITY:
Fermion fields in the same 16
2 Higgs fields in different 10 representations

9. Ellis, Mustafaev, Olive, Velasco-Sevilla
Fermions in different representations
2 Higgs fields in different 10 representations

10. Flipped SU(5) - versus SU(5)
Different field assignment in representations – different predictions (i.e. more freedom with stop masses as compared to SO(10), SU(5))

11. 4-2-2 Unification
-Lepton number a 4th color – thus unifying quarks and leptons
-L-R symmetry, but asymmetric also possible
Pati, Salam,
Lazarides, Shafi, King
Antoniadis, Leontaris
Fermions embedded as follows:

12. Correlations between the non-universal soft scalar masses
and DM in different SUSY GUTS – very rich structure
(CMSSM fpr xu,d,5,R = 1 / too restrictive)
SO(10) [and SU(5)]: stop mass tends to become very heavy
Flipped SU(5)]: stop-coannihilations possible
Cannoni, Ellis, Gomez, SL, Ruiz de Austri

13. New signals, including gluino coannihilations!
422: Gomez, SL, Ruiz de Austri, Shafi
New signals, including gluino coannihilations!

14. (s)Fermion hierarchies from flavour symmetries
EVEN MORE FREEDOM : complete 3x3 structure of Mass Matrices
(s)Fermion hierarchies from flavour symmetries
(i.e. Why the top quark mass so much larger?)
Simplest: a LR family symmetry generates the observed hierarchies
Charges such that only 3 generation masses allowed
(0 flavour charges for 3rd generation)
The rest of the terms appear once the symmetry is broken
Frogatt-Nielsen mechanism
W negative (more interesting…) need to simulate in the programme
Similarly for other fermions, including neutrinos

15. After symmetry breaking, Mup

16. SL, Ross

17. Flavour symmetries may also determine soft SUSY terms
break soft term universality even further!
L-R symmetric
SU(5)
L: (1,0,0)
R: (3,2,0)

18. SO FAR
Can identify patterns of soft SUSY-breaking terms at the GUT scale, compatible with DM predictions and LHC spectra
The models predict different spectra for the same LSP mass, connecting possible observations with the underlying unified theory.
In particular, SO(10), SU(5), flipped SU(5) and lead to very different predictions, and are distinguishable in future searches.
Flipped SU(5) and 422 predict stop-LSP coannihilations that are absent in the other groups and can be explored in LHC searches.
422 also predicts light gluinos, and gluino coannihilations.

19. R-violating SUSY
In addition to the Yukawa couplings generating fermion masses
also
- These violate baryon & lepton number
- If simultaneously present, rapid (unacceptable) p decay

20. Choices: X R-parity (SM: +1 , SUSY: -1) Forbids all terms with ΔL, ΔB
LSP: stable, dark matter (DM) candidate
Main Signal: Missing Energy
Other symmetries, allowing only ΔL, or only ΔB
LSP: unstable / do we lose SUSY DM (?)
Signals: Multilepton and/or multijet events
Single sparticle productions possible
For ΔL (LLE, LQD) we look for:
- ΔLi, new final state topologies
-isolated leptons within jets with small missing energy
For ΔB (UUD) bigger difficulties, except for t,b

21. (i) Simplest SUSY models – missing energy
SUSY στο LHC
(i) Simplest SUSY models – missing energy
(ii)ΔL,ΔΒ≠0, rare leptonic/hadronic events
MSSM

22. bonus – small neutrino masses,
[in agreement with data]

23. For very small RPV couplings

24. Large RPV: Single sparticle productions at the LHC
(Dimopoulos, Hall, Dreiner, Ross)

25. Various channels studied at the LHC
45 couplings! (9+27+9)
Various channels studied at the LHC
under the assumption of a single coupling dominance
Typical λ, λ’, λ’’ bounds for sparticle masses of 1 TeV
[λ133, λ’133, λ’’112, λ’’113 smaller]

27. Without such assumptions,
Simple Models
LLE: MSSM pair sparticle productions
Direct decay to 2 LSP Χ0
RPV decay of Χ0
Also presence of neutrinos,
thus limited Missing Energy
[C]MSSM + 1RPV + RGEs
Single coupling dominance
Without such assumptions,
the parametric space has not yet been scanned

28. CMSSM + 1 RPV + simplified models
Dercks et al.,hep-ph/
CMSSM + 1 RPV + simplified models
Such RPV bounds directly translated to limits on other SM extensions: ie scalar leptoquarks, contact interactions
i.e. Altarelli, Ellis, Giudice, SL, Mangano

29. Are these assumption obvious?
Not really…
L-R flavour symmetries (i.e. within SO(10)):
Similar LLE,LQD,UDD (only the generation matters)
w: flavour independent contributions
(Ellis, SL, Ross)
Single coupling dominance not generically valid!

30. Predictions for R-violating operators in different GUTS:
What type of processes favoured in different groups?
(proceed similarly to discussion for fermion mass terms)
L-R symmetric – SO(10):
similar LLE,LQD,UDD (only generation matters)
- Bounds on products of couplings, due to correlations, translated to individual bounds /very restrictive [Ellis, SL, Ross]
-1 coupling dominance disfavoured
- Single sparticle productions disfavoured over MSSM ones, with RPV decays
SU(5) – with U(1) charges chosen to match lepton data
Very different expected correlations
Larger hierarchies and dominance of fewer couplings
Single sparticle productions better accommodated
W negative (more interesting…) need to simulate in the programme 30

31. We need some insight for RPV hierarchies
What can we do:
We need some insight for RPV hierarchies
(in analogy with those for fermion Yukawa couplings)
Many possible channels – which ones to chose?
Neutralinos-charginos couple to all 45 operators
Ideal channels to study simultneously all hierarchies
[Bomark, Choudhury, Kvellestad, SL, Osland, Raklev]

32. Neutralino Decays Have studied
RPV hierarchies as predicted by flavour symmetries
Parametric spaces beyond CMSSM
Bomark, Chourdury, SL, Osland

33. Are chargino RPV decays also relevant?
Bomark, Kvellastad, Osland, SL, Raklev
For Wino or Ηiggsino LSP, chargino direct RPV decays possible
W negative (more interesting…) need to simulate in the programme
Diagrams for LQD (similar for LLE, UUD)

34. LLĒ LQD [ Χ0 -> (llν) ] Energetic leptons, with explicit ΔLi
SU(2): at least 2 different leptons
LQD
Similar to neutralino decays(ljj, vjj) – BUT differ for LQ3D
-Neutralinos: neutrino + jets OR charged lepton + top + jet
-Charginos: charged leptons + jets, neutrinos + top + jet

35. UDD Generically a problem due to huge QCD background
HOWEVER: Very distinct for: U3DjDk
-Neutralino decays always involve a t
-Chargino decays involve 3 down-type quarks (1 always b)
-Moreover: bbj, ttj (για U3D1,2 D3)

36. Gravitino DM compatible with broken Rp!
Very slow decays:
Gravitino interatcions (~1/Mp)
Phase space (light gravit.)
Loops (~ fermion masses)
Neutrino-neutralino mixing
[Takayama, Yamaguchi], [Chemtob, Moreau][Buchmuler, Covi, Hamaguchi, Ibarra, Yanagida]
[SL, P. Osland, A. Raklev]

37. NEED TO EXTEND THE SM & SUSY looked nice in this respect!
CONCLUSIONS
NEED TO EXTEND THE SM & SUSY looked nice in this respect!
No sign of SUSY so far. BUT:
There is an abundance of viable models
with or without RPV
Only the simplest ones have been studied extensively
We cannot yet exclude SUSY without
properly investigating
these additional opportunities
W negative (more interesting…) need to simulate in the programme 37