GAMBIT results and prospects for EDM studies Martin White
GAMBIT results and prospects for EDM studies
Martin White
(EDMs for beyond-SM physics studies)
Martin White
Opening remarks•We strongly suspect that the SM of particle physics cannot
be the final answer•We discovered the last piece of the SM in 2012 (the Higgs
boson) at the LHC•We've been searching for beyond-SM physics for nearly a
decade now
Martin White
How to find BSM physics at the LHC● There are two main ways to uncover evidence for new physics
1) Search directly: look for new particles being produced
● Look for functions of four vectors that discriminate between SM and SUSY
● Cut away the SM background as much as possible without hurting the expected signal
● Or look for bumps over SM expectation
2) Measure SM processes very precisely
● New physics can enter via loop diagrams
● Measuring SM processes checks consistency but also reveals new physics at high scales
What have we found?
Martin White
No evidence for BSM physics• There is no current evidence for BSM physics in ATLAS or CMS,
neither in SUSY-type searches, nor resonance searches• Anomalies come and go, and some are at the 3-4 sigma level•No SM measurement has generated sustained excitement so far• Except precision flavour measurements at LHCb which show
significant anomalies (seen also at flavour factories)
Martin White
Stupid conclusion 1
•Wrong, surely. It can't explain gravity, dark matter, flavour, the matter-antimatter asymmetry, dark energy, inflation, the low Higgs mass (unstable under radiative corrections), etc, etc
Martin White
Stupid conclusion 2
•Wrong. See later GAMBIT results for proof, but plenty of natural SUSY models would have slipped under the radar of current searches
Martin White
Stupid conclusion 3
•Wrong. GAMBIT results show that plenty of models with light particles are slipping under the radar of current searches.
Martin White
What we should be doing• Surprises are still likely at the LHC•We should be looking to combine insights from the LHC with
every other experiment that can test BSM physics• If the new physics really is at high energy scales, we should be
pursuing other experimental programs, but the results still need to be compared with LHC and other results
Martin White
Martin White
Isn't this an EDM workshop?• EDM measurements could be crucial in discovering the next
theory of particle physics•GAMBIT studies that include a detailed treatment of EDM
constraints would be amazing• It is only for certain sorts of models that combined studies
make sense however
Martin White
Outline of the rest of the talk• I will present promising avenues for GAMBIT EDM projects•What does GAMBIT currently say about those models?•How do collider constraints work in GAMBIT?•What work needs to be done to do interesting EDM+X studies
with GAMBIT?
Martin White
Disclaimer•Much of this material is new to me, and I've only had time to
do a quick dump based on the literature• This is a “let's think about X talk”, not a “we have already
thought about X” talk!
Martin White
EDMs and BSM physics models•CPT theorem says that the SM is invariant under the
combined C, P and T transformation•CP is violated in flavour-changing weak interactions, given by
complex phases in the CKM matrix (constrained by studies of K and B meson properties)•With symmetric initial conditions, the observed matter-
antimatter asymmetry requires extra sources of CP violation• EDM searches provide powerful probes of these extra sources
Martin White
arXiv:1303.2371
One approach to BSM EDMs•Write a general effective field theory (EFT) that extends the
SM with extra CP-violating dimension-six operators
• This is matched onto low-energy hadronic and atomic parameters relating to the EDMs• The EFT provides a bridge between atomic, nuclear and
hadronic matrix elements, and the fundamental CP-violating terms; any given BSM scenario will map to the EFT.
Martin White
arXiv:1407.1064
EDMs and supersymmetry (SUSY)• SUSY: A hypothesised
symmetry that connects fermions and bosons• Lack of knowledge of
SUSY breaking → 105 a priori unconstrained parameters in the simplest theory
Lots of room for extra CP violation!
Option (3): Supersymmetry
EDMs and SUSY• In the MSSM, low fine-tuning plus Higgs mass of 125 GeV →
significant stop mixing• This tends to enhance possible EDMs• “Natural SUSY” models assume that only the stops and/or
electroweakinos are within reach of the LHC• These are a nice scenario to analyse, otherwise things get
very complicated indeed
Martin White
arXiv:1612.08090
Typical diagrams for fermion EDMs
Martin White
arXiv:1612.08090
EDM measurements → constraints on stop sector!
Martin White
arXiv:1612.08090
Also get constraints on EWino sector
Martin White
arXiv:1612.08090
GAMBIT SUSY results
Example GAMBIT results (MSSM7)
● Global fit of MSSM7 with lots of data (LHC+LEP Higgs, LHC+LEP sparticle searches, Planck relic density, Fermi-LAT Pass 8, IceCube 79 string data, direct DM searches (LUX, Panda-X, PICO, Xenon100, SuperCDMS, Simple), g-2, 59 results from Belle, BaBar and LHCb, strong coupling, top mass, nuclear matrix elements, local DM density
arXiv:1705.07917
Martin White + GAMBIT collaboration + Rose Kudzman-Blais + Matthias Danniger
arXiv: 1809.02097
Included constraints
Source: Anders Kvellestad
ColliderBit
•Handles LHC and LEP limits• LEP: complete recast of sparticle xsec limits• SUSY & Exotic LHC search limits from real-time MC simulation• LHC Higgs-like resonance search limits from
HiggsBounds+HiggsSignals• Future: new resonance limits
Model independent LHC limits
•Custom parallelised Pythia MC + custom detector sim•Can generate 20,000 events on 12 cores in < 5 s• Then apply Poisson likelihood with nuisance parameters for
systematics•Combine analyses using best expected exclusion• The best you can do without extra public info from the
experiments. CMS are getting better at this: https://cds.cern.ch/record/2242860/files/NOTE2017_001.pdf
LHC EWino results
● In a test of exclusion power, we find no general constraint on the MSSM EW sector from the LHC!
arXiv:1809.02097
Scalar leptoquark models• Leptoquarks are hypothetical particles that can transform
leptons into quarks (and vice versa)• Leptoquark models come with new CP-violating couplings•Recent work has derived the connection between scalar
leptoquark models and the dimension-6 EFT described earlier (I think!)• Leptoquark theories can simultaneously provide EDMs and
explain flavour anomalies!Martin White
arXiv:1809.09114
GAMBIT leptoquark plans• Progress been made on a GAMBIT leptoquark study•We would need to extend ColliderBit to include leptoquark
limits from ATLAS and CMS (probably via digitised exclusion curves)
Martin White
Existing GAMBIT EDM study• J. Cornell, D. Skodras, E.
Stamou, J. Brod are looking into global fits of CP-violating Yukawa couplings with EDM constraints•Constraint shown results
from only varying the u coupling
Martin White
Summary• Suggestion 1: We should implement literature results on EDMs
in EWino-only scenarios and update our current results• Suggestion 2: Add stop sector and do a new study with EDM
plus other constraints• Suggestion 3: we should implement EDM constraints on
leptoquarks for the leptoquark study• Suggestion 4: if we do this via the dim6 SM-EFT, perhaps we
should do a dim6 SM-EFT fit for a bonus paper?Martin White
Summary
Martin White