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Flavourful new physics for precision observables Innes Bigaran, Raymond Volkas

@innesbigaran11

Frontiers in Quantum Matter Workshop: Electric Dipole Moments, November 25-27 2019

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Overview

1. Standard Model and CP symmetry 2. CPV + flavour to extend the SM 3. Example models: scalar LQs 4. Current and future work

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The SM and CP symmetry

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The Standard Model• Quarks combine to produce

mesons and baryons • Leptons and quarks interact via

gauge bosons • Leptons and quarks exist in

different flavours, with different masses

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?

X

1. No direct lepton-quark interaction2. Neutrino masses 3. Dark matter and dark energy4. Matter/antimatter asymmetry (req. CPV)

Notable absences

The Standard Model

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▪︎ Similarities and differences between different types of quarks and leptons

▪︎ Flavours have different Higgs couplings: ▪︎ different particle masses

▪︎ The flavour puzzle:▪︎ Why so many “free-parameters”?▪︎ Why only 3 families?▪︎ Relationships between masses,

couplings etc for different generations

Up-type quarks

u ds

c b

t

e 𝜇𝜏

Down-type quarks

Charged leptons

Flavour Physics in the SM

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By delving into flavour, we aim to understand the connections between SM and a more complete picture of nature, including CPV

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BSM and CPV

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C and CP and their violationState A ! State B

State A ! State B

��A ! B

�6= � (A ! B)

� (A ! L) 6= ��A ! R

�

C action

CP violation

C violation

Where L and R are the left- and right-handed projections of the same field (mix via the Higgs)

L � gABL+ g0ABR+ h.c.

hHi

Example:

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g

g0⇤

iM / 116⇡

gg0⇤

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C and CP and the CKM

We have some of this in the SM, via the complex terms in the quark CKM mixing matrices— which allow for quark-flavour changing interactions

Not enough to explain matter/antimatter asymmetry

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(See other talks i.e Csaba Balasz)

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CPV in the SM: Strong CP problem

L � ✓ g2

32⇡2✏µ⌫↵�G

aµ⌫G

a↵�

▪︎ CP-odd, total-derivative term in the QCD Lagrangian

▪︎ Derivative terms don’t enter the equations of motion, within PT regime

▪︎ This term has non-perturbative effects

/ ✓ [@µJµ]

Coupling phase mismatch in the chiral EFT Lagrangian —> EDM of the neutron! From experimental constraints on this, SM needs a very small theta ~~10^(-11)

Very fine-tuned, or see work by others on Axions, massless quarks etc….

WHY?

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eEDMs as a probe of NP

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Very broad sub-categories which are “indicative” but also can be quite disheartening for model-builders

Google images: “sad electron”

Sauer, Devlin 2017

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Scalar LQ Models

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Scalar LQ models in context

• Direct coupling between SM quarks and leptons

• Flavour violation in BSM theories ✴ Flavour anomalies? ✴ Neutrino mass?

• CPV possible with complex Yukawa couplings (recall earlier example)

LQ

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Q

L

Q

L

LQ

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Scalar LQ: EDM generation

• Having 2 leptoquark interactions allow for a coupling phase difference —> CPV

• Focus on single-loop specific model constraints for this arXiv:1804.01137

• Revisit with leading-order EDM constraints on the set of scalar LQ models

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https://arxiv.org/pdf/1407.1064.pdf

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Reference for phenomenology

Chupp, Ramsey-Musolf ArXiv:1407.1064

General

More specific

Aim to provide a clear reference on EDM contributions from each of the Scalar LQ models

Thank you to Sacha Davidson and Jordy de Vries for useful discussion on this

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Related precision observable: lepton (g-2)

Bigaran, Volkas , arXiv 1912.xxxx Manuscript in preparation

A bit simpler than the eEDM calculations

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Problem: • Deviation between SM and experiment, • 2.5 sigma for electron, 3.6 sigma for muon but opposite sign —> flavour specific BSM?

Solution:

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Summary

1. Flavour physics has useful applications on the precision frontier

2. Scalar LQs are very neat BSM models 3. (g-2) is a good way to start exploring these models 4. EDM summary tables, developed by

phenomenologists, can help experimentalists make useful conclusions

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