Lectures on BSM and Dark Matter Theory (1St Class)

Lectures on BSM and Dark Matter theory (1st class)

Stefania Gori UC Santa Cruz

15th annual Fermilab - CERN Hadron Collider Physics Summer School August 10-21, 2020 Overview

Chapter 1: Introduction: The Standard Model and its open problems TODAY

SUSY theories.c Direct & indirect searches of SUSY particles Chapter 2: Twin Higgs theories. Direct & indirect searches of the “twin Higgs”

Introduction about Dark Matter Chapter 3: WIMP Dark Matter. Complementarity of searches (Light) Dark Matter living in a dark sectors Chapter 4: Complementarity of accelerator experiments (high energy vs. high intensity)

S.Gori 2 Overview

Chapter 1: Introduction: The Standard Model and its open problems TODAY SUSY theories. Direct & indirect searches of SUSY particles Chapter 2: Twin Higgs theories. Direct & indirect searches of the “twin Higgs” TOMORROW Introduction on Dark Matter Chapter 3: WIMP Dark Matter; Complementarity of searches (Light) Dark Matter living in a dark sectors Chapter 4: Complementarity of accelerator experiments (high energy vs. high intensity)

S.Gori 2 Overview

Goal: Some basics + overview of what I ﬁnd exciting about BSM theories + pheno Disclaimer: not comprehensive! Please interrupt to ask questions! We do not have to go through all slides! :) S.Gori 2 Let us start!

Chapter 1: Introduction: The Standard Model and its open problems

What we know S.Gori First: what is the Standard Model (SM)?

S.Gori 3 First: what is the Standard Model (SM)?

Particle content:

S.Gori 3 Fundamental principles of the SM

S.Gori 4 Free parameters of the SM Lagrangian

S.Gori 5 Free parameters of the SM Lagrangian

S.Gori 5 Open problems/questions for the SM

Let us re-write the SM Lagrangian allowing also for operators up to dimension 6 in the SM fields

S.Gori 6 Open problems/questions for the SM

Let us re-write the SM Lagrangian allowing also for operators up to dimension 6 in the SM fields

Cosmological constant problem

Hierarchy problem

Vacuum stability problem Flavor puzzle see next slide Origin of Z. Ligeti Strong CP problem lectures neutrino masses

New Physics ﬂavor puzzle

Beyond the Standard Model (BSM) physics? S.Gori 6 Vacuum stability

Once we fix the two free parameters of the Higgs potential, we can compute the running of the quartic coupling, λ, as a function of the energy scale

See lectures by H. Logan

Buttazzo et al, 1307.3536

S.Gori Assuming no New Physics 7 Vacuum stability

Once we fix the two free parameters of the Higgs potential, we can compute the running of the quartic coupling, λ, as a function of the energy scale

See lectures by H. Logan

Buttazzo et al, 1307.3536 We are here. Is this a coincidence?

Stability condition:

S.Gori Assuming no New Physics 7 The hierarchy problem

Let us take a generic theory of scalars, φ, and fermions, ψ:

S.Gori 8 The hierarchy problem

Let us take a generic theory of scalars, φ, and fermions, ψ:

etc.

S.Gori 8 The hierarchy problem

Let us take a generic theory of scalars, φ, and fermions, ψ:

etc.

Scalars are very sensitive to the highest scale of the theory

Generically, we would expect mh ~ 125 GeV some New Physics at the scale MPlanck ~ 1019 GeV

S.Gori 8 Putting it in perspective…

Solar eclipse *not in scale

400 1

The distance 1 : 400 should be precise at the ~ 0.05 level The precision needed to predict the measured to compare Higgs mass: 0.000000000000000000000000000000001

S.Gori 9 Principles to build a “good” BSM theory

Take a local, lorentz invariant, unitary field theory;

Preserve gauge invariance (SU(3) x SU(2)L x U(1)Y), anomaly free; (Typically) do not introduce too large sources of breaking of the accidental / approximate symmetries of the SM classical Lagrangian

Not be ruled out by experiments!

S.Gori 10 Principles to build a “good” BSM theory

Take a local, lorentz invariant, unitary field theory;

Preserve gauge invariance (SU(3) x SU(2)L x U(1)Y), anomaly free; (Typically) do not introduce too large sources of breaking of the accidental / approximate symmetries of the SM classical Lagrangian - baryon and lepton number Bquark = 1/3, Banti-quark = -1/3, Blepton = 0 (Llepton = 1, Lanti-lepton = -1, Lquark = 0) - Individual lepton families Le, Lµ, Lτ (these are broken by neutrino masses in the SM (tiny))

- Custodial symmetry: SU(2)L x SU(2)R → SU(2)V (diagonal) (this is broken by hypercharge and Yukawas in the SM) - SU(3)5 flavor symmetry (this is broken by the Yukawas in the SM) Not be ruled out by experiments!

S.Gori 10 Addressing the hierarchy problem

Most studied Supersymmetry Composite Higgs models or, equivalently, extra-dimensional models Signals More recently: at the LHC Neutral naturalness models (twin Higgs, Chacko et al, 0506256), Relaxation models (Graham et al, 1504.07551), Nnaturalness (Arkani-Hamed et al, 1607.06821), ...

S.Gori 11 Addressing the hierarchy problem

SUSY (basic principle) Twin Higgs (basic principle) Introduce new scalar degrees of Introduce new fermionic degrees freedom that are related to the of freedom that are related to the fermions of the SM fermions of the SM but not charged under the SM gauge symmetries

Cancellation of the quadratic sensitivity is ensured by a Cancel the quadratic sensitivity of the global symmetry (e.g. SU(4) x Z2). Higgs mass to the New Physics scale

S.Gori 11 Introduction: Chapter 1: The Standard Model and its open problems SUSY theories. Direct & indirect searches of SUSY particles Chapter 2: Twin Higgs theories. Direct & indirect searches of the “twin Higgs”

BSM @ the LHC

S.Gori Supersymmetry

Minimal Supersymmetric Standard Model (MSSM)

S.Gori 12 Supersymmetry

Minimal Supersymmetric Standard Model (MSSM)

SUSY is broken (in fact, we know that e.g. the sbottom cannot have the same mass as the bottom quark) Log sensitivity of the Higgs mass to the New Physics scale: TeV-scale SUSY?

S.Gori 12 Supersymmetry

Minimal Supersymmetric Standard Model (MSSM)

SUSY is broken (in fact, we know that e.g. the sbottom cannot have the same mass as the bottom quark) Log sensitivity of the Higgs mass to the New Physics scale: TeV-scale SUSY?

Additional remarkable properties: Gauge coupling unification: if SUSY particles are not too heavy, g3 ~ g2 ~ g1 at MGUT If we impose R-parity (sparticles with R-parity = -1, SM particles with R-parity = +1), the lightest SUSY particle can be WIMP Dark Matter (see class of tomorrow)

S.Gori 12 The SUSY mass scale

The “natural spectrum”:

Higgsinos (tree level)

S.Gori 13 The SUSY mass scale

The “natural spectrum”:

Gluinos (2 loops)

Stops (left handed sbottom) (1 loop)

Higgsinos (tree level)

S.Gori 13 The SUSY mass scale

The “natural spectrum”:

Gluinos (2 loops)

Stops (left handed sbottom) (1 loop)

Higgsinos (tree level)

What is the exact scale? Said in other words: what is the level of “fine tuning” we are comfortable allowing? No guaranteed discovery. Exploration of the SUSY paradigm! (TeV-scale stops imply ~O(1%) fine tuning)

S.Gori 13 (Some) pheno of SUSY particles

SUSY provides a remarkably rich set of signatures for the LHC

S.Gori 14 (Some) pheno of SUSY particles

SUSY provides a remarkably rich set of signatures for the LHC All SUSY particles are charged under the SM gauge symmetries. That means that SUSY particles will be copiously produced at the LHC In the case of R-parity conservation:

squark production (SU(3) interactions) gluino production (SU(3) interactions)

Z, W