Supersymmetry

Patrick Mullenders ➔ Why supersymmetry? Index ◆ Particle masses ◆ Cosmological observations ● Dark matter ● Baryon antisymmetry

➔ Why supersymmetry? ◆ What is supersymmetry? ◆ Models ● MSSM ● NMSSM

➔ Detection

2 Why supersymmetry? The standard model is incomplete: Hierarchy problem ➔ 'Natural' mass = Planck mass ➔ Particle mass ≲ (Planck mass)⋅10-16

➔ SUSY: broken symmetry at scale MSUSY ≈ #(TeV)

Image: http://scienceblogs.com/startswithabang/2013/05/15/the-rise-and-fall-of-supersymmetry/ 3 © New Scientist Why supersymmetry? The standard model is incomplete: Cosmology ➔ Dark Matter

◆ Neutrinos are HDM candidates ◆ Need CDM to explain clumping

➔ Prominent CDM candidates

◆ Within the SM framework ● MACHOS ● Primordial BHs

◆ Beyond the SM ● Axions ← strong CP problem ● WIMPS ← Supersymmetric models

Image: https://wccftech.com/dark-matter-continues-evade-worlds-sensitive-scanner-fails-detect-dark 4 -particles/ Why supersymmetry? ➔ WIMPS ◆ SUSY particle !

◆ Early universe: equil. !! qq̅ (or ff)̅ ◆ Cooling: !! → qq̅ ◆ Freeze out: !! ↮ qq̅

➔ Supposing the lightest SUSY particle is stable

(→ R-parity)

◆ Left over !lightest particles could be CDM

5 Why supersymmetry? The standard model is incomplete: Cosmology ➔ Baryonic asymmetry ◆ Baryonic matter ≫ Antibaryonic matter

➔ Supersymmetric theories can account for this by introducing massive bosons, such as ◆ Georgi-Glashow models (X & Y bosons)

+ + X → uLuR , X → e LdR̅ , X → e RdL̅

+ Y → e LuR̅ , Y → dLuR , Y → dL̅ e,R̅

Image: (20100201 ut)r-parity and-cosmological_constraints 6 ➔ Standard Model: Why supersymmetry? ◆ Unified electroweak interaction ◆ Strong interaction ◆ Couplings seem to miss by a factor ~102

➔ Supersymmetric theories: ◆ (Much better) predicted unification of all three SM forces ◆ The SUSY particles cause for changes in the running of the coupling constants w.r.t. energy

Image: http://scienceblogs.com/startswithabang/2013/05/15/the-rise-and-fall-of-supersymmetry/ 7 CERN (European Organization for Nuclear Research), 2001. Why supersymmetry? However…

➔ If SUSY fixes the hierarchy problem → the LHC (energies up to !(TeV)) must be able to discover

SUSY particles. If MSUSY > !(TeV), then SUSY alone is not sufficient. "A light Higgs boson, as has been observed at CERN, is about as likely within the Standard Model as flipping a coin to have it land on its edge. However, by adding SUSY into the mix, it becomes a natural result."

- (Shutterstock / Brian McEntire) ➔ If the lightest SUSY particle is the (largest contributor to) CDM, we should have detected it by now [exp. CDMS & XENOS , SUSY annihilation].

8 Why supersymmetry?

➔ Not all SUSY theories include GG-like X/Y bosons.

"A light Higgs boson, as has been observed at CERN, is about as likely within the Standard Model as flipping a coin to have it land on its edge. However, by adding SUSY into the mix, it becomes a natural result." ➔ There is no physical reason Grand Unification

- (Shutterstock / Brian McEntire) should actually hold.

but if we don't search/theorize, we might never find out.

9 ➔ What is SUSY? Why supersymmetry? ◆ Standard Model extensions

◆ SM particles get SUSY partners ● quarks → squarks ● leptons → sleptons s = ½ → s = 0

● gauge bosons → gauginos s = 1 → s = ½

● Higgs boson → Higgsino s = 0 → s = ½

◆ Note: Supersymmetric extensions of the Higgs sector require an additional complex Higgs scalar doublet in the SM frame, resulting in a total of five Higgs bosons (three with charge 0 (two CP even, one CP odd), one with charge +1, one with

Image: http://www.particleadventure.org/the-role-of-the-higgs-boson.html charge -1) . 10 Supersymmetry ➔ Observed ◆ Baryon number not violated ◆ Lepton '' '' '' ◆ No flavour changing neutral currents ◆ No proton decay (via e.g. ( p → e+!0 ))

➔ Consequence for SUSY models (low energies)

◆ Require conserved R quantum number ● SM particles R = +1 ● SUSY particles R = -1 ◆ e.g. Forbids proton decay: (+1)⋅(+1) ≠ (-1)

➔ Consequence of R-parity conservation

◆ Lightest SUSY particle is stable

Image: LONG-LIVED HEAVY CHARGED PARTICLES AT THE LHC Jonathan Feng UC Irvine 11 LHC Physics Center, Fermilab June 17, 2009. MSSM

Image: http://live.iop-pp01.agh.sleek.net/2014/09/25/sticking-with-susy/ 12 MSSM ➔ What are SUSY particles made of (after EW symmetry breaking)? ◆ Binos ◆ Winos (W̃0,W̃±) ◆ Higgsinos (H̃0,h̃0,Ã0,H̃±)

➔ Forming ◆ 4 Neutralinos ◆ 4 Charginos

The lightest neutralino is prime suspect for CDM.

Note: the heaviest three neutralinos and the charginos can decay weakly into the lightest neutralino.

13 ➔ Problem with MSSM: NMSSM or (M+1)SSM ◆ No explanation why the supersymmetric

mass parameter (dependent on MSUSY) of the Higgs doublets is exactly that to facilitate the measured electroweak scale

➔ NMSSM promotes the parameter to a Yukawa coupling to a singlet field S (complex scalar component of a chiral superfield S)̂ ◆ Allows for symmetry breaking resulting in vacuum expectation values that is of the

desired magnitude of MSUSY.

14 ➔ Expanding around the symmetry broken vacuum NMSSM or (M+1)SSM ◆ The scalar components of Ŝ mix with the neutral components of the Higgs doublets → three CP even, two CP odd neutral scalars ◆ Fermionic superpartners mix as well → five neutralinos

Both the Higgs and neutralino sectors of NMSSM can get considerably modified compared to MSSM.

➔ Heavier Higgs scalar with SM-like coupling to gauge bosons. ➔ Possibly light states with reduced gauge boson couplings. ➔ New Higgs-to-Higgs decay modes, making detection of Higgs bosons at colliders 15 considerably more difficult. NMSSM or (M+1)SSM Upper bound on the lightest Higgs mass in the NMSSM as a function of tanβ = vH1/vH2 for mt = 178

GeV (MA arbitrary: thick full line, MA = 1 TeV: thick

dotted line) and mt = 171.4 GeV (thin full line: MA

arbitrary, thin dotted line: MA = 1 TeV) and in the

MSSM (with MA = 1 TeV) for mt = 178 GeV (thick

dashed line) and mt = 171.4 GeV (thin dashed line).

Squark and gluino masses are 1 TeV and At = Ab = 2.5 TeV.

MA the mass of the CP-odd Higgs scalar

Ai the trilinear soft coupling of the i-(s)quark to the Higgs

MH,SM = 125 GeV

16 Image: https://arxiv.org/pdf/0910.1785.pdf and https://reducedplanckconstant.wordpress.com/tag/higgs-boson/ Detection (neutralino) ➔ Direct detection

➔ Indirect detection ! !

Image: https://kipac.stanford.edu/research/topics/direct-dark-matter-detection 17 and Non-Baryonic Dark Matter in Cosmology - Clinton Miller Current bounds exclude natural SUSY WIMP-only DM models (direct detection)

Mixed axion/WIMP DM models:

spin indep. Z̃1p scattering cross section

WIMP only DM models:

Points above solid lines are currently excluded, dotted line is projected reach of the XENON1T experiment.

Image: https://arxiv.org/pdf/1803.11210.pdf 18 Current bounds exclude natural SUSY WIMP-only DM models (direct detection)

Mixed axion/WIMP DM models:

spin dep. Z̃1p scattering cross section

WIMP only DM models:

Points above solid lines are currently excluded, dotted line is projected reach of the PICO-500 experiment.

Image: https://arxiv.org/pdf/1803.11210.pdf 19 Current bounds exclude natural SUSY WIMP-only DM models (indirect detection)

Thermally averaged WIMP-WIMP annihilation cross section times velocity.

The mixed DM models all lie well below the current bounds, and are thus still viable.

The WIMP-only models are all but a few excluded when compared to current bounds.

Image: https://arxiv.org/pdf/1803.11210.pdf 20 Thank you for your attention

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