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 21.