SUSY models under siege: LHC constraints and electroweak fine-tuning

Apr 8, 2014
31 pages
Published in:
  • Phys.Rev.D 89 (2014) 11, 115019
  • Published: Jun 23, 2014
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Abstract: (APS)

Recent null results from LHC8 supersymmetry (SUSY) searches along with the discovery of a standard model (SM)–like Higgs boson with mass mh125.5  GeV indicates sparticle masses in the TeV range, causing tension with conventional measures of electroweak fine-tuning. We propose a simple fine-tuning rule which should be followed under any credible evaluation of fine-tuning. We believe that overestimates of electroweak fine-tuning by conventional measures all arise from violations of this rule. We show that to gain accord with the fine-tuning rule, then both the Higgs mass and the traditional ΔBG fine-tuning measures reduce to the model-independent electroweak fine-tuning measure ΔEW. This occurs by combining dependent contributions to mZ or mh into independent units. Then, using ΔEW, we evaluate EW fine-tuning for a variety of SUSY models including mSUGRA, NUHM1, NUHM2, mGMSB, mAMSB, hyper-charged AMSB, gaugino AMSB and nine cases of mixed moduli-anomaly (mirage) mediated SUSY breaking models while respecting LHC Higgs mass and B-decay constraints (we do not impose LHC8 sparticle mass constraints due to the possibility of compressed spectra within many of these models). We find mSUGRA, mGMSB and the AMSB models all to be highly fine-tuned. The NUHM1 model is moderately fine-tuned while NUHM2 which allows for radiatively driven naturalness (RNS) allows for fine-tuning at a meager 10% level in the case where m(Higgsinos)100200GeV and the TeV-scale top squarks are well mixed. Models with RNS may or may not be detectable at LHC14. A s500  GeV e+e- collider will be required to make a definitive search for the requisite light Higgsinos.

Note:
  • 30 pages and 12 figures; revised version includes additional references and several typo fixes
  • 12.60.Jv
  • 14.80.Ly
  • new physics
  • naturalness
  • supergravity: minimal
  • supersymmetry: symmetry breaking
  • symmetry breaking: anomaly
  • mediation: mirage
  • Higgsino: mass
  • Higgs particle: mass