1. Degeneracies in the MSSM with Standard Model Background Tom Hartman, Harvard University work in progress with J. Thaler and L.-T. Wang University of Michigan, April 2006

2. Summary Do degeneracies exist? Can we break them? Three examples: –Wino-bino flipper –Ino cycler –“Squeezer” Degeneracies at high luminosity

3. Degeneracies in the MSSM Very different models might have the same set of signatures at the LHC (within error bars)

4. Degeneracies in the MSSM hep-ph/0512190 Arkani-Hamed, Kane, Thaler, Wang Simulated 39,137 MSSMs Compared 1808 LHC observables Found 364 degenerate pairs ~ 12 ie, on average, 12 distinct MSSMs produce the same set of signatures (where “distinct” means inos differ by at least 10%) Discrete degeneracies, not just big error bars But: –No standard model background –Luminosity of 10 fb -1 instead of 300 fb -1.

5. The logical next step Find better degeneracies –This is a difficult problem. Add Standard Model Background Break the degeneracies whenever possible –Better signatures –Higher luminosity See what’s left. Are there persistent degeneracies?

6. Standard Model Background ChannelMin p T (GeV)  (fb) Events generated QCDp T > 1001.3 10 9 5M WW7.0 10 4 1M WZ2.6 10 4 1M ZZ1.1 10 4 1M Wjp T > 204.2 10 7 10M Zjp T > 201.5 10 7 2M tt5.0 10 5 4M bbp T > 509.3 10 7 2M W,Z + >2 jets??? none Generated with Pythia.

7. Example I: Wino-Bino Flipper Similar ∆M’s in decay chains, so similar jet Pt distributions such as Meff.

8. Wino-Bino Flipper: Similarities Model AModel B Meff hardest jet pt electron pt

9. Wino-Bino Flipper: Differences Lepton fractions (10 fb -1 )e-e+ µ-µ- µ+µ+ wino < bino15.5%16.316.216.6 bino < wino14.217.615.117.9 Higgs Counting (bb) Z Counting (l+l-) Charge asymmetry

10. Charge Asymmetry The LHC is a pp collider, so the final-state particles are charge asymmetric. If the decay looks like squark ---> jet + chargino --> jet +W + LSP then the charge asymmetry is in W’s so we can see it. If the decay looks like squark --> jet + neutralino --> jet + W + chargino then the charge asymmetry is lost inside the first jet.

11. Wino-Bino Flipper: 10 fb -1 1l +/- Asym. Zh per 1000 Model A50.4 ± 1.41.3 ± 0.28.9 ± 0.9 Model B55.4 ± 1.42.0 ± 0.29.5 ± 0.9 Signif. 2.5  useless Total cross section is not known precisely, so only ratios are used in the analysis ( # Z’s / # events passing trigger, # h’s / # events passing trigger, etc.) Including background, this pair is indistinguishable at 10 fb -1

12. Breaking the flipper degeneracy Luminosity (fb -1 ) discovery (5  ) Z monolepton dilepton higgs

13. Example II: ino Cycler

14. Breaking the cycler degeneracy Luminosity (fb -1 ) discovery (5  ) Z monolepton higgs dilepton Although charge asymmetry is stronger in this pair (57% vs 50% positive), total lepton count is lower so the signal is swamped by background. Can we trust Z counting to break degeneracies?

15. Example III: “Squeezer” Soft leptons from near-degenerate bino  wino decay are undetectable.

16. Squeezer: Similarities For this particular pair, there are several significant differences (Counting leptons, higgses, and Z’s). However, these are caused by differences in the squark splittings so might be absent in a better degenerate pair. Meff Electron pt

17. Summary Now including standard model background Lepton asymmetry is a good way to break ino-identity degeneracies, with a good clean physics explanation. Finding degeneracies is difficult, even when you start with a close pair. Looks like narrower signatures + higher luminosity + background will reduce number of degeneracies overall (compared to initial result ~ 12) Coming soon…. A better understanding of at high luminosity Study is limited to the MSSM, but degeneracies are more general. Hopefully the MSSM is giving us ideas about how to think about them and how to deal with them when they arise elsewhere.