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Focus-Point studies at LHC

Focus-Point studies at LHC. U. De Sanctis, T. Lar i, C. Troncon University of Milan and INFN ATLAS Collaboration. SUSY and Dark Matter. DM  SUSY Non-baryonic matter density , computed from WMAP measurements: 0.094 < W DM h 2 < 0.129 (2 s conf idence interval )

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Focus-Point studies at LHC

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  1. Focus-Point studies at LHC U. De Sanctis, T. Lari, C. Troncon University of Milan and INFN ATLAS Collaboration T. Lari Focus Point

  2. SUSY and Dark Matter • DM  SUSY • Non-baryonic matter density, computed from WMAP measurements: 0.094 < WDM h2 < 0.129 (2s confidence interval) • For any specific set of parameters of a SUSY R-parity conserving model, it is possible to compute the LSP relic density from the mass spectrum and the Big-Bang cosmology. • The relic density can be less than WDM (if other contributions to the DM). • The WMAP upper limit is a constrain that defines cosmologically interesting regions of the SUSY parameter hyperspace. • I will limit myself to mSUGRA here. SUSY  DM Once (if) we will have a measurement of SUSY mass spectrum mixing angle etc., one can compute the relic density it corresponds to. T. Lari Focus Point studies

  3. mSUGRA and DM SUSY spectrum computed with ISAJET 7.69 Relic density computed with Micromegas 1.3.0 In most of mSUGRA parameter space the predicted relic density is too large. In the Focus-Point region (large m0) the lightest neutralino has a significant Higgsino component, and the relic density is reduced by s-channel annihilation in the early universe. Focus Point Coannihilation (very narrow) Selected for a detailed study with ATLAS simulation. T. Lari Focus Point studies

  4. Comparison of RGE codes m0 scan m1/2 = 300 GeV tanb = 10 A0=0 m >0 mt=175 GeV Large differences in the predicted relic density using different codes to compute SUSY mass spectrum at the Electro-Weak scale. The study presented here was made using ISAJET 7.69. Wh2 3000 4000 m0 (GeV) T. Lari Focus Point studies

  5. SUSY mass spectrum Mass spectrum at the selected point M0=3400 GeV m1/2 = 300 GeV tanb = 10 A0=0 m >0 mt=175 GeV Masses (GeV) ~ ~ ~ ~ ~ ~ ~ ~ ~ Squarks at the limit of LHC reach. Other sleptons and heavy Higgs too heavy for LHC. Gluino decays into neutralinos and charginos. T. Lari Focus Point studies

  6. Production xSection Sum of jet and missing transverse energy. using ATLAS fast simulation ~ ~ Production xSections ~ ~ 10 fb-1(1st LHC year?) Susy/√SM = 16 ~ ~ • cc production most abundant, • but little jet and missing energy: • difficult to separate from SM. We are • investigating the possibility to use • c±1c02 → c01 l± c01 l+ l- • searching for 3 leptons+missing • energy+no jet events. • gluino pair production dominant • after standard SUSY cuts. • squarks visible with high luminosity Standard cuts (not optimized for this point) on jet and missing energy and lepton veto. T. Lari Focus Point studies

  7. Gluino decays Gluino decays: g → c0qq 7.2 % g → c0bb 3.7 % g → c0tt 28.0 % g → c0 g 5.9 % g → cqq 9.6 % g → ctb 45.6 % Golden channel is the neutralino dilepton decay (gives neutralino mass difference). In principle, the leptons from neutralino decays can be combined with jets to get further mass relations. However, large number of jets from gluino decay (heavy combinatory background) and poor lepton statistics to start with. We have concentrated on reconstruction of the two main gluino decays using tt and tb invariant mass distributions (gives difference between gluino and gaugino mass scales) Neutralino dilepton decays: c03 → c01 l l c02 → c01 l l T. Lari Focus Point studies

  8. Dilepton mass distributions The c02 edge can be measured (constrain on neutralino mixing matrix from the shape?) The c03 edge hardly visible even after three years at design luminosity. At generator level ATLAS ~ ~ c02→ c01l+l- Experimental, flavour subtracted ~ ~ ~ ~ c03→ c01l+l- ATLAS ~ 20 40 60 Mll (GeV) 300 fb-1 No SM background Cuts: Meff > 750 GeV, ETmiss > 100 GeV, 1 jet with pT > 100 GeV Leptons with pT > 10 GeV 20 40 60 80 Mll (GeV) T. Lari Focus Point studies

  9. Gluino decays to chargino Top quark decay into udb or csb fully reconstructed. tb invariant masses reconstructed. 30 fb-1 No SM background ATLAS M(g)-M(c1) • 33 fb-1 • no SM backg. M(g)-M(c2) 200 400 600 Mtb (GeV) T. Lari Focus Point studies

  10. Gluino to neutralino Invariant mass of two fully reconstructed tops. Analysis cuts similar to the gluino to chargino analysis. With high luminosity an endpoint can be extracted. Experimental, flavour subtracted At generator level ATLAS ATLAS ~ ~ g→ c04tt 300 fb-1 No SM background ~ ~ g→ c03tt ~ ~ g→ c02tt ~ ~ g→ c01tt 400 600 800 400 600 800 Mtt (GeV) Mtt (GeV) T. Lari Focus Point studies

  11. Scan of parameter space As one moves up the FP strip the SUSY masses increase and the production cross sections decrease. M0-m1/2 scan for mt=175 GeV,A0=0,tanb=10,m>0 FP5 FP4 Gluino mass FP3 FP2 Cross sections in fb, masses in GeV T. Lari Focus Point studies

  12. Neutralino mass differences The c02is close in mass to c01on the right of the band (where W << WWMAP) while it is close to the c03on the left of the band (where W ~ WWMAP). Almost always m(c02)-m(c01) is below the threshold for c02→ c01 Z0 The dilepton edge would provide a good constrain on W. M(c02)-M(c01) M(c03)-M(c02) T. Lari Focus Point studies

  13. Effect of top mass M1/2 (GeV) M1/2 (GeV) Mt = 175 GeV 500 500 Mt = 172 GeV 100 100 2000 5000 2000 4000 M0 (GeV) As the top mass is increased the FP region moves to larger values of m0. For the same m1/2 the gluino/gaugino masses and decays depend very little on the top mass. Sfermions are within LHC reach only for a light top. Mt = 178 GeV 500 100 2000 5000 M0 (GeV) T. Lari Focus Point studies

  14. Effect of top mass At fixed m1/2 = 300 GeV, relation between mtop and m0 for the FP region. tanb=10,A0=0,m>0 FP8 FP7 FP2 FP6 T. Lari Focus Point studies

  15. Effect of tanb tanb=10 tanb=54 FP2 FP10 FP11 tanb=30 A larger value of tanb pushes the FP band to lower values of m0 At FP11 abundant squark production! FP9 T. Lari Focus Point studies

  16. Conclusions Part of the Focus-Point region is accessible by the LHC experiments. A test point was studied with the ATLAS detector fast simulation. A number of mass constrains can be measured: m(c02)-m(c01), m(g)-m(c±) and m(g)-m(c0). A scan of mSUGRA focuspoint space has been performed with ISAJET to study how the SUSY mass spectrum varies and select points for more detailed studies. • The gluino gets heavier as one moves along the band in the m0-m1/2 plane. The LHC reach to observe gluino pair production should be about m1/2 ~ 900 GeV. Gaugino production may be used to extend this reach, assuming it can be isolated from the SM background. • The neutralino spectrum is sensitive to position both along and trasversal to the band. • The squarks are accessible for low top masses and/or high tanb - this would allow to get m0 (and confirm that sfermions are there…) The Focus-Point is under active study by the ATLAS collaboration. All results are preliminary and more are coming. T. Lari Focus Point studies

  17. Horizontal line scan (III) • Not really any good solution with SOFTSUSY T. Lari Focus Point studies

  18. Comparison of RGE codes (2) Comparison for point M0=3400 GeV m1/2 = 300 GeV tanb = 10 A0=0 m >0 mt=175 GeV All masses in GeV T. Lari Focus Point studies

  19. One more table Little effect from changing the sign of m mh = 114.8 GeV T. Lari Focus Point studies

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