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Deciphering the MSSM at the LHC:. Higgs Bosons, Sparticles. Wedgebox Plots. and. CCAST Workshop on TeV Physics and the LHC. ITP, Nov. 7, 2006. Mike Bisset / 毕楷杰. Co-`workers’: Guan Bian (Tsinghua U.) Nick Kersting, Y. Liu, X. Wang (Sichuan U.)

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Mike Bisset / 毕楷杰


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    1. Deciphering the MSSM at the LHC: Higgs Bosons, Sparticles Wedgebox Plots and CCAST Workshop on TeV Physics and the LHC ITP, Nov. 7, 2006 Mike Bisset / 毕楷杰 Co-`workers’: Guan Bian (Tsinghua U.) Nick Kersting, Y. Liu, X. Wang (Sichuan U.) S. Moretti , F. Moortgat (Europe) References: Eur.Phys.J. C45 (2006) 477-492 hep-ph/0501157 Tsinghua University Beijing, China

    2. Need to avoid constraints from loop contributions to low energy processes and LEP analyses  Recent convergence in Beyond the SMscenarios KK-parity in pair production of new states Minimal Universal Extra Dimensions like R-parity in SUSY T-parity in some Little Higgs Models SUSY clones ITP 2006.11.7 克隆

    3. Spectra of new states expected to be quite different in different models (spins also differ) BUT at LHC only a fraction of the entire spectrum may be identified. (spin may be hard to determine at LHC) One feature of SUSY --- multiple Higgs boson states that may be singly produced in addition to the pair-produced sparticles ITP 2006.11.7 Detecting extra Higgs bosons of SUSY at the LHC is of crucial importance

    4. SUPERSYMMETRY MSSM with R-parity conservation: LSP is stable and invisible ITP 2006.11.7 (-ino for short)

    5. How well can we do at the LHC? ITP 2006.11.7

    6. Detecting the lone Higgs Boson of the Standard Model ITP 2006.11.7

    7. Situation in SUSY MSSM is a bit more complicated: ITP 2006.11.7

    8. the only detect ‘decoupling regime’ ITP 2006.11.7

    9. BUT depends on good detection capabilities for b’s and tau’s signals only detect LEP II excluded ITP 2006.11.7

    10. Depends on good detection capabilities for b’s and tau’s only detect Gold -plated signal LEP II excluded ITP 2006.11.7

    11. try harder we must… 星球大战----尤达 …to feel the FORCE as it flows to us from the LHC data ITP 2006.11.7

    12. Ahh.., but proceeding pictures take into account Higgs boson decays into sparticles they do not! On the dark side… decays to these channels reduce the rates of SM signal channels On the good side… new signals they may be found ITP 2006.11.7

    13. One channel that has received some attention is: 4 leptons + signature (2 OS same-flavor pairs) But if such a signal is observed, is it really from this decay chain? ITP 2006.11.7 (assumption in several studies thus far)

    14. At LHC, can have other stuff but also How much of each? Depends on parameters of the model ITP 2006.11.7 CPS2006

    15. M (GeV) from gaugino unification 2 light sleptons Ino sector inputs for the MSSM ITP 2006.11.7

    16. M (GeV) 2 ITP 2006.11.7

    17. M (GeV) 2 ITP 2006.11.7

    18. ino parameters ino parameters favor favor heavier ino pairs MSSM Point 2 MSSM Point 1 ITP 2006.11.7

    19. Plus crucial role for sleptons MSSM inputs of the slepton sector ITP 2006.11.7 CPS2006

    20. rate enhanced factor of ~5 ITP 2006.11.7

    21. What about in mSUGRA ? region region ITP 2006.11.7

    22. Now what about non-Higgs boson backgrounds? Now what about non-Higgs boson ‘backgrounds’? SM backgrounds can be eliminated mainly through cut coupled with final state hello Other SUSY processes? CPS2006

    23. Identify candidate event:  Exactly four isolated, high , low leptons Apply CUTs: four lepton invariant mass cut  ITP 2006.11.7

    24. Four lepton invariant mass cut Need to know Higgs bosons masses …but this is what we seek to discover! ITP 2006.11.7

    25. MSSM Point 1 MSSM Point 2 ITP 2006.11.7

    26. ino parameters favor ITP 2006.11.7

    27. ino parameters favor heavier ino pairs ITP 2006.11.7

    28. ino parameters favor ITP 2006.11.7

    29. ino parameters favor heavier ino pairs ITP 2006.11.7

    30. Can also look for charged Higgs bosons Set A : signature ITP 2006.11.7

    31. Note that in delineating a discovery region for the Higgs bosons, we are comparing the Higgs signal at one point in the MSSM parameter space to MSSM `backgrounds’ at the same point in the MSSM parameter space Could a Higgs excess postulated for one point really be due to increased backgrounds at another point? Consider different ways in MSSM to produce a pair of inos ITP 2006.11.7

    32. LHC HIGGS 老毕 我 未知 ITP 2006.11.7

    33. 4 leptons + signature (2 OS same-flavor pairs) Now consider all methods of producing –ino pairs other stuff but restrict ourselves to leptons pairs of distinct flavors It turns out that this restriction is not really necessary, but it simplifies the analysis. ITP 2006.11.7

    34. Ino Pair Production Modes: ‘direct’ Higgs-mediated colored-sparticle cascade decays Rates generally smaller Rates may be large if heavier MSSM Higgs bosons are in the right zone Largest potential rates due to strong production cross-sections Especially if gluinos (and squarks) are relatively light. jetty ITP 2006.11.7

    35. Facts of life at the LHC: At a hadron collider, cannot set energy for the parton-level process unlike at a linear collider where one can scan up incrementally in to cross each threshold sequentially one at a time So just must deal with different states being produced simultaneously at different rates Need to disentangle these ITP 2006.11.7

    36. Topologies onDalitz-like plot for our process types decay via off-shell or charged slepton box-like shape for production wedge-like shape also Z-Line: for production ITP 2006.11.7  coin the name `wedgebox plot’

    37. ConsiderWEDGEBOX PLOTS or WEDGE (i != j) BOX (i = j) *On shell sleptons: Z-Line: ITP 2006.11.7

    38. Possible Wedgebox Plots: Could be or or ITP 2006.11.7

    39. Complications  other stuff NO Assumes other stuff NO  just other stuff (no leptons) Typically these decay modes are small to negligibly tiny. Neglects charginos   & slepton pair production Along with leptons from decaying top quarks that might happen to be produced. While not yet included in the framework we’ve developed for possible wedgebox plot topologies, we do understand the distributions obtained from such processes fairly well. ITP 2006.11.7

    40. First consider production processes with the largest rates… Gluino/squark pair production with cascade decays ITP 2006.11.7

    41. charginos!!! Note: these are inclusive 4-lepton rates with no cuts ITP 2006.11.7

    42. From Table can determine relative rates for different –ino pairs  Point C: Now actually simulate signals and backgrounds with HERWIG 6.5 event generator coupled to realistic calorimeter simulation package (recent CMS package) ITP 2006.11.7

    43. Resulting Wedgebox plots envelope-types MSSM Point A ITP 2006.11.7

    44. MSSM Point A Hard edges 3-body decay  off-shell sleptons very important ITP 2006.11.7

    45. MSSM Point A Here sleptons on mass-shell  two-body decays End points no longer -ino mass differences ITP 2006.11.7

    46. MSSM Point A Note change in event density around “stripe” or a other stuff 22.8% of the time ITP 2006.11.7

    47. How many Wedgebox Plots? or or 1 + 3 + 2 + (2)(3) + 6 + (2)(6) = 30 With infininte luminosity, see a 6x6 checkerboard 178 Distinct Wedgebox Plots ITP 2006.11.7

    48. MSSM Point A “maverick events” These events are not expected within out neutralino-only framework for predicting Wedgebox plots Study of the detailed HERWIG output for such generated events confirmed that leptons in these events come from charginos in addition, there were other exceptional features of these points ITP 2006.11.7

    49. MSSM Point B envelope-types ITP 2006.11.7

    50. MSSM Point B Double the luminosity Two heavy –inos very close in mass ITP 2006.11.7