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Experimental Study of Neutralino Production in SPS 1a: a First Look

Experimental Study of Neutralino Production in SPS 1a: a First Look. Markus Ball Klaus Desch ECFA/DESY Workshop SUSY Session Praha, 15/11/02. Motivation Analysis Mass + Cross section estimation Summary+Outlook. Motivation. Chargino-Neutralino sector of MSSM depends at tree level

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Experimental Study of Neutralino Production in SPS 1a: a First Look

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  1. Experimental Study of Neutralino Productionin SPS 1a: a First Look Markus Ball Klaus Desch ECFA/DESY Workshop SUSY Session Praha, 15/11/02 • Motivation • Analysis • Mass + Cross section estimation • Summary+Outlook M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  2. Motivation • Chargino-Neutralino sector of MSSM depends at tree level • only on 4 parameters: • can be determined in Chargino-Sector • accessible in Neutralino-Sector (cross sections, masses) • particular interest: CP-violation a Phases Choi et al., hep-ph/0002033 Choi et al., hep-ph/0108117 M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  3. Motivation Idea: Choi et al., hep-ph/0108117 But what are the experimental errors doing to this? M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  4. Motivation A guess: a need very accurate measurement of and M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  5. Motivation Complication: at large tanb, the tends to be the NLSP, making the decay dominant! This is experimentally challenging SPS1a M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  6. Motivation Neutralino masses and branching ratios: M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  7. Analysis • in SPS 1a • (far above threshold, WW very forward…) • 500 , no polarisation (yet) • SUSYGEN for signal + SUSY background • PYTHIA for SM background • SIMDET 4.1 for fast detector simulation • so far: only generic have been considered M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  8. Analysis: Signal + Background • Not yet considered: • Higgs • non-tau backgrounds (electrons, muons) M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  9. Analysis: Cut selection • signal topology: • two acoplanar low-multiplicity jets • missing total + transverse energy • jet-jet angle smaller than for WW and charginos/staus • (both tau’s come from one decay) • Cuts: 1. force event into 2 jets (low mult.) 2 E_jet(1) < 100 GeV 3. Abs(E_jet(1)-E_jet(2)) < 50 GeV 4. 5. 6. cos (acoplanarity angle) > 0 7. Visible Energy > 15 GeV 8. M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  10. Analysis: Cut selection M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  11. Analysis: Cut selection M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  12. Analysis: Cut selection M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  13. Analysis: Cut selection M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  14. Analysis: Cut Flow Statisitical precision on cross section (assuming SUSY backgrounds known) : M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  15. Mass reconstruction • is tough… (too much invisible stuff) • in principle: invariant tau-tau-mass has upper endpoint at • this is still true for jet-jet-mass but only few events are • at maximal mass • tried to use 3-prong tau’s to reconstruct tau-direction and • correct jet-jet mass for pt of neutrinos: died statistical death… • try to estimate from distributions: 3 methods a M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  16. Mass reconstruction 1: fit falling slope of invariant mass distribtion M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  17. Mass reconstruction 2. Count events with high masses: N1 N2 M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  18. Mass reconstruction 3. Count events with small opening angles: N1 N2 Method 3 has highest sensitivity: error ~ 1.4 GeV But background not yet considered, expect factor larger error This might be enough to tell, where to do a threshold scan… M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

  19. Summary+Outlook • first look into neutralino production in SPS 1a • tau final states are not easy… • SM and SUSY backgrounds can be sufficienctly reduced to • perform decent cross section times BR measurement • (~2%) • Mass reconstruction only from shape of distributions • o(1-2 GeV) seems possible • many things to be done: • - Higgs background • - reducible backgrounds, esp. di-leptons • - polarisation • - include errors from other SUSY processes (staus,charginos) • - simulate threshold scan M.Ball/K.Desch, Experimental Analysis of Neutralino Production in SPS 1a

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