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SUSY activities at IPM

SUSY activities at IPM. Saeid Paktinat School of Particles and Accelerators, IPM, Tehran, Iran. People and topics IPM SUSY analyses include both leptonic and hadronic signatures: Ali (CERN): Opposite Sign leptons Hamed (CERN): Same Sign electrons

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SUSY activities at IPM

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  1. SUSY activities at IPM Saeid Paktinat School of Particles and Accelerators, IPM, Tehran, Iran

  2. People and topics • IPM SUSY analyses include both leptonic and hadronic signatures: • Ali (CERN): Opposite Sign leptons • Hamed (CERN): Same Sign electrons • Batool (IPM): inclusive hadronic (top final states) • Saeid(IPM): inclusive hadronic (top final states) • A few new students are in the queue to join the group.

  3. Ali Fahim

  4. SUSY in SameSign Di-Electron chanel HamedBakhshian Backgrounds from standard model to this channel of SUSY is almost negligible. Di electronic decays of ttbar or WW events, when the charge of one of the electrons is badly measured, are almost 25% of all of the backgrounds We can estimate the number of this kind of background: • Where Pmm is probability of charge mismeasurement. To find it, we can select Di-Electron events under the Z peak and count the same sign events. • Simulation shows that 1.2% of electrons are wrongly measured. • By discarding the electrons: • With High Impact parameter • With a converted emitted photon in the way • That the different algorithms of tracking (CTF and GSF) don't calculate the same charge • we can reduce the probability of charge misidentification to 0.2% by killing only 6% of good electrons.

  5. A method to measure the probability of charge mismeasurement as a function of electron properties has been developed and a good agreement with MC information is seen. Then we can estimate the number of this kind of background in different integrated luminosities by this method. The other 75% of the backgrounds is from fake electrons and are still under investigation. The method can be applied in data, as soon as enough Z events have been accumulated. (50pb-1 is needed)

  6. BatoolSafarzadeh

  7. SUSY in top final states • BatoolSafarzadehSaeid Paktinat • 10 TeV • c.m.s energy Control Sample by Reversing the MHT Cut The reconstructed top mass distribution does not depend on MHT, therefore this variable is used to estimate the background. The MHT >150 GeV region is referred to as signal region and Events with MHT < 150 GeV are selected as a control sample. For both samples the other selection criteria are identical. MTop > 750 GeV is used for normalization

  8. The reconstructed top mass distribution of the background processes in logarithmic scale (left) and linear scale (right). Numbers of the simulated and predicted background processes. On M Top < 400 GeV region the SUSY excess is visible with a high significance (Sig ≥5σ)

  9. SUSY in top final states 7 TeV, 100 pb-1 • Saeid Paktinat To estimate the QCD background, the template method is used. The idea is to have the MHT shape from a region that SUSY and the other SM contribution is sufficiently low. The low MHT region is used for the normalization. The events with M_Top > 350 GeV and M_W > 250 GeV are used. To forther suppress the ttbar contribution, events with b-jet are rejected. To suppress the SUSY contamination, DeltaPhi (MHT , MPT) > 2.0.

  10. Real and template MHT composition Very pure control sample.

  11. Method performance: Simulated :: 3 +/- 1.22 Predicted :: 8.47 +/- 2.06 (SM Only) Predicted :: 8.49 +/- 2.06 (SM + SUSY)

  12. Thank you for your attention

  13. Backup • Cut Flow • Pre-selection Criteria: • Lepton Veto (e & μ: |η| <2.4 , PT >10 GeV). • Jets(IC5): ET > 50 GeV , |η| < 2.5, 0.05 < EMF < 0.95. • (Planning to use Anti-KT algorithm ) • ∆Φ(Ji,MHT)>0.3 rad(i=1,2,3). • PTj1 > 180 , PTj2 >150 . • At least one b-jet + two non b-jets. (Discriminator:TKCountingHighEffBJettags >8.5 tagged as a b jet ) • Selection Criteria: • MHT > 150GeV. • ∆Φ(PTtrack, MHT) < 2.0. • |MW-80|<15 GeV(The invariant mass of two non b tagged jets must be in W mass window.) • |η| -top < 2.0 ∆Φ(Top,MHT) <2.8

  14. Control Sample The normalization factor is obtained from the event numbers of the signal region and the control sample in the top mass distribution (Mtop > 500 GeV), in this region the SUSY signal contribution is expected to be relatively small. The reconstructed top mass distribution for the background processes. The dash line shows the estimated distribution from the reversed MHT method. Numbers of background events and estimated numbers for all background processes without SUSY signal.

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