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The Studying very light gravitino using ILD detector simulation

The Studying very light gravitino using ILD detector simulation. Ryo Katayama (Tokyo). Collaborators: T.Suehara( ICEPP ) , T.Tanabe( ICEPP ), Y.Satoru( ICEPP ) , M. Sigeki ( IPMU) , M. Takeo ( IPMU ) , F.K eisuke ( KEK ). Introduction.

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The Studying very light gravitino using ILD detector simulation

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  1. The Studying very light gravitino using ILD detector simulation Ryo Katayama (Tokyo) Collaborators: • T.Suehara(ICEPP) , T.Tanabe(ICEPP), • Y.Satoru(ICEPP) , M.Sigeki(IPMU) , • M.Takeo(IPMU) ,F.Keisuke(KEK)

  2. Introduction • In the case of Gauge mediated SUSY breaking (GMSB), the gravitino appears as the lightest supersymmetricparticle(LSP) • The O(1 eV) very lightgravitinois very attractive from view of Cosmology

  3. NLSP stau By measuring the NLSPmass and lifetime, gravitino mass be determined τ− e- ~ τ− ~ ~ Z＊, γ* ~ τ+ e+ For example, the following value give a stau life time of mLSP=6.5eV , mNLSP=120GeV  ct =100 mm τ+ For comparison ,the tau lifetime is  ct =87.11 mm [arXiv:1104.3624]

  4. The measurement of stau lifetime Leptonic decay (e±, μ±, ν.) Hadronic decay (π±, K±, etc.) Decay products • The impact parameterisdefined as the shortest length between track and IP. • By using the impact parameter distribution ,we can measure the staulifetime. • The staudecay to cascade products.The impact parameter enhance. • We do not use the impact parameter in the z direction because of the large uncertainty of the primary vertex in that direction.We use the d0 component (projection onto the x-y plane). t stau Gravitino IP 16mm Impact parameter d 1st layer τ− e- ~ τ− ~ ~ Z＊, γ* ~ τ+ e+ τ+

  5. Signal and Background Signal & Background processes

  6. Condition • stau mass :120GeV • decay life time :cτ = 100μm • Center of mass energy : 500GeV,Integrated luminosity : 500fb-1,Beam polarization : (Pe-,Pe+)=(+0.8,-0.3) • τ decay mode :1-prong ~ 85％ • Selection: 1-prong+1-prong event <The decay ratio 1-prong mode > [PDG]

  7. Cut

  8. stau mass accuracy (preliminary) • From fitting track energy upper limit, the stau mass can be determined from kinematic relation. • By running Poissonstatics fluctuationto high statistics track energy distribution samples,we make a experiment (Toy MC). • By running Toy MC 10,000 times,the mass fit distribution can be acquired. • From the error estimation from the mass fit distribution, we acquired following result.

  9. stau lifetime accuracy1(preliminary) • The do distribution reflect the lifetime stau->tau. • High statistics samplewasprepared for ct = 90 mm , 100 mm, 110 mm (Template samples). • By using for ct = 100 mm, the do distributionwascreated from Toy MC. 注)右上二段目のBackground分布はct ~ 100mmのデータを使用

  10. stau lifetime accuracy2(preliminary) • At first, we compute the reduced chi2between Toy MC sample and template sample. • The chi2 minimum indicates the most probable value of the lifetime given by the fit. • By Evaluating the error from Toy MC 10,000 times,we obtainedfollowing result.

  11. Gravitino mass accuracy (preliminary) • The NLSP lifetime and mass substitute to the following gravitino mass accuracy formula • The relative accuracy of gravitino mass canwasdetermined about 3%.

  12. open issues • The Cross Section of Bhabha scattering and gg->ll have order ~ nb ,event number~O(109). • Since MC statistics is insufficient , preselected samples should be prepared. • If Bhabha is found to be problematic, we may choose to drop theelectron channel. • Estimate the accuracy of the stau mass by using the threshold scan • Changing stau mass and lifetime, evaluate the accuracy of gravitino mass.

  13. Summary • In the case that stau mass is 120GeV and lifetime is ct = 100mm , using ILD detector simulation , • we acquired the following result: • From track energy fit , the accuracy of stau mass is 1.1% • From template fit , the accuracy of stau lifetime is 1.4% • Combidingabove results , the accuracy of gravitino mass isestimeted to be about 3%.

  14. Back Up

  15. Constraint from cosmology

  16. Acoplanarity(with all other cuts applied)

  17. Visible Energy(with all other cuts applied)

  18. Transverse momentum(with all other cuts applied)

  19. |cosqmis|(with all other cuts applied)

  20. |cosq|(with all other cuts applied)

  21. q12/Evis(with all other cuts applied)

  22. Transverse momentun(after only 2-prong) 注)ただしシグナルは無偏極である

  23. Visible energy ( after only 2-prong ) 注)ただしシグナルは無偏極である

  24. |cosq| (after only 2-prong) 注)ただしシグナルは無偏極である

  25. Acoplanarity (After only 2-prong) 注)ただしシグナルは無偏極である

  26. d0/d0error • track energy(GeV) • Yellow:SignalRed:Tau pair Blue:AA->tautauGreen:WW+ZZ

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