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Studying Very Light Gravitino at ILC

Studying Very Light Gravitino at ILC. Ryo Katayama (Tokyo). Collaborators: Shigeki Matsumoto ( IPMU ) , T . Moroi ( Tokyo ) , K. Fujii (KEK) , T. Suehara (ICEPP), T. Tanabe ( ICEPP ) , S . Yamashita (ICEPP). Motivation.

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Studying Very Light Gravitino at ILC

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  1. Studying Very Light Gravitino at ILC Ryo Katayama (Tokyo) Collaborators: • Shigeki Matsumoto (IPMU) , T. Moroi (Tokyo), K. Fujii (KEK), T. Suehara (ICEPP),T. Tanabe (ICEPP) , S . Yamashita (ICEPP)

  2. Motivation • The very light gravitino (~O(10eV)) is quite attractive from the view of point cosmology. • The next lightest supersymmetryparticle(NLSP) life time directly gives the gravitino mass. • We focus on the case that the NLSP is stau from now. • However, it is difficult to measure the NLSP lifetime at LHC. • It is possible to determine the NLSP lifetime at ILC. [arXiv:1104.3624]

  3. NLSP : Stau τ− e- ~ τ− ~ • From the stau mass and lifetime, we can get the gravitino mass. • To estimate the gravitino mass precision is goal. g ~ g Z＊, γ* ~ τ+ NLSP lifetime example.  t～ 100 x Mpl2 x m3/22/mNLSP5～ O(10–13 ) sec.  ct～ 100 mm e+ τ+ Tau lepton lifetime.  ct ～ 80 mm

  4. Long lifetime means large impact parameter. Thus, by observing the impact parameter distribution of the tau decay products, we can measure the stau lifetime. Impact Parameter Leptonic decay (e±, μ±, ν.) Hadronic decay (π±, K±, etc.) t Stau 1st layer Stau IP Gravitino 16mm Impact parameter d

  5. Background Signal & Background processes ~ ~ (+ ISR) [gg-BG] e+e– e+ e–gg e+ e–t+t– (+ ISR) • First, evaluate the tau pair background. • Tau is reconstructed in the following 1-prong modes: [Signal] e+e–t+t– [PDG]

  6. D0 distribution Display the impact parameter distribution with the mode of e+e-->τ+τ- (black) and e+e-->μ+μ-(red). The difference come from the existence of decay products.

  7. D0 distribution2 Entries of 1-Prong mode Selection 108067 Before Cut Cut Conditions After Cut 1. (θ = Scattering angle of the τ-jet.) 52543 2. (Φ=Azimuthal angle of the τ-jet.) 24372

  8. Conclusion(Schedule) • 1.Genarate the events of stau pair creation as signal. • 2.Include total background into the impact parameter distribution. • 3.Investigate the suitable cuts and its efficiency. • 4.Measure the gravitino mass precision.

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