1. Search for extra-boson from Top Decays Jenna Lane, Paul Miyagawa and Un-Ki Yang Manchester Christmas Meeting, Dec. 20-21

2. 2 Motivation  Search for extra boson from top decays (top->Xb, where X->jj) using a dijet mass  Charged Higgs is a good candidate at low tan(  )  Provide a Jet Energy Scale information using a standard W mass W+W+ W - (H-) t t b-jet jet M jj

3. 3 Method  Use a kinematic top mass fitter developed at CDF Default fitter: M_W(jj)=M_W(l )=80.4, M(top)=M(anti-top) Modified fitter: W(l )=80.4, M(top)=M(anti-top)=175 GeV  Lepton+jet channel with double b-tagged events W (80) H+(120) top->H + b, H + ->csbar using CDF MC

4. 4 Improvements in dijet mass?  Poor resolution for Njet>4  Better handling on the 5th jet Detailed studies of extra jets  Δ R (5th-jet, L4jet)<1, merge it  Good improvement For 2 Hjets

5. 5 Status and Plan  A dijet mass resolution has been improved.  A binned likelihood fitter works.  Plan to make ATLAS MC samples and finish sensitivity studies  Jenna Lane (student) and Paul Miyagawa (postdoc) will join this effort. toy exp.:H:W:B=1:1:1

6. 6 Other Activities  Systematic studies on the extra- jets (ISR/FSR)  Dominant systematic for precision measurements at LHC  Extend CDF ISR/FSR studies to LHC region with other ATLAS colleagues  High Level Trigger: plan to spend 50% efforts on this projec.  qqbar->bbbar @LHC By M. Cobal

7. 7 Backup  Current Limit on the charged Higgs BR(t  H ± b)<0.4 @95%CL Assuming BR(H ±  