Measurement of the Spin Correlation in the Top Quark Pair Production using the Dilepton Events in 1.96-TeV Proton-Antiproton Collisions
- Univ. of Tsukuba (Japan)
One of the most remarkable properties of the top quark is its extremely short lifetime, which allows us to observe the top quark spin at its production. That means a spin correlation at $$t\bar{t}$$ production is possible to be observed. In this thesis, we report on a measurement of the correlation coefficient between top quark spin and antitop quark spin in the beam basis at top quark pair production. We select $$t\bar{t}$$ pair production candidates by requiring two high transverse momentum leptons, two jets and large missing $$E_T$$ . In order to reconstruct the angular distribution of top quark decay products, we perform full kinematical reconstruction using predicted distributions of $$p^{t\bar{t}}_z$$ , $$p^{t\bar{t}}_T$$ and $$M_{t\bar{t}}$$. We make signal and background templates from admixture of Monte Carlo simulations and data-based background modelings. Then, we perform unbinned likelihood fit of angular distribution of data to signal and background templates and obtain result. This analysis is based on the data of 5.1 $$fb^{-1}$$ collected with the Collider Detector Facility (CDF) at the Fermilab Tevatron between March 2002 and June 2009. We observe 334 $$t\bar{t}$$ candidate events. We determine a confidence interval at 68% level for the correlation coefficient $$\kappa$$ to be -0.520 < $$\kappa$$ < 0.605 or $$\kappa$$ = $$0.042^{+0.563}_{-0.562}$$ on the assumption of $$M_{top}$$ = 172.5 GeV/$c^2$.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1353469
- Report Number(s):
- FERMILAB-THESIS-2011-73; 1517692
- Country of Publication:
- United States
- Language:
- English
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