Lifetime difference in the B$0\atop{s}$ system from untagged B$0\atop{s}$ → J/ΨΦ decay at √s= 1.96 TeV at D0 detector

Abstract

In this dissertation, they present a study of the untagged decay of B$0\atop{s}$ → J/ΨΦ, the final state of which is a superposition of the CP-even and CP-odd states. Within the framework of the standard model (SM), to a good approximation, the two CP eigenstates of the (B$0\atop{s}$, $\bar{B}$$0\atop{s}$) system are equivalent to mass eigenstates. The data collected by the D0 detector between June 2002 to August 2004 (an integrated luminosity of approximately 450 pb-1) has been used for the analysis presented in this thesis. From a simultaneous fit to the B$0\atop{s}$ candidate mass, lifetime, and the angular distribution of the decay products, they obtain the CP-odd fraction in the final state at production time to be 0.16 ±} 0.10(stat) ± 0.02(syst). The average lifetime of the (B$0\atop{s}$, $\bar{B}$$0\atop{s}$) system is measured to be 1.39$+0.13\atop{-0.16}$(stat)$+0.01\atop{-0.02}$(syst) ps, with the relative width difference between the heavy and light mass eigenstates, Δγ/$\bar{γ}$ = (γL/γH)/$\bar{γ}$ = 0.24$+0.16\atop{-0.38}$(stat)$+0.03\atop{-0.04}$(syst). With the additional constraint from the world average of the B$0\atop{s}$ lifetime measurements using semileptonic decays, they find average lifetime of the (B$0\atop{s}$, $\bar{B}$$0\atop{s}$) system 1.39 ± 0.06 ps with Δγ/$\bar{γ}$ = 0.25$+0.14\atop{-0.15}$. They have also done B0 lifetime measurement for its analogous decay mode to J/Ψ}K*. With this measurement they get B0 lifetime 1.530 ± 0.043(stat) ± 0.023(syst) ps. Using above results, they get 0.91 ± 0.09(stat) ± 0.003(syst), for the ratio of the B$0\atop{s}$ and B0 lifetimes ($\bar{γ}$(B$0\atop{s}$)/γ(B0)). These measurements are consistent with the predictions of SM within the measurement uncertainty.