B physics in Run II Page: 3 of 5
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Tag measured DO
CDF Run I capabilities
same side 1.8 + 0.4 + 0.3 2
soft lepton 0.9 + 0.1 + 0.1 3.1
jet charge 0.8 + 0.1 + 0.1 4.7
opp. side none (no K id)
combined 9.8Table 1: Flavor tagging efficiencies for both CDF and DO detectors based on knowledge from Run I and
MC studies [7].
3.2 B mixing
Oscillations in the B system occurs because of high-order corrections, as shown in Fig. 1. The mass
b w d,s
u,c,t u,c,t
d,s W b
b u,c,t d,s
W W
d,s u,c,t b
Figure 1: Feynman diagrams responsible for mixing in the B systems.
eigenstates, BL and BH, are different from the CP eigenstates B9 and B0:
IBL) = pB9) + qB) BH) = pB0) - qB), q = d, s quarks.
where Amq = mBH - mBL . Many analysis of Bd - Bd oscillations have been performed by several
collaborations and their results have been combined to give [5]: Amd = 0.489 + 0.008 ps-1. For the case
of B2 mesons, due to their large mass difference Am8, the B oscillation frequency is thought to be much
higher than for Bd. Existing data exclude small values of the mixing parameter x8, x8 = AmB O/Lo >
19.0 at the 95% CL [5].
Various decay modes of B2 mesons are under investigation by the DO collaboration. Among them
B - D;-(K-K+-)+, B - D;-(K-K+-)3r+, B - D;-(K-K+-)+v, B - D*X. The
final data sample will be determined by the quality of the track and secondary vertex reconstruction
algorithms. Final states of B's are expected to be fully reconstructed in hadronic mode(s) and they can
be tagged by the charge of the lepton and reconstructed charm meson and/or kaon. The initial state
required for a B8 mixing search can be tagged by applying opposite-side tagging techniques.
We expect to collect of the order of 40,000 events in semi-leptonic channel B2 - D;t+v. But due to
the escaping neutrino, the momentum resolution is reduced, significantly reducing the Am8 reach. The
hadronic mode(s) of the B's, e.g. B2 - Dpi-+ do not have this limitation, but require a lepton from the
other B in order to trigger on these events. In this case the event yield is highly suppressed, leaving us
a few thousand events by the end of the run unless a new trigger can be established. The MC studies
indicate that DO will be able to measure a mixing parameter x8 ~ 30.3
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Kuznetsov, Valentin E. B physics in Run II, article, October 7, 2002; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc742320/m1/3/: accessed April 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.