arXiv subjects
Publications and source records attributed to Hitoshi Yamamoto.
We review recent results on hadronic B meson decays including rare as well as non-suppressed decays. The main emphasis is on those channels relevant to measurement of CP violation in the coming B factories. After briefly describing flavor-tagged charm counting, we cover B -> DK(*), B -> charmless 2-body decays, inclusive eta' production, and final-state-interaction phases in B -> Psi K* and B -> D* rho.
We estimate the sensitivity of single lepton CP violation measurements with respect to that of traditional di-lepton measurements. We find that the sensitivity of the single lepton method is better than that of the di-lepton method. The achievable sensitivity with the currently available data is already in the range relevant to standard model predictions. We also give general expressions for inclusive decay time distributions on $Υ4S$ where the other $B$ is not measured, which will be used to obtain time dependent asymmetries. The expression is of general use whenever one deals with inclusive time-dependent as well as time-integrated measurements in $Υ(4S)\to B^0\bar B^0$ where the final state of the other $B$ is not reconstructed or when only the time difference is measured.
In recent studies of inclusive $B$ decays, it has been suggested that either $B$ mesons decay much more copiously to final states with no open charm than currently assumed, or $B(D^0 \to K^-π^+)$ has to be reduced significantly. This note takes the experimental $B(D^0 \to K^-π^+)$ at its face value and estimates $B(b\to$ no open charm) using complementary methods: one accounts for the $c$ quark in $b\to c$ transitions, the other accounts for the $\bar c$ quark in $b\to c\bar c s$ transitions. Through cancellation of errors, the average gives our best estimate of $B(b\to$ no open charm), and the difference measures the consistency. The results of the methods are consistent with each other, strongly suggesting a much enhanced $B(b\to$ no open charm). This observation indicates that non-perturbative QCD effects are probably causing a sizable fraction of the $b\to c\bar cs$ transitions to be seen as charmless $b\to s$ processes, contrary to smaller traditional expectations. This mechanism has generally been overlooked and may explain the existing experimental data within the framework of the standard model. We then briefly discuss implications on baryon production governed by $b\to c\bar cs$ processes, rare hadronic $B$ decays and CP violation studies.
When a vector meson such as phi, J/Ψ(3S) or Upsilon(4S) decays to a particle-antiparticle pair of neutral mesons, the time distribution of inclusive decay to a given final state is naively expected to be the incoherent sum of those of the two mesons with opposite flavors. In this paper, we show that this is in general not the case for arbitrary coherent two-body states of the mesons, and obtain conditions under which such a naive incoherent sum gives the correct distributions. The analysis is based on the Weisskopf-Wigner formalism, and applicable to the cases where there are more than two orthogonal states that can mix to form a set of eigenstates of mass and decay rate.
In the decay of Upsilon(4S, the decay time distribution of Upsilon(4S) -> f + X, where f is a final state that B^0 or B^0bar can decay to, is the sum of the decay time distributions of B^0 -> f and B^0bar -> f. Using this general rule, we estimate the sensitivity of single lepton CP violation measurements with respect to that of traditional di-lepton measurements. We find that the sensitivity of the single lepton method is comparable to or better than that of the di-lepton method. The two data samples are largely statistically independent, so that they can be combined to improve sensitivity. The advantage of the single lepton measurement increases for large mixings, which suggests that the single lepton method holds promise for B_s. We also discuss lepton asymmetry measurements on the Z^0 peak and in hadron colliders. The achievable sensitivity with the currently available data is already in the range relevant to standard model predictions. PACS numbers: 11.30.Er, 13.20.Gd, 13.20.He, 03.65.Bx
We review the physics of rare, leptonic, and hadronic decays of charmed mesons based on the results submitted to this conference (EPS 95, Brussles).
The b -> c cbar s transition is usually believed to hadronize predominantly in Bbar -> X_c Ds(*)- with the Ds(*)- originating from the virtual W. We demonstrate in a variety of independent ways that other hadronization processes cannot be neglected. The invariant mass of cbar s has sizable phase-space beyond m_D+m_K. The rate for Bbar -> D Dbar Kbar X could be significant and should not be ignored as was done in previous experimental analyses. We estimate the number of charmed hadrons per B-decay, n_c, to be about 1.3 to higher accuracy than obtained in previous investigations. Even though n_c is currently measured to be about 1.1, observing a significant Bbar -> D Dbar Kbar X would support n_c of about 1.3. Many testable consequences result, some of which we discuss.
It is shown that the existing data on two-body B decays, some of them only upper limits, are precise enough to perform an isospin analysis to extract the phase shifts due to final state interaction. Unlike charm decays, no significant final state interaction is observed in decays $B\to Dπ, Dρ$, and $D^*π$ supporting the factorization hypothesis in these decays. By fitting directly the isospin amplitudes obtained, we extract the ratio $a_2/a_1$, where $a_1$ and $a_2$ are the coefficients in the factorized effective Hamiltonian.
Hadronic decays of $B$ mesons are reviewed. First, masses of $B$ mesons and observed patterns together with physics behind them are discussed. Then the effective Hamiltonian responsible for major decays is presented and its practical applications are discussed in the context of factorization. Various tests of factorization are then studied. For rare decays, the focus is placed on $Kπ$, $ππ$ final state and the penguin-mediated $X_sγ$. In general, the measurements are in excellent agreement with predictions of the standard model.