Discrete Ambiguities in the Measurement of the Weak Phase Gamma

Several time-independent methods have been devised for measuring the phase gamma of the Cabibbo-Kobayashi-Maskawa unitarity triangle. It is shown that such measurements generally suffer from discrete ambiguity which is at least 8-fold, not 4-fold as commonly stated. This has serious experimental implications, which are explored in methods involving B->DK decays. The measurement sensitivity and new physics discovery potential are estimated using a full Monte Carlo detector simulation with realistic background estimates.Comment: 15 pages, 2 figures, fixed typ

Top-quark spin correlation at Linear Colliders with anomalous couplings

We investigate the feasibility of probing anomalous top-quark couplings of $Wtb$, $Z t \bar{t}$, and $\gamma t \bar{t}$ in terms of an effective Lagrangian with dimension-six operators at future $e^+e^-$ linear colliders with a c. m. energy $\sqrt s \sim 500-800$ GeV. We first examine the constraints on these anomalous couplings from the $Z\to b \bar{b}$ data at LEP I and from unitarity considerations. We then consider in detail the effects of anomalous couplings on $t \bar{t}$ spin correlations in the top-pair production and decay with three spin bases: the helicity, beamline and off-diagonal bases. Our results show that the polarized beams are more suitable for exploring the effects of different new operators. For polarized beams, the helicity basis yields the best sensitivity.Comment: 23 pages, 10 figures, references adde

Measuring γ\gamma in B±→K±(KK∗)DB^\pm \to K^\pm (K K^*)_D decays

We develop a method to measure the CKM angle $\gamma$ without hadronic uncertainties from the analysis of $B^\pm \to K^\pm D^0$ and K^\pm \D0bar followed by singly Cabibbo-suppressed $D$ decays to non CP-eigenstates, such as $K^\pm K^{*\mp}$. This method utilizes the interference between $b\to c\bar u s$ and $b\to u\bar c s$ decays, and we point out several attractive features of it. All the modes that need to be measured for this method are accessible in the present data.Comment: 8 page

Using untagged B^0 -> D K_S to determine gamma

It is shown that the weak phase gamma=arg(-V_{ud}V^*_{ub}V_{cb}V_{cd}^*) can be determined using only untagged decays B/Bbar--> D K_S. In order to reduce the uncertainty in gamma, we suggest combining information from B^{+-}--> DK^{+-} and from untagged B^0 decays, where the D meson is observed in common decay modes. Theoretical assumptions, which may further reduce the statistical error, are also discussed.Comment: 18 pages, same as published versio

Photon polarization in radiative B decays

We study decay distributions in B -> K pi pi gamma, combining contributions from several overlapping resonances in a K pi pi mass range near 1400 MeV, (1^+) K_1(1400), (2^+) K^*_2(1430) and (1^-) K^*(1410). A method is proposed for using these distributions to determine a photon polarization parameter in the effective radiative weak Hamiltonian. This parameter is measured through an up-down asymmetry of the photon direction relative to the K pi pi decay plane. We calculate a dominant up-down asymmetry of 0.33 +- 0.05 from the K1(1400) resonance, which can be measured with about 10^8 B B-bar pairs, thus providing a new test for the Standard Model and a probe for some of its extensions.Comment: 22 pages, 3 figures, version to appear in Phys. Rev.

Determining γ\gamma using B±→DK±B^\pm \to D K^\pm with multibody D decays

We propose a method for determining $\gamma$ using $B^\pm\to D K^\pm$ decays followed by a multibody $D$ decay, such as $D \to K_S \pi^-\pi^+$, $D \to K_S K^-K^+$ and $D \to K_S \pi^-\pi^+\pi^0$. The main advantages of the method is that it uses only Cabibbo allowed $D$ decays, and that large strong phases are expected due to the presence of resonances. Since no knowledge about the resonance structure is needed, $\gamma$ can be extracted without any hadronic uncertainty.Comment: 17 pages, 1 figur

CP Violation in τ→3πντ\tau\rightarrow 3\pi\nu_\tau

We consider CP violating effects in the decays $\tau\rightarrow (3\pi)\nu_\tau$ where both the ${\rm J}^{\rm P}=1^+$ resonance, $a_1$, and ${\rm J}^{\rm P}=0^-$ resonance, $\pi^\prime$, can contribute. The interference between the $a_1$ and $\pi^\prime$ resonances can lead to enhanced CP-violating asymmetries whose magnitudes depend crucially on the $\pi^\prime$ decay constant, $f_{\pi^\prime}$. We make an estimate of $f_{\pi^\prime}$ with a simplified chiral Lagrangian coupled to a massive pseudoscalar field, and we compare the estimates from the non-relativistic quark model and from the QCD sum rule with the estimate from the `mock' meson model. We then estimate quantitatively the size of CP-violating effects in a multi-Higgs-doublet model and scalar-leptoquark models. We find that, while CP-violating effects in the scalar-leptoquark models may require more than $10^{10}$ $\tau$ leptons, CP-violating effects from the multi-Higgs-doublet model can be seen at the $2\sigma$ level with about $10^7$ $\tau$ leptons using the chiral Lagrangian estimate of $f_{\pi^\prime}=(1\sim 5)\times 10^{-3}$ GeV.Comment: Latex, 30 pages, 2 figures (not included). Three compressed postscript files of the paper available at ftp://ftp.kek.jp/kek/preprints/TH/TH-419/kekth419.ps.gz, Tau1.ps.gz, Tau2.ps.g

Measuring the Weak Phase gamma in Color Allowed B->DKpi Decays

We present a method to measure the weak phase gamma in the three-body decay of charged B mesons to the final states D K pi0. These decays are mediated by interfering amplitudes which are color-allowed and hence relatively large. As a result, large CP violation effects that could be observed with high statistical significance are possible. In addition, the three-body decay helps resolve discrete ambiguities that are usually present in measurements of the weak phase. The experimental implications of conducting these measurements with three-body decays are discussed, and the sensitivity of the method is evaluated using a simulation.Comment: 18 pages, LaTex, 15 eps and ps figure

CP Violation in Fermion Pair Decays of Neutral Boson Particles

We study CP violation in fermion pair decays of neutral boson particles with spin 0 or 1. We study a new asymmetry to measure CP violation in $\eta, K_L \rightarrow \mu^+\mu^-$ decays and discuss the possibility of measuring it experimentally. For the spin-1 particles case, we study CP violation in the decays of $J/\psi$ to $SU(3)$ octet baryon pairs. We show that these decays can be used to put stringent constraints on the electric dipole moments of $\Lambda$, $\Sigma$ and $\Xi$.Comment: 14p, OZ-93/22, UM-93/89, OITS 51

Kaluza-Klein gravitino production with a single photon at e^+ e^- colliders

In a supersymmetric large extra dimension scenario, the production of Kaluza-Klein gravitinos accompanied by a photino at e^+ e^- colliders is studied. We assume that a bulk supersymmetry is softly broken on our brane such that the low-energy theory resembles the MSSM. Low energy supersymmetry breaking is further assumed as in GMSB, leading to sub-eV mass shift in each KK mode of the gravitino from the corresponding graviton KK mode. Since the photino decays within a detector due to its sufficiently large inclusive decay rate into a photon and a gravitino, the process e^+ e^- -> photino + gravitino yields single photon events with missing energy. Even if the total cross section can be substantial at sqrt(s)=500 GeV, the KK graviton background of e^+ e^- -> photon + graviton is kinematically advantageous and thus much larger. It is shown that the observable, sigma(e^-_L)-sigma(e^-_R), can completely eliminate the KK graviton background but retain most of the KK gravitino signal, which provides a unique and robust method to probe the supersymmetric bulk.Comment: Reference added and typos correcte