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A. I. Sanda

Publications and source records attributed to A. I. Sanda.

At least 37 records · Page 2Linked to original sources
arXiv2002

Possible Large Direct CP Violations in Charmless B-Decays

We discuss the perturbative QCD approach for the exclusive two body B-meson decays to light mesons. We briefly review its ingredients and some important theoretical issues on factorization approach. We show numerical results which are compatible with present experimantal data for the charmless B-meson decays. Specailly we predict the possibility of large direct CP violation effects in $B^0 \to π^{+}π^{-}$ $(23\pm7 %)$ and $B^0\to K^{+}π^{-}$ $(-17\pm5%)$. In the last section we investigate two methods to determine the weak phases $ϕ_2$ and $ϕ_3$ from $B \to ππ,Kπ$ processes. We obtain bounds on $ϕ_2$ and $ϕ_3$ from present experimental measurements.

hep-ph↗
arXiv2002

A Novel PQCD Approach in Charmless B-meson Decays

We discuss a novel pertubative QCD approach on the exclusive non-leptonic two body B-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approaches. We show numerical results which is compatible with recent experimantal data for the charmless B-meson decays.

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arXiv2001

How well can we predict CP asymmetry in $B\to ππ$, $Kπ$ decays?

Using the perturbative QCD amplitudes for $B\to ππ$ and $B\to Kπ$, we have performed an extensive study of the parameter space where the theoretical predictions for the branching ratios are consistent with recent experimental data. From this allowed range of parameter space, we predict the mixing induced CP asymmetry for $B \to π^+π^-$ with about 11% uncertainty and the other CP asymmetries for $B\to ππ$, $Kπ$ with 40% ~ 47% uncertainty. These errors are expected to be reduced as we restrict the parameter space by studying other decay modes and by further improvements in the experimental data.

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arXiv2001

B -> K eta(') decay in perturbative QCD

We compute B->K eta' branching ratio using perturbative QCD approach. We show that a triangular relation among amplitudes for B^0->K^0 pi^0, B^0->K^0 eta, B^0->K^0 eta' receives large corrections from SU(3) breaking effects. If experimental value will come closer to the lower limit of the present BELLE data there will be a possibility to understand the large branching ratio of B^0->K^0 eta'. Otherwise, we perhaps need to modify our understanding of eta' meson, for example, inclusion of a possible admixture of gluonium state.

hep-ph↗
arXiv2001

On a clean determination of $ϕ_2$

We point out that time dependent study of four decay modes $B^0(t)\to \Dbar K_S$, $B^0(t)\to D K_S$ $\Bbar^0(t)\to \Dbar K_S$, and $\Bbar^0(t)\to D K_S$ allows us to measure $\sin(ϕ_1-ϕ_2)$ - contrary to previously obtained result that it measures $\sin(2ϕ_1+ϕ_3)$. The time dependent study of $B_s^0(t)\to D^\pm_sK^\mp$, and the study of $B^-\to K^-(D,\Dbar)\to K^-f$ decay where $D\to f$ is a doubly Cabibbo suppressed decay yield information on $ϕ_3$, as previusly expected.

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arXiv2001

Leading-power contributions to $B\toπ,ρ$ transition form factors

We calculate the $B\toπ,ρ$ transition form factors in the framework of perturbative QCD to leading power of $1/M_B$, $M_B$ being the $B$ meson mass. We explain the basic principle by discussing the pion electromagnetic form factor. It is shown that the logarithmic and linear singularities occurring at small momentum fractions of light meson distribution amplitudes do not exist in a self-consistent perturbative analysis, which includes $k_\perp$ and threshold resummations.

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arXiv2001

Fat penguins and imaginary penguins in perturbative QCD

We evaluate $B\to Kπ$ decay amplitudes in perturbative QCD picture. It is found that penguin contributions are dynamically enhanced by nearly 50% compared to those assumed in the factorization approximation. It is also shown that annihilation diagrams are not negligible, and give large strong phases. Our results for branching ratios of $B\to Kπ$ decays for a representative parameter set are consistent with data. We evaluate $B\to Kπ$ decay amplitudes in perturbative QCD picture. It is found that penguin contributions are dynamically enhanced by nearly 50% compared to those assumed in the factorization approximation. It is also shown that annihilation diagrams are not negligible, and give large strong phases. Our results for branching ratios of $B\to Kπ$ decays for a representative parameter set are consistent with data.

hep-ph↗
arXiv2000

Penguin Enhancement and $B\to Kπ$ decays in perturbative QCD

We compute branching ratios of $B\to Kπ$ decays in the framework of perturbative QCD factorization theorem. Decay amplitudes are classified into the topologies of tree, penguin and annihilation, all of which contain both factorizable and nonfactorizable contributions. These contributions are expressed as the convolutions of hard $b$ quark decay amplitudes with universal meson wave functions. It is shown that (1) matrix elements of penguin operators are dynamically enhanced compared to those employed in the factorization assumption; (2) annihilation diagrams are not negligible, contrary to common belief; (3) annihilation diagrams contribute large strong phases; (4) the uncertainty of current data of the ratio $R={\cal B}(B_d^0\to K^\pmπ^\mp)/{\cal B}(B^\pm\to K^0π^\pm)$ and of CP asymmetries is too large to give a constraint of $ϕ_3$. Assuming $ϕ_3=90^o$ which is extracted from the best fit to the data of $R$, predictions for the branching ratios of the four $B\to Kπ$ modes are consistent with data.

hep-ph↗
arXiv1999

On the Other Five KM Triangles

A comprehensive program of \cp~studies in heavy flavour decays has to go beyond observing large \cp asymmetries in nonleptonic B decays and finding that the sum of the three angles of the KM triangle is consistent with 180$^{\circ}$. There are many more correlations between observables encoded in the KM matrix; those can be expressed through five KM triangles in addition to the one usually considered. To test the completeness of the KM description one has to obtain a highly overconstrained data set sensitive to ${\cal O}(λ^2)$ effects with $λ= \sin θ_C$. Those fall into two categories: (i) Certain large angles agree to leading order only, yet differ in order $λ^2$ in a characteristic way. (ii) Two observables angles are - for reasons specific to the KM ansatz - ${\cal O}(λ^2)$ and ${\cal O}(λ^4)$ thus generating an asymmetry of a few percent and of about 0.1 %, respectively. The former can be measured in $B_s \to ψη, ψϕ$ {\em without} hadronic uncertainty, the latter in Cabibbo suppressed D decays. The intervention of New Physics could boost these effects by an order of magnitude. A special case is provided by $D^+ \to K_{S,L}π^+$ vs. $D^- \to K_{S,L}π^-$. Finally, \cp~asymmetries involving $D^0 - \bar D^0$ oscillations could reach observable levels only due to New Physics.

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arXiv1999

On Limitations of T Invariance in K Decays

Data from the CPLEAR collaboration coupled with the assumption that the Bell-Steinberger relation holds have provided {\em direct} evidence for \ot~violation. In this note we investigate what we can say about \ot~violation {\em without} such an assumption. We show that both the modulus and the phase of $η_{+-}$ can be reproduced with \ot~{\em invariant} dynamics through finetuning \cpt~breaking. The large \ot~odd correlation observed by the KTeV collaboration in $K_L \to π^+π^- e^+ e^-$ thus does not yield direct evidence for \ot~violation. In such a world the phase of $\frac{ε'}ε$ is $δ_2-δ_0-ϕ_{SW}\sim -(85.5\pm 4)^\circ$. Also, $K^{\pm} \to π^{\pm} π^0$ could exhibit a \cpt~asymmetry of up to few$\times 10^{-3}$ without upsetting any known bound.

hep-ph↗
arXiv1999

Summary of Weak Decays, CKM and CP Violation Session Penguins

In our subgroup, we focused on penguin physics from various different angles. Our discussions included: (1) A method to extract one of the angles of the unitarity triangle $ϕ_2$; (2) Methods to extract $ϕ_3$ from $B\to Kπ$ decays; (3) Effects of non-minimal SUSY on B and K decays; (4) Understnding large branching ratios for $B\to η'+K(K^*)$ decays; (5) New calculation for hadronic matrix elements which are needed to compute $ε'/ε$.

hep-ph↗
arXiv1999

A short look at epsilon'/epsilon

We analyze the theoretical implications of the new KTeV measurement of direct CP-violation in K->pi pi decays. The result is found consistent with the Standard Model for low values of the strange quark mass m_s. If the hadronic parameters B_6^{(1/2)} and B_8^{(3/2)} satisfy 2 B_6^{(1/2)} - B_8^{(3/2)} < 2, as suggested by lattice and 1/N_c calculations, we find an upper bound of 110 MeV for m_s (2 GeV)$. We parametrize potential new physics contributions to ε'/εand illustrate their correlation with upper bounds on m_s. Finally we discuss a non-perturbative mechanism, which is not contained in the existing calculations of B_6^{(1/2)}. This mechanism enhances B_6^{(1/2)} and thereby leads to a better understanding of the Delta I=1/2 rule and the high measured value of Re (ε^\prime/ε)

hep-ph↗
arXiv1999

Comments on CPT tests

What do we know about CPT symmetry? We conclude that the direcrt measurement of CPT violation leads to a result that CPT violation force is limited to about 30% of CP violating forces. The best test of CPT symmetry is to see if theoretical prediction for the phase of eta_{+-} and eta_{00} agree with experiments. We discuss uncertainties associated with this prediction, and how to improve it. A new test of CPT is also discussed.

hep-ph↗
arXiv1999

Comments on the Sign of CP Asymmetries

Several experiments are about to measure the CP asymmetry for $B \to ψK_S$ and other decays. The standard model together with the Kobayashi-Maskawa ansatz for CP violation predicts the sign as well as the magnitude for this asymmetry. In this note we elucidate the physics and conventions which lead to the prediction for the sign of the asymmetry.

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arXiv1997

Getting at the CP Angles

In anticipation for intensive experimental effort on B physics, theorists have introduced many ingenious ways to measure properties of the unitarity triangle. We review some of these methods. We will be critical in the hope that, if there is any defect in them, it can be remedied either theoretically or experimentally.

hep-ph↗
arXiv1997

B->Xq l+ l- (q=d,s) and Determination of |Vtd/Vts|

We propose a new method to extract |Vtd/Vts| from the ratio of the decay distributions dR/ds = dB(B->Xdl+l-)/ds/dB(B->Xsl+l-)/ds. This ratio depends only on the KM ratio |Vtd/Vts| with 15% theoretical uncertainties, if dilepton invariant mass-squared s is away from the peaks of the possible resonance states, J/psi, psiprime, and etc. We also give a detailed analytical and numerical analysis on dB(B-Xql+l-)/ds (q=d,s) and dR/ds.

hep-ph↗
arXiv1997

Search for New Physics in CP-violating B Decays

We consider three possible scenarios of new physics in B^0_d-\bar{B}^0_d mixing and propose a simple framework for analyzing their effects. This framework allows us to study the CP asymmetry in semileptonic B_d decays ({\cal A}_{SL}) and those in nonleptonic transitions such as B_d \to J/ψK_S and B_d \to π^+π^-. Numerically we find that new physics may enhance the magnitude of {\cal A}_{SL} up to the percent level within the appropriate parameter space. So measurements of {\cal A}_{SL} and its correlation with other CP asymmetries will serve as a sensitive probe for new physics in B^0_d-\bar{B}^0_d mixing.

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