Comment on "On the TST_S-Anomaly in Betaine Calcium Chloride Dihydrate"

Recently, Hlinka and Ishibashi [J. Phys. Soc. Jpn. 67, 495 (1998)] discussed the $T_S$-anomaly in betaine calcium chloride dihydrate (BCCD) in a Landau-type approach. We comment on the shortcomings of this approach and discuss the $T_S$-anomaly in the framework of a microscopical pseudo spin model based on a realistic description of BCCD in terms of symmetry-adapted local modes.Comment: 2 pages, RevTex, submitted to J. Phys. Soc. Jp

Model-Independent Properties of the B-Meson Distribution Amplitude

The operator product expansion is used to obtain model-independent predictions for the first two moments of the renormalized B-meson light-cone distribution amplitude phi_+(omega,mu), defined with a cutoff omega<Lambda_UV. The leading hadronic power corrections are given in terms of the parameter Lambda(bar)=m_B-m_b. From the cutoff dependence of the zeroth moment an analytical expression for the asymptotic behavior of the distribution amplitude is derived, which exhibits a negative radiation tail for omega>>mu. By solving the evolution equation for the distribution amplitude, an integral representation for phi_+(omega,mu) is obtained in terms an initial function phi_+(omega,mu_0) defined at a lower renormalization scale. A realistic model of the B-meson light-cone distribution amplitude is proposed, which satisfies the moment relations and has the correct asymptotic behavior. This model provides an estimate for the first inverse moment and the associated parameter lambda_B.Comment: 8 pages, 5 figures; problem in Figure 4 fixed, references updated; version to appear in Phys. Rev.

New Bound on gamma from B^+- -> pi K Decays

A bound on the angle gamma of the unitarity triangle is derived using experimental information on the CP-averaged branching ratios for the rare decays B^+- -> pi^+- K^0 and B^+- -> pi^0 K^+-. The theoretical description is cleaner than the Fleischer-Mannel analysis of the decays B^+- -> pi^+- K^0 and B^0 -> pi^-+ K^+- in that the two decay rates differ only in a single isospin amplitude, which has a simple structure in the SU(3) limit. As a consequence, electroweak penguin contributions and strong rescattering effects can be taken into account in a model-independent way. The resulting bound excludes values of cos(gamma) around 0.6 and is thus largely complementary to indirect constraints derived from a global analysis of the unitarity triangle.Comment: minor corrections, version to appear in Physics Letters

Probing the density dependence of the symmetry potential with peripheral heavy-ion collisions

The peripheral heavy-ion collisions of $^{112, 124}Sn+ ^{86}Kr$ at $E_{b}= 25AMeV$ are studied by means of the Improved Quantum Molecular Dynamics Model(ImQMD). It is shown that the slope of the average N/Z ratio of emitted nucleons vs impact parameters for these reactions is very sensitive to the density dependence of the symmetry energy. Our study also shows that the yields of $^{3}H$ and $^{3}He$ decrease with impact parameters and slope of the yield of $^{3}H$ vs impact parameters as well as the ratio of Y($^{3}H$)/Y($^{3}He$) depend on the symmetry potential strongly for peripheral heavy-ion collisions.Comment: 10 pages,6 figures, accepted by Phys.Rev.

Low temperature phase diagram and critical behaviour of the four-state chiral clock model

The low temperature behaviour of the four-state chiral clock ($CC_4$) model is reexamined using a systematic low temperature series expansion of the free energy. Previously obtained results for the low temperature phases are corrected and the low temperature phase diagram is derived. In addition, the phase transition from the modulated region to the high temperature paraphase is shown to belong to the universality class of the 3d-XY model.Comment: 17 pages in ioplppt style, 3 figure

Extracting ∣Vbc∣|V_{bc}|, mcm_c and mbm_b from Inclusive DD and BB Decays

Using recent results for nonperturbative contributions to the $B$ and $D$ meson inclusive semileptonic widths, a model independent extraction of \vbc, $m_c$ and $m_b$ is made from the experimentally measured $B$ and $D$ lifetimes and semileptonic branching ratios. Constraining the parameters of the HQET at \CO(1/m_Q^2) by the $D$ semileptonic width, \vbc is found to lie in the range .040<\vbc< 0.057. The $c$ and $b$ quark masses are not well constrained due to uncertainty in the relevant scale of $\alpha_s$. These results assume the validity of perturbative QCD at the low scales relevant to semileptonic charm decay. Without making this assumption, somewhat less stringent bounds on $V_{bc}$ from $B$ decay alone may be obtained.Comment: (revised version - contains a more detailed discussion of the uncertainty in our results from the uncertainty in the scale of \alpha_s) 12 pages, 5 figures included, uses harvmac.tex and epsf.tex, UCSD/PTH 93-25, UTPT 93-21, CMU-HEP 93-1

Exploring CP Violation through B Decays

The B-meson system provides many strategies to perform stringent tests of the Standard-Model description of CP violation. In this brief review, we discuss implications of the currently available B-factory data on the angles alpha, beta and gamma of the unitarity triangle, emphasize the importance of Bs studies at hadronic B experiments, and discuss new, theoretically clean strategies to determine gamma.Comment: 22 pages, 4 figures, invited brief review for Modern Physics Letters

Long-Distance Dominance of the CP Asymmetry in B->X_{s,d}+gamma Decays

We show that in the Standard Model the parametrically leading (by a factor 1/alpha_s) contribution to the inclusive CP asymmetry in B->X_{s,d}+gamma decays arises from a long-distance effect in the interference of the electromagnetic dipole amplitude with the amplitude for an up-quark penguin transition accompanied by soft gluon emission. This contribution is governed by a single hadronic parameter Lambda_{17}^u related to a matrix elements of a non-local operator. In view of current experimental data, a future precision measurement of the flavor-averaged CP asymmetry in B->X_s+gamma will signal the presence of new physics only if a value below -2% is found. A cleaner probe of new physics is offered by the difference of the CP asymmetries in charged versus neutral B-meson decays.Comment: 4 page

Infrared singularities of scattering amplitudes in perturbative QCD

An exact formula is derived for the infrared singularities of dimensionally regularized scattering amplitudes in massless QCD with an arbitrary number of legs, valid at any number of loops. It is based on the conjecture that the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory contains only a single non-trivial color structure, whose coefficient is the cusp anomalous dimension of Wilson loops with light-like segments. Its color-diagonal part is characterized by two anomalous dimensions, which are extracted to three-loop order from known perturbative results for the quark and gluon form factors. This allows us to predict the three-loop coefficients of all 1/epsilon^k poles for an arbitrary n-parton scattering amplitudes, generalizing existing two-loop results.Comment: 4 pages; v2: typo in eq. (12) fixed, references updated; v3: additional term in (12

Hyperfine Interactions in Charm and Bottom Systems

Hyperfine interactions in the light meson and baryon sectors are generalized to the charm and bottom systems. It is pointed out that an attempt to increase the value of the wave function at the origin to account for the unusual ratio of $\Lambda_{b}$ to the $B^0$ lifetimes could spoil the good agreement among the baryon and meson hyperfine mass-splitting. Including spin effects and taking phase space differences into account we predict that the decay rate of the $\Lambda_{b}$ can be increased relative to that of the $B^0$ meson by about 7%.Comment: 10 pages, plain Latex, no figures. A new isospin argument has been adde