What is the Physics behind the 3He-4He Anomaly ?

We show that coalescence of nucleons emitted prior to thermalization in highly excited nuclei can explain the anomaly of kinetic energies of helium clusters. A new coalescence algorithm has been included into the statistical approach to nuclear reactions formerly used to describe intermediate mass fragment production.Comment: 5 pages, 4 figures, accepted at Eur. Phys.

Higher-order estimates of the chromomagnetic moment of a heavy quark

The leading beta_0^(n-1) alpha_s^n terms in the Wilson coefficient and anomalous dimension of the chromomagnetic operator in the heavy-quark effective Lagrangian are summed to all orders of perturbation theory. The perturbation series for the anomalous dimension is well behaved, while that for the Wilson coefficient exhibits a divergent behaviour already in low orders, caused by a nearby infrared renormalon singularity. The resulting ambiguity is commensurate with terms of order 1/m^2 in the effective Lagrangian, whose corresponding ultraviolet renormalons are identified. An excellent approximation for the scheme-invariant Wilson coefficient at next-to-next-to-leading order in renormalization-group improved perturbation theory is obtained.Comment: 16 pages, 3 figures embedde

Two-Loop Renormalization of Heavy--Light Currents at Order 1/m_Q in the Heavy-Quark Expansion

We present exact results, at next-to-leading order in renormalization-group improved perturbation theory, for the Wilson coefficients appearing at order 1/m_Q in the heavy-quark expansion of heavy-light current operators. To this end, we complete the calculation of the corresponding two-loop anomalous dimension matrix. Our results are important for determinations of |V_{ub}| using exclusive and inclusive semileptonic B decays. They are also relevant to computations of the decay constant f_B based on a heavy-quark expansion.Comment: 16 pages, 2 figures; third author added and one reference updated, results unchange

Slope of the Isgur-Wise function in the heavy mass limit of quark models \`a la Bakamjian-Thomas

The slope of the Isgur-Wise function for ground state mesons is evaluated for the heavy mass limit of quark models \`a la Bakamjian-Thomas, which has been previously discussed by us in general terms. A full calculation in various spectroscopic models with relativistic kinetic energy gives a rather stable result $\rho^2 \approx 1$, much lower than previous estimates. Attention is paid to a careful comparison of this result with the ones of QCD fundamental methods (lattice QCD, QCD sum rules) and with experimental data.Comment: 15 pages, Latex, AMS-LaTe

Phenomenology of B -> pi pi, pi K Decays at O(alpha^2 beta_0) in QCD Factorization

We study O(alpha^2 beta_0) perturbative corrections to matrix elements entering two-body exclusive decays of the form B -> pi pi, pi K in the QCD factorization formalism, including chirally enhanced power corrections, and discuss the effect of these corrections on direct CP asymmetries, which receive their first contribution at O(alpha). We find that the O(alpha^2 beta_0) corrections are often as large as the O(alpha) corrections. We find large uncertainties due to renormalization scale dependence as well as poor knowledge of the non-perturbative parameters. We assess the effect of the perturbative corrections on the direct CP violation parameters of B -> pi^+ pi^-.Comment: 27 pages, 5 figures. Updated input parameters and added citations; expanded discussio

A Consistent Calculation of Heavy Meson Decay Constants and Transition Wave Functions in the Complete HQEFT

Within the complete heavy quark effective field theory (HQEFT), the QCD sum rule approach is used to evaluate the decay constants including 1/m_Q corrections and the Isgur-Wise function and other additional important wave functions concerned at 1/m_Q for the heavy-light mesons. The 1/m_Q corrections to the scaling law f_M \sim F/\sqrt{m_M} are found to be small in HQEFT, which demonstrates again the validity of 1/m_Q expansion in HQEFT. It is also shown that the residual momentum v.k of heavy quark within hadrons does be around the binding energy \bar{\Lambda} of the heavy hadrons. The calculations presented in this paper provide a consistent check on the HQEFT and shows that the HQEFT is more reliable than the usual HQET for describing a slightly off-mass shell heavy quark within hadron as the usual HQET seems to lead to the breakdown of 1/m_Q expansion in evaluating the meson decay constants. It is emphasized that the introduction of the `dressed heavy quark' mass is useful for the heavy-light mesons (Qq) with m_Q >> \bar{\Lambda} >> m_q, while for heavy-heavy bound states (\psi_1\psi_2) with masses m_1, m_2 >> \bar{\Lambda}, like bottom-charm hadrons or similarly for muonium in QED, one needs to treat both particles as heavy effective particles via 1/m_1 and 1/m_2 expansions and redefine the effective bound states and modified `dressed heavy quark' masses within the HQEFT.Comment: 20 pages, revtex, 22 figures, axodraw.sty, two irrelevant figures are moved awa

A priori mixing of mesons and the |Delta I|=1/2 rule in K\to\pi\pi

We consider the hypothesis of a priori mixings in the mass eigenstates of mesons to obtain the |Delta I|=1/2 rule in K\to\pi\pi. The Hamiltonian responsible for the transition is the strong interacting one. The experimental data are described using the isospin symmetry relations between the strong coupling constants

Hadronic Spectral Moments in Semileptonic B Decays With a Lepton Energy Cut

We compute the first two moments of the final hadronic invariant mass in inclusive semileptonic B decay, in the presence of a cut on the charged lepton energy. These moments may be measured directly by experiments at the Upsilon(4S) using the neutrino reconstruction technique, which requires such a cut. Measurement of these moments will place constraints on the nonperturbative parameters \bar\Lambda and \lambda_1, which are relevant for extracting the quark masses m_b and m_c, as well as the CKM angle V_cb. We include terms of order \alpha_s^2\beta_0 and 1/m_b^3 in the operator product expansion, and use the latter to estimate the theoretical uncertainty in the extraction of \bar\Lambda and \lambda_1.Comment: 13 pages, 5 figures, REVTe

The Mass Definition in Hqet and a New Determination of Vcb_{\text{cb}}

Positive powers of the mass parameter in a physical quantity calculated with the help of heavy quark effective theory originate from a Wilson coefficient in the matching of QCD and HQET Green function. We show that this mass parameter enters the calculation as a well--defined running current mass. We further argue that the recently found ill--definition of the pole mass, which is the natural expansion parameter of HQET, does not affect a phenomenological analysis which uses truncated perturbative series. We reanalyse inclusive semileptonic decays of heavy mesons and obtain the $c$ quark mass $m_c^{\overline{\text{MS}}}(m_c) = (1.35\pm 0.20)\,\text{GeV}$ where the error is almost entirely due to scale--uncertainties. We also obtain $m_b^{\overline{\text{MS}}}(m_b) = (4.6\pm 0.3)\,\text{GeV}$ and $|V_{cb}|(\tau_B/1.49\,\text{ps})^{1/2} = 0.036\pm 0.005$ where the errors come from the uncertainty in the kinetic energy of the heavy quark inside the meson, in the experimental branching ratios, in QCD input parameters, and scale--uncertainties.Comment: 21 p., 5 figs, all style files incl., TUM-T31-56/R (Sec. 2 revised, phenomenological results unchanged