Quenched lattice calculation of semileptonic heavy-light meson form factors

We calculate, in the continuum limit of quenched lattice QCD, the matrix elements of the heavy-heavy vector current between heavy-light pseudoscalar meson states. We present the form factors for different values of the initial and final meson masses at finite momentum transfer. In particular, we calculate the non-perturbative correction to the differential decay rate of the process B --> D l nu including the case of a non-vanishing lepton mass.Comment: 16 pages, 10 figures, version accepted for publication on JHE

The three-loop beta function of SU(N) lattice gauge theories with Wilson fermions

We calculate the third coefficient of the lattice beta function associated with the Wilson formulation for both gauge fields and fermions. This allows us to evaluate the three-loop correction (linear in $g_0^2$) to the relation between the lattice Lambda-parameter and the bare coupling $g_0$, which is important in order to verify asymptotic scaling predictions. Our calculation also leads to the two-loop relation between the coupling renormalized in the MSbar scheme and $g_0$. The original version of this paper contained a numerical error in one of the diagrams, which has now been corrected. The calculations, as well as the layout of the paper have remained identical, but there are some important changes in the numerical results.Comment: One 14-page LaTeX file, one PostScript file containing 2 figures. Corrected a numerical error in one of the diagrams. The calculations, as well as the layout of the paper have remained unaffected, but there are some important changes in the numerical result

B spectroscopy using all-to-all propagators

We measure the ground and excited states for B mesons in the static limit using maximally variance reduced estimators for light quark propagators. Because of the large number of propagators we are able to measure accurately also orbitally excited P, D and F states. We also present some results for Lambda_b.Comment: 3 pages, 3 figures. Talk presented at Lattice '97 by J. Peis

Lattice Determination of the B∗BπB^\ast B \pi Coupling

The coupling $g_{B^\ast B \pi}$ is related to the form factor at zero momentum of the axial current between $B^\ast$ and $B$ states. Moreover it is related to the effective coupling between heavy mesons and pions that appear the heavy meson chiral Lagrangian. This coupling has been evaluated on the lattice using static heavy quarks and light quark propagators determined by a stochastic inversion of the fermionic bilinear. We found the value $g=0.42(4)(8)$. Beside its theoretical interest, this quantity has phenomenological implications in $B \to \pi + \bar l l$ decays.Comment: Lattice 99, 3 page

Quark bilinear step scaling functions and their continuum limit extrapolation

Some new results on nonperturbative renormalisation of quark bilinears in quenched QCD with Schroedinger Functional techniques are presented. Special emphasis is put on a study of the universality of the continuum limit for step scaling functions computed with different levels of O(a) improvement.Comment: Lattice2003(improve), 3 pages, 3 figure

Towards a lattice determination of the B∗BπB^\ast B \pi coupling

The coupling $g_{B^\ast B \pi}$ is related to the form factor at zero momentum of the axial current between $B^\ast$- and $B$-states. This form factor is evaluated on the lattice using static heavy quarks and light quark propagators determined by a stochastic inversion of the fermionic bilinear. The \gBBP coupling is related to the coupling $g$ between heavy mesons and low-momentum pions in the effective heavy meson chiral lagrangian. The coupling of the effective theory can therefore be computed by numerical simulations. We find the value $g = 0.42(4)(8)$. Besides its theoretical interest, the phenomenological implications of such a determination are discussed.Comment: 20 pages, 6 figure

Pericranial and scalp rotation flaps for occipitocervical hardware exposure with CSF leak in rheumatoid arthritis patient: A case report and review of the literature

Background: There are several etiologies of craniocervical junction instability (CCJI); trauma, rheumatoid arthritis (RA), infections, tumors, congenital deformity, and degenerative processes. These conditions often require surgery and craniocervical fixation. In rare cases, breakdown of such CCJI fusions (i.e., due to cerebrospinal fluid [CSF] leaks, infection, and wound necrosis) may warrant the utilization of occipital periosteal rescue flaps and scalp rotation flaps to achieve adequate closure. Case Description: A 33-year-old female with RA, cranial settling, and high cervical cord compression underwent an occipitocervical instrumented C0-C3/C4 fusion. Two months later, revision surgery was required due to articular screws pull out, CSF leakage, and infection. At the second surgery, the patient required screws removal, the application of laminar clamps, and sealing the leak with fibrin glue. However, the CSF leak persisted, and the skin edges necrosed leaving the hardware exposed. The third surgery was performed in conjunction with a plastic surgeon. It included operative debridement and covering the instrumentation with a pericranial flap. The resulting cutaneous defect was then additionally reconstructed with a scalp rotation flap. Postoperatively, the patient adequately recovered without sequelae. Conclusion: A 33-year-old female undergoing an occipitocervical fusion developed a postoperative persistent CSF leak, infection, and wound necrosis. This complication warranted the assistance of plastic surgery to attain closure. This required an occipital periosteal rescue flap with an added scalp rotation flap

Determination of B*B pi coupling in unquenched QCD

The $B^* B\pi$ coupling is a fundamental parameter of chiral effective Lagrangian with heavy-light mesons and can constrain the chiral behavior of $f_B$, $B_B$ and the $B\to \pi l \nu$ form factor in the soft pion limit. We compute the $B^* B \pi$ coupling with the static heavy quark and the $O(a)$-improved Wilson light quark. Simulations are carried out with $n_f=2$ unquenched $12^3\times 24$ lattices at $\beta=1.80$ and $16^3\times 32$ lattices at $\beta=1.95$ generated by CP-PACS collaboration. To improve the statistical accuracy, we employ the all-to-all propagator technique and the static quark action with smeared temporal link variables following the quenched study by Negishi {\it et al.}. These methods successfully work also on unquenched lattices, and determine the $B^*B\pi$ coupling with 1--2% statistical accuracy on each lattice spacing.Comment: 19pages,26figure

Improved Pseudofermion Approach for All-Point Propagators

Quark propagators with arbitrary sources and sinks can be obtained more efficiently using a pseudofermion method with a mode-shifted action. Mode-shifting solves the problem of critical slowing down (for light quarks) induced by low eigenmodes of the Dirac operator. The method allows the full physical content of every gauge configuration to be extracted, and should be especially helpful for unquenched QCD calculations. The method can be applied for all the conventional quark actions: Wilson, Sheikoleslami-Wohlert, Kogut-Susskind, as well as Ginsparg-Wilson compliant overlap actions. The statistical properties of the method are examined and examples of physical processes under study are presented.Comment: LateX, 26 pages, 10 eps figure