54 research outputs found
B -> D* l nu and B -> D l nu form factors in staggered chiral perturbation theory
We calculate the B -> D and B -> D* form factors at zero recoil in Staggered
Chiral Perturbation Theory. We consider heavy-light mesons in which only the
light (u, d, or s) quark is staggered; current lattice simulations generally
use a highly improved action such as the Fermilab or NRQCD action for the heavy
(b or c) quark. We work to lowest nontrivial order in the heavy quark expansion
and to one-loop in the chiral expansion. We present results for a partially
quenched theory with three sea quarks in which there are no mass degeneracies
(the "1+1+1" theory) and for a partially quenched theory in which the u and d
sea quark masses are equal (the "2+1" theory). We also present results for full
(2+1) QCD, along with a numerical estimate of the size of staggered
discretization errors. Finally, we calculate the finite volume corrections to
the form factors and estimate their numerical size in current lattice
simulations.Comment: 19 pages, 6 figures, references added, expanded discussion in Section
I
Topological fermion condensates from anomalies
We show that a class of fermion theory formulated on a compact, curved
manifold will generate a condensate whose magnitude is determined only by the
volume and Euler characteristic of the space. The construction requires that
the fermions be treated as K\"{a}hler-Dirac fields and the condensate arises
from an anomaly associated with a global symmetry which is subsequently
broken to a discrete subgroup. Remarkably the anomaly survives under
discretization of the space which allows us to compute the condensate on an
arbitrary triangulation. The results, being topological in character, should
hold in a wide range of gravitationally coupled fermion theories both classical
and quantumComment: 10 pages, 2 figures, 2 tables. minor corrections. Version published
in JHE
Lattice quantum gravity with scalar fields
We consider the four-dimensional Euclidean dynamical triangulations lattice
model of quantum gravity based on triangulations of . We couple it
minimally to a scalar field in the quenched approximation. Our results suggest
a multiplicative renormalization for the mass of the scalar field which is
consistent with the shift symmetry of the discretized lattice action. We
discuss the possibility of measuring the mass anomalous dimension and the
gravitational binding energy between two scalar test particles, where a
negative bound state energy would imply that this model has an attractive
gravitational force.Comment: 1+6 pages, proceedings for the 36th International Symposium on
Lattice Field Theory (22-28 July 2018). v2 -- Added one reference and fixed a
typo. Comments welcome
Quenching effects in strong penguin contributions to
Quenching effects in strong penguin matrix elements are investigated. A
lattice determination of , the constant that appears in the
quenched ChPT relevant for the lattice analysis of matrix
elements, shows that this constant is large. The original RBC analysis of
matrix elements is revisited in light of this result. Also, the numerical
effects of choosing the singlet Golterman-Pallante method of quenching is
investigated.Comment: 3 pages, talk presented at Lattice2004(weak), Fermilab, June 21-26,
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