27 research outputs found
Non-perturbative tests of HQET in small-volume quenched QCD
We quantitatively investigate the quark mass dependence of current matrix
elements and energies, calculated over a wide range of quark masses in the
continuum limit of small-volume quenched lattice QCD. By a precise comparison
of these observables as functions of the heavy quark mass with the predictions
of HQET we are able to verify that their large quark mass behaviour is
described by the effective theory.Comment: Lattice2004(heavy), 3 pages, latex2e, uses espcrc
Indoleamine 2,3-Dioxygenase in Human Hematopoietic Stem Cell Transplantation
In recent years tryptophan metabolism and its rate limiting enzyme indoleamine 2,3-dioxygenase (IDO) have attracted increasing attention for their potential to modulate immune responses including the regulation of transplantation tolerance. The focus of this review is to discuss some features of IDO activity which particularly relate to hematopoietic stem cell transplantation (HSCT). HSCT invariably involves the establishment of some degree of a donor-derived immune system in the recipient. Thus, the outstanding feature of tolerance in HSCT is that in this type of transplantation it is not rejection, which causes the most severe problems to HSCT recipients, but the reverse, graft-versus-host (GvH) directed immune responses. We will discuss the peculiar role of IDO activity and accelerated tryptophan metabolism at the interface between immune activation and immune suppression and delineate from theoretical and experimental evidence the potential significance of IDO in mediating tolerance in HSCT. Finally, we will examine therapeutic options for exploitation of IDO activity in the generation of allo-antigen-specific tolerance, i.e. avoiding allo-reactivity while maintaining immunocompetence, in HSCT
The Muon g-2
The muon anomalous magnetic moment is one of the most precisely measured
quantities in particle physics. In a recent experiment at Brookhaven it has
been measured with a remarkable 14-fold improvement of the previous CERN
experiment reaching a precision of 0.54ppm. Since the first results were
published, a persisting "discrepancy" between theory and experiment of about 3
standard deviations is observed. It is the largest "established" deviation from
the Standard Model seen in a "clean" electroweak observable and thus could be a
hint for New Physics to be around the corner. This deviation triggered numerous
speculations about the possible origin of the "missing piece" and the increased
experimental precision animated a multitude of new theoretical efforts which
lead to a substantial improvement of the prediction of the muon anomaly
a_mu=(g_mu-2)/2. The dominating uncertainty of the prediction, caused by strong
interaction effects, could be reduced substantially, due to new hadronic cross
section measurements in electron-positron annihilation at low energies. Also
the recent electron g-2 measurement at Harvard contributes substantially to the
progress in this field, as it allows for a much more precise determination of
the fine structure constant alpha as well as a cross check of the status of our
theoretical understanding.Comment: 134 pages, 68 figure
Non-perturbative tests of HQET in small-volume quenched QCD
We quantitatively investigate the quark mass dependence of current matrix elements and energies, calculated over a wide range of quark masses in the continuum limit of small-volume quenched lattice QCD. By a precise comparison of these observables as functions of the heavy quark mass with the predictions of HQET we are able to verify that their large quark mass behaviour is described by the effective theory
Non-perturbative tests of Heavy Quark Effective Theory
We consider QCD with one massless quark and one heavy quark in a finite volume of linear extent L_0 ~ 0.2 fm. In this situation, HQET represents an expansion in terms of 1/z=1/(m L_0), which we test by a non-perturbative computation of quenched current matrix elements and energies, taking the continuum limit of lattice results. These are seen to approach the corresponding renormalization group invariant matrix elements of the static effective theory as the quark mass becomes large. We are able to obtain estimates of the size of the 1/m-corrections to the static theory, which are also of practical relevance in our recent strategy to implement HQET non-perturbatively by matching to QCD in a finite volume