arXiv subjects

J. Rittinger

Publications and source records attributed to J. Rittinger.

7 recordsLinked to original sources

arXiv2013

Penguin diagrams in the charm sector in K+ --> pi+ nu anti-nu

We evaluate at next-to-next-to-leading order (NNLO) the QCD corrections to the charm contribution from penguin diagrams to the decay K+ --> pi+ nu anti-nu. A NNLO calculation is already available in the literature. We provide an independent check of the results of non-anomalous and anomalous diagrams. We use Renormalization Group improvement and an effective theory framework to resum the large logarithms that appear. In the case of the non-anomalous diagrams, our results for the decoupling coefficients and anomalous dimensions, as well as the final numerical result, are in agreement with those of the previous calculation. In the anomalous case, analytical and numerical disagreements are observed.

hep-ph↗

arXiv2012

R(s) and Z decay in order α_s^4: complete results

We report on our calculation of the order α_s^4 axial singlet contributions for the decay rates of the Z-boson as well as the vector singlet contribution to the cross section for electron-positron annihilation into hadrons. Together with recently finished O(α_s^4) calculations of the non-signlet corrections [1,2], the new results directly lead us to the first complete O(α_s^4) predictions for the total hadronic decay rate of the Z-boson and the ratio R(s).

hep-ph↗

arXiv2012

Vector Correlator in Massless QCD at Order O(alpha_s^4) and the QED beta-function at five loop

We present a concise summary of recent results for the vector correlator in massless QCD at order ${\cal O}(α_s^4)$, with all colour factors being given for a generic colour group. As a direct consequence we arrive at: (i) the full QCD contribution to the QED $β$--function of order $α^2\, α_s^4$ in the MSbar- and MOM-schemes; (ii) the full five-loop result of order $α^6$ for the $β$-function of QED with a generic number of single-charged fermions, again for the MSbar- and MOM-schemes.

hep-ph↗

arXiv2012

Adler Function, Sum Rules and Crewther Relation of Order O(alpha_s^4): the Singlet Case

The analytic result for the singlet part of the Adler function of the vector current in a general gauge theory is presented in five-loop approximation. Comparing this result with the corresponding singlet part of the Gross-Llewellyn Smith sum rule [1], we successfully demonstrate the validity of the generalized Crewther relation for the singlet part. This provides a non-trivial test of both our calculations and the generalized Crewther relation. Combining the result with the already available non-singlet part of the Adler function [2,3] we arrive at the complete ${\cal O}(α_s^4)$ expression for the Adler function and, as a direct consequence, at the complete ${\cal O}(α_s^4)$ correction to the $e^+ e^-$ annihilation into hadrons in a general gauge theory.

hep-ph↗

arXiv2012

Complete QCD Corrections to Hadronic $Z$--Decays in Order $α_s^4$

Corrections of order $α_s^4$ for the axial singlet contributions for the decay rates of the $Z$-boson into hadrons are evaluated in the limit of the heavy top quark mass. Combined with recently finished ${\cal O}(α_s^4)$ calculations of the non-signlet corrections, the new results directly lead us to the first {\em complete} ${\cal O}(α_s^4)$ prediction for the total hadronic decay rate of the Z-boson. The new ${\cal O}(α_s^4)$ term in Z-decay rate lead to a significant stabilization of the perturbative series, to a reduction of the theory uncertainty in the strong coupling constant $α_s$, as extracted from these measurements, and to a small shift of the central value.

hep-ph↗

arXiv2010

Electroweak Sudakov Logarithms and Real Gauge-Boson Radiation in the TeV Region

Electroweak radiative corrections give rise to large negative, double-logarithmically enhanced corrections in the TeV region. These are partly compensated by real radiation and, moreover, affected by selecting isospin-noninvariant external states. We investigate the impact of real gauge boson radiation more quantitatively by considering different restricted final state configurations. We consider successively a massive abelian gauge theory, a spontaneously broken SU(2) theory and the electroweak Standard Model. We find that details of the choice of the phase space cuts, in particular whether a fraction of collinear and soft radiation is included, have a strong impact on the relative amount of real and virtual corrections.

hep-ph↗

arXiv2008

XQuery Join Graph Isolation

A purely relational account of the true XQuery semantics can turn any relational database system into an XQuery processor. Compiling nested expressions of the fully compositional XQuery language, however, yields odd algebraic plan shapes featuring scattered distributions of join operators that currently overwhelm commercial SQL query optimizers. This work rewrites such plans before submission to the relational database back-end. Once cast into the shape of join graphs, we have found off-the-shelf relational query optimizers--the B-tree indexing subsystem and join tree planner, in particular--to cope and even be autonomously capable of "reinventing" advanced processing strategies that have originally been devised specifically for the XQuery domain, e.g., XPath step reordering, axis reversal, and path stitching. Performance assessments provide evidence that relational query engines are among the most versatile and efficient XQuery processors readily available today.

cs.DB↗