arXiv subjects

Andrei I. Onishchenko

Publications and source records attributed to Andrei I. Onishchenko.

8 recordsLinked to original sources

arXiv2026

Five legs @ three loops: slightly off-shell dual conformal integrals

We calculate the three-loop master integrals contributing to the three-loop five-point amplitude on the special Coulomb branch of $\mathcal{N}=4$ SYM theory. For the genuine pentagon integrals, we follow the approach of Ref. [JHEP 12 (2025) 107], which includes a regularization preserving dual conformal invariance (DCI). As a new ingredient, we introduce a simple method, allowing to factor out the dependence on the DCI cross ratios from the contribution of each region. The remaining integrals are then essentially simplified by taking successive limits of vanishing external invariants. For 3 out of 82 regions contributing to the most complicated integral $\mathcal{I}_5^{(3)}$ we were not able to perform the integration even after these simplifications. For these three regions, we perform the integration-by-parts (IBP) reduction in parametric representation and evaluate the resulting locally finite integrals using HyperInt.

hep-th↗

arXiv2025

Method of regions for dual conformal integrals

We apply the method of regions to the evaluation of dual conformal integrals with small off-shellness. In contrast to conventional approach, where the separation of regions is performed via dimensional regularization breaking the dual conformal invariance (DCI), we use a sufficiently generic combination of dimensional and analytic regularizations which preserves the DCI. Within this regularization (dubbed as DCI regularization), the contribution of each region becomes DCI. We show that our method dramatically simplifies the calculations. As a demonstration, we calculate the slightly off-shell DCI pentabox integral up to power corrections. The contributions of all 32 regions appear to be expressible in terms of products/ratios of $Γ$-functions multiplied by some powers of DCI cross-ratios. Therefore, after removing the regularization, we obtain the final expression in terms of cross-ratios logarithms only. We have checked that our result for pentabox integral numerically agrees with the result of the recent Belitsky\&Smirnov paper [arXiv:2508.14298] which has essentially more complicated form.

hep-th↗

arXiv2007

2-loop QCD corrections to Bc-meson leptonic constant

We present results for two-loop QCD corrections to the short distance coefficient that governs leptonic decay of Bc-meson. After brief discussion of the technics of asymptotic threshold expansion used to perform this calculation, we give comments on the numerical value of two-loop corrections and its impact on NRQCD description of Bc-meson bound state dynamics.

hep-ph↗

arXiv2004

Spectator effects and lifetimes of heavy hadrons

We present a calculation of subleading 1/m_b corrections to spectator effects in the ratios of beauty hadron lifetimes in heavy-quark expansion. We find that these effects are sizable and should be taken into account in systematic analyses of heavy hadron lifetimes. In particular, the inclusion of 1/m_b corrections brings into agreement the theoretical predictions and experimental observations of the ratio of lifetimes of Λ_b-baryon and B_d meson. We obtain τ(B_u)/τ(B_d) = 1.06 \pm 0.02, τ(B_s)/τ(B_d)= 1.00 \pm 0.01, τ(Λ_b)/τ(B_d)= 0.86 \pm 0.05.

hep-ph↗

arXiv2003

Lambda_b lifetime puzzle in heavy-quark expansion

Lifetime differences of heavy hadrons can be consistently computed in heavy-quark expansion. The leading effects appear through spectator interactions at order 1/m_b^3. We compute a well-defined subset of 1/m_b^4 corrections to the lifetime ratio of Lambda_b baryon and B_d meson. We find that these corrections are large and should be taken into account in the systematic analysis of heavy hadron lifetimes. We claim that they could shift the ratio τ_{Λ_b}/τ_{B_d} by as much as -4.5%, significantly reducing the discrepancy between the theoretical predictions and experimental observations.

hep-ph↗

arXiv2000

Exclusive decays of Xi(QQ') baryons in NRQCD sum rules

We perform a detailed study of semileptonic form-factors for the doubly heavy baryons in the framework of three-point NRQCD sum rules. The analyis of spin symmetry relations as well as numerical results on various exclusive decay modes of doubly heavy baryons are given.

hep-ph↗

arXiv2000

B_c - meson sum rules at next-to-leading order

We present B_c-meson two-point sum rules at next-to-leading order in NRQCD approximation. Analitycal results for perturbative spectral density and gluon condensate contribution with account for summed Coulomb corrections are given. Estimates of various c-quark masses together with couplings and masses of lowest lying B_c-meson resonances are performed.

hep-ph↗

arXiv1999

Doubly heavy systems: decays and OPE

We discuss questions related to the application of OPE for the long-lived systems with two heavy flavors. The values of quark masses entering such calulations are constrained by use of currently available data on the lifetimes of $B_d$ and $B_c$-mesons. The lifetimes of doubly charmed baryons at these values of parameters are evaluated. The necessary comments on the difference in the results obtained previously are made.

hep-ph↗