Introduction to XLOOPS

The program package XLOOPS calculates massive one- and two-loop Feynman diagrams. It consists of five parts: i) a graphical user interface ii) routines for generating diagrams from particle input iii) procedures for calculating one-loop integrals both analytically and numerically iv) routines for massive two-loop integrals v) programs for numerical integration of two-loop diagrams. The package relies on the application of parallel space techniques. The treatment of tensor structure and the separation of UV and IR divergences in analytic expressions is described in this scheme. All analytic calculations are performed with MAPLE. Two-loop examples taken from Standard Model calculations are presented. The method has recently been extended to all two-loop vertex topologies, including the crossed topology, graphs with divergent subloops and IR divergent diagrams. This will be included in the XLOOPS package in the near future.Comment: 30 pages, LaTeX, uses epsfi

Virtual annihilation contribution to orthopositronium decay rate

Order alpha^2 contribution to the orthopositronium decay rate due to one-photon virtual annihilation is found to be delta Gamma = (alpha/pi)^2 (pi^2 ln(alpha) - 0.8622(9))Gamma_LO.Comment: 2 pages, no figure

Double-Condensing Attention Condenser: Leveraging Attention in Deep Learning to Detect Skin Cancer from Skin Lesion Images

Skin cancer is the most common type of cancer in the United States and is estimated to affect one in five Americans. Recent advances have demonstrated strong performance on skin cancer detection, as exemplified by state of the art performance in the SIIM-ISIC Melanoma Classification Challenge; however these solutions leverage ensembles of complex deep neural architectures requiring immense storage and compute costs, and therefore may not be tractable. A recent movement for TinyML applications is integrating Double-Condensing Attention Condensers (DC-AC) into a self-attention neural network backbone architecture to allow for faster and more efficient computation. This paper explores leveraging an efficient self-attention structure to detect skin cancer in skin lesion images and introduces a deep neural network design with DC-AC customized for skin cancer detection from skin lesion images. The final model is publicly available as a part of a global open-source initiative dedicated to accelerating advancement in machine learning to aid clinicians in the fight against cancer

alpha^2 corrections to parapositronium decay: a detailed description

We present details of our recent calculation of alpha^2 corrections to the parapositronium decay into two photons. These corrections are rather small and our final result for the parapositronium lifetime agrees well with the most recent measurement. Implications for orthopositronium decays are briefly discussed.Comment: 18 pages, late

The photon energy spectrum in B-> X_s + \gamma in perturbative QCD through O(\alpha_s^2)

We derive the dominant part of the O(\alpha_s^2) correction to the photon energy spectrum in the inclusive decay B-> X_s+gamma. The detailed knowledge of the spectrum is important for relating the theoretical calculations of the B-> X_s + \gamma decay rate and the experimental measurements where a cut on the photon energy is applied. In addition, moments of the photon energy spectrum are used for the determination of the b-quark mass and other fundamental parameters of heavy quark physics. Our calculation reduces the theoretical uncertainty associated with uncalculated higher orders effects and shows that, for B-> X_s+\gamma, QCD radiative corrections to the photon energy spectrum are under theoretical control.Comment: 8 pages, 6 figures; references adde

Top quark production at threshold with O(alpha_s^2) accuracy

We calculate the next-to-next-to-leading order correction to the cross section for top quark pair production in e+e- annihilation in the threshold region, resumming all O [ (alpha_s/beta)^n (alpha_s^2, beta^2, alpha_s beta) ] terms of perturbation series. We find that the magnitude of the NNLO correction is comparable to the size of the NLO corrections.Comment: 15 pages, Latex, one figure, some misprints correcte

Order alpha_s^3 ln^2(1/alpha_s) Corrections to Heavy-Quarkonium Creation and Annihilation

In the framework of nonrelativistic QCD, we compute the leading double-logarithmic corrections of order alpha_s^3 ln^2(1/alpha_s) to the heavy-quark-antiquark bound-state wave function at the origin, which determines the production and annihilation rates of heavy quarkonia. The phenomenological implications for the top-antitop and Upsilon systems are discussed.Comment: 14 pages (Latex), 1 figures (Axodraw); text slightly extended, a few typos corrected, three references added; accepted for publication in Nucl. Phys.

Threshold expansion of the gg(qq) -> QQ+X cross section at O(alpha_s^4)

We derive the complete set of velocity-enhanced terms in the expansion of the total cross section for heavy-quark pair production in hadronic collisions at next-to-next-to-leading order. Our expression takes into account the effects of soft-gluon emission as well as that of potential-gluon exchanges. We prove that there are no enhancements due to subleading soft-gluon couplings multiplying the leading Coulomb singularity.Comment: 11 pages, 2 figures, published erratum included at the end of the paper, updated attached Mathematica fil

O(alpha^3 ln alpha) corrections to positronium decay rates

We compute O(alpha^3 ln alpha) corrections to the decay rates of para- and orthopositronium into two and three photons, respectively. For this calculation we employ the nonrelativistic QED regularized dimensionally and we explain how in this framework the logarithms of the fine structure constant can be extracted.Comment: 10 pages, revte