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Gang Yang - One of the best experts on this subject based on the ideXlab platform.
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the four loop cusp anomalous dimension from the n 4 sudakov Form Factor
Physics Letters B, 2020Co-Authors: Tobias Huber, Andreas Von Manteuffel, Erik Panzer, Robert M Schabinger, Gang YangAbstract:Abstract We present an analytic derivation of the full four-loop cusp anomalous dimension of N = 4 supersymmetric Yang-Mills theory from the Sudakov Form Factor. To extract the cusp anomalous dimension, we calculate the ϵ − 2 pole of the Form Factor using parametric integrations of finite integrals. We provide uniFormly transcendental results for the master integrals through to weight six and confirm a very recent independent analytic result for the full four-loop cusp anomalous dimension of the N = 4 model.
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the four loop cusp anomalous dimension from the mathcal n 4 sudakov Form Factor
arXiv: High Energy Physics - Theory, 2019Co-Authors: Tobias Huber, Andreas Von Manteuffel, Erik Panzer, Robert M Schabinger, Gang YangAbstract:We present an analytic derivation of the full four-loop cusp anomalous dimension of $\mathcal{N}=4$ supersymmetric Yang-Mills theory from the Sudakov Form Factor. To extract the cusp anomalous dimension, we calculate the $\epsilon^{-2}$ pole of the Form Factor using parametric integrations of finite integrals. We provide uniFormly transcendental results for the master integrals through to weight six and confirm a very recent independent analytic result for the full four-loop cusp anomalous dimension of the $\mathcal{N}=4$ model.
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master integrals for the four loop sudakov Form Factor
Nuclear Physics, 2016Co-Authors: Rutger H Boels, Bernd A Kniehl, Gang YangAbstract:Abstract The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally ( N = 4 ) supersymmetric Yang–Mills theory (SYM) in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. The simplest quantity which contains this correction is the four-loop two-point Form Factor of the stress tensor multiplet. This Form Factor was largely obtained in integrand Form in a previous work for N = 4 SYM, up to a free parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP) identities using a modified version of Reduze is reported. The Form Factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. Moreover, two of the integral topologies vanish after reduction. The appearing master integrals are cross-checked using independent algebraic-geometry techniques explored in the Mint package. The latter results provide the basis of master integrals applicable to generic Form Factors, including those in Quantum Chromodynamics. Discrepancies between explicitly solving the IBP relations and the MINT approach are highlighted. Remaining bottlenecks to completing the computation of the four-loop non-planar cusp anomalous dimension in N = 4 SYM and beyond are identified.
Aristizabal D Sierra - One of the best experts on this subject based on the ideXlab platform.
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impact of Form Factor uncertainties on interpretations of coherent elastic neutrino nucleus scattering data
Journal of High Energy Physics, 2019Co-Authors: Aristizabal D Sierra, Jiajun Liao, D MarfatiaAbstract:The standard model coherent elastic neutrino-nucleus scattering (CEνNS) cross section is subject to nuclear Form Factor uncertainties, mainly driven by the root-mean-square radius of the neutron density distribution. Motivated by COHERENT phases I-III and future multi-ton direct detection dark matter searches, we evaluate these uncertainties in cesium iodide, germanium, xenon and argon detectors. We find that the uncertainties become relevant for momentum transfers q ≳ 20 MeV and are essentially independent of the Form Factor parameterization. Consequently, Form Factor uncertainties are not important for CEνNS induced by reactor or solar neutrinos. Taking into account these uncertainties, we then evaluate their impact on measurements of CEνNS at COHERENT, the diffuse supernova background (DSNB) neutrinos and sub-GeV atmospheric neutrinos. We also calculate the relative uncertainties in the number of COHERENT events for different nuclei as a function of recoil energy. For DSNB and atmospheric neutrinos, event rates at a liquid argon detector can be uncertain to more than 5%. Finally, we consider the impact of Form Factor uncertainties on searches for nonstandard neutrino interactions, sterile neutrinos and neutrino generalized interactions. We point out that studies of new physics using CEνNS data are affected by neutron Form Factor uncertainties, which if not properly taken into account may lead to the misidentification of new physics signals. The uncertainties quantified here are also relevant for dark matter direct detection searches.
Vladimir A. Smirnov - One of the best experts on this subject based on the ideXlab platform.
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four loop quark Form Factor with quartic fundamental colour Factor
Journal of High Energy Physics, 2019Co-Authors: R N Lee, Vladimir A. Smirnov, Alexander V Smirnov, Matthias SteinhauserAbstract:We analytically compute the four-loop QCD corrections for the colour structure (d)2 to the massless non-singlet quark Form Factor. The computation involves non-trivial non-planar integral families which have master integrals in the top sector. We compute the master integrals by introducing a second mass scale and solving differential equations with respect to the ratio of the two scales. We present details of our calculational procedure. Analytical results for the cusp and collinear anomalous dimensions, and the finite part of the Form Factor are presented. We also provide analytic results for all master integrals expanded up to weight eight.
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The two-loop vector Form Factor in the Sudakov limit
European Physical Journal C, 2006Co-Authors: B. Jantzen, Vladimir A. SmirnovAbstract:Recently two-loop electroweak corrections to the neutral current four-fermion processes at high energies have been presented. The basic ingredient of this calculation is the evaluation of the two-loop corrections to the Abelian vector Form Factor in a spontaneously broken SU(2) gauge model. Whereas the final result and the derivation of the four-fermion cross sections from evolution equations have been published earlier, the calculation of the Form Factor from the two-loop Feynman diagrams is presented for the first time in this paper. We describe in detail the individual contributions to the Form Factor and their calculation with the help of the expansion by regions method and Mellin–Barnes representations.
D Marfatia - One of the best experts on this subject based on the ideXlab platform.
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impact of Form Factor uncertainties on interpretations of coherent elastic neutrino nucleus scattering data
Journal of High Energy Physics, 2019Co-Authors: Aristizabal D Sierra, Jiajun Liao, D MarfatiaAbstract:The standard model coherent elastic neutrino-nucleus scattering (CEνNS) cross section is subject to nuclear Form Factor uncertainties, mainly driven by the root-mean-square radius of the neutron density distribution. Motivated by COHERENT phases I-III and future multi-ton direct detection dark matter searches, we evaluate these uncertainties in cesium iodide, germanium, xenon and argon detectors. We find that the uncertainties become relevant for momentum transfers q ≳ 20 MeV and are essentially independent of the Form Factor parameterization. Consequently, Form Factor uncertainties are not important for CEνNS induced by reactor or solar neutrinos. Taking into account these uncertainties, we then evaluate their impact on measurements of CEνNS at COHERENT, the diffuse supernova background (DSNB) neutrinos and sub-GeV atmospheric neutrinos. We also calculate the relative uncertainties in the number of COHERENT events for different nuclei as a function of recoil energy. For DSNB and atmospheric neutrinos, event rates at a liquid argon detector can be uncertain to more than 5%. Finally, we consider the impact of Form Factor uncertainties on searches for nonstandard neutrino interactions, sterile neutrinos and neutrino generalized interactions. We point out that studies of new physics using CEνNS data are affected by neutron Form Factor uncertainties, which if not properly taken into account may lead to the misidentification of new physics signals. The uncertainties quantified here are also relevant for dark matter direct detection searches.
Alexander Khodjamirian - One of the best experts on this subject based on the ideXlab platform.
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pion light cone distribution amplitude from the pion electromagnetic Form Factor
Physical Review D, 2020Co-Authors: Shan Cheng, Alexander Khodjamirian, Aleksey V RusovAbstract:We suggest to probe the pion light-cone distribution amplitude, applying a dispersion relation for the pion electromagnetic Form Factor. Instead of the standard dispersion relation, we use the equation between the spacelike Form Factor ${F}_{\ensuremath{\pi}}({Q}^{2})$ and the integrated modulus of the timelike Form Factor. For ${F}_{\ensuremath{\pi}}({Q}^{2})$, the QCD light-cone sum rule with a dominant twist-2 term is used. Adopting for the pion twist-2 distribution amplitude a certain combination of the first few Gegenbauer polynomials, it is possible to fit their coefficients ${a}_{2,4,6,..}$. (Gegenbauer moments) from this equation, employing the measured pion timelike Form Factor. For the exploratory fit we use the data of the BABAR collaboration. The results definitely exclude the asymptotic twist-2 distribution amplitude. Also the model with a single ${a}_{2}\ensuremath{\ne}0$ is disfavored by the fit. Considering the models with ${a}_{ng2}\ensuremath{\ne}0$, we find that the fitted values of the second and fourth Gegenbauer moments cover the intervals ${a}_{2}(1\text{ }\text{ }\mathrm{GeV})=(0.22--0.33)$, ${a}_{4}(1\text{ }\text{ }\mathrm{GeV})=(0.12--0.25)$. The higher moments starting from ${a}_{8}$ are consistent with zero, albeit with large uncertainties. The spacelike pion Form Factor obtained in two different ways, from the dispersion relation and from the light-cone sum rule, agrees, within uncertainties, with the measurement by the Jefferson Lab ${F}_{\ensuremath{\pi}}$ collaboration.
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b meson distribution amplitude from the b π Form Factor
Physics Letters B, 2005Co-Authors: Alexander Khodjamirian, Thomas Mannel, Nils OffenAbstract:Abstract Employing the light-cone sum rule approach in QCD, we relate the B -meson distribution amplitude to the B → π Form Factor at zero momentum transfer. In leading order, the sum rule is converted into a simple expression for the inverse moment λ B of the distribution amplitude ϕ + B . Using as an input the B → π Form Factor calculated from the light-cone sum rule in terms of pion distribution amplitudes, we obtain an estimate: λ B = 460 ± 160 MeV . We investigate how this result is modified by the B -meson three-particle distribution amplitudes.
