On charm-mass dependent NNLO corrections to B -> Xs gamma
M. Misiak, A. Rehman, M. Steinhauser
备注：
8 pages, 3 figures. Contribution to the proceedings of RADCOR 2019 - 14th International Symposium on Radiative Corrections: Applications of Quantum Field Theory to Phenomenology, 9-13 September, 2019, Avignon, France. The version at arXiv is updated with respect to the one at PoS
The inclusive radiative decay of the B meson is known to provide strong constraints on many popular extensions of the Standard Model. Such constraints crucially depend on precision of the Standard Model predictions. One of the main contributions to the theoretical uncertainty is due to certain Next-to-Next-to-Leading Order QCD corrections whose values at the physical charm quark mass m_c have been estimated using interpolation between the m_c=0 and m_c >> m_b limits. A direct determination of such corrections at the physical value of m_c requires calculating hundreds of two-scale four-loop propagator diagrams with unitarity cuts. Applying the integration-by-parts method, we express the corrections in terms of master integrals. Asymptotic expansions of these integrals at m_c >> m_b serve as boundary conditions for differential equations in z=m_c^2/m_b^2 that are being numerically solved. Here, we present our final results for the diagrams involving massless and massive fermion loops on the gluon lines. For the two-body cuts, we confirm the analytical expressions and/or numerical fits that are already present in the literature. In the four-body case, we make the correction complete by including several diagrams that have previously been only estimated using interpolation in m_c. We also report the status of the ongoing calculation of the remaining diagrams where no closed fermion loops on the gluon lines are present.
We report on the status of the perturbative calculation in the QCD factorization framework to charmless hadronic B meson decays and present a compilation of available NNLO results.
We discuss the impact of the charm quark mass in the CTEQ NNLO global analysis of parton distribution functions of the proton. The $\bar{\rm MS}$ mass $m_c(m_c)$ of the charm quark is extracted in the S-ACOT-$χ$ heavy-quark factorization scheme at ${\cal O}(α_s^2)$ accuracy and found to be in agreement with the world-average value. Impact on $m_c(m_c)$ of combined HERA-1 data on semiinclusive charm production at HERA collider and contributing systematic uncertainties are reviewed.
NNLO Vertex Corrections in charmless hadronic B decays: Imaginary part
我们在QCD因式分解框架下计算了强子二体衰变的2圈顶点修正的虚部B -> pi pi。这完成了拓扑树振幅虚部的NNLO计算，并代表了QCD因式分解中直接CP不对称性的NNLO预测的重要一步。关于技术方面，我们发现，软共线红外发散取消硬散射内核，这表明因式分解在2圈顺序。所有的结果得到解析，包括依赖于粲夸克质量。数值的NNLO校正的影响被认为是显着的，特别是它们导致增强的强相位的颜色抑制树振幅。
One of the most popular definition for the charm-quark mass is the charm-quark pole mass $m_c^{\rm pole}$. In this contribution, we extract the charm-quark pole mass through perturbative Quantum Chromo Dynamics (pQCD) analysis up to the next-to-next-to-leading order (NNLO) corrections from HERA Combined and LHCb charm production recent data sets. Then, we investigate for the first time the charm-quark pole mass $m_c^{\rm pole}$ pure impact, as an extra pQCD parameter on the proton Parton Distribution Functions (PDFs) at the NNLO corrections.
We study the effect of the charm quark mass in the CTEQ global analysis of parton distribution functions (PDFs) of the proton. Constraints on the $\bar{\rm MS}$ mass of the charm quark are examined at the next-to-next-to-leading order (NNLO) accuracy in the S-ACOT-$χ$ heavy-quark factorization scheme. The value of the charm quark mass from the hadronic scattering data in the CT10 NNLO fit, including semiinclusive charm production in DIS at HERA collider, is found to agree with the world average value. Various approaches for constraining $m_{c}$ in the global analysis and impact on LHC cross se…
We discuss the theory prediction of epsilon_K and the rare K -> pi nu nu-bar decays and review the structure and current status of higher-order contributions to these flavour changing processes in the standard model in some detail. This includes the next-to-next-to-leading order QCD calculation to the charm quark contribution to K+ -> pi+ nu nu-bar and to the charm-top quark contribution to epsilon_K. Electroweak corrections to the rare kaon decays are also discussed.
We present a fully differential next-to-next-to-leading order calculation of charm quark production in charged-current deep-inelastic scattering, with full charm-quark mass dependence. The next-to-next-to-leading order corrections in perturbative quantum chromodynamics are found to be comparable in size to the next-to-leading order corrections in certain kinematic regions. We compare our predictions with data on dimuon production in (anti-)neutrino scattering from a heavy nucleus. Our results can be used to improve the extraction of the parton distribution function of a strange quark in the nu…
We present the next-to-next-to-leading order (NNLO) QCD corrections to the decay constants for both the pseudoscalar and vector beauty-charmed mesons $B_{c}$ and $B^*_{c}$ in nonrelativistic QCD effective theory. Explicit NNLO calculation verified that the $B_c$ decay constant from pseudoscalar current is identical with the $B_c$ decay constant from axial-vector current. The NNLO result for the vector decay constant of $B^*_{c}$ meson is novel. Combined with the latest extraction of nonrelativistic QCD long-distance matrix elements of $B_c$ meson, we give the branching ratios of leptonic decay…
Strengthening constraints on new physics from the B -> X_s gamma branching ratio requires improving accuracy in the measurements and the Standard Model predictions. To match the expected Belle-II accuracy, Next-to-Next-to-Leading Order (NNLO) QCD corrections must be calculated without the so-far employed interpolation in the charm-quark mass m_c. In the process of evaluating such corrections at the physical value of m_c, we have finalized the part coming from diagrams with closed fermion loops on the gluon lines that contribute to the interference of the current-current and photonic dipole ope…
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…
We discuss the prescription for the Dirac matrix gamma_5 in dimensional regularization used in most second- and third-order QCD calculations of collider cross sections. We provide an alternative implementation of this approach that avoids the use of an explicit form of gamma_5 and of its (anti-) commutation relations in the most important case of no more than one gamma_5 in each fermion trace. This treatment is checked by computing the third-order corrections to the structure functions F_2 and g_1 in charged-current deep-inelastic scattering with axial-vector couplings to the W-bosons. We deri…
NNLO corrections to inclusive semileptonic B decays in the shape-function region
我们计算了形状函数区域中B -> X_u l nu衰变因子分解公式中硬系数函数的双圈QCD修正。我们的计算提供了包含半轻子B衰变的NNLO分析所需的最后一个缺失的部分，这可能会显着降低CKM矩阵元素|V_ub|提取的理论不确定性。在技术方面，我们发现，2-回路硬系数函数是免费的红外奇异性的因式分解框架所预测的。我们执行一个简短的数值分析的NNLO修正，并包括魅力质量效应的讨论。
The main aim of this paper is to present new sets of non-perturbative fragmentation functions (FFs) for $D^0$ and $D^+$ mesons at next-to-leading (NLO) and, for the first time, at next-to-next-to-leading order (NNLO) in the $\overline{\mathrm{MS}}$ factorization scheme with five massless quark flavors. This new determination of FFs is based on the QCD fit to the {\tt OPAL} experimental data for hadron production in the electron-positron single-inclusive annihilation (SIA). We discuss in detail the novel aspects of the methodology used in our analysis and the validity of obtained FFs by compari…
Reanalysis of exclusive charmonium production at the $B$ factories
College of Physics and Optoelectronic Engineering, Chongqing Normal University（重庆师范大学物理与光电工程学院）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences, Chinese Academy of Sciences（中国科学院大学）
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We present details on calculation of next-to-next-to-leading order QCD corrections to massive charged-current coefficient functions in deep-inelastic scattering. Especially we focus on the application to charm-quark production in neutrino scattering on fixed target that can be measured via the dimuon final state. We construct a fast interface to the calculation so for any parton distributions the cross sections can be evaluated within milliseconds by using the pre-generated interpolation grids. We discuss agreements of various theoretical predicitons with the NuTeV and CCFR dimuon data and the…
One of the most important O($α_s^2$) corrections to the $B \to X_s γ$ branching ratio originates from interference of contributions from the current-current and photonic dipole operators. Its value has been estimated using an interpolation in the charm quark mass between the known results at $m_c=0$ and for $m_c \ll m_b/2$. An explicit calculation for the physical value of $m_c$ is necessary to remove the associated uncertainty. In the present work, we evaluate all the ultraviolet counterterm contributions that are relevant for this purpose.
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We present accurate predictions for the inclusive production of a Higgs boson in proton-proton collisions, via gluon-gluon fusion. Our calculation includes next-to-next-to-leading order (NNLO) corrections in perturbative QCD, as well as the resummation of threshold-enhanced contributions to next-to-next-to-next-to-leading logarithmic (N$^3$LL) accuracy, with the inclusion of the recently-determined three-loop constant coefficient (sometimes referred to as N$^3$LL' accuracy). Our result correctly accounts for finite top, bottom and charm masses at leading order (LO) and next-to-leading order (N…
We present details of our evaluation of the NNLO QCD corrections to BR(B -> X_s gamma) in the heavy charm limit m_c >> m_b/2. Results of this calculation have been essential for estimating O(alpha_s^2) effects in this branching ratio via interpolation in m_c.
