Semi-numerical power expansion of Feynman integrals

I present an algorithm based on sector decomposition and Mellin-Barnes techniques to power expand Feynman integrals. The coefficients of this expansion are given in terms of finite integrals that can be calculated numerically. I show in an example the benefit of this method for getting the full analytic power expansion from differential equations by providing the correct ansatz for the solution. For method of regions the presented algorithm provides a numerical check, which is independent from any power counting argument.Comment: 12 pages, 1 figure Version with minor changes, finally accepted from JHE

Perturbative corrections to B to X_s gamma in supersymmetry at next-to-leading order

We give a brief overview about perturbative corrections to the inclusive decay mode B to X_s gamma in supersymmetric models.Comment: 7 pages, 4 figures, based on a plenary talk given by TH at the International Conference PHOTON 2011, Spa, Belgium, 22.-27.5.201

Analytic calculation of two-loop QCD corrections to b\to s\ell^+\ell^- in the high q^2 region

We present our results for the NNLL virtual corrections to the matrix elements of the operators O_1 and O_2 for the inclusive process b\to s\ell^+\ell^- in the kinematical region q^2>4m_c^2, where q^2 is the invariant mass squared of the lepton-pair. This is the first analytic two-loop calculation of these matrix elements in the high q^2 region. We give the matrix elements as an expansion in m_c/m_b and keep the full analytic dependence on q^2. Making extensive use of differential equation techniques, we fully automatize the expanding of the Feynman integrals in m_c/m_b. In coincidence with an earlier work where the master integrals where calculated numerically (Ghinculov et al.) we find that in the high q^2 region the \alpha_s corrections to the matrix elements calculated in the present paper lead to a decrease of the q^2-spectrum by 10%-15% relative to the NNLL result in which these contributions are put to zero and reduce the renormalization scale uncertainty to ~2%.Comment: 27 pages, 4 figures, 2 tables, mathematica and c++ code attached, minor changes and corrections of typo

B- -> pi- pi0/rho- rho0 to NNLO in QCD factorization

The approximate tree decays B- -> pi- pi0/rho- rho0 may serve as benchmark channels for testing the various theoretical descriptions of the strong interaction dynamics in hadronic B meson decays. The ratios of hadronic and differential semileptonic B -> pi l nu/rho l nu decay rates at maximum recoil provide particularly clean probes of the QCD dynamics. We confront the recent NNLO calculation in the QCD factorization framework with experimental data and find support for the factorization assumption. A detailed analysis of all tree-dominated B -> pi pi/pi rho/rho rho decay modes seems to favour somewhat enhanced colour-suppressed amplitudes, which may be accommodated in QCD factorization by a small value of the first inverse moment of the B meson light-cone distribution amplitude, lambda_B ~ 250 MeV. Precise measurements of the B -> rho l nu spectrum could help to clarify this point.Comment: 7 page

Hard spectator interactions in B to pi pi at order alpha_s^2

In the present thesis I discuss the hard spectator interaction amplitude in $B\to\pi\pi$ at NLO i.e. at $\mathcal{O}(\alpha_s^2)$. This special part of the amplitude, whose LO starts at $\mathcal{O}(\alpha_s)$, is defined in the framework of QCD factorization. QCD factorization allows to separate the short- and the long-distance physics in leading power in an expansion in \lqcd/m_b, where the short-distance physics can be calculated in a perturbative expansion in $\alpha_s$. Compared to other parts of the amplitude hard spectator interactions are formally enhanced by the hard collinear scale \sqrt{\lqcd m_b}, which occurs next to the $m_b$-scale and leads to an enhancement of $\alpha_s$. From a technical point of view the main challenges of this calculation are due to the fact that we have to deal with Feynman integrals that come with up to five external legs and with three independent ratios of scales. These Feynman integrals have to be expanded in powers of \lqcd/m_b. I will discuss integration by parts identities to reduce the number of master integrals and differential equations techniques to get their power expansions. A concrete implementation of integration by parts identities in a computer algebra system is given in the appendix. Finally I discuss numerical issues like scale dependence of the amplitudes and branching ratios. It will turn out that the NLO contributions of the hard spectator interactions are important but small enough for perturbation theory to be validComment: PhD thesi

Complete next-to-leading order gluino contributions to b--> s gamma and b--> s g

We present the first complete order alpha_s corrections to the Wilson coefficients (at the high scale) of the various versions of magnetic and chromomagnetic operators which are induced by a squark-gluino exchange. For this matching calculation, we work out the on-shell amplitudes b--> s gamma and b --> s g, both in the full and in the effective theory up to order alpha_s^2. The most difficult part of the calculation is the evaluation of the two-loop diagrams in the full theory; these can be split into two classes: a) diagrams with one gluino and a virtual gluon; b) diagrams with two gluinos or with one gluino and a four-squark vertex. Accordingly, the Wilson coefficients can be split into a part a) and a part b). While part b) of the Wilson coefficients is presented in this paper for the first time, part a) was given in (Bobeth et al.). We checked their results for the coefficients of the magnetic operators and found perfect agreement. Moreover, we work out the renormalization procedure in great detail. Our results for the complete next-to-leading order Wilson coefficients are fully analytic, but far too long to be printed. We therefore publish them in the form of a C++ program. They constitute a crucial building block for the phenomenological next-to-leading logarithmic analysis of the branching ratio Bbar --> X_s gamma in a supersymmetric model beyond minimal flavor violation.Comment: 38 pages, including c++ cod

LiberTEM/LiberTEM-live: 0.2.0

Homepage: https://libertem.github.io/LiberTEM-live GitHub repository: https://github.com/LiberTEM/LiberTEM-live PyPI: https://pypi.org/project/libertem-live/ LiberTEM-live is an extension module for LiberTEM that allows live data processing. Note LiberTEM-live is still experimental and under active development, including the overall architecture. New releases can include changes that break backwards compatibility until the code and architecture are proven in practical application and stabilized sufficiently. That being said, we encourage early experimental use, are happy to support real-world application and appreciate feedback! You can contact us by creating or commenting on an Issue on GitHub or in the LiberTEM Gitter chat . LiberTEM user-defined functions (UDFs) are designed to work without modification on both offline data and live data streams. That means all LiberTEM applications and LiberTEM-based modules can work with all supported detectors in LiberTEM-live. Installation The short version to install into an existing LiberTEM environment: ( libertem ) $ python -m pip install 'libertem-live' See the LiberTEM installation instructions for more details on installing LiberTEM. Detectors Quantum Detectors Merlin DECTRIS EIGER2-based Amsterdam Scientific Instruments CheeTah TPX3 See the documentation for details. Support for the Gatan K2 IS, ASI MPX3, and X-Spectrum cameras is currently under development. License LiberTEM-live is licensed under GPLv3. The I/O parts are also available under the MIT license, please see LICENSE files in the subdirectories for details. Acknowledgements We are very grateful for your continuing support for LiberTEM-live! See the acknowledgement page for a list of authors and contributors to LiberTEM-live and other LiberTEM projects. See also our info on funding and industry partners