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[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

https://biblio.ugent.be/publication/685594/file/1130605.pdf

Review of Particle Physics

We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5 aMC@NLO, capable of handling all these computations — parton-level fixed order, shower-matched, merged — in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV e + e − collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way.

/pdf/the-automated-computation-of-tree-level-and-next-to-leading-4etm0g6w46.pdf

The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations

The Pythia program can be used to generate high-energy-physics ''events'', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as accurate as possible a representation of event properties in a wide range of reactions, within and beyond the Standard Model, with emphasis on those where strong interactions play a role, directly or indirectly, and therefore multihadronic final states are produced. The physics is then not understood well enough to give an exact description; instead the program has to be based on a combination of analytical results and various QCD-based models. This physics input is summarized here, for areas such as hard subprocesses, initial- and final-state parton showers, underlying events and beam remnants, fragmentation and decays, and much more. Furthermore, extensive information is provided on all program elements: subroutines and functions, switches and parameters, and particle and process data. This should allow the user to tailor the generation task to the topics of interest.

/pdf/pythia-6-4-physics-and-manual-3dvwmijpnq.pdf

PYTHIA 6.4 Physics and Manual

We present the inconsistencies which arise in quenched QCD in?I =½ non-leptonic kaon decays using chiral perturbation theory (?PT) to one loop. In particular we discuss how the lack of unitarity of the quenched theory invalidates the usual methods for the extraction of matrix elements from correlation functions.

/pdf/effects-of-quenching-in-delta-i-1-2-kaon-decays-4w1prm5005.pdf

Effects of quenching in delta(I) = 1/2 kaon decays

We present the first lattice calculation of the B-meson binding energy $\labar$ and of the kinetic energy $-\lambda_1/2 m_Q$ of the heavy-quark inside the pseudoscalar B-meson. This calculation has required the non-perturbative subtraction of the power divergences present in matrix elements of the Lagrangian operator $\bar h D_4 h$ and of the kinetic energy operator $\bar h \vec D^2 h$. The non-perturbative renormalisation of the relevant operators has been implemented by imposing suitable renormalisation conditions on quark matrix elements, in the Landau gauge. Our numerical results have been obtained from several independent numerical simulations at $\beta=6.0$ and $6.2$, and using, for the meson correlators, the results obtained by the APE group at the same values of $\beta$. Our best estimate, obtained by combining results at different values of $\beta$, is $\labar =190 \err{50}{30}$ MeV. For the $\overline{MS}$ running mass, we obtain $\overline {m}_b(\overline {m}_b) =4.17 \pm 0.06$ GeV, in reasonable agreement with previous determinations. From a subset of 36 configurations, we were only able to establish a loose upper bound on the $b$-quark kinetic energy in a $B$-meson, $\lambda_1=\langle B \vert \bar h \vec{D}^{2} h \vert B \rangle /(2 M_B )<$~1\, GeV$^2$. This shows that a much larger statistical sample is needed to determine this important parameter.

First Lattice Calculation of The B-meson Binding and Kinetic Energies

It is proposed to compute matrix elements for the (unphysical) $K^0\pi^-\to \pi^-$ transition to determine the next-to-leading order low energy constants of the weak chiral Lagrangian. This allows us to evaluate $K\to(\pi\pi)_{I=0}$ decay amplitudes at this level of precision. This approach has several significant advantages over the use of $K\to\pi\pi$ transitions, most notably the elimination of s-channel disconnected diagrams and the use of fewer inversions.

Using $K^0\pi^-\to\pi^-$ transitions to compute $K\to(\pi\pi)_{I=0}$ decay amplitudes at NLO in the chiral expansion

We present preliminary results from the RBC and UKQCD collaborations for the Kl3 form factor f0Kπ (0) = f+Kπ (0) with 2+1 flavours of dynamical domain wall quarks. Simulations are performed on 163×32×16 and 243×64×16 lattices with three values of the light quark mass, allowing for an extrapolation to the chiral limit.

/pdf/k-to-psemileptonic-form-factor-with-2-1-flavor-domain-wall-544g4v8nn0.pdf

Christopher T. Sachrajda

Papers

Effects of quenching in delta(I) = 1/2 kaon decays

First Lattice Calculation of The B-meson Binding and Kinetic Energies

Using $K^0\pi^-\to\pi^-$ transitions to compute $K\to(\pi\pi)_{I=0}$ decay amplitudes at NLO in the chiral expansion

K to πsemileptonic form factor with 2+1 flavor domain wall Fermions on the lattice

domain wall fermions