Siebren Reker

Light hadrons from lattice QCD with light (u, d), strange and charm dynamical quarks

We present results of lattice QCD simulations with mass-degenerate up and down and mass-split strange and charm (Nf = 2 + 1 + 1) dynamical quarks using Wilson twisted mass fermions at maximal twist. The tuning of the strange and charm quark masses is performed at two values of the lattice spacing a ≈ 0:078 fm and a ≈ 0:086 fm with lattice sizes ranging from L ≈ 1:9 fm to L ≈ 2:8 fm. We measure with high statistical precision the light pseudoscalar mass mPS and decay constant fPS in a range 270 ≲ mPS ≲ 510 MeV and determine the low energy parameters f0 and

Computing K and D meson masses with N_f = 2+1+1 twisted mass lattice QCD

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Computing K and D meson masses with N-f=2+1+1 twisted mass lattice QCD

of SU(2) chiral perturbation theory. We use the two values of the lattice spacing, several lattice sizes as well as different values of the light, strange and charm quark masses to explore the systematic effects. A first study of discretisation effects in light-quark observables and a comparison to Nf = 2 results are performed.

Kinetic analysis of the thermal isomerisation pathways in an asymmetric double azobenzene switch

We discuss the computation of the mass of the K and D mesons within the framework of N-f = 2 + 1 + 1 twisted mass lattice QCD from a technical point of view. These quantities are essential, already at the level of generating gauge configurations, being obvious candidates to tune the strange and charm quark masses to their physical values. In particular, we address the problems related to the twisted mass flavor and parity symmetry breaking, which arise when considering a non-degenerate (c, s) doublet. We propose and verify the consistency of three methods to extract the K and D meson masses in this framework. (c) 2010 Elsevier By. All rights reserved.

eta and eta ' mesons from N-f=2+1+1 twisted mass lattice QCD

We discuss the computation of the mass of the K and D mesons within the framework of N-f = 2 + 1 + 1 twisted mass lattice QCD from a technical point of view. These quantities are essential, already at the level of generating gauge configurations, being obvious candidates to tune the strange and charm quark masses to their physical values. In particular, we address the problems related to the twisted mass flavor and parity symmetry breaking, which arise when considering a non-degenerate (c, s) doublet. We propose and verify the consistency of three methods to extract the K and D meson masses in this framework. (c) 2010 Elsevier By. All rights reserved.

Lemon: An MPI parallel I/O library for data encapsulation using LIME

Here we report a photochemical and kinetic study of the thermal relaxation reaction of a double azobenzene system, in which two azobenzene photochromic units are connected via a phenyl ring. Upon UV irradiation, three thermally unstable isomers are formed. Kinetic studies using arrayed (1)H-NMR spectroscopy revealed four distinct barriers for the thermal reversion to the stable isomer. The double isomerised Z,Z-2 can revert thermally to the E,E-2 isomer via either of two isomerisation pathways. The thermal Z to E isomerisations are not significantly affected by the state of the neighbouring azo-switching unit in the meta position. These findings are supported by quantum chemical calculations on the thermal Z to E isomerisation.

Kaon and D meson masses with N_f = 2+1+1 twisted mass lattice QCD

A bstract We determine mass and mixing angles of η and η′ states using Nf = 2 + 1 + 1 Wilson twisted mass lattice QCD. We describe how those flavour singlet states need to be treated in this lattice formulation. Results are presented for three values of the lattice spacing, a = 0.061 fm, a = 0.078 fm and a = 0.086 fm, with light quark masses corresponding to values of the charged pion mass in a range of 230 to 500 MeV and fixed bare strange and charm quark mass values. We obtain Mη = 557(15)(45) MeV (first error statistical, second systematic) and ϕ = 44(5)° for a single mixing angle in the quark flavour basis, θ = −10(5)° in the octet-singlet basis.

Partially quenched study of strange baryon with Nf = 2 twisted mass fermions

We introduce Lemon, an MPI parallel I/O library that provides efficient parallel I/O of both binary and metadata on massively parallel architectures. Motivated by the demands of the lattice Quantum Chromodynamics community, the data is stored in the SciDAC Lattice QCD Interchange Message Encapsulation format. This format allows for storing large blocks of binary data and corresponding metadata in the same file. Even if designed for LQCD needs, this format might be useful for any application with this type of data profile. The design, implementation and application of Lemon are described. We conclude with presenting the excellent scaling properties of Lemon on state-of-the-art high performance computers. Program summary Program title: Lemon Catalogue identifier: AELP_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AELP_v1_0.html Program obtainable from: CPC Program Library, Queens University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 32 860 No. of bytes in distributed program, including test data, etc.: 223 762 Distribution format: tar.gz Programming language: MPI and C Computer: Any which supports MPI I/O Operating system: Any Has the code been vectorised or parallelised?: Yes. Includes MPI directives. RAM: Depending on input used Classification: 11.5 External routines: MPI Nature of problem: Distributed file I/O with metadata Solution method: MPI parallel I/O based implementation of LIME format Running time: Varies depending on file and architecture size, in the order of seconds (C) 2012 Elsevier B.V. All rights reserved.

Performance of PHMC and HMC algorithms in n f = 4 LQCD with twisted Wilson quarks

We discuss the computation of the kaon and D meson masses in the N_f = 2+1+1 twisted mass lattice QCD setup, where explicit heavy flavor and parity breaking occurs at finite lattice spacing. We present three methods suitable in this context and verify their consistency.

Renormalization constants of quark bilinears in lattice QCD with four dynamical Wilson quarks

7 pages, 9 figures, Talk presented at The XXVI International Symposium on Lattice Field Theory, LATTICE 2008, July 14 - 19, 2008, Williamsburg, Virginia, USA