Axial charges of hyperons and charmed baryons using Nf=2+1+1N_f=2+1+1 twisted mass fermions

The axial couplings of the low lying baryons are evaluated using a total of five ensembles of dynamical twisted mass fermion gauge configurations. The simulations are performed using the Iwasaki gauge action and two degenerate flavors of light quarks, and a strange and a charm quark fixed to approximately their physical values at two values of the coupling constant. The lattice spacings, determined using the nucleon mass, are $a=0.082$ fm and $a=0.065$ fm and the simulations cover a pion mass in the range of about 210 MeV to 430 MeV. We study the dependence of the axial couplings on the pion mass in the range of about 210 MeV to 430 MeV as well as the $SU(3)$ breaking effects as we decrease the light quark mass towards its physical value.Comment: 34 pages, 17 figure

Heavy-light baryonic mass splittings from the lattice

We present lattice estimates of the mass of the heavy-light baryons $\Lambda_b$ and $\Xi_b$ obtained using propagating heavy quarks. For $\Lambda_b$ our result is $M_{\Lambda_b}=5.728 \pm 0.144 \pm 0.018$ GeV, after extrapolation to the continuum limit and in the quenched approximation.Comment: 3 pages postscript, Contribution to Lattice'9

Evidence for diquarks in lattice QCD

Diquarks may play an important role in hadron spectroscopy, baryon decays and color superconductivity. We investigate the existence of diquark correlations in lattice QCD by considering systematically all the lowest energy diquark channels in a color gauge-invariant setup. We measure mass differences between the various channels and show that the positive parity scalar diquark is the lightest. Quark-quark correlations inside the diquark are clearly seen in this channel, and yield a diquark size of order 1 fm.Comment: Version as published in Phys. Rev. Lett.97, 222002,2006; 4 pages, 5 figure

Sigma-terms and axial charges for hyperons and charmed baryons

We present results for the $\sigma$-terms and axial charges for various hyperons and charmed baryons using $N_f=2+1+1$ twisted mass fermions. For the computation of the three-point function we use the fixed current method. For one of the $N_f=2+1+1$ ensembles with pion mass of 373 MeV we compare the results of the fixed current method with those obtained with a stochastic method for computing the all-to-all propagator involved in the evaluation of the three point functions.Comment: Talk presented at 31st International Symposium on Lattice Field Theory LATTICE 2013, July 29 - August 3, 2013, Mainz, Germany, PoS(LATTICE 2013)279. 7 pages and6 figure

Calculation of fermion loops for η′\eta^\prime and nucleon scalar and electromagnetic form factors

The exact evaluation of the disconnected diagram contributions to the flavor-singlet pseudoscalar meson mass, the nucleon sigma term and the nucleon electromagnetic form factors, is carried out utilizing GPGPU technology with the NVIDIA CUDA platform. The disconnected loops are also computed using stochastic methods with several noise reduction techniques. Various dilution schemes as well as the truncated solver method are studied. We make a comparison of these stochastic techniques to the exact results and show that the number of noise vectors depends on the operator insertion in the fermionic loop.Comment: Version accepted for publication in Comp. Phys. Commun. References added. 13 pages, 12 figure

Scaling Study of the Leptonic Decay Constants of Heavy-Light Mesons: A Consumers Report on Improvement Factors

A high statistics calculation, performed at $\beta =5.74,\;6.00$ and $6.26$, enables us to study the variation of the leptonic decay constants $f_P$ of heavy pseudoscalar mesons with the lattice spacing $a$. We observe only a weak $a$ dependence when the standard $\sqrt{2\kappa}$ normalization is used for the quark fields, whereas application of the Kronfeld-Mackenzie normalization induces a stronger variation with $a$. Increasing the meson mass from $1.1GeV$ to $2.3GeV$ this situation becomes even more pronounced.Comment: Lattice 93, 3 pages Latex, 2 postscript figures (epsf style

Using personas to promote inclusive education in an online course

Inclusion and diversity are themes at the forefront of education development and the subject of much institutional level policy. However, there are differences that can be made at the course or even module level by local teams that will both compliment institutional policy and have an immediate impact on students. This paper aims to describe the process taken to embed diversity and inclusion into an online career development short course. We will explain how user experience personas, created in the design phase of the course, developed into an integral part of the course curriculum and how they are used to show diversity to a fully asynchronous online cohort. We discuss how theories of pedagogy and design can be combined to have a positive impact on the sense of belong for all students. Finally, we explore how these theories can be applied to wider practice and offer suggestions for how other courses can use our process to embed elements of diversity into their programmes, and hopefully increase a sense of student belonging

Beautiful Baryons from Lattice QCD

We perform a lattice study of heavy baryons, containing one ($\Lambda_b$) or two $b$-quarks ($\Xi_b$). Using the quenched approximation we obtain for the mass of $\Lambda_b$ $$M_{\Lambda_b}= 5.728 \pm 0.144 \pm 0.018 {\rm GeV}.$$ The mass splitting between the $\Lambda_b$ and the B-meson is found to increase by about 20\% if the light quark mass is varied from the chiral limit to the strange quark mass.Comment: 11 pages, Figures obtained upon request from [email protected]

Semileptonic Decays of Heavy Mesons: A Status Report

We present intermediate results on our ongoing investigation concerning semileptonic decays of heavy pseudoscalar mesons into pseudoscalar and vector mesons. The corresponding formfactors are evaluated at several momenta and appropriate combinations of four light and four heavy quarks, which are chosen to allow for an extrapolation into the B Meson region. In order to obtain clear groundstate signals we apply gauge invariant ``Wuppertal'' smearing to the quarks. The analysis is based on 32 quenched gauge configurations of size $24^3 \times 64$ at $\beta=6.3$, with Wilson fermions.Comment: 3 pages, uuencoded, contribution to Lat 9