The nucleon to Delta electromagnetic transition form factors in lattice QCD

The electromagnetic nucleon to Delta transition form factors are evaluated using two degenerate flavors of dynamical Wilson fermions and using dynamical sea staggered fermions with domain wall valence quarks. The two subdominant quadrupole form factors are evaluated for the first time in full QCD to sufficient accuracy to exclude a zero value, which is taken as a signal for deformation in the nucleon-Delta system. For the Coulomb quadrupole form factor the unquenched results show deviations from the quenched results at low q^2 bringing dynamical lattice results closer to experiment, thereby confirming the importance of pion cloud contributions on this quantity.Comment: 15 pages, 8 Figure

Hadron wave functions and the issue of nucleon deformation

Using gauge invariant hadronic two- and three- density correlators we extract information on the spatial distributions of quarks in hadrons, and on hadron shape and multipole moments within quenched lattice QCD. Combined with the calculation of N to Delta transition amplitudes the issue of nucleon deformation can be addressed.Comment: 4 pages, 7 figures. Talk presented at the PANIC02 conference, Sept. 30 - Oct. 4, 2002, Osaka, Japan. Discussion of the N to Delta results modifie

Momentum dependence of the N to Delta transition form factors

We present a new method to determine the momentum dependence of the N to Delta transition form factors and demonstrate its effectiveness in the quenched theory at $\beta=6.0$ on a $32^3 \times 64$ lattice. We address a number of technical issues such as the optimal combination of matrix elements and the simultaneous overconstrained analysis of all lattice vector momenta contributing to a given momentum transfer squared, $Q^2$.Comment: Talk presented at Lattice 2004 (spectrum), Fermilab, 21-26 Jun. 2004. 3 pages, 3 figures. One typo in phenomenological Ansatz correcte

Union learning representatives: facilitating professional development for Scottish teachers

In the United Kingdom, teachers' professional associations and labor organizations, notably in the form of trade unions have historically been involved in education and training in the workplace. Recently, in the United Kingdom this activity has gained greater credence and importance due to the emergence of trade union learning representatives who are a new category of unpaid lay representation with statutory rights who operate within the workplace. They are part of the present UK government's drive to expand and improve lifelong learning and continuing professional development (CPD) in order to create the new learning society within the UK. In Scotland, a constituent part of the UK with its own distinctive education system, the McCrone Report (2000), particularly its CPD recommendations and the subsequent 21st Century Agreement (Scottish Executive Education Department [SEED], 2001) has added impetus to the role of these learning representatives within the Scottish teaching profession. This article examines how the Educational Institute of Scotland, a professional trade union, which represents the overwhelming majority of teachers in Scotland, has launched a learning representatives initiative with the aim that the representatives work to advise, broker, and facilitate improved CPD opportunities for their colleagues, particularly in relation to Chartered Teacher status (O'Brien and Hunt, 2005)

Axial Nucleon to Delta transition form factors on 2+1 flavor hybrid lattices

We correct the values of the dominant nucleon to Delta axial transition form factors CA_5 and CA_6 published in C. Alexandrou et.al., Phys. Rev. D 76,094511 (2007). The analysis error affects only the values obtained when using the hybrid action in the low Q^2 regime bringing them into agreement with those obtained with Wilson fermions.Comment: 1+2 pages, 2 figures, 1 Table, Erratum to C. Alexandrou et.al., Phys. Rev. D 76, 094511 (2007

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

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

A lattice study of the pentaquark states

We present a study of the pentaquark system in quenched lattice QCD using diquark-diquark and kaon-nucleon local and smeared interpolating fields. We examine the volume dependence of the spectral weights of local correlators on lattices of size $16^3\times 32$, $24^3\times32$ and $32^3\times 64$ at $\beta=6.0$. We find that a reliable evaluation of the volume dependence of the spectral weights requires accurate determination of the correlators at large time separations. Our main result from the spectral weight analysis in the pentaquark system is that within our variational basis and statistics we can not exclude a pentaquark resonance. However our data also do not allow a clear identification of a pentaquark state since only the spectral weights of the lowest state can be determined to sufficient accuracy to test for volume dependence. In the negative parity channel the mass extracted for this state is very close to the KN threshold whereas in the positive parity channel is about 60% above.Comment: Manuscript expanded, discussion of two-pion system included, a comment regarding Ref.13 was corrected, version to appear in Phys. Rev. D, 19 figure