1,096 research outputs found
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 on a 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, .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
and obtained using propagating heavy quarks. For
our result is 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 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 , and at
. 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
- …