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Dr
Christian Wiese
(NIC - DESY Zeuthen)
25/07/2016, 14:15
Although parton distribution functions are the fundamental objects describing the inner structure of hadrons, they were so far not calculated from first principles.
In the past, lattice QCD has successfully been employed for the computation of hadronic spectra and form factors. Yet calculations of quark distributions are still missing, since they are given by light-cone correlation functions...
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Dr
YIBO Yang
(university of Kentucky)
25/07/2016, 14:35
I shall report on the progress of the proton spin decomposition based on Ji’s scheme and also the necessary perturbative calculation, to convert them from the lattice regularization to MS-bar scheme at 2 GeV.
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Michael Engelhardt
(New Mexico State University)
25/07/2016, 14:55
Quark orbital angular momentum (OAM) in the nucleon can be evaluated
directly by employing a Wigner function embodying the simultaneous
distribution of parton transverse position and momentum. This
distribution can be accessed via a generalization of the nucleon
matrix elements of quark bilocal operators which have been used
previously in the lattice evaluation of transverse...
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Prof.
Constantia Alexandrou
(University of Cyprus and The Cyprus Institute)
25/07/2016, 15:15
The quark contributions to the spin and mass of the nucleon are computed using $N_f=2$ twisted mass fermions with a physical value of the pion mass. We use improved methods to obtain accurate results for
the disconnected contributions involved in the evaluation of the axial charge and quark momentum fraction as well as the light, the strange and the charm $\sigma$-terms.
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Dr
James Zanotti
(University of Adelaide)
25/07/2016, 15:35
Fourier transforms of electromagnetic form factors provide valuable insights into the spatial distribution of quarks/charge within a hadron. When combined with form factors arising from non-forward matrix elements of the tensor operator, we are able to unlock fascinating information into the distribution of transversely polarised/unpolarised quarks within a transversely polarised/unpolarised...
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Sergey Syritsyn
(Jefferson Lab)
25/07/2016, 15:55
In typical nucleon structure calculations on a lattice, the interpolating fields are optimized to overlap with the nucleon ground state at rest, which in practice limits the momentum transfer in form factors to $Q^2\le 1\,GeV^2$. There is great interest in studying nucleon form factors up to few tens of GeV^2. New experiments at the JLab 12-GeV upgrade will measure nucleon form factors with...
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Andre Walker-Loud
(LBNL)
25/07/2016, 16:45
Motivated by the Feynman-Hellman Theorem, we develop an improved method for computing matrix elements of external currents utilizing only two-point correlation functions.
The contamination from excited states is shown to be Euclidean-time dependent allowing for a significantly improved ability to reliably determine and control the systematics.
We demonstrate the utility of our method with a...
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Mr
Alexander Chambers
(University of Adelaide)
25/07/2016, 17:05
Although hadron structure calculations in lattice QCD
have improved greatly in recent years,
many problems still remain.
Various techniques for determining fermion line disconnected contributions to
matrix elements have produced exciting and promising results, but
rely on complicated analyses.
Additionally, calculations of electromagnetic form factors at high
momentum transfers remain...
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Dr
Shigemi Ohta
(KEK)
25/07/2016, 17:25
Nucleon isovector vector- and axialvector-current form factors and some low moments of isovector structure functions will be reported with improved statistics from four recent RBC+UKQCD 2+1-flavor dynamical drain-wall fermions ensembles: Iwasaki gauge 24^3x64 at 1.78-GeV momentum cut off and pion mass of 432 ans 330 MeV and Iwasaki times DSDR gauge 32^3x64 at 1.38 GeV momentum cut off and pion...
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Prof.
Keh-Fei Liu
(University of Kentucky)
25/07/2016, 17:45
I shall report on calculations of isovector matrix elements of the nucleon, such as $g_A, g_s$, and $\langle x \rangle$ on the $48^3 \times 96$ lattice with pion mass at 139 MeV and lattice size of 5.5 fm. We employ overlap valence fermion on the 2+1 flavor DWF configurations for the calculation. Also reported will be the strange quark momentum fraction and its magnetic moment from this...
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Mr
Fabian Hutzler
(University Regensburg)
25/07/2016, 18:05
We present results of the first ab initio lattice QCD calculation of the normalization constants and first moments of the leading twist distribution amplitudes of the full baryon octet, corresponding to the small transverse distance limit of the associated S-wave light-cone wave functions. The P-wave (higher twist) normalization constants are evaluated as well. The calculation is done using...
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Mr
Michael Gruber
(RQCD collaboration)
25/07/2016, 18:25
Octet baryon distribution amplitudes are non-perturbative objects of phenomenological interest parametrizing the momentum distribution within the corresponding Fock states. Their normalization and their moments can be calculated using lattice QCD, and such results require renormalization. However, the MS-bar scheme, i.e., the renormalization scheme used in phenomenological applications,...
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Christoph Lehner
(BNL)
26/07/2016, 14:00
I present our recent results for the disconnected HVP contribution and report the current status of our light connected HVP contribution to the muon anomalous magnetic moment.
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Mr
Luchang Jin
(Columbia University)
26/07/2016, 14:20
We report our recent lattice calculation of hadronic light-by-light contribution to muon $g-2$ using our recent developed moment method. The connected diagrams and the leading disconnected diagrams are included. The calculation is performed on a $48^3 \times 96$ lattice with physical pion mass and 5.5 fm box size. We expect sizable finite volume and finite lattice spacing corrections to the...
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Hanno Horch
(University of Mainz)
26/07/2016, 14:40
We present results of our lattice QCD study of the hadronic vacuum polarization (HVP)
function with O$(a)$-improved $N_{\rm f}=2$ Wilson fermions with twisted boundary
conditions. We discuss the extraction of the leading order hadronic contribution to the
anomalous magnetic moment of the muon $\left(a_\mu^{\mathrm{HLO}}\right)$ via the
hybrid method involving two steps: (i) To describe...
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Mr
James Harrison
(University of Southampton)
26/07/2016, 15:00
Lattice calculations of the leading-order hadronic contribution to the muon g-2, from the hadronic vacuum polarisation, are approaching sub-percent level precision. At this level, it becomes important to consider corrections from isospin-breaking. Here, we include quenched QED in our simulations by stochastically generating U(1) gauge configurations and combining these with existing SU(3)...
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Ms
Vera Guelpers
(University of Southampton)
26/07/2016, 15:20
We present a strategy to calculate the leading order electromagnetic corrections to meson masses and the hadronic vacuum polarization. These corrections are computed directly through a QED perturbative expansion of the QCD+QED correlation functions. We will show some first results obtained using $N_f=2+1$ Domain Wall fermions. This calculation will be directly compared to the stochastic...
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Mr
Nils Asmussen
(Institut für Kernphysik, Johannes Gutenberg-Universität Mainz)
26/07/2016, 15:40
The anomalous magnetic moment of the muon currently shows a more than $3\sigma$ discrepancy between the experimental value and recent Standard Model predictions. The theoretical uncertainty is dominated by the hadronic vacuum polarization and the hadronic light-by-light (HLbL) scattering contributions, where the latter has so far only been fully evaluated using different models. To pave the...
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Dr
Taichi Kawanai
(Forschungszentrum Jülich (Budapest-Marseille-Wuppertal collaboration))
26/07/2016, 16:30
Recent phenomenological and lattice determinations of the anomalous magnetic moment of the muon $a_\mu$ hint at beyond the Standard Model physics on the 3-4 sigma level. Here we present lattice results for the leading order hadronic contribution of $a_\mu$ obtained from 2+1+1 flavor, staggered quark simulations at the physical point. The various quark flavor contributions, together with their...
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Dr
Kohtaroh Miura
(Centre de Physique Theorique, Aix-Marseille Universite, BMW Collaboration)
26/07/2016, 16:50
The low, euclidean momentum behavior of the hadron vacuum polarization (HVP) is critical for determining, amongst other quantities, the anomalous magnetic moments of the electron and the muon. Here we present lattice QCD results for the first few moments of the HVP obtained from 2+1+1 flavor, staggered-quark simulations at the physical point. The various quark-flavor contributions, together...
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Mr
Spraggs Matthew
(University of Southampton)
26/07/2016, 17:10
I present our work on the leading strange and charm quark-connected contributions to the muon anomalous magnetic moment using RBC/UKQCD physical point domain wall fermion ensembles.
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Dr
Tomomi Ishikawa
(RIKEN BNL Research Center)
26/07/2016, 17:30
In recent years, the quasi parton distribution has been introduced to extract the parton distribution functions by the lattice QCD simulation. The quasi and standard distribution share the same collinear IR singularity and the quasi distribution can be factorized into the standard distribution with perturbative matching factor. The quasi parton distribution is known to have power-law UV...
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Dr
Holger Perlt
(Institute for Theoretical Physics, University of Leipzig)
26/07/2016, 17:50
A partially conserved axial vector current that satisfies the chiral
Ward identity is defined nonperturbatively for improved Wilson
fermions. A first application to the nucleon axial vector coupling is
presented.
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Dr
Zohreh Davoudi
(MIT)
28/07/2016, 14:00
Nonuniform background electromagnetic fields, once implemented in lattice QCD calculations of hadronic systems, provide a means to constrain a large class of electromagnetic properties, from higher electromagnetic moments and charge radii to electromagnetic form factors. In this talk, I present the recent theoretical developments in realizing general background fields in periodic hypercubic...
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Dr
Laurent Lellouch
(CNRS & Aix-Marseille U.)
28/07/2016, 14:20
For the Budapest-Marseille-Wuppertal collaboration
We present a lattice study of the u, d and s quark contents of the nucleon, determined using the Feynman-Hellmann theorem. Results are obtained from twenty-nine high-statistics simulations with four flavors of O(a)-improved Wilson quarks, four lattice spacings and a variety of quark masses.
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Dr
Chia Cheng Chang
(LBNL)
28/07/2016, 14:40
Momentum-space derivatives of matrix elements can be related to their coordinate-space moments through the Fourier transform. We derive these expressions as a function of momentum transfer $Q^2$ for asymptotic in/out states consisting of a single hadron. We calculate corrections to the finite volume moments by studying the spatial dependence of the lattice correlation functions. This method...
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Dr
Yong-Chull Jang
(Los Alamos National Laboratory)
28/07/2016, 15:00
We present the status of the calculation of the nucleon iso-vector axial and vector form factor using the MILC $N_f=2+1+1$ HISQ ensembles with lattice spacings $a=0.12, 0.09$, and $0.06\;\mathrm{fm}$ and three values of light quark masses corresponding to pion masses $310, 220, 130\;\mathrm{MeV}$. Valence quarks are simulated with the clover action. A number of techniques to increase the...
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Nesreen Hasan
(Bergische Universitaet Wuppertal)
28/07/2016, 15:20
We describe a lattice approach for directly computing momentum derivatives
of nucleon matrix elements using the Rome method, which we apply
to obtain the isovector magnetic moment and Dirac radius. We present preliminary
results calculated at the physical pion mass using a 2HEX-smeared
Wilson-clover action from the Budapest-Marseille-Wuppertal collaboration.
For removing the effects of...
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Dr
Jeremy Green
(Institut für Kernphysik, Johannes Gutenberg-Universität Mainz)
28/07/2016, 15:40
A lattice QCD calculation of the light and strange axial form factors $G_A$ and $G_P$ of the nucleon will be reported. Disconnected diagrams were calculated using hierarchical probing, and a clear nonzero signal was obtained. We pay special attention to renormalization, which we determined nonperturbatively, including the mixing between light and strange quarks. This calculation was done on a...
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Prof.
Yoshinobu Kuramashi
(University of Tsukuba/RIKEN AICS)
28/07/2016, 16:30
We present preliminary results for nucleon form factors including the axial charge and the Dirac radius in 2+1 flavor QCD at the almost physical pion mass on a $96^4$ lattice with the lattice spacing of 0.084 fm. The configurations are generated with the stout-smeared $O(a)$-improved Wilson quark action and the Iwasaki gauge action at beta=1.82. A large spatial volume of (8.1fm$)^3$ allows us...
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Dr
Tim Harris
(Helmholtz-Institut Mainz)
28/07/2016, 16:50
We present updated results on the isovector electromagnetic form factors and axial coupling of the nucleon calculated using the CLS ensembles with $N_{\mathrm f}=2+1$ flavours of Wilson fermions. Systematic effects are investigated by covering a range of lattice spacings and pseudoscalar masses. Efficient variance reduction is achieved with the truncated solver method. The strategy to...
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Dr
Giannis Koutsou
(The Cyprus Institute)
28/07/2016, 17:10
The nucleon electromagentic and axial form factors are presented using an N$_\textrm{f}$=2 twisted mass fermion ensemble with pion mass of 135 MeV. Dipole masses for the momentum dependence of the form factors are extracted and compared to experiment, as is the nucleon magnetic moment and charge and magnetic radii.
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Dr
Alejandro Vaquero
(INFN Sezione Milano Bicocca)
28/07/2016, 17:30
The latest results from the Twisted-Mass collaboration on disconnected diagrams at the physical value of the pion mass are presented. In particular, we focus on the sigma terms, the axial charges and the momentum fraction. A detailed error analysis for each observable follows, showing the strengths and weaknesses of the one-end trick. Alternatives are discussed.
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Dr
Rajan Gupta
(Los Alamos National Laboratory)
28/07/2016, 17:50
High precision estimates of the iso-vector nucleon charges g_A, g_S and g_T, electric, magnetic and axial form factors measured on four ensembles of 2+1 flavor clover fermions will be presented and compared with those from clover-on-HISQ calculations. An analysis of systematic uncertainties due the lattice volume, lattice spacing, quark mass and renormalization will also be presented for both...
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Aaron Meyer
(University of Chicago/Fermilab)
28/07/2016, 18:10
The nucleon axial form factor is a dominant contribution to errors in neutrino oscillation studies. Lattice calculations have the potential to make an impact on controlling theory errors by disentangling the effects of nuclear corrections and nucleon form factors. In this talk, I will present preliminary results on a blinded calculation of $g_A$ and the axial form factor using HISQ staggered...
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Dr
Benoît Blossier
(CNRS/LPT Orsay)
29/07/2016, 14:00
In many lattice simulations with dynamical quarks, radial or orbital
excitations of hadrons lie near multihadron thresholds: it makes the
extraction of excited states properties more challenging and cqn introduce
some systematics difficult to estimate without an explicit computation of
correlators using interpolating fields strongly coupled to multihadronic
states. In a recent study...
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Dr
Maxwell Hansen
(University of Mainz)
29/07/2016, 14:20
Excited-state contamination is one of the dominant uncertainties in lattice calculations of nucleon charges and form factors. To estimate this uncertainty one needs the finite-volume energy spectrum as well as the finite-volume matrix elements that determine the coefficients of excited state exponentials. In this work we use experimental data, supplemented by chiral perturbation theory (ChPT),...
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Mr
Junpei Kakazu
(University of Tsukuba)
29/07/2016, 14:40
We present preliminary result of the electromagnetic form factor of the pion
at $m_\pi=0.145$ GeV on the large volume corresponding to $L = 8.1$ fm
using stout-smearing Wilson clover quark action and Iwasaki
gauge action at $a^{-1}=2.333$ GeV. The mean square charge radius
is estimated from the results at small space-like momentum transfer
with the NLO formula in SU(2) chiral perturbation...
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Mr
Bartosz Kostrzewa
(HISKP (Theory) - Universitaet Bonn)
29/07/2016, 15:00
We present an investigation of pion structure based on ETMC $N_f=2$ and $N_f=2+1+1$
twisted mass configurations at maximal twist. We compute
the first two moments of the quark momentum fraction of the pion and the electromagnetic form factor.
For the latter, momentum is injected using twisted boundary conditions and $F_\pi(Q^2)$ is calculated
at the physical pion mass. We find that our...
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Meinulf Goeckeler
(University of Regensburg)
29/07/2016, 15:20
We present preliminary results of the RQCD collaboration
for the lowest moments of the distribution amplitudes of the
rho meson obtained from simulations with 2 degenerate flavours
of clover fermions. The quark masses are chosen such that we
have rho masses below the decay threshold as well as above
threshold. Treating the rho as a stable particle, we find
results for small quark masses...
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Mr
Finn M. Stokes
(University of Adelaide)
29/07/2016, 15:40
Variational analysis techniques in lattice QCD are powerful tools that give access to the full spectrum of QCD. At zero momentum, these techniques are well established and can cleanly isolate energy eigenstates of either positive or negative parity.
In order to compute the form factors of a single energy eigenstate, we must perform a variational analysis at nonzero momentum. When we do this...
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Phiala Shanahan
(Massachusetts Institute of Technology)
29/07/2016, 16:30
We present the first lattice QCD study of the double-helicity-flip leading-twist gluonic structure function ∆(x,Q2). In particular, we calculate its leading moment in a φ meson and find a robust signal. This quantity is particularly interesting since, unlike the unpolarised and helicity gluon distributions, the double-helicity-flip density is a clean measure of gluonic degrees of freedom as it...
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Dr
Elena Luschevskaya
(State Scientific Center of Russian Federation - Institute of Theoretical and Experimental Physics)
29/07/2016, 16:50
We explore the ground state energy of pseudoscalar charged and neutral mesons as a function of external magnetic field in SU(3) lattice gauge theory. We calculate the dipole magnetic polarizabilities and hyperpolarizabilities of charged and neutral pseudoscalar pi and K mesons. It was found that the magnetic polarizability of charged pion agrees with the experimental prediction of COMPASS...
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Ms
Olga Soloveva
(Institute for Theoretical and Experimental Physics & National Research Nuclear University MEPhI (Moscow Engine ering Physics Institute))
29/07/2016, 17:10
We have explored ground state energies of the light vector mesons on the base of the $SU(3)$ lattice gauge theory. This study was performed without dynamical quarks. We have observed the energies spliting depending on the value of the spin projections on an external magnetic field. The ground state energy of neutral mesons with the $s_z = 0$ diminishes with the increase of the field, while the...
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Mr
Christian Zimmermann
(University of Regensburg)
29/07/2016, 17:30
The effects of double hard interactions are no longer negligible at energy scales reached at the LHC. Double parton scattering (DPS) processes are often described by taking the product of two single parton scattering processes assuming that interference effects are very small. We calculate four point functions (4pt-functions), which appear in the the DPS cross section, employing lattice...
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Dr
Luka Leskovec
(University of Arizona)
29/07/2016, 17:50
Lattice QCD calculations of radiative transitions between hadrons have in the past been limited to processes of hadrons stable under the strong interaction. Recently developed methods for $1 \to 2$ transition matrix elements in a finite volume now enable the determination of radiative decay rates of strongly unstable particles. Our lattice QCD study focuses on the process $\pi \pi \to \pi...
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Dr
Antoine Gerardin
(Institute for Nuclear Physics, University of Mainz)
29/07/2016, 18:10
We report on the lattice QCD calculation of the $\pi^0 \to \gamma^\ast \gamma^\ast$ form factor using two flavors of O(a)-improved Wilson fermions with photon virtualities in the range $Q^2 \in [0-1.5]$~GeV$^2$. Different lattice spacings and pion masses are used to extrapolate our result to the physical point.
First, we check that our results, once extrapolated to the chiral and continuum...
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