15 research outputs found
Hadron Distribution Amplitudes from Lattice QCD Simulations
In this thesis we examine hadron distribution amplitudes, which are universal, process-independent functions that govern the physics of hard exclusive processes and contribute to both, measurements of fundamental parameters of the Standard Model and probes of new physics. For this purpose, we perform lattice QCD simulations for mesons and baryons in order to calculate Mellin moments of the distribution amplitudes numerically
Pion and Kaon Distribution Amplitudes from lattice QCD: towards the continuum limit
We present the current status of a non-perturbative lattice calculation of
the moments of the pion and kaon distribution amplitudes by the RQCD
collaboration. Our investigation is carried out using dynamical,
non-perturbatively O(a)-improved Wilson fermions on the CLS ensembles with 5
different lattice spacings and pion masses down to the physical pion mass. A
combined continuum and chiral extrapolation to the physical point is performed
along two independent quark mass trajectories simultaneously. We employ
momentum smearing in order to decrease the contamination by excited states and
increase statistical precision.Comment: Proceedings of the 36th Annual International Symposium on Lattice
Field Theory - LATTICE201
Light-cone distribution amplitudes of the baryon octet
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 flavors of dynamical (clover) fermions on lattices of
different volumes and pion masses down to 222 MeV. Significant SU(3) flavor
symmetry violation effects in the shape of the distribution amplitudes are
observed.Comment: Update to the version published in JHE
Light-cone distribution amplitudes of octet baryons from lattice QCD
We present lattice QCD results for the wave function normalization constants
and the first moments of the distribution amplitudes for the lowest-lying
baryon octet. The analysis is based on a large number of ensembles
comprising multiple trajectories in the quark mass plane including physical
pion (and kaon) masses, large volumes, and, most importantly, five different
lattice spacings down to . This allows us to perform a
controlled extrapolation to the continuum and infinite volume limits by a
simultaneous fit to all available data. We demonstrate that the formerly
observed violation of flavor symmetry breaking constraints can, indeed, be
attributed to discretization effects that vanish in the continuum limit
Pion distribution amplitude from Euclidean correlation functions: Exploring universality and higher-twist effects
Building upon our recent study [G. S. Bali et al., Eur. Phys. J. C 78, 217 (2018)], we investigate the feasibility of calculating the pion distribution amplitude from suitably chosen Euclidean correlation functions at large momentum. We demonstrate in this work the advantage of analyzing several correlation functions simultaneously and extracting the pion distribution amplitude from a global fit. This approach also allows us to study higher-twist corrections, which are a major source of systematic error. Our result for the higher-twist parameter delta(pi)(2) is in good agreement with estimates from QCD sum rules. Another novel element is the use of all-to-all propagators, calculated using stochastic estimators, which enables an additional volume average of the correlation functions, thereby reducing statistical errors
Addendum to: Light-cone distribution amplitudes of pseudoscalar mesons from lattice QCD
We update our lattice determination of the two lowest Gegenbauer moments
of the leading-twist pion and kaon light-cone distribution amplitudes [1] using the recently
calculated three-loop matching factors for the conversion from the RI0/SMOM to the MS
scheme [2, 3]. We find a�2 = 0.116+19
−20 for the pion, aK1
= 0.0525+31
−33 and aK2
= 0.106+15
−16 for
the kaon. Updated plots can be found in the appendix in the arXiv submission
Light-cone distribution amplitudes of pseudoscalar mesons from lattice QCD
We present the first lattice determination of the two lowest Gegenbauer moments of the leading-twist pion and kaon light-cone distribution amplitudes with full control of all errors: for the pion; and for the kaon. The calculation is carried out on 35 different CLS ensembles with flavors of dynamical Wilson-clover fermions. These cover a multitude of pion and kaon mass combinations (including the physical point) and 5 different lattice spacings down to fm. The momentum smearing technique and a new operator basis are employed to reduce statistical fluctuations and to improve the overlap with the ground states. The results are obtained from a combined chiral and continuum limit extrapolation that includes three separate trajectories in the quark mass plane
Pion distribution amplitude from Euclidean correlation functions
Abstract Following the proposal in (Braun and Müller. Eur Phys J C55:349, 2008), we study the feasibility to calculate the pion distribution amplitude (DA) from suitably chosen Euclidean correlation functions at large momentum. In our lattice study we employ the novel momentum smearing technique (Bali et al. Phys Rev D93:094515, 2016; Bali et al. Phys Lett B774:91, 2017). This approach is complementary to the calculations of the lowest moments of the DA using the Wilson operator product expansion and avoids mixing with lower dimensional local operators on the lattice. The theoretical status of this method is similar to that of quasi-distributions (Ji. Phys Rev Lett 110:262002, 2013) that have recently been used in (Zhang et al. Phys Rev D95:094514, 2017) to estimate the twist two pion DA. The similarities and differences between these two techniques are highlighted
The rho-meson light-cone distribution amplitudes from lattice QCD
We present the results of a lattice study of the normalization constants and
second moments of the light-cone distribution amplitudes of longitudinally and
transversely polarized mesons. The calculation is performed using two
flavors of dynamical clover fermions at lattice spacings between
and , different lattice volumes up to
and pion masses down to . Bare lattice
results are renormalized non-perturbatively using a variant of the RI'-MOM
scheme and converted to the scheme. The necessary
conversion coefficients, which are not available in the literature, are
calculated. The chiral extrapolation for the relevant decay constants is worked
out in detail. We obtain for the ratio of the tensor and vector coupling
constants and the values of the
second Gegenbauer moments and at the scale for the longitudinally and
transversely polarized mesons, respectively. The errors include the
statistical uncertainty and estimates of the systematics arising from
renormalization. Discretization errors cannot be estimated reliably and are not
included. In this calculation the possibility of decay at the
smaller pion masses is not taken into account.Comment: Updated to published versio