We gratefully acknowledge support from
the Simons Foundation
and member institutions

High Energy Physics - Lattice

New submissions

[ total of 7 entries: 1-7 ]
[ showing up to 2000 entries per page: fewer | more ]

New submissions for Thu, 23 Nov 17

[1]  arXiv:1711.08085 [pdf, ps, other]
Title: $B_s \to K \ellν$ form factors with 2+1 flavors
Authors: Fermilab Lattice, MILC Collaborations: Yuzhi Liu (1), Jon A. Bailey (2), A. Bazavov (3), C. Bernard (4), C.M. Bouchard (5), C. DeTar (6), Daping Du (7), A.X. El-Khadra (8,9), E.D. Freeland (10), E. Gámiz (11), Z. Gelzer (8,12), Steven Gottlieb (1), U.M. Heller (13), A.S. Kronfeld (9,14), J. Laiho (7), P.B. Mackenzie (9), Y. Meurice (12), E.T. Neil (15,16), J.N. Simone (9), R. Sugar (17), D. Toussaint (18), R.S. Van de Water (9), Ran Zhou (9) ((1) Indiana University, (2) Seoul National University, (3) Michigan State University, (4) Washington University, (5) University of Glasgow, (6) University of Utah, (7) Syracuse University, (8) University of Illinois, (9) Fermilab, (10) School of the Art Institute of Chicago, (11) Universidad de Granada, (12) University of Iowa, (13) American Physical Society, (14) Technische Universität München, (15) University of Colorado, (16) Brookhaven National Laboratory, (17) University of California, Santa Barbara, (18) University of Arizona)
Comments: 8 pages, 6 figures, to appear in the Proceedings of Lattice 2017, June 18-24, Granada, Spain
Subjects: High Energy Physics - Lattice (hep-lat)

Using the MILC 2+1 flavor asqtad quark action ensembles, we are calculating the form factors $f_0$ and $f_+$ for the semileptonic $B_s \rightarrow K \ell\nu$ decay. A total of six ensembles with lattice spacing from $\approx0.12$ to 0.06 fm are being used. At the coarsest and finest lattice spacings, the light quark mass $m'_l$ is one-tenth the strange quark mass $m'_s$. At the intermediate lattice spacing, the ratio $m'_l/m'_s$ ranges from 0.05 to 0.2. The valence $b$ quark is treated using the Sheikholeslami-Wohlert Wilson-clover action with the Fermilab interpretation. The other valence quarks use the asqtad action. When combined with (future) measurements from the LHCb and Belle II experiments, these calculations will provide an alternate determination of the CKM matrix element $|V_{ub}|$.

[2]  arXiv:1711.08121 [pdf, other]
Title: Calculation of fermionic Green functions with Grassmann higher-order tensor renormalization group
Subjects: High Energy Physics - Lattice (hep-lat)

We develop calculational method for fermionic Green functions in the framework of Grassmann higher-order tensor renormalization group. The validity of the method is tested by applying it to three-dimensional free Wilson fermion system. We compare the numerical results for chiral condensate and two-point correlation functions with the exact ones obtained by analytical methods.

Cross-lists for Thu, 23 Nov 17

[3]  arXiv:1711.07858 (cross-list from hep-ph) [pdf, other]
Title: Gaussian-weighted Parton Quasi-distribution
Comments: 9 pages, 3 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Lattice (hep-lat)

We propose a revised definition of quasi-distributions within the framework of large-momentum effective theory (LaMET) that improves convergence towards the large-momentum limit. Since the definition of quasi-distributions is not unique, each choice goes along with a specific matching function, we can use this freedom to optimize convergence towards the large-momentum limit. As an illustration, we study quasi-distributions with a Gaussian weighting factor that naturally suppresses long-range correlations, which are plagued by artifacts. This choice has the advantage that the matching functions can be trivially obtained from the known ones. We apply the Gaussian weighting to the previously published results for the nonperturbatively renormalized unpolarized quark distribution, and find that the unphysical oscillatory behavior is significantly reduced.

[4]  arXiv:1711.08062 (cross-list from cond-mat.mes-hall) [pdf, other]
Title: Coupling magneto-elastic Lagrangians to spin transfer torque sources
Comments: 6 pages, LaTeX2e, 3 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); High Energy Physics - Lattice (hep-lat)

The consequences of coupling magnetic and elastic degrees of freedom, where spins and deformations are carried by point-like objects subject to local interactions, are studied, theoretically and by detailed numerical simulations. From the constrained Lagrangians we derive consistent equations of motion for the coupled dynamical variables. In order to probe the dynamics of such a system, we consider external perturbations, such as spin transfer torques for the magnetic part, and homogeneous stresses for the elastic part, associated to their corresponding damping. This approach is applied to the study of ultrafast switching processes in anti-ferromagnetic systems, which have recently attracted attention as candidates for anti-ferromagnetic spintronic devices. Our strategy is then checked in simple, but instructive, situations. We carried out numerical experiments to study, in particular, how the magnetostrictive coupling and external stresses affect the nature of the switching processes in a prototype anti-ferromagnetic material.

[5]  arXiv:1711.08088 (cross-list from hep-ph) [pdf, ps, other]
Title: Hadron tomography by generalized distribution amplitudes in pion-pair production process $γ^* γ\rightarrow π^0 π^0 $ and gravitational form factors for pion
Comments: 26 pages, 21 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); High Energy Physics - Lattice (hep-lat); Nuclear Theory (nucl-th)

Hadron tomography can be investigated by three-dimensional structure functions such as generalized parton distributions (GPDs), transverse-momentum-dependent parton distributions, and generalized distribution amplitudes (GDAs). Here, we extract the GDAs, which are $s$-$t$ crossed quantities of the GPDs, from cross-section measurements of hadron-pair production process $\gamma^* \gamma \rightarrow \pi^0 \pi^0$ at KEKB. This work is the first attempt to obtain the GDAs from the actual experimental data. The GDAs are expressed by a number of parameters and they are determined from the data of $\gamma^* \gamma \rightarrow \pi^0 \pi^0$ by including intermediate scalar- and tensor-meson contributions to the cross section. Our results indicate that the dependence of parton-momentum fraction $z$ in the GDAs is close to the asymptotic one. The timelike gravitational form factors $\Theta_1$ and $\Theta_2$ are obtained from our GDAs, and they are converted to the spacelike ones by the dispersion relation. From the spacelike $\Theta_1$ and $\Theta_2$, gravitational densities of the pion are calculated. Then, we obtained the mass (energy) radius and the mechanical (pressure and shear force) radius from $\Theta_2$ and $\Theta_1$, respectively. They are calculated as $\sqrt {\langle r^2 \rangle_{\text{mass}}} =0.56 \sim 0.69$ fm, whereas the mechanical radius is larger $\sqrt {\langle r^2 \rangle_{\text{mech}}} =1.45 \sim 1.56$ fm. This is the first report on the gravitational radius of a hadron from actual experimental measurements. It is interesting to find the possibility that the gravitational mass and mechanical radii could be different from the experimental charge radius $\sqrt {\langle r^2 \rangle_{\text{charge}}} =0.672 \pm 0.008$ fm for the charged pion. There is a byproduct from our analysis that $f_0 (980)$ is not likely to be a $q\bar q$-type meson in comparison with the KEKB data.

Replacements for Thu, 23 Nov 17

[6]  arXiv:1708.01216 (replaced) [pdf, ps, other]
Title: Improved thermodynamics of SU(2) gauge theory
Comments: 32 pages, 22 figures. Source files of 20 figures (format agr of the program xmgrace) included in the submission as "ancillary files" from which raw data can be extracted. In this third version we removed 4 figures and we modified substantially Secs. 2.2, 3.3 and 4
Subjects: High Energy Physics - Lattice (hep-lat)
[7]  arXiv:1710.08066 (replaced) [pdf, ps, other]
Title: Comparison of different source calculations in two-nucleon channel at large quark mass
Comments: 8 pages, 7 figures, Proceedings of the 35th International Symposium on Lattice Field Theory (Lattice 2017), June 19-24, 2017, Granada, Spain
Subjects: High Energy Physics - Lattice (hep-lat)
[ total of 7 entries: 1-7 ]
[ showing up to 2000 entries per page: fewer | more ]

Disable MathJax (What is MathJax?)