Excited-state hadron masses using the stochastic LapH method

Bulava, John; Juge, Keisuke J.; Morningstar, Colin; Wong, Chik Him; Foley, Justin; Lenkner, David; Jhang, You-Cyuan

doi:10.22323/1.139.0131

Article
Report number	arXiv:1111.0845
Title	Excited-state hadron masses using the stochastic LapH method
Author(s)	Bulava, John (CERN) ; Foley, Justin (Utah U.) ; Jhang, You-Cyuan (Carnegie Mellon U.) ; Juge, Keisuke J. (U. Pacific, Stockton) ; Lenkner, David (Carnegie Mellon U.) ; Morningstar, Colin (Carnegie Mellon U.) ; Wong, Chik Him (UC, San Diego)
Publication	2011
Imprint	04 Nov 2011
Number of pages	8
Note	Comments: 8 pages, 4 figures, contribution to The XXIX International Symposium on Lattice Field Theory - Lattice 2011, July 10-16, 2011, Squaw Valley, Lake Tahoe, California, USA 8 pages, 4 figures, contribution to The XXIX International Symposium on Lattice Field Theory - Lattice 2011, July 10-16, 2011, Squaw Valley, Lake Tahoe, California, USA
In:	PoS LATTICE2011 (2011) 31
In:	29th International Symposium on Lattice Field Theory, Squaw Valley, Lake Tahoe, CA, USA, 10 - 16 Jul 2011, pp.131
DOI	10.22323/1.139.0131
Subject category	Particle Physics - Lattice
Abstract	Progress in computing the spectrum of excited baryons and mesons in lattice QCD is described. Large sets of spatially-extended hadron operators are used. The need for multi-hadron operators in addition to single-hadron operators is emphasized, necessitating the use of a new stochastic method of treating the low-lying modes of quark propagation which exploits Laplacian Heaviside quark-field smearing. A new glueball operator is tested and computing the mixing of this glueball operator with a quark-antiquark operator and multiple two-pion operators is shown to be feasible. Some of our initial results show warning signs about extracting high-lying resonance energies using only single-hadron operators.

$Masses of the isovector mesons in terms of the nucleon mass using the stochastic LapH method with 170 gauge configurations on a $24^3\times 128$ anisotropic lattice. The pion mass is about $m_\pi\sim 390$~MeV. In the irrep labels, the letters with numerical subscripts refer to the point group $O_h$ irreps, the subscripts $g$ and $u$ refer to even and odd parity, respectively, and the superscripts $\pm$ refer to $G$-parity. Only single-hadron operators were used with dilution scheme $(TF,SF,LI8)$. The shaded region indicates the threshold locations for multi-hadron energy levels. We emphasize that extractions of energies in the shaded regions could be complicated by ``false plateaux'' unless multi-hadron operators are used.$ $Effective masses corresponding to the diagonal elements of the rotated $2\times 2$ correlator matrix involving a single-site $\rho$-meson operator and an $I=1$ $\pi\pi$ operator in a $P$-wave with minimal relative momentum. The $\rho$ operator dominates the lowest-lying level (left), while the $\pi\pi$ operator dominates the first-excited state (right). Although the mixing of the operators is small, it is not negligible. These results were obtained on 584 configurations of the $24^3\times 128$ lattice with pion mass $m_\pi\sim 240$~MeV.$ $Comparison of the effective mass associated with the correlator of the standard smeared plaquette glueball operator (left) with that of our new glueball operator $G_\Delta$ defined in the text (right). The similarity of the two results shows that the new glueball operator is just as useful as the familiar smeared plaquette for studying the scalar glueball. These effective masses do not reach a plateau at the glueball mass since various $\pi\pi$ states and other multi-hadron states have smaller energies than the glueball mass. These results were obtained using 584 configs of the $24^3$ ensemble for pion mass $m_\pi\sim 240$~MeV.$ Show more plots

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Record created 2011-11-04, last modified 2023-03-14

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