Static hybrid quarkonium potential with improved staggered quarks Page: 1 of 3
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FERMILAB-Conf-02/399-T January 2004
Static hybrid quarkonium potential with improved staggered quarks
MILC Collaboration: C. Bernard a, T. Burch b, C.E. DeTar ', Ziwen FuC*, Steven Gottlieb d,
E. Gregory b, U.M. Heller e, J. OsbornC, R.L. Sugar f, and D. Toussaint b
'Department of Physics, Washington University, St. Louis, MO 63130, USA
bDepartment of Physics, University of Arizona, Tucson, AZ 85721, USA
CPhysics Department, University of Utah, Salt Lake City, UT 84112, USA
dDepartment of Physics, Indiana University, Bloomington, IN 47405, USA and Fermilab, Batavia, IL
eCSIT, Florida State University, Tallahassee, FL 32306-4120, USA
fDepartment of Physics, University of California, Santa Barbara, CA 93106, USA
We are studying the effects of light dynamical quarks on the excitation energies of a flux tube between a static
quark and antiquark. We report preliminary results of an analysis of the ground state potential and the E'
and [U potentials. We have measured these potentials on closely matched ensembles of gauge configurations,
generated in the quenched approximation and with 2+1 flavors of Asqtad improved staggered quarks.
Simulations with dynamical quarks have found
that light quarks modify the heavy quark-
antiquark potential in a number of ways [1-3].
At large distances they decrease the string ten-
sion in units of the Sommer ro and r1 parame-
ters (defined by r2F(r) = 1.65 and 1.00, respec-
tively) and lead eventually to string-breaking. At
shorter distances they modify the running of the
coupling constant, deepening the Coulomb well
and increasing the ratio ro/ri. In this work, we
extend these studies to some of the potentials
with excited flux tubes. Of particular interest to
quarkonium spectroscopy are the Hu excitations
leading to exotic QQg hybrids .
We report results of a study in which our
sources and sinks are optimized to create and an-
nihilate a flux-tube state. In the presence of dy-
namical quarks, string breaking is expected. It is
known that in the conventional E9 channel, tran-
sitions to the open two-meson channel are exceed-
ingly weak, qualitatively consistent with the small
widths of quarkonium states above the heavy-
light meson thresholds [5,3]. Since at present we
do not include the open two-meson channel we do
not expect to observe string breaking here.
We have measured the heavy quark potential
on an ensemble of 283 x 96 (a , 0.09 fm) gauge
configurations generated in the presence of 2 + 1
flavors of Asqtad dynamical quarks of varying
masses and a one-loop Symanzik gauge action.
The strange quark mass is set approximately to
its physical value. Here we compare results from
our 358-configuration quenched ensemble with
our 495-configuration dynamical quark ensemble
for which (m,ro)2 ~. 1.3.
The configurations are first smoothed using a
single hypercubic (HYP) blocking pass , a tech-
nique that improves significantly the signal-to-
noise ratio . The blocking procedure involves
replacing all gauge links (timelike as well as space-
like) with an SU(3)-projected average over paths
confined to adjacent hypercubes. Thus distor-
tions in the result are local and expected to be
*Presented by Ziwen Fu
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al., C. Bernard et. Static hybrid quarkonium potential with improved staggered quarks, article, January 6, 2004; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc735048/m1/1/: accessed November 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.