Nuclear Physics from Lattice QCD Page: 4 of 12
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with exciting discoveries of charmonium states, considerable progress has been made in
studying bottom mesons and baryons. While the B factories, such as Belle and Babar, have
investigated the bottom mesons, recent experiments at Fermilab have reported the discover-
ies of a few bottom baryon states. It is anticipated that in the upcoming dedicated bottom
physics experiment LHCb at CERN, there will be many more discoveries in the bottom-
hadron spectrum, significantly enhancing our knowledge about these states. Most recently
DO and CDF have observed ; , however their results seem to be in disagreement. Lattice
determinations of the flavored baryon spectrum could be useful and complementary to the
on going experimental program in this field.
During this last year we targeted both the charm and the bottom sector with two different
computational approaches. In the bottom sector we worked with the static approximation
since the bottom quark is heavy and the leading term in the Heavy Quark Effective The-
ory (HQET) is sufficient reliable computations of several quantities. In the charm sector (a
project primarily pushed by my graduate student Liuming Liu) we used the Fermilab rel-
ativistic action in order to reduce discretization errors and capture the relevant relativistic
effects in the charm sector.
Our results in the bottom sector are in good agreement with experiment. In the case of Qb
our result is in good agreement with the CDF result and several standard deviations away
from the DO observation. In addition, we also predict the mass for the as yet unobserved 'E
to be 5955(27) MeV.
In the charmed sector, we have published in conference proceedings preliminary results for
the baryon (spin 1/2) sector. In addition, we compute the scattering lengths of charmed
mesons and charmonia scattering with light hadrons. The scattering processes of chamonia
(r/c and J/1[) with light hadrons (r, p and N). As it has been pointed out in the literature such
interaction has a direct relation to possible charmonium-nucleus bound states with binding
energy of a few MeV. Unlike the traditional nuclear force that binds nucleons, in this case,
there are no quark exchange diagrams, and only gluons are responsible for the binding. In
other words, the charmonium nucleon force is purely a gluonic van der Waals force. D
meson scattering can also provide useful insight to nucleon nucleon interactions since the
low energy effective theory describing the D meson interaction through the exchange of
pions is related to this of the nucleon-nucleon interaction. These calculations are pursued
for the first time in the full QCD.
Currently we are working on finalizing a publication of our results for both the spectroscopy
and scattering lengths in the charmed sector. During the next year we plan to extend these
calculations to the cases where coupled channels exist and study the formalism needed to
extract scattering lengths in such cases (where the application of the simple Luscher formula
is not possible).
" Meson Baryon interactions: The 7r++, 7+ , K+p, K+n, and KOWO scattering lengths
are calculated in mixed-action Lattice QCD with domain-wall valence quarks on the asqtad-
improved coarse MILC configurations at four light-quark masses, and at two light-quark
masses on the fine MILC configurations. Heavy Baryon Chiral Perturbation Theory with
two and three flavors of light quarks is used to perform the chiral extrapolations. We find no
convergence for the kaon-baryon processes in the three-flavor chiral expansion. Using the
two-flavor chiral expansion, we find a,+z+ =?0.197 + 0.017 fm, and a,+o =?0.0980.017
fm, where the comprehensive error includes statistical and systematic uncertainties.4
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Orginos, Konstantinos. Nuclear Physics from Lattice QCD, report, April 19, 2013; United States. (https://digital.library.unt.edu/ark:/67531/metadc830144/m1/4/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.