290 research outputs found
The Determination of the Quark-Gluon Mixed Condensate (anti-Q sigma G Q) from Lattice QCD
We study the quark-gluon mixed condensate g, using the
SU(3)c lattice QCD with the Kogut-Susskind fermion at the quenched level. We
generate 100 gauge configurations on the 16^4 lattice with \beta = 6.0, and
perform the measurement of the mixed condensate at 16 points in each gauge
configuration for each current quark mass of m_q=21, 36, 52 MeV. Using the 1600
data for each m_q, we find the ratio between the mixed condensate and the quark
condensate, m_0^2 = g / \simeq 2.5 GeV^2 at the
lattice scale of 1/a \simeq 2 GeV in the chiral limit. The large value of the
mixed condensate suggests its importance in the operator product expansions in
QCD. We study also chiral restoration at finite temperature in terms of the
mixed condensate, which is another chiral order parameter. We present the
lattice QCD results of the mixed condensate at finite temperature.Comment: 5 pages, Talk given at Tokyo-Adelaide Joint Workshop on Quarks,
Astrophysics and Space physics, Tokyo, Japan, Jan.6 - Jan.10, 200
Comment on "Relation between scattering amplitude and Bethe-Salpeter wave function in quantum field theory"
We invalidate the arguments given in [T.Yamazaki and Y.Kuramashi, Phys. Rev.
D96, 114511 (2017)] over the HAL QCD method for hadron-hadron interactions on
the lattice. We also pose questions on the practical usefulness of the method
proposed in this reference.Comment: 3 pages. Version accepted for publication in Physical Review
Are two nucleons bound in lattice QCD for heavy quark masses? -- Consistency check with L\"uscher's finite volume formula --
On the basis of the L\"uscher's finite volume formula, a simple test
(consistency check or sanity check) is introduced and applied to inspect the
recent claims of the existence of the nucleon-nucleon () bound state(s) for
heavy quark masses in lattice QCD. We show that the consistency between the
scattering phase shifts at and/or obtained from the lattice
data and the behavior of phase shifts from the effective range expansion (ERE)
around exposes the validity of the original lattice data, otherwise
such information is hidden in the energy shift of the two nucleons
on the lattice. We carry out this sanity check for all the lattice results in
the literature claiming the existence of the bound state(s) for heavy
quark masses, and find that (i) some of the data show clear inconsistency
between the behavior of ERE at and that at , (ii) some of
the data exhibit singular behavior of the low energy parameter (such as
the divergent effective range) at , (iii) some of the data have the
unphysical residue for the bound state pole in S-matrix, and (iv) the rest of
the data are inconsistent among themselves. Furthermore, we raise a
caution of using the ERE in the case of the multiple bound states. Our finding,
together with the fake plateau problem previously pointed out by the present
authors, brings a serious doubt on the existence of the bound states for
pion masses heavier than 300 MeV in the previous studies.Comment: 39 pages, 16 figures, and 11 tables, title changed, references and
comment adde
Baryon interactions from lattice QCD with physical quark masses -- Nuclear forces and forces --
We present the latest lattice QCD results for baryon interactions obtained at
nearly physical quark masses. nonperturbatively -improved Wilson quark action with stout smearing and Iwasaki gauge
action are employed on the lattice of (96a)^4 \simeq (8.1\mbox{fm})^4 with
GeV, where MeV and MeV.
In this report, we study the two-nucleon systems and two- systems in
channel and - coupled channel, and extract central and
tensor interactions by the HAL QCD method. We also present the results for the
interaction in channel which is relevant to the
pair-momentum correlation in heavy-ion collision experiments.Comment: Talk given at 35th International Symposium on Lattice Field Theory
(Lattice 2017), Granada, Spain, 18-24 Jun 2017, 8 pages, 9 figures. arXiv
admin note: text overlap with arXiv:1702.0160
Most Strange Dibaryon from Lattice QCD
The system in the channel (the most strange dibaryon)
is studied on the basis of the (2+1)-flavor lattice QCD simulations with a
large volume (8.1 fm) and nearly physical pion mass MeV
at a lattice spacing fm. We show that lattice QCD data
analysis by the HAL QCD method leads to the scattering length , the effective range and the binding energy . These results indicate that the
system has an overall attraction and is located near the unitary regime. Such a
system can be best searched experimentally by the pair-momentum correlation in
relativistic heavy-ion collisions.Comment: 6 pages and 4 figure
dibaryon from lattice QCD near the physical point
The nucleon()-Omega() system in the S-wave and spin-2 channel
(S) is studied from the (2+1)-flavor lattice QCD with nearly physical
quark masses (~MeV and ~MeV). The
time-dependent HAL QCD method is employed to convert the lattice QCD data of
the two-baryon correlation function to the baryon-baryon potential and
eventually to the scattering observables. The (S) potential,
obtained under the assumption that its couplings to the D-wave octet-baryon
pairs are small, is found to be attractive in all distances and to produce a
quasi-bound state near unitarity: In this channel, the scattering length, the
effective range and the binding energy from QCD alone read ~fm, ~fm, ~MeV,
respectively. Including the extra Coulomb attraction, the binding energy of
(S) becomes ~MeV. Such a spin-2 state could be
searched through two-particle correlations in -, -nucleus and
nucleus-nucleus collisions.Comment: 16 pages, 6 figures, a reference adde
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