2,195 research outputs found
Properties of nucleon in nuclear matter: once more
We calculate the mass and residue of the nucleon in nuclear matter in the
framework of QCD sum rules using the nucleon's interpolating current with an
arbitrary mixing parameter. We evaluate the effects of the nuclear medium on
these quantities and compare the obtained results with the existing theoretical
predictions. The results are also compared with those obtained in vacuum to
find the shifts in the quantities under consideration. Our calculations show
that these shifts in the mass and residue are about and ,
respectively.Comment: 18 Pages, 2 Tables and 7 Figures, To be appear in EPJ
QCD nature of dark energy at finite temperature: cosmological implications
The Veneziano ghost field has been proposed as an alternative source of dark
energy whose energy density is consistent with the cosmological observations.
In this model, the energy density of QCD ghost field is expressed in terms of
QCD degrees of freedom at zero temperature. We extend this model to finite
temperature to search the model predictions from late time to early universe.
We depict the variations of QCD parameters entering the calculations, dark
energy density, equation of state, Hubble and deceleration parameters on
temperature from zero to a critical temperature. We compare our results with
the observations and theoretical predictions existing at different eras. It is
found that this model safely defines the universe from quark condensation up to
now and its predictions are not in tension with those of the standard
cosmology. The EoS parameter of dark energy is dynamical and evolves from
in the presence of radiation to at late time. The finite
temperature ghost dark energy predictions on the Hubble parameter well fit to
those of CDM and observations at late time.Comment: 10 Pages and 6 Figures. Some references were rearrange
Positive and negative parity hyperons in nuclear medium
The effects of nuclear medium on the residue, mass and self energy of the
positive and negative parity , and hyperons are
investigated using the QCD sum rule method. In the calculations, the general
interpolating currents of hyperons with an arbitrary mixing parameter are used.
We compare the results obtained in medium with those of the vacuum and
calculate the shifts in the corresponding parameters. It is found that the
shifts on the residues in nuclear matter are over all positive for both the
positive and negative parity hyperons, except for the positive parity
hyperon that the shift is negative. The shifts on the masses of these baryons
are obtained to be negative. The shifts on the residues and masses of negative
parity states are large compared to those of positive parities. The maximum
shift belongs to the residue of the negative parity hyperon. The
vector self-energies gained by the positive parity baryons are large compared
to the negative parities' vector self-energies. The maximum value of the vector
self-energy belongs to the positive parity hyperon. The numerical
values are compared with the existing predictions in the literature.Comment: 20 Pages, 9 Figures and 7 Table
More about the and mesons in nuclear matter
We calculate the shifts in decay constants of the pseudoscalar and
mesons in nuclear medium in the frame work of QCD sum rules. We write those
shifts in terms of the and scattering lengths and an extra
phenomenological parameter entered to calculations. Computing an appreciate
forward scattering correlation function, we derive the QCD sum rules for the
and scattering lengths and the extra phenomenological parameter in
terms of various operators in nuclear medium. We numerically find the values of
the shifts in the decay constants compared to their vacuum values. Using the
sum rules obtained, we also determine the shifts in the masses of these
particles due to nuclear matter and compare the results obtained with the
previous predictions in the literature.Comment: 16 Pages, 4 Figures and 3 Table
Scalar and vector self-energies of heavy baryons in nuclear medium
The in-medium sum rules are employed to calculate the shifts in the mass and
residue as well as the scalar and vector self-energies of the heavy and baryons, with Q being or quark. The maximum shift
in mass due to nuclear matter belongs to the baryon and it is found
to be . In the case of residue, it is
obtained that the residue of baryon is maximally affected by the
nuclear medium with the shift .
The scalar and vector self-energies are found to be , , , , , and , ,
, , and
.Comment: 13 Pages, 11 Figures and 5 Table
Properties of charmed-strange tensor meson
The mass and current coupling constant of the
charmed-strange meson is calculated in the framework of two-point QCD sum rule
approach. Although the quantum numbers of this meson is not exactly known, its
width and decay modes are consistent with , which we consider to
write the interpolating current used in our calculations. Replacing the light
strange quark with up or down quark we also compare the results with those of
charmed tensor meson and estimate the order of SU(3) flavor symmetry
violation.Comment: 9 Pages, 2 Figures and 1 Table, Some misprints are correcte
Subcritical and supercritical fluid extraction a critical review of its analytical usefulness
Subcritical R134a is suggested as a low-pressure alternative to supercritical CO2 in the supercritical fluid extraction technology in particular of palm oil application. Therefore, a measurement of solubility of palm oil in subcritical Rl34a will be carried out at temperatures of 40, 60, 70 and 80°C and pressures up to 300 bar. The solubility of carotene are also will be measured using UV Spectrophotometer. Results obtained from this study will be compared with the previous work and for the first time, simulation for the SFE process of palm oil will be performed using Artificial Neural Network (ANN) and it will be implemented in comparisons as well when the operating conditions of the previous findings are different from this study. It is expected that the solubility of the palm oil in subcritical Rl34a is much higher than SC-C02, and it is expected that R134a could be a viable alternative solvent to supercritical carbon dioxide as R134a could be perform well at a lower pressure used whereas can achieved a higher solubility compared to SC-C0
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