6,128 research outputs found
Chiral-Symmetry and Strange Four-Quark Matrix Elements
We consider the matrix elements of the left-handed flavor-conserving
four-quark operators in the nucleon and pion states. Using chiral symmetry, we
derive relationships among these matrix elements. We argue that the rule of hyperon and kaon non-leptonic weak decay implies possible large
strange-quark content in the nucleon and pion.Comment: 10 pages in Plain TeX, MIT CTP #218
Drell-Hearn-Gerasimov Sum-Rule for the Deuteron in Nuclear Effective Field Theory
The Drell-Hearn-Gerasimov sum rule for the deuteron is studied in nuclear
effective field theory. The low-energy theorem for the spin-dependent Compton
amplitude is derived to the next-to-leading order in low-energy
expansion. The spin-dependent photodisintegration cross section
is calculated to the same order, and its contribution to
the dispersive integral is evaluated.Comment: 8 pages, 2 figure
Sum Rules and Spin-Dependent Polarizabilities of the Deuteron in Effective Field Theory
We construct sum rules for the forward vector and tensor polarizabilities for
any spin- target and apply them to the spin-1 deuteron. We calculate these
polarizabilities of the deuteron to the next-to-leading order in the pionless
effective field theory.Comment: 10 pages, figures include
The three-boson system at next-to-leading order in an effective field theory for systems with a large scattering length
We analyze how corrections linear in the effective range, r_0, affect
quantities in the three-body sector within an effective field theory for
short-range interactions. We demonstrate that observables can be obtained
straightforwardly using a perturbative expansion in powers of r_0. In
particular, we show that two linear-in-r_0 counterterms are needed for
renormalization at this order if scattering-length-dependent observables are
considered. We exemplify the implications of this result using various
three-body observables. Analytic results for the running of the
next-to-leading-order portion of the three-body force in this effective field
theory are provided. Expressions which incorporate O(r_0) corrections and
relate the positions of features observed in three-atom recombination near a
Feshbach resonance are presented.Comment: revtex4, 30 pages, 6figures, version2 accepted for publication in
Annals of Physics, section on universal relations at NLO rewritte
Universality of the EMC Effect
Using effective field theory, we investigate nuclear modification of nucleon
parton distributions (for example, the EMC effect). We show that the
universality of the shape distortion in nuclear parton distributions (the
factorisation of the Bjorken x and atomic number (A) dependence) is model
independent and emerges naturally in effective field theory. We then extend our
analysis to study the analogous nuclear modifications in isospin and spin
dependent parton distributions and generalised parton distributions.Comment: 8 pages, 2 figure
Heavy-quark contribution to the proton's magnetic moment
We study the contribution to the proton's magnetic moment from a heavy quark
sea in quantum chromodynamics. The heavy quark is integrated out perturbatively
to obtain an effective dimension-6 magnetic moment operator composed of three
gluon fields. The leading contribution to the matrix element in the proton
comes from a quadratically divergent term associated with a light-quark tensor
operator. With an approximate knowledge of the proton's tensor charge, we
conclude that a heavy sea-quark contribution to the proton's magnetic moment is
positive in the asymptotic limit. We comment on the implication of this result
for the physical strange quark.Comment: 4 pages, 2 figure
Deuteron Compton Scattering in Effective Field Theory And Spin-Independent Nucleon Polarizabilities
Deuteron Compton scattering is calculated to in pionless
effective field theory using a dibaryon approach. The vector amplitude, which
was not included in the previous pionless calculations, contributes to the
cross section at and influences significantly the extracted
values of nucleon electric polarizability at incident photon energy 49 MeV. We
recommend future high precision deuteron compton scattering experiments being
performed at 25-35 MeV photon energy where the nucleon polarizability effects
are appreciable and the pionless effective field theory is most reliable. For
example, a measurement at 30 MeV with a 3% error will constrain the isoscalar
nucleon electric polarizability with a error.Comment: 11 pages, 5 figures include
R-parity Violation and Semileptonic Decays of B-meson
We investigate the effects of R-parity violation on the semileptonic decays
of B-meson in the minimal supersymmetric standard model with explicit R-parity
violation and discuss its physical implications. We find that the semileptonic
decays of B-meson can be largely affected by the R-parity violation.Comment: 10 pages, LaTex file, no figure. References and a table are added.
Tables are improve
A note on nonperturbative renormalization of effective field theory
Within the realm of contact potentials, the key structures intrinsic of
nonperturbative renormalization of -matrices are unraveled using rigorous
solutions and an inverse form of algebraic Lippmann-schwinger equation. The
intrinsic mismatches between effective field theory power counting and
nonperturbative divergence structures are shown for the first time to preclude
the conventional counterterm algorithm from working in the renormalization of
EFT for scattering in nonperturbative regimes.Comment: 6 pages, no figure, version to appear in J.Phys.
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