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 $\Delta I = 1/2$ 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 $f_1(\omega)$ is derived to the next-to-leading order in low-energy expansion. The spin-dependent photodisintegration cross section $\sigma^P-\sigma^A$ 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-$S$ 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 $\mathcal{O}(Q^2)$ 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 $\mathcal{O}(Q^2)$ 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 $\sim 30$ 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 $T$-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 $NN$ scattering in nonperturbative regimes.Comment: 6 pages, no figure, version to appear in J.Phys.