Development of a systematic approach to conversion of the ileoanal pouch into continent ileostomy

Based on practical experience, a systematic approach to conversion of ileal J-pouches into continent ileostomies is developed by defining three types of conversion surgery, each with two subtypes. Type 1 refers to conversion without pouch reconstruction, type 2 to partial pouch reconstruction, and type 3 to complete pouch reconstruction. The subdivisions (a and b) take into account whether the afferent loop of the former pelvic pouch (a) or a higher ileal/jejunal segment of the small intestine (b) is used in conversion and/or reconstruction. The six resulting surgical variants are shown in schematic illustrations with accompanying descriptions of technical details to provide the specialized surgeon with comprehensive technical guidance

Comment on soft-pion emission in DVCS

The soft-pion theorem for pion production in deeply virtual Compton scattering, derived by Guichon, Mosse and Vanderhaegen, is shown to be consistent with chiral perturbation theory. Chiral symmetry requires that the nonsinglet operators corresponding to spin-independent and spin-dependent parton distributions have the same anomalous dimensions in cases where those operators are related by chiral transformations. In chiral perturbation theory, their scale-dependences can thus be absorbed in the coefficents of the corresponding effective operators, without affecting their chiral structures.Comment: 2 pages, RevTe

Final-sate radiation in electron-positron annihilation into a pion pair

The process of $e^+e^-$ annihilation into a $\pi^+\pi^-$ pair with radiation of a photon is considered. The amplitude of the reaction $e^+e^-\to\pi^+\pi^-\gamma$ consists of the model independent initial-state radiation (ISR) and model-dependent final-state radiation (FSR). The general structure of the FSR tensor is constructed from Lorentz covariance, gauge invariance and discrete symmetries in terms of the three invariant functions. To calculate these functions we apply Chiral Perturbation Theory (ChPT) with vector and axial-vector mesons. The contribution of $e^+e^-\to\pi^+\pi^-\gamma$ process to the muon anomalous magnetic moment is evaluated, and results are compared with the dominant contribution in the framework of a hybrid model, consisting of VMD and point-like scalar eletrodynamics. The developed approach allows us also to calculate the $\pi^+\pi^-$ charge asymmetry.Comment: 21 pages, 8 figure

Radiative Kaon Decays K±→π±π0γK^\pm\to\pi^\pm\pi^0\gamma and Direct CP Violation

It is stressed that a measurement of the electric dipole amplitude for direct photon emission in \kpm decays through its interference with inner bremsstrahlung is important for differentiating among various models. Effects of amplitude CP violation in the radiative decays of the charged kaon are analyzed in the Standard Model in conjunction with the large $N_c$ approach. We point out that gluon and electromagnetic penguin contributions to the CP-violating asymmetry between the Dalitz plots of \kpm are of equal weight. The magnitude of CP asymmetry ranges from $2\times 10^{-6}$ to $1\times 10^{-5}$ when the photon energy in the kaon rest frame varies from 50 MeV to 170 MeV.Comment: Latex, 11 pages, ITP-SB-93-36, IP-ASTP-22-9

On the analysis of the pion--nucleon σ\sigma--term: The size of the remainder at the Cheng--Dashen point

We calculate the one--loop contributions of order $M_\pi^4$ to the difference $\Delta_R$ between the on--shell pion--nucleon scattering amplitude $\bar{D}^+(0,2M_\pi^2)$ at the Cheng--Dashen point $\nu =0$, $t=2M_\pi^2$ and the scalar form factor $\sigma (2M_\pi^2)$ in the framework of heavy baryon chiral perturbation theory. We proof that to this order $\Delta_R$ contains $no$ chiral logarithms and therefore it vanishes simply as $M_\pi^4$ in the chiral limit. Numerically, we find as an upper limit $\Delta_R \simeq 2\,$MeV.Comment: 7 pp, LaTeX, uses epsf, 1 figure in separate PS fil

One-loop vertex integrals in heavy-particle effective theories

We give a complete analytical computation of three-point one-loop integrals with one heavy propagator, up to the third tensor rank, for arbitrary values of external momenta and masses.Comment: 10 pages, Latex, to appear in J. Phys.

FCNC in left-right symmetric theories and constraints on the right-handed scale

We revise the limits on the FCNC higgses in manifestly left-right symmetric theories. It is shown that the combination of the Kobayashi-Maskawa CP-violation with the tree level $\Delta S=2$ higgs exchange gives very large contribution to the CP-violating $\epsilon$ parameter. It leads to the new strong constraint on the FCNC higgs mass, M>50- 100 TeV, enhanced by factor of the order $\sqrt{m_t/m_c}$. Being addressed to the supersymmetric left-right models, FCNC problem requires both right-handed scale and supersymmetric mass parameters be heavier than 50 TeV for $tan\beta\sim 1$. The most relaxed case corresponds to $tan\beta\sim 20- 30$ where right-handed scale can be of the order of few TeV.Comment: 11 pages, latex, 3 figure

The reaction πN→ππN\pi N \to \pi \pi N at threshold in chiral perturbation theory

In the framework of heavy baryon chiral perturbation theory, we give thIn the framework of heavy baryon chiral perturbation theory, we give the chiral expansion for the $\pi N \to \pi \pi N$ threshold amplitudes $D_1$ and $D_2$ to quadratic order in the pion mass. The theoretical results agree within one standard deviation with the empirical values. We also derive a relation between the two threshold amplitudes of the reaction $\pi N \to \pi \pi N$ and the $\pi \pi$ S--wave scattering lengths, $a_0^0$ and $a_0^2$, respectively, to order ${\cal O}(M_\pi^2)$. We show that there are uncertainties mostly related to resonance excitation which make an accurate determination of the $\pi \pi$ scattering length $a_0^0$ from the $\pi \pi N$ threshold amplitudes at present very difficult. The situation is different in the $\pi \pi$ isospin two final state. Here, the chiral series converges and one finds $a_0^2 = -0.031 \pm 0.007$ consistent with the one--loop chiral perturbation theory prediction.Comment: 30 pp, LaTeX file, uses epsf, 6 figures (appended), corrections in sections 5 and 6, conclusions unchange

Aspects of chiral pion-nucleon physics

The next-to-leading order chiral pion-nucleon Lagrangian contains seven finite low-energy constants. Two can be fixed from the nucleon anomalous magnetic moments and another one from the quark mass contribution to the neutron-proton mass splitting. We find a set of nine observables, which to one loop order do only depend on the remaining four dimension two couplings. These are then determined from a best fit. We also show that their values can be understood in terms of resonance exchange related to $\Delta$ excitation as well as vector and scalar meson exchange. In particular, we discuss the role of the fictitious scalar-isoscalar meson. We also investigate the chiral expansion of the two P-wave scattering volumes $P_1^-$ and $P_2^+$ as well as the isovector S-wave effective range parameter $b^-$. The one-loop calculation is in good agreement with the data. The difference $P_1^- - P_2^+$ signals chiral loop effects in the $\pi N$ P-waves. The calculated D- and F-wave threshold parameters compare well with the empirical values.Comment: 19 pp, LaTeX, enlarged and revised version, title changed, minor corrections in section 4, more detailed discussion in section 5, additional results in sec. 6 and the appendix, accepted for publication in Nucl. Phys.