π+π+\pi^+\pi^+ and π+π−\pi^+\pi^- colliding in noncommutative space

By studying the scattering process of scalar particle pion on the noncommutative scalar quantum electrodynamics, the non-commutative amendment of differential scattering cross-section is found, which is dependent of polar-angle and the results are significantly different from that in the commutative scalar quantum electrodynamics, particularly when $\cos\theta\sim \pm 1$. The non-commutativity of space is expected to be explored at around $\Lambda_{NC}\sim$TeV.Comment: Latex, 12 page

Lambda polarization in pp -> p\Lambda K^+ \pi^+\pi^-\pi^+\pi^-

We show that there is a correlation between the invariant mass of the produced \Lambda K^+, \Lambda K^+\pi^+\pi^- or \Lambda K^+ \pi^+\pi^-\pi^+\pi^- system in the exclusive reaction pp\to p\Lambda K^+\pi^+\pi^-\pi^+\pi^- and the longitudinal or transverse momentum of $\Lambda$. Together with the longitudinal and transverse momentum dependence of Lambda polarization observed in inclusive reactions, such a correlation implies a dependence of Lambda polarization on these invariant masses. The qualitative features of this dependence are consistent with the recent observation by E766 collaboration at BNL. A quantitative estimation has been made using an event generator for $pp$ collisions. A detailed comparison with the data is made.Comment: 10 pages with 3 figures, submitted to J. Phys.

Study of the D^0 \to pi^-pi^+pi^-pi^+ decay

Using data from the FOCUS (E831) experiment at Fermilab, we present new measurements for the Cabibbo-suppressed decay mode $D^0 \to \pi^-\pi^+\pi^-\pi^+$. We measure the branching ratio $\Gamma(D^0 \to\pi^+\pi^- \pi^+\pi^-)/\Gamma(D^0 \to K^-\pi^+\pi^-\pi^+) = 0.0914 \pm 0.0018 \pm 0.0022$. An amplitude analysis has been performed, a first for this channel, in order to determine the resonant substructure of this decay mode. The dominant component is the decay $D^0 \to a_1(1260)^+ \pi^-$, accounting for 60% of the decay rate. The second most dominant contribution comes from the decay $D^0 \to \rho(770)^0\rho(770)^0$, with a fraction of 25%. We also study the $a_1(1260)$ line shape and resonant substructure. Using the helicity formalism for the angular distribution of the decay $D^0 \to \rho(770)^0\rho(770)^0$, we measure a longitudinal polarization of $P_L = (71 \pm 4\pm 2)$%.Comment: 38 pages, 8 figures. accepted for publication in Physical Review

Phase Motion in the Scalar Low-Mass π−π+\pi^-\pi^+ Amplitude in D+→π−π+π+D^+ \to \pi^-\pi^+\pi^+

This work is a direct and model-independent measurement of the low mass $\pi^+\pi^-$ phase motion in the $D^+ \to \pi^-\pi^+\pi^+$ decay. The results show a strong phase variation, compatible with an isoscalar $\sigma(500)$ meson. This result confirms the previous Fermilab E791 result which found evidence for the existence of this scalar particle using a full Dalitz-plot analysis.Comment: 5 pages, 2 figures, talk given at X International Conference on Hadron Spectroscopy (HADRON '03), Aschaffenburg, German

Model-independent approach to eta -> pi+ pi- gamma and eta' -> pi+ pi- gamma

We present a new, model-independent method to analyze radiative decays of mesons to a vector, isovector pair of pions of invariant mass square below the first significant pion-pion threshold in the vector channel. It is based on a combination of chiral perturbation theory and dispersion theory. This allows for a controlled inclusion of resonance physics without the necessity to involve vector meson dominance explicitly. As an example, the method is applied to an analysis of the reactions eta -> pi+ pi- gamma and eta'->pi+ pi- gamma.Comment: 16 pages, 4 figure

B-> rho pi, rho rho, pi pi: hunting for alpha

We determine the domains of the values of unitarity triangle angle alpha, allowed by the charmless strangeless B_d (\bar B_d) decays.Comment: 16 pages. Recent Belle results on CP asymmetries in B_d(\bar{B}_d)-->rho^+ rho^- decays are taken into account. Version to be published in Yad.Fi