Inelastic Final State Interactions Research Articles

Baryon femtoscopy in = 2.76 TeV Pb–Pb collisions at ALICE

We present femtoscopic results for proton and Λ correlation functions measured by ALICE in = 2.76 TeV Pb–Pb collisions. Femtoscopic radii are extracted from pp, p̄p̄, and pp̄ pairs. Comparisons of these radii with those from pion and kaon analyses reveal an approximate transverse mass scaling that is consistent with explanations of radial flow. Inelastic final state interactions are explored in baryon-antibaryon correlations functions to investigate their relationship with reduced proton yields at LHC energies.

Inelastic Final State Interactions in [formula omitted] Decays

A method parametrizing all inelastic final state interactions (FSI) in $B\to PP$ decays is presented ($P$ - pseudoscalar meson). The method explicitly shows how rescattering leads to the replacement of the short-distance amplitudes with the effective quark diagram amplitudes, and how it affects the extraction of the unitarity triangle angle $\gamma $ from the data. It is furthermore pointed out that the size of FSI effects cannot be determined from $B^0_d \to K^+ K^-$ decays in a satisfactory way. The case of SU(3)-violating FSI is also discussed. When fits to the branching ratios of all $B \to PP$ decays are performed with all inelastic FSI included, the extracted value of $ \gamma $ is shifted down by some $20^o-30^o$ when compared to the no-FSI analyses, and becomes consistent with the Standard Model value of $ 65^o \pm 7^o$.

STUDY OF DIRECT CP ASYMMETRY IN B+→K0π+

The direct CP asymmetry (aCP) for the process B+→π+K0 is studied including the contributions arising from both the QCD and electroweak penguins and the long range inelastic final state interactions (IFSI). The usually neglected space-like penguins and the annihilation contributions are also taken into account in our analysis. The next-to-leading order low energy effective Hamiltonian and BSW model are used to evaluate the weak transition matrix elements. The effect of space-like and annihilation diagrams are studied using the Lepage and Brodsky model. We found that as a result of FSI, the CP asymmetry and the branching ratio are suppressed slightly in comparison to no FSI situation, but the obtained branching ratio with FSI agrees very well with the present experimental value. With our predicted value of aCP~1010, charged B mesons are required to resolve the CP asymmetry experimentally at 3σ level.

Long-range two-body final-state interactions and directCPasymmetry inB+→π+K0decay

We present a calculation of the direct $\mathrm{CP}$ asymmetry ${A}_{\mathrm{CP}}^{\mathrm{dir}}$ for the process ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}^{0}$ including the effects of long-range two-body inelastic final-state interactions (FSI). We admit four two-body channels in our calculation: ${B}^{+}\ensuremath{\rightarrow}({\ensuremath{\pi}}^{+}{K}^{0}),(\ensuremath{\eta}{K}^{+}),$ ${(D}_{s}^{+}{D}^{0})$ and the charge-exchange channel ${\ensuremath{\pi}}^{0}{K}^{+}.$ The strong scattering is described in terms of Pomeron and Regge exchanges. We find that the direct $\mathrm{CP}$ asymmetry is enhanced by a factor of $\ensuremath{\sim}3$ as a result of FSI, but remains well short of the claims of (10--20)% in recent literature. A critical assessment of papers claiming large $\mathrm{CP}$ asymmetries is also presented. Many-body decay channels could play an important role in direct $\mathrm{CP}$ asymmetry; however, their contribution is hard to estimate.

Nonfactorizable effects in spectator and penguin amplitudes of hadronic charmlessBdecays

Nonfactorizable effects in hadronic charmless B -> PP, VP decays can be parametrized in terms of the effective number of colors N_c in the effective parameters $a_i^{eff}$ that are linear combinations of Wilson coefficients. It is shown that N_c(V+A) in the penguin amplitudes induced by the (V-A)(V+A) four-quark operators is different from N_c(V-A) in the decay amplitudes arising from the (V-A)(V-A) operators. Central values of the branching ratios of $B^\pm\to\omega \pi^\pm$ and $B\to\pi\pi$ decays favor $N_c(V-A)\approx 2$, in accordance with the nonfactorizable effect observed in $B\to D^{(*)}\pi (\rho)$. Measurements of the interference effects in $B^-\to\pi^-(\rho^-)\pi^0 (\rho^0)$ decays will provide a more decisive test on the parameter N_c(V-A). However, $N_c(V+A)\sim 2$ is ruled out by $B^\pm\to\phi K^\pm$ and $B\to\phi K^*$. We find that N_c(V+A) lies in the range $10\geq N_c(V+A)\geq 4.3$, subject to the corrections from W-annihilation and space-like penguin effects. With $N_c(V-A)\approx 2$ we show that the branching ratio of $B\to\eta' K$ is enhanced considerably at small values of 1/N_c(V+A) so that it is compatible with experiment. In particular, the measurement of $B^0\to\eta' K^0$ is now well explained without resorting to any new mechanism or new physics beyond the Standard Model. Finally, we point out that it is difficult to understand the observed large branching ratio of $B^\pm\to\omega K^\pm$ within the present framework. Inelastic final-state interactions may alleviate the difficulty with this decay mode.

Inelastic final-state interactions in B → VV →π K processes

We study the final-state interactions in $B \to \pi K$ decays through $B \to VV \to \pi K$ processes where the inelastic rescattering occurs via single pion exchange. The next-to-leading order low energy effective Hamiltonian and BSW model are used to evaluate the weak transition matrix elements and the final-state interactions. We found that the final-state interaction effects in $B \to \rho K^* \to \pi K$ processes are significant. The Fleischer-Mannel relation about the CKM angle $\gamma$ may be significantly modified.

Inelastic final-state interactions and two-body hadronicBdecays into single-isospin channels

The role of inelastic final-state interactions in $\mathrm{CP}$ asymmetries and branching ratios is investigated in certain chosen single-isospin two-body hadronic $B$ decays. Treating final-state interactions through Pomeron and Regge exchanges, we demonstrate that inelastic final-state interactions could lead to sizable effects on the $\mathrm{CP}$ asymmetry.

A simplified approach to determine α and the penguin amplitude in Bd → ππ

The effect of inelastic final-state interactions (IFSIs) on the determination of the weak phase α from the isospin triangles of B → ππ is qualitatively illustrated. Neglecting the electroweak penguins and IFSIs and assuming the dominance of the top-quark loop in strong penguin diagrams, we propose an experimentally accessible way to approximately determine α and the penguin amplitude in B d → ππ. This approach relies on a simplified isospin consideration and the factorization approximation, and its feasibility is irrelevant to the time-dependent measurements of B d → ππ.

Test of factorization in Cabibbo-favored two-body hadronic decays of D mesons.

We propose a method that involves quantities independent of strong interaction phases to test the factorization model in Cabibbo-favored two-body decays of [ital D] mesons. The method tests if the factorization model correctly predicts the magnitudes of the isospin amplitudes. We have applied this method to the Cabibbo-favored decays [ital D][r arrow][ital [bar K]][pi], [ital [bar K]][rho], and [ital [bar K]][sup *][pi]. The test, used as a diagnostic tool, allows us to pinpoint the isospin amplitudes for which the factorization model fails. We discuss the roles of annihilation terms and inelastic final state interactions in resolving the differences between the factorization model predictions and experiments.

Test of factorization in D--> pi pi and D-->KK-bar decays.

We propose a method that involves quantities independent of strong interaction phases to test the factorization model in D\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi} and KK\ifmmode\bar\else\textasciimacron\fi{} decays. The method allows us to conclude that the factorization model correctly predicts \ensuremath{\Vert}${\mathit{A}}_{2}^{\mathrm{\ensuremath{\pi}}\mathrm{\ensuremath{\pi}}}$\ensuremath{\Vert}, overestimates \ensuremath{\Vert}${\mathit{A}}_{0}^{\mathrm{\ensuremath{\pi}}\mathrm{\ensuremath{\pi}}}$\ensuremath{\Vert} and \ensuremath{\Vert}${\mathit{A}}_{1}^{\mathit{KK}\mathit{\ifmmode\bar\else\textasciimacron\fi{}}}$\ensuremath{\Vert}, and underestimates \ensuremath{\Vert}${\mathit{A}}_{0}^{\mathit{KK}\mathit{\ifmmode\bar\else\textasciimacron\fi{}}}$\ensuremath{\Vert}. We rule out the Penguin mechanism as the solution to the disagreement between theory and experiment. We believe inelastic final state interactions are responsible for bridging the gap between theory and experiment.

Many-body correlation effects on the longitudinal response in the quasielastic (e,e') reaction.

A study is made of the influence of many-body corrections on the longitudinal response function for the inclusive quasielastic (e, e') reaction. This response function is well known to be suppressed, by about a factor of two, when compared with theoretical predictions based on the concept of single nucleon ejection. This is a characteristic of the data that persists through a wide range of different nuclei and suggests a violation of the Coulomb sum rule. It is here shown how an estimation of the effect of many-body correlations, including a consistent treatment of inelastic final state interactions, can be computed through a relationship to the nuclear optical model. The approximations are such that the Coulomb sum rule in guaranteed to remain satisfied providing the optical potential is hermitian analytic. Calculations of the longitudinal response are carried out within the Fermi Gas Model using phenomenological parameterizations of the nuclear optical potential. The reductions

Unitary and inelastic final state interactions

Inelasticity is taken into account in final state interactions by treating the problem in a coupled-channel approach. This generalizes the usual Omnès formula and incorporates unitary constraints which are pointed out. It is shown that the important notion is that of fundamental solutions to the Hilbert problem introduced by Muskhelishvili and Vekua, the practical determination of which is described. In terms of these, the polynomial ambiguities can be controlled in a direct way although there are no analytic solutions to the problem as in the usual one-channel treatment. We illustrate these techniques on an example concerning the pion form factor in the inelastic region. Further physical applications will be given in future publications.