Final State Interaction Effects Research Articles

Hydrodynamic approach to p–Pb

The formation and collective expansion of the fireball formed in ultrarelativistic p-A and d-A collisions is discussed. Predictions of the hydrodynamic model are compared to recent experimental results. The presence of strong final state interaction effects in the small dense systems is consistent with the observed azimuthal anisotropy of the flow and with the mass dependence of the average transverse momentum and of the elliptic flow. This raises the question of the mechanism explaining such a rapid build up of the collective flow and the large degree of local equilibration needed to justify this scenario.

Final-state interaction effects in neutral-current neutrino and antineutrino cross sections at MiniBooNE kinematics

The analysis of the recent neutral-current elastic neutrino and antineutrino-nucleus scattering cross sections measured by the MiniBooNE Collaboration requires relativistic theoretical descriptions also accounting for the role of final-state interactions. In this work we investigate the sensitivity to final-state interactions and compare the MiniBooNE data with the results obtained in the relativistic Green's function model with different parameterizations for the phenomenological relativistic optical potential.

Final State Interaction Effects in B0→J/ψπ0Decay

Final State Interaction Effects in B0→J/ψπ0Decay

Effects of Final-State Interactions in Pure Annihilation Decay of B0_s→π+π-

Effects of Final-State Interactions in Pure Annihilation Decay of B⁰_s→π⁺π^-

Quasi-free photoproduction of η-mesons off 3He nuclei

Quasi-free photoproduction of η-mesons has been measured off nucleons bound in 3He nuclei for incident photon energies from the threshold region up to 1.4 GeV. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with an almost 4π covering electromagnetic calorimeter, combining the TAPS and Crystal Ball detectors. The η-mesons were detected in coincidence with the recoil nucleons. This allowed a comparison of the production cross section off quasi-free protons and quasi-free neutrons and a full kinematic reconstruction of the final state, eliminating effects from nuclear Fermi motion. In the S11(1535) resonance peak, the data agree with the neutron/proton cross section ratio extracted from measurements with deuteron targets. More importantly, the prominent structure observed in photoproduction off quasi-free neutrons bound in the deuteron is also clearly observed. Its parameters (width, strength) are consistent with the expectations from the deuteron results. On an absolute scale the cross sections for both quasi-free protons and neutrons are suppressed with respect to the deuteron target pointing to significant nuclear final-state interaction effects.

ν¯linduced pion production from nuclei at∼1 GeV

We have studied charged current ${\overline{\ensuremath{\nu}}}_{l}$ induced one pion production from $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ nuclear targets at MiniBooNE and atmospheric antineutrino energies. The calculations have been done for the incoherent pion production process as well as for the pions coming from the hyperons in the quasielastic production of $\ensuremath{\Lambda}$ and $\ensuremath{\Sigma}$. The calculations are done in the local density approximation. For the inelastic processes the calculations have been done in the $\ensuremath{\Delta}$ dominance model, and we take into account the effect of Pauli blocking, Fermi motion of the nucleon, and renormalization of $\ensuremath{\Delta}$ properties in the nuclear medium. The effect of final state interaction (FSI) of pions is also taken into account. For the hyperon production, the nuclear medium effects due to Fermi motion and FSI effects due to hyperon-nucleon scattering have been taken into account. These results may be quite useful in the analysis of SciBooNE, MicroBooNE, $\mathrm{MINER}\ensuremath{\nu}\mathrm{A}$, and ArgoNeuT experiments when the pion analysis is done by using antineutrino beams.

Ambiguity of the final state interaction for neutral-current neutrino-nucleus scattering in the quasielastic region

We investigate the effect of final state interaction (FSI) on the neutrino (antineutrino) scattering via neutral current from a ${}^{12}$C target in the quasielastic region within the framework of a relativistic single-particle model. Three different descriptions of the FSI, which are a relativistic mean field, a complex optical potential, and its real potential, are taken into account for two incident neutrino energies of 500 MeV and 1 GeV. The effects of the FSI are studied not only on the differential cross sections but also on each longitudinal, transverse, and transverse interference cross section. We found that the FSI description may play a vital role for the estimation of those cross sections, and the FSI effects on each response cross section may differ from those on the differential cross section. However, the asymmetry between neutrino and antineutrino scattering cross sections turns out to be nearly independent of the FSI descriptions. Finally, possible FSI effects on the MiniBooNE data are studied in detail.

Probing vector mesons in deuteron breakup reactions

We study vector meson photoproduction from the deuteron at high momentum transfer, accompanied by break-up of the deuteron into a proton and neutron. The large $-t$ involved allows one of the nucleons to be identified as struck, and the other as a spectator to the $\gamma N\rightarrow VN$ subprocess. Corrections to the plane wave impulse approximation involve final state interactions (FSIs) between the struck nucleon or the vector meson, either of which is energetic, with the slow spectator nucleon. In this regime, the eikonal approximation is valid, so is employed to calculate the cross-section for the reaction. Due to the high-energy nature of the FSIs, the maxima of the rescatterings are located at nearly transverse directions of the fast hadrons. This results in two peaks in the angular distribution of the spectator nucleon, each corresponding to either the $V$-$N$ or the $p$-$n$ rescattering. The $V$-$N$ peak provides a new means of probing the $V$-$N$ interaction. This is checked for near-threshold $\phi$ and $J/\Psi$ photoproduction reactions which demonstrate that the $V$-$N$ peak can be used to extract the largely unknown amplitudes of $\phi$-$N$ and $J/\Psi$-$N$ interactions. Two additional phenomena are observed when extending the calculation of $J/\Psi$ photoproduction to the sub-threshold and high-energy domains. In the first case we observe overall suppression of FSI effects due to a restricted phase space for sub-threshold production in the rescattering amplitude. In the second, we observe cancellation of the $V$-$N$ rescattering amplitudes for vector mesons produced off of different nucleons in the deuteron.

Tensor meson photoproduction as a final state interaction effect

The model is presented to describe the ${f}_{2}(1270)$ meson photoproduction as a result of pion-pion interactions in the final state. Treating tensor mesons as objects dynamically created due to final state interactions is a convenient and straightforward way to employ data from $\ensuremath{\pi}\ensuremath{\pi}$ scattering like phase shifts and inelasticities for description of (photo)production reactions while retaining proper analytical structure of amplitudes, two-particle unitarity, and crossing symmetry. The model presented here can provide experimentally testable quantities like differential cross sections and $\ensuremath{\pi}\ensuremath{\pi}$ mass distributions as well as the strengths of partial waves corresponding to various ${f}_{2}(1270)$ helicities which are essential for partial wave analyses. It can also be used to compute moments of angular distribution and spin density matrix elements where partial wave interference effects are important.

Effects of Final State Interactions in Pure Annihilation Decay of $B^{0}_{s}\rightarrow\pi^{0}\pi^{0}$

We investigate the effects of final state interactions (FSI) contributions in the nonleptonic two body $B^{0}_{s} \rightarrow \pi^{0}\pi^{0}$ decay. The short distance interaction amplitude is calculated by using the annihilation diagrams and a tiny branching ratio is obtained, then the long distance amplitude is considered and calculated within FSI effects. For contributions of FSI, the ρ 0 ρ 0, π + π −(ρ + ρ −), K + K −(K +∗ K −∗) and $K^{0}\bar{K}^{0}(K^{0*}\bar{K}^{0*})$ are produced for intermediate states, in this case the π 0, π −(ρ −), K −(∗) and $\bar{K}^{0(*)}$ mesons are exchanged. The absorptive part of the diagrams is directly calculated and the dispersive part of the rescattering amplitude can be obtained from the absorptive part via the dispersion relation. The imaginary and real parts of the amplitudes are summed over all intermediate states. The predicted branching ratio of $B^{0}_{s} \rightarrow \pi^{0}\pi^{0}$ is 0.69×10−8 in the absence of FSI effects and it becomes 1.86×10−4 when FSI contributions are taken into account, while the experimental result is less than 2.1×10−4.

Final state interaction contribution to the observedBsdecays intoK+K−andπ+K−

Because at the tree level ${B}_{s}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$ is Cabibbo triple suppressed, so its branching ratio should be smaller than that of ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}^{\ensuremath{-}}$. The measurements present a reversed ratio as $R=\mathcal{B}({B}_{s}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}^{\ensuremath{-}})/\phantom{\rule{0ex}{0ex}}\mathcal{B}({B}_{s}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}})\ensuremath{\sim}4.9/33$. Therefore, it has been suggested that the transition ${B}_{s}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$ is dominated by the penguin mechanism, which is proportional to ${V}_{cb}{V}_{cs}^{*}$. In this work, we show that an extra contribution from the final state interaction to ${B}_{s}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$ via sequential processes ${B}_{s}\ensuremath{\rightarrow}{D}_{(s)}^{(*)}{\overline{D}}_{s}^{(*)}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$ is also substantial and should be superposed on the penguin contribution. Indeed, taking into account the final state interaction effects, the theoretical prediction on $R$ is well consistent with the data.

Two-Body Electrodisintegration of 4He Using Antisymmetrized Molecular Dynamics

The antisymmetrized molecular dynamics method is used to investigate the two-body electrodisintegration of 4He. Effects of final-state interactions are included via the Glauber multiple scattering approximation. Experimental data for the 4He longitudinal and transverse response functions are well described at high momentum transfer.

CC and NC Pion Production

The disappearance searching experiments use charged current quasielastic (CCQE) reaction to detect an arriving neutrino and reconstruct its energy, while the CC1π+ production can mimic the CCQE signal process. In appearance experiments, the NC1π0 production process can lead to a fake e- event by the impossibility for the detector of distinguish an arriving electron or a photon. Here we present a consistent model, from the point of view of the construction of the elemental amplitude, for the mentioned pion production background processes including bounding, smearing and final state interaction (FSI) effects in a single fashion. Results are comparable with more evolved approaches based on Monte Carlo simulations.

Evaluation of theγn→π−pdifferential cross section in theΔ-isobar region

Differential cross sections for the process $\ensuremath{\gamma}n\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}p$ have been extracted from MAMI-B measurements of $\ensuremath{\gamma}d\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}pp$, accounting for final-state interaction effects, using a diagrammatic technique taking into account the $NN$ and $\ensuremath{\pi}N$ final-state interaction amplitudes. Results are compared to previous measurements of the inverse process, ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}n\ensuremath{\gamma}$, and recent multipole analyses.

Effects of Final-State Interactions in B0->K+K- Decay

The decay of the B0 meson to the K+ and K- mesons is a pure annihilation decay; for this reason, in the framework of the quantum chromodynamics factorization (QCDF) approach, this decay has a small amplitude and a small branching ratio. In this study, we find that, before the K+ and K- mesons are produced in the final states, pair mesons such as π0π0(ρ0ρ0), π+π-(ρ+ρ-), K0K0(K0*K0*), D0D0(D0*D0*), D+sD-s(D+*sD-*s), φφ and ρ0φ are produced. The intermediate-state mesons via the exchange of K+(*), K0(*), π-(ρ-), D+(*)s, D0(*) and K-(*) mesons go to the K+ and K- final-state mesons. However, we calculate the B0 →K+K- decay in two different frameworks. The first framework is the QCDF method and the second one is the use of the final-state interaction (FSI) effects. The experimental branching ratios of B0 → K+K- decay are 1.3 and 2.3 ×10-7, and our results obtained by the QCDF method and FSI are 0.11 ×10-7 and 0.09 ∼3.21 ×10-7, respectively.

Effects of final-state interactions in neutrino-nucleus interactions

Final-state interaction (FSI) effects are discussed in the context of Monte Carlo simulations of neutrino-nucleus interactions. A role of formation time is explained and several models describing this effect are compared. Various observables which are sensitive to FSI effects are reviewed including pion-nucleus interaction and hadron yields in backward hemisphere. NuWro Monte Carlo neutrino event generator is described and its ability to understand neutral current ${\ensuremath{\pi}}^{0}$ production data in $\ensuremath{\sim}1$ GeV neutrino flux experiments is demonstrated.

WEAK ANNIHILATION TOPOLOGIES AND FINAL STATE INTERACTIONS IN $B^+ \rightarrow D^+_s\phi$ DECAY

In this research, the hadronic decay of [Formula: see text] is analyzed by using "QCD factorization" (QCDF) method and final state interaction (FSI). First, the [Formula: see text] decay is calculated via QCDF method and only the annihilation graphs exist in that method. Then, FSI is considered to solve the [Formula: see text] decay as a sizable correction and the D+*K0, D0*K+ and [Formula: see text] via the exchange of [Formula: see text], K-(*) and [Formula: see text] mesons are chosen for the intermediate states. To estimate the intermediate states amplitudes, QCDF method is again used. These amplitudes are used in the absorptive part of the diagrams. The experimental branching ratio of [Formula: see text] decay is less than 1.9×10-6 and our results according to QCDF method and FSI effects are 0.16×10-6 and 1.86×10-6, respectively.

Production ofK+K−pairs in proton-proton collisions at 2.83 GeV

Differential and total cross sections for the pp -> ppK+K- reaction have been measured at a proton beam energy of 2.83 GeV using the COSY-ANKE magnetic spectrometer. Detailed model descriptions fitted to a variety of one-dimensional distributions permit the separation of the pp -> pp phi cross section from that of non-phi production. The differential spectra show that higher partial waves represent the majority of the pp -> pp phi total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave phi-p enhancement near threshold. The non-phi data can be described in terms of the combined effects of two-body final state interactions using the same effective scattering parameters determined from lower energy data.

Probing strongly interacting W’s at the ILC with polarized beams

AbstractWe study the possibility of fingerprinting a strongly interactingWboson sector which is consistent with present day LHC searches at the ILC with longitudinal as well as transversely polarized electron and positron beams. We account for the final state interaction using a suitable Omnès formalism in terms of a plausible resonance description, and carry out thorough analyses of cross sections, asymmetries and angular distributions of the W′s. We carry out a comparison with other extensions of the Standard Model, where heavy additional Z′bosons arise naturally. We also consider the effect of the strong final state interaction on a correlation that depends on$ \left( {{\phi_{ - }} - {\phi_{ + }}} \right) $, where theϕ∓are the azimuthal angles of decay leptons, and find that it is a useful discriminant.

Final state interaction effects in electrodisintegration of the deuteron in the Bethe-Salpeter approach

The electrodisintegration of the deuteron is considered within a relativistic model of nucleon-nucleon interaction based on the Bethe-Salpeter approach with a separable interaction kernel. The exclusive cross section is calculated within the impulse approximation under various kinematic conditions. Final state interactions between the outgoing nucleons are taken into account. The comparison of nonrelativistic and relativistic calculations is presented. Partial-wave states of the neutron-proton pair with total angular momentum $J=0,1$ are considered.