Final State Interaction Effects Research Articles

Coupled channels and production of near-threshold [formula omitted] resonances in e+e− annihilation

The effects of final-state interaction of hadrons, produced in e+e− annihilation near the threshold, are discussed. If there is a loosely bound state or a virtual state in a system of produced hadrons, then the energy dependence of hadroproduction cross section is very strong. Our approach is based on the use of the effective potentials accounting for the interaction between hadrons in the final state. The cases of a few channels with nonzero transition amplitudes between them are considered. It is shown that these transitions drastically change the energy dependence of the cross sections. In particular, a narrow resonance below the threshold in one channel leads to a broad peak in another channel. We explained the non-trivial energy dependence of the production cross sections of BB¯, B⁎B¯, BB¯⁎, B⁎B¯⁎ near the thresholds in e+e− annihilation and obtained good agreement between our predictions and the experimental data available.

Quantifying Effects Of Final State Interactions On Pion Production In DUNE Using Monte Carlo Event Generators

The analysis of pion production in neutrino-nucleus scattering is crucial to quantify the effect of final state interactions (FSI) in the energy regime of DUNE and other long-baseline neutrino experiments since FSI modify the number of pions that emerge in the final state as compared to the number of pions produced in the initial (primary) state. Not only the number of pions but also their charge gets changed due to the prevailing FSI effects. In the present work, we will study the effect of FSI on pions after their production at the initial neutrino-nucleus interaction vertex using two different Monte Carlo (MC) simulation tools viz. GENIE (version: 3.0.6) and NuWro (version: 19.2.2). Considering the DUNE experimental set-up, we observe pion production in νµ and 40 Ar nucleus interactions for an event sample of 1 million for each generator. We find that there are some differences in the pion number observed in the primary and final states of two generators and that the differences are above statistical fluctuations. We observe that GENIE (version: 3.0.6) is more responsive (less transparent) to absorption and charge exchange processes as compared to NuWro (version: 19.2.2).

Determination of the titanium spectral function from (e, e′p) data

The E12-14-012 experiment, performed in Jefferson Lab Hall A, has measured the (e,e'p) cross section in parallel kinematics using a natural titanium target. Here, we report the full results of the analysis of the data set corresponding to beam energy 2.2 GeV, and spanning the missing momentum and missing energy range 15 <= pm <= 250 MeV/c and 12 <= Em <= 80 MeV. The reduced cross section has been measured with ~7% accuracy as function of both missing momentum and missing energy. We compared our data to the results of a Monte Carlo simulations performed using a model spectral function and including the effects of final state interactions. The overall agreement between data and simulations is quite good (chi2/d.o.f. = 0.9).

Quantifying Effects of Final-State Interactions on Energy Reconstruction in DUNE

In neutrino-nucleus interactions, the particles produced at the primary vertex may be different from the particles observed in the final state. This is due to the effect of final-state interactions (FSI) on the particles during their transport in the nuclear matter to reach the detector (final state) after their production at the primary vertex. In this report, the energy reconstruction is done for charged current quasielastic (CCQE) and charged current resonance (CCRES) scatterings on the event-by-event basis using the calorimetric method, and NuWro and GENIE simulation tools. In addition, the percentage of fake events in CCQE and CCRES interactions is presented. It is found that the percentage of fake events is more than 50% for both CCQE and CCRES processes for both the generators, if we apply the condition for the signal events that the particles observed in the final state should be the same as the particles produced at the primary vertex. Based on our definition of signal events, the reconstructed energy and number of fake events may change, and this influences the measurement of oscillation parameters in long-baseline experiments like DUNE.

Sivers asymmetry in inelastic $J/ψ$ leptoproduction at the EIC

We study the Sivers asymmetry in inelastic J/\psiJ/ψ leptoproduction, ep^\uparrow \to e+ J/\psi+Xep↑→e+J/ψ+X, within a transverse momentum dependent scheme, the so-called generalized parton model (GPM). The effects of final-state interactions are properly taken into account by employing the color-gauge invariant GPM (CGI-GPM). For the J/\psiJ/ψ formation the non-relativistic QCD (NRQCD) framework is adopted. Predictions for unpolarized cross sections and maximized Sivers asymmetries at EIC energies are given.

Determination of the argon spectral function from(e,e′p)data

The E12-14-012 experiment, performed in Jefferson Lab Hall A, has measured the $(e, e'p)$ cross section in parallel kinematics using a natural argon target. Here, we report the full results of the analysis of the data set corresponding to beam energy 2.222 GeV, and spanning the missing momentum and missing energy range $15 \lesssim p_m \lesssim 300$ MeV/c and $12 \lesssim E_m \lesssim 80$ MeV. The reduced cross section, determined as a function of $p_m$ and $E_m$ with $\approx$4\% accuracy, has been fitted using the results of Monte Carlo simulations involving a model spectral function and including the effects of final state interactions. The overall agreement between data and simulations turns out to be quite satisfactory ($\chi^2$/n.d.o.f.=1.9). The resulting spectral function will provide valuable new information, needed for the interpretation of neutrino interactions in liquid argon detectors.

Resonance contributions in B^-rightarrow K^+K^-pi ^- within the light-cone sum rule approach

In this work, we study the resonance contributions to the decay B^-rightarrow K^+K^-pi ^-, which is dominated by the scalar f_0(980), K_0^*(1430), vector rho (1450), phi (1020), K^*(892) and tensor f_2(1270) resonances. The three-body decay is reduced to various quasi two-body decays, where the B meson firstly decays into a resonance and a pion or a kaon, subsequently the resonance decays into the other two final-state mesons. The quasi two-body decays are calculated within the light-cone sum rule approach utilizing the leading twist B meson light-cone distribution amplitudes. Finally, the decay branching fraction contributions from each resonance is calculated. Some of them are compatible with experiment or previous theoretical works. Including the effects of non-resonant and final-state interactions, we also evaluate the total branching fraction.

Unfolding the effects of final-state interactions and quantum statistics in two-particle angular correlations

Angular correlations of identified particles measured in ultrarelativistic proton-proton (pp) and heavy-ion collisions exhibit a number of features which depend on the collision system and particle type under consideration. Those features are produced by mechanisms, such as (mini)jets, elliptic flow, resonance decays, and conservation laws. In addition, of particular importance are those related to the quantum statistics (QS) and final-state interactions (FSIs). In this paper we show how to unfold the QS and FSI contributions in angular correlation functions by employing a Monte Carlo approach and using momentum correlations (femtoscopy), focusing on pp reactions. We validate the proposed method with PYTHIA 8 Monte Carlo simulations of pp collisions at $\sqrt{s}=13$ TeV coupled to calculations of QS and FSI effects with the Lednick\'y and Lyuboshitz formalism and provide predictions for the unfolded effects. In particular, we show how those effects modify the shape of the angular correlation function with emphasis on pions and protons. Most importantly, specific structures observed in the near-side region for both baryon-baryon and baryon-antibaryon pairs, originating from the strong interaction, are unveiled with the proposed method.

Final State Interaction Analysis and Branching Fraction Calculations of $$\varvec{B^+_c\rightarrow D^+{\bar{D}}^0(D^+D^0)}$$ Decays

The LHC experiments have been measured the branching fractions for $$B^+_c$$ decays to two pseudoscalar charm mesons by multiplying the production rates for $$B^+_c$$ relative to $$B^+_u$$ mesons (in units of $$10^{-6}$$ ): $$\begin{aligned} (f_c/f_u){\mathcal {B}}(B^+_c\rightarrow D^+{\bar{D}}^0)_{EXP}=3.04\pm 2.87,\quad (f_c/f_u){\mathcal {B}}(B^+_c\rightarrow D^+D^0)_{EXP}=1.10\pm 2.02. \end{aligned}$$ We have calculated the branching fractions of these decay modes by using the QCD factorization (QCDF) approach and obtained; $${\mathcal {B}}(B^+_c \rightarrow D^+{\bar{D}}^0)_{QCDF}=(0.28\pm 0.08)\times 10^{-4}$$ and $${\mathcal {B}}(B^+_c \rightarrow D^+D^0)_{QCDF}=(0.60\pm 0.17)\times 10^{-6}$$ . Consider to upper limit of production ratio ( $$f_c/f_u=0.012$$ ), the QCDF results are 10 and $$10^2$$ times smaller than experimental results, respectively. The effects of the final state interaction (FSI) have compensated for the smallness of the theoretical results. After entering the effects of FSI, acceptable results have been obtained (in units of $$10^{-6}$$ ): $$\begin{aligned} (f_c/f_u){\mathcal {B}}(B^+_c\rightarrow D^+{\bar{D}}^0)_{FSI}=3.08\pm 0.32,\quad (f_c/f_u){\mathcal {B}}(B^+_c\rightarrow D^+D^0)_{FSI}=0.62\pm 0.07. \end{aligned}$$

Final state interaction in the pn and nn decay channels of $$^4_\varLambda $$He

We study the effects of final state interactions in the non-mesonic weak decay $\Lambda N \rightarrow nN$ (n is a neutron and N is either a neutron or a proton) of the hypernucleus $_\Lambda^4$He. Using a three-body model the effects of distortion of the interaction of the emitted nucleon pair with the residual nucleus is considered. We also study the influence of the final state interaction between the emitted nucleons using the Migdal-Watson model. The effect of spin symmetries in the final state of the pair is also considered. Based on our calculations, we conclude that final state interactions play a minor role in the kinetic energy spectrum of the emitted nucleon pair.

Examination of coalescence as the origin of nuclei in hadronic collisions

The origin of weakly-bound nuclear clusters in hadronic collisions is a key question to be addressed by heavy-ion collision (HIC) experiments. The measured yields of clusters are approximately consistent with expectations from phenomenological statistical hadronisation models (SHMs), but a theoretical understanding of the dynamics of cluster formation prior to kinetic freeze out is lacking. The competing model is nuclear coalescence, which attributes cluster formation to the effect of final state interactions (FSI) during the propagation of the nuclei from kinetic freeze out to the observer. This phenomenon is closely related to the effect of FSI in imprinting femtoscopic correlations between continuum pairs of particles at small relative momentum difference. We give a concise theoretical derivation of the coalescence--correlation relation, predicting nuclear cluster spectra from femtoscopic measurements. We review the fact that coalescence derives from a relativistic Bethe-Salpeter equation, and recall how effective quantum mechanics controls the dynamics of cluster particles that are nonrelativistic in the cluster centre of mass frame. We demonstrate that the coalescence--correlation relation is roughly consistent with the observed cluster spectra in systems ranging from PbPb to pPb and pp collisions. Paying special attention to nuclear wave functions, we derive the coalescence prediction for hypertriton and show that it, too, is roughly consistent with the data. Our work motivates a combined experimental programme addressing femtoscopy and cluster production under a unified framework. Upcoming pp, pPb and peripheral PbPb data analysed within such a programme could stringently test coalescence as the origin of clusters.

Branching fractions of Bc+ decays to two vector charm mesons

In this paper the decays of [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] have been investigated. The available experimental results for these decays are (in units of [Formula: see text]): [Formula: see text] By applying the theoretical value of the [Formula: see text] that span the range of [Formula: see text], the results for QCDF approach are about [Formula: see text] times smaller than experimental one. Therefore, it is decided to calculate the theoretical branching ratio by applying the final state interaction (FSI) through the [Formula: see text] (crossed and uncrossed) channels. The FSI effects are very sensitive to the changes in the phenomenological parameter [Formula: see text]. This parameter appears in the FSI form factors that increase strong interaction share. In most calculation changing two units in this parameter, makes the final result multiply in the branching ratio, therefore the decision to use FSI is not unexpected. In this study there are thirteen intermediate states for [Formula: see text] decay, fifteen intermediate states for [Formula: see text] decay and four intermediate states for [Formula: see text] and [Formula: see text] decays, in which the contribution of each one is calculated and summed in the final amplitude. Considering [Formula: see text] and fixing [Formula: see text] between four and five acceptable results have been obtained.

Evaluation of the decay by the factorization approaches and applying the effects of the final state interaction

In this paper the decay of meson which consists of two b and c heavy quarks, into the D0 and mesons is studied in two steps. In the first step, the QCD factorization (QCDF) approach is considered in the initial evaluation, the result of calculation is . While the available experimental result for this decay is , by applying the theoretical value of the that span the range of [0.4, 1.2]%, the result for QCDF approach becomes and the branching ratio in the experimental observation is obtained in the range of (3.72 ± 0.24) × 10−5 to (11.16 ± 0.72) × 10−5. Therefore, it is decided to calculate the theoretical branching ratio by applying the final state interaction (FSI) through the T and cross section channels. In this process, before the meson decays into two final state mesons of , it first decays into two intermediate mesons like , then these two mesons transform into two final mesons by exchanging another meson like D0. The FSI effects are very sensitive to the changes in the phenomenological parameter which appear in the form factor relation. In most calculations, changing two units in this parameter, makes the final result multiplied in the branching ratio, therefor the decision to use FSI is not unexpected. In this study there are nineteen intermediate states in which the contribution of each one is calculated and summed in the final amplitude. Considering , the numerical value of the is from (0.47 ± 0.08) × 10−7 to (13.98 ± 2.08) × 10−7 for which obtained by entering the FSI effects (η = 1 ∼ 3). It should be noted that by choosing the value of the η according to the mass of the exchange meson, as η = 3 for exchange meson of (or D) and η = 1 for exchange meson of (or K) the obtained result is , that is in very good agreement with the experimental result.

Femtoscopy with Identified Charged Particles for the NICA Energy Range

The correlation femtoscopy allows one to measure the space-time characteristics of particle production processes due to the effects of quantum statistics (QS) and final state interactions (FSI). Femtoscopy at lower energies was intensively studied at AGS, SPS and in the Beam Energy Scan (BES) program at RHIC. In the work we discuss possibilities to observe a difference from the first-order phase transition expected, according some theoretical predictions, at low energies and the crossover one, to be occurred at high energies, with the femtoscopy observables using the hybrid model vHLLE + UrQMD. The possibilities to use kaon femtoscopy complementary to the usually used pion one are discussed.

High-Statistics Measurement of Neutrino Quasielasticlike Scattering at 6GeV on a Hydrocarbon Target.

We measure neutrino charged-current quasielasticlike scattering on hydrocarbon at high statistics using the wideband Neutrinos at the Main Injector beam with neutrino energy peaked at 6GeV. The double-differential cross section is reported in terms of muon longitudinal (p_{∥}) and transverse (p_{⊥}) momentum. Cross section contours versus lepton momentum components are approximately described by a conventional generator-based simulation, however, discrepancies are observed for transverse momenta above 0.5 GeV/c for longitudinal momentum ranges 3-5 and 9-20 GeV/c. The single differential cross section versus momentum transfer squared (dσ/dQ_{QE}^{2}) is measured over a four-decade range of Q^{2} that extends to 10 GeV^{2}. The cross section turnover and falloff in the Q^{2} range 0.3-10 GeV^{2} is not fully reproduced by generator predictions that rely on dipole form factors. Our measurement probes the axial-vector content of the hadronic current and complements the electromagnetic form factor data obtained using electron-nucleon elastic scattering. These results help oscillation experiments because they probe the importance of various correlations and final-state interaction effects within the nucleus, which have different effects on the visible energy in detectors.

Investigating the effects of the phenomenological parameters changes in the final state interaction

In this research, the decay of is studied in two stages. In the first step, the QCD factorization (QCDF) approach is considered in the initial evaluation, the result of calculation is . While the available experimental result for this decay is , by applying the theoretical value of the that span the range of [0.9, 8.0]%, the result for QCDF approach becomes ) ** → = and the branching ratio in the experimental observation is obtained in the range of 2.57%–29.76% which is a large range. Therefore, it is decided to calculate the theoretical branch ratio by applying the effects of the final state interaction (FSI) through only possible cross section channel. In this process, before the meson decays into two final mesons, , first, it decays into two intermediate mesons (as ), then these two intermediate mesons are converted into two final mesons by the exchange of another meson, (such as K+ corresponding to ). The FSI effects are highly sensitive to the phenomenological parameters that appear in the form factor relationship, so that in most calculations, change the three units in the numeric value of this parameter changes the final result ten times. Therefore, the decision to use FSI is not unexpected. In this study, there are four intermediate states in the cross section channel in which the amplitude of each of them are calculated separately and included in the final amplitude. Considering , the numerical value of the is from (1.54 ± 0.20) × 10−3 to (2.89 ± 0.41) × 10−3 for which obtained by entering the QCDF approach and FSI effects (η = 0.5–1.5). It should be noted that by choosing the value of the η according to the mass of the exchange meson, as η = 1.5 for exchange meson of B* (or B) and η = 0.5 for exchange meson of K* (or K) the obtained result is , that is in very good agreement with the experimental result.

Near-threshold incoherent pion photoproduction on the deuteron with final-state interaction effects

Incoherent pion photoproduction on the deuteron γd→πNN is investigated in the energy region Eγthr≤Eγ≤ 160 MeV. The model applied contains the amplitudes of the impulse approximation as well as the NN and πN rescattering in the final state. For the elementary γN→πN amplitude, the unitary isobar MAID-2007 model is used. This model is parameterized in terms of invariant amplitudes and allows one to give a more reliable description of the threshold region. The half-off-shell NN and πN scattering amplitudes are obtained from separable representations of realistic NN and πN interactions, respectively. For the first time, numerical results for the linear photon asymmetry Σ, vector T11 and tensor T2M (M=0,1,2) deuteron spin asymmetries for the reactions γd→π−pp, γd→π+nn, and γd→π0np are presented. In addition, results for the unpolarized differential and total cross sections are given. We found that the influence of NN rescattering is moderate in both charged-and neutral-pion production channels, whereas πN rescattering is almost negligible in the charged-pion production channels which is not the case in neutral-pion production since a noticeable contribution is obtained. The calculated results for unpolarized differential and total cross sections are compared with the available experimental data and other theoretical models, and a satisfactory agreement is obtained.

Effects of final state interaction in B^+_c to D^0 K^+ decay

Effects of final state interaction in B^+_c to D^0 K^+ decay

Nuclear transparency in Monte Carlo neutrino event generators

Hadron cascade model is an essential part of Monte Carlo neutrino event generators that governs final state interactions of knocked-out nucleons and produced pions. It is shown that such model enriched with physically motivated modifications of nucleon-nucleon cross section and incorporation of nuclear correlation effects is able to reproduce experimental nuclear transparency data. Uncertainty of nucleon final state interactions effects is estimated and applied to recent neutrino-nucleus cross section measurements that include an outgoing proton in the experimental signal. Conclusions are drawn on a perspective of identification of events that originate from two-body current mechanism.

Quasi-elastic polarization-transfer measurements on the deuteron in anti-parallel kinematics

We present measurements of the polarization-transfer components in the H2(e→,e′p→) reaction, covering a previously unexplored kinematic region with large positive (anti-parallel) missing momentum, pmiss, up to 220MeV/c, and Q2=0.65(GeV/c)2. These measurements, performed at the Mainz Microtron (MAMI), were motivated by theoretical calculations which predict small final-state interaction (FSI) effects in these kinematics, making them favorable for searching for medium modifications of bound nucleons in nuclei. We find in this kinematic region that the measured polarization-transfer components Px and Pz and their ratio agree with the theoretical calculations, which use free-proton form factors. Using this, we establish upper limits on possible medium effects that modify the bound proton's form factor ratio GE/GM at the level of a few percent. We also compare the measured polarization-transfer components and their ratio for 2H to those of a free (moving) proton. We find that the universal behavior of 2H, 4He and 12C in the double ratio (Px/Pz)A(Px/Pz)H1 is maintained in the positive missing-momentum region.