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Differential cross sections for elastic pion scattering on a number of nuclei at energies between 130 and 290 MeV are calculated. For this purpose, use is made of a microscopic optical pion-nucleus potential that was obtained on the basis of the Glauber theory of high-energy scattering and which is determined by the density distribution of pointlike target nucleons and by the pion-nucleon scattering amplitude. The calculation of the cross sections in question is based on solving the respective relativistic wave equation. Three parameters of the pion-nucleon amplitude are fitted in performing a comparison with experimental data. These are the total cross section for pion-nucleon scattering, the ratio of the real to the imaginary part of the forward pion-nucleon scattering amplitude, and the slope parameter. The resulting values of these parameters are then compared with their counterparts for scattering on free nucleons. The character of nuclear-matter-induced changes in these parameters is studied. [ABSTRACT FROM AUTHOR]

Using one- and two-body density matrices, we calculate the spatial and momentum distributions, two-particle Hanbury-Brown-Twiss (HBT) correlation functions, and the chaotic parameter λ in HBT interferometry for the systems of boson gas within the harmonic oscillator potentials with anisotropic frequencies in transverse and longitudinal directions. The HBT chaotic parameter, which can be obtained by measuring the correlation functions at zero relative momentum of the particle pair, is related to the degree of Bose-Einstein condensation and thus the system environment. We investigate the effects of system temperature, particle number and the average momentum of the particle pair on the chaotic parameter. The value of λ decreases with the condensed fraction, f0. It is one for f0 = 0 and zero for f0 = 1. For a certain f0 between 0 and 1, we find that λ increases with the average momentum of the particle pair and decreases with the particle number of system. The results of λ are sensitive to the ratio, ν = ωz/ωρ, of the frequencies in longitudinal and transverse directions. They are smaller for larger ν when ωρ is fixed. In the heavy-ion collisions at the Large Hadron Collider (LHC) energy the large identical pion multiplicity may possibly lead to a considerable Bose-Einstein condensation. Its effect on the chaotic parameter in two-pion interferometry is worth considering in earnest. [ABSTRACT FROM AUTHOR]

The D03 dibaryon is generated dynamically as a resonance pole in a πNΔ' three body model, where Δ' is a stable Δ baryon. Using separable interactions dominated by the Δ(1232) isobar for pN and by the D12(2150) isobar for NΔ', with D12(2150) the NΔ dibaryon deduced in and constrained by ¹D2 pp scattering, the model reduces to an effective two body problem for ΔΔ' which is solved. The mass and width of D03 are found close to those of the I(JP)=0(3+) resonance peak observed by WASA-at-COSY in pion-production pn collisions at 2.37 GeV. [ABSTRACT FROM AUTHOR]

A novel method is employed to compute the pion electromagnetic form factor, Fπ(Q2), on the entire domain of spacelike momentum transfer using the Dyson-Schwinger equation (DSE) framework in QCD. The DSE architecture unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA). Using this PDA, the leading-order, leading-twist perturbative QCD result for Q2 Fπ(Q2) underestimates the full computation by just 15% on Q2 ≳ 8 GeV2, in stark contrast to the result obtained using the asymptotic PDA. The analysis shows that hard contributions to the pion form factor dominate for Q2 ≳ 8 GeV2, but, even so, the magnitude of Q2Fπ(Q2) reflects the scale of dynamical chiral symmetry breaking, a pivotal emergent phenomenon in the standard model. [ABSTRACT FROM AUTHOR]

A method is explained through which a pointwise accurate approximation to the pion's valence-quark distribution amplitude (PDA) may be obtained from a limited number of moments. In connection with the single nontrivial moment accessible in contemporary simulations of lattice-regularized QCD, the method yields a PDA that is a broad concave function whose pointwise form agrees with that predicted by Dyson-Schwinger equation analyses of the pion. Under leading-order evolution, the PDA remains broad to energy scales in excess of 100 GeV, a feature which signals persistence of the influence of dynamical chiral symmetry breaking. Consequently, the asymptotic distribution φπasy(x) is a poor approximation to the pion's PDA at all such scales that are either currently accessible or foreseeable in experiments on pion elastic and transition form factors. Thus, related expectations based on φπasy(x) should be revised. [ABSTRACT FROM AUTHOR]

The multichannel S- and P-wave amplitudes for the ππ scattering, constructed requiring analyticity and unitarity of the S-matrix and using the uniformization procedure, are elaborated using the dispersion relations with imposed crossing symmetry condition. The amplitudes are modified in the low-energy region to improve their consistency with experimental data and the dispersion relations. Agreement with data is achieved for both amplitudes from the threshold up to 1.8 GeV and with dispersion relations up to 1.1 GeV. Consequences of the applied modifications, e.g. changes of the S-wave lowest-pole positions, are presented. [ABSTRACT FROM AUTHOR]

We study DD̅ * (D*D̅ ) scattering in the framework of unitarized heavy meson chiral perturbation theory with pion exchange and a contact interaction. 3S1-3D1 mixing effects are taken into account. A loosely bound state X(3872), with the pole position being Mpole=(3871.70-i0.39)  MeV, is found. The result is not sensitive to the strength of the contact interaction. Our calculation provides a theoretical confirmation of the existence of the 1++ state X(3872). The light quark mass dependence of the pole position indicates it has a predominately DD̅ * (D*D̅ ) molecular nature. When the π mass is larger than 142 MeV, the pole disappears, which makes impossible the lattice simulation of this state at large quark mass. [ABSTRACT FROM AUTHOR]

The study of the neutral current elastic scattering of neutrinos on protons at lower energies can be used as a compelling probe to improve our knowledge of the strangeness of the proton. We consider a neutrino beam generated from pion decay at rest, as provided by a cyclotron or a spallation neutron source and a 1 kton scintillating detector with a potential similar to the Borexino detector. Despite several backgrounds from solar and radioactive sources, it is possible to estimate two optimal energy windows for the analysis, one between 0.65 and 1.1 MeV and another between 1.73 and 2.2 MeV. The expected number of neutral current events in these two regions, for an exposure of 1 yr, is enough to obtain an error on the strange axial charge 10 times smaller than available at present. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the feasibility of studying in-medium properties of the ω meson in photoproduction experiments via the decay . We use the GiBUU transport model to compare different methods of obtaining in-medium information, such as the invariant mass spectrum, transparency ratio, excitation function and momentum spectrum. We show that the final-state interaction of the pion poses a major obstacle for the interpretation of the invariant mass spectrum. The other three observables turn out to be fairly independent of final-state interactions and thus, taken together, can give access to the ωʼs in-medium properties. [Copyright &y& Elsevier]

We re-examine one-pion exchange as a possible binding mechanism in the X (3872) charmonium-like state and argue it to be not sufficiently binding for this purpose. We conclude therefore that other short-range dynamics are responsible for the X formation. [ABSTRACT FROM AUTHOR]

An analysis of $${B^\pm \to \pi^\pm \pi^\mp \pi^\pm}$$ decay data in a quasi two-body B → π [ π π] QCD factorization framework is performed. The short distance amplitudes are calculated including next-to-leading order in α vertex and penguin corrections. The long distance amplitudes due to the [ π π] final state interactions are described by the pion non-strange scalar and vector form factors for the [ π π] S-wave state and [ π π] P-wave state, respectively and by a relativistic Breit-Wigner formula for the[ π π] D-wave state. We achieve a good fit of the data with only three parameters for the S wave, one for the P wave and one for the D wave. Our model gives a unified unitary description of the three scalar resonances, f(600), f(980) and f(1400) in terms of the pion scalar form factor. We predict for the B to f(1270) transition form factor, $${F^{Bf_2}(m_\pi^2)=0.098\pm0.007}$$ . [ABSTRACT FROM AUTHOR]

Abstract: We extend the usual chiral perturbation theory framework (χPT) to allow the inclusion of a light dynamical isosinglet scalar. Using lattice QCD results, and a few phenomenological inputs, we explore the parameter space of the effective theory. We discuss the S-wave pion–pion scattering lengths, extract the average value of the two light quark masses and evaluate the impact of the dynamical singlet field in the low-energy constants , and of χPT. We also show how to extract the mass and width of the sigma resonance from chiral extrapolations of lattice QCD data. [Copyright &y& Elsevier]

Abstract: We study the correlation among impact parameter, multiplicity and longitudinal rapidity of neutral and charged pions, protons and neutrons produced in the interactions of charged pions with xenon nuclei at momenta of 2.34, 3.5, 9 and 30GeV/c. The correlation is investigated using a JAM modeling code. [Copyright &y& Elsevier]

Comparisons of predictions from two simple event generators followed by a rescattering model are made with pion interferometry data from the STAR experiment. The systematics with impact parameter, pair momentum and azimuthal angle are presented and a general agreement with all main trends in the data is demonstrated; however, the experimentally observed approach of the three radius values toward a common value at the highest pair momenta is not found for the model values. In addition, an analysis of source times as derived from the interferometry analysis is presented and a quantitative estimate of the model freeze-out duration times is presented. [ABSTRACT FROM AUTHOR]

The search for genuine two-particle dynamical correlations among the pions produced in 16O-AgBr interactions at 60 AGeV and 32S-AgBr interactions at 200 AGeV (super proton synchrotron data) has been carried out by the method of normalized factorial cumulant moments in pseudo-rapidity (η), azimuthal angle (ϕ) and two-dimensional anisotropic (η-ϕ) phase space. The analysis reveals the presence of genuine two-particle dynamical correlations among the pions in 16O-AgBr and 32S-AgBr interactions in both one and two dimensions. Stronger correlation has been observed in higher dimensional space. Correlations between the pions are found to decrease with the increase of projectile mass and energy. Experimental results have been compared with the FRITIOF data sample in the pseudo-rapidity space. In azimuthal angle space, events simulated by generating random numbers (Monte Carlo Simulation) have been used for the purpose of comparison. The FRITIOF data and the data of the simulated interactions have failed to reproduce the experimental results. The experimental results have also been compared with the event sample generated by the UrQMD model in both pseudo-rapidity and azimuthal angle space. Like the FRITIOF model, the UrQMD model is also unable to replicate the experimental results. The variation of normalized cumulant moment (K2) against the number of bin M has been fitted with a function K2 = aMb in both one and two dimensions. No fitting of this kind has been possible in the case of the FRITIOF data, UrQMD data and the MC simulated data. [ABSTRACT FROM AUTHOR]

We study the three-pion decays of the lightest isoscalar vector mesons, ω and ɸ, in a dispersive framework that allows for a consistent description of final-state interactions between all three pions. Our results are solely dependent on the phenomenological input for the pion-pion P-wave scattering phase shift. We predict the Dalitz plot distributions for both decays and compare our findings to recent measurements of the ɸ→3π Dalitz plot by the KLOE and CMD-2 collaborations. Dalitz plot parameters for future precision measurements of ω→3π are predicted. We also calculate the ππ P-wave inelasticity contribution from ωπ intermediate states. [ABSTRACT FROM AUTHOR]

We study CP violation and the contribution of the strong pion-pion interactions in the three-body B± → π ± π … π ± decays within a quasi two-body QCD factorization approach. The short distance interaction amplitude is calculated in the next-to-leading order in the strong coupling constant with vertex and penguin corrections. The meson-meson final state interactions are described by pion non-strange scalar and vector form factors for the S and P waves and by a relativistic Breit-Wigner formula for the D wave. The pion scalar form factor is calculated from a unitary relativistic coupled-channel model including ππ, KK̄ and effective (2π)(2π) interactions. The pion vector form factor results from a Belle Collaboration analysis of Τ̅ → pi; ̅π0VΤ data. The recent B± → π ± π … π ± BABAR Collaboration data are fitted with our model using only three parameters for the S wave, one for the P wave and one for the D wave. We find not only a sizable contribution of the S wave just above the π π threshold but also under the ρ(770) peak a significant interference, mainly between the S and P waves. For the B to f2(1270) transition form factor, we predict FBf2 (m Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. ) = 0:098 ± 0:007. Our model yields a unified unitary description of the contribution of the three scalar resonances f0(600), f0(980) and f0(1400) in terms of the pion non-strange scalar form factor. [ABSTRACT FROM AUTHOR]

In high-energy heavy ion collisions a hot and dense medium is formed, where the UA(1) or chiral symmetry may temporarily be restored. As a consequence, the mass of the η′(958) mesons may be reduced to its quark model value, and the abundance of η′ mesons at low pT may be enhanced by more than a factor of 10. The intercept parameter λ* of the charged pion Bose Einstein correlations provides a sensitive observable of the possibly enhanced η′ abundance. We have analyzed λ*(mT) data from √sNN=200 GeV central Au+Au reactions measured at the BNL Relativistic Heavy Ion Collider (RHIC), using extensive Monte Carlo simulations based on six popular models for hadronic multiplicities. Based on the combined STAR and PHENIX data set, and on various systematic investigations of resonance multiplicities and model parameters, we conclude that in √sNN=200 GeV central Au+Au reactions the mass of the η′ meson is reduced by Δmη′*>200 MeV, at the 99.9% confidence level in the considered model class. Such a significant η′ mass modification may indicate the restoration of the UA(1) symmetry in a hot and dense hadronic matter and the return of the ninth "prodigal" Goldstone boson. A similar analysis of NA44 S+Pb data at top CERN Super Proton Synchroton (SPS) energies showed no significant in-medium η′ mass modification. [ABSTRACT FROM AUTHOR]