Polarization phenomena in open charm photoproduction processes

Tomasi–Gustafsson, E.; Rekalo, M.P.

doi:10.1103/physrevd.69.094015

Cited by 4 publications

(3 citation statements)

References 66 publications

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“…[25,26]; polarization effects in open charm photo-production were considered in Ref. [27]; propagation of charmed hadrons in the nuclear medium were analyzed in Refs. [28,29,30]; open charm production in relativistic nucleus-nucleus collisions at wide energy region was analyzed in Ref.…”

Section: Introductionmentioning

confidence: 99%

Exclusive charm production inp¯pcollisions ats≲15GeV

Титов

Kämpfer

2008

Phys. Rev. C

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We discuss the open charm production in peripheral reactionspp →Ȳ c Y c andpp → M cMc , where Y c and M c stand for Λ + c , Σ + c and D, D * , respectively, at √ s 15 GeV, which corresponds to the energy range of FAIR. Our consideration is based on the topological decomposition of the planar quark and diquark diagrams which allows to estimate consistently meson and baryon exchange trajectories and energy scale parameters as well. The spin dependance is determined by the effective interaction of lowest exchanged resonance. Unknown parameters are fixed by an independent analysis of open strangeness production inpp →Ȳ Y andpp →KK reactions and of SU(4) symmetry. We present the corresponding cross sections and longitudinal double-spin asymmetries for exclusive binary reactions with open charm mesons and baryons in the final state. The polarization observables have a non-trivial t and s dependence which is sensitive to details of the open charm production mechanism.

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Section: Introductionmentioning

confidence: 99%

Exclusive charm production inp¯pcollisions ats≲15GeV

Титов

Kämpfer

2008

Phys. Rev. C

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“…for any E γ and cos θ (θ is the K meson production angle). The following model independent relation holds between polarization observables in any reaction γ + N → M + B(1/2 ± ) [17]:…”

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Model-independent methods to measure theP-parity of the ⁺-pentaquark in photo-production experiments

Rekalo¹,

Tomasi–Gustafsson²

2004

J. Phys. G: Nucl. Part. Phys.

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We discuss model independent methods to measure the P -parity of the Θ + -pentaquark, in the simplest processes of photoproduction, γ + N → K + Θ + , using definite relations between T-even polarization observables, which depend on the P -parity of the Θ + baryon (with respect to the N K system). One method, which holds for any photon energy and any K meson production angle, is based on the relation between the Σ B asymmetry (induced by a linearly polarized photon beam, with unpolarized target) and the D nn component of the depolarization tensor (for unpolarized photon beam). Another method, which applies in collinear kinematics (or in threshold conditions), is related to the sign of the D nn component, with linearly polarized photon beam. PACS numbers: 25.20.Lj,21.10.Hw,13.88.+e 1 The experimental determination of the P -parity of the Θ + -pentaquark is important for the understanding of the underlying structure of this resonance [1, 2, 3,4,5,6,7,8], therefore, several suggestions concerning different processes, have been recently proposed in the literature [9].The simplest photoproduction reaction of the Θ + -baryon, γ + N → K + Θ + , is in principle interesting for the determination of the Θ + parity: all the observables (the differential cross section and the polarization effects) depend of course on the P -parity. However different models give different predictions on the angular and E γ behavior of the observables.Presently, the choice of a reliable model for the considered reaction is extremely difficultdue to the absence of the necessary experimental information: too much freedom is left in building a model, from the choice of an adequate approach to the knowledge of necessary coupling constants and phenomenological form factors. In this way, the determination of the P-parity would be ambiguous, because model dependent.A similar example is given by photo-end electro-production of strange particles, where a wide number of different models give a comparable description of the available data. Different reaction mechanisms with many unknown parameters and constants (to be determined from the data), have been suggested, but their predictive power is quite poor, and any new experimental information require, as a rule, to update the fitting procedure [10].One can note that, in the first studies on photo-end electro-production of strange particles, both possibilities on the K-meson P -parity, P (K) = ±1, were systematically considered in the theoretical analysis [11]. Later on, many data on γ + N → K + Y and e − + N → e − + K + Y , (Y = Λ or Σ hyperon) were collected. Their phenomenological interpretation relies on the negative P -parity of the K meson (or, more exactly, the relative P -parity with respect to the NY system). There is a so large arbitrariness in the theoretical approaches, that it is, a priori, commonly assumed, for simplicity, that the K meson P parity is negative. Following the quark model, the K meson is considered to be a pseudoscalar particle. But, in our opinion, the existing data and mod...

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“…Large isotopic effects are an expected property of ELA approach, because the relative values of s, u, and t-channel contributions are different for the different channels. Large isotopic effects are especially visible in the cos 0-distributions for all these observables [7]. 2.…”

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confidence: 96%

Associative open charm photoproduction $$\gamma + N \to Y_c + \bar D_c (\bar D_c^ * ), Y_c = \Lambda _c^ + or \Sigma _c $$

Tomasi–Gustafsson

2005

Czech J Phys

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We analyze polarization effects in associative photoproduction of pseudoscalar (D~_) and vector (D:) charmed mesons in exclusive processes 7 + N --, Y~ + De, Y~ = A +, ~. We calculate the differential cross section and all polarization observables in framework of an effective Lagrangian approach. In case of collinear kinematics it is possible to give model independent predictions for polarization observables in case of D~ production, and the analysis for D: is largely simplified.Photoproduction of charmed particles on nucleons has been studied since more than twenty years, mostly through inclusive reactions, in the photon energy range E~ = 20-70 GeV, i.e. far from the threshold region. The production mechanism usually assumed is the photon-gluon fusion mechanism (PGF), "~ + G -~ c + ~ [1], and, in this frame, Dc and D: production are related to the gluon content of the nucleon: polarized reactions are a tool to measure the spill content of tile nucleon which is carried by the gluons.However, the calculation of the properties of the produced charmed inesons and baryons produced from PGF is not straightforward, as it involves assumptions on the hadronization process and the knowledge of fragmentation functions. Whereas it is possible to reproduce the inclusive cross section, the particle/antiparticle ratio, observed in the experiments, in particular near threshold, cannot be reproduced by PGF.In principle, other mechanisms (of non-perturbative nature) should also be taken into account, such as, for example, tile diffractive production of Dc--Dc or AcDc pairs, through Pomeron exchange. Different hadronic exchanges can also occur [2]. We discuss here the simplest two body reactions -y + N ~ Yc + Dc (Dc), among _---0 which the reaction 3' + P --* A + + Dc has the lowest threshold (Ethr = 8.9 GeV).The differential cross section and the polarization observables for these processes can be calculated in terms of hadronic exchanges in s, t and u channels. The effect, ive Lagrangian approach gives a very convenient frame for this study, since all the observables can be calculated with the help of few parameters, which have a definite physical meaning.

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Polarization phenomena in open charm photoproduction processes

Cited by 4 publications

References 66 publications

Exclusive charm production inp¯pcollisions ats≲15GeV

Exclusive charm production inp¯pcollisions ats≲15GeV

Model-independent methods to measure theP-parity of the ⁺-pentaquark in photo-production experiments

Associative open charm photoproduction $$\gamma + N \to Y_c + \bar D_c (\bar D_c^ * ), Y_c = \Lambda _c^ + or \Sigma _c $$

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Polarization phenomena in open charm photoproduction processes

Cited by 4 publications

References 66 publications

Exclusive charm production inp¯pcollisions ats≲15GeV

Exclusive charm production inp¯pcollisions ats≲15GeV

Model-independent methods to measure theP-parity of the +-pentaquark in photo-production experiments

Associative open charm photoproduction $$\gamma + N \to Y_c + \bar D_c (\bar D_c^ * ), Y_c = \Lambda _c^ + or \Sigma _c $$

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Model-independent methods to measure theP-parity of the ⁺-pentaquark in photo-production experiments