Two-pion exchange contribution to proton-proton scattering at medium energies

Gibbs, W. R.; Loiseau, B.

doi:10.1103/physrevc.77.014003

“…We utilize a dipole form for the pion-nucleon form factor ∼1=ð1 þ Q 2 =m 2 A Þ 2 , where m A ∼ 1 GeV is the axial mass [72,73], and similarly the proton electromagnetic form factor F 1 ðQ 2 Þ ∼ 1=ð1 þ Q 2 =ð0.71 GeVÞ 2 Þ 2 . The contribution from one-pion exchange is significant in a narrow energy range, and it is known that additional processes, such as twopion exchange, become important for beam momenta above 600-700 MeV [74,75]. Retaining just the one-pion exchange contribution will nonetheless be sufficient in our case, as we are interested in the ratio of two-to three-body final states, in which the overall normalization of the pp cross section drops out as for the splitting function calculation above.…”

Section: One-pion Exchangementioning

confidence: 99%

LSND constraints on the Higgs portal

Foroughi-Abari

¹

,

Ritz

²

2020

View full text Add to dashboard Cite

High-luminosity fixed target experiments provide impressive sensitivity to new light weakly coupled degrees of freedom. We revisit the minimal case of a scalar singlet S coupled to the Standard Model through the Higgs portal that decays visibly to leptons for scalar masses below the dipion threshold. The dataset from the LSND experiment is found to impose the leading constraints within two mass windows between m S ∼ 100 and 350 MeV. In the process, we analyze a number of scalar production channels in the target, finding that proton bremsstrahlung provides the dominant channel at LSND beam energies.

show abstract

“…which is the analogue of (3.52), both already discussed in Sec. 2 Note that Gibbs and Loiseau [110] introduced a similar set of amplitudes, but following Ref. [5], they used unit vectors { , m } which are rotated by 45 • as compared to our { , m} for the scattered particle, so that their amplitudes are the same (a = a, etc.…”

Section: This Implies the Identitymentioning

confidence: 99%

Spin observables and spin structure functions: inequalities and dynamics

Artru,

Elchikh,

Richard

et al. 2008

Preprint

View full text Add to dashboard Cite

Model-independent identities and inequalities which relate the various spin observables of collisions in nuclear and particle physics are reviewed in a unified formalism. Their physical interpretation and their implications for dynamical models are also discussed. These constraints between observables can be obtained in several ways: from the explicit expression of the observables in terms of a set of helicity or transversity amplitudes, a non-trivial algebraic exercise which can be preceded by numerical simulation with randomly chosen amplitudes, from anticommutation relations, or from the requirement that any polarisation vector is less than unity. The most powerful tool is the positivity of the density matrices describing the spins in the initial or final state of the reaction or its crossed channels. The inequalities resulting from positivity need to be projected to single out correlations between two or three observables. The quantum aspects of the information carried by spins, in particular entanglement, are considered when deriving and discussing the constraints Several examples are given, with a comparison with experimental data in some cases. For the exclusive reactions, the cases of the strangeness-exchange proton-antiproton scattering and the photoproduction of pseudoscalar mesons are treated in some detail: all triples of observables are constrained, and new results are presented for the allowed domains. The positivity constraints for total cross-sections and for the simplest observables of single-particle inclusive reactions are reviewed. They also apply to spin-dependent structure functions and parton distributions, both integrated or transverse-momentum dependent. The corresponding inequalities are shown to be preserved by the evolution equations of quantum chromodynamics.

show abstract

“…2 Note that Gibbs and Loiseau [110] introduced a similar set of amplitudes, but following Ref. [5], they used unit vectors { , m } which are rotated by 45…”

mentioning

confidence: 99%

Spin observables and spin structure functions: Inequalities and dynamics

Artru

¹

,

Elchikh

²

,

Richard

³

et al. 2009

View full text Add to dashboard Cite

Model-independent identities and inequalities which relate the various spin observables of collisions in nuclear and particle physics are reviewed in a unified formalism. Their physical interpretation and their implications for dynamical models are also discussed. These constraints between observables can be obtained in several ways: from the explicit expression of the observables in terms of a set of helicity or transversity amplitudes, a non-trivial algebraic exercise which can be preceded by numerical simulation with randomly chosen amplitudes, from anticommutation relations, or from the requirement that any polarisation vector is less than unity. The most powerful tool is the positivity of the density matrices describing the spins in the initial or final state of the reaction or its crossed channels. The inequalities resulting from positivity need to be projected to single out correlations between two or three observables. The quantum aspects of the information carried by spins, in particular entanglement, are considered when deriving and discussing the constraints Several examples are given, with a comparison with experimental data in some cases. For the exclusive reactions, the cases of the strangeness-exchange proton-antiproton scattering and the photoproduction of pseudoscalar mesons are treated in some detail: all triples of observables are constrained, and new results are presented for the allowed domains. The positivity constraints for total cross-sections and for the simplest observables of single-particle inclusive reactions are reviewed. They also apply to spin-dependent structure functions and parton distributions, both integrated or transverse-momentum dependent. The corresponding inequalities are shown to be preserved by the evolution equations of quantum chromodynamics.Inequalities on spin observables 3

show abstract

Two-pion exchange contribution to proton-proton scattering at medium energies

Cited by 3 publications

References 84 publications

LSND constraints on the Higgs portal

LSND constraints on the Higgs portal

Spin observables and spin structure functions: inequalities and dynamics

Spin observables and spin structure functions: Inequalities and dynamics

Contact Info

Product

Resources

About