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J. Haidenbauer

Publications and source records attributed to J. Haidenbauer.

At least 91 records · Page 5Linked to original sources
arXiv2009

Measurement of the Spin-Dependence of the pbar-p Interaction at the AD-Ring

We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determine for the first time the two total spin-dependent pbar-p cross sections sigma_1 and sigma_2 at antiproton beam energies in the range from 50 to 450 MeV. The data obtained are of interest by themselves for the general theory of pbar-p interactions since they will provide a first experimental constraint of the spin-spin dependence of the nucleon-antinucleon potential in the energy range of interest. In addition, measurements of the polarization buildup of stored antiprotons are required to define the optimum parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to feed a double-polarized asymmetric pbar-p collider with polarized antiprotons. Such a machine has recently been proposed by the PAX collaboration for the new Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, Germany. The availability of an intense stored beam of polarized antiprotons will provide access to a wealth of single- and double-spin observables, thereby opening a new window on QCD spin physics.

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arXiv2009

Neutral pion photoproduction at high energies

A Regge model with absorptive corrections is employed in a global analysis of the world data on the reactions gamma p -> pi0 p and gamma n -> pi0 n for photon energies from 3 to 18 GeV. In this region resonance contributions are expected to be negligible so that the available experimental information on differential cross sections and single- and double polarization observables at -t < 2 GeV^2 allows us to determine the non-resonant part of the reaction amplitude reliably. The model amplitude is then used to predict observables for photon energies below 3 GeV. A detailed comparison with recent data from the CLAS and CB-ELSA Collaborations in that energy region is presented. Furthermore, the prospects for determining the pi0 radiative decay width via the Primakoff effect from the reaction gamma p -> pi0 p are explored.

hep-ph↗
arXiv2009

Backward pion photoproduction

We present a systematic analysis of backward pion photoproduction for the reactions gamma p -> pi0 p and gamma p -> pi+ n. Regge phenomenology is applied at invariant collision energies above 3 GeV in order to fix the reaction amplitude. A comparision with older data on pi0- and pi+ photoproduction at theta = 180 degrees indicates that the high-energy limit as given by the Regge calculation could be reached possibly at energies of around sqrt{s} = 3 GeV. In the energy region of sqrt{s} < 2.5 GeV, covered by the new measurements of gamma p -> pi0 p differential cross sections at large angles at ELSA, JLab, and LEPS, we see no clear signal for a convergence towards the Regge results. The baryon trajectories obtained in our analysis are in good agreement with those given by the spectrum of excited baryons.

hep-ph↗
arXiv2009

Forward antiproton-deuteron elastic scattering and total spin-dependent antiproton-deuteron cross sections at intermediate energies

Spin-dependent total pbar-d cross sections are considered using the optical theorem. For this aim the full spin dependence of the forward pbar-d elastic scattering amplitude is considered in a model independent way. The single-scattering approximation is used to relate this amplitude to the elementary amplitudes of pbar-p and pbar-n scattering and the deuteron form factor. A formalism allowing to take into account Coulomb-nuclear interference effects in polarized pbar-d cross sections is developed. Numerical calculations for the polarized total pbar-d cross sections are performed at beam energies 20-300 MeV using the Nbar-N interaction models developed by the Julich group. Double-scattering effects are estimated within the Glauber approach and found to be in the order of 10-20%. Existing experimental data on differential pbar-d cross sections are in good agreement with the performed Glauber calculations. It is found that for the used Nbar-N models the total longitudinal and transversal pbar-d cross sections are comparable in absolute value to those for pbar-p scattering.

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arXiv2008

Comment on "Once more about the KK molecule approach to the light scalars"

In this manuscript we comment on the criticism raised recently by Achasov and Kiselev [Phys. Rev. D 76, 077501 (2007)] on our work on the radiative decays phi to gamma a_0/f_0 [Eur. Phys. J. A 24, 437 (2005)]. Specifically, we demonstrate that their criticism relies on results that violate gauge-invariance and is therefore invalid.

hep-ph↗
arXiv2008

Pion-nucleon charge-exchange amplitudes above 2 GeV

The amplitudes for the pion-nucleon charge exchange reaction of the Karlsruhe-Helsinki and the George-Washington-University partial wave analyses are compared with those of a Regge-cut model with the aim to explore the possibility to provide high energy constraints for theoretical baryon resonance analyses in the energy region above 2 GeV.

hep-ph↗
arXiv2008

Near threshold ppbar enhancement in the J/psi -> omega ppbar decay

The near-threshold behavior of the ppbar invariant mass spectrum from the J/psi -> omega ppbar decay reported recently by the BES Collaboration is analyzed. Contrary to the statement made by the BES Collaboration itself our study demonstrates that there is indeed a noticeable enhancement in the ppbar invariant mass spectrum near threshold. Moreover, this enhancement is nicely reproduced by the final state interaction in the relevant 11S0 ppbar partial wave as given by the Julich nucleon--antinucleon model. Therefore, and again contrary to the statement by the BES Collaboration, their new data on J/psi -> omega ppbar decay in fact strongly support the FSI interpretation of the ppbar enhancement, seen also in other decay reactions.

hep-ph↗
arXiv2008

Charmed meson rescattering in the reaction pbar d to D Dbar N

We examine the possibility to extract information about the DN and DbarN interactions from the pbar d to D Dbar N reaction. We utilize the notion that the open-charm mesons are first produced in the annihilation of the antiproton on one nucleon in the deuteron and subsequently rescatter on the other (the spectator) nucleon. The latter process is then exploited for investigating the DN and DbarN interactions. We study different methods for isolating the contributions from the D^0p and D^-p rescattering terms.

hep-ph↗
arXiv2007

Pion--deuteron scattering length in Chiral Perturbation Theory up to order χ^{3/2}

A complete calculation of the corrections to pion-deuteron scattering length up to order $χ^{3/2}$ with $χ=m_π/M_{N}$ is performed. The calculation includes the dispersive contributions and corrections due to the explicit treatment of the $Δ$ resonance. s-wave pion-nucleon scattering parameters are extracted from a combined analysis of modern experimental data.

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arXiv2007

Progress in NN --> NNpi

We survey the recent developments in the reaction $NN \to NNπ$ in effective field theory. We show that the proper construction of the production operator needs a careful separation of irreducible pieces from reducible ones. The result of this consideration is a complete cancellation of all loops in the production operator at NLO. Moreover, we show that this procedure brings the leading Weinberg-Tomozawa vertex on-shell, thus enhancing the corresponding contribution to the transition amplitude by a factor of 4/3 as compared to the commonly used value. We also discuss the role of the $Δ(1232)$ for the s-wave pion production. Being relatively sizable individually the direct and rescattering mechanisms of the $Δ$ excitation at NLO cancel each other to a large extent. Thus, we conclude that the net effect of the $Δ$ at NLO is very small.

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arXiv2007

Regge approach to charged-pion photoproduction at invariant energies above 2 GeV

A Regge model with absorptive corrections is employed in a global analysis of the world data on positive and negative pion photoproduction for photon energies from 3 to 8 GeV. In this region resonance contributions are expected to be negligible so that the available experimental information on differential cross sections and single polarization observables at -t \leq 2 GeV^2 allows us to determine the non-resonant part of the reaction amplitude reliably. The model amplitude is then used to predict observables for photon energies below 3 GeV. Differences between our predictions and data in this energy region are systematically examined as possible signals for the presence of excited baryons. We find that the data available for the polarized photon asymmetry show promising resonance signatures at invariant energies around 2 GeV. With regard to differential cross sections the analysis of negative pion photoproduction data, obtained recently at JLab, indicates likewise the presence of resonance structures around 2 GeV

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arXiv2007

Role of the Delta(1232) in pion-deuteron scattering at threshold within chiral effective field theory

We investigate the role of the delta isobar in the reaction $πd\to πd$ at threshold in chiral effective field theory. We discuss the corresponding power counting and argue that this calculation completes the evaluation of diagrams up to the order (m_pi/M_N)^(3/2), with m_pi (M_N) for the pion (nucleon) mass. The net effect of all delta contributions at this order to the pion-deuteron scattering length is (2.4 +/- 0.4)x 10^(-3) m_pi^{-1}.

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arXiv2007

Strangeness S=-2 baryon-baryon interactions using chiral effective field theory

We derive the leading order strangeness S=-2 baryon-baryon interactions in chiral effective field theory. The potential consists of contact terms without derivatives and of one-pseudoscalar-meson exchanges. The contact terms and the couplings of the pseudoscalar mesons to the baryons are related via SU(3) flavor symmetry to the S=-1 hyperon-nucleon channels. We show that the chiral effective field theory predictions with natural values for the low-energy constants agree with the experimental information in the S=-2 sector.

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arXiv2007

Dbar-N interaction from meson-exchange and quark-gluon dynamics

We investigate the Dbar-N interaction at low energies using a meson-exchange model supplemented with a short-distance contribution from one-gluon-exchange. The model is developed in close analogy to the meson-exchange KN interaction of the Juelich group utilizing SU(4) symmetry constraints. The main ingredients of the interaction are provided by vector meson (rho, omega) exchange and higher-order box diagrams involving D*N, DΔ, and D*Δintermediate states. The short range part is assumed to receive additional contributions from genuine quark-gluon processes. The predicted cross sections for Dbar-N for excess energies up to 150 MeV are of the same order of magnitude as those for KN but with average values of around 20 mb, roughly a factor two larger than for the latter system. It is found that the omega-exchange plays a very important role. Its interference pattern with the rho-exchange, which is basically fixed by the assumed SU(4) symmetry, clearly determines the qualitative features of the Dbar-N interaction -- very similiar to what happens also for the KN system.

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arXiv2007

On the sign of the pi-rho-omega coupling constant

It is shown that the relative sign between the $NNω$ and $πρω$ coupling constants can be determined most sensitively from $ω$ production processes in $NN$ collisions. Recent data on these reactions clearly favor the sign of the $πρω$ coupling constant which is opposite to that inferred from studies of the photoproduction reaction in combination with the vector meson dominance assumption and used by many authors. Implication of this finding in the description of other reactions is discussed.

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arXiv2007

The hyperon-nucleon interaction: conventional versus effective field theory approach

Hyperon-nucleon interactions are presented that are derived either in the conventional meson-exchange picture or within leading order chiral effective field theory. The chiral potential consists of one-pseudoscalar-meson exchanges and non-derivative four-baryon contact terms. With regard to meson-exchange hyperon-nucleon models we focus on the new potential of the Juelich group, whose most salient feature is that the contributions in the scalar--isoscalar (σ) and vector--isovector (ρ) exchange channels are constrained by a microscopic model of correlated ππand KKbar exchange.

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arXiv2007

The pp -> K^+Sigma^+n cross section from missing mass spectra

We utilize existing inclusive data on K^+ meson momentum spectra of the reaction pp -> K^+X at T_p = 2.3 - 2.85 GeV to deduce total cross sections for pp -> K^+Σ^+n. The method used to extract those cross sections is explained and discussed in detail. Our result for T_p = 2.85 GeV is consistent with the data point from a direct measurement at the same beam energy. The cross section obtained for T_p = 2.3 GeV is with 13.7\pm2.3 μb considerably smaller than the value found in a recent experiment by the COSY-11 Collaboration at a somewhat lower beam energy, indicating that the pp -> K^+Σ^+n reaction cross section could exhibit a rather unusual energy dependence.

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