Shonle, John I.
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Differential cross section and recoil polarization measurements for the gamma p to K+ Lambda reaction using CLAS at Jefferson Lab

The CLAS collaboration McCracken, M.E. ; Bellis, M. ; Meyer, C.A. ; et al.
Phys.Rev.C 81 (2010) 025201, 2010.
Inspire Record 840934 DOI 10.17182/hepdata.54967

We present measurements of the differential cross section and Lambda recoil polarization for the gamma p to K+ Lambda reaction made using the CLAS detector at Jefferson Lab. These measurements cover the center-of-mass energy range from 1.62 to 2.84 GeV and a wide range of center-of-mass K+ production angles. Independent analyses were performed using the K+ p pi- and K+ p (missing pi -) final-state topologies/ results from these analyses were found to exhibit good agreement. These differential cross section measurements show excellent agreement with previous CLAS and LEPS results and offer increased precision and a 300 MeV increase in energy coverage. The recoil polarization data agree well with previous results and offer a large increase in precision and a 500 MeV extension in energy range. The increased center-of-mass energy range that these data represent will allow for independent study of non-resonant K+ Lambda photoproduction mechanisms at all production angles.

241 data tables
Table 1

Differential cross section as a function of COS(THETA(K)) for the centre-of-mass range 1.62-1.63 GeV.

Table 2

Differential cross section as a function of COS(THETA(K)) for the centre-of-mass range 1.63-1.64 GeV.

Table 3

Differential cross section as a function of COS(THETA(K)) for the centre-of-mass range 1.64-1.65 GeV.

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Angular distributions of leptons from J/psi's produced in 920- GeV fixed-target proton-nucleus collisions

The HERA-B collaboration Abt, I. ; Adams, M. ; Agari, M. ; et al.
Eur.Phys.J.C 60 (2009) 517-524, 2009.
Inspire Record 810555 DOI 10.17182/hepdata.57473

A study of the angular distributions of leptons from decays of J/psi's produced in p-C and p-W collisions at sqrt{s}=41.6 GeV has been performed in the Feynman-x region -0.34 < x_F < 0.14 and for transverse momentum up to 5.4 GeV/c. The data were collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The results, based on a clean selection of 2.3 x 10^5 J/psi's reconstructed in both the e^+ e^- and mu^+ mu^- decay channels, indicate that J/psi's are produced with longitudinal polarization. The magnitude of the effect is maximal at low p_T. For p_T >1 GeV/c a significant dependence on the reference frame is found: the polar anisotropy is more pronounced in the Collins-Soper frame and almost vanishes in the helicity frame, where, instead, a significant azimuthal anisotropy arises.

9 data tables
Table 1

Output parameters obtained by fitting the distributions.

Table 2

Values of the parameters Lambda_theta, Lambda_phi et Lambda_theta_phi measured in the Collins-Soper frame as functions of the average reconstructed p_T for combined carbon and tungsten data.

Table 3

Values of the parameters Lambda_theta, Lambda_phi et Lambda_theta_phi measured in the Collins-Soper frame as functions of the average reconstructed x_F for combined carbon and tungsten data.

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Measurement of $\pi^0 \Lambda$, $\bar{K}^0 n$, and $\pi^0 \Sigma^0$ production in $K^- p$ interactions for $p_{K^-}$ between 514 and 750 MeV/$c$

Prakhov, S. ; Nefkens, B.M.K. ; Bekrenev, V. ; et al.
Phys.Rev.C 80 (2009) 025204, 2009.
Inspire Record 804864 DOI 10.17182/hepdata.52376

The results on the differential cross sections as well as the polarizations of $\Lambda$ and $\Sigma^0$ have been obtained for $\bar{K}^0 n$, $\pi^0 \Lambda$, and $\pi^0 \Sigma^0$ production in $K^- p$ interactions at eight $K^-$ momenta between 514 and 750 MeV/$c$. The study is conducted by measuring multiphoton final states with the Crystal Ball spectrometer, using a $K^-$ beam from the Alternating Gradient Synchrotron of BNL. The results improve substantially the existing data, allowing a detailed reexamination of the $\Lambda^*$ and $\Sigma^*$ states in our energy range.

11 data tables
Table 1

Differential cross section for the K- P --> KBAR0 N reaction. Errors are statistical only.

Table 2

Differential cross section for the K- P --> KBAR0 N reaction. Errors are statistical only.

Table 3

Differential cross section for the K- P --> PI0 LAMBDA reaction. Errors are statistical only.

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Neutron-proton charge-exchange amplitudes at 585-MeV

Chiladze, D. ; Carbonell, J. ; Dzyuba, A. ; et al.
2008.
Inspire Record 803150 DOI 10.17182/hepdata.52344

The differential cross section and deuteron analysing powers of the dp -> {pp}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using a deuteron beam of energy 1170 MeV, data were obtained for small momentum transfers to a {pp} system with low excitation energy. A good quantitative understanding of all the measured observables is provided by the impulse approximation using known neutron-proton amplitudes. The proof of principle achieved here for the method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable.

6 data tables
Table 1

Differential cross section for the unpolarized DEUT P --> P P N reaction integrated over momentum transfer Q < 100 MeV.

Table 2

Unpolarized differential cross section for the DEUT P --> P P N reaction of (P P) excitation energies < 3 MeV.

Table 3

Spherical tensor analysing powers t20 and t22 for EPP 0.1 to 1.0 MeV and cos(theta) > 0.5.

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Cross Section and Tensor Analysing Power of the $\vec{d}d\to \eta\alpha$ Reaction Near Threshold

The GEM collaboration Budzanowski, A. ; Chatterjee, A. ; Gebel, R. ; et al.
Nucl.Phys.A 821 (2009) 193-209, 2009.
Inspire Record 803178 DOI 10.17182/hepdata.52401

The angular distributions of the unpolarised differential cross section and tensor analysing power $A_{xx}$ of the $\vec{d}d\to\alpha \eta$ reaction have been measured at an excess energy of 16.6 MeV. The ambiguities in the partial-wave description of these data are made explicit by using the invariant amplitude decomposition. This allows the magnitude of the s-wave amplitude to be extracted and compared with results published at lower energies. In this way, firmer bounds could be obtained on the scattering length of the $\eta \alpha$ system. The results do not, however, unambiguously prove the existence of a quasi-bound $\eta \alpha$ state.

3 data tables
Table 1

Total cross section from fit to the differential angular distribution.

Table 2

Differential angular distribution.

Table 3

Analysing power measurements.


Linearly polarised photon beams at ELSA and measurement of the beam asymmetry in pi^0-photoproduction off the proton

The CBELSA & TAPS collaborations Elsner, D. ; Bantes, B. ; Bartholomy, O. ; et al.
Eur.Phys.J.A 39 (2009) 373-381, 2009.
Inspire Record 799078 DOI 10.17182/hepdata.50479

At the electron accelerator ELSA a linearly polarised tagged photon beam is produced by coherent bremsstrahlung off a diamond crystal. Orientation and energy range of the linear polarisation can be deliberately chosen by accurate positioning of the crystal with a goniometer. The degree of polarisation is determined by the form of the scattered electron spectrum. Good agreement between experiment and expectations on basis of the experimental conditions is obtained. Polarisation degrees of P = 40% are typically achieved at half of the primary electron energy. The determination of P is confirmed by measuring the beam asymmetry, \Sigma, in pi^0 photoproduction and a comparison of the results to independent measurements using laser backscattering.

20 data tables
Table 1

Beam asymmetry as a function of the PI0 centre of mass scattering angle.

Table 2

Beam asymmetry as a function of the PI0 centre of mass scattering angle.

Table 3

Beam asymmetry as a function of the PI0 centre of mass scattering angle.

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Measurement of the beam asymmetry $\Sigma$ in $\pi^°\eta$ production off the proton with the CBELSA/TAPS experiment

The CBELSA collaboration Gutz, E. ; Sokhoyan, V. ; van Pee, H. ; et al.
Eur.Phys.J.A 35 (2008) 291-293, 2008.
Inspire Record 788569 DOI 10.17182/hepdata.54889

In photoproduction experiments, a large number of final states yielding various resonance contributions are accessible. To extract resonance parameters via partial-wave analysis not only the measurement of differential cross-sections is necessary, but also the determination of polarization observables. At the electron accelerator ELSA (Bonn) the coherent bremsstrahlung method was used to generate a linearly polarized photon beam. Using the CBELSA/TAPS detector setup, the beam asymmetry Σ in the reaction γp → pπ 0 η was determined as a function of various masses and angles for photon energies between 970MeV and 1650MeV.

12 data tables
Table 1

Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 0.970 to 1.200 GeV.

Table 2

Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 1.200 to 1.450 GeV.

Table 3

Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 1.450 to 1.650 GeV.

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Polarization of J / psi and psi(2S) mesons produced in p anti-p collisions at s**(1/2) = 1.96-TeV

The CDF collaboration Abulencia, A. ; Adelman, Jahred A. ; Affolder, T. ; et al.
Phys.Rev.Lett. 99 (2007) 132001, 2007.
Inspire Record 747876 DOI 10.17182/hepdata.42742

We have measured the polarizations of J/ψ and ψ(2S) mesons as functions of their transverse momentum pT when they are produced promptly in the rapidity range |y|<0.6 with pT≥5  GeV/c. The analysis is performed using a data sample with an integrated luminosity of about 800  pb−1 collected by the CDF II detector. For both vector mesons, we find that the polarizations become increasingly longitudinal as pT increases from 5 to 30  GeV/c. These results are compared to the predictions of nonrelativistic quantum chromodynamics and other contemporary models. The effective polarizations of J/ψ and ψ(2S) mesons from B-hadron decays are also reported.

2 data tables
Table 1

Polarization parameter ALPHA for J/PSI production.

Table 2

Polarization parameter ALPHA for PSI(2S) production.


Measurement of the beam asymmetry in eta photoproduction off the proton.

The CBELSA & TAPS collaborations Elsner, D. ; Anisovich, A.V. ; Anton, G. ; et al.
Eur.Phys.J.A 33 (2007) 147-155, 2007.
Inspire Record 744568 DOI 10.17182/hepdata.43430

The beam asymmetry, $\Sigma$, was measured at ELSA in the reaction $\vec \gamma p \to \eta p$ using linearly polarised tagged photon beams, produced by coherent bremsstrahlung off a diamond. The crystal was oriented to provide polarised photons in the energy range $E_\gamma = 800$ to 1400 MeV with the maximum polarisation of $P_\gamma = 49$ % obtained at 1305 MeV. Both dominant decay modes of the $\eta$ into two photons and $3\pi^0$ were used to extract the beam asymmetry from the azimuthal modulation of the cross section. The measurements cover the angular range $\Theta_\text{cm}\simeq 50$ -- 150 degrees. Large asymmetries up to 80 % are observed, in agreement with a previous measurement. The eta-MAID model and the Bonn--Gatchina partial wave analysis describe the measurements, but the required partial waves differ significantly.

6 data tables
Table 1

Photon asymmetry for eta photoproduction at incident photon energy of 850 MeV.

Table 2

Photon asymmetry for eta photoproduction at incident photon energy of 950 MeV.

Table 3

Photon asymmetry for eta photoproduction at incident photon energy of 1050 MeV.

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Separated structure functions for the exclusive electroproduction of K+ Lambda and K+ Sigma0 final states.

The CLAS collaboration Ambrozewicz, P. ; Carman, D.S. ; Feuerbach, R.J. ; et al.
Phys.Rev.C 75 (2007) 045203, 2007.
Inspire Record 732363 DOI 10.17182/hepdata.4994

We report measurements of the exclusive electroproduction of $K^+\Lambda$ and $K^+\Sigma^0$ final states from a proton target using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions $\sigma_T$, $\sigma_L$, $\sigma_{TT}$, and $\sigma_{LT}$ were extracted from the $\Phi$- and $\epsilon$-dependent differential cross sections taken with electron beam energies of 2.567, 4.056, and 4.247 GeV. This analysis represents the first $\sigma_L/\sigma_T$ separation with the CLAS detector, and the first measurement of the kaon electroproduction structure functions away from parallel kinematics. The data span a broad range of momentum transfers from $0.5\leq Q^2\leq 2.8$ GeV$^2$ and invariant energy from $1.6\leq W\leq 2.4$ GeV, while spanning nearly the full center-of-mass angular range of the kaon. The separated structure functions reveal clear differences between the production dynamics for the $\Lambda$ and $\Sigma^0$ hyperons. These results provide an unprecedented data sample with which to constrain current and future models for the associated production of strangeness, which will allow for a better understanding of the underlying resonant and non-resonant contributions to hyperon production.

531 data tables
Table 1

Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.6 to 1.7 GeV.

Table 2

Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.70 to 1.75 GeV.

Table 3

Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.75 to 1.80 GeV.

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