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

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

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

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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Measurement of the $\vec{\gamma} p \to K^+ \Lambda$ Reaction at Backward Angles

The LEPS collaboration Hicks, K. ; Mibe, T. ; Sumihama, M. ; et al.
2007.
Inspire Record 756925 DOI 10.17182/hepdata.25090

Cross sections for the $\gamma p \to K^+ \Lambda$ have been measured at backward angles using linearly polarized photons in the range 1.50 to 2.37 GeV. In addition, the beam asymmetry for this reaction has been measured for the first time at backward angles. The $\Lambda$ was detected at forward angles in the LEPS spectrometer via its decay to $p\pi^-$ and the K^+ was inferred using the technique of missing mass. These measurements, corresponding to kaons at far backward angles in the center-of-mass frame, complement similar CLAS data at other angles. Comparison with theoretical models shows that the reactions in these kinematics provide further opportunities to investigate the reaction mechanisms of hadron dynamics.

5 data tables

Differential cross sections as a function of the Mandelstam variable U for photon beam energy 1.5 to 1.8 GeV.

Differential cross sections as a function of the Mandelstam variable U for photon beam energy 1.8 to 2.1 GeV.

Differential cross sections as a function of the Mandelstam variable U for photon beam energy 2.1 to 2.4 GeV.

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The gamma(pol.) p --> K+ Lambda and gamma(pol.) p --> K+ Sigma0 reactions at forward angles with photon energies from 1.5-GeV to 2.4-GeV.

The LEPS collaboration Sumihama, M. ; Ahn, J.K. ; Akimune, H. ; et al.
Phys.Rev.C 73 (2006) 035214, 2006.
Inspire Record 701097 DOI 10.17182/hepdata.41824

Differential cross sections and photon beam asymmetries for the gamma p rightarrow K+ Lambda and gamma p rightarrow K+ Sigma0 reactions have been measured in the photon energy range from 1.5 GeV to 2.4 GeV and in the angular range from Theta_{cm} = 0 to 60 of the K+ scattering angle in the center of mass system at the SPring-8/LEPS facility. The photon beam asymmetries for both the reactions have been found to be positive and to increase with the photon energy. The measured differential cross sections agree with the data measured by the CLAS collaboration at cosTheta_{cm}<0.9 within the experimental uncertainties, but the discrepancy with the SAPHIR data for the K+Lambda reaction is large at cosTheta_{cm}>0.9. In the K+Lambda reaction, the resonance-like structure found in the CLAS and SAPHIR data at W=1.96 GeV is confirmed. The differential cross sections at forward angles suggest a strong K-exchange contribution in the t-channel for the K+Lambda reaction, but not for the K+Sigma0 reaction.

14 data tables

Photon beam asymmetries for the two reactions as a function of CM angle for photon beam energy 1.55 GeV (W=1.947 GeV).

Photon beam asymmetries for the two reactions as a function of CM angle for photon beam energy 1.65 GeV (W=1.994 GeV).

Photon beam asymmetries for the two reactions as a function of CM angle for photon beam energy 1.75 GeV (W=2.041 GeV).

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Measurement of gamma p --> K+ Lambda and gamma p --> K+ Sigma0 at photon energies up to 2.6 GeV

Glander, K.H. ; Barth, J. ; Braun, W. ; et al.
Eur.Phys.J.A 19 (2004) 251-273, 2004.
Inspire Record 626695 DOI 10.17182/hepdata.51677

The reactions gamma p --> K+ Lambda and gamma p --> K+ Sigma0 were measured in the energy range from threshold up to a photon energy of 2.6 GeV. The data were taken with the SAPHIR detector at the electron stretcher facility, ELSA. Results on cross sections and hyperon polarizations are presented as a function of kaon production angle and photon energy. The total cross section for Lambda production rises steeply with energy close to threshold, whereas the Sigma0 cross section rises slowly to a maximum at about E_gamma = 1.45 GeV. Cross sections together with their angular decompositions into Legendre polynomials suggest contributions from resonance production for both reactions. In general, the induced polarization of Lambda has negative values in the kaon forward direction and positive values in the backward direction. The magnitude varies with energy. The polarization of Sigma0 follows a similar angular and energy dependence as that of Lambda, but with opposite sign.

24 data tables

Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 0.9 to 1.0 GeV.

Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.0 to 1.2 GeV.

Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.2 to 1.4 GeV.

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Beam polarization asymmetries for the p(gamma,K+)Lambda and p(gamma,K+)Sigma0 reactions at E(gamma) = 1.5-GeV - 2.4-GeV.

The LEPS collaboration Zegers, R.G.T. ; Sumihama, M. ; Ahn, D.S. ; et al.
Phys.Rev.Lett. 91 (2003) 092001, 2003.
Inspire Record 613016 DOI 10.17182/hepdata.31708

Beam polarization asymmetries for the p(gamma,K+)Lambda and p(gamma,K+)sigma0 reactions are measured for the first time for Egamma=1.5-2.4 GeV and 0.6<cos(theta_cm(K+))<1.0 by using linearly polarized photons at the Laser-Electron-Photon facility at SPring-8 (LEPS). The observed asymmetries are positive and gradually increase with rising photon energy. The data are not consistent with theoretical predictions based on tree-level effective Lagrangian approaches. Including the new results in the development of the models is, therefore, crucial for understanding the reaction mechanism and to test the presence of baryon resonances which are predicted in quark models but are sofar undiscovered.

18 data tables

Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.5 to 1.6.

Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.6 to 1.7.

Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.7 to 1.8.

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Photoproduction of k+ lambda0 and k+ sigma0 from hydrogen at constant momentum transfer t between 1.05 and 2.2 gev

Feller, P. ; Menze, D. ; Opara, U. ; et al.
Nucl.Phys.B 39 (1972) 413-420, 1972.
Inspire Record 75243 DOI 10.17182/hepdata.32925

For the reaction γ p → K + Λ 0 the differential cross section has been measured at t = −0.147 GeV 2 ( θ C.M. = 26.5 ± 3.5°) and photoenergies between 1.05 and 2.2 GeV and for the reaction γ p→K + Σ 0 at ≈−0.17 GeV 2 ( θ C.M. = 28±3.5°) and photoenergies between 1.3 and 2.2 GeV. For this four momentum transfer the differential cross section of K + Λ 0 photoproduction has a surprising steep increase above threshold and stays nearly constant up to 2.2 GeV. The K + Σ 0 cross section increases from 1.3 to 1.56 GeV and goes down gradually at higher energies.

2 data tables

AT CONSTANT MOMENTUM TRANSFER OF -T = 0.147 GEV**2.

AT APPROXIMATELY CONSTANT MOMENTUM TRANSFER OF -T = 0.17 GEV**2.