HEPData Search

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Inclusive double-helicity asymmetries in neutral pion and eta meson production in $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=200$ GeV

The PHENIX collaboration Adare, A. ; Aidala, C. ; Ajitanand, N.N. ; et al.

Phys.Rev.D 90 (2014) 012007, 2014.

Inspire Record 1282448 DOI 10.17182/hepdata.64716

Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, $A_{LL}$, for $\pi^0$ and $\eta$ production in $\sqrt{s} = 200$ GeV polarized $p$$+$$p$ collisions. Comparison of the $\pi^0$ results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, $\Delta G$, in the proton in the probed Bjorken $x$ range. The effect of adding the new 2009 \pz data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}} = 0.06^{+0.11}_{-0.15}$ in the range $0.05<x<0.2$, with the uncertainty at $\Delta \chi^2 = 9$ when considering only statistical experimental uncertainties. Shifting the PHENIX data points by their systematic uncertainty leads to a variation of the best-fit value of $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}}$ between $0.02$ and $0.12$, demonstrating the need for full treatment of the experimental systematic uncertainties in future global analyses.

9 data tables

Table 1

PI0 ASYM(LL) measurements from 2005.

Table 2

PI0 ASYM(LL) measurements from 2006.

Table 3

PI0 ASYM(LL) measurements from 2009.

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W boson polarisation at LEP2.

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.

Phys.Lett.B 585 (2004) 223-236, 2004.

Inspire Record 635790 DOI 10.17182/hepdata.49660

Elements of the spin density matrix for W bosons in e+e- -> W+W- -> qqln events are measured from data recorded by the OPAL detector at LEP. This information is used calculate polarised differential cross-sections and to search for CP-violating effects. Results are presented for W bosons produced in e+e- collisions with centre-of-mass energies between 183 GeV and 209 GeV. The average fraction of W bosons that are longitudinally polarised is found to be (23.9 +- 2.1 +- 1.1)% compared to a Standard Model prediction of (23.9 +- 0.1)%. All results are consistent with CP conservation.

7 data tables

Table 1

The fraction of longitudinal polarization for leptonically and hadronically decaying W bosons. The average values for all the centre of mass energies and for both lepton and hadron decay combined are also given.

Table 2

The luminosity weighted average over all the centre of mass energies of the diagonal elements of the RHO++ and RHO-- SDM as a function of the cosine of the angle of the W- boson for the leptonic decay channel.

Table 3

The luminosity weighted average over all the centre of mass energies of the diagonal element of the RHO00 SDM as a function of the cosine of the angle of the W- boson for both leptonic and hadronic decay channels, and combined.

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Measurements of Delta sigma-L (n p) between 500-MeV and 800-MeV

Beddo, M. ; Burleson, G. ; Faucett, J.A. ; et al.

Phys.Lett.B 258 (1991) 24-28, 1991.

Inspire Record 29058 DOI 10.17182/hepdata.51096

A measurement of Δσ L (np), the difference between neutron-proton total cross sections in pure longitudinal spin states, is described. Data were taken for five energies between 500 and 800 MeV, with statistical errors of ≈ 1.5 mb and an estimated normalization error of 6%. The data, combined with other results, show some evidence for an elastic I =0 spin-singlet resonance with mass ∼ 2213 MeV and width ∼ 74 MeV, or a coupled-triplet resonance with similar mass and width.

1 data table

Table 1

SIG(C=PARALLEL)-SIG(C=ANTIPARALLEL) means the difference in the total crosssection with initial parallel and antiparallel longitudinal spin states. The I0 means I=0, these values were found using interpolated Delta(sigma(pp)) data.

Measurement of eta photoproduction on the proton from threshold to 1500-MeV

The GRAAL collaboration Bartalini, O. ; Bellini, V. ; Bocquet, J.P. ; et al.

Eur.Phys.J.A 33 (2007) 169-184, 2007.

Inspire Record 755415 DOI 10.17182/hepdata.51526

Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.

45 data tables

Table 1

Measured beam asymmetry at photon energy 724 MeV as a function of the ETA centre of mass angle.

Table 2

Measured beam asymmetry at photon energy 761 MeV as a function of the ETA centre of mass angle.

Table 3

Measured beam asymmetry at photon energy 810 MeV as a function of the ETA centre of mass angle.

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n p elastic analyzing power A(NO) and spin transfer K(NN)

McNaughton, M.W. ; Johnston, K. ; Swenson, D. ; et al.

Phys.Rev.C 48 (1993) 256-265, 1993.

Inspire Record 34401 DOI 10.17182/hepdata.51045

We have measured the analyzing power ANO and the spin transfer KNN for np-elastic scattering from about 60° to 170° c.m. at 485, 635, and 788 MeV. The new data clarify previous discrepancies and complete the first-order determination of nucleon-nucleon elastic scattering at these energies.

6 data tables

Table 1

For definition of the POL(NAME=SPIN-TRANSFER) see text.

Table 2

For definition of the POL(NAME=SPIN-TRANSFER) see text.

Table 3

For definition of the POL(NAME=SPIN-TRANSFER) see text.

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Test of Charge Symmetry in Neutron - Proton Elastic Scattering at 477-{MeV}

Abegg, R. ; Bandyopadhyay, D. ; Birchall, J. ; et al.

Phys.Rev.Lett. 56 (1986) 2571, 1986.

Inspire Record 228239 DOI 10.17182/hepdata.20237

An experiment resulting in the first measurement of the isospin-mixing, charge-symmetry-violating component of the n−p interaction has been performed. The experiment determined the difference in the angles of the zero crossing of the neutron and proton analyzing powers An and Ap at 477 MeV. In terms of the laboratory scattering angle of the neutron, the measured difference is θ0n(An)−θ0n(Ap)=+0.13° ±0.06° (±0.03°), where the second error is a worst-case estimate of systematic error. The resulting difference in the analyzing powers at the zero-crossing angle is An−Ap=+0.0037 ±0.0017 (±0.0008).

1 data table

Table 1

No description provided.

Production Polarization and Magnetic Moment of $\Xi^{-+}$ Antihyperons Produced by 800-GeV/c Protons

Ho, P.M. ; Longo, M.J. ; Nguyen, A. ; et al.

Phys.Rev.Lett. 65 (1990) 1713-1716, 1990.

Inspire Record 296567 DOI 10.17182/hepdata.22752

The polarization of Ξ¯ + hyperons produced by 800-GeV/c protons in the inclusive reaction p+Be→Ξ¯ ++X has been measured. The average polarization of the Ξ¯ +, at a mean xF=0.39 and pt=0.76 GeV/c, is -0.097±0.012±0.009. The magnetic moment of the Ξ¯ + is 0.657±0.028±0.020 nuclear magneton.

3 data tables

Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

Polarization in pp Elastic Scattering at Large Momentum Transfers

Booth, N.E. ; Conforto, G. ; Esterling, R.J. ; et al.

Phys.Rev.Lett. 21 (1968) 651-652, 1968.

Inspire Record 944913 DOI 10.17182/hepdata.21669

Measurements of the polarization in pp elastic scattering have been made at 5.15 GeV/c over the range −t=0.2 to 1.8 (GeV/c)2. The data are compared with a Regge-pole model, and with the diffraction model of Durand and Lipes in which the absorptive part of the pp interaction is derived from the electromagnetic form factor of the proton. The latter model reproduces the t dependence of the experimental data in a qualitative way.

1 data table

Table 1

'1'.