Sciulli, F.J.
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Measurement of the beam asymmetry $\Sigma$ for $\pi^0$ and $\eta$ photoproduction on the proton at $E_\gamma = 9$ GeV

The GlueX collaboration Al Ghoul, H. ; Anassontzis, E.G. ; Austregesilo, A. ; et al.
Phys.Rev.C 95 (2017) 042201, 2017.
Inspire Record 1511149 DOI 10.17182/hepdata.76745

We report measurements of the photon beam asymmetry $\Sigma$ for the reactions $\vec{\gamma}p\to p\pi^0$ and $\vec{\gamma}p\to p\eta $ from the GlueX experiment using a 9 GeV linearly-polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous $\pi^0$ measurements and are the first $\eta$ measurements in this energy regime. The results are compared with theoretical predictions based on $t$-channel, quasi-particle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models.

2 data tables
Table 1

Measurement of the beam asymmetry $\Sigma$ for $\pi^0$ photoproduction on the proton at $E_\gamma = 9$ GeV. The uncorrelated systematic errors (syst) are given in the table below along with a correlated normalization uncertainty (norm) of 3.6% due to the beam polarization.

Table 2

Measurement of the beam asymmetry $\Sigma$ for $\eta$ photoproduction on the proton at $E_\gamma = 9$ GeV. The uncorrelated systematic errors (syst) are given in the table below along with a correlated normalization uncertainty (norm) of 3.6% due to the beam polarization.


Differential cross sections and recoil polarizations for the reaction gamma p -> K+ Sigma0

The CLAS collaboration Dey, B. ; Meyer, C.A. ; Bellis, M. ; et al.
Phys.Rev.C 82 (2010) 025202, 2010.
Inspire Record 857728 DOI 10.17182/hepdata.55696

High-statistics measurements of differential cross sections and recoil polarizations for the reaction $\gamma p \rightarrow K^+ \Sigma^0$ have been obtained using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from 1.69 to 2.84 GeV, with an extensive coverage in the $K^+$ production angle. Independent measurements were made using the $K^{+}p\pi^{-}$($\gamma$) and $K^{+}p$($\pi^-, \gamma$) final-state topologies, and were found to exhibit good agreement. Our differential cross sections show good agreement with earlier CLAS, SAPHIR and LEPS results, while offering better statistical precision and a 300-MeV increase in $\sqrt{s}$ coverage. Above $\sqrt{s} \approx 2.5$ GeV, $t$- and $u$-channel Regge scaling behavior can be seen at forward- and backward-angles, respectively. Our recoil polarization ($P_\Sigma$) measurements represent a substantial increase in kinematic coverage and enhanced precision over previous world data. At forward angles we find that $P_\Sigma$ is of the same magnitude but opposite sign as $P_\Lambda$, in agreement with the static SU(6) quark model prediction of $P_\Sigma \approx -P_\Lambda$. This expectation is violated in some mid- and backward-angle kinematic regimes, where $P_\Sigma$ and $P_\Lambda$ are of similar magnitudes but also have the same signs. In conjunction with several other meson photoproduction results recently published by CLAS, the present data will help constrain the partial wave analyses being performed to search for missing baryon resonances.

149 data tables
Table 1

Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.69 to 1.7 GeV.

Table 2

Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.7 to 1.71 GeV.

Table 3

Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.71 to 1.72 GeV.

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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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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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rivet Analysis
A precise measurement of the tau polarisation at LEP-1.

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Eur.Phys.J.C 14 (2000) 585-611, 2000.
Inspire Record 511443 DOI 10.17182/hepdata.49001

The$\tau$polarisation has been studied with the${\rm e^+e^-}\to \tau^+\tau^-$data collected by the DELPHI detector at LEP in

2 data tables
Table 1

The errors are statistical and systematic combined in quadrature.

Table 2

No description provided.


Measurement of gamma p --> K0 Sigma+ at photon energies up to 1.55-GeV.

The SAPHIR collaboration Goers, S ; Barth, J ; Bennhold, C ; et al.
Phys.Lett.B 464 (1999) 331-338, 1999.
Inspire Record 512574 DOI 10.17182/hepdata.27045

The reaction γp → K 0 Σ + has been measured with the SAPHIR detector at the electron stretcher ring ELSA. The total cross section rises up to a peak value of 1.1 μ b at a photon energy of 1.4 GeV. The differential cross sections dσ/dΩ are consistent with being flat throughout the measured energy range. The first measurement of the Σ + polarization in photon induced reactions was obtained.

3 data tables
Table 1

Total cross section for the reaction GAMMA P --> K0 SIGMA+. Errors include statistics and the uncertainty on the acceptance calculation and photon flux.

Table 2

Differential cross section for the reaction GAMMA P --> K0 SIGMA+. Errors are dominated by statistical uncertainties.

Table 3

Measure of SIGMA+ polarization in the reaction GAMMA P --> K0 SIGMA+.


Measurement of gamma p --> K+ Lambda and gamma p --> K+ Sigma0 at photon energies up to 2-GeV .

The SAPHIR collaboration Tran, M.Q. ; Barth, J. ; Bennhold, C. ; et al.
Phys.Lett.B 445 (1998) 20-26, 1998.
Inspire Record 483236 DOI 10.17182/hepdata.27074

Associated strangeness production in the reactions γp → K + Λ and γp → K + Σ 0 was measured with the SAPHIR detector at the electron stretcher ring ELSA at Bonn. Data on total and differential cross sections and on hyperon polarizations are presented. The total cross section for Λ production shows a strong threshold enhancement whereas the Σ 0 data have a maximum at about E γ =1.45 GeV. Along with the angular decomposition of the differential cross section into polynomials, this suggests resonance production. However, the angular distributions of both hyperon polarizations vary only slightly with the photon energy. Λ and Σ 0 polarizations show opposite signs and change sign over the angular range.

10 data tables
Table 1

Total cross section for the reaction GAMMA P --> K+ LAMBDA.

Table 2

Total cross section for the reaction GAMMA P --> K+ SIGMA0.

Table 3

Differential cross section for the reaction GAMMA P --> K+ LAMBDA in the GAMMA energy range 0.90 to 1.10 GeV in three energy bins.

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Measurement of elastic omega photoproduction at HERA.

The ZEUS collaboration Derrick, M. ; Krakauer, D. ; Magill, S. ; et al.
Z.Phys.C 73 (1996) 73-84, 1996.
Inspire Record 422159 DOI 10.17182/hepdata.44712

The reaction $\gamma p \rightarrow \omega p$ $(\omega \rightarrow \pi~+\pi~-\pi~0$ and $\pi~0\rightarrow\gamma\gamma)$ has been studied in $ep$ interactions using the \mbox{ZEUS} detector at photon-proton centre-of-mass energies between $70$ and $90\uni{GeV}$ and $|t| < 0.6\uni{GeV}~2$, where $t$ is the squared four momentum transferred at the proton vertex. The elastic \ome photoproduction cross section has been measured to be $\sigma_{\gamma p\rightarrow \omega p} = 1.21\pm 0.12\pm 0.23 \mu\mbox{b}$. The differential cross section $d\sigma_{\gamma p\rightarrow \omega p} /d|t|$ has an exponential shape $\mbox{e}~{-b |t|}$ with a slope $b = 10.0\pm 1.2\pm 1.3\uni{GeV}~{-2}$. The angular distributions of the decay pions are consistent with {\it s}-channel helicity conservation. When compared to low energy data, the features of $\omega$ photoproduction as measured at HERA energies are in agreement with those of a soft diffractive process. Previous measurements of the $\rho~0$ and $\phi$ photoproduction cross sections at HERA show a similar behaviour.

4 data tables
Table 1

Total Elastic Cross Section.

Table 2

No description provided.

Table 3

SLOPE OF DSIG/DT distribution.

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Measurement of the Michel parameters and the average tau-neutrino helicity from tau decays in e+ e- ---> tau+ tau-

The L3 collaboration Acciarri, M. ; Adam, A. ; Adriani, O. ; et al.
Phys.Lett.B 377 (1996) 313-324, 1996.
Inspire Record 418417 DOI 10.17182/hepdata.47587

The Michel parameters ϱ, η, ξ, and ξδ, the chirality parameter ξ h and the τ polarization P τ are measured using 32012 τ pair decays. Their values are extracted from the energy spectra of leptons and hadrons in τ − → l − ν l ν τ and τ − → π − ν τ decays, the energy and decay angular distributions in τ − → ϱ − ν τ decays, and the correlations in the energy spectra and angular distributions of the decay products. Assuming universality in leptonic and semileptonic τ decays, the results are ϱ = 0.794±0.039±0.031, η = 0.25±0.17±0.11, ξ = 0.94±0.21±0.07, ξδ = 0.81±0.14±0.06, ξ h = −0.970±0.053±0.011, and P τ = −0.154±0.018±0.012. The measurement is in agreement with the V-A hypothesis for the weak charged current.

1 data table
Table 1

No description provided.


Measurements of the tau polarization in Z0 decays

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Z.Phys.C 67 (1995) 183-202, 1995.
Inspire Record 393793 DOI 10.17182/hepdata.47961

A sample of Z0→τ+τ− events observed in the DELPHI detector at LEP in 1991 and 1992 is analysed to measure the τ polarisation in the exclusive decay channels\(ev\bar v\),\(\mu v\bar v\), πν, ρν and a1ν. The τ polarisation is also measured with an inclusive hadronic analysis which benefits from a higher efficiency and a better systematic precision than the use of the exclusive decay modes. The results have been combined with those published on the 1990 data. A measurement of the τ polarisation as a function of production angle yields the values for the mean τ polarisation 〈P〉τ=−0.148±0.022 and for the Z0 polarisationPZ=−0.136±0.027. These results are used to determine the ratio of vector to axial-vector effective couplings for taus\(\bar v_\tau/\bar a_\tau= 0.074 \pm 0.011\), and for electrons\(\bar v_e /\bar a_e= 0.068 \pm 0.014\), compatible with e-τ universality. With the assumption of lepton universality, the ratio of vector to axial-vector effective couplings for leptons\(\bar v_l /\bar a_l= 0.072 \pm 0.008\) is obtained, implying a value of the effective weak mixing angle sin2θefflept=0.2320±0.0021.

10 data tables
Table 1

Results are for both TAU+ and TAU- decay.

Table 2

The systematic error contains a systematic error of 0.003 common to all channels.

Table 3

Errors are statistical only.

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