Measurement of the charm structure function F2(c)(gamma) of the photon at LEP.

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Phys.Lett.B 539 (2002) 13-24, 2002.
Inspire Record 587909 DOI 10.17182/hepdata.49793

The production of charm quarks is studied in deep-inelastic electron-photon scattering using data recorded by the OPAL detector at LEP at normal e+e- centre-of-mass energies from 183 to 209 GeV. The charm quarks have been identified by full reconstruction of charged D* mesons using their decays into D0pi with the D0 observed in two decay modes with charged particle final states, Kpi and K3pi. The cross-section sigma(D*) for production of charged D* in the reaction e+e- -> e+e-D*X is measured in a restricted kinematical region using two bins in Bjorken x, 0.0014 < x < 0.1 and 0.1 < x < 0.87. From sigma(D*) the charm production cross-section sigma(e+e- -> e+e- ccbar X) and the charm structure function of the photon F 2,c are determined in the region 0.0014 < x < 0.87 and 5 < Q2 < 100 GeV2. For x > 0.1 the perturbative QCD calculation at next-to-leading order agrees perfectly with the measured cross-section. For x < 0.1 the measured cross-section is 43.8 +- 14.3 +- 6.3 +- 2.8 pb with a next-to-leading order prediction of 17.0+2.9-2.3 p.b

3 data tables

The inclusive D* production cross section.

The inclusive charm quark pair cross section. The second DSYS error is due to extrapolation.

The measured structure function F2(C=CHARM). The second DSYS error is due to extrapolation.


Measurement of the hadronic photon structure function F2(gamma) at LEP2.

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Phys.Lett.B 533 (2002) 207-222, 2002.
Inspire Record 583115 DOI 10.17182/hepdata.49744

The hadronic structure of the photon F2gamma is measured as a function of Bjorken x and of the photon virtuality Q2 using deep-inelastic scattering data taken by the OPAL detector at LEP at e+e- centre-of-mass energies from 183 to 209 GeV. Previous OPAL measurements of the x dependence of F2gamma are extended to an average Q2 of <Q2>=780GeV2 using data in the kinematic range 0.15 < x < 0.98. The Q2 evolution of F2gamma is studied for 12.1 < <Q2> < 780GeV2 using three ranges of x. As predicted by QCD, the data show positive scaling violations in F2gamma for the central x region 0.10-0.60. Several parameterisations of F2gamma are in qualitative agreement with the measurements whereas the quark-parton model prediction fails to describe the data.

13 data tables

F2 and DSIG/DX for the EE sample in the high Q**2 region as a function of X.

Statistical correlations between the bins in the preceding table.

The measured value of F2 and DSIG/DX for the SW data sample in the Q**2 range 9 to 15 GeV**2.

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Measurement of the low-x behavior of the photon structure function F2(gamma).

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Ainsley, C. ; et al.
Eur.Phys.J.C 18 (2000) 15-39, 2000.
Inspire Record 529899 DOI 10.17182/hepdata.49907

The photon structure function F2-gamma(x,Q**2) has been measured using data taken by the OPAL detector at centre-of-mass energies of 91Gev, 183Gev and 189Gev, in Q**2 ranges of 1.5 to 30.0 GeV**2 (LEP1), and 7.0 to 30.0 GeV**2 (LEP2), probing lower values of x than ever before. Since previous OPAL analyses, new Monte Carlo models and new methods, such as multi-variable unfolding, have been introduced, reducing significantly the model dependent systematic errors in the measurement.

12 data tables

Results of F2/ALPHAE for the LEP1 data using the SW for Q**2 = 1.9 GeV**2.

Results of F2/ALPHAE for the LEP1 data using the SW for Q**2 = 3.7 GeV**2.

Results of F2/ALPHAE for the LEP1 data using the FD for Q**2 = 8.9 GeV**2.

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Inclusive production of D*+- mesons in photon photon collisions at s**(1/2)(ee) = 183-GeV and 189-GeV and a first measurement of F2(c)(gamma).

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Akesson, P.F. ; et al.
Eur.Phys.J.C 16 (2000) 579-596, 2000.
Inspire Record 510531 DOI 10.17182/hepdata.35045

The inclusive production of D*+- mesons in photon-photon collisions has been measured using the OPAL detector at LEP at e+e- centre-of-mass energies of 183 and 189GeV. The D* mesons are reconstructed in their decay to D0pi+ with the D0 observed in the two decay modes Kpi+ and Kpi+pi-pi+. After background subtraction, 100.4+-12.6(stat) D*+- mesons have been selected in events without observed scattered beam electron ("anti-tagged") and 29.8+-5.9 (stat) D*+- mesons in events where one beam electron is scattered into the detector ("single-tagged"). Direct and single-resolved events are studied separately. Differential cross-sections as functions of the D* transverse momentum p_t and pseudorapidity \eta are presented in the kinematic region 2<p_t<12GeV and \eta<1.5. They are compared to next-to-leading order (NLO) perturbative QCD calculations. The total cross-section for the process (e+e- to e+e-ccbar), where the charm quarks are produced in the collision of two quasi-real photons, is measured to be 842+-97(stat)+-75(syst)+-196(extrapolation)pb. A first measurement of the charm structure function F2 of the photon is performed in the kinematic range 0.0014<x<0.87 and 5<Q^2<100 GeV^2, and the result is compared to a NLO perturbative QCD calculation.

7 data tables

Differential PT distribution for anti-tagged events for both D* decay modesand combined.

Differential ETARAP distribution for anti-tagged events for both D* decay modes and combined.

Integrated cross section using the anti-tagged events for D* production in the kinematic range of the experiment.

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Measurements of the QED structure of the photon.

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Alexander, G. ; et al.
Eur.Phys.J.C 11 (1999) 409-425, 1999.
Inspire Record 495378 DOI 10.17182/hepdata.49315

The structure of both quasi-real and highly virtual photons is investigated using the reaction e+e- -> e+e-mu+mu-, proceeding via the exchange of two photons. The results are based on the complete OPAL dataset taken at e+e- centre-of-mass energies close to the mass of the Z boson. The QED structure function F_2^gamma and the differential cross-section dsigdx for quasi-real photons are obtained as functions of the fractional momentum x from the muon momentum which is carried by the struck muon in the quasi-real photon for values of Q**2 ranging from 1.5 to 400 GeV**2. The differential cross-section dsigdx for highly virtual photons is measured for 1.5< Q**2 < 30 GeV**2 and 1.5< P**2 < 20 GeV**2, where Q**2 and P**2 are the negative values of the four-momentum squared of the two photons such that Q**2 > P**2. Based on azimuthal correlations the QED structure functions F_A^gamma and F_B^gamma for quasi-real photons are determined for an average Q**2 of 5.4 GeV**2.

12 data tables

No description provided.

No description provided.

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Measurement of the Q**2 evolution of the photon structure function F2(gamma).

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Phys.Lett.B 411 (1997) 387-401, 1997.
Inspire Record 446673 DOI 10.17182/hepdata.47450

New measurements are presented of the photon structure function F_2^gamma(Q) at four values of Q^2 between 9 and 59 GeV/c^2 based on data collected with the OPAL detector at centre-of-mass energies of 161-172 GeV, with a total integrated luminosity of 18.1 pb^-1. The evolution of F_2^gamma with Q^2 in bins of x is determined in the Q^2 range from 1.86 to 135 GeV/c^2 using data taken at centre-of-mass energies of 91 GeV and 161-172 GeV. F_2^gamma is observed to increase with Q^2 with a slope of 1/alpha_em dF_2^gamma/dln(Q^2) = 0.10 +0.05 -0.03 measured in the range 0.1 < x < 0.6.

5 data tables

Measured values of F2 for the SW sample.

Measured values of F2 for the FD sample.

F2 for the full X range (0.1 to 0.6) as a function of Q**2. The full SW andFD sample points are tabulated for completeness but are not in the plot or fits . The first three points are previous OPAL data at sqrt(s) = 91 GeV (ZP C74(1997)33).

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Measurement of the photon structure function F2(gamma) at low x.

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Phys.Lett.B 412 (1997) 225-234, 1997.
Inspire Record 447187 DOI 10.17182/hepdata.49560

Deep inelastic electron-photon scattering is studied using e+e- data collected by the OPAL detector at centre-of-mass energies sqrt{s_ee} ~ M_{Z^0}. The photon structure function F_2^gamma(x,Q^2) is explored in a Q^2 range of 1.1 to 6.6 GeV/c^2 at lower x values than ever before. To probe this kinematic region events are selected with a beam electron scattered into one of the OPAL luminosity calorimeters at scattering angles between 27 and 55 mrad. A measurement is presented of the photon structure function F_2^gamma(x,Q^2) at <Q^2> = 1.86 GeV^2 and 3.76 GeV^2 in five logarithmic x bins from 0.0025 to 0.2.

2 data tables

Measurement of the hadron photon structure function. Systematic errors do not contain any effects caused by the four momentum of the quasi-real photon being non zero.

Measurement of the hadron photon structure function. Systematic errors do not contain any effects caused by the four momentum of the quasi-real photon being non zero.


Analysis of hadronic final states and the photon structure function F2(gamma) in deep inelastic electron photon scattering at LEP.

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 74 (1997) 33-48, 1997.
Inspire Record 426209 DOI 10.17182/hepdata.47770

Deep inelastic electron-photon scattering is studied in the Q2 ranges from 6 to 30 GeV2 and from 60 to 400 GeV2 using the full sample of LEP data taken with the OPAL detector at centre-of-mass energies close to the Z0 mass, with an integrated luminosity of 156.4 pb−1. Energy flow distributions and other properties of the measured hadronic final state are compared with the predictions of Monte Carlo models, including HERWIG and PYTHIA. Sizeable differences are found between the data and the models, especially at low values of the scaling variable x. New measurements are presented of the photon structure function $F_2^{αmma }(x,Q^2)$, allowing for the first time for uncertainties in the description of the final state by different Monte Carlo models. The differences between the data and the models contribute significantly to the systematic errors on $F_2^{αmma }$. The slope ${⤪ d}(F_2^{αmma }/←pha )/{⤪ d ln} Q^2$ is measured to be $0.13_{-0.04}^{+0.06}$.

5 data tables

No description provided.

No description provided.

No description provided.

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Measurement of the QED longitudinal structure function of the photon using azimuthal correlations at LEP.

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 74 (1997) 49-55, 1997.
Inspire Record 426207 DOI 10.17182/hepdata.47704

We have studied azimuthal correlations in singly-tagged e+e− → e+e−μ+μ− events at an average Q2 of 5.2 GeV2. The data were taken with the OPAL detector at LEP at e+e− centre-of-mass energies close to the Z0 mass, with an integrated luminosity of approximately 100 pb−1. The azimuthal correlations are used to extract the ratio $F_{B}^{αmma}/F_{2}^{αmma}$ of the QED structure functions $F_{B}^{αmma}(x,Q^{2})$ and $F_{2}^{αmma}(x,Q^{2})$ of the photon. In leading order and neglecting the muon mass $F_{B}^{αmma}$ is expected to be identical to the longitudinal structure function $F_{L}^{αmma}$. The measurement of $F_{B}^{αmma}/F_{2}^{αmma}$ is found to be significantly different from zero and to be consistent with the QED prediction.

1 data table

No description provided.


Measurement of the photon structure function F2 (gamma) in the reaction e+ e- ---> e+ e- + hadrons at LEP

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 61 (1994) 199-208, 1994.
Inspire Record 358863 DOI 10.17182/hepdata.48474

We present measurements of the hadronic photon structure functionF2γ(x), in twoQ2 ranges with mean values of 5.9 GeV2 and 14.7 GeV2. The data were taken by the OPAL experiment at LEP, with\(\sqrt s\) close to theZ0 mass and correspond to an integratede+e− luminosity of 44.8 pb−1. In the context of a QCD-based model we find the quark transverse momentum cutoff separating the vector meson dominance (VMD) and perturbative QCD regions to be 0.27±0.10 GeV. We confirm that there is a significant pointlike component of the photon when the probe photon hasQ2>4 GeV2. Our measurements extend to lower values ofx than any previous experiment, and no increase ofF2γ(x) is observed.

2 data tables

Additional overall systematic error 5.9% not included.

Additional overall systematic error 5.9% not included.