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Measurement of the hadronic photon structure function F2(gamma)(x, Q**2) in two-photon collisions at LEP

The ALEPH collaboration Heister, A. ; Schael, S. ; Barate, R. ; et al.
Eur.Phys.J.C 30 (2003) 145-158, 2003.
Inspire Record 631231 DOI 10.17182/hepdata.43218

The hadronic photon structure function $F_2^\gamma(x,Q^2)$ is measured from data taken with the ALEPH detector at LEP. At centre-of-mass energies between

4 data tables

Measured value of F2/ALPHAE at a mean Q**2 of 17.3 GeV**2.

Measured value of F2/ALPHAE at a mean Q**2 of 67.2 GeV**2.

Statistical correlation coefficients for the F2 measurements at Q**2 = 17.3 GeV**2.

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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 =780GeV2 using data in the kinematic range 0.15 < x < 0.98. The Q2 evolution of F2gamma is studied for 12.1 < < 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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Observation of diffractive J / psi production at the Fermilab Tevatron

The CDF collaboration Affolder, T. ; Akimoto, H. ; Akopian, A. ; et al.
Phys.Rev.Lett. 87 (2001) 241802, 2001.
Inspire Record 560628 DOI 10.17182/hepdata.55764

We report the first observation of diffractive $J/\psi(\to \mu^+\mu^-)$ production in $\bar pp$ collisions at $\sqrt{s}$=1.8 TeV. Diffractive events are identified by their rapidity gap signature. In a sample of events with two muons of transverse momentum $p_T^{\mu}>2$ GeV/$c$ within the pseudorapidity region $|\eta|<$1.0, the ratio of diffractive to total $J/\psi$ production rates is found to be $R_{J/\psi}= [1.45\pm 0.25]%$. The ratio $R_{J/\psi}(x)$ is presented as a function of $x$-Bjorken. By combining it with our previously measured corresponding ratio $R_{jj}(x)$ for diffractive dijet production, we extract a value of $0.59\pm 0.15$ for the gluon fraction of the diffractive structure function of the proton.

3 data tables

Diffractive to total J/psi production ratio.

Ratio of diffractive to total J/psi rate, per unit of the fractional momentum loss of the leading (anti)proton, and as a function of x-Bjorken of the struck parton of the (anti)proton adjacent to the rapidity gap and participating in the J/psi production.

Gluon fraction of the diffractive structure function of the (anti)proton.


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

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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Measurement of the hadronic photon structure function at LEP1 for values between 9.9-GeV**2 and 284-GeV**2.

The ALEPH collaboration Barate, R. ; Decamp, D. ; Ghez, Philippe ; et al.
Phys.Lett.B 458 (1999) 152-166, 1999.
Inspire Record 499917 DOI 10.17182/hepdata.49109

Inclusive γ ∗ γ interactions to hadronic final states where one scattered electron or positron is detected in the electromagnetic calorimeters have been studied in the LEP 1 data taken by ALEPH from 1991 to 1995. The event sample has been used to measure the hadronic structure function of the photon F 2 γ in three bins with 〈 Q 2 〉 of 9.9, 20.7 and 284 GeV 2 .

10 data tables

The measured values of dsig/dx from the ECAL data in the Q**2 bin 35 to 3000 GeV**2 with a mean of 284 +- 49 GeV**2.

The measured values of dsig/dx from the LCAL data in the Q**2 bin 13 to 44 GeV**2 with a mean of 20.67 +- 016 GeV**2.

The measured values of dsig/dx from the LCAL data in the Q**2 bin 6 to 13 GeV**2 with a mean of 9.93 +- 0.04 GeV**2.

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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

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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 = 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.