Besson, D.
Two-Photon
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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
Table 1

Additional overall systematic error 5.9% not included.

Table 2

Additional overall systematic error 5.9% not included.


rivet Analysis
Measurement of cross-section for gamma gamma ---> p anti-p

The CLEO collaboration Artuso, M. ; He, D. ; Goldberg, M. ; et al.
Phys.Rev.D 50 (1994) 5484-5490, 1994.
Inspire Record 358510 DOI 10.17182/hepdata.47137

A measurement of the cross section for γγ→pp¯ is performed at two-photon center-of-mass energies between 2.00 and 3.25 GeV. These results are obtained using e+e−→e+e−pp¯ events selected from 1.31 fb−1 of data taken with the CLEO II detector. The measured cross section is in reasonable agreement with previous measurements and is in excellent agreement with recent calculations based on a diquark model. However, leading order QCD calculations performed using the Brodsky-Lepage formalism are well below the measured cross section.

3 data tables
Table 1

Data read from graph.

Table 2

Data read from graph.

Table 3

Data read from graph.


Inclusive charged hadron and K0 production in two photon interactions

Cords, D. ; Boyer, J. ; Butler, F. ; et al.
Phys.Lett.B 302 (1993) 341-344, 1993.
Inspire Record 340849 DOI 10.17182/hepdata.28958

The inclusive transverse momentum distributions of charged hadrons and K 0 's produced in tagged photon-photon collisions, are measured and compared to model calculations up to a p T of 5 GeV/ c . The relative abundance of K 0 's favor the inclusion of charm.

1 data table
Table 1

Data read from graph.


rivet Analysis
An Experimental study of the process gamma gamma ---> pi+ pi-

The CELLO collaboration Behrend, H.J. ; Criegee, L. ; Field, J.H. ; et al.
Z.Phys.C 56 (1992) 381-390, 1992.
Inspire Record 345437 DOI 10.17182/hepdata.14534

Using the CELLO detector, we have measured cross sections for the processγγ→π+π− in the mass range 0.75–1.9 GeV/c2. A partial wave fit to the data indicates the presence of a sizeableS-wave amplitude with signs of resonant behaviour. Values for the γγ width of thef2(1270) are given, showing the model-dependence of this quantity. At higher dipion masses, the model of Brodsky and Lepage is found to give an order of magnitude description of the data.

2 data tables
Table 1

No description provided.

Table 2

No description provided.


rivet Analysis
A Spin parity analysis of gamma gamma ---> rho+ rho-

The ARGUS collaboration Albrecht, H. ; Ehrlichmann, H. ; Hamacher, T. ; et al.
Phys.Lett.B 267 (1991) 535-540, 1991.
Inspire Record 315058 DOI 10.17182/hepdata.29334

A spin-parity analysis of the ϱ + ϱ − system in the reaction γγ→ϱ + ϱ − →Π + Π − Π 0 Π 0 has been performed using the ARGUS detector at the e + e − storage ring DORIS II at DESY. The cross section is found to be dominated by the amplitudes J P = 0 + and J P = 2 + ( J z = 2).

2 data tables
Table 1

No description provided.

Table 2

Cross section for different JP states.


Measurement and analysis of the reaction gamma gamma ---> 3 pi+ 3 pi-

The JADE collaboration Pust, R. ; Olsson, J. ; Allison, J. ; et al.
Z.Phys.C 51 (1991) 531-540, 1991.
Inspire Record 314005 DOI 10.17182/hepdata.14926

The reactionγγ→3π+3π- has been studied usig the JADE detector at PETRA. The topological cross sectionσ(γγ→3π+3π-) was measured in the CM energy range 1.5–5.5 GeV. The production ofρ0,s was observed and the average number ofρ0,s per event measured. The contributions of the subprocessesγγ→ρ02π+2π-,γγ→ρ0ρ0π+2π- andγγ→ 3π+3π- (phase space) were studied and 95% C.L. upper limits for the cross sectionσ(γγ→ρ0ρ0π+π- determined. Finally the Bose-Einstein correlation for pairs of like signed pions was observed. A fit to a standard parametrization gave results consistent with other studies of this effect in pion systems.

4 data tables
Table 1

Topological cross section.

Table 2

Fractions of events for different final states resulting from the extended liklihood fit using incoherent weights.

Table 3

Fractions of events for different final states resulting from the extended liklihood fit using coherent weights.

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rivet Analysis
Two photon production of pion pairs

Boyer, J. ; Butler, F. ; Gidal, G. ; et al.
Phys.Rev.D 42 (1990) 1350-1367, 1990.
Inspire Record 304882 DOI 10.17182/hepdata.22881

We present a new high-statistics measurement of the cross section for the process e+e−→e+e−π+π− at a center-of-mass energy of 29 GeV for invariant pion-pair masses M(π+π−) between 350 MeV/c2 and 1.6 GeV/c2. We observe the f2(1270) and measure its radiative width to be 3.15±0.04±0.39 keV. We also observe an enhancement in the π+π− spectrum near 1 GeV. General agreement is found with unitarized models of the γγ→π+π− reaction that include final-state interactions.

2 data tables
Table 1

No description provided.

Table 2

Statistical errors only.


A Measurement of the photon structure function F2

The AMY collaboration Sasaki, T. ; Yamagishi, Y. ; Tanaka, R. ; et al.
Phys.Lett.B 252 (1990) 491-498, 1990.
Inspire Record 299056 DOI 10.17182/hepdata.29524

The photon structure function F 2 has been measured at average Q 2 values of 73,160 and 390 ( GeV c ) 2 . We compare the x dependence of the Q 2 = 73 ( GeV c ) 2 data with theoretical expectations based on QCD. In addition we present results on the Q 2 evolution of the structure function for the intermediate x range (0.3⩽ x ⩽0.8). The results are consistent with QCD.

4 data tables
Table 1

X dependence at Q**2 = 73 GeV**2 for light quark data.

Table 2

X dependence at Q**2 = 73 GeV**2 for total data.

Table 3

Photon structure function F2 for total data.

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Rho0 production in the reaction gamma gamma ---> 3 pi+ 3 pi- and search for gamma gamma ---> rho0 rho0 (1700)

The CELLO collaboration Behrend, H.J. ; Criegee, L. ; Field, J.H. ; et al.
Z.Phys.C 49 (1991) 43-48, 1991.
Inspire Record 27985 DOI 10.17182/hepdata.15027

We have studied the ρ0 production rate in the reaction ξξ→3π+3π− in the energy range 1.6≦Wγγ≦7.5 GeV with the CELLO detector at PETRA. Our analysis points to a substantial yield of ρ0ρ0π+π− events in particular atWγγ>4.0 GeV. We give cross sections for the ρ02π+2π− and ρ0ρ0π+π− final states and calculate upper limits for the reaction γγ→ρ0ρ0 (1700) →ρ0ρ0π+π−.

3 data tables
Table 1

Data from CA model analysis.

Table 2

Data from NCA model analysis.

Table 3

Upper limits to RHO0 RHO(1700)0 cross section with 95 pct confidence limits. Data read from graph.


Measurement of two photon production of rho0 omega

The JADE collaboration Wegner, A. ; Olsson, J. ; Allison, J. ; et al.
Z.Phys.C 48 (1990) 393-400, 1990.
Inspire Record 297909 DOI 10.17182/hepdata.15125

The reaction γγ→π+π-π+π-π0 has been studied using the JADE detector at PETRA. The cross sections for γγ→ωπ+- and for γγ→ωρ0- are given. We observe no peak in these cross sections in the regionWγγ=1.9–2.0 GeV.

1 data table
Table 1

No description provided.