Braunschweig, W.
Two-Photon
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Measurement of the Two Photon Reaction $\gamma \gamma \to \pi^+ \pi^- \pi^+ \pi^-$ at Large Values of $Q^2$

The TASSO collaboration Braunschweig, W. ; Gerhards, R. ; Kirschfink, F.J. ; et al.
Z.Phys.C 41 (1988) 353-357, 1988.
Inspire Record 250570 DOI 10.17182/hepdata.15557

The process γγ→π+π−π+π− has been investigated in reactions of the typee+e−→e+e−π+π−π+π− in the single tag mode. The range of the four momentum squared of one of the virtual photons was 0.28 GeV2/c2≦Q2≦3.6 GeV2/c2, the average being 〈Q2〉=0.92 GeV2/c2; the other photon was quasi real. The reaction is mainly described by the channels γγ→ρ0ρ0 and γγ→4π (phase space), occuring with about equal probability. TheQ2-dependence of the cross section is in agreement with the ρ form factor.

2 data tables match query
Table 1

Data read from graph.. Additional overall systematic error 25%.

Table 2

Data read from graph.. Additional overall systematic error 25%.. The Q**2 approx 0 datum is deduced from the earlier TASSO paper, Brandelik et al, Phys. Lett. 97B(1980)448, (<a href=http://durpdg.dur.ac.uk/scripts/reacsearch.csh/TESTREAC/red+1151> RED = 1151 </a>) on rho0 rho0 production.


Measurement of the Radiative Width of the A(2) (1320) in Two Photon Interactions

The TASSO collaboration Althoff, M. ; Braunschweig, W. ; Gerhards, R. ; et al.
Z.Phys.C 31 (1986) 537, 1986.
Inspire Record 228876 DOI 10.17182/hepdata.15859

The reactione+e−→e+e− A2 (1320) has been observed by detecting the decayA2→π+,π-π0. The two-photon width of theA2 has been measured to be Г(A2→γγ)=(0.09±0.27 (stat)±0.16 (syst)) keV. The cross section σ(γγ→π+,π-π0 has been determined outside theA2 resonance region.

1 data table match query
Table 1

Data read off a graph.


Measurement of the Photon Structure Function f(2)Gamma at Q**2 from 7-GeV/c**2 to 70-GeV/c**2

The TASSO collaboration Althoff, M. ; Braunschweig, W. ; Gerhards, R. ; et al.
Z.Phys.C 31 (1986) 527, 1986.
Inspire Record 228251 DOI 10.17182/hepdata.15858

We have measured the processe+e−→e+e−+hadrons, where one of the scattered electrons was detected at large angles, withQ2 ranging from 7 to 70 (VeV/c)2. The photon structure functionF2γ(x, Q2) was determined at an averageQ2 of 23 (GeV/c)2. The measurements were compared to theoretical predictions of the Quark Parton Model and Quantum Chromodynamics. In both models a hadronic part was added. Within the errors the data are in agreement with the QPM using quark masses of 300 MeV/c2 for the light quarks. The data also agree with a QCD calculation including higher order corrections. A fit yielded a\(\Lambda _{\overline {MS} } \) value of 140−65+190 MeV, where the errors include statistical and systematic uncertainties.

1 data table match query
Table 1

No description provided.


Differential Cross-sections for $\gamma \gamma \to p \bar{p}$ in the Center-of-mass Energy Range From 2.0-{GeV} to 3.1-{GeV}

The TASSO collaboration Althoff, M. ; Braunschweig, W. ; Gather, K. ; et al.
Phys.Lett.B 130 (1983) 449-453, 1983.
Inspire Record 191417 DOI 10.17182/hepdata.6654

Exclusive production of proton-antiproton pairs by two photon scattering at CM energies between 2.0 GeV and 3.1 GeV has been measured with the TASSO detector at the e + e − storage ring PETRA. The angular distribution is flat within the accepted CM angular range | cos Θ ∗ |⩽0.7 . The integrated cross section (| cos Θ ∗ |⩽0.6) drops from about 4 nb at 2 GeV to less than 0.5 nb above 3 GeV. For the two-photon production of the η c (2984) and its subsequent decay into proton-antiproton the upper limit Γ(η c →γγ)· B (η c → p p )<0.32 keV (95% CL) is found.

3 data tables match query
Table 1

No description provided.

Table 2

No description provided.

Table 4

No description provided.


Angular Correlations in gamma Gamma ---> rho0 rho0 Near Threshold

The TASSO collaboration Althoff, M. ; Braunschweig, W. ; Gather, K. ; et al.
Z.Phys.C 16 (1982) 13, 1982.
Inspire Record 180755 DOI 10.17182/hepdata.16415

We present an analysis ofρ0ρ0 production by two photons in theρ0ρ0 invariant mass range from 1.2 to 2.0 GeV. From a study of the angular correlations in the process γγ→ρ0ρ0→π−π+π− we exclude a dominant contribution fromJP=0− or 2− states. The data indicate sizeable contributions fromJP=0+ for four pion massesM4π<1.7 GeV and fromJP=2+ forM4π>1.7 GeV. The data are also well described by a model with isotropic production and uncorrelated isotropic decay of theρ0,s. The cross section stays high below the nominalρ0ρ0 threshold, i.e.M4π<1.5 GeV. The matrix element forρ0ρ0 production is found to decrease steeply with increasingM4π. Upper limits for the couplings of the ι(1440) and Θ(1640) to γγ andρ0ρ0 are given:Γ(ι→γγ)·B(ι→ρ0ρ0)<1.0 keV andΓ(Θ→γγ)

2 data tables match query
Table 1

ASSUMING ISOTROPIC RHO0 RHO0 PRODUCTION AND ISOTROPIC RHO DECAY.

Table 2

CROSS SECTIONS FOR DIFFERENT SPIN-PARITY CONTRIBUTIONS.


Measurement of open beauty production at HERA.

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Phys.Lett.B 467 (1999) 156-164, 1999.
Inspire Record 507230 DOI 10.17182/hepdata.43893

The first observation of open b production in ep collisions is reported. An event sample containing muons and jets has been selected which is enriched in semileptonic b quark decays. The visible cross section \sigma(ep -> b \bar{b}X -> \mu X') for Q^2 < 1 GeV^2, 0.1 < y < 0.8 is measured to be 0.176+-0.016(stat.)+0.026-0.017(syst.) nb for the muons to be detected in the range 35 deg < \theta^\mu < 130 deg and \pt^\mu > 2.0 GeV in the laboratory frame. The expected visible cross section based on a NLO QCD calculation is 0.104+-0.017 nb. The cross sections for electroproduction with Q^2<1 GeV^2 and photoproduction are derived from the data and found to be \sigma(ep-> e b\bar{b}X) = 7.1+-0.6(stat.)+1.5-1.3(syst.) nb and \sigma(\gamma p-> b\bar{b} X) = 111+-10(stat.)+23-20(syst.) at an average <W_{\gamma p}> \sim 180 GeV, respectively.

2 data tables match query
Table 1

The visible BQ BQBAR --> MUON X cross section in the stated kinematic range.

Table 2

The total electroproduction and photoproduction cross sections extrapolated to the full phase space.


Measurement and Analysis of the Reaction $\gamma \gamma \to \pi^+ \pi^- \pi^+ \pi^-$

The PLUTO collaboration Berger, Christoph ; Genzel, H. ; Lackas, W. ; et al.
Z.Phys.C 38 (1988) 521, 1988.
Inspire Record 252632 DOI 10.17182/hepdata.1916

We have measured the cross section of four charged pion production in photon-photon interactions in the invariant mass range 1.0≦Wγγ≦3.2 GeV and up toQ2=16 GeV2. For 1.2 GeV≦Wγγ≦1.7 GeV the process is dominated by ρ0ρ0 production with a rapid rise in cross section around 1.2 GeV, well below the nominal ρ0ρ0 threshold. The observed distributions in the two particle masses and in the production and decay angles are well described by an incoherent sum of the phase-space subprocesses γγ →ρ0ρ0, →ρ0π+π−, and →π+π−π+π−. A spin-parity analysis of the ρ0ρ0 system showsJP=2+ to dominate, although 0+ is also possible forWγγ≦1.4 GeV. Negative partity states are excluded.

12 data tables match query
Table 1

Fractions of subprocesses from 3-parameter fit to the no-tag data.

Table 2

Fractions of subprocesses from 2-parameter fit to the no-tag data in limited energy range. The Q=1R contribution is set equal to zero.

Table 3

Fractions of subprocesses from 3-parameter fit to the single-tag data.

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First Measurement of the Photon Structure Function F2

The PLUTO collaboration Berger, Christoph ; Genzel, H. ; Grigull, R. ; et al.
Phys.Lett.B 107 (1981) 168-172, 1981.
Inspire Record 167681 DOI 10.17182/hepdata.31043

Using data taken at PETRA we present results on deep inelastic electron photon scattering at momentum transfers 1 < Q 2 < 15 GeV 2 . The results are expressed in terms of the photon structure function F 2 and are compared with QCD predictions and “hadronic” models of the photon. The pointlike component of the photon is found to be dominant.

2 data tables match query
Table 1

Data read from graph.. Data for W < 3.5 in Berger et al. 1981, PL 99B,287 (<a href=http://durpdg.dur.ac.uk/scripts/reacsearch.csh/TESTREAC/red+1164> RED = 1164 </a>).

Table 2

PHOTON STRUCTURE FUNCTION. NUMERICAL VALUES OF DATA ON FIGURE SUPPLIED BY W. WAGNER.


Measurement and QCD Analysis of the Photon Structure Function F2 (x, Q**2)

The PLUTO collaboration Berger, Christoph ; Genzel, H. ; Lackas, W. ; et al.
Nucl.Phys.B 281 (1987) 365, 1987.
Inspire Record 230592 DOI 10.17182/hepdata.33588

We present a measurement of the hadronic structure function F 2 γ ( x , Q 2 ) of the photon in the Q 2 range from 10 to 100 GeV 2 . Data were taken with the PLUTO detector at the e + e - storage ring PETRA. This measurement and previous PLUTO measurements in the Q 2 range of 1.5 to 16 GeV 2 are compared with higher order QCD calculations. The structure function is consistent with the predicted log Q 2 behaviour when charm contributions are subtracted. The x dependence can be well described for 0.1 < x < 0.9 by the regularization scheme of Antoniadis and Grunberg. Within their scheme the data yield a value of Λ MS = 183 + 65/ −40( stat. ) + 46/ −36( sys. ) MeV for the QCD scale parameter.

5 data tables match query
Table 1

Data read from graph.

Table 2

Data read from graph.

Table 3

Data read from graph.

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Experimental Study of the Photon Structure Function F(2) in the High $Q^2$ Region

The JADE collaboration Bartel, W. ; Cords, D. ; Dietrich, G. ; et al.
Phys.Lett.B 121 (1983) 203-208, 1983.
Inspire Record 180758 DOI 10.17182/hepdata.30781

We report on a measurement of the process e + e − →e + e − + hadrons, where one of the scattered electrons is detected at large angles, with an average Q 2 of 23 GeV. The results are analysed in terms of the photon structure function F 2 and are compared with QCD predictions.

3 data tables match query
Table 1

Data read off graph.

Table 2

Data read off graph.

Table 3

Data read off graph.