Buschhorn, G.
Photoproduction
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Search for a Threshold Enhancement in the $\gamma (p) \to$ Charmed Baryon + Charmed Meson Cross-section

The SLAC Hybrid Facility Photon collaboration Abe, K. ; Bacon, T.C. ; Bingham, H.H. ; et al.
Phys.Rev.D 30 (1984) 694, 1984.
Inspire Record 200010 DOI 10.17182/hepdata.23592

Results of a search for a predicted enhancement of several microbarns in the charm-photoproduction cross section just above threshold are reported. No charm decays were detected, from which an upper limit to the charm cross section of 94 nb (90% C.L.) at Eγ≃10 GeV was obtained. Upper limits in the range 270 to 450 nb were also obtained for the peak cross sections for threshold enhancements in γp→D−Σc++ and similar channels.

2 data tables
Table 1

UPPER LIMIT TO AVERAGE CHARM CROSS SECTION.

Table 2

UPPER LIMITS TO INDIVIDUAL CHANNELS.


Measurement of Exclusive $\eta^\prime$ Production in $\gamma \gamma$ Reactions

The PLUTO collaboration Berger, Christoph ; Deuter, A. ; Genzel, H. ; et al.
Phys.Lett.B 142 (1984) 125-129, 1984.
Inspire Record 201708 DOI 10.17182/hepdata.30533

We observe γγ → η′ production in the reaction e + e − → e + e − π + π − γ. We measure the product γ γγ ( η ′) B ( η ′ → ϱ 0 γ ) to be 1.14 ± 0.08 ± 0.11 keV. A first measurement of the γγ → η′ transition form factor is made for Q 2 up to 1 GeV 2 .

1 data table
Table 1

No description provided.


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

The PLUTO collaboration Berger, Christoph ; Deuter, A. ; Genzel, H. ; et al.
Phys.Lett.B 142 (1984) 111-118, 1984.
Inspire Record 201376 DOI 10.17182/hepdata.30545

None

4 data tables
Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

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Observation of the Reaction $\gamma \gamma \to p \bar{p} \pi^+ \pi^-$

The TASSO collaboration Althoff, M. ; Braunschweig, W. ; Kirschfink, F.J. ; et al.
Phys.Lett.B 142 (1984) 135-140, 1984.
Inspire Record 199848 DOI 10.17182/hepdata.30532

Production of the p p π + π − final state by two-photon scattering was observed. The cross section for γγ→p p π + π − was determined assuming phase space production. No evidence was found for the production or formation of resonances. Upper limits are given for Λ and Δ pair production, for production of p p ϱ 0 and for the two-photon excitation of c c bound states.

1 data table
Table 1

No description provided.


Production of the F(0) Meson in Photon-photon Collisions

The CELLO collaboration Behrend, H.J. ; Fenner, H. ; Schachter, M.J. ; et al.
Z.Phys.C 23 (1984) 223, 1984.
Inspire Record 199731 DOI 10.17182/hepdata.16320

The production of thef0 in two photon collisions, with the subsequent decayf0→π+π− has been observed in the CELLO detector at PETRA. Thef0 peak was found to lie on a dipion continuum and to be shifted downwards in mass by ≃50 MeV/c2. The ππ mass spectrum from 0.8 to 1.5 GeV/c2 was well fitted by the model of Mennessier using only a unitarised Born amplitude and helicity 2f0 amplitude. The previously observed mass shift and distortion of thef0 peak are explained by strong interference between the Born andf0 amplitudes. The only free parameter in the fit of the data to the model is the radiative widthΓγγ(f0). It was found that:Γγγ(f0)=2.5±0.1±0.5 keV where the first (second) quoted errors are statistical (systematic).

2 data tables
Table 1

Data read from graph.

Table 2

Data read from graph.


CHARM PHOTOPRODUCTION AT 20-GeV

The SLAC Hybrid Facility Photon collaboration Abe, K. ; Bacon, T.C. ; Ballam, Joseph ; et al.
Phys.Rev.D 30 (1984) 1, 1984.
Inspire Record 194546 DOI 10.17182/hepdata.23639

Sixty-two charm events have been observed in an exposure of the SLAC Hybrid Facility toa backward sacttered laser beam. Based on 22 neutral and 21 charged decays we have measured the charmed-meson lifetimes to be τD0=(6.8−1.8+2.3)×10−13 sec, τD±=(7.4−2.0+2.3)×10−13 sec and their ratio τD±τD0=1.1−0.3+0.6. The inclusive charm cross section at a photon energy of 20 GeV has been measured to be 56−23+24 nb. Evidence is presented for a non-DD¯ component to charm production, consistent with (35±20)% Λc+ production and some D*± production. We have found no unambiguous F decays.

1 data table
Table 1

No description provided.


Exclusive Production of Hadron Pairs at Large Momentum Transfer in Photon-photon Interactions

The PLUTO collaboration Berger, Christoph ; Deuter, A. ; Genzel, H. ; et al.
Phys.Lett.B 137 (1984) 267-271, 1984.
Inspire Record 194772 DOI 10.17182/hepdata.30576

We report on the exclusive production of π, K and proton pairs from photon-photon interactions at momentum transfers | t |⩾1 GeV 2 . Using the PLUTO detector at the e + e − storage ring PETRA, we have observed 15 events in an integrated luminosity of 41.7 pb −1 . The data lie far below the expectations for point-like hadrons, and are in reasonable agreement with the QCD-based predictions of Brodsky and Lepage.

3 data tables
Table 1

THIS METHOD OF ANALYSIS OF THE OBSERVED RATIO OF HADRON TO MUON PAIRS, IS TIED TO THE SPECIFIC DETECTOR ACCEPTANCE, BUT HAS THE ADVANTAGE OF BEING VIRTUALLY INDEPENDENT OF THE HADRON MASSES.

Table 2

SEE COMMENT IN PREVIOUS TABLE.

Table 3

THIS METHOD OF ANALYSIS OF THE CROSS SECTION AT 90 DEG IN THE CM AS A FUNCTION OF PCM IS MORE EASILY COMPARED WITH THEORETICAL PREDICTIONS BUT MORE DEPENDENT ON THE SPECIFIC HADRON MASSES.


Observation of the Production of $\eta$ Mesons in Two Photon Collisions

Weinstein, A. ; Antreasyan, D. ; Gu, Y.F. ; et al.
Phys.Rev.D 28 (1983) 2896, 1983.
Inspire Record 192651 DOI 10.17182/hepdata.23791

Using 2674 nb−1 of data taken at s from 5.00 to 7.25 GeV with a trigger sensitive to decays of lower-mass particles produced in two-photon collisions, we have observed 56±12 events consistent with the reaction e+e−→e+e−η, η→γγ. Background has been subtracted using separated-beam data. We obtain Γγγ(η)=0.56±0.16 keV and the pseudoscalar-nonet mixing angle θP=−17.6°±3.6°.

1 data table
Table 1

No description provided.


rivet Analysis
Pion Pair Production From $\gamma \gamma$ Collisions at {PEP}

Smith, J.R. ; Burke, D.L. ; Abrams, G.S. ; et al.
Phys.Rev.D 30 (1984) 851, 1984.
Inspire Record 195739 DOI 10.17182/hepdata.23582

We have studied several features of the production of charged-hardon pairs by γγ collisions. We have measured the f0 partial width Γf0→γγ(Q2) for Q2 in the range 0

1 data table
Table 1

Data read from graph.. Both statistical and systematic errors included.


Deuteron Photodisintegration at Photon Energies Between 200-{MeV} and 700-{MeV} in Backward Direction

Althoff, K.H. ; Anton, G. ; Bour, D. ; et al.
Z.Phys.C 21 (1983) 149, 1983.
Inspire Record 192906 DOI 10.17182/hepdata.50170

The differential cross section of the deuteron photodisintegration was measured at a protion c.m. angle of 180 degrees and for photon energies between 180 and 730 MeV. The protons were detected in a magnetic spectrometer. The proton energy resolution varied between 30 MeV and 50 MeV FWHM. Since these are the first data at 180 degrees in this energy range a comparison can only be done with data from other laboratories extrapolated to 180 degrees and with theoretical predictions. The agreement with existing calculations is poor. Contributions of dibaryons to the cross section seem not to improve the situation.

1 data table
Table 1

BEAM ERROR D(E) = 50.000 MEV.