Gerhards, R.
Photoproduction
Max results
Sort by Reverse order

Showing 10 of 584 results

Date

Tensor Meson Excitation in the Reaction $\gamma \gamma \to K^0_S K^0_S$

The PLUTO collaboration Berger, Christoph ; Genzel, H. ; Lackas, W. ; et al.
Z.Phys.C 37 (1988) 329, 1988.
Inspire Record 250982 DOI 10.17182/hepdata.15690

In the analysis of the reactione+e−→e+e−KS0Ks0 clear evidence for exclusive γγ→f2′ resonance production is observed. The productΓγγ ·B(f2′→K\(\bar K\)) is measured to be 0.10−0.03−0.02+0.04+0.03 keV independent of ana priori assumption on the helicity structure. Our data are consistent with a pure helicity 2 contribution and we derive an upper limit for the ratioΓγγ(0)/Γγγ. The absence of events in the mass region around 1.3 GeV clearly proves destructivef2−a2 interference and allows to measure the relative phases betweenf2,a2 andf2′. Upper limits on the production of the glueball candidate statesf2(1720) andX(2230) as well as theKS0KS0-continuum are given.

1 data table
Table 1

Data read from graph.


rivet Analysis
First Observation of $\gamma \gamma \to K^*0 \bar{K}^*$0

The ARGUS collaboration Albrecht, H. ; Andam, A.A. ; Binder, U. ; et al.
Phys.Lett.B 198 (1987) 255-260, 1987.
Inspire Record 248680 DOI 10.17182/hepdata.30080

The final state K + K − π + π − has been studied in γγ interactions using the ARGUS detector at the e + e − storage ring DORIS II at DESY. Production of the vector meson pair K ∗0 (892) K ∗0 (892) is observed for the first time. The cross section for K + K − π + π − , K ∗0 K − π + +c.c. and K ∗0 K ∗0 are all found to be of the order of a few nb. In the W γγ range accessible, a mean upper limit of 0.5 nb at 95% CL is derived for φϱ 0 production.

6 data tables
Table 1

TOPOLOGICAL CROSS SECTION.

Table 2

(K*0 K*BAR0) cross section.

Table 3

(K*0 K- PI+ + CC) CROSS SECTION WITH (K*0 K*BAR0) REMOVED.

More…

rivet Analysis
EXCLUSIVE PRODUCTION OF PROTON - ANTI-PROTON PAIRS IN TWO PHOTON COLLISIONS AT PEP

The TPC/Two Gamma collaboration Aihara, H. ; Alston-Garnjost, M. ; Avery, R.E. ; et al.
Phys.Rev.D 36 (1987) 3506, 1987.
Inspire Record 246557 DOI 10.17182/hepdata.23356

We report cross sections for the process γγ→pp¯ at center-of-mass energies W from 2.0 to 2.8 GeV. These results have been extracted from measurements of e+e−→e+e−pp¯ at an overall center-of-mass energy of 29 GeV, using the TPC/Two-Gamma facility at the SLAC storage ring PEP. Cross sections for the untagged mode [both photons nearly real] are shown to lie well above QCD predictions. Results are also presented for the single-tagged mode [one photon in the range 0.16

3 data tables
Table 1

Data read from graph in preprint. Statistical errors only.

Table 2

Data read from graph. Statistical errors only.

Table 3

Data read from graph. Statistical errors only.


rivet Analysis
First Observation of $\gamma \gamma \to \omega \rho^0$

The ARGUS collaboration Albrecht, H. ; Andam, A.A. ; Binder, U. ; et al.
Phys.Lett.B 196 (1987) 101, 1987.
Inspire Record 247567 DOI 10.17182/hepdata.30104

The reaction γγ → 2 π + 2 π − π 0 has been studied using the the ARGUS detector at the e + e − storage ring DORIS II at DESY. The production of the vector-meson pair ωϱ 0 is observed for the first time. The cross section for γγ → ωϱ 0 and the topological cross section for γγ → 2 π + 2 π − π 0 are given. The angular distribution in ωϱ 0 events do not indicate any specific dominant spin-parity; they are consistent with isotropic production and decay of the ω and ϱ 0 mesons over the available W γγ range.

2 data tables
Table 1

Topological cross section.

Table 2

OMEGA RHO0 Production cross section.


First Observation of $\gamma \gamma \to \omega \omega$

The ARGUS collaboration Albrecht, H. ; Andam, A.A. ; Binder, U. ; et al.
Phys.Lett.B 198 (1987) 577-582, 1987.
Inspire Record 247566 DOI 10.17182/hepdata.30070

The reaction γγ → 2 π + 2 π − 2 π 0 has been studied using the ARGUS detector at the e + e − storage ring DORIS II at DESY. Production of ω mesons is observed and, in particular, the reaction γγ → ωω is seen for the first time. The cross section for γγ → ωω has an enhancement at ∼ 1.9 GeV/ c 2 of about 10 nb. The cross sections for γγ → 2 π + 2 π − 2 π 0 and γγ → ωπ + π − π 0 are also given.

3 data tables
Table 1

Topological cross section. 14 pct systematic uncertainty not included.

Table 2

Cross section for (omega omega) production. Additional 25 pct systematic error not included.

Table 3

Cross section for (omega pi+ pi- pi0) where (omega omega) events have been removed. Additional 15 pct systematic error not included.


Pion Pair Production in Photon-photon Collisions at Dci

The DM1-DM2 collaboration Ajaltouni, Z. ; Falvard, A. ; Jousset, J. ; et al.
Phys.Lett.B 194 (1987) 573, 1987.
Inspire Record 248992 DOI 10.17182/hepdata.30109

This paper presents experimental results on π + π − production threshold from the collision of quasi-real photons. The data, obtained at the e + e − collider DCI, are a combination of the results from the DM1 and DM2 experiments. Using the e + e − and π + π − production for normalization and cross-checks, we observe a pion pair yield at low invariant mass ( W < 500 MeV/ c 2 ) which is approximately twice the one expected from Born terms.

2 data tables
Table 1

Data read from graph.

Table 2

Data read from graph.


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
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 $J/\psi$ and $\psi^\prime$ Real Photoproduction on $^{6}$Li at a Mean Energy of 90-{GeV}

The NA14 collaboration Barate, R. ; Bareyre, P. ; Bloch, D. ; et al.
Z.Phys.C 33 (1987) 505, 1987.
Inspire Record 235579 DOI 10.17182/hepdata.15814

Inelastic and elasticJ/ψ (3097) photoproduction on Li6 are measured at a mean γ energy of 90 GeV in an open spectrometer. TheJ/ψ are identified by their decays intoμ+μ− ore+e−. A signal of ψ′(3685) intoμ+μ− andJ/ψπ+π− is also seen. The inelastic cross-section withZ=Eψ/Eγ<0.9 is compared in shape and magnitude with the colour singlet model of photon-gluon fusion.

2 data tables
Table 1

DIMUON TRIGGER, INELASTIC MEANS Z < 0.9.

Table 2

ELECTRON TRIGGER, INELASTIC MEANS Z < 0.9.


Measurement of the Photon Structure Function F2 (Gamma) (x, Q**2) in the Region 0.2-GeV**2 < 7-GeV**2

The TPC/Two Gamma collaboration Aihara, H. ; Alston-Garnjost, M. ; Avery, R.E. ; et al.
Z.Phys.C 34 (1987) 1, 1987.
Inspire Record 234578 DOI 10.17182/hepdata.15803

We present a measurement of the photon structure functionF2γ in the reactionee→eeX forQ2 in the range 0.2

11 data tables
Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

More…

OBSERVATION OF SCALING OF THE PHOTON STRUCTURE FUNCTION F2 (gamma) AT LOW Q**2

The TPC/Two Gamma collaboration Aihara, H. ; Alston-Garnjost, M. ; Avery, R.E. ; et al.
Phys.Rev.Lett. 58 (1987) 97, 1987.
Inspire Record 233595 DOI 10.17182/hepdata.20136

The structure function F2γ for a quasireal photon has been measured in the reaction ee→eeX for Q2 in the range 0.20.1. Below Q2=0.3 GeV2, scaling breaks down in accordance with the finite cross-section bound for real photons.

4 data tables
Table 1

Data read from graph.

Table 2

Data read from graph.

Table 3

Data read from graph.

More…