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. C23 (1984) 223, 1984.
Inspire Record 199731 DOI 10.17182/hepdata.16320
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Measurement of exclusive $\rho^0 \rho^0$ production in two photon collisions at high $Q^{2}$ at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett. B568 (2003) 11-22, 2003.
Inspire Record 619620 DOI 10.17182/hepdata.48855

Exclusive rho rho production in two-photon collisions involving a single highly virtual photon is studied with data collected at LEP at centre-of-mass energies 89GeV < \sqrt{s} < 209GeV with a total integrated luminosity of 854.7pb^-1 The cross section of the process gamma gamma^* -> rho rho is determined as a function of the photon virtuality, Q^2 and the two-photon centre-of-mass energy, Wgg, in the kinematic region: 1.2GeV^2 < Q^2 < 30GeV^2 and 1.1GeV < Wgg < 3GeV.

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Inclusive $\pi^0$ and $K^0_{S}$ production in two photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett. B524 (2002) 44-54, 2002.
Inspire Record 563335 DOI 10.17182/hepdata.49800

The reactions ee->ee+pi0+X and ee->ee+K0s+X are studied using data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 202 GeV. Inclusive differential cross sections are measured as a function of the particle transverse momentum pt and the pseudo-rapidity. For pt &lt; 1.5 GeV, the pi0 and K0s differential cross sections are described by an exponential, typical of soft hadronic processes. For pt > 1.5 GeV, the cross sections show the presence of perturbative QCD processes, described by a power-law. The data are compared to Monte Carlo predictions and to NLO QCD calculations.

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Production of $\pi^0 \pi^0$ and $\pi^0 \eta$ in Photon - Photon Collisions

Edwards, C. ; Partridge, Richard ; Peck, C. ; et al.
Phys.Lett. B110 (1982) 82-86, 1982.
Inspire Record 168793 DOI 10.17182/hepdata.30959
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A Measurement of $\pi^0 \pi^0$ Production in Two Photon Collisions

The Crystal Ball collaboration Marsiske, H. ; Antreasyan, D. ; Bartels, H.W. ; et al.
Phys.Rev. D41 (1990) 3324, 1990.
Inspire Record 294492 DOI 10.17182/hepdata.22923
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$\Lambda$ and $\Sigma^0$ pair production in two photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett. B536 (2002) 24-33, 2002.
Inspire Record 585621 DOI 10.17182/hepdata.48892

Strange baryon pair production in two-photon collisions is studied with the L3 detector at LEP. The analysis is based on data collected at e+e- centre-of-mass energies from 91 GeV to 208 GeV, corresponding to an integrated luminosity of 844 pb-1. The processes gamma gamma -> Lambda Anti-lambda and gamma gamma -> Sigma0 Anti-sigma0 are identified. Their cross sections as a function of the gamma gamma centre-of-mass energy are measured and results are compared to predictions of the quark-diquark model.

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Study of $\pi^0$ pair production in single-tag two-photon collisions

The Belle collaboration Masuda, M. ; Uehara, S. ; Watanabe, Y. ; et al.
Phys.Rev. D93 (2016) 032003, 2016.
Inspire Record 1390112 DOI 10.17182/hepdata.71443

We report a measurement of the differential cross section of π0 pair production in single-tag two-photon collisions, γ*γ→π0π0, in e+e- scattering. The cross section is measured for Q2 up to 30  GeV2, where Q2 is the negative of the invariant mass squared of the tagged photon, in the kinematic range 0.5  GeV<W<2.1  GeV and |cosθ*|<1.0 for the total energy and pion scattering angle, respectively, in the γ*γ center-of-mass system. The results are based on a data sample of 759  fb-1 collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The transition form factor of the f0(980) and that of the f2(1270) with the helicity-0, -1, and -2 components separately are measured for the first time and are compared with theoretical calculations.

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High-statistics study of $K^0_S$ pair production in two-photon collisions

The Belle collaboration Uehara, S. ; Watanabe, Y. ; Nakazawa, H. ; et al.
PTEP 2013 (2013) 123C01, 2013.
Inspire Record 1245023 DOI 10.17182/hepdata.62221

We report a high-statistics measurement of the differential cross section of the process gamma gamma --> K^0_S K^0_S in the range 1.05 GeV <= W <= 4.00 GeV, where W is the center-of-mass energy of the colliding photons, using 972 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider operated at and near the Upsilon-resonance region. The differential cross section is fitted by parameterized S-, D_0-, D_2-, G_0- and G_2-wave amplitudes. In the D_2 wave, the f_2(1270), a_2(1320) and f_2'(1525) are dominant and a resonance, the f_2(2200), is also present. The f_0(1710) and possibly the f_0(2500) are seen in the S wave. The mass, total width and product of the two-photon partial decay width and decay branching fraction to the K bar{K} state Gamma_{gamma gamma}B(K bar{K}) are extracted for the f_2'(1525), f_0(1710), f_2(2200) and f_0(2500). The destructive interference between the f_2(1270) and a_2(1320) is confirmed by measuring their relative phase. The parameters of the charmonium states chi_{c0} and chi_{c2} are updated. Possible contributions from the chi_{c0}(2P) and chi_{c2}(2P) states are discussed. A new upper limit for the branching fraction of the P- and CP-violating decay channel eta_c --> K^0_S K^0_S is reported. The detailed behavior of the cross section is updated and compared with QCD-based calculations.

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Measurement of eta-prime (958) formation in two photon collisions at LEP-1

The L3 collaboration Acciarri, M. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett. B418 (1998) 399-410, 1998.
Inspire Record 447945 DOI 10.17182/hepdata.47406
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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 F**gamma(2,c)

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Akesson, P.F. ; et al.
Eur.Phys.J. C16 (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<p_t<12GeV and \eta<1.5. They are compared to next-to-leading order (NLO) perturbative QCD calculations. The total cross-section for the process (e+e- to e+e-ccbar), where the charm quarks are produced in the collision of two quasi-real photons, is measured to be 842+-97(stat)+-75(syst)+-196(extrapolation)pb. A first measurement of the charm structure function F2 of the photon is performed in the kinematic range 0.0014<x<0.87 and 5<Q^2<100 GeV^2, and the result is compared to a NLO perturbative QCD calculation.

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Inclusive Jet Production in Photon-Photon Collisions at s(ee)**(1/2) from 189 to 209-GeV

The OPAL collaboration
Phys.Lett. B658 (2008) 185-192, 2008.
Inspire Record 754316 DOI 10.17182/hepdata.48798

Inclusive jet production (e+e- -> e+e- +jet+X) is studied in collisions of quasi-real photons radiated by the LEP beams at e+e- centre-of-mass energies sqrt see from 189 to 209 GeV. Jets are reconstructed using the kp jet algorithm. The inclusive differential cross-section is measured as a function of the jet transverse momentum, ptjet, in the range 5 <ptjet < 40 GeV for pseudo-rapidities, etaj, in the range -1.5 < etaj < 1.5. The results are compared to predictions of perturbative QCD in next-to-leading order in the strong coupling constant.

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Measurement of isolated prompt photon production in photon photon collisions at s(ee)**(1/2) = 183 GeV - 209-GeV

The OPAL collaboration
Eur.Phys.J. C31 (2003) 491-502, 2003.
Inspire Record 619533 DOI 10.17182/hepdata.48831

For the first time at LEP the production of prompt photons is studied in the collisions of quasi-real photons using the OPAL data taken at e+e- centre-of-mass energies between 183 GeV and 209 GeV. The total inclusive production cross-section for isolated prompt photons in the kinematic range of photon transverse momentum larger than 3.0 GeV and absolute photon pseudorapidity less than 1 is determined to be 0.32 +- 0.04 (stat) +- 0.04 (sys) pb. Differential cross-sections are compared to the predictions of a next-to-leading-order (NLO) calculation.

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Dijet production in photon-photon collisions at $S^{(1/2)}$ (ee) = 161-GeV and 172-GeV

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Alexander, G. ; et al.
Eur.Phys.J. C10 (1999) 547-561, 1999.
Inspire Record 474009 DOI 10.17182/hepdata.49386

Di-jet production is studied in collisions of quasi-real photons radiated by the LEP beams at e+e- centre-of-mass energies 161 and 172 GeV. The jets are reconstructed using a cone jet finding algorithm. The angular distributions of direct and double-resolved processes are measured and compared to the predictions of leading order and next-to-leading order perturbative QCD. The jet energy profiles are also studied. The inclusive two-jet cross-section is measured as a function of transverse energy and rapidity and compared to next-to-leading order perturbative QCD calculations. The inclusive two-jet cross-section as a function of rapidity is compared to the prediction of the leading order Monte Carlo generators PYTHIA and PHOJET. The Monte Carlo predictions are calculated with different parametrisations of the parton distributions of the photon. The influence of the `underlying event' has been studied to reduce the model dependence of the predicted jet cross-sections from the Monte Carlo generators.

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Dijet production in photon-photon collisions at s(ee)**(1/2) from 189-GeV to 209-GeV

The OPAL collaboration
Eur.Phys.J. C31 (2003) 307-325, 2003.
Inspire Record 611415 DOI 10.17182/hepdata.49662

Di-jet producion is studied in collisions of quasi-real photons at e+e- centre- of-mass energies sqrt(s)ee from 189 to 209 GeV at LEP. The data were collected with the OPAL detector. Jets are reconstructed using an inclusive k_t clustering algorithm for all cross-section measurements presented. A cone jet algorithm is used in addition to study the different structure of the jets resulting from either of the algorithms. The inclusive di-jet cross-section is measured as a function of the mean transverse energy Etm(jet) of the two leading jets, and as a functiuon of the estimated fraction of the photon momentum carried by the parton entering the hard sub-process, xg, for different regions of Etm (jet). Angular distribution in di-jet events are measured and used to demonstrate the dominance of quark and gluon initiated processes in different regions of phase space. Furthermore the inclusive di-jet cross-section as a function of |eta(jet)| and |delta eta (jet)| is presented where eta(jet) is the jet pseudo-rapidity. Different regions of the xg+ -xg- -space are explored to study and control the influence of an underlying event. The results are compared to next-to-leading order perturbative QCD calculations and to the predictions of the leading order Monte Carlo generator PYTHIA.

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Inclusive jet production in photon-photon collisions at $\sqrt{s}$ = 130-GeV and 136-GeV

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Z.Phys. C73 (1997) 433-442, 1997.
Inspire Record 424635 DOI 10.17182/hepdata.47713
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Formation of Delta (980) and A2 (1320) in Photon-photon Collisions

The Crystal Ball collaboration Antreasyan, D. ; Aschman, D. ; Besset, D. ; et al.
Phys.Rev. D33 (1986) 1847, 1986.
Inspire Record 217547 DOI 10.17182/hepdata.23518
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Production of $K \bar{K}$ Pairs in Photon-photon Collisions and the Excitation of the Tensor Meson F-prime (1515)

The TASSO collaboration Althoff, M. ; Brandelik, R. ; Braunschweig, W. ; et al.
Phys.Lett. B121 (1983) 216-222, 1983.
Inspire Record 181468 DOI 10.17182/hepdata.30814
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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. C30 (2003) 145-158, 2003.
Inspire Record 631231 DOI 10.17182/hepdata.43218
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Measurement of exclusive rho+ rho- production in high-Q**2 two-photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett. B597 (2004) 26-38, 2004.
Inspire Record 654177 DOI 10.17182/hepdata.48589

Exclusive rho^+ rho^- production in two-photon collisions involving a single highly-virtual photon is studied with data collected at LEP at centre-of-mass energies 89 GeV &lt; \sqrt{s} &lt; 209 GeV with a total integrated luminosity of 854.7 pb^-1. The cross section of the process gamma gamma^* -> rho^+ rho^- is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 1.2 GeV^2 &lt; Q^2 &lt; 30 GeV^2 and 1.1 GeV &lt; W_gg &lt; 3 GeV. The \rho^+\rho^- production cross section is found to be of the same magnitude as the cross section of the process gamma gamma^* -> rho^0 rho^0, measured in the same kinematic region by L3, and to have similar W_gg and Q^2 dependences.

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A study of $\eta$ formation in photon-photon collisions at PEP

The TPC/Two Gamma collaboration Aihara, H. ; Alston-Garnjost, M. ; Armitage, J.C. ; et al.
Phys.Rev. D33 (1986) 844, 1986.
Inspire Record 217503 DOI 10.17182/hepdata.23508
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Analysis of the pi+ pi- pi+ pi- and pi+ pi0 pi- pi0 final states in quasi-real two-photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett. B638 (2006) 128-139, 2006.
Inspire Record 705125 DOI 10.17182/hepdata.48674

The reactions gamma gamma -> pi^+pi^-pi^+pi^- and gamma gamma -> pi^+pi^0pi^-pi^0 are studied with the L3 detector at LEP in a data sample collected at centre-of-mass energies from 161GeV to 209GeV with a total integrated luminosity of 698/pb. A spin-parity-helicity analysis of the rho^0 rho^0 and rho^+ rho^- systems for two-photon centre-of-mass energies between 1GeV and 3GeV shows the dominance of the spin-parity state 2+ with helicity 2. The contribution of 0+ and 0- spin-parity states is also observed, whereas contributions of 2- states and of a state with spin-parity 2+ and zero helicity are found to be negligible.

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Pion and Kaon Pair Production in Photon-Photon Collisions

The TPC/Two Gamma collaboration Aihara, H. ; Alston-Garnjost, M. ; Avery, R.E. ; et al.
Phys.Rev.Lett. 57 (1986) 404, 1986.
Inspire Record 228072 DOI 10.17182/hepdata.20204
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Muon pair and tau pair production in two photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett. B585 (2004) 53-62, 2004.
Inspire Record 645127 DOI 10.17182/hepdata.48801

The QED processes e^+ e^- -> e^+ e^- \mu^+ \mu^- and e^+ e^- -> e^+ e^- \tau^+ \tau^- are studied with the L3 detector at LEP using an untagged data sample collected at centre-of-mass energies 161 GeV < sqrt{s} < 209 GeV. The tau-pairs are observed through the associated decay of one tau into e\nu\nu and the other into \pi\pi\nu . The cross sections are measured as a function of sqrt{s}. For muon pairs, the cross section of the \gamma\gamma -> \mu^+\mu^- process is also measured as a function of the two-photon centre-of-mass energy for 3 GeV < W_{\gamma\gamma} < 40 GeV. Good agreement is found between these measurements and the O(\alpha^4) QED expectations. In addition, limits on the anomalous magnetic and electric dipole moments of the tau lepton are extracted.

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Study of inclusive strange-baryon production and search for pentaquarks in two-photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Eur.Phys.J. C49 (2007) 395-410, 2007.
Inspire Record 727262 DOI 10.17182/hepdata.51884

Measurements of inclusive production of the Lambda, Xi- and Xi*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections for Lambda and Xi- are measured as a function of the baryon transverse momentum, pt, and pseudo-rapidity, eta. The mean number of Lambda, Xi- and Xi*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4 GeV &lt; pt&lt; 2.5 GeV, |eta| &lt; 1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive production of the pentaquark theta+(1540) in two-photon collisions through the decay theta+ -> proton K0s is also presented. No evidence for production of this state is found.

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Measurement of Lepton and Pion Pair Production in Photon - Photon Collisions at Dci

Courau, A. ; Falvard, A. ; Haissinski, J. ; et al.
Phys.Lett. B96 (1980) 402-406, 1980.
Inspire Record 153776 DOI 10.17182/hepdata.49087
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