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We propose and demonstrate that a gamma-gamma collider with W_gg < 12 GeV can be added to the European XFEL with a minimal disruption to its main program. High-energy photons will be obtained by Compton scattering of 0.5 micron laser…
The possibility of a photon collider extension to the beam dump of the $17.5$ GeV European XFEL has already been discussed before as the first high energy collider of its sort. It would not only be the first proof of concept and test of a…
The possibility of a Photon-Photon collider extension to the Beam dump of the $17.5$ GeV European XFEL has been discussed before as the first high energy collider of its sort. It would not just be to study the concept of photon colliders…
A high-brilliance ($\sim10^{24}$~photon.s$^{-1}$.mm$^{-2}$.mrd$^{-2}$/0.1\%) gamma-ray source experiment is currently being planned at Fermilab ($E_\gamma\simeq 1.1$~MeV)~[1]. The source implements a high-repetition-rate inverse Compton…
Possibility of PbPb$\to$PbPb$\gamma\gamma$ measurement at smaller (< 5 GeV) diphoton invariant mass will be presented. Analysis focuses only on ultraperipheral heavy-ion collisions. This estimate shows that the $\gamma \gamma \to \gamma…
It is very likely that in 3-4 years the construction of one or two linear colliders with c.m.s energy up to 0.5--1.5 TeV will be started. Besides e^+e^- collisions, linear colliders give a unique possibility to study gamma-gamma and…
Along with $\pi^0$ and $\eta$ mesons, a resonance structure in the invariant mass spectrum of two photons at $M_{\gamma\gamma}= 360 \pm 7 \pm 9$ MeV is observed in the reaction $d C\to\gamma + \gamma +X$ at momentum 2.75 GeV/c per nucleon.…
A high-energy lepton-lepton collider will give us a unique possibility to study e-gamma and gamma-gamma interactions at high energies. The high-energy photons can be generated by Compton back-scattering of laser light on the high-energy…
Results are presented of a search for heavy particles decaying into two photons. The analysis is based on a 19.7 inverse femtobarn sample of proton-proton collisions at sqrt(s) = 8 TeV collected with the CMS detector at the CERN LHC. The…
Due to coherence, there are strong electromagnetic fields of short duration in very peripheral collisions. They give rise to photon-photon and photon-nucleus collisions with a high flux up to an invariant mass region hitherto unexplored…
A search for diphoton resonances in the mass range between 10 and 70 GeV with the ATLAS experiment at the Large Hadron Collider (LHC) is presented. The analysis is based on $pp$ collision data corresponding to an integrated luminosity of…
A search for heavy, narrow resonances decaying to a Higgs boson and a photon (H$\gamma$) has been performed in proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$…
Searches for new resonances decaying into two photons in the ATLAS experiment at the CERN Large Hadron Collider are described. The analysis is based on proton--proton collision data corresponding to an integrated luminosity of 3.2 fb$^{-1}$…
We perform a detailed study of the process $e^+e^-\to\gamma\nu_l\bar\nu_l$ and its sensitivity to anomalous gauge boson couplings of the $\gamma WW$ vertex. We concentrate on LEP II energies, $\sqrt{s}=200$ GeV, and energies appropria- te…
In the relatively recent CMS data, there is a hint on the existence of a resonance with the mass 28 GeV coupling to muons. Such a resonance should also couple to photons through the fermion loop, therefore it can be searched for in…
We present a study of photon-photon scattering in the mass range $W_{\gamma\gamma} < 5$ GeV. We extend earlier calculations of this cross section for $W_{\gamma\gamma}>$ 5 GeV into the low mass range where photoproduction of the…
The construction of two electron linacs and an optical FEL system is proposed. This facility, which would serve primarily as a Higgs-boson collider factory, could be built in two stages, each with distinct physics objectives requiring…
A high energy photon collider (gamma-gamma, gamma-electron) based on backward Compton scattering of laser light is a very natural supplement to e+e- a linear collider and can significantly enrich the physics program. The region below about…
The cross section of atomic electron Compton scattering $\gamma + e \rightarrow \gamma^\prime + e^\prime $ was measured in the 4.40--5.475 GeV photon beam energy region by the {\em PrimEx} collaboration at Jefferson Lab with an accuracy of…
Methods of gamma-gamma, gamma-electron luminosities measurement at photon colliders based on Compton scattering of laser photons on high energy electrons at linear colliders are considered.