A modeling study suggests that a future 10 TeV gamma-gamma collider would face a clear trade-off: near-optical lasers give higher predicted luminosity, while X-ray lasers produce a narrower high-energy peak. The result comes from scans of laser wavelength and pulse duration that account for pair production and photon angular divergence. The authors present both wavelength regions as possible operating choices, with near-optical light offering higher luminosity and a lower technological challenge.
The trade-off in the numbers
In the scan focused on the strict high-energy part of the spectrum, two operating points emerged. One used 5 eV laser photons, a 6 mm pulse and 125 J of laser pulse energy. The other used 1 keV photons, an 80 micrometer pulse and 1.7 J. Under those respective settings, predicted total gamma-gamma luminosity was 1.2 x 10^35 cm^-2 s^-1 for the 5 eV case and 1.8 x 10^34 cm^-2 s^-1 for the 1 keV case. The corresponding 5% partial luminosities were 1.3 x 10^34 and 5.3 x 10^33 cm^-2 s^-1. The near-optical setup therefore produced more collisions by both measures in this comparison, while the X-ray option used much less pulse energy.
What the model says about pair production
Pair production is the main limit the design is trying to manage. In the one-dimensional rate model, the surviving high-energy photon population was predicted to fall enough to reduce photon luminosity by about a factor of 10, with the reduction approaching a factor of 16 in the model's large-x limit. The calculation's representative case used 2.5 eV laser photons, a0 = 0.3 and 5 TeV electrons, reaching a maximum high-energy photon count of 0.3n0 at x = 191 and a maximum-time parameter of 0.8.
A second calculation provides a benchmark
To test that simplified picture, the researchers used a two-stage CAIN simulation. The first stage modeled laser conversion into electron, positron and photon beams. The second modeled their beam-beam collision at the interaction point and produced luminosity spectra for multiple collision channels. At x = 191, the conversion stage produced maxima of 0.14n0 for photons above the study's 0.95E0 threshold and 0.45n0 above 0.5E0. An adjusted one-dimensional estimate of approximately 0.12n0 for the stricter threshold was described as agreeing with CAIN.
The definition of high energy changes the answer
Higher-frequency lasers sharpened the high-energy gamma-gamma spectrum, but the reported comparisons associated that sharper peak with lower total luminosity. For a 1 keV scattering laser, the high-energy peak had a full width at half maximum of 75 GeV, a measure of how tightly the energies were clustered. Peaks from near-optical lasers were much broader.
The preferred wavelength also changed when the study widened its energy window. When the cutoff was set at ECoM > 0.8 x 2E0, the near-optical maximum shifted to 2.5 eV, the distinct keV optimum disappeared, and the 1 keV result became nearly six times smaller. The best wavelength was therefore tied to the energy range the collider was meant to emphasize.
Other beam settings also matter
The tested polarization settings altered the valuable top end of the spectrum. The -0.9 configuration produced the strongest high-energy gamma-gamma peak. Total luminosity was nearly unchanged compared with the +0.9 configuration, but 5% partial luminosity was six times larger at -0.9.
Laser intensity produced a less simple pattern. In the 5 eV sensitivity simulations, a0 values of 0.3, 0.4 and 0.5 produced comparable maxima. The maximum at a0 = 0.5 was reduced by nonlinear Compton effects, while a0 = 0.2 showed degradation related to pulse duration. The tested results favored moderate settings under the simulated conditions.
A design study, not a demonstrated machine
The comparison of collider modes put the trade-off in broader terms. The two gamma-gamma options dominated at the highest energies, while electron-positron and electron-electron options generated significantly more collisions overall. The abstract also says that the reported 250 nm near-optical and 1.25 nm X-ray cases retain enough secondary-pair luminosity for heavy-particle production rates beyond existing colliders. These remain computational projections from a hypothetical design, not experimental production or discovery results.
The document is arXiv preprint 2608.25137v1, dated 25 August 2026. Its authors conclude that a future 10 TeV gamma-gamma collider could use scattering lasers spanning near-optical to X-ray wavelengths, with near-optical systems offering higher luminosity and less technological challenge. Their conclusion concerns the range of simulated design choices described in the preprint.
Paper data and sources
Original title: Enhancing 10 TeV $γγ$-collider luminosity through scattering-laser wavelength selection in the presence of prolific electron-positron pair production
Authors: S. S. Bulanov, T. Barklow, C. Benedetti et al.
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-25
DOI: Not available
Original paper · Full text