We review current results on physics with photons at the LHC and discuss realistic perspectives of photon physics at future colliders. In particular, we focus on Standard Model (SM) measurements with photons at the upcoming high-luminosity and a possible high-energy LHC as well as jet measurements at an Electron-Ion Collider (EIC) to be constructed either at BNL or at JLAB and their potential to constrain nuclear parton densities. We also discuss future searches for physics beyond the SM with photons in the high-luminosity phase of the LHC.
The perspectives for measuring the top quark and the Higgs boson in nuclear collisions at the LHC and Future Circular Collider (FCC) are summarized. Perturbative QCD calculations at (N)NLO accuracy, including nuclear parton distribution functions, are used to determine their cross sections and visible yields after standard analysis cuts in PbPb and pPb collisions at the LHC ($\sqrt{s_{NN}}$ = 5.5, 8.8 TeV) and FCC ($\sqrt{s_{NN}}$ = 39, 63 TeV). In their "cleanest" decay channels, $\rm t\bar{t}\to b\bar{b} 2 \ell 2ν$ and $\rm H\to γγ, 4\ell$, about 10$^3$ ($10^5$) top-quark and 10 (10$^3$) Hig…
We use an event-by-event hydrodynamical description of the heavy-ion collision process with Glauber initial conditions to calculate the thermal emission of photons. The photon rates in the hadronic phase follow from a spectral function approach and a density expansion, while in the partonic phase they follow from the AMY perturbative rates. The calculated photon elliptic flows are lower than those reported recently by both the ALICE and PHENIX collaborations.
Motivated by the recent LHC discovery of the di-photon excess at the invariant mass of ~ 750 GeV, we study the prospect of investigating the scalar resonance at a future photon-photon collider. We show that, if the di-photon excess observed at the LHC is due to a new scalar boson coupled to the standard-model gauge bosons, such a scalar boson can be observed and studied at the photon-photon collider with the center-of-mass energy of ~ 1 TeV in large fraction of parameter space.
Two photon collisions offer a variety of physics studies that can be performed at the future electron-positron colliders. Using the planned CEPC parameters as a benchmark we consider several topics to be studied in the two-photon collisions. With the full integrated luminosity the Higgs boson photoproduction can be reliably observed. A large statistics of various quarkonium states can be collected. The LEP results on the photon structure function and the tau lepton anomalous magnetic moment can be improved by 1-2 orders of magnitude.
We discuss a photon collider based on the $e^+e^-$ \ linear collider with energies of $2E = 1÷2$ TeV in cms (ILC, CLIC, ...). Previously, this energy range was considered hopeless for the experiment in the foreseeable future. We discuss the realization of the TeV PLC based on modern lasers. A small modification of the laser-optical system prepared for the photon collider with energy of $E \approx 250$ GeV will be sufficient if the parameters are chosen optimally. The high-energy part of the photon spectrum does not depend on design details and is well separated from the low-energy part. That i…
Equivalent photon approximation is used to calculate fiducial cross sections for dimuon production in ultraperipheral proton-proton and lead-lead collisions. Analytical formulae taking into account experimental cuts are derived. The results are compared with the measurements reported by the ATLAS collaboration.
We propose a three-beam stimulated resonant photon collider with focused laser fields in order to directly produce an axion-like particle (ALP) with the two beams and to stimulate its decay by the remaining one. The expected sensitivity around the eV mass range has been evaluated. The result shows that the sensitivity can reach the ALP-photon coupling down to $\mathcal{O}(10^{-14})$ GeV${}^{-1}$ with 1 J class short-pulsed lasers.
We study the decay of the $Z$ vector boson into a photon and a massless (invisible) dark photon in high-energy collisions. The photon can be used as trigger for the event, while the dark photon is detected indirectly as missing momentum in the event final state. We investigate the possibility of searching for such a dark photon at the LHC, HL-LHC and future lepton colliders, and compare the respective sensitivities. As expected, the best result is found for the lepton colliders running at the $Z$ mass, FCC-ee and CEPC, with a final sensitivity to branching ratios of order $O(10^{-11})$. We als…
We show that the evolution of interacting massive particles in the de Sitter bulk can be understood at leading order as a series of resonant decay and production events. From this perspective, we classify the cosmological collider signals into local and nonlocal categories with drastically different physical origins. This further allows us to derive a cutting rule for efficiently extracting these cosmological collider signals in an analytical fashion. Our cutting rule is a practical way for extracting cosmological collider signals in model building, and can be readily implemented as symbolic c…
We studied the feasibility of observing light-by-light scattering in a photon-photon collider based on an existing accelerator complex and a commercially available laser system. We investigated the statistical significance of the signal over the QED backgrounds through a Monte Carlo simulation with a detector model. The study showed that light-by-light scattering can be observed with a statistical significance of 8 to 10 sigma in a year of operation, depending on the operating conditions.
Motivated by the ATLAS and CMS announcements of the excesses of di-photon events, we discuss the production and decay processes of di-photon resonance at future $e^+e^-$ colliders. We assume that the excess of the di-photon events at the LHC is explained by a scalar resonance decaying into a pair of photons. In such a case, the scalar interacts with standard model gauge bosons and, consequently, the production of such a scalar is possible at the $e^+e^-$ colliders. We study the production of the scalar resonance via the associated production with photon or $Z$, as well as via the vector-boson …
Photon Colliders in Physical Program for Large Colliders. Talk given at Workshop on Electromagnetic Probes of Fundamental Physics, Eriche, Sicily, 16-21 October 2001
For the first time, the production of a massive dark photon (DP) in the $γe^-$ scattering at the future lepton colliders ILC, CLIC, and CEPC is examined. The invisible decay mode of the DP is addressed. We have studied both the unpolarized scattering and the collision of the Compton backscattered photons with the polarized electron. The missing energy distributions are shown. We have considered the wide range 10 GeV -- 1000 GeV of the DP mass $m_{A'}$. The excluded regions at the 95\% C.L. in the plane $(\varepsilon, m_{A'})$, where $\varepsilon$ is the kinetic mixing parameter, are obtained.
