Soft-photon radiation in high-energy proton-proton collisions within the tensor-Pomeron approach: Bremsstrahlung

Abstract

We discuss diffractive processes in proton-proton collisions at small momentum transfers without and with photon radiation. We consider the soft exclusive reactions $pp\to pp$, $p\bar{p}\to p\bar{p}$, and $pp\to pp\gamma$ within the tensor-pomeron and vector-odderon approach. We compare our results with the data for $pp$ and $p\bar{p}$ total cross sections, for the ratio of real to imaginary part of the forward scattering amplitude, and for the elastic $pp$ cross sections, especially those from TOTEM. To describe the low-energy data more accurately the secondary reggeons must be included. We write down the amplitudes for the photon bremsstrahlung in high-energy proton-proton collisions using the tensor-pomeron model. These results are relevant for the c.m. energies presently available at the Relativistic Heavy Ion Collider and at the LHC. We present predictions for the proposed measurements of soft photons with the planned future upgrade of the ALICE experiment at the LHC. We investigate the limits of applicability of the soft-photon approximation (SPA) based on Low's theorem. The corresponding SPA results are compared to those obtained from our complete model. The regions of phase space are given quantitatively where SPA and our complete tensor-pomeron results are close to each other. As an example, let $k_{\perp }$, $\mathrm{y}$, and $\omega$, be the absolute value of the transverse momentum, the rapidity, and the energy of the photon, respectively, in the overall c.m. system. For the region $1\mathrm{MeV}<k_{\perp }<100\mathrm{MeV}$ and $3.5<|y|<5.0$, we find that the SPA Ansatz with only the pole terms $\propto {\omega }^{-1}$ agrees at the percent level with our complete model result up to $\omega \cong 2$ GeV.

44 pages, 18 figures, Comments on the photon radiation in connection with diffractive excitation of the proton were added

References in corpus (17)

• Low's Subleading Soft Theorem as a Symmetry of QED
• Low-Energy Behavior of Gluons and Gravitons from Gauge Invariance
• Measurement of Elastic pp Scattering at $\sqrt{s}$ = 8 TeV in the Coulomb-Nuclear Interference Region - Determination of the $\rho$-Parameter and the Total Cross-Section
• Comparison of $pp$ and $p\bar{p}$ differential elastic cross sections and observation of the exchange of a colorless $C$-odd gluonic compound
• Single Spin Asymmetry $A_N$ in Polarized Proton-Proton Elastic Scattering at $\sqrt{s}=200$ GeV
• Helicity in Proton-Proton Elastic Scattering and the Spin Structure of the Pomeron
• Evidence for an Excess of Soft Photons in Hadronic Decays of Z^0
• Dark Sector Production via Proton Bremsstrahlung
• Photoproduction of pi+ pi- pairs in a model with tensor-pomeron and vector-odderon exchange
• Central exclusive diffractive production of $K^{+}{K}^{-}{K}^{+}{K}^{-}$ via the intermediate $\varphi \varphi$ state in proton-proton collisions
• Observation of the Muon Inner Bremsstrahlung at LEP1
• Elastic and diffractive scattering in the LHC era
• Searching for the odderon in $pp\to pp{K}^{+}{K}^{-}$ and $pp\to pp{\mu }^{+}{\mu }^{-}$ reactions in the $\varphi (1020)$ resonance region at the LHC
• High-energy $\pi \pi$ scattering without and with photon radiation
• Forward Physics at the LHC, Detecting Elastic pp Scattering by Radiative Photons
• Lack of evidence for an odderon at small t
• High-energy elastic diffractive scattering of nucleons in the framework of the two-Reggeon eikonal approximation (from U-70 to LHC)

Cited by in corpus (2)

• On the question of quark confinement in the Abelian U(1) QED gauge interaction
• Dynamics of quarks and gauge fields in the lowest-energy states in QCD and QED