A survey of W pair production through the two-photon process

Possibility of measuring the magnetic moment of theWboson at heavy-ion colliders

“…The photonic production cross section 6 ( y y -W + W-1 is very well known [12]: with r r M & / 5 . Note that 6-8.rra2/M&=93 pb as 3w , and rises very fast above threshold.…”

Polarization observables for millicharged particles in photon collisions

“…The value of the gyromagnetic factor is set by requiring the unitarity of the theory at tree level [27], implying that all the consistent theories of spin-1 particles interacting with the EM field, such as the one in [8], necessarily yield this phenomenon. A tangible example of this characteristic asymptotic behavior is provided by the W pair production through photon-photon scatterings in the SM, γγ → W + W − , where g W = 2 and σ s→∞ (W W ) = 8πα 2 m 2 W = 80.8 pb, with m W the W ± mass, while for α the low energy value should be used [11,12]. We stress that this is a general behavior of interacting spin-1 gauge theories based on non-Abelian gauge groups [8], which is also manifest in the pure gluon-gluon scatterings of QCD.…”

“…Such a distinguishing characteristic of spin-1 interactions is manifest in the SM, where the tree-level total cross section for γγ → W + W − approaches a constant of about 80 pb at high energies [9][10][11], while radiative corrections are typically of order 10% [12]. This property, resulting from a collinear effect of the W propagator in the t-channel production mechanism, has a general validity and also holds for the analogous production of two spin-1 MCP [8].…”

Dark matter and spin-1 milli-charged particles

“…However, the case of spin-1 MCP, V µ , presents and intriguing feature: as a result of the interplay between gauge interactions and unitarity, the total cross section of γγ → V V tends to a constant in the high energy limit, whereas the same quantity decreases as s −1 in the cases of spin-0 and spin-1/2 MCP. Such distinguishing characteristic of spin-1 interactions is manifest in the SM, where the tree-level total cross section for γγ → W + W − approaches a constant of about 80 pb at high energies [13][14][15], while radiative corrections are typically of order 10% [16].…”

“…The possible relevance of the latter stems from its constant behaviour in the high energy limit: even if this process is of higher order in , the corresponding cross section does not present the typical 1/s suppression at high energies, therefore this channel dominates the V ± production as long as the reheating temperature is considerably higher than m V . The corresponding thermal average is then given by 15) and by supposing that the MCP have a vanishing initial abundance and are produced only via the inverse annihilations, we obtain a relic abundance of…”