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Cross-section Formulae for Specific Processes
| Content Provider | Semantic Scholar |
|---|---|
| Author | Baer, Howard Cahn, Robert |
| Abstract | Setting aside leptoproduction (for which, see Sec. 16 of this Review), the cross sections of primary interest are those with light incident particles, where g and q represent gluons and light quarks. The produced particles include both light particles and heavy ones-t, W , Z, and the Higgs boson H. We provide the production cross sections calculated within the Standard Model for several such processes. Resonant cross sections are generally described by the Breit-Wigner formula (Sec. 16 of this Review). where E is the c.m. energy, J is the spin of the resonance, and the number of polarization states of the two incident particles are 2S 1 + 1 and 2S 2 + 2. The c.m. momentum in the initial state is k, E 0 is the c.m. energy at the resonance, and Γ is the full width at half maximum height of the resonance. The branching fraction for the resonance into the initial-state channel is B in and into the final-state channel is B out. For a narrow resonance, the factor in square brackets may be replaced by πΓδ(E − E 0)/2. The production of point-like, spin-1/2 fermions in e + e − annihilation through a virtual photon, e + e − → γ * → f f , at c.m. energy squared s is given by dσ dΩ = N c α 2 4s β 1 + cos 2 θ + (1 − β 2) sin 2 θ Q 2 f , (39.2) where β is v/c for the produced fermions in the c.m., θ is the c.m. scattering angle, and Q f is the charge of the fermion. The factor N c is 1 for charged leptons and 3 for quarks. In the ultrarelativistic limit, β → 1, σ = N c Q 2 f 4πα 2 3s = N c Q 2 f 86.8 nb s(GeV 2) 2. The cross section for the annihilation of a qq pair into a distinct pair q q through a gluon is completely analogous up to color factors, with the replacement α → α s. Treating all quarks as massless, averaging over the colors of the initial quarks and defining t = −s sin 2 (θ/2), u = −s cos 2 (θ/2), one finds [1] dσ dΩ (qq → q q) = α 2 9s t 2 + u 2 s 2 . |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://pdg.lbl.gov/2007/reviews/crosssecrpp.pdf |
| Alternate Webpage(s) | http://pdg.lbl.gov/2009/reviews/rpp2009-rev-cross-section-formulae.pdf |
| Alternate Webpage(s) | http://www.inp.nsk.su/pdg/2010/reviews/rpp2010-rev-cross-section-formulae.pdf |
| Alternate Webpage(s) | http://www.cern.ch/pdg/2009/reviews/rpp2009-rev-cross-section-formulae.pdf |
| Alternate Webpage(s) | http://www.inp.nsk.su/pdg/2009/reviews/rpp2009-rev-cross-section-formulae.pdf |
| Alternate Webpage(s) | http://www.inp.nsk.su/pdg/2007/reviews/crosssecrpp.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Boson sampling Charge (electrical) Color Cross section (geometry) Photons Polarization (waves) Resonance Spin-½ Supernumerary maxillary left central incisor Supernumerary maxillary right second premolar width |
| Content Type | Text |
| Resource Type | Article |
