The Structure of the Proton Phenomenology

Abstract

Deep inelastic scattering of an electron on a proton is a very interesting process to probe with high precision the structure of the proton. In deep inelastic scattering a highly virtual photon of mass Q ² interacts with pointlike constituents (partons) of the proton. In the Breit frame the photon carries no energy and the proton has a momentum P proportionnai to EquationSource$$% MathType!MTEF!2!1!+- % feaagCart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaOaaaeaaca % WGrbWaaWbaaSqabeaacaaIYaaaaaqabaaaaa!37C3!]]</EquationSource><EquationSource Format="TEX"><![CDATA[$$ \sqrt {{Q^2}} $$. For high Q ², P is large and the proton looks like a highly contracted pancake. The time τ of interaction is proportional to EquationSource% MathType!MTEF!2!1!+- % feaagCart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaaca % aIXaaabaWaaOaaaeaacaWGrbWaaWbaaSqabeaacaaIYaaaaaqabaaa % aaaa!388E!]]</EquationSource><EquationSource Format="TEX"><![CDATA[$$ \frac{1}{{\sqrt {{Q^2}} }} $$ ; for small τ we can safely suppose that the proton scatters incoherently on each parton. The cross section for deep inelastic scattering depends on the parton distribution seen when we look inside the proton with a resolution time τ.

talk given at the CARGESE summer school on “Masses of fundamental particles” (5–17 August 1996) / ²⁾DGLAP stands for Dokshitzer, Gribov, Lipatov, Altarelli, Parisi