charm decays with photons in the final state and trigger counter ...

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charm decays with photons in the final state and trigger counter ...

10quantity in a reaction or decay is conserved if its original value remains the same afterthe process occurred. There are some physical quantities that are known to be conservedunder any physical process: energy, momentum, angular momentum and electric charge.The conservation of these parameters gives the notion of “conservation laws” in physics.A conservation law states that the total value of some quantity, such as energy or electricalcharge, will be conserved in any process. Experiments in particle physics show that anydecay process that one can imagine will occur spontaneously unless it is forbidden by aconservation law. This means that the rules that define all decay processes are determinedby the conservations laws of some physical quantity.Table 1.4: Conservations lawsConserved quantity Strong Weak ElectromagneticInteraction Interaction InteractionEnergy/Momentum yes yes yesCharge yes yes yesBaryon number yes yes yesLepton number yes yes yesI (isospin) yes no noS (strangeness) yes no yesC (charm) yes no yesP (parity) yes no yesC (charge-conjugation parity) yes yes yesCP yes no yesCPT yes yes yesIn particle physics other quantities had been experimentally identified that areconserved in addition to the ones mentioned before such as energy, angular momentum,and spin (see table 1.4).Sometimes processes that were forbidden by some of theseempirical conservation laws are found, but because this forbidden process appears rarely on

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