OR K π 0 + µ + v ( µ ) M. (a) (i) quark antiquark pair OR qq OR named quark antiquark pair 0 (iii) us (b) (i) Weak any of the following also score mark: weak interaction weak interaction force weak nuclear weak nuclear interaction weak decay weak force weak nuclear force conserved: baryon number, charge, lepton number, spin not conserved: strangeness (iii) K π 0 + e + v (e) [9] M. (a) interaction exchange particle weak W + OR W OR Z electromagnetic photon OR γ (b) uud (c) (i) an atomic/orbital/shell electron interacts with a proton in the nucleus (via the weak interaction) PhysicsAndMathsTutor.com
neutron formed or u quark changes to d quark (and neutrino released) [9] M. (a) (i) Z 0 with the weak interaction gluons or pions with the strong nuclear force γ photons with electromagnetic interaction gravitons with gravity (any exchange particle () and corresponding interaction ()) transfers energy transfers momentum transfers force (sometimes) transfers charge any two ()() (b) p π 0 () V e e + µ () e + () pe + µ () [8] M. (a) baryon number 0 + = + 0 () lepton number 0 + 0 = 0 + 0 () charge 0 + = 0 + () PhysicsAndMathsTutor.com
(b) K () π + () p udu () correct number of quarks and antiquarks in each () [7] M5. (a) particle quark structure charge strangeness baryon number proton uud + 0 sigma + uus + - π + ud + 0 0 7 (b) (i) examples: proton, antiquarks (iii) consists of antiquarks same (rest) mass (energy) difference eg baryon number/charge [] M6. (a) (i) any two eg proton, neutron PhysicsAndMathsTutor.com
(b) (i) contains a strange quark or longer half life than expected or decays by weak interaction the second one is not possible because lepton number is not conserved (c) (i) weak (interaction) mention of charge conservation or charge conservation demonstrated by numbers (iii) X must be a baryon baryon number on right hand side is + (iv) proton/p [] M7. (a) (i) positron, neutron, neutrino, positive pion () () (if all correct) (lose ()for each error) electron, proton, negative muon () () (if all correct) (lose ()for each error) (b) (i) (µ ) e + + v µ () difference: mass or half-life or generation of lepton () similarity: both leptons or both negatively charged () (c) [0] PhysicsAndMathsTutor.com
M8. (a) (i) leptons do not experience the strong interaction but hadrons do or hadrons not fundamental/made of quarks and leptons are not () hadron eg proton, neutron, pion () lepton eg electron, neutrino () (iii) baryons () mesons () baryons made from three quarks (or antiquarks), mesons a quark, antiquark pair or baryons, baryon number is + or mesons 0 () (b) baryon number, lepton number, charge, strangeness, energy or momentum () demonstration of conservation (before and after considered and number appropriate to particle quoted) () [8] M9. (a) (i) particles that experience the strong (nuclear) force/interaction () particles composed of three quarks () (iii) particles composed of a quark and an antiquark () (b) similarity: but the same (rest) mass or rest energy () difference: opposite quantum states eg charge () (c) charge/c baryon number quark structure antiproton.6 0 9 for each error PhysicsAndMathsTutor.com 5
(d) (i) weak interaction () strange not conserved or there is a change/decay of quark (flavour) () any two eg charge baryon number (muon) lepton number [] M0. (a) (i) ; qqq; ()() (() for just two combinations) π + = () () (b) (i) strangeness = charge = baryon number = + lepton number = 0 ()()() if all correct lose one for each error the proton () [8] PhysicsAndMathsTutor.com 6
M. (a) n () p () v e () (b) (i) γ photon () γ is massless γ has infinite range γ does not carry charge ()() any two (c) (i) all properties/quantum numbers (e.g. charge, strangeness) are opposite () π () but the masses are the same () γ () () 5 [] M. (a) (i) (named force) from weak (nuclear), electromagnetic or gravity () uses a mediating/exchange particle, named particle from W (±) (boson), (γ) photon or graviton () to transfer energy/momentum () when electron emits/receives exchange particle, disappearance/creation of new particle occurs () anti proton () QWC max PhysicsAndMathsTutor.com 7
(b) (i) (quarks) () weak (nuclear) () (iii) proton () [7] PhysicsAndMathsTutor.com 8