QUARK WORKBENCH TEACHER NOTES

Transcription

1 QUARK WORKBENCH TEACHER NOTES DESCRIPTION Stents se cleverly constrcte pzzle pieces an look for patterns in how those pieces can fit together. The pzzles pieces obey, as mch as possible, the Stanar Moel s rles limiting the qark composition of bon states, both baryons an mesons. We provie a template that allows yo to ct ot the pzzle pieces an a workbench that stents can se for assembly. STANDARDS National Science Ecation Stanars (U.S. National Research Concil) Unifying Concepts an Processes: As a reslt of this activity... stents shol evelop nerstaning an abilities aligne with the following concepts an process: o Systems, orer an organization o Evience, moels an explanation Physical Science Content Stanar B: As a reslt of this activity... stents shol evelop an nerstaning of: o Strctre an properties of matter. LEARNING OBJECTIVES As a reslt of this activity, stents will know an be able to: Ientify the fnamental particles in the Stanar Moel chart. Describe properties of qarks, incling color, spin, an charge. Describe the role of qarks informing particles that are part of the Stanar Moel. State the rles for combining qarks to make mesons an baryons. PRIOR KNOWLEDGE None BACKGROUND MATERIAL As an introction to the Stanar Moel, stents will work with pzzle pieces that obey, as mch as possible, the Stanar Moel s rles limiting the qark composition of bon states, both baryons an mesons. Specifically, these bon states mst be color netral: re-- (or anti-re, anti- an anti-) for the three qark harons, while the two qarks comprising a meson mst be either re with anti-re, with anti-, or with anti. The qark pzzle pieces o follow these rles, forming close, soli figres for allowe bon states, while stbbornly refsing to fit together for forbien combinations. Given a set of qark pieces an some time to attempt to maniplate them into bon states, stents shol be able to recognize certain restrictions on what is allowe. This activity ens with a brief iscssion of the Stanar Moel as the crrent theoretical framework for or nerstaning of matter an the Stanar Moel chart, which incles the basic biling blocks qarks, leptons an force carriers. Some rles that stents shol iscover : Antiqarks always possess an anti-color.

2 All baryons consist of three qarks or of three antiqarks. The three qarks making p each baryon mst consist of the three primary colors: re, an, or the three anti-colors: anti- (yellow), anti- (magenta) or anti-re (cyan). All mesons consist of two qarks: one qark an an antiqark. The two qarks in any meson mst possess a color an its anti-color. All harons posses a total charge of -2, -1, 0, +1, or +2. All mesons posses a total charge of -1, 0, or +1. Some limitations of the qark pzzle pieces: Of corse, qarks are not shape like the pzzle pieces; nor o they possess tre colors. Neither leptons (incling electrons) nor WEAK interactions can be escribe by these pieces. The glons which bin the qarks into the ncles are also not represente. The qark pieces cannot escribe any of nmeros known particles fon in sperpositions, sch as the π 0, a sperposition of an. IMPLEMENTATION Project the Stanar Moel Chart of Elementary Particles (fon at an iscss the generations, ifference between leptons, qarks an force carriers. (Yo can fin some material to prompt this iscssion at Point ot the large ifference in masses between the qarks (this will foreshaow the next activity in this packet) an the fact that the only massless particle on the chart is the photon. Discss the fact that the particles here represent the biling blocks of natre everything else in the niverse is comprise of these particles. Everything. Point ot that that the familiar proton is comprise of three valence qarks (p-p-own) an many other virtal qark pairs an glons. Introce the Qark Workbench activity as a way to etermine the combination rles for the qarks as they form composite particles. A few important points: 1. The Stanar Moel chart illstrate the fnamental biling blocks of matter an the force carriers that govern their interactions with one another. 2. It is srprising that only the p an own qarks an the electron make p all the orinary matter aron s. 3. Once we nerstan the rles for combining these fnamental particles, we can make hnres of other particles. 4. The Stanar Moel, sally illstrate by the Stanar Moel chart is, of corse, mch more than the chart an is the crrent theoretical framework for or nerstaning of matter. We recommen printing the pzzle pieces (the following pages) on car stock an laminating game boars.

3 ASSESSMENT Dring the activity, yo might ask: What color are all of the bon states that yo have iscovere? What is the net charge of the bon states that yo have iscovere? How many bon qarks are reqire to make a meson? A baryon? When the stents have finishe the activity, project the Elementary Particles chart again. Discss the fact that they have investigate a small part of the Stanar Moel one that escribes formation of baryons an mesons. There is more to learn abot the Stanar Moel both for the stents an for physicists. What rles i yo iscover that etermine the composition of baryons? Mesons? What role i qarks play in forming the mesons an baryons? In aition to qarks, what other particles are fnamental? What o physicists call the crrent theoretical framework for or nerstaning of matter? ADDITIONAL INFORMATION The proton an netron are baryons. As an extension to the activity, ask the stents to etermine the possible qark combinations to constrct these particles that they are aware of. Remin the stents that protons an netrons are matter (they col also make antiprotons an antinetrons), an iscss the reslts. 1. Proton: 2. Netron: 3. Antiproton: () 4. Constrct the pion family: π + () ; π (); an π 0 () or (). Yo may wish to iscss that each π 0 is known to be a sperposition of those two states. Variations: Print an ct ot an excess of p an own qarks, in orer to sggest that all qark types are not eqally prevalent; in fact, the other qark types are qite rare in the niverse we are se to. Use the qarks in a game similar to gin rmmy. Each player starts with ten qark pieces; the object of the game is for a player to be the first to se p all of their ten pieces by biling several composite particles (baryons or mesons). Players take trns, each trying to evelop ONE particle only one per trn is allowe. If a particle is constrcte,

4 it an its qark constitents leave the player s han an remain on the table for the remainer of the game. If nwilling or nable to form a particle, the player mst select a ranom qark from a stockpile an wait a trn to constrct. Eric Gettrst is a physics teacher in Maison, Wisconsin. He create this pzzle activity for his stents in the smmer of 2008 after a smmer appointment as a QarkNet Lea Teacher in the physics epartment at the University of Wisconsin. He pblishe the iea in The Physics Teacher ring the spring of 2010.

5 MESON WORKBENCH BUILD MESONS HERE BARYON WORKBENCH BUILD BARYONS HERE Qark pieces mst fit together like pzzle pieces: no overlapping. There mst be no empty spots on the insie of the particle forme: ALLOWED ALLOWED FORBIDDEN FORBIDDEN

6 re re re re TEACHER: Ct ot each Qark pzzle piece beforehan. Each will be one color (or anti-color). Discar the white ots. Car stock will make better pieces than plain white paper. Recommenation: Print ot many extra copies of this page, to help represent that p an own qarks comprise the particles common to or experience. QUARK PIECES pg. 1 of 3

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8 t t b b s s 2 3 t t b b s s 2 3 TEACHER: Ct ot each Qark pzzle piece beforehan. Each will be one color (or anti-color). Discar the white ots. QUARK PIECES pg. 3 of 3