PHYS 420: Astrophysics & Cosmology

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1 PHYS 420: Astrophysics & Cosmology

2 Dr Richard H. Cyburt Assistant Professor of Physics My office: 402c in the Science Building My phone: (304) My My webpage: In person or is the best way to get a hold of me.

3 My Office Hours TR 5:30-17:00am W 5:00-6:00pm Meetings may also be arranged at other times, by appointment

4 Midterm 1 Thurs. Feb 9, 4-5:15pm Cosmic Perspective & Scientific Method(s) History & development of Modern Science & Cosmology Information from Light Building Blocks of the Universe Review Wed. Feb 8, 7-9pm

5 Homework (Extended to Thu, Feb 9) Homework (Turn in before exam): From all we have discussed so far, think of questions and topics you are particularly very interested in. Pick 2 questions or topics you are interested in and would like to use for a possible project. Write a paragraph or two on why you are interested and the kinds of question you have or hope to address. What experiments and/or observations do you think are relevant? You will be researching these topics, not explicitly performing expts.

6 Douglas Adams Hitchhiker s Guide to the Galaxy

7 Radiation & Particles RADIATION Electromagnetic Visible light Heat rays = infared Chemical rays = ultraviolet X-rays Gamma rays Weak b-rays Strong a-rays, fission PARTICLES Electron (e " ) Positron (e # ) Proton (p) Negatron or Anti-proton (p ) Neutron (n) anti-neutron (n') Muon (μ ± ) neutrinoss (n) Pion (π ±, π, ) Kaon (K ±, K, ) Lambda (Λ, ) Delta ( ##, #,,, " )

8 Particles LEPTONS (NO, STRONG INTERACTION) Electrons Muons Neutrinos HADRONS (YES, STRONG INTERACTION) Proton (p) anti-proton (p ) Neutron (n) anti-neutron (n') Pion (π ±, π, ) Kaon (K ±, K, ) Lambda (Λ, ) Delta ( ##, #,,, " )

9 Hadrons MESONS (LIGHTER THAN PROTON) Pion (π ±, π, ) Kaon (K ±, K, ) BARYONS (= OR HEAVIER THAN PROTON) Proton (p) anti-proton (p ) Neutron (n) anti-neutron (n') Lambda (Λ, ) Delta ( ##, #,,, " )

10 Mesons (Lighter than Proton) Pion (π ±, π, ) Kaon (K ±, K, ) Bosons = whole-integer spin (intrinsic angular momentum)

11 Baryons (= or heavier than proton) Proton (p) anti-proton (p ) Neutron (n) anti-neutron (n') Lambda (Λ, ) Delta ( ##, #,,, " ) Fermions = half-integer spin (intrinsic angular momentum)

12 Let s organize what we see (spin 3/2 baryons) Mass X 0 X MeV/c 2 S + S 0 S MeV/c 2 D ++ D + D 0 D MeV/c 2 Charge

13 Let s organize what we see (spin 3/2 baryons) Mass X 0 X MeV/c 2 S + S 0 S MeV/c 2 D ++ D + D 0 D MeV/c 2 Charge

14 Let s organize what we see (spin 3/2 baryons) Mass X 0 X MeV/c 2 ~150 MeV/c 2 S + S 0 S MeV/c 2 ~150 MeV/c 2 D ++ D + D 0 D MeV/c 2 Charge

15 Let s organize what we see (spin 3/2 baryons) 1685 MeV/c 2 ~150 MeV/c 2 Mass X 0 X MeV/c 2 ~150 MeV/c 2 S + S 0 S MeV/c 2 ~150 MeV/c 2 D ++ D + D 0 D MeV/c 2 Charge

16 Let s organize what we see (spin 3/2 baryons) W MeV/c MeV/c 2 Mass X *0 X * MeV/c 2 S *+ S *0 S * MeV/c 2 D ++ D + D 0 D MeV/c 2 Charge

17 Let s organize what we see (spin 1/2 baryons) Mass X 0 X MeV/c 2 ~200MeV/c MeV/c 2 L MeV/c 2 S + S 0 S - p n 940 MeV/c 2 ~200MeV/c 2 Charge

18 Looks similar to excited levels in nuclei Uniform Mass gap suggests these particles differ by 1 unit of something strange. Also, vertical transitions between these states seem inhibited for some decays These states lived much longer than our naïve expectations

19 The Hadron Zoo = not fundamental particles Hadrons are made of smaller particles Based on the charges and mass spectrum.. Mass u Charge s d The lightest hadrons consist of 2 strongly interacting fermions with spin=1/2 (quarks) up-type quark, charge = +2/3 down-type quark, charge = -1/3 The existence of a mass gap, suggests a 3rd heavy quark strange-type quark, charge = -1/3 A jump over the gap to the next level is adding a strange quark

20 Introduces New Conserved Charges Iso-spin charge What distinguishes A proton from a neutron A charged pion from a neutral pion An electron from an electron-type neutrino Baryon Number Quarks = 1/3 baryon Anti-quarks = -1/3 baryon Strangeness What distinguishes Nucleons from Lambda baryons Omega and Delta baryons Counts the number of strange quarks present

21 Let s organize what we see (spin ½ quarks) Strangeness s -1 u d 0 3/2 1 1/2 0-1/2-1 -3/2 Iso-spin Charge

22 Let s organize what we see (spin 3/2 baryons) W - -3 Strangeness X *0 X *- -2 S *+ S *0 S *- -1 D ++ D + D 0 D - 0 3/2 1 1/2 0-1/2-1 -3/2 Iso-spin Charge

23 Let s organize what we see (spin 3/2 baryons) sss -3 Strangeness uss dss -2 uus uds dds -1 uuu uud udd ddd 0 3/2 1 1/2 0-1/2-1 -3/2 Iso-spin Charge

24 Let s organize what we see (spin 1/2 baryons) Strangeness X 0 X - S + S 0 S - L p n 0 3/2 1 1/2 0-1/2-1 -3/2 Iso-spin Charge

25 Let s organize what we see (spin 1/2 baryons) Strangeness uss dss -2 uus uds dds -1 uud udd 0 3/2 1 1/2 0-1/2-1 -3/2 Iso-spin Charge

26 Let s organize what we see (spin 0 mesons) Strangeness K10 K - h 0 p + p 0 p K + K 0 1 3/2 1 1/2 0-1/2-1 -3/2 Iso-spin Charge

27 Let s organize what we see (spin 0 mesons) su' sd' -1 Strangeness ud' uu' dd' ss' du' 0 us' ds' 1 3/2 1 1/2 0-1/2-1 -3/2 Iso-spin Charge

28 Hadrons are all made of quarks MESONS (LIGHTER THAN PROTON) Pion (π ±, π, ) Kaon (K ±, K, ) BARYONS (= OR HEAVIER THAN PROTON) Proton (p) anti-proton (p ) Neutron (n) anti-neutron (n') Lambda (Λ, ) Delta ( ##, #,,, " )

29 Particles LEPTONS (NO, STRONG INTERACTION) Electrons Muons Neutrinos HADRONS (YES, STRONG INTERACTION) Proton (p) anti-proton (p ) Neutron (n) anti-neutron (n') Pion (π ±, π, ) Kaon (K ±, K, ) Lambda (Λ, ) Delta ( ##, #,,, " )

30 Radiation & Particles RADIATION Electromagnetic Visible light Heat rays = infared Chemical rays = ultraviolet X-rays Gamma rays Weak b-rays Strong a-rays, fission PARTICLES Electron (e " ) Positron (e # ) Proton (p) Negatron or Anti-proton (p ) Neutron (n) anti-neutron (n') Muon (μ ± ) neutrinoss (n) Pion (π ±, π, ) Kaon (K ±, K, ) Lambda (Λ, ) Delta ( ##, #,,, " )

31 What Interactions do/don t conserve Electromagnetic Interaction Conserves baryon number, charge, iso-spin charge and strangeness Interactions governed by exchanging massless photons Photon is a spin-1 boson (interacts w/ all EM charged particles) Strong interaction Conserves baryon number, charge, iso-spin charge and strangeness Interactions governed by exchanging massless gluons Gluons are spin-1 bosons (interacts w/ quarks and other gluons) Weak interaction Conserves baryon number Interactions governed by exchanging massive W ± and Z 0 bosons W ± and Z 0 are spin-1 bosons

32 Standard Model of Particle Physics Spin ½ Fermions (3 families) Basic building blocks of matter Spin 1 Bosons Fundamental interactions Spin 0 Higgs Boson Can be viewed as a 5 th force Responsible for masses of all particles Spin 2 Graviton???? Gravity is not explained or included GR tells us it is Spin-2 Being long-ranged tells us it is massless

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