09nuclei1 - P461 Nuclei I 1 Properties of Nuclei • Z...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: P461 - Nuclei I 1 Properties of Nuclei • Z protons and N neutrons held together with a short-ranged force b gives binding energy • P and n made from quarks. Most of the mass due to the strong interactions binding them together. Recent JLAB results show masses inside nucleus might be slightly smaller than free particles • P and n are about 1 Fermi in size and the strong force doesn’t compress. Size ~ range of strong force b all nuclei have the same density and higher A nuclei are bigger (unlike atoms) m MeV c m MeV c M Zm Nm E Am with A Z N m u MeV c p n nucleus p n bind N N = = = + − ≈ = + = = 938 3 939 6 9315 2 2 2 . / . / . / P461 - Nuclei I 2 Protons vs Neutron • neutron slightly heavier than proton and so it decays. No reason “why” just observation • quark content: n = udd and p = uud (plus g, qqbar) Mass up and down quarks 5-10 Mev • three generations of quarks. Only top quark ever observed as “bare” quark. Somehow up quark seems to be slightly lighter than down quark K 33 31 35 2 2 , ) ( 10 886 ) mod ( 10 / 56 . 939 / 27 . 938 π μ π ν + + → + + → > > + + − e p e p n specific yrs s es all yrs lifetime c MeV c MeV mass neutron proton ???? 3 1 3 2 u d s c b t m m m m m m b t s c d u > > > ⇒ − P461 - Nuclei I 3 Nuclei Force • Strong force binds together nucleons • Strong force nominally carried by gluons. But internucleon force carried by pions (quark- antiquark bound states) as effective range too large for gluons • Each p/n surrounded by virtual pions. Strong force identical p-p, p-n, n-n (except for symmetry/Pauli exclusion effects) • Range of 1 F due to pion mass p n n p p p n n + → + → + → + → − + π π π π p n n p π Δ Δ Δ Δ E t t m s x c m MeVF MeV F ≈ → = ≈ ≈ = = − h h h π π 10 197 135 1 25 P461 - Nuclei I 4 Nuclear Sizes and Densities • Use e + A b e + A scattering completely EM • p e = 1000 MeV/c b wavelength = 1.2 F now JLAB, in 60s/70s SLAC up to 20 GeV( mapped out quarks) • Measurement of angular dependence of cross section gives charge distribution (Fourier transform) • Can also scatter neutral particles (n, K L ) in strong interactions to give n,p distributions • Find density ~same for all but the lowest A nucleii ρ ρ ( ) ( ) / ( )/ r e kg m r a b = + ≈ − 1 10 18 3 a A F volume A b F surface area A skin depth radius A = ∝ = ∝ ≈ ∝ 107 055 1 3 2 3 1 3 . . / / / P461 - Nuclei I 5 Nuclear Densities • can write density as an energy density • Note Quark-Gluon Plasma occurs if 3 2 27 3 / 1 / 14 . / / 938 10 7 . 1 2 . 1 F GeV vol E c MeV kg m FA R p ≈ ⇒ = × = + = − 3 / 1 / F GeV vol E ≥ m F F kg cm g m kg 15 3 28 3 14 3 17 10 1 10 / 10 10 − − = = = P461 - Nuclei I 6 Nuclear Densities ) 1979 ( 9 , 42 , , , , ) ( PRL Pb Sn Cu Al C A anything A K L = → + σ P461 - Nuclei I 7 Nuclear Densities ) 1979 ( 9 , 42 , , , , ) ( PRL Pb Sn Cu Al C A anything A K L = → + σ 84 ....
View Full Document

{[ snackBarMessage ]}

Page1 / 46

09nuclei1 - P461 Nuclei I 1 Properties of Nuclei • Z...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online