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• Charm and beauty • • decuplet • spin and color • Baryon octet • Pseudoscalar • Vector mesons • Other tests of the • Mass relations and hyperfine splitting • EM mass differences and isospin symmetry • Baryon magnetic moments • Heavy quark mesons • The top quarks

Physics 661, Chapter 4 1 Quark Model

• Patterns of observed led to proposal in early 1960’s that hadrons were composed of quarks – u, d, and s (at that time)

• Were quarks real? – exhaustive searches for free quarks were unsuccessful

• With the discovery of “confined” quarks in the 1970’s it was realized that quarks truly exist, but cannot be freed

Physics 661, Chapter 4 2 - 1961

Murray Gell-Mann and Yuval Ne’eman

Physics 661, Chapter 4 3 Internal Structure - 1964

• SU(3) • Murray Gell-Mann and

Physics 661, Chapter 4 4 Charm and Beauty

• In 1970, three quarks explained all known hadrons. • During the 1970’s, two more quarks were discovered – charm, 1974 – bottom, 1977

• In 1995, the was finally observed

* Flavor I I3 S C B T Q/e u 1/2 1/2 0 0 0 0 +2/3 d 1/2 -1/2 0 0 0 0 -1/3 s 0 0 -1 0 0 0 -1/3 c 0 0 0 1 0 0 +2/3 b 0 0 0 0 -1 0 -1/3 t 0 0 0 0 0 1 +2/3

Physics 661, Chapter 4 5 Discovery of Charm

• 1974 – two complementary experiments – SLAC: e+e- → ψ → hadrons → e+e-, µ+µ- – BNL: p + Be → J/ψ + anything → e+e-

Physics 661, Chapter 4 6 Discovery of Charm

• 1974 – SLAC: e+e- → ψ → hadrons hadrons → e+e-, µ+µ-

width dominated by

experimental resolution µ+µ-

Also observed second peak at 3.7 GeV (ψʹ ) e+e-

Physics 661, Chapter 4 7 Discovery of Charm

• 1974 – BNL: p + Be → J/ψ + anything → e+e-

Physics 661, Chapter 4 8 Discovery of Charm

• Total width from integral of the cross section: i j

⌠σ(E) dE ⌡

e+e-

Physics 661, Chapter 4 9 Discovery of Charm

• Total width from integral of the cross section: i j

⌠σ(E) dE Γi = Γj = Γee ⌡

Let x = 2(E-ER)/Γ, dx = 2dE/Γ, dE=(Γ/2) dx

2J+1=3 and 2sa+1=2sb+1=2

2 2 ⌠σ(E) dE = 3π/2 λ (Γee/Γ) Γ ⌠ dx 2 ⌡ ⌡(1+x )

π Physics 661, Chapter 4 10

Discovery of Charm

• Total width from integral of the cross section: i j

2 2 2 ⌠σ(E) dE = 3π /2 λ (Γee/Γ) Γ = 800 nb MeV ⌡

Γee/Γ = 0.06 λ = hc/pc = 197 MeV-fm/1550 MeV

Γ = 0.093 MeV (very narrow) Ref: Data Group

Physics 661, Chapter 4 11 Discovery of Charm

• Vector mesons: Γ . ρ(776 MeV) 150 MeV ω(784 MeV) 8.4 MeV J/ψ(3100 MeV) 0.093 MeV

Γee ρ(776 MeV) 6.8 keV φ(1020 MeV) 1.4 keV ω(784 MeV) 0.6 keV J/ψ(3100 MeV) 5 keV Physics 661, Chapter 4 12 Discovery of Charm

• Shape of the resonance was consistent with Jp = 1- – interference of the direct and virtual channels

– ratio of decay modes (such as ρ0π0 and ρ-π+) shows J/ψ is I=0 state

Physics 661, Chapter 4 13 Discovery of Charm

• ψ(3700) → ψ(3100) π+ π-

Physics 661, Chapter 4 14 Discovery of Charm

Ref: Particle Data Group

(e+ e- + -) R = σ (e+ e- → hadrons) / σ (e+ e- → µ+ µ-) σPT → µ µ PT = 4πα2 / 3s + - + - – consider e e → hadrons as e e → QQ, = 87nb / s(GeV2) summed over all quarks (point cross section) Physics 661, Chapter 4 15 Discovery of Charm

• Narrowness of ψ(3100) and ψ(3700) explained by QCD, 3G exchange required

Colorless, and C odd

Physics 661, Chapter 4 16 Discovery of Charm

• For heavier charmionium states, open charm decay modes open up -> broader resonances

Physics 661, Chapter 4 17 Discovery of Charm

ψ(3100) Γ = 0.093 MeV

ψ(3700) Γ = 0.30 MeV Open charm threshold ψ(3770) Γ = 27 ± 1 MeV ψ(4040) Γ = 80 ± 10 MeV ψ(4160) Γ = 103 ± 8 MeV ψ(4415) Γ = 62 ± 20 MeV

Ref: Particle Data Group

Physics 661, Chapter 4 18 Discovery of Beauty

• 1977 – history repeats itself – another narrow resonance

– this time at Fermilab – p+Be -> µ+µ- + anything p+Cu -> µ+µ- + anything p+Pt -> µ+µ- + anything 400 GeV

Physics 661, Chapter 4 19 Discovery of Beauty

• - colliders refine measurements: – DORIS at DESY, CLEO at Cornell

Physics 661, Chapter 4 20 Discovery of Beauty

Ref: Particle Data Group

Physics 661, Chapter 4 21 Discovery of Beauty

Mass Γee (keV) Γ (MeV) (MeV) ϒ(1S) 9460 1.34 0.054 ϒ(2S) 10023 0.61 0.032 ϒ(3S) 10355 0.020 ϒ(4S) 10579 0.27 20.5 ± 2.5

Ref: Particle Data Group

Physics 661, Chapter 4 22 Quarkonium and

Physics 661, Chapter 4 23 Positronium

• e+e- -> γγ – τ = 1.25 x 10-10 sec – singlet state – even ang. momentum -> J=0 -> C = (-1)L+S =(-1)0 = +1 – C = (-1)nγ -> C = +1

• e+e- -> γγγ – τ = 1.4 x 10-7 sec – triplet state -> J=1 -> C = (-1)L+S = (-1)0+1 = -1 – C = (-1)nγ -> C = -1

Physics 661, Chapter 4 24 C & P of e+e- system

• Interchange of particles – Spin symmetry (-1)S+1

eg. α(s=0, s3=0) = 1/√2 (éê−êé) – Spatial symmetry (-1)L+1 • Recall opposite intrinsic parities of e+ and e-

– So – total symmetry is (-1)L+S

• Interchange of space and spin is equivalent to Charge Conjugation

Physics 661, Chapter 4 25 Positronium

• Principal energy levels from non-relativistic Schroedinger equation in a Coulomb potential

2 2 2 En = - α µc / 2n , µ = m/2

• Relativistic corrections: – spin-orbit • S, P, D – spin-spin 3 1 • S1, S0, ……

– these are about the same size in positronium: • ΔE ~ α4mc2 / n3

Physics 661, Chapter 4 26 Positronium

• Lifetimes: – Two photon • two means rate is to order α2 • overlap of wavefunctions at origin to annihilate – |ψ(0)|2 = 1/ π a3 – a = 2 h/(2π mc α) • exact result: – Γ = α5 m/2

– Three photon • rate at higher order – Γ = 2(π2-9) α6 m/(9π)

Physics 661, Chapter 4 27 Positronium

• Excellent agreement on Theory and Experimental results for lifetimes and energy levels – (see textbook)

Physics 661, Chapter 4 28 Quarkonium

• Similar energy levels to positronium 2S+1 n L J

Physics 661, Chapter 4 29 Quarkonium

• Different potential: – positronium -> Coulomb – V = - α / r

– quarkonium -> potential from QCD – expected potential of the form

– V = -(4/3) αs / r + kr

Physics 661, Chapter 4 30 Quarkonium

• αs = 0.2 -1 • k ≈ 1 GeV fm

Physics 661, Chapter 4 31 Quarkonium

• For the heavy quarks, a non-relativistic approximation is valid: – p/m ~ 0.13

• Fine structure is of order αs, and therefore coarser than for positronium, as observed

Physics 661, Chapter 4 32 Baryon Decuplet

• Lightest spin 3/2

isospin (3rd comp.)

Before the Ω- was discovered, it (and its properties) were predicted by this pattern Physics 661, Chapter 4 33 Discovery of the Ω-

Three, sequential decays of the Ω- = sss Ξ0 = ssu Λ = sud

Physics 661, Chapter 4 34 Baryon Decuplet

• Notice the masses M(Δ) = 1232 M(Σ) = 1384 = M(Δ) + 152 M(Ξ) = 1533 = M(Σ) + 149 M(Ω) = 1672 = M(Ξ) + 139

We see an orderly increase of mass with number of strange quarks

Physics 661, Chapter 4 35 Group Theory

• Quarks are fundamental representations of the group SU(3)

3 ⊗ 3 = 6 ⊕ 3 3 ⊗ 3 = 8 ⊕ 1

3 ⊗ 3 ⊗ 3 = 1 ⊕ 8 ⊕ 8 ⊕ 10

1 is anti-symmetric under interchange of two quarks 10 is symmetric under interchange of two quarks 8’s are mixed under interchange of two quarks

Physics 661, Chapter 4 36 Group Theory – Combining Multiplets

• Multiplet Labels – SU(n) -> (n-1) non negative integers (α, β, γ, …) so for SU(3) (α, β) (lengths of top, and bottom)

(1,0) (1,1) (3,0) (0,1)

Physics 661, Chapter 4 37

Group Theory – Combining Multiplets

• Number of Particles in the Multiplet – For SU(3) N = (α+1) (β+1) (α+β+2)/2

(1,1) (3,0)

N=8 N=10

N=3 N=3 (1,0) (0,1)

Physics 661, Chapter 4 38 Group Theory – Combining Multiplets

• Young’s diagrams – Top row is α boxes past end of 2nd row – 2nd row is β boxes past end of 3rd row

(1,0)

(1,1)

(3,0)

(0,1)

Physics 661, Chapter 4 39 Group Theory – Combining Multiplets

• Coupling multiplets – Sequence of letters okay if everywhere at least as many of an early letter (eg. a) has occurred as a later letter (eg. b) – In one diagram, replace boxes by a’s (1st row), b’s (2nd row), etc.

– So becomes a

becomes a a b

becomes a a a becomes a b

Physics 661, Chapter 4 40 Group Theory – Combining Multiplets

3 x 3 = x a = a + = (2,0) + (0,1) = 6 + 3 a

3 x 3 = 6 + 3

x = +

Physics 661, Chapter 4 41 Group Theory – Combining Multiplets

3 x 3 = x a = ( a + ) b a b

= a + = (1,1) + (0,0) = 8 + 1 b a b

+ = +

Physics 661, Chapter 4 42 Group Theory – Combining Multiplets

3 x 3 x 3 = (6 + 3) x 3 = ( + ) x a

= a + + a + a a = (3,0) + (1,1) + (1,1) + (0,0) = 10 + 8 + 8 + 1

x x = + + +

Physics 661, Chapter 4 43 Quark Spin and Color

• Consider the Δ++ – spin 3/2 (uuu) – therefore u↑u↑u↑ • now, this appears to violate the Pauli principle – two or more identical cannot exist in the same quantum state • resolution, another quantum number (color) and each of the u quarks have a different value: u↑(red)u↑(green)u↑(blue) and we have to aniti-symmetrize the color u↑u↑u↑ (rgb-rbg+brg-bgr+gbr-grb)

Physics 661, Chapter 4 44 Quark Spin and Color

• We also know from the rate of decay of the π0 that there are three colors

0 2 Γ(π →γγ) = 7.73 eV (Nc/3) Γ(observed) = 7.76 ± 0.6 eV

Nc = 2.99 ± 0.12

+ - • Also the rate of e e → hadrons tells us Nc = 3 Physics 661, Chapter 4 45 π0 Lifetime

0 2 • Theory: Γ(π → γγ) = 7.73 eV (Nc/3)

τ = h/Γ = 197 MeV-fm/(3 x 1023 fm/s Γ) = 6.6 x 10-16 s / Γ(eV) -17 2 = 8.5 x 10 s (3/Nc)

-2 2 d = γ β c τ = 2.6 x 10 µm (p/m) (3/Nc)

2 Suppose p = 5 GeV, then d ≈ 1 µm (3/Nc)

Physics 661, Chapter 4 46

π0 Lifetime Experiment p + A → π0 + X γ γ

γ beam π0 γ d

d ~ 1 µm for p = 5 GeV and Nc=3

Physics 661, Chapter 4 47 π0 Lifetime Experiment

Technique – use thin foils for target, convert photons into e+e- pairs, and count as function of target thickness (t)

γ Proton beam 0 π e- γ d

e+ t

Physics 661, Chapter 4 48 π0 Lifetime Experiment

1. Production rate of π0 is K dx 2. Then, π0s decay with decay length λ 3. Pairs are produced immediately as Dalitz pairs in fraction B of decays, or appear in

conversion with prob dy/X0 Pair Production Rate

R(t) = Kt{ B 2 -t/λ + 1/X0[t/2-λ+λ /t(1-e )] }

Physics 661, Chapter 4 49

π0 Lifetime Experiment

2 -t/λ R(t) = Kt{ B + 1/X0[t/2-λ+λ /t(1-e )] }

Thin foil ⇒ t ≪ λ

2 R(t) ≈ Kt (B + t /6λX0)

Physics 661, Chapter 4 50 π0 Lifetime Experiment

2 Atherton et al., R(t) ≈ Kt (B + t /6λX0) Phy. Lett. 158B, 81 (1985) t = 3, 4, 18, 58 µm (platinum) p = 5 GeV/c

-17 Part. Data Group τ = 8.4 ± 0.4 x 10 sec ⇒ NC = 3 Physics 661, Chapter 4 51 Baryon Octet

• Multiplet including the and proton – lightest spin 1/2 baryons – wavefunction symmetric under simultaneous interchange of flavor and spin

– total wave-function must be anti-symmetric • (flavor)(spin)(color)(space) • color is anti-symmetric for all hadrons because they are color-neutral, singlet states • space is symmetric because L=0 • ∴ (flavor)(spin) is symmetric

Physics 661, Chapter 4 52 Baryon Octet

• Consider the proton (uud) – two quarks in the spin singlet state • (↑↓-↓↑)/ √ 2 (anti-symmetric)

– these quarks must also be in an anti-symmetric flavor state for an overall symmetric flavor- spin wavefunction • (ud-du)/ √ 2 (anti-symmetric)

– Third Quark is spin up (u↑d↓ - u↓d↑ - d↑u↓ + d↓u↑) u↑

Physics 661, Chapter 4 53 Baryon Octet

• Now symmetrize by making cyclic permutation (2u↑u↑d↓ + 2d↓u↑u↑ + 2u↑d↓u↑ - u↓d↑u↑ - u↑u↓d↑ - u↓u↑d↑ - d↑u↓u↑ - u↑d↑u↓ - d↑u↑u↓) / √ 18

Physics 661, Chapter 4 54 Baryon Octet

Physics 661, Chapter 4 55 Baryon Octet

• Notice the masses M(Ν) = 939 M(Σ) = 1193 = M(Ν) + 254 M(Λ) = 1116 = M(Ν) + 177 M(Ξ) = 1318 = M(Σ) + 125 = M(Λ) + 202

Pattern is more complicated than for decuplet hyperfine splitting Physics 661, Chapter 4 56 Light Pseudoscalar Mesons

• Combine a quark and an antiquark – 3 ⊗ 3 = 8 ⊕ 1

Physics 661, Chapter 4 57 Light Pseudoscalar Mesons

• Combine a quark and an antiquark – 3 ⊗ 3 = 8 ⊕ 1

The strangeless mesons

This table ignores the strange quarks

Physics 661, Chapter 4 58 Light Pseudoscalar Mesons

• C operation on quarks – (Condon-Shortly convention)

Physics 661, Chapter 4 59 Light Pseudoscalar Mesons

Physics 661, Chapter 4 60 Light Pseudoscalar Mesons

Gell-Mann Okubo Mass Formula

2 2 2 4(MK) = Mπ + 3 Mη

0.988 GeV2 = 0.924 GeV2

Physics 661, Chapter 4 61 The light vector mesons

Physics 661, Chapter 4 62 The light vector mesons

(excluding π0γ)

Physics 661, Chapter 4 63 The light vector mesons

• “ideal mixing”

φ8 = (uu + dd – 2ss) / √6

φ0 = (uu + dd + ss) / √3

φ = (φ0 - √2 φ8) / √3 = ss

ω = (φ8 + √2 φ0) / √3 = (dd + uu)/ √2

Physics 661, Chapter 4 64 The light vector mesons

Suppressed like J/ψ, because of unconnected quark lines (OZI rule)

Physics 661, Chapter 4 65 - cross-sections

(mb)

σ

σ(πp) = 2/3 σ(pp)

Additive quark model Physics 661, Chapter 4 66 Pair Production on Isoscalar Targets

• Drell-Yan production

- + - 2 σ(π C → µ µ + . . . ) ~ 18 Qu = 18(4/9) + + - 2 σ(π C → µ µ + . . . ) ~ 18 Qd = 18(1/9) since π- = ud π+ = du C = 18u + 18d

Physics 661, Chapter 4 67 Vector Decay to

Physics 661, Chapter 4 68 Mass Relations and Hyperfine Splitting

2 • ΔE(QQ) = 8παs |ψ(0)| σi • σj / 9mimj = 2K σi • σj / mimj 2 • ΔE(QQ) = 4παs |ψ(0)| σi • σj / 9mimj = K σi • σj / mimj

due to color field – analogous to, but stronger than, EM hyperfine splitting Physics 661, Chapter 4 69 Electromagnetic Mass Differences and Isospin Symmetry

M() = Mbare + ΔMEM

Mbare = constituents plus S.I. (incl. hfs)

Expect the ΔMEM for multiplet to be same for like charge particles: ΔM(p) = ΔM(Σ+) ΔM(Σ-) = ΔM(Ξ-) 0 ΔM(Ξ ) = ΔM(n) With bare masses: M(p) + M(Σ-) + M(Ξ0) = M(Σ+) + M(Ξ-) + M(n) M(p) - M(n) = M(Σ+) - M(Σ-) + M(Ξ-) - M(Ξ0) -1.3 MeV = -8,0 MeV + 6.4 MeV = -1.6 MeV

Md -Mu = 2 MeV Physics 661, Chapter 4 70 Magnetic Moments of Baryons

• Magnetic moments of the – proton 2.793 nuclear magnetons – neutron - 1.913 nuclear magnetons – [ nuclear magneton = eh/(2Mc)]

• Recall the proton wave function: (2u↑u↑d↓ + 2d↓u↑u↑ + 2u↑d↓u↑ - u↓d↑u↑ - u↑u↓d↑ - u↓u↑d↑ - d↑u↓u↑ - u↑d↑u↓ - d↑u↑u↓) / √ 18

Physics 661, Chapter 4 71 Magnetic Moments of Baryons proton: (2u↑u↑d↓ + 2d↓u↑u↑ + 2u↑d↓u↑ - u↓d↑u↑ - u↑u↓d↑ - u↓u↑d↑ - d↑u↓u↑ - u↑d↑u↓ - d↑u↑u↓) / √ 18

µp = 12/18 (2µu-µd) + 6/18 (µd)

= 4/3 µu - 1/3 µd

µn = 4/3 µd - 1/3 µu

µu = - 2 µd

µp = 4/3 µu - 1/3(-1/2 µu) = 3/2 µu

µn = 4/3(-1/2 µu) - 1/3 µu = - µu = -2/3 µp

Physics 661, Chapter 4 72 Magnetic Moments of Baryons proton: (2u↑u↑d↓ + 2d↓u↑u↑ + 2u↑d↓u↑ - u↓d↑u↑ - u↑u↓d↑ - u↓u↑d↑ - d↑u↓u↑ - u↑d↑u↓ - d↑u↑u↓) / √ 18

µp = 4/3 µu – 1/3 µd = 3/2 µu

µn = 4/3 µd - 1/3 µu = - µu = -2/3 µp

Consider other octet baryons – Easiest are those with two identical quarks: Σ− (dds), Σ+ (uus), Ξ−(dss), Ξ0 (uss)

Physics 661, Chapter 4 73 Magnetic Moments of Baryons consider Σ+ (uus) - replace d in proton with s proton: (2u↑u↑d↓ + 2d↓u↑u↑ + 2u↑d↓u↑ - u↓d↑u↑ - u↑u↓d↑ - u↓u↑d↑ - d↑u↓u↑ - u↑d↑u↓ - d↑u↑u↓) / √ 18 Σ+ : (2u↑u↑s↓ + 2s↓u↑u↑ + 2u↑s↓u↑ - u↓s↑u↑ - u↑u↓s↑ - u↓u↑s↑ - s↑u↓u↑ - u↑s↑u↓ - s↑u↑u↓) / √ 18

µp = 4/3 µu – 1/3 µd = 3/2 µu + µ(Σ ) = 4/3 µu – 1/3 µs

Physics 661, Chapter 4 74 Magnetic Moments of Baryons

With similar arguments, we find for the other baryons with two identical quarks:

- µ(Σ ) = 4/3 µd – 1/3 µs

0 µ(Ξ ) = 4/3 µs – 1/3 µu

- µ(Ξ ) = 4/3 µs – 1/3 µd

Physics 661, Chapter 4 75 Magnetic Moments of Baryons

consider Σ0 (uds) get Σ0 from I-(Σ+) [I-(u) = d/√2 , I-(d) = 0 ] Ι-(Σ+) = I-(2u↑u↑s↓ + 2s↓u↑u↑ + 2u↑s↓u↑ - u↓s↑u↑ - u↑u↓s↑ - u↓u↑s↑ - s↑u↓u↑ - u↑s↑u↓ - s↑u↑u↓) / √ 18 = (2d↑u↑s↓ + 2u↑d↑s↓ + 2s↓d↑u↑ + 2s↓u↑d↑ + 2d↑s↓u↑ + 2u↑s↓d↑ - d↓s↑u↑ - u↓s↑d↑ - d↑u↓s↑ - u↑d↓s↑ - d↓u↑s↑ -u↓d↑s↑ - s↑d↓u↑ - s↑u↓d↑ - d↑s↑u↓ - u↑s↑d↓ - s↑d↑u↓ - s↑u↑d↓) / √ 36

Physics 661, Chapter 4 76

Magnetic Moments of Baryons

Σ0 = (2d↑u↑s↓ + 2u↑d↑s↓ + 2s↓d↑u↑ + 2s↓u↑d↑ + 2d↑s↓u↑ + 2u↑s↓d↑ - d↓s↑u↑ - u↓s↑d↑ - d↑u↓s↑ - u↑d↓s↑ - d↓u↑s↑ -u↓d↑s↑ - s↑d↓u↑ - s↑u↓d↑ - d↑s↑u↓ - u↑s↑d↓ - s↑d↑u↓ - s↑u↑d↓) / √ 36

0 µ(Σ ) = [6 x 4 (µu + µd – µs) + 12 x µs]/36

= [2 µu + 2 µd – µs]/3

Physics 661, Chapter 4 77 Magnetic Moments of Baryons

mn (= mu = md) = 336 MeV ms = 509 MeV

Physics 661, Chapter 4 78 Magnetic •Moments x of Baryons

Particle Data Group 2010

Physics 661, Chapter 4 79 Mesons Built of Light and Heavy Quarks

Pseudoscalar mesons in SU(4)

• D+ (=cd) • D0 (=cu) + • D s (=cs)

Particle Data Group

Physics 661, Chapter 4 80 Mesons Built of Light and Heavy Quarks

Vector mesons in SU(4)

• D*+ (=cd) • D*0 (=cu) *+ • D s (=cs)

Particle Data Group

Physics 661, Chapter 4 81 Mesons Built of Light and Heavy Quarks

Charmed pseudoscalar mesons decay via ΔC = ±1 weak interactions with lifetimes of ~ 10-12 sec largely to final states containing strange particles

eg. D0 →K−π+

or c → s

Physics 661, Chapter 4 82 Mesons Built of Light and Heavy Quarks

Physics 661, Chapter 4 83 Mesons Built of Light and Heavy Quarks

• In heavy quark-light quark system, heavy quark has small effect on energy levels ~ Λ/M ~ 0.2 Gev/M • Hyperfine splitting smaller than for light quark mesons - ~1/M

~ 1/M independent of M (color magnetic int.)

• Mass difference for pseudoscalar states only weakly depends on heavy quark mass + + – M(Ds )-M(D ) = 1968-1870 = 98 MeV 0 0 – M(Bs ) – M(B ) = 5366 – 5280 = 86 MeV Physics 661, Chapter 4 84 Charmed Baryons

• SU(4)

Physics 661, Chapter 4 85 Top Quark

• First observed in 1995 at Fermilab • M = 175 GeV • pp → t t + X (1/1010 collisions) → W+b W-b

Physics 661, Chapter 4 86 Top quark production

Also q + g → q + Q + Q Physics 661, Chapter 4 87 Top Quark Decay

b t

W

Physics 661, Chapter 4 88 Top Quark Decay

• Top quark is very short lived, not long enough for bound states to form • Particle Data Group: Γ= 1.99 (+0.69 -0.55) GeV τ = h/Γ= 197 MeV-fm/3 x 1023 fm/sec/1990 ~ 3 x 10-25 sec b t

W

Physics 661, Chapter 4 89