1938 when he premiered in comic book form superman’ s flying was explained as jumping
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1938 when he premiered in comic book form Superman’ s flying was explained as jumping with super strength. TheAdventures of Superman(1950). Faster than a speeding bullet !. More powerful than a locomotive !. Able to leap tall buildings with a single bound !. - PowerPoint PPT PresentationTRANSCRIPT
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo1938 when he premiered in comic book form Superman’s flying
was explained as jumping with super strength.
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Faster than a speeding bullet!
More powerful than a locomotive!
Able to leap tall buildings
with a single bound!
TheAdventures of Superman(1950)
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
The Superman movie (1978) included camera shots of stopping, hovering,
surveying below before launching off in a new direction.
What’s wrong with that?
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
When an object explodes or breaks apart::
Is this ever possible? In free space?Even in the initial moment along the ground?
Why?
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Explosion (inelastic un-collision)
Before the explosion:
vo = 0
m1 m2
v1 v2
After the explosion:
Mass, M
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Explosion...
• No external forces, so PP is conserved.
• Initially: PP = 0
• Finally: PP = m1vv1 + m2vv2 = 0
m1vv1 = m2vv2
m1 m2
vv1 vv2
vo = 0
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1 2
Before fission:
After fission:
Which fragment has a greater momentum?
Uranium nucleus
A) 1B) 2C) both the same
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1 2
Before fission:
After fission:
Which fragment has a greater speed?
Uranium nucleus
A) 1B) 2C) both the same
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1 2
Before fission:
After fission:
Which fragment has a greater
momentum? C) both the same
Uranium nucleus
speed?
Same momentem! Total momentum before fission is zero, so total after must still be zero (no external forces so momentum is conserved). Since momentum is a vector, fragments 1 and 2 must have equal and opposite momenta. Since fragment 1 has a smaller mass, it must have greater speed since v = p / m.
A) 1
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
p = 0 pgas procket
pi = 0 = pf = pgas + procket pgas = – procket
pi = 0 = pf = prifle + pbullet prifle = – pbullet
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
A cannon rests on a railroad flatcar with a total mass of 1000 kg. When a 10 kg cannon ball is fired at a speed of 50 m/sec, as shown, what is the speed of the flatcar?
A) 0 m/sB) ½ m/s to the rightC) 1 m/s to the leftD) 20 m/s to the right
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
A bomb at rest explodes into four fragments. The momentum vectors for three of the fragments are shown. Which arrow below best represents the momentum vector of the fourth fragment?
?
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
No external forces act on the bomb, so its momentum must be conserved: the total momentum before the explosion is zero, so total momentum after must also be zero.
?
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
An explosive chargeseparates rocket stages
high in earth’s atmosphere.
Which best represent the trajectories of the stages?
AB
C
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Which best represents its streaming fragments?
An artillery shell bursts at the peak of its trajectory.
A B
CD
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
For a particle decaying in flight
would this pair of trajectories be possible?
Why?
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Status of particle physics early 20th century
Electron J.J.Thomson 1898
nucleus ( proton) Ernest Rutherford 1908-09
Henri Becquerel 1896 Ernest Rutherford 1899
P. Villard 1900
X-rays Wilhelm Roentgen 1895
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Status of particle physics early 20th century
Electron J.J.Thomson 1898
nucleus ( proton) Ernest Rutherford 1908-09
Henri Becquerel 1896 Ernest Rutherford 1899
P. Villard 1900
X-rays Wilhelm Roentgen 1895
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1930 Series of studies of nuclear beta decay, e.g.,
Potassium goes to calcium 10K40 20Ca40
Copper goes to zinc 29Cu64 30Zn64 Boron goes to carbon 5B12 6C12 Tritium goes to helium 1H3 2He3
1932 Once neutron discovered, included the more fundamental n p + e
For simple 2-body decay, conservation of energy and momentum demand both the recoil of the nucleus andenergy of the emitted electron be fixed (by the energy released through the loss of mass) to a single precise value.
Ee = (mA2 - mB
2 - me2)c2/2mA
but this only seems to match the maximum value observedon a spectrum of beta ray energies!
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1932 n p + e + neutrino
charge 0 +1 1 ?mass 939.56563 938.27231 0.51099906 ? MeV MeV MeV
neutrino mass < 5.1 eV < me /100000 0
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1932 Carl Anderson first observes the positron in a cloud chamber photograph.
•Droplet density (thickness) of track appears to identify it as that of an electron•Curvature of track confirms the charge to mass ratio (q/m) is that of an electron•The particle’s slowing in its passage through lead foil establishes its direction ( UP! ).•Direction of curvature clearly indicates it is POSITVELY charged!
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Additional comments on Matter/Antimatter Production
e+e•Particles are created in pairs e+
e
and annihilatein pairs
Notice how this “conserves” ELECTRIC CHARGE(as well as MOMENTUM and ENERGY)
p+pp+p+p+p Lab frame (fixed target) Center of Momentum frame
a b a c db
a b
at thresholdof production final state
total energy
= 4mprotonc2
So conservation of energy argues: EaCOM+Eb
COM=4mc2
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1936 Millikan’s group shows at earth’s surface cosmic ray showers are dominated by electrons, gammas, and
X-particles capable of penetrating deep underground (to lake bottom and deep tunnel experiments) and yielding isolated single cloud chamber tracks
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1937 Street and Stevenson1938 Anderson and Neddermeyer determine X-particles
•are charged•have 206× the electron’s mass•decay to electrons with a mean lifetime of 2sec
0.000002 sec
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1947 Lattes, Muirhead, Occhialini and Powell observe pion decay
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1947 Lattes, Muirhead, Occhialini and Powell observe pion decay
Consistently ~600 microns (0.6 mm)
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
+ energy always
predictably fixedby E
Under the influence of a magnetic field
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1932 n p + e + neutrino
charge 0 +1 1 ?mass 939.56563 938.27231 0.51099906 ? MeV MeV MeV
neutrino mass < 5.1 eV < me /100000 0
??
+ energy always
predictably fixed
by E
simple 2-body decay!
+ + + neutrino?charge +1 +1 ?
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
n p + e + neutrino?
+ + + neutrino?Then
- e- + neutrino????
p
e
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
n p + e + neutrino?
+ + + neutrino?Then
- e- + neutrino????
As in the case of decaying radioactive isotopes, the electrons’s energy varied, with a maximum cutoff (whose value was the 2-body prediction)
3 body decay!
p
e
e
2 neutrinos
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Hadrons “heavy” or “strong” particles”p, n (the nucleons) and those
they interacted “strongly” with Mesons intermediate or medium mass
Leptons “light particles” e-, e+, ,
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1953, 1956, 1959 Cowan & Reines
Savannah River (1000-MWatt) Nuclear Reactorin South Carolina
looked for the inverse of the process
n p + e- + neutrino
p + neutrino n + e+
with estimate flux of 51013 neutrinos/cm2-sec observed 2-3 p + neutrino events/hour
also looked forn + neutrino p + e
but never observed!
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1953 Konopinski & Mahmoud introduce LEPTON NUMBER to account for which decays/reactions are possible, which not
e, ( ) assigned L = +1 e+, + ( +) assigned L =1
n p + e- + neutrino
p + neutrino n + e+
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1953 Konopinski & Mahmoud introduce LEPTON NUMBER to account for which decays/reactions are possible, which not
e, ( ) assigned L = +1 e+, + ( +) assigned L =1
n p + e- +
p + n + e+
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1953 Konopinski & Mahmoud introduce LEPTON NUMBER to account for which decays/reactions are possible, which not
e, ( ) assigned L = +1 e+, + ( +) assigned L =1
n p + e- +
p + n + e+
n + p + e- ???
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1962 Lederman,Schwartz,Steinberger Brookhaven National Laboratory
using a as a source of antineutrinos
and a 44-foot thick stack of steel (from a dismantled warship hull)
to shield everything but the ’s
found 29 instances of + p + + n
but none of + n e+ + n
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
Elastic collision
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
p
p
p
p p
p
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1947 Rochester and Butler cloud chamber cosmic ray event
of a neutral object decaying into two pions
K0 +
1949 C. F. Powell photographic emulsion event
K+
1950 Carl Anderson Cal Tech p +
The Cosmic Ray Observatory Project High Energy Physics Group The University of Nebraska-Lincoln
The Particle Zoo
1952 Brookhaven Cosmotron 1st modern accelerator
artificially creating these particles for study
1954 6.2-GeV p synchrotron Lawrence,Berkeley1960 28-GeV p synchrotron CERN, Geneva 33-GeV p synchrotron Brookhaven Lab1962 6-GeV e synchrotron Cambridge1963 12.5-GeV p synchrotron Argonne Lab1964 6.5-GeV p synchrotron DESY,Germany1966 21-GeV e Linac SLAC (Standford)