1. CP violation with K-mesons Vs. B-mesons
P Spring 2002 L17
Richard Kass
CP violation with K-mesons Vs. B-mesons
KL mesons B0 mesons
observe CPV with “wrong” Look for differences in decay distributions (time)
CP states (CP- ®CP+).
»3/1000 decays violate CP CPV is large (10-15%) for certain final states.
use KL0®2p/3p, KL0®pln But the final states have small branching ratios:
sin2b BRs » 5x10-4: B0®yKs, B0®yKL
sin2a BRs » 5x10-6: B0®p+p-, B0®p0p0
can make » 107 KL/sec can make » 5B0/sec
explores limited region of the CKM “triangles” provide a detailed check of
standard model. standard model.
Very mature field (1964) Field is just beginning. Experiments are planned
maybe one more experiment for next 20 years (SLAC, KEK, CERN, Fermilab)

2. CP Violation with Leptons
P Spring 2002 L17
CP Violation with Leptons
Richard Kass
If quarks can violate CP why not CP violation with leptons?
The CP violation that we see in “outer space” is much larger than the CPV
we see with quarks.
Maybe it’s the leptons that generated the cosmic baryon/anti-baryon asymmetry!
To date, no experimental evidence for CPV in lepton sector.
But if neutrinos violate CP who would know?
Very hard to do an experiment with neutrinos that is sensitive to CPV
We know that neutrinos “mix”: veÛvm veÛvt
Results from SuperK and SNO imply that neutrinos:
have mass (small)
neutrino lepton number not conserved (must modify standard model)
Is there a “CKM”-like matrix (3x3 unitary) for neutrinos ?
If neutrino mixing, why not CP violation?

3. Neutrino oscillations/mixing
P Spring 2002 L17
Neutrino oscillations/mixing
Richard Kass
The derivation of neutrino oscillations is very similar to the derivation of “strangeness” oscillations (Lec. 7) and B meson oscillations.
To make the derivation “simple” assume that CP is conserved, there are only 2 types of neutrinos and both neutrinos are stable (t1 = t2 = ¥).
At t=0 we have an electron (ne) and muon (nm) neutrino which are both mixtures of n1 and n2.
ne(t=0) º ne= n1cosq+n2sinq nm(t=0) º nm= -n1sinq+n2cosq
Since we don’t know (beforehand) how “mixed” the neutrinos are we use q to describe the mixture. Note: for the kaon case we assumed equal amounts of K1 and K2 or q=45 degrees.
The mass eigenstates (n1 and n2) propagate through space with energy E1 and E2 according to:
We are interested in the case where the neutrinos are relativistic (E>>m) and therefore:
Assuming the same energy (and E= p) for both neutrino components we can write:
The probability of observing a ne at x (=ct) given that a nm was produced at t=0 is:
P(nm® ne)=|< ne|nm(t)> |2
M&S

4. Neutrino Oscillations/Mixing
P Spring 2002 L17
Richard Kass
Neutrino Oscillations/Mixing
If we measure mass in eV, x in meters, and E in MeV we can write the above as:
The probability of observing a nm at x given that a nm was produced at t=0 is:
P(nm® nm)=|< nm|nm(t)> |2
In order to have neutrino oscillations:
at least one neutrino must have mass
the neutrinos must mix
Since the oscillation depends on Dm2 the mass of the neutrinos
must be determined from “other” experiments:
n energy endpoint experiments
double b-decay experiments

5. The SuperKamiokande Experiment
P Spring 2002 L17
The SuperKamiokande Experiment
Richard Kass
Original purpose was to search for proton decay: p®e+p0 (baryon # violation).
Found lepton number violation instead!
Use water as target and detector medium
Need lots of protons to get neutrino interactions.
Size: Cylinder of 41.4m (Height) x 39.3m (Diameter)
Weight: 50,000 tons of pure water
Need to identify e-’s and, m’s, p0’s (use Cerenkov radiation)
Reject unwanted backgrounds (cosmic rays, natural radiation)
103m underground at the Mozumi mine
of the Kamioka Mining&Smelting Co Kamioka-cho, Japan

6. Atmospheric Neutrinos
P Spring 2002 L17
Atmospheric Neutrinos
Richard Kass
Atmospheric neutrinos are the end
product of high energy collisions of
cosmic rays (mostly protons) with
the nuclei in our upper atmosphere.
Neutrinos are mostly the result of
pion decay (and subsequent muon
decay) but kaons also contribute to
neutrino production.
From the figure on the right we (naively) expect for the number of muon and electron induced interactions:
The experiments cannot distinguish
the charge of the lepton produced in the
neutrino interaction.
The efficiency for detecting muons is usually very different than the efficiency for
detecting electrons so the measured R is not 2.

7. Atmospheric Neutrino Oscillation Results from SuperK
P Spring 2002 L17
Richard Kass
Atmospheric Neutrino Oscillation Results from SuperK
Measure the number of ne and nm interactions in SuperK as a function of neutrino path length in the earth’s atmosphere. n
Neutrinos are produced by
cosmic ray interactions in
earths atmosphere.
superK
Phys. Rev. Lett. 86(2001)
earth
Phys. Rev. Lett. 81 (1998) 
atmosphere n
The nm‘s are
“disappearing”!

8. Atmospheric Neutrino Oscillation Results from SuperK
P Spring 2002 L17
Richard Kass
Atmospheric Neutrino Oscillation Results from SuperK
SuperK does not actually see an “oscillation”.
For example use the solution with:
Dm2 = 2.2x10-3 eV2 assume <En>=103 MeV
losc = (p/1.27)(<En>/Dm2) = (p/1.27)(103/2.2x10-3) = 1.1x106 m
SuperK sees too few muon neutrinos.
The number of expected muon neutrino interactions is calculated using a detailed simulation of the detector and takes into account detection efficiency as a function of energy and angle (atmospheric path length and detector path length).
Scenario #1: No oscillations (or equal muon and electron neutrino oscillations neÛnm)
number of muon and electron neutrino interactions independent of L/E.
Scenario #2: muon neutrino oscillates into electron neutrino (nm®ne)
excess number of electron neutrino interactions Vs. L/E
depletion of muon neutrino interactions Vs. L/E
Scenario #3: muon neutrino oscillates into tau neutrino (nm®nt)
SuperK has low detection efficiency for nt interactions
constant number of electron neutrino interactions Vs. L/E
Scenario #4: muon neutrino oscillates into a neutrino (nm®nS) that doesn’t interact
Scenario #5: Combination of 3&4 or something else??