THE ROLE OF CP AND T IN HIGH-ENERGY PHYSICS

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THE ROLE OF CP AND T IN HIGH-ENERGY PHYSICS. Phenomenology of CP and T Direct CP Violation Measurements NA48, KTEV T Violation in rare Kaon decays KTEV Direct checks of T Violation CPLEAR Outlook. L.Gatignon / CERN. PHENOMENOLGY OF CP AND T. C: Charge conjugation

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Presentation Transcript
THE ROLE OF CP AND TIN HIGH-ENERGY PHYSICS
• Phenomenology of CP and T
• Direct CP Violation Measurements NA48, KTEV
• T Violation in rare Kaon decays KTEV
• Direct checks of T Violation CPLEAR
• Outlook

L.Gatignon / CERN

Symposium Marie Curie

PHENOMENOLGY OF CP AND T

C: Charge conjugation

Replace all particles by their anti-particles

P: Parity

Space inversion: x  -x

T: Time reversal

Invert the arrow of time t  - t

CPT Theorem:within any quantum field theory, all interactions are invariant under the succession of the three operations

C, P and T in any order.

This theorem is based on very general assumptions.

• Its experimental consequences are rather well verified, such as the
• identity of masses of particles and anti-particles, e.g.
• m Ko – mKo < 10-18
Actions of P and T operators

Like r xp

Like fors

Magnetic dipole

Electric dipole

Long. polarization

Transv. polarization

We can now verify the behaviour of these quantities under the operators

Actions of P and T operators

In High-Energy physics, direct checks of T-violation

are not so easy to do.

Here we will see 3 approaches:

• Address T-related issues via CPe.g. CP experiments NA48 and KTEV
• Transverse polarization measurementse.g. KTEV experiment
• Direct measurements on time reversedprocessese.g. CPLEAR experiment
Parity violation
• The angular distribution of e- isI(q) = 1 + as.p / E- s is a unit spin vecor alongJ- p and E are the e- momentum and energy
• The first term, 1, is even parity
• The second term,s.p, is odd parity

Parity is violated

C Violation

Left-handed neutrino

Right-handed anti-neutrino

J

n

n

J

But CP transforms a left-handed n into a right-handedn

Is CP conserved ???

CP Violation
• CP violation is (via CPT) one of the feasible experimental approaches to T‑violation in high-energy physics
• Many of the T-violation studies have indeed been performed by experiments originally designed for CP-violation measurements (NA48, KTEV, CPLEAR,..)
• The neutral kaon system provides an excellent laboratory for CP and T violation experiments
• CP violation is considered to be one of the necessary elements to explain the matter dominance (over anti-matter) in the universe.

This implies also that the matter/anti-matter ratio

increases with time, thus giving a direction to time.

Ko

pp

or

ppp

Ko

W

s

W

s

d

W

d

KoKo Mixing
• Ko can mix withKo via virtual pp or ppp states: KoppKo orKop p pKo

These are DS = 2 transitions

1964: J.Cronin et al:

Observation of KL 2p

1964: Christenson, Cronin, Fitch and Turlay observed an excess of  50 events

with 490 < mpp < 510 MeV/c2 in the cosq distribution of the pp system w.r.t. the

KL line of flight. The dashed line shows the expectation for 3p decays

s

d

s

d

d

d

Direct and indirect CP Violation

It is usually described

by so-called

Penguin diagrams:

The relevant parameter is e’