PHYS 5326 – Lecture #11

Monday, Feb. 24, 2003 PHYS 5326, Spring 2003Jae Yu

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PHYS 5326 – Lecture #11Monday, Feb. 24, 2003

Dr. Jae Yu

1. Brief Review of sin2W measurement

2. Neutrino Oscillation Measurements1. Solar neutrinos2. Atmospheric neutrinos

3. A lecture on neutrino mass (Dr. Sydney Meshkov from CalTech)

•Next makeup class is Friday, Mar. 14, 1-2:30pm, rm 200.


2

How is sin2W measured?

• Cross section ratios between NC and CC proportional to sin2W

• Llewellyn Smith Formula:

)(CC

)(CC

W4

W22

)(CC

)(NC)(

σ

σ1θsin

95

θsin21

ρσ

σR

WEMweak QIcoupling 2)3( sin)3(weakIcoupling


3

SM Global Fits with New ResultsWithout NuTeV dof=20.5/14: P=11.4%With NuTeV dof=29.7/15: P=1.3%Confidence level in upper Mhiggs limit weakens slightly.

LEP EWWG: http://www.cern.ch/LEPEWWG

http://www.cern.ch/LEPEWWG


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Tree-level Parameters: and sin2W(on-shell)

• Either sin2W(on-shell) or 0 could agree with SM but both agreeing

simultaneously is unlikely

150GeV

Mln0.00032

50GeV

175GeVM0.00022θδsin

H

2

22tshell)(On

W2

0.0400.9983ρ

0.00310.2265θsin

0

W2


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• R can be expressed in terms of quark couplings:

Model Independent Analysis

2R

2L-

--

grgR 1

XN

XN

Where

2

1

XνNσ

XNνσr

Paschos-Wolfenstein formula can be expressed as

2R

2L

νν

W22

νCC

νCC

νNC

νNC gg

r1

rRRθsin

2

1ρ

σσ

σσR


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Model Independent Analysis

Difficult to explain the disagreement with SM by:Parton Distribution Function or LO vs NLO or Electroweak Radiative Correction: large MHiggs


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Linking sin2W with Higgs through Mtop vs MW

150GeVM

ln0.0003250GeV

175GeVM0.00022θδsin H

2

22tshell)(On

W2

One-loop correction to sin2W


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Oscillation Probability• Substituting the energies into the wave function:

E

tmiE

mpitt 2expcossin2exp22

121

where and .22

21

2 mmm pE

• Since the ’s move at the speed of light, t=x/c, where x is the distance to the source of .

• The probability for with energy E oscillates to e at the distance L from the source becomes

E

LmP e

222 27.1

sin2sin


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Why is Neutrino Oscillation Important?• Neutrinos are one of the fundamental constituents in nature

– Three weak eigenstates based on SM• Left handed particles and right handed anti-particles only

– Violates parity Why only neutrinos?– Is it because of its masslessness?

• SM based on massless neutrinos• Mass eigenstates of neutrinos makes flavors to mix• SM in trouble…• Many experimental results showing definitive evidences of

neutrino oscillation– SNO giving 5 sigma results


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Sources for Oscillation Experiments• Must have some way of knowing the flux

– Why?• Natural Sources

– Solar neutrinos– Atmospheric neutrinos

• Manmade Sources– Nuclear Reactor– Accelerator


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Oscillation Detectors• The most important factor is the energy of neutrinos

and its products from interactions• Good particle ID is crucial• Detectors using natural sources

– Deep under ground to minimize cosmic ray background– Use Cerenkov light from secondary interactions of

neutrinose + e e+X: electron gives out Cerenkov light CC interactions, resulting in muons with Cerenkov light

• Detectors using accelerator made neutrinos– Look very much like normal neutrino detectors

• Need to increase statistics


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Solar Neutrinos• Result from nuclear fusion process in the Sun• Primary reactions and the neutrino energy from

them are:

eLieBe 77

158B

0.867Be

1.44pep

0.42pp

E End point (MeV)ReactionName

eeDpp

eDpep

eeHeB 48 2


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Solar Neutrino Energy Spectrum


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Comparison of Theory and Experiments


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Sudbery Neutrino Observatory (SNO)•Sudbery mine, Canada•6800 ft underground•12 m diameter acrylic vessel•1000 tons of D2O•9600 PMT’s

Elastic Scattering

Neutral Current


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SNO e Event Display


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Solar Neutrino Flux


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SNO First Results

0.35


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Atmospheric Neutrinos• Neutrinos resulting from the atmospheric

interactions of cosmic ray particles to e is about 2 to 1– He, p, etc + N ,K, etc

e+e+

– This reaction gives 2 and 1 e

• Expected flux ratio between and e is 2 to 1• Form a double ratio for the measurement

The

Exp

NN

NN

R

e

e


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Super Kamiokande•Kamioka zinc mine, Japan• 1000m underground•40 m (d) x 40m(h) SS•50,000 tons of ultra pure H2O•11200(inner)+1800(outer) 50cm PMT’s•Originally for proton decay experiment•Accident in Nov. 2001, destroyed 7000 PMT’s•Dec. 2002 resume data taking


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Atmospheric Neutrino Oscillations


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Super-K Atmospheric Neutrino Results


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Super-K Event Displays

Stopping 3


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Other Experimental Results

Soudan 2 experiment

Macro experiment


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Accelerator Based Experiments• Mostly from accelerators• Long and Short baseline experiments

– Long baseline: Detectors located far away from the source, assisted by a similar detector at a very short distance (eg. MINOS: 370km, K2K: 250km, etc)

• Compare the near detector with the far detector, taking into account angular dispersion

– Short baseline: Detectors located at a close distance to the source

• Need to know flux well

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PHYS 5326 – Lecture #11