8/5/2002Ulrich Heintz - Quarknet 20021 neutrino puzzles Ulrich Heintz Boston University .
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Transcript of 8/5/2002Ulrich Heintz - Quarknet 20021 neutrino puzzles Ulrich Heintz Boston University .
8/5/2002 Ulrich Heintz - Quarknet 2002 1
neutrino puzzlesUlrich Heintz
Boston University
http://physics.bu.edu/quarknet/2002/neutrinos.ppt
8/5/2002 Ulrich Heintz - Quarknet 2002 2
outline
• the neutrino
• atmospheric neutrinos
• solar neutrinos
• accelerator neutrinos
• does it make sense?
8/5/2002 Ulrich Heintz - Quarknet 2002 3
the neutrino in the standard model
e e u d0.511 MeV 0 a few MeV a few MeV
c s106 MeV 0 1100 MeV 150 MeV
t b1.8 GeV 0 175 GeV 4.2 GeV
leptons quarksspin = ½ (fermions)
The Standard Model
8/5/2002 Ulrich Heintz - Quarknet 2002 4
neutrino properties• how do we detect neutrinos?
– no charge, no color– neutrinos interact only by the weak force– can penetrate entire earth without interacting– need lots of neutrinos and big detectors
• limits on the neutrino masses– mass of e < 3 eV ( decay of 3H)
– mass of < 0.19 MeV (+!++)
– mass of < 18 MeV (- ! - - + )
8/5/2002 Ulrich Heintz - Quarknet 2002 5
origin of atmospheric neutrinos• cosmic rays
• interact in upper atmosphere
decaye decay
• expect two per e
• energy ¼ 1 GeV
+
p
+
e+
e
8/5/2002 Ulrich Heintz - Quarknet 2002 6
neutrino detection• neutrino interaction with matter
– electron neutrinos (e) produce electrons (e)
– muon neutrinos () produce muons ()
– tau neutrinos () produce taus ()
e
ee
e
W
ee
W
8/5/2002 Ulrich Heintz - Quarknet 2002 8
Super Kamiokande
41 m
39 m3 km 2 km
1 km
outer detector:1867 8” tubes
50 ktons H2O
inner detector:11146 20” tubes
8/5/2002 Ulrich Heintz - Quarknet 2002 14
neutrino oscillations
e
x
c
p
mmp e
222
212
2cos12sin
2
1)(
strength of mixing
distance travelled
momentum
mass difference
8/5/2002 Ulrich Heintz - Quarknet 2002 15
neutrino oscillations• p = 400 MeV
• range of momenta centered on 400 MeV
p(
!
e)
distance traveled (m)
0.00
0.20
0.40
0.60
0.80
1.00
0 50 100 150 200 250 300 350 400 450
8/5/2002 Ulrich Heintz - Quarknet 2002 16
atmospheric neutrinos• what does this mean?
– disappear– e
• would see e
–
• is hard to see
– from top• no oscillations
– from bottom• oscillations
– limit parameters
8/5/2002 Ulrich Heintz - Quarknet 2002 18
neutrino mixing parameters• maximal mixing
– sin22 ¼ 1
• small m2
– m2 ¼ 10-3 eV2
8/5/2002 Ulrich Heintz - Quarknet 2002 19
K2K• to check Super-K results
– shoot beam from KEK to Kamiokande (K2K)
energy ¼ 1.3 GeV
– count events at Super-K
• if there are oscillations expect a deficit of ’s (disappearance)
• not enough energy to make ’s (appearance)
8/5/2002 Ulrich Heintz - Quarknet 2002 22
do they oscillate?• beam events at
Super-K– observe 56– expect 80– probability for this
without oscillations: ¼ 1%
8/5/2002 Ulrich Heintz - Quarknet 2002 23
Super-K accident• on November 12, 2001
– 6779 of 11146 inner tubes collapsed
– rebuild with 47% of tubes by fall 2002– complete rebuild after that
8/5/2002 Ulrich Heintz - Quarknet 2002 25
reactions in the sun
p+p2H+e++ep+e-+p2H+e
2H+p3He+
3He+3He4He+2p 3He+p4He+e++e
3He+4He7Be+
7Be+p8Be+8Be8B* +e+ +e
8B*4He+4He
7Be+e-7Li+e
7Li+p4He+4He
8/5/2002 Ulrich Heintz - Quarknet 2002 27
solar neutrino experiments• SAGE, GALLEX
– e +71Ga71Ge+e flux = 0.558 SSM
• Homestake– e+37Cl37Ar+e- flux = 0.33 SSM
• Super-K– x +e- x +e- flux = 0.46 SSM
8/5/2002 Ulrich Heintz - Quarknet 2002 30
Sudbury Neutrino Observatory• Creighton Mine,
Sudbury, Ontario
• 1000 tonnes D2O in 12 m diameter acrylic vessel
• 9500 PMTs in 17 m diameter support
• 7000 tonnes H2O
• Surrounded by norite rock
2039m to surface.
1011m to sun.
8/5/2002 Ulrich Heintz - Quarknet 2002 32
neutrino reactions in SNO• “charged current”
• “neutral current”
• “elastic scattering”
ee
W
n pp
pxx
Z
nnp
p
electron neutrinos only
all neutrinos
e
ee
e
Z mostly electron neutrinos
8/5/2002 Ulrich Heintz - Quarknet 2002 33
observed neutrino flux
154.0
154.0 eeseees
encenc
cceecc
/s /cm66.041.3/s /cm27.039.2
/s /cm64.009.5
/s /cm11.076.1/s /cm11.076.1
22
2
22
es
nc
ecc
8/5/2002 Ulrich Heintz - Quarknet 2002 34
observed neutrino flux
ssm = 5.05+1.01-0.81 sno = 5.09+0.44
-0.43+0.46-0.43
8/5/2002 Ulrich Heintz - Quarknet 2002 35
neutrino oscillation parameters• maximal mixing
– sin22 ¼ 1
• small m2
– m2 < 10-4 eV2
8/5/2002 Ulrich Heintz - Quarknet 2002 36
accelerator neutrinos• LSND (Los Alamos)
– + + +
– + e+ +e +
– observe e
– oscillations from
• Karmen (Rutherford Lab)– no oscillation signal
• Miniboone (Fermilab)– starts 2002– will resolve issue
8/5/2002 Ulrich Heintz - Quarknet 2002 37
does it make sense?• three oscillation signals
– atmospheric neutrinos m2 ¼ 10-3 eV2
– solar neutrinos m2 ¼ 10-4 eV2
– accelerator neutrinos m2 ¼ 0.1 eV2
• incompatible with three neutrinos– one of the experiments is wrong– there is a 4th neutrino
8/5/2002 Ulrich Heintz - Quarknet 2002 39
summary• strong evidence for neutrino oscillations
– from atmospheric neutrinos ( ?)
– from solar neutrinos (e or ?)
• at least one neutrino must have mass
• accelerator neutrino oscillation signal – mildly inconsistent experiments– not compatible with these and three neutrinos
• is there a 4th (sterile) neutrino?