status of solar neutrino oscillations - smu physics · 2015. 3. 10. · u if we consider 2 flavours...
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![Page 1: Status of Solar Neutrino Oscillations - SMU Physics · 2015. 3. 10. · u If we consider 2 flavours the mixing is characterized by a single angle θ analogous to the Cabibbo angle](https://reader036.vdocuments.us/reader036/viewer/2022071413/610a918d709d573317247323/html5/thumbnails/1.jpg)
Jorge G. MorfínCTEQ SS 2001St. Andrews,
Scotland
Status of Solar Neutrino Oscillations
With many thanks to Dave Wark -
RAL/ University of Sussex and
Stephen Brice - Fermilab
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandN
ext t
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dapt
ed f
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http
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.sns
.ias.
edu/
~jnb
/ The Solar Neutrino Problem
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandThe Solar Neutrino Problem
![Page 4: Status of Solar Neutrino Oscillations - SMU Physics · 2015. 3. 10. · u If we consider 2 flavours the mixing is characterized by a single angle θ analogous to the Cabibbo angle](https://reader036.vdocuments.us/reader036/viewer/2022071413/610a918d709d573317247323/html5/thumbnails/4.jpg)
Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandThe Solar Neutrino Problem
![Page 5: Status of Solar Neutrino Oscillations - SMU Physics · 2015. 3. 10. · u If we consider 2 flavours the mixing is characterized by a single angle θ analogous to the Cabibbo angle](https://reader036.vdocuments.us/reader036/viewer/2022071413/610a918d709d573317247323/html5/thumbnails/5.jpg)
Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandThe Solar Neutrino Problem
![Page 6: Status of Solar Neutrino Oscillations - SMU Physics · 2015. 3. 10. · u If we consider 2 flavours the mixing is characterized by a single angle θ analogous to the Cabibbo angle](https://reader036.vdocuments.us/reader036/viewer/2022071413/610a918d709d573317247323/html5/thumbnails/6.jpg)
Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandNeutrino Oscillations
u Let us assume that neutrinos have(different) masses - ∆m2
u Let us assume that the mass eigenstates arenot identical to the weak eigenstates
u If we consider 2 flavours the mixing ischaracterized by a single angle θ analogousto the Cabibbo angle in case of quarks
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandNeutrino Oscillations
u Recall that:
u Consider θ = 45°
( ) ( ) tiEii
ie0�t� −=
νe νµνµ
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandVacuum Oscillations
u In general this leads to the disappearance ofthe original neutrino flavour
u With the corresponding appearance of the“wrong” neutrino flavour
)E
L� m27.1(sin2sin1)(
222 θνν −=♦ eeP
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandThe MSW effect
u νe have an extra diagram for scattering fromelectrons.
u gives νe an “effective mass” in matter.
u can lead to resonant enhancement of oscillationsÜ the MSW effect
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandMSW effects on survival probabilities
Taken from
the US K
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AN
D proposal
Tak
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Mic
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Sm
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talk
, Mor
iond
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1
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandGlobal fit, 8B Flux a free parameter
u Includes:– Rates:
» Homestake
» SAGE
» GALLEX/GNO
» Super-K
– Super-K spectra
» day
» night
From Bahcall, Krastev, and Smirnov; hep-ph/0103179
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSterile ν solutions
u Includes:– Rates:
» Homestake
» SAGE
» GALLEX/GNO
» Super-K
– Super-K spectra
» day
» night
From Bahcall, Krastev, and Smirnov; hep-ph/0103179
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSmoking guns?u ν oscillations are consistent with the data,
but are they the right explanation?
u Other models have been proposed - FCNC,extra dimensions, violations of the EP,neutrino decay, neutrino magnetic moments,etc….
u What would be proof for oscillations?
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandThe Super-Kamiokande Detector
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSuper-K Elastic Scattering
Directly away from the Sun
Directly towards the Sun
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSmoking guns from solar ν? Pre-SNO
u The appearance of the wrong-flavorneutrinos in the beam - not seen yet forsolar neutrinos
u A variation of the rate with L/E—Spectral distortions—Seasonal variations
u Regeneration of neutrinos passingthrough the Earth.
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandDay/Night variation in Super-K
Tak
en f
rom
Mic
heal
Sm
yÕs
talk
, Mor
iond
200
1
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSNO
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandThe SNO Detector
1000 tons D2O
Acrylic Vessel
Phototube SupportStructure (PSUP)
104 8Ó PMTs6500 tons H2O
Surface: 2 km
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
Scotlandν Reactions in SNO
-Good measurement of νe energy spectrum-Weak directional sensitivity ∝ 1-1/3cos(θ)
-Measure total 8B ν flux from the sun.
NCxx
νν ++⇒+ npd
ES -- +⇒+ e_e_ x x
-Low Statistics-Strong directional sensitivity
CC -eppd ++⇒+νe
⇒
νe only
⇒Equal cross sectionfor all ν types
⇒All ν types butenhanced sensitivity to νe
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSNO run sequence
u Pure D2O– Good CC sensitivity
u Added Salt in D2O
– Enhanced NC sensitivity
u Neutral Current Detectors– 3He proportional counters in the
D2O
Neutron Detection Method
Capture on D
Capture on Cl
Capture on 3He
Event by event separation of CC and NCevents
n + 3He → p + t
n + 35Cl → 36Cl + Σγ … → e− (EΣγ = 8.6 MeV)
n + d → t + γ … → e− (Eγ = 6.3 MeV)
The Three Ph ases
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandThe enemy…..
βs and γs from decays in these chains interfere with our signals at low energies
And worse, γs over 2.2 MeVcause d + γ → n + p
Design called for: D2O < 10-15 gm/gm U/Th H2O < 10-14 gm/gm U/Th Acrylic < 10-12 gm/gm U/Th
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSignals in SNO
NC Salt(BP98)
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandAcrylic Vessel Assay
u Every piece sampledand tested
u Sample bonds tested
u Direct Assay byCherenkov light
AV well below(~1/10)
the target level of 2 ppt U/Th
ÒBerkeley BlobÓ9
+20 m 3 µg ÒThÓ-5
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandInstrumental Background Cuts
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSolar Neutrino Spectrum
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSNO cos(θ)sun distribution
Electron Angle with respect to the direction from the Sun
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSmoking Guns in SNO - 1
Charged-current spectrumis more sensitive to shape
distortions!
ES
CC
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSmoking Guns in SNO - 2
τµ νννν
++=
e
e
NC
CC
Bahcall etal., Phys. Rev. D 54, 5147 (1996)
Charged-Current to Neutral Currentratio is a direct signature
for oscillations
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSmoking Guns in SNO - 3
)(14.0ES
CC
e
e
τµ νννν
++=CC/ES Could also show
significant effects!
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandBorexino
ES in 300t superclean scintillator target
Under Construction, data taking end 2001
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandSignals and Backgrounds
Background suppression is challenging!
Signal suppression is promising!
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandOscillation Sensitivity
Reactor ν disappearance
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Jorge G. MorfínCTEQ SS 2001St. Andrews,
ScotlandConclusions
u Neutrino Oscillations very stronglyindicated.
u A real Solar ν smoking gun from SNOcollaboration.
u We live in interesting times…...