Neutrinos: At the Heart of the Matter?

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Neutrinos:At the Heart

of the Matter?Kevin McFarland

University of Rochester5 August 2012

5 August 2012K. McFarland, Neutrino Frontier

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Neutrino Frontier

5 August 2012K. McFarland, Neutrino Frontier

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And each time we look over the horizon…

5 August 2012K. McFarland, Neutrino Frontier

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Foci for Current Work

• Neutrinos as particleso Masseso Mixing and CP violation

• Neutrinos as probeso Of the largeo Of the small

5 August 2012K. McFarland, Neutrino Frontier

Figure from C. Walter, Super-Kamiokande Collaboration

γ ν

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Foci for Current Work

• Neutrinos as particleso Masseso Mixing and CP violation

• Neutrinos as probeso Of the largeo Of the small

5 August 2012K. McFarland, Neutrino Frontier

Figure from G. Kane, Scientific Am., 2003

CERN Publications

K. McFarland, Neutrino Frontier 6

Neutrino Flavor• Neutrinos were discovered by

o the final state positron tags flavoro we’ve seen neutrinos

produce all three charged leptons in weak interactions

• The Z boson decays into three (and only three) neutrinos

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p e n

ee

K. McFarland, Neutrino Frontier 7

Neutrino FlavorMixing

• If neutrinos mass states mix to formflavors (Pontecorvo)

• and the masses are different…o flavors of neutrinos can change in flight

• Explains Davis’ “solar neutrino puzzle”o since only electron flavor

neutrinos induce ν+n→p+e-

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e

flavor,mass eige

fn

lavstates,

or

i ii

U

K. McFarland, Neutrino Frontier 8

Neutrino Flavor Oscillation

• Each neutrino wavefunctionhas a time-varying phase in its rest frame,

• Now, imagine you produce a neutrino of definite momentum but is a mixture of two masses, m1, m2

• so pick up a phase difference in lab frame

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/iEte

22 2 1

1 1 2

22 2 2

2 2 2

1

1

mE p m ppmE p m pp

2 21 2 1 2( ) ( ) Lci E E i m m

p

K. McFarland, Neutrino Frontier 9

• Phase differencecan cause change of flavor in a vacuum

o

more generally, mixing need not be maximal

Neutrino Oscillation (cont’d)

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cos sinsin cos

i

j

only two generations for now!

2 21 2 1 2( ) ( ) Lci E E i m m

E

K. McFarland, Neutrino Frontier 105 August 2012

Neutrino Oscillation (cont’d)

• For two generations…

o Oscillations require mass differenceso Oscillation parameters are mass-squared differences,

dm2, and mixing angles, .• One correction to this is matter… changes , L

dep.

ELmm

P4

)(sin2sin)(

21

2222

Wolfenstein, PRD (1978)

22

22

22

)2cos(2sin

)2cos(2sin2sin2sin

xLL

x

M

M

nm

EnGx eF2

22

e- density

appropriate units give the usual

numerical factor 1.27 GeV/km-

eV2

K. McFarland, Neutrino Frontier 115 August 2012

Solar Neutrinos: SNO

• D2O target uniquely observed:o charged-currento neutral-current

• The former is onlyobserved for e(lepton mass)

• The latter for all types• Solar flux is consistent

with modelso but not all e at earth

X Xd pn ed ppe

K. McFarland, Neutrino Frontier 125 August 2012

KAMLAND• Sources were

Japanesereactorso 150-200 km

for most offlux. Rate uncertainty ~6%

• 1 kTon scint. detector inold Kamiokande caverno overwhelming confirmation

that neutrinos change flavorin the sun via mattereffects

K. McFarland, Neutrino Frontier 135 August 2012

Atmospheric Neutrinos

• Neutrino energy: few 100 MeV – few GeV• Flavor ratio robustly predicted• Distance in flight: ~20km (down) to 12700 km

(up)

K. McFarland, Neutrino Frontier 145 August 2012

Super-Kamiokande• Super-K

detector hasexcellent e/separation

• Up / down difference: L/E

• Muons distorted, electrons not; so mostly

old, but good data!

2004 Super-K analysis

K. McFarland, Neutrino Frontier 155 August 2012

MINOS735km baseline5.4kton Far Det.1 kton Near Det.Running since early

2005

Precise measurement of disappearance energygives dm2

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K. McFarland, Neutrino Frontier 165 August 2012

Two Mass Splitings:

Three Generations

• Oscillations have told us the splittings in m2, but nothing about the hierarchy

• The electron neutrino potential (matter effects) can resolve this in oscillations, however.

figures courtesy B. Kayser

dmsol2 dm12

2≈8x10-5eV2 dmatm2 dm23

2≈2.5x10-

3eV2

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Oases over the horizon?

5 August 2012K. McFarland, Neutrino Frontier

Observation of A. deRujula at Neutrino 2000:

If mass differences were not matched to…• Solar densities (small δm2)• the size of the earth (large δm2)… we would probably not have discovered neutrino oscillations

dmsol2 dm12

2≈8x10-5eV2

dmatm2 dm23

2≈2.5x10-3eV2

Emboldened, neutrino physicists keep gambling…

K. McFarland, Neutrino Frontier 185 August 2012

Three Generation Mixing

• Note the new mixing in middle, and the phase, d

slide courtesy D. Harris

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Two Paths for νμ→νe?

• If “reactor” mixing, 13, is small, but not too small, there is an interesting possibility

• At atmospheric L/E,

dm232, 13

dm122, 12

e

2 22 2 2 1( )( ) sin 2 sin

4em m LP

E

SMALLLARGE

SMALLLARGE

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Implication of two paths• Two amplitudes

• If both small,but not too small, both can contribute ~ equally

• Relative phase, d, between them can lead toCP violation (neutrinos and anti-neutrinos differ) in oscillations!

• CP violation in leptons, along with Majorana masses, are key ingredients for leptogenesis of baryon asymmetry of Universe.

dm232, 13

dm122, 12

e

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13 in 2011: Not Zero!• T2K, an accelerator experiment,

showed a signal of 6 eventso 1.5 expected if 13=0

• Consistent, but less significant, indication from MINOS shortly after

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13 in 2012: Large!• Two reactor experiments recently showed

overwhelming evidence for large 13.o Both place detectors near and far (~1km) from

reactorso Look for a small

rate differencebetween twolocations

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K. McFarland, Neutrino Frontier 23

13 in 2012: Daya Bay

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Figures from K. Heeger

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13 in 2012: RENO

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Figures from S.B. Kim

K. McFarland, Neutrino Frontier 255 August 2012

Two paths!• Two amplitudes

• Now we know the measurement of d and CP violation in oscillations is possible.

• Bring on megaton detectors and multi-megawatt sources…o LBNE, Hyper-Kamiokande, LAGUNA, etc.

dm232, 13

dm122, 12

e

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Implications of Large 13• If 13 is large, then one of the two paths

is larger than the other.• This implies large signals, but small CP

asymmetries

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dm232, 13

dm122, 12

e

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Implications of Large 13

• Quantitative analysis to illustrate this expected behavioro Fractional asymmetry

decreases as 13 increases• We live here• Statistics are (relatively)

high, so the challenge will be controlling systematic uncertainties.

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NeutrinolessDouble Beta Decay

• Signature of Majorananeutrino mass

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~Now

In progress

F. Piquemal, Neutrino 2012

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Foci for Current Work

• Neutrinos as particleso Masseso Mixing and CP violation

• Neutrinos as probeso Of the largeo Of the small

5 August 2012K. McFarland, Neutrino Frontier FNAL Visual Media Services

Joha

nnes

Blü

mer

Stanford group, KAMLAND

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Geoneutrinos

5 August 2012K. McFarland, Neutrino FrontierSteve Dye, Neutrino 2012

Stanford group, KAMLAND

• Radioactive decays in mantle contribute significantly to internal heating of earth

• Neutrinos from these decays have been discovered

• Weak evidence forexcess overamount fromcrust

31A. Ishihara, Neutrino 2012

Ultra-High Energy Neutrinos

• IceCube (km3 detector at south pole) has observed two events, likely 1000-10000 TeV neutrinos

• Analysis is underway(note scale: “photoelectrons”)

5 August 2012K. McFarland, Neutrino Frontier

Joha

nnes

Blü

mer

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Neutrinos and Nucleons• MiniBooNE data sets have been an interesting

challenge for this community.

• In brief, models of nucleus effect on both initial and final state are probably too naïve.

• Challenge is to develop workable models of these interactions to compare to data and use in oscillation measurements.

5 August 2012K. McFarland, Neutrino Frontier

Alcaraz et al, AIP Conf. Proc.

1189.145 (2009)

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NuWro: T.Golan, C. Juszczak, J. Sobczyk. arXiv:1202.4197

Neutrino-Nucleon (cont’d)• New experiments (MINERvA, T2K, NOvA) will

expand detector capabilities, energy range, number of nuclei studied and statistics over current data.

• I.e., first results from MINERvA recently availableo Small fraction of data on one target, preliminary and large systematics.

5 August 2012K. McFarland, Neutrino Frontier

Anti-neutrino CCQE on scintillator (CH)

p n candidate

n candidate

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Conclusions• Nature hands us another gift: large 13

o New and bold, and potentially very long term, efforts to discover CP violation in neutrino oscillation.

o Very challenging technically, and ambitious technically• Neutrinoless double beta decay still ungifted

o Steady and hard-won progress towards sufficiently sensitive experiments.

• Running and future experiments using neutrinos as probes solider on.o IceCube now at full size. Coming years could be exciting.o Low energy neutrino detection for geo-neutrinos, reactor monitoring is

an exploding field. Many interesting proposals.o Neutrino-nucleus scattering physics should see a wealth of new data

with MINERvA, T2K, NOvA detectors. The interplay between theory and experiment is familiar to those engaged in our main topic for this week.

o Next new idea for harnessing neutrinos?

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BackupSuperuminal

More on CCQE

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Do Neutrinos Go Faster Than Light?

• No

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Do Neutrinos Go Faster Than Light?

• No

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K. McFarland, Neutrino Interactions 38

Short-Range Correlations

5 June 2012

Recent Jlab studies of 12C quasi-elastic scattering have demonstrated significant probabilities to see multiple nucleons knocked out. [R. Subedi et al., Science 320, 1476 (2008)]

• Kinematics of interaction may be altered because scattering in nuclear environment occurs from a correlated pair ~20% of the time.

• Not a new idea to apply toquasi-elastic scattering. Evidence in charged leptonscattering now strengthens the case.

Dekker et al., PLB 266, 249 (1991)Singh, Oset, NP A542, 587 (1992)Gil et al., NP A627, 543 (1997)J. Marteau, NPPS 112, 203 (2002)Nieves et al., PRC 70, 055503 (2004)Martini et al., PRC 80, 065001 (2009)

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Martini et al, PRC 81, 045502 (2010)

Δσ

Explains MiniBooNE?• From the 12C experiment and calculations,

expect a cross-section enhancement from correlated process:

5 June 2012K. McFarland, Neutrino Interactions

New work since Martini proposalNieves et al., arXiv:1106.5374 [hep-ph]Bodek et al., arXiv:1106.0340 [hep-ph]Amaro, et al., arXiv:1104.5446 [nucl-th]Antonov, et al., arXiv:1104.0125Benhar, et al., arXiv:1103.0987 [nucl-th]Meucci, et al., Phys. Rev. C83, 064614 (2011)Ankowski, et al., Phys. Rev. C83, 054616 (2011)Nieves, et al., Phys. Rev. C83, 045501 (2011)Amaro, et al., arXiv:1012.4265 [hep-ex]Alvarez-Ruso, arXiv:1012.3871[nucl-th]Benhar, arXiv:1012.2032 [nucl-th]Martinez, et al., Phys. Lett B697, 477 (2011)Amaro, et al., Phys. Lett B696, 151 (2011)Martini, et al., Phys. Rev C81, 045502 (2010)[compilation by G.P. Zeller]

νμn→μ-p + νμ(np)corr.→μ-pp

MINERvA Neutrino and Anti-Neutrino CCQE in Energy

BinsQ2 distributions compared to GENIE, MA=0.99 GeV/c2

5 June 2012K. McFarland, Neutrino Interactions 40

Low Energy, 2-4 GeV

High Energy, 4-10 GeV

Similar trendsin Q2 in both beams, energies

20% of our data on CH