Neutrinos from the sun, earth and SN’s: a brief excursion

Aldo Ianni @ IFAE 2006

Pavia April 19th

Outline

Solar neutrinos: established facts Solar neutrinos: the future Neutrinos from the Earth: present & future Neutrinos from SN

Solar neutrinos

• Pure e beam

• Low energy• Long baseline (1013 cm)• Moving through high

density matter (at sun’s core ~150 g/cm3)

Solar neutrinos: observations

Experiment Type Thres. (MeV) Start

ES CC NC

Homestake(Cl-Ar) Radioch. 0.814 1968(stopped)

Kamiokande Cherenk. 7.0 1985(stopped)

SAGE Radioch. 0.233 1990

GALLEX Radioch. 0.233 1991(stopped)

Super-Kamiokande Cherenk. 5.0 1996*

GNO Radioch. 0.233 1999(stopped)

SNO Cherenk. 5.0 5.0 5.0 1999**

* Super-Kamiokande recovers full detector performances this year** SNO is planned to be shut down end of this year

Phenomenology of solar neutrino observations

1. Observations explained by neutrino oscillations + matter effects (MSW)

2. MSW leads to energy spectrum distortion and regeneration in the earth (day-night effect)

3. After SNO with NC the space of parameters gets reduced a lot

4. After KamLAND (assuming CPT) one dominant solution is tackled, namely the LMA

The great turn with SNO (>2001)

Established dominant solution

Taken from V. Barger et al hep-ph/0501247

Taken from G.L.Fogli et al hep-ph/0506083

Established facts

• 0.01% of solar neutrinos measured in real time• Data explained by the MSW LMA

• MWS defines mass hierarchy (m2 > m1)

• SNO CC/NC sets tan212<1

• MSW predicts up-turn of survival probability (spectral distortion) and regeneration

• MSW predicted effects not yet observed in SNO and SK due to high systematrics and still poor statistics

SNO data

A look at the future for Solar neutrinos

Measure in real time 99.99% of spectrum below 5 MeV : low energy detectors

Measure spectral distortion and regeneration : low energy and/or Mton water Cherenkov

Compare photon to neutrino luminosity : low energy solar neutrinos pp, pep, Be

Test new physics with sub-dominant effects : e.m. properties, mass varying neutrinos, non-standard interactions, light sterile neutrino

Borexino @ Gran SassoA pioneering experiment to search for sub-MeV 7Be solar neutrinos

1. Target medium : 100tons of high radiopurity organic liquid scintillator2. Detection channel: neutrino-electron elastic scattering (about 30cpd

expected)3. Signature : seasonal variation + Compton-like threshold due to

monoenergetic 7Be neutrinos4. Challenge : reduce background sources (238U, 232Th, 40K, 222Rn, 85Kr, 39Ar,

210Pb, 210Po) to get S/N>15. Lower detection energy : 250 keV limited to intrinsic 14C contamination6. Experimental strategies to reduce background : established by a 4-ton

scale prototype

pep neutrinos with Borexino

• Basic idea : reduce 11C cosmogenic background

• Method : tagging 11C by tackling the produced (95%) neutrons in spallation interactions

Taken from C. Galbiati et al PRC 71, 055805 (2005)

Remark: a pep measurement gives the same information of a pp one

Reduction of background for pep neutrinos

Cylindrical cut Around muon-track

Spherical cut aroundneutron Capture to reject 11C event

Neutron production

Muon track

11C tagged with the Borexino prototype

Taken from Borexino coll. hep-ex/0601035

11C decays + with Q~1MeV and min Measured production rate ~0.14 events/day/ton at Gran Sasso depth

Predictions to falsify with BorexinoBahcall et al, JHEP 8 (2004) 016, hep-ph/04060294

2 monoenergetic beams to test solar physics and neutrino physics

pep new goal for KamLAND-II

Taken from Nakajima, La Thuile

pep for SNO+

• Main physics goal for 1kton organic liquid scintillator after SNO

• At SNOlab 11C is reduced by a factor of about 10 with respect to Gran Sasso and 70 to Kamioka

Searching for pp solar neutrinos

Goal : no 14C or a strong tagging Solution-I : liquid Ne(CLEAN) or Xe(XMASS), detection

channel = ES Solution-II : loaded 115In liquid scintillator (LENS)

Solution-III : 100Mo sheets + plastic scintillator

Time scale : due to experimental difficulties >2010

)(100100 TceMoe

Conclusions on solar neutrinos

• Wonderful effort made by researchers (both on experiments and theory) to collect and explain data

• Unique opportunity with low energy solar neutrinos both in astrophysics and neutrino physics

• A great challenge for experiments• pep neutrinos measurable• Not too much to add to oscillation parameters

Neutrinos from the earth: geoneutrinos

MeV

Th

MeV

U

dEE

dEE

806.1

806.1

150.0)(

383.0)(

Goals: 1. determine distribution of U, Th and K in earth interior2. measure total heat due to radioactivity [earth gives 30-44 TW]3. determine hot spots (geo-reactor etc) if any

Detection of geoneutrinos

MeV

Th

MeV

U

Th

U

cmdEEE

cmdEEE

MeVEdEE

MeVEdEE

806.1

245

806.1

245

0

0

1030.1)()(

1023.4)()(

22.2)(

91.3)(

1 1.5 2 2.5 3

0

0.1

0.2

0.3

0.4

0.5

Above 1.8MeV (only U,Th): inverse-beta decay (strong tagging)Below 1.8MeV (K as well): elastic scattering (weak tagging)

The earth looked through geoneutrinos

Geoneutrino flux (Fiorentini et al)

Middle oceanic crust SNO+ Borexino Lena 30kt KamLAND

Present observations @ KamLAND

• Energy window: 0.9<E<2.6 MeV• Observed : 152 events• Background : 127 ± 13 events

• Geoneutrino signal : 25+19-18 events

• Main sources of background : reactors and 13C(,n)16O with ’s from 210Po

Geoneutrinos @ Gran Sasso

Borexino 300t target mass : S/N~1

LENA in Finland

• Proposed a 30kt multi-puspose liquid scintillator based on PXE

• PXE tested with the Borexino prototype• High statistics and angular resolution (26°) may

allow 40K neutrino measurement looking toward the earth’s nucleus (if any hidden K in there!)

Conclusions on geoneutrinos

• U and Th geoneutrinos to get information on radiogenic heat on earth and test earth formation mechanism

• U and Th geoneutrinos easy to detect far away from reactors and with a low background liquid scintillator

• More detectors in different locations to reduce uncertainties

• First (2) evidence of geoneutrinos from KamLAND• Hope : detect K neutrinos somehow. See M. Chen talk at

Neutrino Geophysics, Honolulu, Hawaii December 15, 2005

•

SN neutrinos

Detection of SN neutrinos [1]

• SN neutrinos are affected by oscillations:

• In the standard figure each flavor has a peculiar mean energy and temperature (Te~3.5MeV, Tanti-e~5MeV, Tx~8MeV with <E>~3.15T)

• Uncertainty of standard figure ~50%• SN in galaxy: 40±10 yr/SN.

Long-term stability of detectors required• in order to measure the temperature and

energy of x’s and their antiparticles

one needs a spectral signature

)()1( xSN

eeSNeee

Earthe FPFPF

0 10 20 30 40 50 60

0

0.02

0.04

0.06e

anti-e

x

Detection of SN neutrinos [2]

• SuperKamiokande will play a crucial role with ~8000 events for inverse-beta decay and ~700 for NC on 16O @10kpc

• SuperKamiokande will see ~300 events of antineutrino @50kpc in the LMC

• SNO has a unique channel e +dppe- for studying the neutronization phase but it will be shut down in 2007

• NC with neutrino-proton elastic scattering to measure x’s and their antiparticles with a spectral signature in low threshold liquid scintillators (Borexino, KamLAND)

• Italy has a great opportunity with LVD, T600 and Borexino at the same location

Detection of SN neutrinos [3]

Detection channel N, Borexino N, LVD

+e- +e- 5 14

inverse-beta decay 60 400

+p +p 55 5

12C(,)12C* [E=15.1MeV] 9(8 for anti-) 27(25 for anti-)

12C(anti-,e+)12B 3 11

12C(,e-)12N 9 28

56Fe(,e-)56Co+56Fe(anti-,e+)56Mn - 80

Conclusions on SN neutrinos

• A future galactic SN will yield 100-1000 events in the existing detectors for the well tagged channel of inverse-beta decay (electron-antineutrino spectral signature)

• Neutrino-proton elastic scattering will allow to measure the energy and temperature of mu and tau (anti)neutrinos

• Collection of nice data for the cooling phase, not as well for the neutronization phase after SNO shut-down

• Future proposed LENA to see modulation of spectra due to matter effect in the earth