The importance of low energy solar neutrino experiments
This presentation is the property of its rightful owner.
Sponsored Links
1 / 24

The Importance of Low-Energy Solar Neutrino Experiments PowerPoint PPT Presentation


  • 83 Views
  • Uploaded on
  • Presentation posted in: General

The Importance of Low-Energy Solar Neutrino Experiments. Thomas Bowles Los Alamos National Laboratory. Markov Symposium Institute for Nuclear Research 5/13/05. Nuclear Physics. Standard Solar Model. Nuclear Physics. Comparison of measured rates and Standard Solar Model

Download Presentation

The Importance of Low-Energy Solar Neutrino Experiments

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


The importance of low energy solar neutrino experiments

The Importance of Low-EnergySolar Neutrino Experiments

Thomas Bowles

Los Alamos National Laboratory

Markov Symposium

Institute for Nuclear Research

5/13/05

Nuclear Physics


Standard solar model

Standard Solar Model

Nuclear Physics


The importance of low energy solar neutrino experiments

Comparison of measured rates and Standard Solar Model

(After 30+ years of effort)

Nuclear Physics


The importance of low energy solar neutrino experiments

Flavor Content of the Solar 8B Neutrino Flux

Detecting Neutrinos in SNO

CC Interaction

Sensitive to electron neutrinos only

NC Interaction

Equally sensitive to all flavours

ES Interaction

Sensitive to all flavors,

but most sensitive to electron neutrinos

Nuclear Physics


What we know

What We Know

  • Flux of 8B n’s has a large non-ne component

  • Survival probability Pee for En > 5 MeV is

    essentially independent of En

  • Pee for n’s of lower energy (p-p) is larger

  • There is no significant (> 2s) D/N asymmetry

All observations are consistent with

the following hypotheses:

Mass-induced flavor oscillations

(with LMA as the favored solution)

Nuclear Physics


Neutrino oscillations

Neutrino Oscillations

If neutrinos have mass leptons can mix:

Flavor eigenstates are a mixture of mass eigenstates

States evolve with time or distance

The ne survival probability for two flavor mixing is:

Nuclear Physics


Reactor neutrino experiment

Photomultipliers

Reactor Neutrino Experiment

Terrestrial Neutrinos

KamLAND is a 1 kton

liquid scintillator detector

that observes from a

number of reactors in

Japan at an average

distance of 180 km

(NOBS - NBG)/NEXP =

0.611 ± 0.085 (stat)

± 0.041 (syst)

KamLAND observes a

significant deficit of

neutrinos and confirms

solar neutrino LMA

neutrino oscillation solution

Nuclear Physics


Neutrino properties

Neutrino Properties

  • What We Know

    • There are 3 types of neutrinos : ne , nm , nt

    • Neutrinos have mass and oscillate

    • Oscillation parameters (Dm2 and tan2q) known to ~ 30%

    • Neutrino masses are small

      • 50 meV < mn < 2.8 eV (90% CL)

        • Lower limit from atmospheric neutrino results

        • Upper limit from tritium beta decay results

      • Neutrinos account for at least as much mass in the Universe

      • as the visible stars

Nuclear Physics


Neutrino properties1

Neutrino Properties

  • What We Don’t Know - Neutrino Properties

    • Are neutrinos their own antiparticles? (Majorana n)

  • What is the absolute scale for neutrino mass?

  • Is the mass scale normal ordered or inverted hierarchy?

  • Are there sterile neutrinos?

  • What are the elements of the MNS mixing matrix?

  • Is CP / CPT violated in the neutrino sector?

  • What We Don’t Know - Neutrino Astrophysics

    • Is the Standard Solar Model correct?

  • What is the flux of solar neutrinos below 5 MeV?

  • What is the flux of CNO neutrinos?

  • What is the radial temperature distribution of the Sun?

  • How do neutrino properties affect supernovae?

Nuclear Physics


The importance of low energy solar neutrino experiments

Physics Program for FutureSolar Neutrino Experiments (I)

  • Directly observe the 99.99% of solar neutrinos

  • that are below 5 MeV

    Direct test of solar models (p-p, 7Be, CNO)

Uncertainties in the solar neutrino fluxes

p-p7BeCNO8B

Present15%35%100%6%

With present12% 8%100%4%

generation dets

Future expts1-3%2-5% 10-20% 2-4%

  • Measurement of CNO neutrinos provides an important test:

    • 1.5% of the Sun’s energy is from the CNO cycle

    • CNO burning is crucial in first 108 yr convective stage

    • Provides test of initial metallicity of the Sun

  • Determine unitarity / dimension of n mixing matrix

  • Goal is to measure the flavor composition

  • of the p-p solar n’s to 1% precision in

  • a model-independent manner

  • Requires CC and ES/NC measurement

  • (assuming active oscillations)

  • Model-indep test for sterile n’s using measured

  • oscillation parameters (p-p + KamLAND)

 Can achieve ≈ 13% sensitivity (90% CL)

Nuclear Physics


The importance of low energy solar neutrino experiments

Physics Program for FutureSolar Neutrino Experiments (II)

  • Use p-p neutrinos as “standard candle”

    Precision test for CPT violation comparing

    and

  • Model-dependent cross-check for sterile neutrinos

  • with ≈ 2% sensitivity (90% CL)

Measurement of the p-p rate to 1% provides knowledge of q12

to allow a search for CPT violation at a scale of 10-20 GeV

Compared to the present CPT test from the upper limit on

the mass difference in the kaon system of 4.4 x 10-19 GeV

Various scenarios imply that the sterile component of solar

neutrino fluxes may be energy dependent

  • Provide improved precision of mixing angle

  • Future p-p solar neutrino experiments offer the best prospect

  • for improving our knowledge of q12

 Low-energy solar neutrino expts must be part of any

full study of sterile neutrinos

  • Search for n magnetic moment with improved

  • sensitivity (contribution  1/Te)

Qsolar required to determine mn in 0n-bb decay

 Expect sensitivity of 10-11mB

Nuclear Physics


The importance of low energy solar neutrino experiments

p-p Solar Neutrino Experiments:Physics Goals

fTotal= fActive + fSterile

Search with sterile neutrino components with

an order of magnitude improved sensitivity

Future Sensitivity

Present limits

Nuclear Physics


The importance of low energy solar neutrino experiments

Next-Generation Solar Neutrino Experiments

What is required of future experiments:

Measurement of ne fluxes:

SourceTo matchTo matchTo match

current expts:projected expts:LMA prediction:

p-p 15% 12% 2%

7Be 35% 8% 5%

CNO100%100%100%

pep100%100% 2%

8B 6% 4% 6%

Mixing parameters:

To match current limits on tan2q: 3% p-p accuracy

To match projected SNO, KamLAND limits: 2% p-p accuracy

Nuclear Physics


The importance of low energy solar neutrino experiments

Future Experiments - Borexino

  • Looks at solar 7Be line (862 keV)

  • Precision measurement of q12

  • Will provide test of SSM for 7Be flux

  • Possible future extension to p-p neutrinos

Nuclear Physics


The importance of low energy solar neutrino experiments

p-p Solar Neutrino Experiments

Charged-Current Experiments:

LENS, MOON

Goal: Measure ne component of p-p (7Be)

with 1-3% (2-5%) accuracy

Elastic Scattering Experiments:

CLEAN, HERON, TPC, XMASS

Goal: Measure ne / nm, nt component of p-p (7Be)

with 1-3% (2-5%) accuracy

Nuclear Physics


The importance of low energy solar neutrino experiments

CC p-p Experiments: LENS

Spokesman: Raju Raghavan

40 tons In target in 400 tons scintillator

Modular design with In cells surrounded

by non-In cells (2000 tons scintillator)

Fundamental problem: 115In beta decay

Nuclear Physics


The importance of low energy solar neutrino experiments

CC p-p Experiments: LENS

Nuclear Physics


The importance of low energy solar neutrino experiments

LENS Count Rates

  • Design Parameters (assumed)

  • 40 tons In

    •  480 tons InLS, 4 kton non-InLS

  • 4 years of running (5 calendar years)

  • Detection efficiency ~ 22% for p-p, 57% for 7Be, CNO

  • 300 MeV/pe scintillator, 3 m attenuation length

  • No backgrounds

  • Calibrated by 8 MCi 51Cr source

SourceStatistical Accuracy

p-p2.3%

7Be 2.8%

CNO 5.8%

pep 11.8%

Issue: estimated cost ~ $140M

Nuclear Physics


The importance of low energy solar neutrino experiments

CC p-p Experiments: MOON

Nuclear Physics


The importance of low energy solar neutrino experiments

CC p-p Experiments: MOON

Issue: Double beta decay background!

Nuclear Physics


The importance of low energy solar neutrino experiments

ES p-p Experiments: HERON

Spokesman: Bob Lanou

~ 5,000 events/yr (10 ton fid. Vol.) BP00 SSM

Nuclear Physics


The importance of low energy solar neutrino experiments

Low Energy Solar Neutrino Fluxes

Bahcall, Gonzalez-Garcia, Pena-Garay, hep-ph/0204194

Ga  SNO  KamLAND  BOREXINO  BP00

Ga Ga CNO SNO KamLAND BOREXINO

Exp’t X-Sect. SSM CC Exp’t Exp’t Sterile

      

+0.05 +0.01 +0.00

fpp = 1.05 (1 ± 0.11 ± 0.007 ± 0.05 ± 0.04 )

- 0.08 - 0.02 - 0.02

= 1.05 (1 ± 0.15)

Dedicated pp Experiments

required to make Improvements.

Flux Predictions for a pp

Elastic Scattering Experiment

0.697 ± 0.023 (100 keV)

0.693 ± 0.024 ( 50 keV)

Nuclear Physics


The importance of low energy solar neutrino experiments

Low Energy Solar Neutrino Fluxes

SAGE Results: 69.6 +4.4/-4.3 (stat) +3.7/-3.2 (syst) SNU

GALLEX + GNO: 70.8  4.5 (stat)  3.8 (syst) SNU

Progress in determining the flux of

low-energy solar ne can only be achieved

in the next decade by improved Ga measurements

SAGE: 1990-2003

The Gallium experiments should continue to operate

until they are systematics limited

Nuclear Physics


The importance of low energy solar neutrino experiments

The Russian-American Gallium Experiment

It has been my experience that SAGE has proved to be a perfect

example of the value of international scientific collaborations

The SAGE collaboration has provided the means

for achieving a significant scientific result

It has been my privilege and honor to play a role in SAGE

I am extremely grateful to the many people

who have made SAGE a success -

Without all of their support the success and recognition

that we have received in the world scientific community

would not have been possible.

Nuclear Physics


  • Login