# Presentation: 109297

## Experimental Prospects for Direct Measurements of Neutrino Mass(Tritium Experiments)

**  ****Directness?**
**  ****The Various Techniques: for completeness**
**  ****Astrophysics/Cosmology (very short)**
**  ****Nuclear and Particle Physics: heart of the talk**
**	****beta decay**
**	**

**Experimental Prospects for Direct Measurements of Neutrino Mass****(Tritium Experiments)**

- Steve Elliott

***Nuclear Physics***

## Direct vs. IndirectAbsolute vs. RelativeKinematic vs. Interference

**No m******** experimental technique is direct in that it measures one of the *****m*****i****. All experiments measure parameters that depend on the mass eigenvalues.**
**Many laboratory experiments might indicate the “absolute scale of ******** mass”.**
**These are experiments that search for a kinematic effect due to mass. **
**These are not experiments that search for an interference effects. Oscillation experiments provide data on the “relative mass scale”.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Neutrino Mass: What do we want to know?

**Mass**

**Absolute**
**Mass**
**Scale**

**Relative**
**Mass**
**Scale**

**Dirac or Majorana**

******e**

******1**

******2**

******3**

**Mixing**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## A List of Upcoming Techniques

**Supernovas - relatively poor sensitivity**
**Cosmology - hope of reaching below 100 meV**
**Nuclear/Particle Physics**
**	******** ****decay - relatively poor sensitivity**
**	******** ****decay - relatively poor sensitivity**
**	******** ****decay - hope to reach below 500 meV**
**	******** ****decay - hope to reach below 50 meV**
**	****oscillations - great sensitivity to mass differences**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Matter Content of Universe

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Supernova Tests

**Spread of neutrino arrival times can give indication of mass.**
**SN1987a: about 20 eV limit but conclusions varied.**
**SN dynamics makes for model dependencies.**
**Future sensitivity might be a few eV.**

**But Earth effects might be exploited for ********13**** and sgn(********m****2****) measurments**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Supernova  Experiments

| Detector | Type | Mass (kton) | Location | # events at 10 kpc | status |
| --- | --- | --- | --- | --- | --- |
| Super-K | H2O Cerenkov | 32 | Japan | 7000 | Running |
| SNO | Heavy Water (salt) | 1.4 H2O / 1 D2O | Canada | 350, 450 | Running |
| LVD | Scintillator | 1 | Italy | 200 | Running |
| KamLAND | Scintillator | 1 | Japan | 300 | Running |
| Borexino | Scintillator | 0.3 | Italy | 100 | Soon? |
| Baksan | Scintillator | 0.33 | Russia | 50 | Running |
| MINIBooNE | Scintillator | 0.7 | USA | 200 | Running |
| AMANDA | Ice | Meff ~ 0.4/PMT | South Pole | N/A | Running |
| Icarus | Liquid Ar | 2.4 | Italy | 250 | Soon |
| OMNIS | Pb, Fe | 4, 1 | USA | 2000 | Proposed |
| LANNDD | Liquid Ar | 70 | USA | 6000 | Proposed |
| UNO | H2O Cerenkov | 600 | USA | >100,000 | Proposed |
| Hyper-K | H2O Cerenkov | 1000 | Japan | >100,000 | Proposed |
| LENA | Scintillator | 30 | Europe | 15,000 | Proposed |

**Table aby Scholberg (NESS)**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## CosmologyMeasure h2

**WMAP measured cosmological parameters very precisely. This allowed precise estimates of ************h****2**** from LSS measurements.**
**WMAP results indicate *********m*****i**** < about 1 eV. A very competitive result. (one interpretation claims *********m*****i**** = 0.64 eV!) **
**But, correlations between parameters result in assumption dependent conclusions. **
**Want laboratory experiments.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Cosmology - Future Measurements

**MAP/PLANCK CMB measurements with high precision galaxy surveys (Sloan Digital Sky Survey): *********m*****i**** < ~300 meV**
**If weak lensing by LSS is also considered:**
*******m*****i**** < ~40 meV**
**Even with the correlations, cosmology will play an important role in the interpretation of neutrino mass.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Z-burst and high-energy 

**Requires, as yet unknown (and unneeded?) flux of UHE ******** with energy > Greisen-Zatsepin-Kuzmin (GZK) energy (5x10****19**** eV).**
**Although could explain existence of cosmic rays with E>E****GZK****, it doesn’t explain source of proposed UHE ********.**
**UHE ******** + cosmic relic ******** --> Z --> hadrons, ********s**
***m*****i**** near 500 meV could produce p or ******** just above GZK cutoff. Model can be “tweaked” to get lower masses.**
**Detect p or ******** : their multiplicity and energies relate to E****R**** and hence *****m*****i****.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Nuclear and Particle Physics Techniques

****** ****decay: decays into 5 or 6 ******** most sensitive because of restricted phase space for ********.**

**Eur. Phys. J. C2 (1998) 3**

**m****h**** is invariant mass of n ********.**
**E* is total ******** energy in ******** rest frame.**
**Obtain data on degenerate scale *****m*****1****.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Nuclear and Particle Physics Techniques

****** ****decay: ******** --> ******

**PR D53 (1996) 6065**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## The  Spectrum (bare nucleus)

**Fund. Constants**

**Energy-independent Matrix Element**

**Fermi Function**

**Electron momentum,**
**Energy, mass**

****** ****= E****0**** - E**

**Step Function**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

##  Spectrum (atom or molecule)plus neutrinos mix

**Many possible final states.**

**W****j**** - probability for transition to state j**

******j**** for state j**

***m*****i**** - ******** mass**
**eigenstate**

**U****ei**** - mixing**
**matrix elements**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

##  Spectrum(atom or molecule)

**When convolved with resolution function with width > *****m*****i****, we can analyze the spectrum with one mass parameter: <*****m*********>.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## The Neutrino Mass from  decay

**The shape of the ******** energy spectrum **
**near the endpoint depends on m********.**

**NP B (Proc. Suppl.) 91 (2001), 273**

**KATRIN LOI**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## 187Re  Decay Experiments

**Low Q-value: 2.6 eV**
**Long half-life = low specific activity**
**Bolometric techniques = measure whole spectrum**
**But also entire energy deposit!!!**
**Measure 10****-10**** of decays near endpoint, but bolometer response time is 100s ********s.**
**Future sensitivity should be about 10 eV.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Milano Re Experiment

**AgReO****4**
**Hope for a sensitivity of 4 eV**

**NIM A444 (2000) 77**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Genoa Re Experiment

**Genoa: Metallic Re, m********< 26 eV  ****NP B (proc. Suppl.) 91 (2001) 293**

**PR C63 014302**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Why Tritium?

**Re bolometers (source = detector) collect whole spectrum at once: therefore need low rate to prevent pile-up.**
**Very low Q-value (2.5 keV)**

**With source ≠ detector, one can just analyze end of spectrum: much higher activities.**
**Low Q-value (18 keV)**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Mainz Experiment Setup

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Mainz Results

- E ~2-6 eV at 20 keV
- Large acceptance
- 	10-40% of 4

- _Improvements 94-98_
- Lower temp source
- 	no dewetting
- T2 evaporating into
- spectrometer stopped
- by tilted solenoids.

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Fit Function

**Fit Parameters: Free Amplitude, Endpoint energy, neutrino mass squared, and background**
**Response function depends on: Potential distribution within source, backscattering from source substrate, spectrometer transmission, and energy dependence of detection efficiency.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Systematic Uncertainties

**Inelastic scattering in tritium film**
**Neighbor molecule excitation**
**Final states in THe****+**** molecule**
**Charging of source film**

- Statistical

- Systematic

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## The Troisk Experiment

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Troisk Results

**PL B 460, 227 (1999)**

**Solid line is spectrum with step funcion.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Troisk Anomaly

**A “peak” shifting periodically in time would match the data.**
**In a integrating spectrum, a peak would appear as a step.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Identifying the Systematics

**Mainz: tritium as thin film on flat surface. Temperature activated roughening led to microcrystals in turn leading to large inelastic scattering.**
**Troisk: Gaseous tritium. Large angle scattering of electrons trapped in source.**
**Addressing these issues removed the “negative mass squared” in those experiments.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Primary Systematic Uncertainties

**Resolution error leads to m******** error**

**KATRIN LOI**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Tritium  decay Experiments

**KATRIN**
**Very big spectrometer using gaseous and thin sources. A big step forward.**

**Univ. of Texas-Austin**
**t****2**** source in magnetic free environment.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## The MAC-E Filter

**Magnetic Adiabatic Collimation followed by an Electrostatic Filter**
**High luminosity**
**Low background**
**Good energy resolution**
**Integrating **
**     ****high-pass filter**

**KATRIN LOI**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## KATRIN

**1-eV resolution (x4 better)**
**Electron transport system guides ******** to pre-spectrometer while preventing tritium flow to spectrometers.**
**Pre-spectrometer filters out all ******** except those near endpoint. Keeps residual ionization minimized hence reducing background.**
**Large analyzing plane increases signal rate**
**Si drift detectors. 600 eV resolution for 18.6 keV ********. Good electron sensitivity but low efficiency for ********.**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## KATRIN (LOI version)

- KATRIN will be sensitive to about 200 meV. Thus if the *m*i follow a degenerate pattern and *m*1 is within the sensitivity, the experiment may see <m> = *m*1.

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## Summary of Mass Measurements(with a guess at the future)

**Plot a la PL B532, 15 (2002)**

_**Absolute scale measures**_
******: 350 meV**
******: 50 meV**
**Cosmology: <100 meV**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

**Notes:**
Solar mixing angle is 30 degress for 2bdk formula.

## A summary of the questions

**Are neutrinos Majorana or Dirac?**
**What is the absolute mass scale?**
**How small is ********13****?**
**How maximal is ********23****?**
**Is there CP violation in the neutrino sector?**
**Is the mass hierarchy inverted or normal?**
**Is the LSND evidence for oscillation true? Are there sterile neutrinos?**

- Steve Elliott, Tritium Beta Decay, NPSS 2005

## References

**Katrin LOI**
**Lobashev *****et al*****. PL B460 (1999) 227**
**Weinheimer *****et al*****. PL B460 (1999) 219**
**Bilenky Review**
**	****hep-ph/0211462 v3**

- Steve Elliott, Tritium Beta Decay, NPSS 2005