# Presentation: 448923

## All Things Neutrinos

- H. Ray
- Los Alamos National Laboratory
- MiniBooNE

## Outline

- Neutrinos & The Standard Model of Physics
- Oscillations
- Sources of Neutrinos
- Detecting Neutrinos
- Interactions with matter
- Detection techniques
- Examples of detectors
- Oscillation Results
- Sampling of Neutrino Theories

## Cool Neutrino Facts

- Human body = 20 mg of Potassium 40.  Humans emit 340 million neutrinos per day!
- 100,000 billion pass through your body each second from the sun
**Your body will stop ~1 neutrino which passes through it in a lifetime!**

## Why Neutrinos?

- 2 body alpha decay, E of decay products always the same
- 1913 - 1930 : beta decay = continuous spectrum of E
- E not conserved?
- P not conserved?
- “I have done something very bad today by proposing a particle that cannot be detected; it is something no theorist should ever do.” (Pauli, 1930)

## Two Body Decay Kinematics

## Standard Model of Physics

**+2/3**
** ****-1/3**

## Standard Model of Physics

** ****0**
**-1**

## Standard Model of Physics

**  ****0**
** ********1**

## Standard Model of Physics

## Standard Model of Physics

## Standard Model of Physics

## Standard Model of Physics

- Also have 12 anti-particles (same mass & lifetime, opposite charge)
- Gauge particles mediate or transmit forces between particles
- Forces that create particles also dictate which interactions particles can participate in
- E-M : particles with electric charge
- Quarks, leptons
- Strong : binds quarks together
- Quarks

## Standard Model of Physics

**Weak : ****force of transmutation!**
**changes flavor of quarks, leptons **_***within a family***_
**Only force that acts on neutrinos**
**Neutral current = no exchange of electric charge (Z)**
**Charged current = exchange electric charge (W****+****, W****-****)**

## Standard Model of Physics

**W-**

**W-**

**W**+

**W+**

**Notes:**
Can’t switch between families

## Ex : Beta Decay

**n**

**p**

**W****-**

******e**

**e****-**

**du****d = -1/3**

**du****u = +2/3**

**W****- ****= -1**

**time**

## Neutrinos in the Standard Model

- Neutrinos are massless
- Neutrinos only interact via the Weak force
- Neutrinos are left-handed
- anti-neutrinos are right-handed
- Neutrinos are electrically neutral
- Neutrinos have three flavors
- Electron, muon, tau

## Oscillation Physics

## Quark Mixing

- Problem! If Weak force only acts inside of a family - how do you explain lambda decay?

******-**

**u**

**u**

**u**

**d**

**d**

**s**

****

**p**

**W****-**

**u**

**d**

**Notes:**
We know it’s the weak force and not strong b/c of lifetime of lambda.  If strong see super quick decay

## Quark Mixing

- Solution : quark generations are rotated for the purposes of weak interactions
- Instead of the Weak force coupling to
- It couples to

**u**

**d**

**u**

**d’**

## Quark Mixing

- Where d’ is a linear combination of the d, s, b quarks
- mixing that results from mis-alignment of weak and mass states is a natural outcome of the symmetry-breaking mechanism by which particles acquire mass

**s’**

**b’**

**d’**

**s**

**b**

**d**

**V****ud**

**V****us**

**V****ub**

**V****cd**

**V****td**

**=**

**Weak state**

**Mass state**

**Notes:**
Rubik cube : strong sees one side, week sees other (mixed side)

## Quark Mixing

- States which participate in Strong interactions are mass states
- States which participate in Weak interactions are mixtures of mass states

**W-**

**W**+

**’**

**’**

**’**

## Lepton Mixing

- Why doesn’t same thing happen to leptons?
-  SM = mass and weak states are identical because the neutrino has no mass!
- If neutrinos are massive have analogous situation for neutrino-lepton pairs

## Neutrino Oscillations

********

******e**

**=**

**Weak state**

**Mass state**

******1**

******2**

**cos ******

**cos ******

**-sin ******

**sin ******

## Neutrino Oscillations

********

******e**

**=**

**Weak state**

**Mass state**

******1**

******2**

**cos ******

**cos ******

**-sin ******

**sin ******

**|************(0)> = -sin ******** |********1****> + cos**** ******** |********2****> **

## Neutrino Oscillations

********

******e**

**=**

**Weak state**

**Mass state**

******1**

******2**

**cos ******

**cos ******

**-sin ******

**sin ******

**|************(t)> = -sin ******** |********1****> + cos**** ******** |********2****> **

**e-****iE1t**

**e****-iE2t**

## Neutrino Oscillations

**P****osc**** = |<********e ****| ************(t)>|****2**

**P****osc**** =sin****2****2******** sin****2**** 1.27 ********m****2 ****L**
**	****	****	****	****	****	****E**

## Neutrino Oscillations

**P****osc**** =****sin****2****2******** sin****2**** 1.27 ********m****2**** ****L**
**	****	****	****	****	****	****E**

**Distance from point of creation of neutrino beam to detection point **

****** ****Is the mixing angle**

******m****2  ****is the mass squared difference between the two neutrino states**

**E is the energy of the neutrino beam**

## Neutrino Oscillations

**Probability**

**sin****2****2******

**Distance from neutrino source (L)**

## Sources of Neutrinos

## Neutrino Sources

**Solar : ~ 0.1 - 15 MeV (10****6**** eV)**
- from fusion inside of stars
- 85% from p+p -> 2H + e+ + e
**Man-Made : ~few MeV**
- Nuclear reactors - byproduct
**Man-Made : ~ 0.5 MeV - 1 GeV (10****9**** eV)**
- Accelerators - DAR, DIF
**Atmospheric : ~1 - 10 GeV**
- cosmic  rays = proton from outer space + atm = showers, creates atmospheric neutrinos

**Notes:**
Say atm = same as accelerator; slam something into a target, wait for decay.  
Advantage of accel = beam off some part of the time

## Solar Neutrinos

- Theoretical uncertainties

**ppI**

**ppII**

**ppIII**

## Nuclear Reactor Neutrinos

- Reactors = only source of a pure anti-neutrino beam, pure electron-flavor beam!
- Anti-neutrinos are emitted by the radioactive fissile products when they disintegrate via beta decay
- ~few MeV Energy

- Rb-92

- e

- e-

## Accelerator-Based Neutrinos

- Beam of protons + a target material = mesons (, K)
- Mesons decay into the neutrino beam seen by a detector
- K+ / +  + + 
- +  e+ +  +  e
- K0L   ++ - + 
- Create neutrinos via meson Decay at Rest, Decay in Flight

**Notes:**
We use Be to limit reinteractions
Be, Sapphire, Carbon commonly used

## Decay At Rest

**Target Area**

******-**** absorbed by target**

******+****DAR**

**Mono-Energetic!**
**********= 30 MeV**

**E range up to 52.6 MeV**

- Hg+ target, SNS (Spallation Neutron Source, Oak Ridge)

## Decay At Rest

- Advantage = Know timing of beam, lifetime of particles, use to greatly suppress cosmic ray background
- Advantage = extremely well defined flux
- Disadvantage = Low E limits choices of neutrino interaction signal
- Disadvantage = Beam is isotropic - no directionality
- Hard to make an intense isotropic beam

## Decay In Flight

- Advantage : more intense beam because mesons are focused (not isotropic)
- Advantage : can select neutrino, anti-nu beam
- Disadvantage : difficult to understand the flux (in content and in E)!

## Atmospheric Neutrinos

- High energy protons + nuclei collide in the upper atmosphere = high energy pions
- Pions  muons  + neutrinos
- Muons  neutrinos
- ( + ) : (e + e)          = 2 : 1

- 

- 

- e

## Detecting Neutrinos

- Interactions with Matter

## Detecting Neutrinos

- Neutrinos interact with material in the detector.  It’s the outcome of these interactions that we look for
**Neutrinos can interact with : **
- Electron in the atomic orbit
- The nucleus as a whole
- Free proton or nucleon bound in nucleus
- A quark

## Neutrino Interactions

- Elastic Scattering
- Quasi-Elastic Scattering
- Single Pion Production
- Deep Inelastic Scattering

**MeV**
**GeV**

## Elastic Scattering

- Target left intact
- Neutrinos can elastic scatter from any particle (electrons, protons)
- Neutrino imparts recoil energy to target = how we observe these interactions

**Z**

******e**

**e****-**

**e****-**

******e**

## Quasi-elastic Scattering

- Neutrino in, charged lepton out
- Target changes type
- Need to conserve electric charge at every vertex
- Need minimum neutrino E
- Need enough CM energy to make the two outgoing particles

**n**

**p**

**W****+**

******e**

**e****-**

**Notes:**
Say : inverse beta decay!

## Single Pion Production

- Resonant
- neutrino scattering from a nucleon
- Nucleon resonance is excited, decays back into it’s ground state nucleon
- Emits one or more mesons in the de-excitation process

**N**

**Z****0**

********

********

**N***

**N**

******0**

## Single Pion Production

- Coherent
- neutrino scatters from entire nucleus
- nucleus does not break up / no recoil nucleon
- Requires low momentum transfer (to keep nucleus intact)
- No transfer of charge, quantum numbers

**A**

**Z****0**

********

********

**A**

******0**

## Deep Inelastic Scattering

- Scattering with very large momentum transfers
- Incoming neutrino produces a W boson, turns into partner lepton
- W interacts with quark in nucleon and blows it to bits (ie inelastic)
- Quarks shower into a variety of hadrons, dissipating the E carried by the W boson  (ie deep)

**n**

**Hadron shower**

**W****+**

******e**

**e****-**

## How often do these interactions occur?

## Cross Sections

- Cross section = probability that an interaction will take place

- Volume of detector = V (m3)
- Density of nucleons = n (1/m3)

- Neutrino flux =  (1/m2s)

****

****

****

****

****

**Cross Section ********  (m****2****) = # neutrino interactions per second**
**	****	****	****                 ****Flux  * Density * Volume**

- # of targets

## Neutrino Cross Sections

## Detecting Neutrinos

- Detection Techniques

## Observing Neutrino Interactions

- Very small cross sections for interactions!
- Need large-scale detectors
- Radiochemical reactions
- e + 37Cl = 37Ar + e-
- Measure neutrino flux by counting number of produced Ar atoms
- No time, direction information
- Passage of charged particles through matter leaves a distinct mark
- Cerenkov effect / light
- Scintillation light
- Provides time, direction information

- Find
- s

- Find
- products
- of 
- ints

## Cerenkov Light

- Light detected by PMTs
- Use to measure particle direction and to reconstruct interaction vertex
- Prompt light signature

- Charged particles with a velocity greater than the speed of light * in the medium* produce an E-M shock wave
-  v > 1/n
- Similar to a sonic boom

**Notes:**
Say : detected by pmts.  Pmts are reverses lightbulbs.

## Cerenkov Light

## Scintillation Light

- Charged particles moving through a material deposit energy in the medium, which excites the surrounding molecules
- The de-excitation of molecules produces scintillation light
- Isotropic, delayed
- No information about track direction
- Can use PMT timing information to locate interaction point

## Detecting Neutrinos

- Examples of Detectors

## Neutrino Detectors : Solar (Atm, Accel)

- Scattered ele follow the direction of the incoming  (~15 deg. max deviation)
- Threshold E for interaction = 4 to 5 MeV

- [1] Detect Cerenkov light from  interacting with water in Kamiokande
- Electron neutrino scatters elastically from an atomic electron

## Neutrino Detectors : Solar

- [1] Detect Cerenkov light from  interacting with *heavy* water : SNO
- Deuterium nuclei in water = distinguish electron neutrinos from other types
- Neutrino interaction rates are higher in heavy water than ordinary water = uses less water, less collection time to have same statistics as Kamiokande
- NC : D +  = p + n + 
- CC :                                                                                           D + e = p + p + e

**Notes:**
Say : use heavy water b/c can’t interact w/ neutrons in normal water b/c too 
Tightly bound in oxygen.  Deuterium falls apart

## Neutrino Detectors : Solar

- [2] Detect transformation of atoms under neutrino interaction
- e + 37Cl = 37Ar + e- : Homestake
- Only sensitive to  from 7Be, 8B branches (>0.8 MeV)
- e + 71Ga = 71Ge + e- : Gallex
- Sensitive to  from                                                     initial proton fusion                                              reaction (>233 keV)

## Neutrino Detectors : Reactor

**Kamland** scintillator detector

**neutron thermalization**
**mean time = 200 **s

**two 0.511 MeV photons**

**one 2.2 MeV photon**

**happens so quickly you only see 1 light flash!**

## Neutrino Detectors : Accelerator

- Mainly a Cerenkov detector

## Oscillation Results

## Oscillation Results

******m****2 ****= m****a****2**** - m****b****2**

- If there are only 3 :
******m****ac****2**** = **
**	********m****ab****2**** + **
**	********m****bc****2**

**P****osc**** =****sin****2****2******** sin****2**** 1.27 ********m****2**** ****L**

**        ****E**

**Notes:**
Repeat pierres line about all hell will break loose
If lsnd is right we have jobs for many years

## Sampling Neutrino Theories

- AKA : explaining the three oscillation results

## Other Theories

- Sterile Neutrinos
- RH neutrinos that don’t interact (Weak == LH only)
- CPT Violation
- 3 neutrino model,  manti-2 > m2
- Run in neutrino, anti-neutrino mode, compare measured oscillation probability
- Mass Varying Neutrinos
- Mass of neutrinos depends on medium through which it travels
- Lorentz Violation
- Oscillations depend on direction of propagation
- Oscillations explained by small Lorentz violation
- Don’t need to introduce neutrino mass for oscillations!
- Look for sidereal variations in oscillation probability

## Things I Haven’t Covered

- How neutrinos can get mass
- Dirac vs Majorana type particles

## Finally : Open Questions

- What is the mass of each neutrino?
- Do neutrinos have a magnetic moment?
- Expect a non-zero moment if massive
- How do they get their mass?
- ie, are the neutrino and anti-neutrino the same or different?
- Is the LSND oscillation signal correct?

## Standard Model of Physics

**Up**
**3 MeV **
**1/312 H atom**

**Down**
**6 MeV **
**1/156 H atom**

**Electron**
**0.511 MeV**
**1/2000 H atom**

**Electron ******
**0 MeV**

**Charm**
**1500 MeV **
**1.5 H atom**

**Strange**
**170 MeV **
**1/5 H atom**

**Muon**
**105 MeV**
**1/9 H atom**

**Muon ******** **
**0 MeV**

**Top**
**175000 MeV**
**1 Au atom **

**Bottom**
**4500 MeV**
**1 He + 1 H atom**

**Tau**
**1782 MeV**
**2 H atoms**

**Tau ******
**0 MeV**