# Presentation: 103218

## Constraining Neutrino Properties with the Cosmic Microwave Background

- Kathryn Zurek
- University of Wisconsin, Madison

- A. Friedland, K. Zurek, S. Bashinsky, in progress

## Outline

- Basic CMB physics
- Neutrinos and the CMB
- Majoron models of neutrino mass
- Neutrino dark energy
- Little constraint from WMAP; significant constraint from PLANCK
- Implication for models of neutrino mass; targets for model builders
- What other models might be constrained?

- Kathryn Zurek, Fermilab seminar

## “The era of precision cosmology”

- z ~ 1000 (T ~ 0.1 – 1 eV)
- + galaxy surveys (SDSS and 2dF) (z ~ few, T ~ 10-4 eV)
- + supernova data (z ~ few, T ~ 10-4 eV)
- + BBN data (z ~ 109, T ~ 1 MeV)

- Kathryn Zurek, Fermilab seminar

## Implication for particle physics

- Baryon to photon ratio at BBN and CMB epochs agree  constraints on
- late entropy release
- extra relativistic degrees of freedom
-  early matter domination
- Physical matter density measured through CMB and low-redshift galaxy surveys agree  stringent constraints on EOS of DM (density dilutes as 1/R3)
- Microwave background is a perfect blackbody  very stringent constraints on dark matter annihilation/interaction with CMB photons
- All potential model killers

- Kathryn Zurek, Fermilab seminar

## Implication for particle physics

- Interesting information on neutrinos from cosmology—sometimes more rigorous limits than laboratory
- Strongest constraint on neutrino mass from galaxy surveys m < 0.2 (Seljak et al; Melchiorri et al 2006)
- BBN constrains N < 3.3 - 4.5
- Cyburt, Fields, Olive, Skillman and Barger, Kneller, Lee, Marfatia, Steigman
- Original constraints made it difficult to reconcile LSND result favoring extra sterile neutrino with BBN (requires complicated flavor models with multiple sterile neutrinos)
- CMB + galaxy surveys + Lyman-alpha 2.7 < N < 7.4 (95% C.L.)

- Kathryn Zurek, Fermilab seminar

## Basic physics of acoustic peaks

- Baryon-photon fluid tightly coupled by scattering
- Balance of gas pressure and gravity sets up oscillations:
- Electron photon scattering before recombination will damp perturbations on scales smaller than mean free path

- Kathryn Zurek, Fermilab seminar

## What parameters does CMB measure well?

- Location of first peak
- Height of first peak
- Ratio of height of first peak to second peak

- Kathryn Zurek, Fermilab seminar

## Parameter Degeneracies

- Number of neutrinos 37
- Delay of Matter-Radiation EqualityBoost of Peaks due to ISW effect
- Remove Boost by rescaling h to refix zeq
- Small suppression
- Not a background effect!  Due to removal of neutrino anisotropic stress

- Kathryn Zurek, Fermilab seminar

## Parameter degeneracies

- Cat and mouse game of breaking degeneracies
- Break degeracies through data sets which measure orthogonal combinations of parameters
- BBN: YHe
- Galaxy surveys: H0/Heq
- Supernova: , wde
- Large errors often imply unbroken degeneracies
- Current constraints (WMAP3 + SDSS + 2dF + Lya):
- 2.7<N<7.2 (McDonald, Slosar, Seljak 2006)
- Data set dependent; pull in the data between 2dF and SDSS (4.6<N<10.1 vs. 0.9<N<6.8)

- Kathryn Zurek, Fermilab seminar

## BBN

- Constraints on Ntot<4.5
- This parameter may *evolve*
- Recouple at lower temperatures
- BBN can accommodate 1 extra neutrino state in thermal equilibrium, and possibly two extra scalars (Ntot= 4/7)
- Can CMB constraints be more restrictive?
- Constraints will apply to *any* thermalized species!

- 

- 

- Kathryn Zurek, Fermilab seminar

## Neutrino non-free-streaming

- Standard Model neutrinos decouple at BBN
- New Interactions neutrino free-streaming
- Not a background effect!  Due solely to different evolution of gravitational potentials

- Kathryn Zurek, Fermilab seminar

## Compensation also very efficient

- Current constraints?:  3 interacting neutrinos ruled out at   6 (Hannestad), 2.4 (Trotta and Melchiorri), 3.9 (Cirelli and Strumia)

- Kathryn Zurek, Fermilab seminar

## Particle Physics Motivations

- Total number of neutrinos:
- Potentially tighter constraint than BBN on any light fields/moduli
- Neutrino Interactions
- Neutrino mass unaccounted for in standard model
- What generates it?
- Models of neutrino mass generation often gives rise to new neutrino interactions

- Kathryn Zurek, Fermilab seminar

## Models of Neutrino Mass

- Higher dimension operator to generate neutrino mass
- Generate higher dimension operator with sterile neutrino = see-saw mechanism
- Add sterile neutrino to SM to generate neutrino mass

- Kathryn Zurek, Fermilab seminar

## Models of Neutrino Mass

- Right handed neutrino mass generated by additional scalar

- Kathryn Zurek, Fermilab seminar

## Models of Neutrino Mass

- Effective Interaction
- Goldstone and light scalar interactions:

- Kathryn Zurek, Fermilab seminar

## Neutrino Mass Models and the Majoron

- A venerable history
- Gelmini and Roncadelli, Georgi et al. (1981) HiggsTriplet model. Ruled out by LEP.
- Need singlet state.  Take see-saw (Yanagida, Gell-Mann 1979), promote to field which breaks lepton number.
- Chikashige, Mohapatra, Peccei (1980-81)
- Supersymmetric versions: Aulukh and Mohapatra (1983), Ross and Valle (1985)
- Modern incarnations
- Late time neutrino masses (Chacko, Hall, Okui, Oliver)
- Neutrinoless universe (Beacom, Bell, Dodelson)
- MaVaNs (Fardon, Nelson, Weiner)
- Other Neutrino Dark Energy models
- Hill, Mocioiu, Paschos, Sarkar
- Hall, Murayama, Papucci, Perez

- Kathryn Zurek, Fermilab seminar

## What scale physics can we probe?

- Bell, Sigurdson, Pierpaoli

- Kathryn Zurek, Fermilab seminar

## CMB very sensitive to g through neutrino non-free-streaming

- Possible to probe TeV scale neutrino mass generation!

- Kathryn Zurek, Fermilab seminar

## Neutrino dark energy

- Unique feature: low energy scale for entire sector
- Don’t generate neutrino mass at high scale (e.g. GUT scale) as in traditional see-saw
- Place cutoff for entire theory at eV scale (not weak SUSY breaking scale!)
- Generates small scalar mass (though not nearly as small as quintessence)

- Fardon, Nelson, Weiner

- Kathryn Zurek, Fermilab seminar

## Neutrino dark energy

- Expanding universe

- 

- 

- g

- Evolving coupling!

- Kathryn Zurek, Fermilab seminar

## Contact with the data: current and future constraints

- Unclear in the literature what the current constraints are
- Future sensitivity (Planck) either unclear or unanalyzed
- TT channel only, 1 errors on N = 1.5 (Bashinsky and Seljak) or 0.5 (Bowen, Raffelt et al)?
- No analysis conducted on sensitivity to neutrino interactions
- Will the noise be taken out of the sensitivity in future measurements?

- 3 interacting neutrinos ruled out at   6 (Hannestad), 2.4 (Trotta and Melchiorri), 3.9 (Cirelli and Strumia)

- Kathryn Zurek, Fermilab seminar

## What is the source of the sensitivity?

- Also unclear from the literature
- Phase shift = change in location of peaks due to change in sound speed?
- Or amplitude variation = due to suppression of growth of fluctuations?
- How does the compensation work?

- Bashinsky and Seljak

- Kathryn Zurek, Fermilab seminar

## The toolkit

- Walk the parameter space to determine best fit to spectrum
- Monte Carlo Markov Chain: CAMB and CosmoMC
- Which parameters to vary?
- Use Fisher analysis to determine preliminary sensitivity

- Kathryn Zurek, Fermilab seminar

## The toolkit

- Standard error:
- Evaluate spectrum at O(20) points, instead of O(105) points (as in MCMC)
- But must assume errors are Gaussian

- Kathryn Zurek, Fermilab seminar

## Current Data: it depends on which set you believe

- Kathryn Zurek, Fermilab seminar

## Current Data: it depends on which set you believe

- Kathryn Zurek, Fermilab seminar

## Current Data: it depends on which set you believe

- Kathryn Zurek, Fermilab seminar

## Future data: Planck trumps all

- Kathryn Zurek, Fermilab seminar

## Power of WMAP3 vs. Planck

- WMAP3 only

- Planck only

- Kathryn Zurek, Fermilab seminar

## Slide 31

- Kathryn Zurek, Fermilab seminar

## Compensation mechanism and nature of the sensitivity

- Uncompensated differences

- After compensation

- Kathryn Zurek, Fermilab seminar

## Compensation mechanism and nature of the sensitivity

- Largest effect comes from small l where phase shift is unimportant.

- Kathryn Zurek, Fermilab seminar

## Implications for neutrino models

- Neutrino-neutrino scattering
- Decay-Inverse decay
- 

- Kathryn Zurek, Fermilab seminar

## Implication for neutrino models

- Neutrino dark energy
- “Natural” scalar masses in MaVaN models: 10-3-10-6 eV
- Generic see-saw models

- Kathryn Zurek, Fermilab seminar

## Conclusions

- There are many types of neutrino models which generate neutrino-scalar interactions
- Majoran models
- Lighter see-saw (break symmetry associated with additional scalar, f ~ 1 MeV-1 TeV)
- Neutrino dark energy
- Even for very small neutrino scalar couplings (g<10-7-10-13), interaction g may lead to neutrino non free-streaming or extra relativistic degrees of freedom around CMB temperatures
- While current data cannot tell us whether neutrinos were free-streaming at recombination, or whether there are extra neutrinos in thermal equilibrium, PLANCK alone will be able to constrain neutrino free-streaming and an extra-relativistic degree at high significance.
- Will be able to probe TeV scale neutrino mass generation and models of neutrino dark energy

- Kathryn Zurek, Fermilab seminar