LBNL-2016: Neutrino and Light Relativistic Species

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Break-out Sessions

First 15 minutes : Status of Neutrino Chapter (Dan Green)

Second 45 minutes : Important questions to address (Marilena Loverde)

Some topics for discussion

  • Obstacles to measuring neutrino mass (e.g. optical depth and lmin)
  • Comparison with lab based neutrino mass experiments
  • Status of other cosmological probes like clusters and cross-correlations
  • Other important theory targets (beyond sterile neutrinos and axions)

Status of the Science Book

Big Picture

The primary neutrino-science targets described in the science book are Mν > 58 meV and ΔNeff > 0.027.




  1. Intro
  2. Neutrino Mass
    1. Intro
    2. CMB Lensing
    3. Other Cosmological Probes
    4. Forecasts
    5. Relation to Lab Experiments
  3. Neff
    1. Theory Review
    2. Natural Target
    3. Observational Signatures
    4. Forecasts
  4. Sterile Neutrinos and Axions
    1. Sterile Neutrinos
    2. Axions
  5. Complementarity of CMB and BBN
    1. Theory Review (BBN)
    2. BSM physics and BBN
    3. Relation to CMB

Sections in need of work

  • Forecasting
  • Discussion of lensing signature, systematics
  • Other Cosmological Probes both with S4 (SZ clusters) and other surveys (galaxy surveys, weak lensing)
  • Comparison with Lab (both for neutrino mass and BSM physics)
  • Other theory targets

Open Questions


Discussion tomorrow - please come!

  • Mν forecast is output of lensing forecast. Do we leave it to the lensing group?
  • What needs to be included in the Mν and Neff forecast? (Give us your answer tomorrow)

Neutrino Mass Intro

  • What do we learn from measuring Mν? What is the motivation?
  • What do we learn from combining with lab measurements?


figure from Dodelson and Lykken arXiv:1403.5173

  • Neutrino-less double beta decay and cosmology are complimentary (especially for inverted hierarchy)

Optical Depth and lmin


figure from Allison et al. arXiv:1509.07471

  • We don't need S4 level of sensitivity to reach goals.
  • Transition around lmin 15-20. Is that doable?


BAO plays an important role in breaking degeneracy with Ωm


figure from Pan and Knox

  • Should we be including more parameters beyond LCDM in our forecasts? If so, what should we marginalize over?


figure from Allison et al. arXiv:1509.07471

SZ Clusters and Other data sets

We need help on SZ clusters and cross-coloration and their impact on neutrino mass.


figure from Mantz

  • How can we combine data with other surveys to improve our constraint on Mν and Neff?
  • We need to elaborate on the relation to LSS surveys

Theory Targets

Current state : short discussion of sterile neutrinos. Axions also look quite promising!


figure from Baumann, Green & Wallisch (to appear)

Is there more to say about sterile neutrinos. Are there other compelling targets? E.g. energy injection?

  • More work needed on the impact on sterile neutrinos. Explain connection with lab experiments (e.g. impact of sterile neutrino hints for CMB S4).
  • What is the interplay with BBN, Mν, etc.? Need a way to parameterize the impact of all these measurements
  • CMB measures Yp. Add impact of this measurement for BSM physics and BBN physics.
  • What can we learn about the neutrino distribution?


figure from Fuller and Evans (Grohs et al. arXiv:1512.02205)