Difference between revisions of "UMICH-2015: Neutrino and Light Relativisic Species break-out session 1"

Revision as of 15:28, 17 September 2015

Clear science target - A massless field in thermal equilibrium with the Standard model leads to ΔN_eff > 0.027

For thermal decoupling above 100 GeV: Real scalar - ΔN_eff = 0.027; Weyl fermion - ΔN_eff = 0.047 (Dirac - 0.094); Vector field - ΔN_eff = 0.054

With 10⁶ detectors and f_sky = 0.75, forecasts of σ_Neff =0.013: (see e.g. arXiv:1402.4108).

Model independent theory motivation - Is this realistic experimentally?

What are the trade-offs for other science goals to achieve this sensitivity

What is missing from the forecast that could significantly reduce the sensitivity?

More general science targets -- axion-like particles, late decays of massive fields (before, during or after BBN), decaying Dark matter

How well can be break degeneracies?

E.g. Want to separate N_eff^CMB from Y_p

Forecasts with both varying give σ_Neff = 0.048 and σ_Yp = 0.0027 (see arXiv:1508.06342)

In principle allows us to distinguish effects at recombination from changes to BBN

What role does CMB lensing play?

For N_eff, delensing E-modes improves constraints significantly (sharpens peaks - improves phase shift measurement)

Can it help break degeneracies in other models (e.g. decaying dark matter) ?

Is it a good direct probe of BSM physics (as in the case of neutrino masses)

Planck 2015 versus forecasts with 2 different marginalizations (see arXiv:1508.06342)

@@ Line 7: / Line 7: @@
 ;For thermal decoupling above 100 GeV :
-: a real scalar produces &Delta;N<sub>eff</sub> = 0.027
+: Real scalar - &Delta;N<sub>eff</sub> = 0.027
-: a Weyl fermion produces &Delta;N<sub>eff</sub> = 0.047 (Dirac : 0.094)
+: Weyl fermion - &Delta;N<sub>eff</sub> = 0.047 (Dirac - 0.094)
-: a vector field produces &Delta;N<sub>eff</sub> = 0.054
+: Vector field - &Delta;N<sub>eff</sub> = 0.054
 ;With 10<sup>6</sup> detectors and f<sub>sky</sub> = 0.75, forecasts of &sigma;<sub>Neff</sub> =0.013