Thursday, June 9, 2022

New Daya Bay Neutrino Oscillation Parameters With Record Precision

New Daya Bay Results

Physics conferences are providing new measurements for neutrino oscillation parameters (in the case of the Daya Bay measurements the precision of the measurement sets a new record).

Via Physics Forums (hurray for Twitter which announced data not found in the press release from Daya Bay or at arXiv).

Prior to these results the global average Particle Data Group (PDG) results were as follows:

Translated into raw values of the parameters themselves, the best fit Daya Bay theta13 value is 8.49º compared to a PDG value of 8.53º. These results are consistent at the one sigma level. (The PDG value of theta12 is 33.65º.)

The square root of the normal hierarchy Δm232 is 49.5 meV (while it is 49.1 meV for the NOvA measurement below). The PDG value is 49.53 meV. The two measurements and the world average are all consistent with each other within their uncertainties. (The PDG delta m12 value is 8.68 meV.)

The Daya Bay presentation also included the following summary of results from other experiments:

New NOvA Collaboration Results

There are also new results from the NOvA collaboration:

We present the most recent 3-flavor neutrino oscillation results from the NOvA long-baseline experiment, using a joint fit of νμνμν¯μν¯μνμνe, and ν¯μν¯e channels, and an accumulated exposure of 13.6×1020 protons-on-target of neutrino beam and 12.5×1020 protons-on-target of antineutrino beam. 

The best-fit values for the atmospheric parameters are 

Δm232=(2.41±0.07)×103 eV2sin2θ23=0.57+0.030.04 and δCP=(0.82+0.270.87)π

The data disfavor combinations of oscillation parameters that lead to large asymmetries between the rates of νe vs ν¯appearance.

Erika Catano-Mur (for the NOvA collaboration), "Recent results from NOvA" arXiv:2206.03542 (June 7, 2022) (Contribution to the 2022 EW session of the 56th Rencontres de Moriond).

The NOvA theta23 value is 49.02º v. the PDG value of 47.64º or 42.36º with the second quadrant (i.e. more than 45º slightly favored). The results are consistent with each other at one sigma.

The NOvA value for the CP violating phase of 147.6º is consistent at one sigma with zero but favors something close to the maximal value of one π, as have prior measurements from other sources. The PDG value is 244.8º. the results are consistent with each other within their uncertainties.

Background Reference Re CKM Matrix

The 2008 values for the parallel standard parameters of the CKM matrix for quarks were:

θ12 = 13.04±0.05°, 
θ13 = 0.201±0.011°, 
θ23 = 2.38±0.06°
δ13 = 1.20±0.08 radians = 68.8±4.5°.

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