Addendum to: Improved global fit to non-standard neutrino interactions using COHERENT energy and timing data

In this addendum we re-assess the constraints on Non-Standard Interactions (NSI) from the combined analysis of data from oscillation experiments and from COHERENT after including the new data released since the publication of ref. [1].

In this addendum we re-assess the constraints on Non-Standard Interactions (NSI) from the combined analysis of data from oscillation experiments and from COHERENT after including the new data released since the publication of ref. [1], in particular the new results presented at the Neutrino2020 conference. New data considered includes the latest total energy spectrum and the day-night asymmetry of the SK4 2970-day sample presented at Neutrino2020 [2], and the latest results from long-baseline (LBL) experiments T2K [3,4] and NOvA [5,6]. In addition, we have updated the reactor experiments Double-Chooz [7,8] to 1276/587 days of far/near detector data and RENO [9,10] to 2908 days of exposure.
The main effect driven by the new results concerns the analysis of solar oscillation data. The quantification of the effects in the oscillation analysis has been presented in a separate Addendum to ref. [11]. Here we quantify the induced changes in the results of the combined analysis of oscillation data with COHERENT results, which were contained in section 4.2 of ref. [1]. In particular we present in figures 1 and 2 the new version of figures 8 and 9, and in table 1 the new version of table 2. In brief, in the left panel in figure 8 of ref. [1] we found that the introduction of NSI lead to a substantial improvement of the fit already for the LMA solution (solid lines) with respect to the oscillation data analysis, resulting in a sizable decrease of the minimum χ 2 LMA with respect to the standard oscillation scenario. This was driven by a well-known tension at the level of ∆χ 2 ∼ 7.4 between solar and KamLAND data in the determination of ∆m 2 21 . Correspondingly the inclusion of NSI improved the combined fit by about 2.2σ JHEP12(2020)071 over a broad range of values of η. As discussed in ref. [12], with the updated SK4 solar data the tension between the best fit ∆m 2 21 of KamLAND and that of the solar results has decreased to ∆χ 2 solar = 1.3. So now in the left panel in figure 1 we see that for the LMA solution the combined global fit with NSI leads to a decrease of about 2 units in χ 2 for most values of η and for most variants of the COH analysis. The only exception is the analysis of the combination with COHERENT t+E data using the data release assumptions, for which including NSI can improve the fit in LMA by ∆χ 2 ∼ 4 for most values of η.
Concerning the status of the LMA-D degeneracy, we find that when COHERENT total rate results are taken into account and we include the new oscillation data, LMA-D is allowed below 3σ with respect to LMA for a slightly wider range of values of η. This is a consequence of the increase of χ 2 LMA . Quantitatively, LMA-D is now allowed at 3σ for values of η in the following ranges: (0.1) Figure 2 contains the updated ∆χ 2 profiles for each of the six NSI coefficients after marginalization over the undisplayed oscillation parameters and the other five NSI coefficients not shown in a given panel, for three representative cases of NSI models including couplings to up quarks only, down quarks only and to protons. The corresponding 2σ ranges are also provided in table 1 for convenience. The main difference introduced by the new oscillation data is that now the two minima corresponding to the degeneracy on ε coh µµ obtained after the inclusion of timing information for COHERENT, is no longer broken after combination with the updated oscillation data. This leads to the appearance of disconnected allowed ranges at 2σ when comparing table 1 with table 2 in ref. [1]. We notice also that at the confidence level shown no LMA-D solution for these specific cases is allowed.
From figure 1 we see that best fit within LMA-D solution is achieved for η ∼ −30 • , which corresponds to a model with couplings to up and down quarks in a ratio ∼ −1.2. Assuming the same coupling normalization employed for the cases of ε u αβ and ε d αβ shown in  In summary, we find that the main effect of the inclusion of the new data -characterized by a smaller tension between the solar and KamLAND results -is the reduction of the improvement of the quality of the fit with NSI with respect to that of pure oscillations within the LMA solution. Conversely LMA-D becomes allowed for a slightly wider range of the η parameter, i.e., for a slightly broader variety of models with NSI couplings to combinations of up and down quarks.
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