beamExposure:
name: Beam exposure
value: 7.47594
units: GW*hr
uncertainty: negligible
comment: |
This is the effective SNS beam exposure for the Chicago analysis of the first result from the COHERENT Collaboration.
This represents the effective exposure for the data released here, and is reflective of the result from the 2017 Science publication.
distanceToTarget:
name: Distance to target
value: 19.3
units: m
uncertainty: negligible
comment: |
This value was determined from a LIDAR scan of the neutrino alley target area carried out by the survey and alignment team of the SNS.
csiQF:
name: CsI-Na quenching factor
value: 0.0878
units: none
uncertainty: 0.0166
comment: |
This value for the QF was determined based on a fit to all available data points, including those from COHERENT measurements and others from literature.
A weighted average between 5 and 30 keVnr determined the mean value, while the uncertainty was defined by the unweighted standard deviation of these points.
To convert nuclear-recoil energy X into electron-equivalent energy, multiply X by the quenching factor.
csiLightYield:
name: Light yield for CsI-Na
value: 13.348
units: PE/keVee
uncertainty: 0.019
comment: |
Light yield for CsI-Na detector measured at 59.54 keV 241Am line.
This is the average of several measurements made along the length of the detector.
neutrinosPerProton:
name: Neutrinos produced per SNS proton
value: 0.08
uncertainty: 0.008
units: nu/flavor/proton
comment: |
This is the number of decay-at-rest neutrinos produced per incident SNS beam proton per neutrino flavor.
The DAR neutrinos are emitted isotropically.
promptNeutronNormalization:
name: Normalization constant of prompt neutron PDF
value: 1
uncertainty: 0.25
units: none
comment: |
The PDF included is normalized so that bin values represent the number of counts expected per GW-hr of SNS beam exposure.
After scaling for exposure, the overall uncertainty of the normalization on the prompt PDF is 25 percent.
acceptanceEfficiency:
name: Acceptance efficiency parameters
parameters:
- name: a
value: 0.6655
error_hi: 0.0212
error_lo: 0.0384
- name: k
value: 0.4942
error_hi: 0.0335
error_lo: 0.0131
- name: x_0
value: 10.8507
error_hi: 0.1838
error_lo: 0.3995
comment: |
Analysis efficiency is described by f(x) = a/(1.0 + exp(-k*(x - x_0))) * H(x-5)
Where H(x) denotes a modified Heaviside step function and the parameter values are included here, along with asymmetric, 1-sigma errors.
H(x) has a value of 0 for x < 5; a value of 1/2 for 5 <= x < 6; and a value of 1 for x >= 6.
This efficiency must be applied to any calculated CEvNS recoil curves, as well as the prompt-neutron distribution, before the distributions are compared with data.
It is applied to distributions binned with 1-PE bin widths, and the effective efficiency value for each bin is taken as the value of this function at the bin center (e.g., evaluated at 0.5 for the 1-PE bin, evaluated at 1.5 for the 2-PE bin, etc).