The double-differential quasi-elastic-like (CCQE) anti-neutrino cross section from the MINERvA experiment medium energy sample as a function of transverse (pT) and longitudinal (p||) momentum. The dark points are the data and the curves show various neutrino interactions models.
Amit Bashyal’s thesis work on anti-neutrino quasi-elastic scattering has been published as Bashyal et. al., “High-statistics measurement of antineutrino quasielastic-like scattering at Eν ~ 6 GeV on a hydrocarbon target”, Phys. Rev. D 108, 032018 , in the August 1 issue of Physical Review D. This paper uses the full MINERvA medium-energy data sample with 635,592 candidate interactions and the improved MINERvA neutrino flux and energy scale (see Amit’s previous paper, Bashyal et. al., “Use of neutrino scattering events with low hadronic recoil to inform neutrino flux and detector energy scale”, 2021 JINST16 ).
Left: Measured (data points) and MINERvA Tune v1 prediction (dotted lines) of CCQE-like dσ/dQ2 for neutrinos (red) and antineutrinos (this measurement, black) extracted with at neutrino and antineutrinos energies ∼6 GeV. Right: Summary of fractional uncertainties on the differential antineutrino cross section as a function of Q2.
Comparisons of the cross section predicted by various tunes applied on GENIE with respect to the baseline GENIE 2.12.6 (black) as a function of Q2 (left). MINERvA Tune v1 (blue) is the standard simulation tuned to the MINERvA low energy data. MINERvA Tune v2 (red) is MINERvA Tune v1 with non-resonant pions suppressed in the low Q2 region. The remaining curves on the left show the effect of enabling different corrections to the base model. The plots on the right show comparisons of cross-section predictions for GENIE v3.0.6 (dotted lines) with the MINERvA tuned GENIE v2.12.6 predictions. Inner error bars represent statistical uncertainties and outer error bars represent systematic uncertainties.
The new GENIE 3 series models do a much better job of explaining the high Q2 dependence of the observed cross section.
Full details are available in his doctoral thesis. Amit is now a postdoc at Argonne National Laboratory.
Postdoc Mateus Carneiro has moved on to a position at Brookhaven National Laboratory but he left us with a really nice paper in Physics Review Letters.
M.Carneiro et al. [MINERvA], “High-Statistics Measurement of Neutrino Quasielasticlike Scattering at 6 GeV on a Hydrocarbon Target”, Phys. Rev. Lett. 124, no.12, 121801 (2020), doi:10.1103/PhysRevLett.124.121801
Graduate Student Amit Bashyal did many of the cross-checks for this complicated measurement and wrote a summary for FermiNews which is copied below. Amit’s thesis topic is the parallel measurement for anti-neutrinos.
Hard to believe you can play pool with neutrinos, but certain neutrino interaction events are closer to the game than you think.
In these charged-current quasielastic interactions — let’s call them CCQE interactions for short — a neutrino strikes a particle in an atom’s nucleus — a proton or a neutron. Two particles emerge from the collision. One is a muon, a heavier cousin of the electron. The other is either a proton (if the stationary particle is a neutron) or a neutron (if the stationary particle is a proton).
The neutrino interactions that result from these quasielastic reactions are like the collisions between balls in a game of pool: You can guess the energy of the incoming neutrino by measuring the direction and energy of only one of the outgoing particles, provided you know the types of all four particles that were in the interaction in the first place and the original direction of the neutrino.
CCQE interactions are an important interaction mode of neutrinos in current and future neutrino oscillation experiments, such as the international Deep Underground Neutrino Experiment, hosted by Fermilab.
They are similar to the elastic interactions every pool player knows except in one important way: The weak nuclear force allows the particles to change from one kind into another, hence the “quasielastic” name. In this subatomic pool game, the cue ball (neutrino) strikes a stationary red ball (proton), which emerges from the collision as an orange ball (neutron).
This display shows a CCQE-like event reconstructed in the MINERvA detector. Image: MINERvA
Since most modern neutrino experiments use targets made of heavy nuclei ranging from carbon to argon, nuclear effects and correlations between the neutrons and protons inside the nucleus can cause significant changes in the observed interaction rates and modifications to the estimated neutrino energy.
At MINERvA, scientists identify the CCQE interactions by a long muon track left in the particle detector and potentially one or more proton tracks. However, this experimental signature can sometimes be produced by non-CCQE interactions due to nuclear effects inside the target nucleus. Similarly, nuclear effects can also modify the final-state particles to make a CCQE event look like a non-CCQE event and vice versa.
Since nuclear effects can make it challenging to identify a true CCQE event, MINERvA reports measurements based on the properties of the final-state particles only and calls them CCQE-like events (since they will have contributions from both true CCQE and non-CCQE events). A CCQE-like event is one that has at least one outgoing muon, any number of protons or neutrons, and no mesons as final-state particles. (Mesons, like protons and neutrons, are made of quarks. Protons and neutrons have three quarks; mesons have two.)
MINERvA has measured the likelihood of CCQE-like neutrino interactions using Fermilab’s medium-energy neutrino beam, with the neutrino flux peaking at 6 GeV. Compared to MINERvA’s earlier measurements, which were conducted with a low-energy beam (3 GeV peak neutrino flux), this measurement has the advantage of a broader energy reach and much larger statistics: 1,318,540 CCQE-like events compared to 109,275 events in earlier low-energy runs.
MINERvA made these CCQE interaction probability measurements as a function of the square of the momentum transferred by the neutrino to the nucleus, which scientists denote as Q2. The plot shows discrepancies between the data and most predictions in low-Q2 and high-Q2 regions. By comparing MINERvA’s measurement with various models, scientists can refine them and better explain the physics inside the nuclear environment.
This plot shows the ratio of cross-section as a function of Q2 of data and various predictions with respectto one commonly used interaction model. Image: MINERvA
MINERvA has also made more detailed measurements of the probability of neutrino interaction based on the outgoing muon’s momentum. They take into account the muon’s momentum both in the direction of the incoming neutrino’s trajectory and in the direction perpendicular to its trajectory. This work helps current and future neutrino experiments understand their own data over a wide range of muon kinematics.
Mateus Carneiro, formerly of the Brazilian Center for Research in Physics and Oregon State University and now at Brookhaven National Laboratory, and Dan Ruterbories of the University of Rochester were the main drivers of this analysis. The results were published in Physical Review Letters.
Amit Bashyal is an Oregon State University scientist on the MINERvA experiment.
This work is supported by the DOE Office of Science, National Science Foundation, Coordination for the Improvement of Higher Education Personnel in Brazil, Brazilian National Council for Scientific and Technological Development, Mexican National Council of Science and Technology, Basal Project in Chile, Chilean National Commission for Scientific and Technological Research, Chilean National Fund for Scientific and Technological Development, Peruvian National Council for Science, Technology and Technological Innovation, Research Management Directorate at the Pontifical Catholic University of Peru, National University of Engineering in Peru, Polish National Science Center and UK Science and Technology Facilities Council.
Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.
Differential QE-like cross section dσ(E_QEν)/dQ^2_QE, in bins of E_QEν. Inner error bars show statistical uncertainties; outer error bars show total (statistical and systematic) uncertainty. The red histogram shows the MINERvA-tuned GENIE model used to estimate smearing and acceptance.
The much anticipated paper version of Cheryl Patrick’s thesis has been accepted by Physical Review D. Check it out at:
