Recent QCD studies at the Tevatron

Since the beginning of Run II at the Fermilab Tevatron, the QCD physics groups of the CDF and D0 Collaborations have worked to reach unprecendented levels of precision for many QCD observables. This note summarizes important recent measurements with dataset corresponding to up to 8 fb−1 of total integrated luminosity

Measurement of single π0 production by coherent neutral-current ν Fe interactions in the MINOS Near Detector

Forward single π0 production by coherent neutral-current interactions, νA→νAπ0, is investigated using a 2.8×1020 protons-on-target exposure of the MINOS Near Detector. For single-shower topologies, the event distribution in production angle exhibits a clear excess above the estimated background at very forward angles for visible energy in the range 1-8 GeV. Cross sections are obtained for the detector medium comprised of 80% iron and 20% carbon nuclei with =48, the highest- target used to date in the study of this coherent reaction. The total cross section for coherent neutral-current single π0 production initiated by the νμ flux of the NuMI low-energy beam with mean (mode) Eν of 4.9 GeV (3.0 GeV), is 77.6±5.0(stat)-16.8+15.0(syst)×10-40 cm2 pernucleus. The results are in good agreement with predictions of the Berger-Sehgal model

Constraints on large extra dimensions from the MINOS experiment

We report new constraints on the size of large extra dimensions from data collected by the MINOS experiment between 2005 and 2012. Our analysis employs a model in which sterile neutrinos arise as Kaluza-Klein states in large extra dimensions and thus modify the neutrino oscillation probabilities due to mixing between active and sterile neutrino states. Using Fermilab’s Neutrinos at the Main Injector beam exposure of 10.56 × 1020 protons on target, we combine muon neutrino charged current and neutral current data sets from the Near and Far Detectors and observe no evidence for deviations from standard three-flavor neutrino oscillations. The ratios of reconstructed energy spectra in the two detectors constrain the size of large extra dimensions to be smaller than 0.45 μm at 90% C.L. in the limit of a vanishing lightest active neutrino mass. Stronger limits are obtained for nonvanishing masses

Search for flavor-changing nonstandard neutrino interactions using νe appearance in MINOS

We report new constraints on flavor-changing nonstandard neutrino interactions from the MINOS longbaseline experiment using νe and ¯νe appearance candidate events from predominantly νμ and ¯νμ beams. We used a statistical selection algorithm to separate νe candidates from background events, enabling an analysis of the combined MINOS neutrino and antineutrino data. We observe no deviations from standard neutrino mixing, and thus place constraints on the nonstandard interaction matter effect, |εeτ|, and phase, (δCP + δeτ), using a 30-bin likelihood fit

Measurement of single π0 production by coherent neutral-current ν Fe interactions in the MINOS Near Detector

Forward single π0 production by coherent neutral-current interactions, νA → νAπ0, is investigated using a 2.8 × 10^20 protons-on-target exposure of the MINOS Near Detector. For single-shower topologies, the event distribution in production angle exhibits a clear excess above the estimated background at very forward angles for visible energy in the range 1–8 GeV. Cross sections are obtained for the detector medium comprised of 80% iron and 20% carbon nuclei with = 48, the highest- target used to date in the study of this coherent reaction. The total cross section for coherent neutral-current single π0 production initiated by the νμ flux of the NuMI low-energy beam with mean (mode) Eν of 4.9 GeV (3.0 GeV), is 77.6±5.0(stat)+15.0−16.8 (syst) × 10−40 cm2 pernucleus. The results are in good agreement with predictions of the Berger-Sehgal model

Study of quasielastic scattering using charged-current νμ-iron interactions in the MINOS near detector

Kinematic distributions from an inclusive sample of 1.41 × 10^6 charged-current νμ interactions on iron, obtained using the MINOS near detector exposed to a wide-band beam with peak flux at 3 GeV, are compared to a conventional treatment of neutrino scattering within a Fermi gas nucleus. Results are used to guide the selection of a subsample enriched in quasielastic νμFe interactions, containing an estimated 123,000 quasielastic events of incident energies 1 < Eν < 8 GeV, with hEνi ¼ 2.79 GeV. Four additional subsamples representing topological and kinematic sideband regions to quasielastic scattering are also selected for the purpose of evaluating backgrounds. Comparisons using subsample distributions in fourmomentum transfer Q^2 show the Monte Carlo model to be inadequate at low Q^2. Its shortcomings are remedied via inclusion of a Q^2-dependent suppression function for baryon resonance production, developed from the data. A chi-square fit of the resulting Monte Carlo simulation to the shape of the Q2 distribution for the quasielastic-enriched sample is carried out with the axial-vector mass MA of the dipole axial-vector form factor of the neutron as a free parameter. The effective MA which best describes the data is 1.23+0.13−0.09 (fit)+0.12−0.15 (syst) GeV

Comparisons of annual modulations in MINOS with the event rate modulation in CoGeNT

The CoGeNT Collaboration has recently published results from a fifteen month data set which indicate an annual modulation in the event rate similar to what is expected from weakly interacting massive particle interactions. It has been suggested that the CoGeNT modulation may actually be caused by other annually modulating phenomena, specifically the flux of atmospheric muons underground or the radon level in the laboratory. We have compared the phase of the CoGeNT data modulation to that of the concurrent atmospheric muon and radon data collected by the MINOS experiment which occupies an adjacent experimental hall in the Soudan Underground Laboratory. The results presented are obtained by performing a shape-free χ^2 data-to-data comparison and from a simultaneous fit of the MINOS and CoGeNT data to phase-shifted sinusoidal functions. Both tests indicate that the phase of the CoGeNT modulation is inconsistent with the phases of the MINOS muon and radon modulations at the 3.0σ level

Observation of muon intensity variations by season with the MINOS near detector

A sample of 1.53×109 cosmic-ray-induced single muon events has been recorded at 225 m water equivalent using the MINOS near detector. The underground muon rate is observed to be highly correlated with the effective atmospheric temperature. The coefficient αT, relating the change in the muon rate to the change in the vertical effective temperature, is determined to be 0.428±0.003(stat.)±0.059(syst.). An alternative description is provided by the weighted effective temperature, introduced to account for the differences in the temperature profile and muon flux as a function of zenith angle. Using the latter estimation of temperature, the coefficient is determined to be 0.352±0.003(stat.)±0.046(syst.)

Combined analysis of νμ disappearance and νμ → νe appearance in MINOS using accelerator and atmospheric neutrinos

We report on a new analysis of neutrino oscillations in MINOS using the complete set of accelerator and atmospheric data. The analysis combines the νμ disappearance and νe appearance data using the three-flavor formalism. We measure |Δm^2 32| = [2.28–2.46] × 10−3 eV^2 (68% C.L.) and sin^2 θ23 = 0.35–0.65 (90% C.L.) in the normal hierarchy, and |Δm^2 32| = [2.32–2.53] × 10−3 eV^2 (68% C.L.) and sin^2 θ23 = 0.34–0.67 (90% C.L.) in the inverted hierarchy. The data also constrain δCP, the θ23 octant degeneracy and the mass hierarchy; we disfavor 36% (11%) of this three-parameter space at 68% (90%) C.L