Measuring observables to constrain models using maximum-likelihood estimation is fundamental to many physics experiments. Wilks' theorem provides a simple way to construct confidence intervals on model parameters, but it only applies under certain conditions. These conditions, such as nested hypotheses and unbounded parameters, are often violated in neutrino oscillation measurements and other experimental scenarios. Monte Carlo methods can address these issues, albeit at increased computational cost. In the presence of nuisance parameters, however, the best way to implement a Monte Carlo method is ambiguous. This paper documents the method selected by the NOvA experiment, the profile construction. It presents the toy studies that informed the choice of method, details of its implementation, and tests performed to validate it. It also includes some practical considerations which may be of use to others choosing to use the profile construction.
We report cross-section measurements of the final-state muon kinematics for nu mu charged-current interactions in the NOvA near detector using an accumulated 8.09 x 1020 protons on target in the NuMI beam. We present the results as a double-differential cross section in the observed outgoing muon energy and angle, as well as single-differential cross sections in the derived neutrino energy, E nu, and square of the four-momentum transfer, Q(2). We compare the results to inclusive cross-section predictions from various neutrino event generators via chi(2) calculations using a covariance matrix that accounts for bin-to-bin correlations of systematic uncertainties. These comparisons show a clear discrepancy between the data and each of the tested predictions at forward muon angle and low Q(2), indicating a missing suppression of the cross section in current neutrino-nucleus scattering models.
The inclusive electron neutrino charged-current cross section is measured in the NOvA near detector using 8.02×10^{20} protons-on-target in the NuMI beam. The sample of GeV electron neutrino interactions is the largest analyzed to date and is limited by ≃17% systematic rather than the ≃7.4% statistical uncertainties. The double-differential cross section in final-state electron energy and angle is presented for the first time, together with the single-differential dependence on Q^{2} (squared four-momentum transfer) and energy, in the range 1 GeV≤E_{ν}<6 GeV. Detailed comparisons are made to the predictions of the GENIE, GiBUU, NEUT, and NuWro neutrino event generators. The data do not strongly favor a model over the others consistently across all three cross sections measured, though some models have especially good or poor agreement in the single differential cross section vs Q^{2}.
Cross sections for the interaction nu(mu)A -> mu(-)pi X-0 with neutrino energies between 1 and 5 GeV are measured using a sample of 165,000 selected events collected in the NOvA experiment's near detector, a hydrocarbon-based detector exposed to the Neutrinos from the Main Injector beam at the Fermi National Accelerator Laboratory. Results are presented as a flux-averaged total cross section and as differential cross sections in the momenta and angles of the outgoing muon and pi(0), the total four-momentum transfer, and the invariant mass of the hadronic system. Comparisons are made with predictions from a reference version of the GENIE neutrino interaction generator. The measured total cross section of (3.57 +/- 0.44THORN x 10(-39) cm(2) is 7.5% higher than the GENIE prediction, but is consistent within experimental errors.
We present new $\nu_\mu\rightarrow\nu_e$, $\nu_\mu\rightarrow\nu_\mu$, $\overline{\nu}_\mu\rightarrow\overline{\nu}_e$, and $\overline{\nu}_\mu\rightarrow\overline{\nu}_\mu$ oscillation measurements by the NOvA experiment, with a 50% increase in neutrino-mode beam exposure over the previously reported results. The additional data, combined with previously published neutrino and antineutrino data, are all analyzed using improved techniques and simulations. A joint fit to the $\nu_e$, $\nu_\mu$, $\overline{\nu}_e$, and $\overline{\nu}_\mu$ candidate samples within the 3-flavor neutrino oscillation framework continues to yield a best-fit point in the normal mass ordering and the upper octant of the $\theta_{23}$ mixing angle, with $\Delta m^{2}_{32} = (2.41\pm0.07)\times 10^{-3}$ eV$^2$ and $\sin^2\theta_{23} = 0.57^{+0.03}_{-0.04}$. The data disfavor combinations of oscillation parameters that give rise to a large asymmetry in the rates of $\nu_e$ and $\overline{\nu}_e$ appearance. This includes values of the CP-violating phase in the vicinity of $\delta_\text{CP} = \pi/2$ which are excluded by $>3\sigma$ for the inverted mass ordering, and values around $\delta_\text{CP} = 3\pi/2$ in the normal ordering which are disfavored at 2$\sigma$ confidence.
We report a search for a magnetic monopole component of the cosmic-ray flux in a 95-day exposure of the NOvA experiment's Far Detector, a 14 kt segmented liquid scintillator detector designed primarily to observe GeV-scale electron neutrinos. No events consistent with monopoles were observed, setting an upper limit on the flux of 2 x 10(-14) cm(-2) s(-1) sr(-1) at 90% C.L. for monopole speed 6 x 10(-4) < beta < 5 x 10(-3) and mass greater than 5 x 10(8) GeV. Because of NOvA's small overburden of 3 meters-water equivalent, this constraint covers a previously unexplored low-mass region.
We report the rate of cosmic ray air showers with multiplicities exceeding 15 muon tracks recorded in the NOvA Far Detector between May 2016 and May 2018. The detector is located on the surface under an overburden of 3.6 meters water equivalent. We observe a seasonal dependence in the rate of multiple-muon showers, which varies in magnitude with multiplicity and zenith angle. During this period, the effective atmospheric temperature and surface pressure ranged between 210 K to 230 K and 940mbar to 990mbar, respectively; the shower rates are anti-correlated with the variation in the effective temperature. The variations are about 30% larger for the highest multiplicities than the lowest multiplicities and 20% larger for showers near the horizon than vertical showers.
This Letter reports results from the first long-baseline search for sterile antineutrinos mixing in an accelerator-based antineutrino-dominated beam. The rate of neutral-current interactions in the two NOvA detectors, at distances of 1 and 810 km from the beam source, is analyzed using an exposure of 12.51×10^{20} protons-on-target from the NuMI beam at Fermilab running in antineutrino mode. A total of 121 of neutral-current candidates are observed at the far detector, compared to a prediction of 122±11(stat.)±15(syst.) assuming mixing only between three active flavors. No evidence for ν[over ¯]_{μ}→ν[over ¯]_{s} oscillation is observed. Interpreting this result within a 3+1 model, constraints are placed on the mixing angles θ_{24}<25° and θ_{34}<32° at the 90% C.L. for 0.05 eV^{2}≤Δm_{41}^{2}≤0.5 eV^{2}, the range of mass splittings that produces no significant oscillations at the near detector. These are the first 3+1 confidence limits set using long-baseline accelerator antineutrinos.
A search is performed for supernova-like neutrino interactions coincident with 76 gravitational wave events detected by the LIGO/Virgo Collaboration. For 40 of these events, full readout of the time around the gravitational wave is available from the NOvA Far Detector. For these events, we set limits on the fluence of the sum of all neutrino flavors of $F < 7(4)\times 10^{10}\mathrm{cm}^{-2}$ at 90% C.L. assuming energy and time distributions corresponding to the Garching supernova models with masses 9.6(27)$\mathrm{M}_\odot$. Under the hypothesis that any given gravitational wave event was caused by a supernova, this corresponds to a distance of $r > 29(50)$kpc at 90% C.L. Weaker limits are set for other gravitational wave events with partial Far Detector data and/or Near Detector data.
Using the NOvA neutrino detectors, a broad search has been performed for any signal coincident with 28 gravitational wave events detected by the LIGO/Virgo Collaboration between September 2015 and July 2019. For all of these events, NOvA is sensitive to possible arrival of neutrinos and cosmic rays of GeV and higher energies. For five (seven) events in the NOvA Far (Near) Detector, timely public alerts from the LIGO/Virgo Collaboration allowed recording of MeV-scale events. No signal candidates were found.
The two-detector design of the NOvA neutrino oscillation experiment, in which two functionally identical detectors are exposed to an intense neutrino beam, aids in canceling leading order effects of cross-section uncertainties. However, limited knowledge of neutrino interaction cross sections still gives rise to some of the largest systematic uncertainties in current oscillation measurements. We show contemporary models of neutrino interactions to be discrepant with data from NOvA, consistent with discrepancies seen in other experiments. Adjustments to neutrino interaction models in GENIE are presented, creating an effective model that improves agreement with our data. We also describe systematic uncertainties on these models, including uncertainties on multi-nucleon interactions from a newly developed procedure using NOvA near detector data.
The NOvA long-baseline neutrino experiment uses a pair of large, segmented, liquid-scintillator calorimeters to study neutrino oscillations, using GeV-scale neutrinos from the Fermilab NuMI beam. These detectors are also sensitive to the flux of neutrinos which are emitted during a core-collapse supernova through inverse beta decay interactions on carbon at energies of O(10 MeV). This signature provides a means to study the dominant mode of energy release for a core-collapse supernova occurring in our galaxy. We describe the data-driven software trigger system developed and employed by the NOvA experiment to identify and record neutrino data from nearby galactic supernovae. This technique has been used by NOvA to self-trigger on potential core-collapse supernovae in our galaxy, with an estimated sensitivity reaching out to 10 kpc distance while achieving a detection efficiency of 23% to 49% for supernovae from progenitor stars with masses of 9.6 M-circle dot to 27 M-circle dot, respectively.
We present the 1st results of the event-by-event study of long-range correlations between event mean Pt and charged particle multiplicity using NA49 experimental data in two separated rapidity intervals in 158 A *Ge V Pb Pb collisions at the CERN SPS. Noticeable long range correlations are found. The most striking feature is the negative Prn correlation observed for the central PbPb collisions. Results are compared to the predictions of the HIJING event generator and of the String Fusion Model favoring a string fusion hypothesis. Key-words: experiment, relativistic heavy ions, color strings fusion, long-range correlations.
The Daya Bay Reactor Neutrino Experiment is designed to determine precisely the neutrino mixing angle theta(13) with a sensitivity better than 0.01 in the parameter sin(2) 2 theta(13) at the 90% confidence level. To achieve this goal, the collaboration will build eight functionally identical antineutrino detectors. The first two detectors have been constructed, installed and commissioned in Experimental Hall 1, with steady data-taking beginning September 23, 2011. A comparison of the data collected over the subsequent three months indicates that the detectors are functionally identical, and that detector-related systematic uncertainties are smaller than requirements. (C) 2012 Elsevier B.V. All rights reserved.
The performance of prototypes for the ALICE electromagnetic sampling calorimeter has been studied in test beam measurements at FNAL and CERN. A 4×4 array of final design modules showed an energy resolution of about 11%/E(GeV)⊕1.7% with a uniformity of the response to electrons of 1% and a good linearity in the energy range from 10 to 100GeV. The electromagnetic shower position resolution was found to be described by 1.5mm⊕5.3mm/E(GeV). For an electron identification efficiency of 90% a hadron rejection factor of >600 was obtained.
The properties of discontinuous aligned pinning centers (PCs) created by high-energy heavy-ions are compared for bulk melt-textured and coated conductor HTS. Properties of PCs, which increase Jc (pinning potential and entanglement), and negative properties which decrease Jc (e.g., decreased Tc and percolation paths) are evaluated. Mechanisms are proposed to explain the very large increases in Jc resulting from multiple-in-line-damage (MILD) compared to continuous columnar pinning centers (CCPC). In particular, a mechanism which results in fluxoid entanglement, even for parallel (unsplayed) PCs, is discussed. The same mechanism is found to also account for restoration of much of the pinning potential expected to be lost due to the gaps in MILD PCs. It also accounts for the fact that at high fluence, Jc increases as fluence is increased, instead of decreasing as expected. The very low self-field in coated conductor permits separation of the negative and positive effects of PCs. It is found that parameters developed to quantify the negative effects in bulk melt-textured YBCO, by 63GeV U238 ions, successfully describe damage to 2.1μm thick coated conductor by 1GeV Ru44 ions. Coated conductor at 77K and self-field is generally known to have Jc about 100 times that of melt-textured YBCO. However, at 77K and applied field of 1T, when both forms of HTS are processed with comparable numbers of near-optimum MILD PCs, the difference in Jc is reduced to a factor of 1.3–2. Whereas Jc for melt-textured YBCO increased sharply, by a factor of up to 16.8 for high-fluence MILD PCs, Jc in coated conductor increased by a smaller factor of 2.5–3.0. Nevertheless, 2.1μm thick coated conductor, with near-optimum MILD PCs, exhibits Jc=543kA/cm2 at 77K and applied field of 1.0T, and Ic=114 A/cm-width of conductor. This is the highest value we find in the literature. The phenomenology developed indicates that for optimum MILD PCs in coated conductor, Jc∼700±70kA/cm2 should be achievable at 77K, 1.0T.
Columnar defects were produced in melt-textured YBCO by irradiation with high-energy U238 ions at a constant matching field of Bϕ = 10 T and for several energy losses between Se = 1.67 and 2.4 keV/Å. The influence of discontinuous or multiple-in-line-damage (MILD) columnar defects in melt-textured YBCO on flux pinning and the vortex matter phase diagram was investigated. The critical current density jc(H,T) was found to strongly increase with Se due to the increasing length of the MILD pins. Simultaneously, the irreversibility field Birr(T) for fields along the c-axis progressively shifts upwards reaching 9 T at 77 K. For Se= 2.4 keV/Å, a pronounced kink is observed in Birr(T) at 8 T which is a strong indication for Bose glass behaviour. The data for the irradiated YBCO are compared with data for bulk YBCO in which a periodic array of nanoscale twin boundaries was obtained by RuO2 additions.
S.V. Afanasiev,T. Anticic, B. Baatar,D. Barna, J. Bartke, R.A. Barton, M. Behler, L. Betev, H. Bia lkowska, A. Billmeier, C. Blume, C.O. Blyth, B. Boimska, M. Botje, J. Bracinik, R. Bramm, R. Brun, P. Bunčić, V. Cerny, O. Chvala, J.G. Cramer, P. Csató, P. Dinkelaker, V. Eckardt, P. Filip, H.G. Fischer, Z. Fodor, P. Foka, P. Freund, V. Friese, J. Gál, M. Gaździcki, G. Georgopoulos, E. G ladysz, S. Hegyi, C. Höhne, G. Igo, P.G. Jones, K. Kadija, A. Karev, V.I. Kolesnikov, T. Kollegger, M. Kowalski, I. Kraus, M. Kreps, M. van Leeuwen, R. Lednický, P. Lévai, A.I. Malakhov, S. Margetis, C. Markert, B.W. Mayes, G.L. Melkumov, C. Meurer, A. Mischke, M. Mitrovski, J. Molnár, J.M. Nelson, G. Pálla, A.D. Panagiotou, K. Perl, A. Petridis, M. Pikna, L. Pinsky, F. Pühlhofer, J.G. Reid, R. Renfordt, W. Retyk, C. Roland, G. Roland, A. Rybicki, T. Sammer, A. Sandoval, H. Sann, N. Schmitz, P. Seyboth, F. Siklér, B. Sitar, E. Skrzypczak, J. Smolik, G.T.A. Squier, R. Stock, H. Ströbele, T. Susa, I. Szentpétery, J. Sziklai, T.A. Trainor, D. Varga, M. Vassiliou, G.I. Veres, G. Vesztergombi, D. Vranić, S. Wenig, A. Wetzler, C. Whitten, I.K. Yoo, J. Zaranek, J. Zimányi
ALICE (A Large Ion Collider Experiment) at the LHC contains a wide array of detector systems for measuring hadrons, leptons, and photons. ALICE is designed to carry out comprehensive measurements of high energy nucleus-nucleus collisions, in order to study QCD matter under extreme conditions and to study the phase transition between confined matter and the Quark-Gluon Plasma (QGP). Discussion of the full ALICE physics program can be found in [1, 2]. The interaction and energy loss of high energy partons in matter provides a sensitive tomographic probe of the medium generated in high energy nuclear collisions (“jet quenching”) [3–6]. Jet quenching measurements have played a key role at the Relativistic Heavy Ion Collider (RHIC) [7–10] and will be central to the study of nuclear collisions at the LHC. This Technical Design Report describes a large acceptance Electromagnetic Calorimeter (EMCal) that will be installed in the ALICE central detector. The EMCal enhances ALICE's capabilities for jet quenching measurements. The addition of the EMCal enables triggering on high energy jets, reduces significantly the measurement bias for jet quenching studies, improves jet energy resolution, and augments existing ALICE capabilities to measure high momentum photons and electrons. Combined with ALICE's excellent capabilities to track and identify particles from very low pt to high pt the EMCal enables an extensive study of jet quenching at the LHC.
In type II superconductor, pinning centers are essential to obtain high current density, Jc. Conventional wisdom holds that highest Jc is obtained by using continuous columnar pinning centers, which in turn maximize pinning potential. We find this conclusion to be in severe error. Using heavy high-energy ions to insert pinning centers into the YBCO high temperature superconductor, we find peak Jc where pinning centers have 66% discontinuity. Furthermore, this provides record Jc, and peak irreversibility field, Hirr. The values of Jc achieved using discontinuous pinning centers is 5 to 60 times that achieved using continuous columnar pinning centers. We review a phenomenological theory, in its early stages, which matches this experimental result. It indicates that Jc is highest not where pinning potential is largest, but where the combined effects of percolation paths, critical temperature, and pinning potential, are optimized.