Search for Sterile Neutrinos in MINOS and MINOS+ Using a Two-Detector Fit.

A search for mixing between active neutrinos and light sterile neutrinos has been performed by looking for muon neutrino disappearance in two detectors at baselines of 1.04 and 735 km, using a combined MINOS and MINOS+ exposure of 16.36×10^{20} protons on target. A simultaneous fit to the charged-current muon neutrino and neutral-current neutrino energy spectra in the two detectors yields no evidence for sterile neutrino mixing using a 3+1 model. The most stringent limit to date is set on the mixing parameter sin^{2}θ_{24} for most values of the sterile neutrino mass splitting Δm_{41}^{2}>10^{-4} eV^{2}.

Constraints on Oscillation Parameters from ν_{e} Appearance and ν_{µ} Disappearance in NOvA.

Results are reported from an improved measurement of ν_{µ}→ν_{e} transitions by the NOvA experiment. Using an exposure equivalent to 6.05×10^{20} protons on target, 33 ν_{e} candidates are observed with a background of 8.2±0.8 (syst.). Combined with the latest NOvA ν_{µ} disappearance data and external constraints from reactor experiments on sin^{2}2θ_{13}, the hypothesis of inverted mass hierarchy with θ_{23} in the lower octant is disfavored at greater than 93% C.L. for all values of δ_{CP}.

Measurement of the Neutrino Mixing Angle θ_{23} in NOvA.

This Letter reports new results on muon neutrino disappearance from NOvA, using a 14 kton detector equivalent exposure of 6.05×10^{20} protons on target from the NuMI beam at the Fermi National Accelerator Laboratory. The measurement probes the muon-tau symmetry hypothesis that requires maximal θ_{23} mixing (θ_{23}=π/4). Assuming the normal mass hierarchy, we find Δm_{32}^{2}=(2.67±0.11)×10^{-3} eV^{2} and sin^{2}θ_{23} at the two statistically degenerate values 0.404_{-0.022}^{+0.030} and 0.624_{-0.030}^{+0.022}, both at the 68% confidence level. Our data disfavor the maximal mixing scenario with 2.6σ significance.

Search for Sterile Neutrinos Mixing with Muon Neutrinos in MINOS.

We report results of a search for oscillations involving a light sterile neutrino over distances of 1.04 and 735 km in a ν_{µ}-dominated beam with a peak energy of 3 GeV. The data, from an exposure of 10.56×10^{20} protons on target, are analyzed using a phenomenological model with one sterile neutrino. We constrain the mixing parameters θ_{24} and Δm_{41}^{2} and set limits on parameters of the four-dimensional Pontecorvo-Maki-Nakagawa-Sakata matrix, |U_{µ4}|^{2} and |U_{τ4}|^{2}, under the assumption that mixing between ν_{e} and ν_{s} is negligible (|U_{e4}|^{2}=0). No evidence for ν_{µ}→ν_{s} transitions is found and we set a world-leading limit on θ_{24} for values of Δm_{41}^{2}≲1 eV^{2}.

Limits on Active to Sterile Neutrino Oscillations from Disappearance Searches in the MINOS, Daya Bay, and Bugey-3 Experiments.

Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on sin^{2}2θ_{µe} are set over 6 orders of magnitude in the sterile mass-squared splitting Δm_{41}^{2}. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for Δm_{41}^{2}<0.8 eV^{2} at 95% CL_{s}.

First Measurement of Electron Neutrino Appearance in NOvA.

We report results from the first search for ν_{µ}→ν_{e} transitions by the NOvA experiment. In an exposure equivalent to 2.74×10^{20} protons on target in the upgraded NuMI beam at Fermilab, we observe 6 events in the Far Detector, compared to a background expectation of 0.99±0.11(syst) events based on the Near Detector measurement. A secondary analysis observes 11 events with a background of 1.07±0.14(syst). The 3.3σ excess of events observed in the primary analysis disfavors 0.1π<δ_{CP}<0.5π in the inverted mass hierarchy at the 90% C.L.

Observation of the ψ(1 3D2) State in e+e-→π+π-γχc1 at BESIII.

We report the observation of the X(3823) state in the process e+e-→π+π-X(3823)→π+π-γχc1 with a statistical significance of 6.2σ, in data samples at center-of-mass energies sqrt[s]=4.230, 4.260, 4.360, 4.420, and 4.600 GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the X(3823) state is (3821.7±1.3±0.7) MeV/c2, where the first error is statistical and the second systematic, and the width is less than 16 MeV at the 90% confidence level. The products of the Born cross sections for e+e-→π+π-X(3823) and the branching ratio B[X(3823)→γχc1,c2] are also measured. These measurements are in good agreement with the assignment of the X(3823) state as the ψ(1 3D2) charmonium state.

Study of e(+)e(-)→ωχ(cJ) at center of mass energies from 4.21 to 4.42 GeV.

Based on data samples collected with the BESIII detector at the BEPCII collider at nine center of mass energies from 4.21 to 4.42 GeV, we search for the production of e^{+}e^{-}→ωχ_{cJ} (J=0, 1, 2). The process e^{+}e^{-}→ωχ_{c0} is observed for the first time, and the Born cross sections at sqrt[s]=4.23 and 4.26 GeV are measured to be (55.4±6.0±5.9) and (23.7±5.3±3.5) pb, respectively, where the first uncertainties are statistical and the second are systematic. The ωχ_{c0} signals at the other seven energies and the e^{+}e^{-}→ωχ_{c1} and ωχ_{c2} signals are not significant, and the upper limits on the cross sections are determined. By examining the ωχ_{c0} cross section as a function of center of mass energy, we find that it is inconsistent with the line shape of the Y(4260) observed in e^{+}e^{-}→π^{+}π^{-}J/ψ. Assuming the ωχ_{c0} signals come from a single resonance, we extract the mass and width of the resonance to be (4230±8±6) MeV/c^{2} and (38±12±2) MeV, respectively, and the statistical significance is more than 9σ.

Observation of e(+)e(-)→π(0)π(0)hc and a neutral charmoniumlike structure Zc(4020)(0).

Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at center-of-mass energies of sqrt[s]=4.23, 4.26, and 4.36 GeV, we observe e(+)e(-)→π(0)π(0)hc for the first time. The Born cross sections are measured and found to be about half of those of e(+)e(-)→π(+)π(-)hc within less than 2σ. In the π(0)hc mass spectrum, a structure at 4.02 GeV/c(2) is found. It is most likely to be the neutral isospin partner of the Zc(4020)(±) observed in the process of e(+)e(-)→π(+)π(-)hc being found. A fit to the π(0)hc invariant mass spectrum, with the width of the Zc(4020)(0) fixed to that of its charged isospin partner and possible interferences with non-Zc(4020)(0) amplitudes neglected, gives a mass of (4023.9±2.2±3.8) MeV/c(2) for the Zc(4020)(0), where the first error is statistical and the second systematic.

Observation of η'→π+ π π+ π- and η'→π+π- π0 π0.

Using a sample of 1.3 × 10(9) J/ψ events collected with the BESIII detector, we report the first observation of η(')→π(+)π(-)π(+)π(-) and η(')→π(+)π(-)π(0)π(0). The measured branching fractions are B(η(')→π(+)π(-)π(+)π(-)) = [8.53 ± 0.69(stat.) ± 0.64(syst.)]×10(-5) and B(η(')→π(+)π(-)π(0) π(0)) = [1.82 ± 0.35(stat.) ± 0.18(syst.)] × 10(-4), which are consistent with theoretical predictions based on a combination of chiral perturbation theory and vector-meson dominance.

Combined analysis of νµ disappearance and νµâ†’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 ν(µ) disappearance and ν(e) appearance data using the three-flavor formalism. We measure |Δm(32)(2)| = [2.28-2.46] × 10(-3) eV(2) (68% C.L.) and sin(2)θ(23) = 0.35-0.65 (90% C.L.) in the normal hierarchy, and |Δm(32)(2)| = [2.32-2.53] × 10(-3) eV(2) (68% C.L.) and sin(2)θ(23) = 0.34-0.67 (90% C.L.) in the inverted hierarchy. The data also constrain δ(CP), the θ(23} octant degeneracy and the mass hierarchy; we disfavor 36% (11%) of this three-parameter space at 68% (90%) C.L.

Observation of a charged charmoniumlike structure in e+ e- → (D* D*)± π∓ at √s = 4.26 GeV.

We study the process e+ e- →(D* D*)± π∓ at a center-of-mass energy of 4.26 GeV using a 827 pb(-1) data sample obtained with the BESIII detector at the Beijing Electron Positron Collider. Based on a partial reconstruction technique, the Born cross section is measured to be (137±9±15) pb. We observe a structure near the (D* D*)± threshold in the π∓ recoil mass spectrum, which we denote as the Zc±(4025). The measured mass and width of the structure are (4026.3±2.6±3.7) MeV/c2 and (24.8±5.6±7.7) MeV, respectively. Its production ratio σ(e+ e- → Zc±(4025)π∓ → (D* D*)± π∓)/σ(e+ e- → (D* D*)± π∓) is determined to be 0.65±0.09±0.06. The first uncertainties are statistical and the second are systematic.

Observation of e+e- → γX(3872) at BESIII.

With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process e+e-→ γX(3872) is observed for the first time with a statistical significance of 6.3σ. The measured mass of the X(3872) is (3871.9 ± 0.7s tat ± 0.2 syst) MeV/c(2), in agreement with previous measurements. Measurements of the product of the cross section σ[e+e- → γX(3872)] and the branching fraction B[X(3872)→π+π-J/ψ] at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process Y(4260) → γX(3872).

Observation of a charged (DD*)± mass peak in e+ e- → πDD* at sqrt[s] = 4.26 GeV.

We report on a study of the process e+ e- → π± (DD*)∓ at sqrt[s] = 4.26 GeV using a 525 pb(-1) data sample collected with the BESIII detector at the BEPCII storage ring. A distinct charged structure is observed in the (DD*)∓ invariant mass distribution. When fitted to a mass-dependent-width Breit-Wigner line shape, the pole mass and width are determined to be Mpole = (3883.9±1.5(stat)±4.2(syst)) MeV/c2 and Γpole = (24.8±3.3(stat)±11.0(syst)) MeV. The mass and width of the structure, which we refer to as Zc(3885), are 2σ and 1σ, respectively, below those of the Zc(3900) → π± J/ψ peak observed by BESIII and Belle in π+ π- J/ψ final states produced at the same center-of-mass energy. The angular distribution of the πZc(3885) system favors a JP = 1+ quantum number assignment for the structure and disfavors 1- or 0-. The Born cross section times the DD* branching fraction of the Zc(3885) is measured to be σ(e+ e- → π± Zc(3885)∓)×B(Zc(3885)∓ → (DD*)∓) = (83.5±6.6(stat)±22.0(syst)) pb. Assuming the Zc(3885) → DD* signal reported here and the Zc(3900) → πJ/ψ signal are from the same source, the partial width ratio (Γ(Zc(3885) → DD*)/Γ(Zc(3900) → πJ/ψ)) = 6.2±1.1(stat)±2.7(syst) is determined.

Measurement of neutrino and antineutrino oscillations using beam and atmospheric data in MINOS.

We report measurements of oscillation parameters from ν(µ) and ν(µ) disappearance using beam and atmospheric data from MINOS. The data comprise exposures of 10.71×10(20) protons on target in the ν(µ)-dominated beam, 3.36×10(20) protons on target in the ν(µ)-enhanced beam, and 37.88 kton yr of atmospheric neutrinos. Assuming identical ν and ν oscillation parameters, we measure |Δm2| = (2.41(-0.10)(+0.09))×10(-3) eV2 and sin2(2θ) = 0.950(-0.036)(+0.035). Allowing independent ν and ν oscillations, we measure antineutrino parameters of |Δm2| = (2.50(-0.25)(+0.23))×10(-3) eV2 and sin2(2θ) = 0.97(-0.08)(+0.03), with minimal change to the neutrino parameters.

Observation of a charged charmoniumlike structure in e+ e- → π+ π- J/ψ at sqrt[s] = 4.26 GeV.

We study the process ee+ e- → π+ π- J/ψ at a center-of-mass energy of 4.260 GeV using a 525 pb(-1) data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross section is measured to be (62.9±1.9±3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c2 in the π(±)J/ψ mass spectrum, which we refer to as the Z(c)(3900). If interpreted as a new particle, it is unusual in that it carries an electric charge and couples to charmonium. A fit to the π(±)J/ψ invariant mass spectrum, neglecting interference, results in a mass of (3899.0±3.6±4.9) MeV/c2 and a width of (46±10±20) MeV. Its production ratio is measured to be R = (σ(e+ e- → π(±)Z(c)(3900)(∓) → π+ π- J/ψ)/σ(e+ e- → π+ π- J/ψ)) = (21.5±3.3±7.5)%. In all measurements the first errors are statistical and the second are systematic.

Electron neutrino and antineutrino appearance in the full MINOS data sample.

We report on ν(e) and ν(e) appearance in ν(µ) and ν(µ) beams using the full MINOS data sample. The comparison of these ν(e) and ν(e) appearance data at a 735 km baseline with θ13 measurements by reactor experiments probes δ, the θ23 octant degeneracy, and the mass hierarchy. This analysis is the first use of this technique and includes the first accelerator long-baseline search for ν(µ) → ν(e). Our data disfavor 31% (5%) of the three-parameter space defined by δ, the octant of the θ23, and the mass hierarchy at the 68% (90%) C.L. We measure a value of 2sin(2)(2θ13)sin(2)(θ23) that is consistent with reactor experiments.

Observation of two new N* resonances in the decay ψ(3686)→ppπ0.

Based on 106×10(6)ψ(3686) events collected with the BESIII detector at the BEPCII facility, a partial wave analysis of ψ(3686)→ppπ0 is performed. The branching fraction of this channel has been determined to be B(ψ(3686)→ppπ0)=(1.65±0.03±0.15)×10(-4). In this decay, 7 N* intermediate resonances are observed. Among these, two new resonances, N(2300) and N(2570) are significant, one 1/2+ resonance with a mass of 2300(-30-0)(+40+109) MeV/c2 and width of 340(-30-58)(+30+110) MeV/c2, and one 5/2- resonance with a mass of 2570(-10-10)(+19+34) MeV/c2 and width of 250(-24-21)(+14+69) MeV/c2. For the remaining 5 N* intermediate resonances [N(1440), N(1520), N(1535), N(1650) and N(1720)], the analysis yields mass and width values that are consistent with those from established resonances.

Observation of a charged charmoniumlike structure Zc(4020) and search for the Zc(3900) in e+e-→π+π-hc.

We study e+e-→π+π-hc at center-of-mass energies from 3.90 to 4.42 GeV by using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies and are found to be of the same order of magnitude as those of e+e-→π+π-J/ψ but with a different line shape. In the π±hc mass spectrum, a distinct structure, referred to as Zc(4020), is observed at 4.02 GeV/c2. The Zc(4020) carries an electric charge and couples to charmonium. A fit to the π±hc invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9±0.8±2.7) MeV/c2 and a width of (7.9±2.7±2.6) MeV for the Zc(4020), where the first errors are statistical and the second systematic. The difference between the parameters of this structure and the Zc(4025) observed in the D*D[over ¯]* final state is within 1.5σ, but whether they are the same state needs further investigation. No significant Zc(3900) signal is observed, and upper limits on the Zc(3900) production cross sections in π±hc at center-of-mass energies of 4.23 and 4.26 GeV are set.

Evidence for the direct two-photon transition from ψ(3686) to J/ψ.

The two-photon transition ψ(3686)→γγJ/ψ is studied in a sample of 1.06×10(8) ψ(3686) decays collected by the BESIII detector. The branching fraction is measured to be (3.1±0.6(stat)(-1.0)(+0.8)(syst))×10(-4) using J/ψ→e(+)e(-) and J/ψ→µ(+)µ(-) decays, and its upper limit is estimated to be 4.5×10(-4) at the 90% confidence level. This work represents the first measurement of a two-photon transition among charmonium states. The orientation of the ψ(3686) decay plane and the J/ψ polarization in this decay are also studied. In addition, the product branching fractions of sequential E1 transitions ψ(3686)→γχ(cJ) and χ(cJ)→γJ/ψ(J=0,1,2) are reported.