arXiv subjects

NOMAD Collaboration

Publications and source records attributed to NOMAD Collaboration.

11 recordsLinked to original sources

arXiv2013

A Precision Measurement of Charm Dimuon Production in Neutrino Interactions from the NOMAD Experiment

We present our new measurement of the cross-section for charm dimuon production in neutrino-iron interactions based upon the full statistics collected by the NOMAD experiment. After background subtraction we observe 15,344 charm dimuon events, providing the largest sample currently available. The analysis exploits the large inclusive charged current sample - about $9\times 10^6$ events after all analysis cuts - and the high resolution NOMAD detector to constrain the total systematic uncertainty on the ratio of charm dimuon to inclusive Charged Current (CC) cross-sections to $\sim 2%$. We also perform a fit to the NOMAD data to extract the charm production parameters and the strange quark sea content of the nucleon within the NLO QCD approximation. We obtain a value of $m_c(m_c)=1.159\pm0.075$ GeV/c$^2$ for the running mass of the charm quark in the $\bar{\rm MS}$ scheme and a strange quark sea suppression factor of $κ_s = 0.591 \pm 0.019$ at $Q^2=20$ GeV$^2$/c$^2$.

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arXiv2009

A study of quasi-elastic muon neutrino and antineutrino scattering in the NOMAD experiment

We have studied the muon neutrino and antineutrino quasi-elastic (QEL) scattering reactions ($ν_μn\to μ^- p$ and $\barν_μp\to μ^+ n$) using a set of experimental data collected by the NOMAD collaboration. We have performed measurements of the cross-section of these processes on a nuclear target (mainly Carbon) normalizing it to the total $ν_μ$ ($\barν_μ$) charged current cross-section. The results for the flux averaged QEL cross-sections in the (anti)neutrino energy interval 3-100 GeV are $σ^{qel}_{ν_μ} = (0.92 \pm 0.02 (stat) \pm 0.06 (syst))\times 10^{-38} \cm^2$ and $σ{qel}_{\barν_μ} = (0.81 \pm 0.05 (stat) \pm 0.08 (syst))\times 10^{-38} \cm^2$ for neutrino and antineutrino, respectively. The axial mass parameter $M_A$ was extracted from the measured quasi-elastic neutrino cross-section. The corresponding result is $M_A = 1.05 \pm 0.02 (stat) \pm 0.06 (syst) GeV$. It is consistent with the axial mass values recalculated from the antineutrino cross-section and extracted from the pure $Q^2$ shape analysis of the high purity sample of $ν_μ$ quasi-elastic 2-track events, but has smaller systematic error and should be quoted as the main result of this work. Our measured $M_A$ is found to be in good agreement with the world average value obtained in previous deuterium filled bubble chamber experiments. The NOMAD measurement of $M_A$ is lower than those recently published by K2K and MiniBooNE collaborations. However, within the large errors quoted by these experiments on $M_A$, these results are compatible with the more precise NOMAD value.

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arXiv2007

A Precise Measurement of the Muon Neutrino-Nucleon Inclusive Charged Current Cross-Section off an Isoscalar Target in the Energy Range 2.5 < E_ν< 40 GeV by NOMAD

We present a measurement of the muon neutrino-nucleon inclusive charged current cross-section, off an isoscalar target, in the neutrino energy range $2.5 \leq E_ν\leq 40$ GeV. The significance of this measurement is its precision, $\pm 4$% in $2.5 \leq E_ν\leq 10$ GeV, and $\pm 2.6$% in $10 \leq E_ν\leq 40$ GeV regions, where significant uncertainties in previous experiments still exist, and its importance to the current and proposed long baseline neutrino oscillation experiments.

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arXiv2006

Production properties of K*(892) vector mesons and their spin alignment as measured in the NOMAD experiment

First measurements of K*(892) mesons production properties and their spin alignment in nu_mu charged current (CC) and neutral current (NC) interactions are presented. The analysis of the full data sample of the NOMAD experiment is performed in different kinematic regions. For K*+ and K*- mesons produced in nu_mu CC interactions and decaying into K0 pi+/- we have found the following yields per event: (2.6 +/- 0.2 (stat.) +/- 0.2 (syst.))% and (1.6 +/- 0.1 (stat.) +/- 0.1 (syst.))% respectively, while for the K*+ and K*- mesons produced in nu NC interactions the corresponding yields per event are: (2.5 +/- 0.3 (stat.) +/- 0.3 (syst.))% and (1.0 +/- 0.3 (stat.) +/- 0.2 (syst.))%. The results obtained for the rho00 parameter, 0.40 +/- 0.06 (stat) +/- 0.03 (syst) and 0.28 +/- 0.07 (stat) +/- 0.03 (syst) for K*+ and K*- produced in nu_mu CC interactions, are compared to theoretical predictions tuned on LEP measurements in e+e- annihilation at the Z0 pole. For K*+ mesons produced in nu NC interactions the measured rho00 parameter is 0.66 +/- 0.10 (stat) +/- 0.05 (syst).

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arXiv2004

A Study of Strange Particles Produced in Neutrino Neutral Current Interactions in the NOMAD Experiment

Results of a detailed study of strange particle production in neutrino neutral current interactions are presented using the data from the NOMAD experiment. Integral yields of neutral strange particles (K0s, Lambda, Lambda-bar) have been measured. Decays of resonances and heavy hyperons with an identified K0s or Lambda in the final state have been analyzed. Clear signals corresponding to K* and Sigma(1385) have been observed. First results on the measurements of the Lambda polarization in neutral current interactions have been obtained.

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arXiv2004

Bose-Einstein Correlations in Charged Current Muon-Neutrino Interactions in the NOMAD Experiment at CERN

Bose-Einstein Correlations in one and two dimensions have been studied, with high statistics, in charged current muon-neutrino interaction events collected with the NOMAD detector at CERN. In one dimension the Bose-Einstein effect has been analyzed with the Goldhaber and the Kopylov-Podgoretskii phenomenological parametrizations. The Goldhaber parametrization gives the radius of the pion emission region R_G = 1.01+/-0.05(stat)+0.09-0.06(sys) fm and for the chaoticity parameter the value lambda = 0.40+/-0.03(stat)+0.01-0.06(sys). Using the Kopylov-Podgoretskii parametrization yields R_KP = 2.07+/-0.04(stat)+0.01-0.14(sys) fm and lambda_KP = 0.29+/-0.06(stat)+0.01-0.04(sys). Different parametrizations of the long-range correlations have been also studied. The two-dimensional shape of the source has been investigated in the longitudinal co-moving frame. A significant difference between the transverse and the longitudinal dimensions is observed. The high statistics of the collected sample allowed the study of the Bose-Einstein correlations as a function of rapidity, charged particle multiplicity and hadronic energy. A weak dependence of both radius and chaoticity on multiplicity and hadronic energy is found.

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arXiv2003

Search for nu(mu)-->nu(e) Oscillations in the NOMAD Experiment

We present the results of a search for nu(mu)-->nu(e) oscillations in the NOMAD experiment at CERN. The experiment looked for the appearance of nu(e) in a predominantly nu(mu) wide-band neutrino beam at the CERN SPS. No evidence for oscillations was found. The 90% confidence limits obtained are delta m^2 < 0.4 eV^2 for maximal mixing and sin^2(2theta) < 1.4x10^{-3} for large delta m^2. This result excludes the LSND allowed region of oscillation parameters with delta m^2 > 10 eV^2.

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arXiv2003

Prediction of Neutrino Fluxes in the NOMAD Experiment

The method developed for the calculation of the flux and composition of the West Area Neutrino Beam used by NOMAD in its search for neutrino oscillations is described. The calculation is based on particle production rates computed using a recent version of FLUKA and modified to take into account the cross sections measured by the SPY and NA20 experiments. These particles are propagated through the beam line taking into account the material and magnetic fields they traverse. The neutrinos produced through their decays are tracked to the NOMAD detector. The fluxes of the four neutrino flavours at NOMAD are predicted with an uncertainty of about 8% for nu(mu) and nu(e), 10% for antinu(mu), and 12% for antinu(e). The energy-dependent uncertainty achieved on the R(e, mu) prediction needed for a nu(mu)->nu(e) oscillation search ranges from 4% to 7%, whereas the overall normalization uncertainty on this ratio is 4.2%.

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arXiv2001

Final NOMAD results on nu_mu->nu_tau and nu_e->nu_tau oscillations including a new search for nu_tau appearance using hadronic tau decays

Results from the nu_tau appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic tau decays, significantly improving the overall sensitivity of the experiment to oscillations. The "blind analysis" of all topologies yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90% C.L. allowed region in the sin^2(2theta)-Delta m^2 plane which includes sin^2(2theta)<3.3 x 10^{-4} at large Delta m^2 and Delta m^2 < 0.7 eV^2/c^4 at sin^2(2theta)=1. The corresponding contour in the nu_e->nu_tau oscillation hypothesis results in sin^2(2theta)<1.5 x 10^{-2} at large Delta m^2 and Delta m^2 < 5.9 eV^2/c^4 at sin^2(2theta)=1. We also derive limits on effective couplings of the tau lepton to nu_mu or nu_e.

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arXiv2001

Search for heavy neutrinos mixing with tau neutrinos

We report on a search for heavy neutrinos ($\nus$) produced in the decay $D_s\to τ\nus$ at the SPS proton target followed by the decay $\nudecay$ in the NOMAD detector. Both decays are expected to occur if $\nus$ is a component of $ν_τ$.\ From the analysis of the data collected during the 1996-1998 runs with $4.1\times10^{19}$ protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the $\nus$ mass range from 10 to 190 $\rm MeV$. Windows between the SN1987a and Big Bang Nucleosynthesis lower limits and our result are still open for future experimental searches. The results obtained are used to constrain an interpretation of the time anomaly observed in the KARMEN1 detector.\

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arXiv2001

Inclusive production of $ρ^{0}(770), f_0(980)$ and $f_2(1270)$ mesons in $ν_μ$ charged current interactions

The inclusive production of the meson resonances $ρ^{0}(770)$, $f_0(980)$ and $f_2(1270)$ in neutrino-nucleus charged current interactions has been studied with the NOMAD detector exposed to the wide band neutrino beam generated by 450 GeV protons at the CERN SPS. For the first time the $f_{0}(980)$ meson is observed in neutrino interactions. The statistical significance of its observation is 6 standard deviations. The presence of $f_{2}(1270)$ in neutrino interactions is reliably established. The average multiplicity of these three resonances is measured as a function of several kinematic variables. The experimental results are compared to the multiplicities obtained from a simulation based on the Lund model. In addition, the average multiplicity of $ρ^{0}(770)$ in antineutrino - nucleus interactions is measured.

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