0000000000177037
AUTHOR
Anselmo Cervera Villanueva
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 Deltam(2) < 0.4 eV(2) for maximal mixing and sin(2) (20) < 1.4 x 10(-3) for large Deltam(2). This result excludes the LSND allowed region of oscillation parameters with Deltam(2) greater than or similar to 10 eV(2).
Measurement of the quasi-elastic axial vector mass in neutrino-oxygen interactions
The weak nucleon axial-vector form factor for quasielastic interactions is determined using neutrino interaction data from the K2K Scintillating Fiber detector in the neutrino beam at KEK. More than 12 000 events are analyzed, of which half are charged-current quasielastic interactions nu(mu)n ->mu(-)p occurring primarily in oxygen nuclei. We use a relativistic Fermi gas model for oxygen and assume the form factor is approximately a dipole with one parameter, the axial-vector mass M-A, and fit to the shape of the distribution of the square of the momentum transfer from the nucleon to the nucleus. Our best fit result for M-A=1.20 +/- 0.12 GeV. Furthermore, this analysis includes updated vect…
Forward pi(+/-) production in p-O-2 and p-N-2 interactions at 12 GeV/c
Measurements of double-differential charged pion production cross-sections in interactions of 12 GeV/c protons on O-2 and N-2 thin targets are presented in the kinematic range 0.5 GeV/c <= p(pi) < 8 GeV/c and 50 mrad <= 0(pi) < 250 mrad (in the laboratory frame) and are compared with p-C results. For p-N-2 (p-O-2) interactions the analysis is performed using 38576 (7522) reconstructed secondary pions. The analysis uses the beam instrumentation and the forward spectrometer of the HARP experiment at CERN PS. The measured cross-sections have a direct impact on the precise calculation of atmospheric neutrino fluxes and on the improved reliability of extensive air shower simulations by reducing …
Measurement of the Lambda polarization in nu(mu) charged current interactions in the NOMAD experiment
The Lambda polarization in upsilon (mu) charged current interactions has been measured in the NOMAD experiment. The event sample (8087 reconstructed Lambda 's) is more than an order of magnitude larger than that of previous bubble chamber experiments, while the quality of event reconstruction is comparable. We observe negative polarization along the W-boson direction which is enhanced in the target fragmentation region: P-x(x(F) 0) = -0.09 +/- 0.06(stat) +/- 0.03(sys). These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization tin the direction orthogonal to the Lambda production plane! has…
Characterisation of NEXT-DEMO using xenon K-alpha X-rays
The NEXT experiment aims to observe the neutrinoless double beta decay of 136Xe in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ion- ization. Understanding the response of the detector is imperative in achieving a consistent and well understood energy measurement. The abundance of xenon K-shell X-ray emission during data tak- ing has been identified as a multitool for the characterisation of the fundamental parameters of the gas as well as the equalisation of the response of the detector. The NEXT-DEMO prototype is a ∼ 1.5 kg volume TPC filled with natural xenon. It employs an array of 19 PMTs as an energy plane and of 256 SiPMs as a tracking plane…
A study of backward going protons and negative pions in Numu CC interactions with the NOMAD detector
Backward proton and π− production has been studied in νμCC interactions with carbon nuclei. Detailed analyses of the momentum distributions, of the production rates, and of the general features of events with a backward going particle, have been carried out in order to understand the mechanism producing these particles. The backward proton data have been compared with the predictions of the reinteraction and the short range correlation models.
Measurement of the Antilambda Polarisation in Nu(mu) Charged Current Interactions in the NOMAD Experiment
We present a measurement of the polarization of Antilambda hyperons produced in nu_mu charged current interactions. The full data sample from the NOMAD experiment has been analyzed using the same V0 identification procedure and analysis method reported in a previous paper for the case of Lambda hyperons. The Antilambda polarization has been measured for the first time in a neutrino experiment. The polarization vector is found to be compatible with zero.
Near-intrinsic energy resolution for 30-662 keV gamma rays in a high pressure xenon electroluminescent TPC
We present the design, data and results from the NEXT prototype for Double Beta and Dark Matter (NEXT-DBDM) detector, a high-pressure gaseous natural xenon electroluminescent time projection chamber (TPC) that was built at the Lawrence Berkeley National Laboratory. It is a prototype of the planned NEXT-100 Xe-136 neutrino-less double beta decay (0 nu beta beta) experiment with the main objectives of demonstrating near-intrinsic energy resolution at energies up to 662 keV and of optimizing the NEXT-100 detector design and operating parameters. Energy resolutions of similar to 1% FWHM for 662 keV gamma rays were obtained at 10 and 15 atm and similar to 5% FWHM for 30 keV fluorescence xenon X-…
A precise measurement of the muon neutrino nucleon inclusive charged current cross section off an isoscalar target in the energy range 2.5<E<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 <= E-v <= 40 GeV. The significance of this measurement is its precision, +/- 4% in 2.5 <= E-v <= 10 GeV, and +/- 2.6% in 10 <= E-v <= 40 GeV regions, where significant uncertainties in previous experiments still exist, and its importance to the current and proposed long baseline neutrino oscillation experiments.
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 v, 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% CL allowed region in the sin(2)2 theta (mu tau)-Deltam(2) plane which includes sin(2)2 theta (mu tau) nu (tau) oscillation hypothesis results in sin(2) 2 theta (l tau) < 1.5 x 10(-2) at large Deltam(2) and Deltam(2) < 5.9 eV(2)/c(4) at sin(2) 2 theta (l tau) = 1. We also derive limits on effective couplings of the tau…
Measurement of the production cross-sections of pi(+/-) in p-C and pi(+/-)-C interactions at 12 GeV/c
The results of the measurements of the double-differential production cross-sections of pions, d(2)sigma(pi)/dpd Omega, in p-C and pi(+/-)-C interactions using the forward spectrometer of the HARP experiment are presented. The incident particles are 12 GeV/c protons and charged pions directed onto a carbon target with a thickness of 5% of a nuclear interaction length. For p-C interactions the analysis is performed using 100,035 reconstructed secondary tracks, while the corresponding numbers of tracks for pi(-)-C and pi(+)-C analyses are 106,534 and 10,122, respectively. Cross-section results are presented in the kinematic range 0.5 GeV/c <= p(pi) < 8 GeV/c and 30 mrad <= theta(pi) < 240 mra…
Precision measurement of scaled momentum, charge multiplicity, and thrust in nu N-mu and (nu)over-bar(mu)N interactions
We report the first precision measurements of the scaled momentum, the charge multiplicity, and the thrust of hadronic jets in the Breit frame in Deep Inelastic Scattering nu(mu)N and charged cur rent events over the Q(2) range from 1 to 100 GeV2. The neutrino data, obtained in the NOMAD experiment at the CERN SPS, extend the Q(2)-evolution of these parameters by two orders of magnitude, and with commensurate precision, when compared to those reported by the ep and e(+)e(-) experiments
Experimental study of the atmospheric neutrino backgrounds for p -> e(+)pi(0) searches in water Cherenkov detectors
The atmospheric neutrino background for proton decay via p -> e(+)pi(0) in ring imaging water Cherenkov detectors is studied with an artificial accelerator neutrino beam for the first time. In total, 3.14x10(5) neutrino events corresponding to about 10 megaton-years of atmospheric neutrino interactions were collected by a 1000 ton water Cherenkov detector (KT). The KT charged-current single pi(0) production data are well reproduced by simulation programs of neutrino and secondary hadronic interactions used in the Super-Kamiokande (SK) proton decay search. The obtained p -> e(+)pi(0) background rate by the KT data for SK from the atmospheric neutrinos whose energies are below 3 GeV is 1.63(-…
A more sensitive search for nu(mu) -> nu(tau) oscillations in NOMAD
With additional data and improved algorithms, we have enhanced the sensitivity of our appearance search for nu(mu) --> nu(tau) oscillations in the NOMAD detector in the CERN-SPS wide-band neutrino beam. The search uses kinematic criteria to identify nu(tau) charged current interactions followed by decay of the tau(-) to one of several decay modes. Our 'blind'' analyses of deep-inelastic scattering data taken in 1996 and 1997, combined with consistent reanalyses of previously reported 1995 data, yield no oscillation signal. For the two-family oscillation scenario, we present the contour outlining a 90% C.L. confidence region in the sin(2)2 theta(mu tau) - Delta m(2) plane. At large Delta m(2…
Limit on nu(e) -> nu(tau) oscillations from the NOMAD experiment
In the context of a two-flavour approximation we reinterpret the published NOMAD limit on νμ→ντ oscillations in terms of νe→ντ oscillations. At 90% C.L. we obtain Full-size image (<1 K) for large Δm2, while for sin22θeτ=1 the confidence region includes Δm2<11 eV2/c4.
Measurement of the production cross-section of positive pions in p-Al collisions at 12.9 GeV/c
A precision measurement of the double-differential production cross-section, d(2)sigma(pi+)/dpd Omega for pions of positive charge. performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV/c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 to 6.5 GeV/c. and within an angular range from 30 mrad to 2 10 mrad. The absolute normaliza…
Improved search for nu(mu)->nu(e) oscillation in a long-baseline accelerator experiment
We performed an improved search for nu(mu)->nu(e) oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2x10(19) protons on target. No evidence for a nu(e) appearance signal was found, and we set bounds on the nu(mu)->nu(e) oscillation parameters. At Delta m(2)=2.8x10(-3) eV(2), the best-fit value of the K2K nu(mu) disappearance analysis, we set an upper limit of sin(2)2 theta(mu e)< 0.13 at a 90% confidence level.