Publications (38)0 Total impact
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I. Bird,
B Blumenfeld, [......],
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
R Zei,
K Zuber,
P. Zuccon
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ABSTRACT: 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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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I. Bird,
B Blumenfeld, [......],
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon,
E do Couto e Silva
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ABSTRACT: 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) < 1.4 X 10^-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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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I. Bird,
B Blumenfeld, [......],
J M Vieira,
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: A study of strange particle production in $\nu_\mu$ charged current interactions has been performed using the data from the NOMAD experiment. Yields of neutral strange particles ($\ko$, $\lam$, $\alam$) have been measured. Mean multiplicities are reported as a function of the event kinematic variables $E_\nu$, $W^2$ and $Q^2$ as well as of the variables describing particle behaviour within a hadronic jet: $x_F$, $z$ and $p_T^2$. Decays of resonances and heavy hyperons with identified $\ko$ and $\lam$ in the final state have been analyzed. Clear signals corresponding to $\rm {K^\star}^\pm$ $\rm {\Sigma^\star}^\pm$, $\rm \Xi^-$ and $\rm \Sigma^0$ have been observed.
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I G Bird, [......],
M K Vo,
S Volkov,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: With additional data and improved algorithms, we have enhanced the sensitivity of our appearance search for $\numunutau$ oscillations in the NOMAD detector in the CERN-SPS wide-band neutrino beam. The search uses kinematic criteria to identify $\nutau$ 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 $\sin^22\theta_{\mu \tau} - \Delta m^2$ plane. At large $\Delta m^2$, the confidence region includes $\sin^22\theta_{\mu\tau}\ <\ 1.2\times10^{-3}$ (a limit 3.5 times more stringent than in our previous publication), while at $\sin^22\theta_{\mu \tau}=1$, the confidence region includes $\Delta m^2 < 1.2$ eV$^2$/$c^4$.
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J. Altegoer,
C Angelini, Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner,
S. Basa,
Gabriel Bassompierre, [......],
S Volkov,
F. Weber,
T. Weisse,
M Werlen,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: We report the first precision measurements of the scaledmomentum, the charge multiplicity, and the thrust of hadronic jets inthe Breit frame in Deep Inelastic Scattering \nun\ and\nunbar\ charged current events over the $Q^2$ range from 1 to 100 \GeVsq\ . Theneutrino data, obtained in the NOMAD experiment at the CERN SPS, extend the $Q^2$-evolution ofthese parametersby two orders of magnitude, and with commensurate precision, whencompared to those reported by the \ep\ and \ee\ experiments.
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I G Bird, [......],
J M Vieira,
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: Updated results from the appearance searches for $\numunutau$ and $\nuenutau$ oscillations in the full NOMAD data sample are reported. The increased data and the use of more refined kinematic schemes for the $\nutau$ CC selection allow a significant improvement of the overall sensitivity. The ``blind analysis" of both the deep-inelastic and the low multiplicity samples yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90\% C.L. region in the $\sin^22\theta_{\mu\tau} - \Delta m^2$ plane which includes $\sin^22\theta_{\mu\tau}\ <\ 4.4\times10^{-4}$ at large $\Delta m^2$ and $\Delta m^2 < 0.8$ eV$^2$/$c^4$ at $\sin^22\theta_{\mu \tau}=1$. The corresponding contour in the $\nuenutau$ oscillation hypothesis results in $\sin^22\theta_{e\tau}\ <\ 2.2\times10^{-2}$ at large $\Delta m^2$ and $\Delta m^2 < 6.5$ eV$^2$/$c^4$ at $\sin^22\theta_{e \tau}=1$.
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J. Altegoer, Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner,
S. Basa,
Gabriel Bassompierre,
K. Benslama, [......],
M K Vo,
S Volkov,
F. Weber,
T. Weisse,
M Werlen,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber
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ABSTRACT: A search was made for a new light gauge boson $X$ which might be produced in $\pi^{0}\rightarrow\gamma + X$ decay from neutral pions generated by 450-GeV protons in the CERN SPS neutrino target. Th e X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of $X \rightarrow\pi^{0}$ conversion in the external Coulomb field of a nucleus.\ With $1.45\times10^{18}$ protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data.\ This number is in agreement with the e xpectation of 18.1$\pm$2.8 background events from standard neutrino processes.\ A new 90 $\% ~C.L.$ upper limit on the branching ratio $Br(\pi^{0}\rightarrow\gamma + X)<$ (3.3~to~1.9)$\times10^{-5}$ for $X$ masses ranging from 0 to 120 MeV/c$^{2}$ is obtained.
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J. Altegoer,
C Angelini, Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner,
S. Basa,
Gabriel Bassompierre, [......],
M K Vo,
S Volkov,
F V Weber,
T. Weisse,
M Werlen,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber
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ABSTRACT: NOMAD is a neutrino oscillation experiment designed to search for $\nu_\tau$ appearance in the CERN-SPS wide band $\nu_\mu$ beam. Signal detection relies on the identification of $\nu_\tau$ charge d current interactions using kinematic criteria. The analysis of the 1995 data sample yields no oscillation signal. Combining all studied $\tau$ decay modes, a limit of $\sin^22\theta_{\mu \tau}~< ~4.2\times10^{-3}$ is obtained for large $\Delta m^2$ at the 90\% confidence level.
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
M Banner,
Gabriel Bassompierre,
N Besson,
I. Bird,
B Blumenfeld,
F. Bobisut, [......],
J M Vieira,
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: We present a measurement of the polarization of $\alam$ hyperons produced in $\nu_\mu$ charged current interactions. The full data sample from the NOMAD experiment has been analyzed using the same $\vo$ identification procedure and analysis method reported in a previous paper~\cite{NOMAD-polar} for the case of $\lam$ hyperons. The $\alam$ polarization has been measured for the first time in a neutrino experiment. The polarization vector is found to be compatible with zero.
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I. Bird,
B Blumenfeld, [......],
J M Vieira,
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: 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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D V Naumov,
A. Chukanov,
E Naumova,
B. Popov, Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
M Banner,
G Bassompierre, [......],
J M Vieira,
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: 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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O. Samoylov, Pierre Astier,
D. Autiero,
Alberto Baldisseri,
M. Baldo-Ceolin,
M Banner,
G Bassompierre,
K. Benslama,
N Besson,
I. Bird, [......],
J M Vieira,
T. Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: A search for exotic Theta baryon via Theta -> proton +Ks decay mode in the NOMAD muon neutrino DIS data is reported. The special background generation procedure was developed. The proton identification criteria are tuned to maximize the sensitivity to the Theta signal as a function of xF which allows to study the Theta production mechanism. We do not observe any evidence for the Theta state in the NOMAD data. We provide an upper limit on Theta production rate at 90% CL as 2.13 per 1000 of neutrino interactions.
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I. Bird, [......],
T G Vinogradova,
M K Vo,
F. Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: The NOMAD Collaboration presents a study of opposite sign dimuon events in the framework of Leading Order QCD. A total of 2714 neutrino- and 115 antineutrino-induced opposite sign dimuon events with $E_{\mu 1}, E_{\mu 2} > 4.5$ GeV, $15 < E_{\nu} < 300$ GeV and $Q^{2} > 1\;(\mbox{GeV}/\mbox{c})^{2}$ are observed %in the data from the 1995 and 1996 runs. in the Front-Calorimeter of NOMAD during the 1995 and 1996 runs. The analysis yields a value for the charm quark mass of $m_{c} = 1.3^{+0.3\;+0.3}_{-0.3\;-0.3}\;\mbox{GeV}/\m box{c}^{2}$ and for the average semileptonic branching ratio of $B_{c} = 0.095^{+0.007\;+0.014}_{-0.007\;-0.013}$. The ratio of the strange to non-strange sea in the nucleon is measured to be $\kappa = 0.48^{+0.09 +0.17}_{-0.07 -0.12}$. The measured rate of charm-induced dimuon relative to single muon, as a function of neutrino energy, is consistent with the slow rescaling hypothesis of heavy quark production.
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A. Chukanov,
D Naumov,
B. Popov, Pierre Astier,
D. Autiero,
Alberto Baldisseri,
M. Baldo-Ceolin,
M Banner,
G Bassompierre,
K. Benslama, [......],
T. Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
R Zei,
K Zuber,
P. Zuccon
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ABSTRACT: 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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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I. Bird,
B Blumenfeld, [......],
J M Vieira,
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: A search was made among $\nu_\mu$ charged current events collected in the NOMAD experiment for the reaction: $\nu_\mu + N \rightarrow \mu^- + D^{\star+} + hadrons \hookrightarrow D^0 + \pi^+ \hookrightarrow K^- + \pi^+ A $D^{\star+}$ sample composed of 47 events, with 90% purity, was extracted. The $D^{\star+}$ yield in $\nu_\mu$ charged current interactions was measured to be $T = (0.99 \pm 0.15(stat.) \pm 0.11(syst.))$%. The mean fraction of the hadronic jet energy taken by the $D^{\star+}$ is $0.67 \pm 0.02(stat) \pm 0.02(syst.)$. The distributions of the fragmentation variables $z$, ${P_{T}}^2$ and $x_F$ for $D^{\star+}$ are also presented.
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I G Bird, [......],
J M Vieira,
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
M Banner,
G Bassompierre,
K. Benslama,
N Besson,
I. Bird,
B Blumenfeld, [......],
J M Vieira,
T G Vinogradova,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
K Zuber,
P. Zuccon
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ABSTRACT: A study of strange particle production in muon neutrino charged current interactions has been performed using the data from the NOMAD experiment. Yields of neutral strange particles K0s, Lambda, AntiLambda have been measured. Mean multiplicities are reported as a function of the event kinematic variables Enu, W2 and Q2 as well as of the variables describing particle behaviour within a hadronic jet: xF, z and pT2. Decays of resonances and heavy hyperons with identified K0s and Lambda in the final state have been analyzed. Clear signals corresponding to K*+-, Sigma*+-, Xi- and Sigma0 have been observed.
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J. Altegoer,
M G Anfreville,
C Angelini, Pierre Astier,
M. Authier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner, [......],
M K Vo,
S Volkov,
F. Weber,
T. Weisse,
M Werlen,
P Wicht,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone
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ABSTRACT: The NOMAD experiment is a short base-line search for $\nu_{\mu}\rightarrow \nu_{\tau}$ oscillations in the CERN neutrino beam. The $\nu_{\tau}$'s are searched for through their charged-current interactions followed by the observation of the resulting $\tau^{-}$ through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation detectors, and the veto and trigger scintillation counters. The beam and data acquisition system are also described. The quality of the reconstruction of individual particles is demonstrated through the ability of NOMAD to observe K$^0_{\rm s}$'s, $\Lambda^0$'s and $\pi^0$'s. Finally, the observation of $\tau^{-}$ through its electronic decay being one of the most promising channels in the search, the identification of electrons in NOMAD is discussed.
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Pierre Astier,
D. Autiero,
Alberto Baldisseri,
Massimilla Baldo-Ceolin,
G. Ballocchi,
M Banner,
Gabriel Bassompierre,
K. Benslama,
N Besson,
I G Bird, [......],
S A. Volkov,
F V Weber,
T. Weisse,
F F Wilson,
L J Winton,
B. D. Yabsley,
Henri Zaccone,
Konstantin Zioutas,
K Zuber,
P. Zuccon
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ABSTRACT: We carried out a model-independent search for light scalar or pseudoscalar particles $a$'s (an example of which is the axion) that couple to two photons by using a photon-regeneration method at high energies allowing a substantial increase in the sensitivity to $eV$ masses.\ The experimental set-up is based on elements of the CERN West Area Neutrino Facility (WANF) beam line and theNOMAD neutrino detector.\ The new particles, if they exist, could be produced through the Primakoff effect in interactions of high energy photons, generated by the 450 $GeV$ protons in the CERN SPS neutrino target, with virtual photons from the WANF horn magnetic field.\ The particles would penetrate the downstream shieldingand would be observed in the NOMAD neutrino detector through their re-conversion into real high energy photons byinteracting with the virtual photons from the magnetic field of the NOMAD dipole magnet.\ From the analysis of the data collected during the 1996 run with $1.08\times10^{19}$ protons on target, 312 candidate events with energy between 5 and 140 $GeV$ were found.\ This number is in general agreement with the expectation of 272$\pm$18 background events from standard neutrino processes.\ A 90 $\% ~CL$ upper limit on the $a\gamma\gamma$-coupling $g_{a\gamma\gamma} <$ 1.5$\times10^{-4}~GeV^{ -1}$ for $a$ masses up to 40 $eV$ is obtained.\
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