A hybrid experiment with nuclear emulsion and scintillating-fiber detectors (KEK-E373) has been performed to search for double-strangeness systems. Among about 10(3) events of Xi(-) hyperons captured at rest by emulsion nuclei, we have observed four events which clearly show the topology of cascade weak decays of double-Lambda hypernuclei including the "Nagara" event. Regarding the Nagara event, values of the two-Lambda binding energy (B-Lambda Lambda) and the Lambda-Lambda interaction energy (Delta B-Lambda Lambda) of He-6(Lambda Lambda) have been revised to 6.91 +/- 0.16 and 0.67 +/- 0.17 MeV, respectively, due to the recent change of the Xi(-) mass value (Particle Data Group). For another three events, we have determined possible species of double-Lambda hypernuclei together with their binding energies.

The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode through the study of $\nu_\mu\to\nu_\tau$ oscillations. The apparatus consists of an emulsion/lead target complemented by electronic detectors and it is placed in the high energy long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out in 2007 and 2008 with the detector fully operational with its related facilities for the emulsion handling and analysis. After a brief description of the beam and of the experimental setup we report on the collection, reconstruction and analysis procedures of first samples of neutrino interaction events.

The OPERA neutrino oscillation experiment has been designed to prove the appearance of ντ in a nearly pure νμ beam (CNGS) produced at CERN and detected in the underground Hall C of the Gran Sasso Laboratory, 730 km away from the source. In OPERA, τ leptons resulting from the interaction of ντ are produced in target units called bricks made of nuclear emulsion films interleaved with lead plates. The OPERA target contains 150000 of such bricks, for a total mass of 1.25 kton, arranged into walls interleaved with plastic scintillator strips. The detector is split into two identical supermodules, each supermodule containing a target section followed by a magnetic spectrometer for momentum and charge measurement of penetrating particles. Real time information from the scintillators and the spectrometers provide the identification of the bricks where the neutrino interactions occurred. The candidate bricks are extracted from the walls and, after X-ray marking and an exposure to cosmic rays for alignment, their emulsion films are developed and sent to the emulsion scanning laboratories to perform the accurate scan of the event. In this paper, we review the design and construction of the detector and of its related infrastructures, and report on some technical performances of the various components. The construction of the detector started in 2003 and it was completed in Summer 2008. The experiment is presently in the data taking phase. The whole sequence of operations has proven to be successful, from triggering to brick selection, development, scanning and event analysis.

An emulsion-counter hybrid experiment (KEK E176) was carried out to search for double strangeness systems such as double-Λ hypernuclei and H-dibaryons. More than 10% of Ξ− hyperons produced in the (K−, K+) reaction were brought to rest in the nuclear emulsion. We have obtained 98 candidate events of nuclear capture at rest of Ξ− hyperons which are described in this report. Among those, four events were identified as sequential weak decay of double-Λ hypernuclei. The binding energies of Ξ−-(12C, 14N and 16O) states have been estimated for two events which emit twin single-Λ hypernuclei back to back from the capture point. The Σ−p decay vertex of an H-dibaryon was searched for near the capture point and no evidence was observed. Upper limits for the branching ratio of H emission are 5–10% for a lifetime less than 0.1 ns at the 90% confidence level. The trapping probabilities of single and double strangeness to a nuclear fragment following Ξ− capture at rest have been studied.

New methods for efficient and unambiguous interconnection between electronic position sensitive detectors and target units based on nuclear photographic emulsion films have been developed. The application to the OPERA experiment, that aims at detecting νμ⇌ντ oscillations in the CNGS neutrino beam, is reported in this paper. In order to reduce background due to latent tracks collected before installation in the detector, on-site large-scale treatments of the emulsions (''refreshing'') have been applied. Changeable Sheet (CSd) packages, each made of a doublet of emulsion films, have been designed, assembled and coupled to the OPERA target units (''ECC bricks''). A device has been built to print X-ray spots for accurate interconnection both within the CSd and between the CSd and the related ECC brick. Sample emulsion films have been extensively scanned with state-of-the-art automated optical microscopes. Efficient track-matching and powerful background rejection have been achieved in tests with electronically tagged penetrating muons. Further improvement of in-doublet film alignment was obtained by matching the pattern of low-energy electron tracks. The commissioning of the overall OPERA alignment procedure is in progress.

We have observed 23.2±6.0 −0.9 purely-leptonic decays of D + s → μ νμ from a sample of muonic one prong decay events detected in the emulsion target of Fermilab experiment E653. Using the D+ s → φμ νμ yield measured previously in this experiment, we obtain B(D+ s → μ νμ)/B(D + s → φμ νμ) = 0.16 ± 0.06 ± 0.03. In addition, we extract the decay constant fDs = 194 ± 35 ± 20 ± 14 MeV . 1) Aichi University of Education, Kariya 448, JAPAN 2) University of California (Davis), Davis, CA 95616, USA

The final oscillation analysis of the complete set of data collected by CHORUS in the years 1994-1997 is presented. Reconstruction algorithms of data extracted by electronic detectors were improved and the data recorded in the emulsion target were analysed by new automated scanning systems, allowing the use of a new method for event reconstruction in emulsion. CHORUS has applied these new techniques to the sample of 1996-1997 events for which no muons were observed in the electronic detectors. Combining the new sample with the data analysed in previous papers, the overall sensitivity of the experiment to the nu(tau) appearance is thus improved. In a two-neutrino mixing scheme, a 90% C.L. upper limit of sin(2)2 theta(mu tau) < 4.4 x 10(-4) is set for large Delta m(2), improving by a factor 1.5 the previously published CHORUS result. (C) 2007 Elsevier B.V. All rights reserved.

The OPERA neutrino oscillation experiment is based on the use of the Emulsion Cloud Chamber (ECC). In the OPERA ECC, nuclear emulsion films acting as very high precision tracking detectors are interleaved with lead plates providing a massive target for neutrino interactions. We report on studies related to the effects occurring from the contact between emulsion and lead. A low radioactivity lead is required in order to minimize the number of background tracks in emulsions and to achieve the required performance in the reconstruction of neutrino events. It was observed that adding other chemical elements to the lead, in order to improve the mechanical properties, may significantly increase the level of radioactivity on the emulsions. A detailed study was made in order to choose a lead alloy with good mechanical properties and an appropriate packing technique so as to have a low enough effective radioactivity.

We present a leading order QCD analysis of a sample of neutrino induced charged-current events with two muons in the final state originating in the lead-scintillating fibre calorimeter of the CHORUS detector. The results are based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign dimuon events collected during the exposure of the detector to the CERN Wide Band Neutrino Beam between 1995 and 1998. The analysis yields a value of the charm quark mass of m(c) = (1.26 +/- 0.16 +/- 0.09) GeV/c(2) and a value of the ratio of the strange to non-strange sea in the nucleon Of K = 0.33 +/- 0.05 +/- 0.05, improving the results obtained in similar analyses by previous experiments. (c) 2008 Elsevier B.V. All rights reserved.

The DONuT experiment collected data in 1997 and published first results in 2000 based on four observed v(tau) charged-current (CC) interactions. The final analysis of the data collected in the experiment is presented in this paper, based on 3.6 x 10(17) protons on target using the 800 GeV Tevatron beam at Fermilab. The number of observed v(tau) CC events is 9 with an estimated background of 1.5 events, from a total of 578 observed neutrino interactions. We calculate the v(tau) CC cross section as a function of one parameter. Assuming D-s mesons are the sole source for v(tau), the energy-independent part of the total CC cross section can be parametrized as sigma(const)(v(tau)) = 2.51n(1.52) x 10(-40) cm(2) GeV-1 for n >= 4, where n is the parameter controlling the longitudinal part of the Ds differential cross section of the form d sigma/dx(F) proportional to (1-vertical bar x(F)vertical bar)(n). The analysis could not distinguish between v(tau) and (v) over bar (tau). The value of n obtained from PYTHIA simulations, n = 6.1, gives an estimated value of sigma(const)(v(tau))= (0.39 +/- 0.13 +/- 0.13) x 10(-38) cm(2) GeV-1.

A. Anokhina, w S. Aoki, q A. Ariga, y,∗ L. Arrabito, s D. Autiero, s A. Badertscher, al F. Bay,a F. Bersani Greggio, ai A. Bertolin, ad M. Besnier, b D. Bick, n C. Bozza,ag T. Brugiere, s R. Brugnera, ae G. Brunetti, h S. Buontempo, z E. Carrara, ae A. Cazes,k L. Chaussard, s M. Chernyavsky, v V. Chiarella, k N. Chon-Sen, ah A. Chukanov, z L. Consiglio, h M. Cozzi,h V. Cuha,a F. Dal Corso, ad G. D’Amato, ag N. D’Ambrosio, c G. De Lellis, aa Y. Déclais, s M. De Serio, e F. Di Capua, z D. Di Ferdinando, g A. Di Giovanni, r N. Di Marco, r C. Di Troia, k S. Dmitrievski, j A. Dominjon, s M. Dracos, ah D. Duchesneau, b S. Dusini, ad J. Ebert, n O. Egorov, u R. Enikeev, t A. Ereditato, f L.S. Esposito, c J. Favier, b G. Felici, k T. Ferber, n R. Fini, e D. Frekers, x T. Fukuda, y V.I. Galkin, w V.A. Galkin, ac A. Garfagnini, ae G. Giacomelli, h M. Giorgini, h C. Goellnitz, n J. Goldberg, m D. Golubkov, u Y. Gornushkin, j G. Grella, ag F. Grianti, ai M. Guler, a G. Gusev, v C. Gustavino, c C. Hagner, n T. Hara,q M. Hierholzer, n S. Hiramatsu, y K. Hoshino, y M. Ieva,e K. Jakovcic, ak J. Janicsko Csathy, ab B. Janutta, n C. Jollet, ah F. Juget, ab T. Kawai, y M. Kazuyama, y S. H. Kim, o,1 J. Knuesel, f K. Kodama, p M. Komatsu, y U. Kose, a I. Kreslo, f I. Laktineh, s C. Lazzaro, al J. Lenkeit, n A. Ljubicic, ak A. Longhin, ad G. Lutter, ab K. Manai, s G. Mandrioli, g A. Marotta, z J. Marteau, s T. Matsuo, l H. Matsuoka, y N. Mauri, h F. Meisel, ab A. Meregaglia, ah M. Messina, f P. Migliozzi, z S. Mikado, l ,2 S. Miyamoto, y P. Monacelli, r K. Morishima, y U. Moser, f M.T. Muciaccia, d N. Naganawa, y T. Naka,y M. Nakamura, y T. Nakamura, y T. Nakano, y V. Nikitina, w K. Niwa, y Y. Nonoyama, y S. Ogawa, l V. Osedlo, w D. Ossetski, ac A. Paoloni, k B.D. Park, o I.G. Park,o A. Pastore, d L. Patrizii, g E. Pennacchio, s H. Pessard, b V. Pilipenko, x C. Pistillo, f N. Polukhina, v M. Pozzato, h K. Pretzl, f P. Publichenko, w F. Pupilli, r T. Roganova, w G. Rosa,a f I. Rostovtseva, u A. Rubbia, al A. Russo, z O. Ryazhskaya, t D. Ryzhikov, ac O. Sato,y Y. Sato,a j V. Saveliev, ac G. Sazhina, w A. Schembri, c L. Scotto Lavina, z H. Shibuya, l S. Simone, d M. Sioli, h C. Sirignano, ag G. Sirri, g J. S. Song, o M. Spinetti, k L. Stanco, ad N. Starkov, v M. Stipcevic, ak T. Strauss, al P. Strolin, aa V. Sugonyaev, ad Y. Taira,y S. Takahashi, y M. Tenti, h F. Terranova, k I. Tezuka,a j V. Tioukov, z P. Tolun, a V. Tsarev, v S. Tufanli, a N. Ushida, p P. Vilain, i M. Vladimirov, v L. Votano, k J.L. Vuilleumier, ab G. Wilquet, i B. Wonsak, n C. S. Yoon, o J. Yoshida, y Y. Zaitsev, u S. Zemskova, j A. Zghiche b and R. Zimmermann n

In this paper a search for associated charm production both in neutral and charged current $\nu$-nucleus interactions is presented. The improvement of automatic scanning systems in the {CHORUS} experiment allows an efficient search to be performed in emulsion for short-lived particles. Hence a search for rare processes, like the associated charm production, becomes possible through the observation of the double charm-decay topology with a very low background. About 130,000 $\nu$ interactions located in the emulsion target have been analysed. Three events with two charm decays have been observed in the neutral-current sample with an estimated background of 0.18$\pm$0.05. The relative rate of the associated charm cross-section in deep inelastic $\nu$ interactions, $\sigma(c\bar{c}\nu)/\sigma_\mathrm{NC}^\mathrm{DIS}= (3.62^{+2.95}_{-2.42}({stat})\pm 0.54({syst}))\times 10^{-3}$ has been measured. One event with two charm decays has been observed in charged-current $\nu_\mu$ interactions with an estimated background of 0.18$\pm$0.06 and the upper limit on associated charm production in charged-current interactions at 90% C.L. has been found to be $\sigma (c\bar{c} \mu^-)/\sigma_\mathrm{CC} < 9.69 \times 10^{-4}$.

. An event emitting a Σ - -hyperon from a Ξ - -hyperon nuclear capture at rest has been observed in a hybrid-emulsion experiment. The event has been analyzed as the first observation of the weak decay of the S = - 2 system.

The DONuT experiment collected data in 1997 and published first results in 2000 based on four observed {nu}{sub {tau}} charged-current (CC) interactions. The final analysis of the data collected in the experiment is presented in this paper, based on 3.6 x 10{sup 17} protons on target using the 800 GeV Tevatron beam at Fermilab. The number of observed {nu}{sub {tau}} CC interactions is 9, from a total of 578 observed neutrino interactions. We calculated the energy-independent part of the tau-neutrino CC cross section ({nu} + {bar {nu}}), relative to the well-known {nu}{sub e} and {nu}{sub {mu}} cross sections. The ratio {sigma}({nu}{sub {tau}})/{sigma}({nu}{sub e,{mu}}) was found to be 1.37 {+-} 0.35 {+-} 0.77. The {nu}{sub {tau}} CC cross section was found to be 0.72 {+-} 0.24 {+-} 0.36 x 10{sup -38} cm{sup 2} GeV{sup -1}. Both results are in agreement with expectations from the Standard Model.

The CHORUS experiment, designed to search for νμ→ντ oscillations, consists of a nuclear emulsion target and electronic detectors. In this paper, results on the production of charged particles in a small sample of charged-current neutrino– and anti-neutrino–nucleus interactions at high energy are presented. For each event, the emission angle and the ionization features of the charged particles produced in the interaction are recorded, while the standard kinematic variables are reconstructed using the electronic detectors. The average multiplicities for charged tracks, the pseudo-rapidity distributions, the dispersion in the multiplicity of charged particles and the KNO scaling are studied in different kinematical regions. A study of quasi-elastic topologies performed for the first time in nuclear emulsions is also reported. The results are presented in a form suitable for use in the validation of Monte Carlo generators of neutrino–nucleus interactions.

After completion of the data taking for the v(mu) -> v(tau) oscillation search, the CHORUS lead-scintillator calorimeter was used in the 1998 run as an active target. High-statistics samples of charged-current interactions were collected in the CERN SPS west area neutrino beam. This beam contained predominantly muon (anti-)neutrinos from sign-selected pious and kaons. We measure the flux and energy spectrum of the incident neutrinos and compare them with beam simulations. The neutrino-nucleon and anti-neutrino-nucleon differential cross-sections are measured in the range 0.01 < x < 0.7, 0.05 < y < 0.95, 10 < E-v < 200 GeV. We extract the neutrino-nucleon structure functions F-2(x, Q(2)), xF(3) (x, Q(2)), and R(x, Q2) and compare these with results from other experiments. (c) 2005 Elsevier B.V. All rights reserved.

The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode, through the study of nu_mu to nu_tau oscillations. The apparatus consists of a lead/emulsion-film target complemented by electronic detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. In August 2006 a first run with CNGS neutrinos was successfully conducted. A first sample of neutrino events was collected, statistically consistent with the integrated beam intensity. After a brief description of the beam and of the various sub-detectors, we report on the achievement of this milestone, presenting the first data and some analysis results.

A systematic search for superfragments (charmed nuclei) has been performed in 22 200 neutrinoemulsion interactions obtained with the CHORUS experiment making use of automatic off-line image analysis. The absence of candidates provides an upper limit for the superfragment production rate of 1.9 x 10(-4) (90% C.L.) relative to neutrino charged-current interactions at an average neutrino energy of 27 GeV. In the same analysis 28 hyperfragment decays were found. For the first time, a production rate of hyperfragments in neutrino-emulsion interactions was obtained. The value of the hyperfragment production rate relative to the neutrino charged-current cross-section was found to be (2.0 +/- 0.4(stat) +/- 0.3 (syst)) x 10(-3). (c) 2005 Elsevier B.V. All rights reserved.

During the years 1994-1997, the emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy. In total about 100 000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. From this sample of events which was based on the data acquired by new automatic scanning systems, 1048 charged-current interactions with a Do in the final state were selected by a pattern recognition program and confirmed as neutral-particle decays through visual inspection. The ratio of decay branching fractions of the Do into four charged particles to two charged particles was measured to be B(D-0 -> V4)/B(D-0 -> V2) = 0.207 +/- 0.016 +/- 0.004. The inclusive measurement of the observed production rate of the Do with a decay into four charged prongs in combination with external measurements of this topological branching ratio was used to determine the total Do production rate by neutrinos without additional assumption on the branching fractions. The value of this rate relative to the charged-current cross-section was found to be sigma (D-0) / sigma (CC) = 0.0269 +/- 0.0018 +/- 0.0013. In addition, the same normalization method was used to deduce the inclusive topological decay rate into final states with neutral particles only. A value of 0.218 +/- 0.049 +/- 0.036 was found for this branching fraction. From an observed number of three charged six-prong events the branching ratio into six charged particles was determined to be (1.2(-0.9)(+1.3) +/- 0.2) x 10(-3). A measurement of the energy dependence of the D-0 production by neutrinos relative to the total charged-current cross-section is also reported. This measurement was used to deduce for m(c), the effective charm-quark mass, a value of (1.42 +/- 0.08) GeV/c(2). (c) 2005 Elsevier B.V. All rights reserved.

From 1994 to 1997, the emulsion target of the CHORUS detector was exposed to the wideband neutrino beam of the CERN SPS. In total about 100 000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. From this sample of events based on the data acquired by new automatic scanning systems; 2013 charm-decay events were selected by a pattern recognition program. They were confirmed as decays through visual inspection. Based on these events, the effective branching ratio of charmed particles into muons was determined to be (B) over bar (mu) = [7.3 +/- 0.8(stat) +/- 0.2(syst)] x 10(-2). In addition, the muonic branching ratios are presented for dominating charm-decay topologies. Normalization of the muonic decays to charged-current interactions provides sigma(mu)-(mu)+/sigma(cc) = [3.16 +/- 0.34(stat) 0.09(syst)] x 10(-3). Selecting only events with visible energy greater than 30 GeV gives a value of (B) over bar (mu) that is less affected by the charm production threshold and quasi-elastic Delta(+)(c) production. Combining this value with the current average of B 12 of vertical bar V-cd vertical bar(LO) = 0. 236 +/- 0.016. (c) 2005 Elsevier B.V. All rights reserved.