Last Update: October 2000

NOMAD

Laboratory and beam: CERN Geneva, wide band neutrino beam

Collaboration:

6J. Altegoer 17C. Angelini15P. Astier 9D. Autiero 19A. Baldisseri 14M. Baldo-Ceolin 9G. Ballocchi 15M. Banner 10S. Basa 2G. Bassompierre 10K. Benslama 19N. Besson 10I. Bird 3B. Blumenfeld 14F. Bobisut 19J. Bouchez 20S. Boyd 4A. Bueno 7S. Bunyatov 9L. Camilleri 11A. Cardini 15A. Castera 16P. W. Cattaneo 17V. Cavasinni 9A. Cervera-Villanueva 14G. M. Collazuol 21G. Conforto 16C. Conta 14M. Contalbrigo 11R. Cousins 4D. Daniels 10H. Degaudenzi 17A. De Santo 17T. Del Prete 4T. Dignan 9L. Di Lella 9E. do Couto e Silva 20I. J. Donnelly 15J. Dumarchez 2T. Fazio 4G. J. Feldman 16R. Ferrari 9D. Ferrère 17V. Flaminio 16M. Fraternali 2J-M. Gaillard 10P. Galumian 15E. Gangler 9A. Geiser 6D. Geppert 14D. Gibin 13S. Gninenko 1J-J. Gomez-Cadenas 19J. Gosset 6C. Gößling 2M. Gouané re 9A. Grant 8G. Graziani 14A. Guglielmi 19C. Hagner 1J. Hernando 4D. Hubbard 4P. Hurst 12N. Hyett 8E. Iacopini 10C. Joseph 10F. Juget 22D. Kekez 9B. Khomenko 7M. Kirsanov 7O. Klimov 9J. Kokkonen 13A. Kovzelev 7V. Kuznetsov 14S. Lacaprara 16A. Lanza 5L. La Rotonda 14M. Laveder 17C. Lazzeroni 15A. Letessier-Selvon 15J-M. Levy 9L. Linssen 22A. Ljubicic 3J. Long 8A. Lupi 2E. Manola-Poggioli 8A. Marchionni 21F. Martelli 19X. Méchain 2J-P. Mendiburu 19J-P. Meyer 14M. Mezzetto 4S. R. Mishra 12G. F. Moorhead 2L. Mossuz 2P. Nédélec 7Yu. Nefedov 10C. Nguyen-Mau 18D. Orestano 18F. Pastore 20L. S. Peak 21E. Pennacchio 10J-P. Perroud 2H. Pessard 16R. Petti 9A. Placci 9H. Plothow-Besch 19A. Pluquet 16G. Polesello 6D. Pollmann 9B. G. Pope 7B. Popov 12C. Poulsen 19P. Rathouit 17G. Renzoni 9C. Roda 9A. Rubbia 16F. Salvatore 16D. Scannicchio 15K. Schahmaneche 6B. Schmidt 14A. Sconza 15M. Serrano 12M. E. Sevior 2D. Sillou 20F. J. P. Soler 10G. Sozzi 3D. Steele 9P. Steffen 10M. Steininger 9U. Stiegler 22M. Stipcevic 19T. Stolarczyk 10M. Tareb-Reyes 12G. N. Taylor 7S. Tereshchenko 13A. Toropin 15A-M. Touchard 12S. N. Tovey 10M-T. Tran 9E. Tsesmelis 20J. Ulrichs 15V. Uros 10L. Vacavant 5M. Valdata-Nappi 7V. Valuev 15F. Vannucci 20K. E. Varvell 21M. Veltri 16V. Vercesi 2D. Verkindt 10J-M. Vieira 11T. Vinogradova 19M-K. Vo 13S. Volkov 4F. Weber 6T. Weisse 10M. Werlen 9F. Wilson 12L. J. Winton 20B. D. Yabsley 19H. Zaccone 6K. Zuber

______________________________________

1Univ. of Massachusetts, Amherst, MA, USA 2LAPP, Annecy, France 3Johns Hopkins Univ., Baltimore, MD, USA 4Harvard Univ., Cambridge, MA, USA 5Univ. of Calabria and INFN, Cosenza, Italy 6Dortmund Univ., Dortmund, Germany 7JINR, Dubna, Russia 8Univ. of Florence and INFN, Florence, Italy 9CERN, Geneva, Switzerland 10University of Lausanne, Lausanne, Switzerland 11UCLA, Los Angeles, CA, USA 12University of Melbourne, Melbourne, Australia 13Inst. Nucl. Research, INR Moscow, Russia 14Univ. of Padova and INFN, Padova, Italy 15LPNHE, Univ. of Paris, Paris VI and VII, France 16Univ. of Pavia and INFN, Pavia, Italy 17Univ. of Pisa and INFN, Pisa, Italy 18Roma-III Univ., Rome, Italy 19DAPNIA, CEA Saclay, France 20Univ. of Sydney, Sydney, Australia 21Univ. of Urbino, Urbino, and INFN Florence, Italy 22Rudjer Boskovic Institute, Zagreb, Croatia 23Now at Perugia Univ., Perugia, Italy 24Now at UCSC, Santa Cruz, CA, USA 25Now at Univ. of Colorado, Boulder, CO, USA

1. Goal of the Experiment

> The NOMAD (Neutrino Oscillation MAgnetic Detector) experiment has been designed to search for the nm-nt oscillation, in the region of mass difference dm2 of several eV2 - a region of cosmological interest - with a sensitivity on P(nm-nt) about 2. 10-4 .

> The nt appearance in an almost pure nm beam is detected through its CC interactions and subsequent t decay. Nomad is sensitive to about 82% of the t branching ratios. To achieve the needed background rejection power of the order 105 Nomad pioneers a selection tecnique based on kinematic criteria.

> The goal of the experiment is to reach a low and consistently estimated background level while getting an high sensitivity and a robust evaluation of the selection efficiency.

> Due to the naturally suppressed ne component of the beam and to the good lepton identification and reconstruction properties of the detector, Nomad can also perform a nm-ne oscillation search with a sensitivity partially covering the parameter region allowed by the LSND experiment.

2. Physics achievements

> Nomad has collected a sample of 1.3 millions nm CC interactions on the target and has completed the analysis for the nm-nt oscillation search. The robustness and the power of the kinematic selection method has been proven. The large collected statistics of nm CC has been exploited to correct for the systematics of the MC simulation and to obtain a precise description of the backgrounds down to O(10-5) and to check the MC efficiencies. An independent check of the background predictions has been obtained with the analysis of wrong sign candidates. The possible biases due to the study of the data in the region where the signal is expected has been avoided by means of a blind analysis. The exploitation of all the observed t decay channels has allowed to obtain a final sensitivity on P(nm-nt) of 2.6 10-4 (75% of which is due to the low background bins) close to the value of the proposal. No excess has been observed over the expected background so the experiment has established a new 90%CL limit on the P(nm-nt) of 2. 10-4 .

3. INFN contribution to the experiment in terms of manpower and financial support

> - 28 physicists (16.9 FTE) and 3 technicians.

> - Financial support: 881 MLit. (1999), 565 MLit (2000) .

4. Number of publications in refereed journal: 20

5. Number of talks to conferences: 73

6. Number of undergraduate and doctoral thesis on the experiment:

> 23 (of which 12 italian) undergraduated and 31 (of which 4 italian) PhD thesis.

7. Leadership roles in the experiment

> - The spokesperson is L. Di Lella. The italian group leader is M. Baldo Ceolin.

> - The INFN groups had the responsibility for the design, realization, maintenance and exploitation of the electromagnetic calorimeter.

> - The INFN groups gave significant contribution to the analysis of both nm-nt and nm-ne oscillation and to the precise understanding of the beam composition.

8. Innovative instruments

> - A 3 ton active target made of large area (3x3 m2) and low density (r~0.1 g/cm3) drift chambers with 200 mm resolution.

> - A large area (3x3 m2) transition radiation detector allowing to reject pions to the 10-3 level with an electron identification efficiency of 90 %.

> - An omogeneous electromagnetic calorimeter with sE/E=3.2%/E1/2+1% operating inside a magnetic field.

9. Competing experiments

> Chorus experiment at the Cern wide band beam.

10. International committee which has reviewed the experiment

> The CERN SPSC and the CERN Research Board.