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Measurement of the $\Lambda$ polarization in $\nu_\mu$ charged current interactions in the NOMAD experiment (2000) |
- Astier, Pierre,
- Autiero, D,
- Baldisseri, Alberto,
- Baldo-Ceolin, Massimilla,
- Banner, M,
- Bassompierre, Gabriel,
- Benslama, K,
- Besson, N,
- Bird, I,
- Blumenfeld, B,
- Bobisut, F,
- Bouchez, J,
- Boyd, S,
- Bueno, A G,
- Bunyatov, S A,
- Camilleri, L L,
- Cardini, A,
- Cattaneo, Paolo Walter,
- Cavasinni, V,
- Cervera-Villanueva, A,
- Chukanov, A,
- Collazuol, G,
- Conforto, G,
- Conta, C,
- Contalbrigo, M,
- Cousins, R D,
- Daniels, D C,
- Degaudenzi, H M,
- Del Prete, T,
- De Santo, A,
- Dignan, T,
- Di Lella, L,
- Dumarchez, J,
- Ellis, M,
- Fazio, T,
- Feldman, G J,
- Ferrari, R,
- Ferrère, D,
- Flaminio, Vincenzo,
- Fraternali, M,
- Gaillard, Jean-Marc,
- Gangler, E,
- Geiser, A,
- Geppert, D,
- Gibin, D,
- Gninenko, S N,
- Godley, A,
- Gómez-Cadenas, J J,
- Gosset, J,
- Gössling, C,
- Gouanère, M,
- Grant, A,
- Graziani, G,
- Guglielmi, A M,
- Hagner, C,
- Hernando, J,
- Hubbard, D B,
- Hurst, P,
- Hyett, N,
- Iacopini, E,
- Joseph, C L,
- Juget, F R,
- Kirsanov, M M,
- Klimov, O L,
- Kokkonen, J,
- Kovzelev, A,
- Krasnoperov, A V,
- Kustov, D V,
- Kuznetsov, V,
- Lacaprara, S,
- Lachaud, C,
- Lakic, B,
- Lanza, A,
- La Rotonda, L,
- Laveder, M,
- Letessier-Selvon, A A,
- Lévy, J M,
- Linssen, Lucie,
- Ljubicic, A,
- Long, J,
- Lupi, A,
- Marchionni, A,
- Martelli, F,
- Méchain, X,
- Mendiburu, J P,
- Meyer, J P,
- Mezzetto, Mauro,
- Mishra, S R,
- Moorhead, G F,
- Naumov, D V,
- Nédélec, P,
- Nefedov, Yu A,
- Nguyen-Mau, C,
- Orestano, D,
- Pastore, F,
- Peak, L S,
- Pennacchio, E,
- Pessard, H,
- Petti, R,
- Placci, Alfredo,
- Polesello, G,
- Pollmann, D,
- Polyarush, A Yu,
- Popov, B,
- Poulsen, C,
- Rathouit, P,
- Rico, J,
- Riemann, P,
- Roda, C,
- Rubbia, André,
- Salvatore, F,
- Schahmaneche, K,
- Schmidt, B,
- Schmidt, T,
- Sevior, M E,
- Sillou, D,
- Soler, F J P,
- Sozzi, G,
- Steele, D,
- Stiegler, U,
- Stipcevic, M,
- Stolarczyk, T,
- Tareb-Reyes, M,
- Taylor, G N,
- Tereshchenko, S,
- Toropin, A N,
- Touchard, A M,
- Tovey, Stuart N,
- Tran, M T,
- Tsesmelis, E,
- Ulrichs, J,
- Vacavant, L,
- Valdata-Nappi, M,
- Valuev, V Yu,
- Vannucci, François,
- Varvell, K E,
- Veltri, M,
- Vercesi, V,
- Vieira, J M,
- Vinogradova, T G,
- Weber, F,
- Weisse, T,
- Wilson, F F,
- Winton, L J,
- Yabsley, B D,
- Zaccone, Henri,
- Zuber, K,
- Zuccon, P
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Abstract |
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The $\Lambda$ polarization in $\nu_\mu$ 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: $P_x (x_F < 0) = -0.21 \pm 0.04 \mbox{(stat)} \pm 0.02 \mbox{(sys)}$. In the current fragmentation region we find $P_x (x_F > 0) = -0.09 \pm 0.06 \mbox{(stat)} \pm 0.03 \mbox{(sys)}$. These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization (in the direction orthogonal to the $\Lambda$ production plane) has been observed for the first time in a neutrino experiment: $P_y = -0.22 \pm 0.03 \mbox{(stat)} \pm 0.01 \mbox{(sys)}$. The dependence of the absolute value of $P_y$ on the $\Lambda$ transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the results from unpolarized |
Publication details |
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