Apparatus to study crystal channeling and volume reflection phenomena at the SPS H8 beamline

none52A high performance apparatus has been designed and built by the H8-RD22 collaboration for the study of channeling and volume reflection phenomena in the interaction of 400 GeV/c protons with bent silicon crystals, during the 2006 data taking in the external beamline H8 of the CERN SPS. High-quality silicon short crystals were bent by either anticlastic or quasimosaic effects. Alignment with the highly parallel (8 µrad divergence) proton beam was guaranteed through a submicroradian goniometric system equipped with both rotational and translational stages. Particle tracking was possible by a series of silicon microstrip detectors with high-resolution and a parallel plate gas chamber, triggered by various scintillating detectors located along the beamline. Experimental observation of volume reflection with 400 GeV/c protons proved true with a deflection angle of (10.4±0.5) µrad with respect to the unperturbed beam, with a silicon crystal whose (111) planes were parallel to the beam.noneW. Scandale; I. Efthymiopoulos; D. A. Still; A. Carnera; G. Della Mea; D. De Salvador; R. Milan; A. Vomiero; S. Baricordi; S. Chiozzi; P. Dalpiaz; C. Damiani; M. Fiorini; V. Guidi;G. Martinelli; A. Mazzolari; E. Milan; G. Ambrosi; P. Azzarello; R. Battiston; B. Bertucci; W. J. Burger; M. Ionica; P. Zuccon; G. Cavoto; R. Santacesaria; P. Valente; E. Vallazza;A. G. Afonin; V. T. Baranov; Y. A. Chesnokov; V. I. Kotov; V. A. Maisheev; I. A. Yazynin; S. V. Afanasiev; A. D. Kovalenko; A. M. Taratin; N. F. Bondar; A S. Denisov; Y. A. Gavrikov; Y. M. Ivanov; V. G. Ivochkin; S. V. Kosyanenko; L. P. Lapina; P. M. Levtchenko; A. A. Petrunin; V. V. Skorobogatov; V. M. Suvorov; D. Bolognini; L. Foggetta; S. Hasan; M. PrestW., Scandale; I., Efthymiopoulos; D. A., Still; A., Carnera; G., Della Mea; D., De Salvador; R., Milan; A., Vomiero; Baricordi, Stefano; S., Chiozzi; Dalpiaz, Pietro; Damiani, Chiara; Fiorini, Massimiliano; Guidi, Vincenzo; Martinelli, Giuliano; Mazzolari, Andrea; Milan, Emiliano; G., Ambrosi; P., Azzarello; R., Battiston; B., Bertucci; W. J., Burger; M., Ionica; P., Zuccon; G., Cavoto; R., Santacesaria; P., Valente; E., Vallazza; A. G., Afonin; V. T., Baranov; Y. A., Chesnokov; V. I., Kotov; V. A., Maisheev; I. A., Yazynin; S. V., Afanasiev; A. D., Kovalenko; A. M., Taratin; N. F., Bondar; A. S., Denisov; Y. A., Gavrikov; Y. M., Ivanov; V. G., Ivochkin; S. V., Kosyanenko; L. P., Lapina; P. M., Levtchenko; A. A., Petrunin; V. V., Skorobogatov; V. M., Suvorov; D., Bolognini; L., Foggetta; S., Hasan; M., Pres

Production asymmetry of D-s from 600 GeV/c Sigma(-) and pi(-) beam

The production of D-S(-) relative to D-S(+) as a function of x(F) with 600 GeV/c Sigma(-) beam is measured in the interval 0.15 < x(F) < 0.7 by the SELEX (E781) experiment at Fermilab. The integrated charge asymmetries with 600 GeV/c Sigma(-) beam (0.53 +/- 0.06) and pi(-) beam (0.06 +/- 0.11) are also compared. The results show the Sigma(-) beam fragments play a role in the production of D-S(-), as suggested by the leading quark model. (C) 2003 Elsevier Science B.V. All rights reserved

First measurement of pi(-)e ->pi(-)e gamma pion virtual compton scattering

Pion virtual compton scattering (VCS) via the reaction pi(-)e-->pi(-)egamma was observed in the Fermilab E781 SELEX experiment. SELEX used a 600 GeV/c pi(-) beam incident on target atomic electrons, detecting the incident pi(-) and the final state pi(-), electron and gamma. Theoretical predictions based on chiral perturbation theory are incorporated into a Monte Carlo simulation of the experiment and are compared to the data. The number of reconstructed events (=9) and their distribution with respect to the kinematic variables (for the kinematic region studied) are in reasonable accord with the predictions. The corresponding pi(-) VCS experimental cross section is sigma=38.8+/-13 nb, in agreement with the theoretical expectation of sigma=34.7 nb

Measurement of the D-s(+/-) lifetime

We report a precise measurement of the D-s(+/-) meson lifetime. The data were taken by the SELEX experiment (E781) spectrometer using 600 GeV/c Sigma (-), pi (-) and p beams. The measurement has been done using 918 reconstructed D-s(+/-). The lifetime of the D-s(+/-) s is measured to be 472.5 +/- 17.2 +/- 6.6 fs, using K*(892)K-0(+/-) and phi pi (+/-) decay modes. The lifetime ratio of D-s(+/-) to D-0 is 1.145 +/- 0.049. (C) 2001 Elsevier Science B.V. All rights reserved

First observation of the doubly charmed baryon Xi(+)(cc)

We observe a signal for the doubly charmed baryon Xi(cc)(+) in the charged decay mode Xi(cc)(+)-->Lambda(c)(+)K(-)pi(+) in data from SELEX, the charm hadroproduction experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1+/-0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is 3519+/-1 MeV/c(2). The Gaussian mass width of this state is 3 MeV/c(2), consistent with resolution; its lifetime is less than 33 fs at 90% confidence