HyperCP: A high-rate spectrometer for the study of charged hyperon and kaon decays

The HyperCP experiment (Fermilab E871) was designed to search for rare phenomena in the decays of charged strange particles, in particular CP violation in $\Xi$ and $\Lambda$ hyperon decays with a sensitivity of $10^{-4}$. Intense charged secondary beams were produced by 800 GeV/c protons and momentum-selected by a magnetic channel. Decay products were detected in a large-acceptance, high-rate magnetic spectrometer using multiwire proportional chambers, trigger hodoscopes, a hadronic calorimeter, and a muon-detection system. Nearly identical acceptances and efficiencies for hyperons and antihyperons decaying within an evacuated volume were achieved by reversing the polarities of the channel and spectrometer magnets. A high-rate data-acquisition system enabled 231 billion events to be recorded in twelve months of data-taking.Comment: 107 pages, 45 Postscript figures, 14 tables, Elsevier LaTeX, submitted to Nucl. Instrum. Meth.

ASYMMETRY IN n+ PHOTOPRODUCTION FROM A POLARIZED TARGET AT 5 AND16 GeV

The authors have measured the asymmetry in the cross section for the reaction {gamma}p {yields} {pi}{sup +}n between the two stages of polarization of the initial proton normal to the plane of scattering. The initial laboratory photon energies, k, were 5 GeV and 16 GeV, and the regions of momentum transfer, t, covered were 0.14 {le} {radical}-t {le} 1.01 GeV/c and 0.14 {le} {radical}-t {le} 0.78 GeV/c respectively. A butanol polarized target was used with the SLAC 20 GeV/c magnetic spectrometer. The data show a sizeable asymmetry at both 5 GeV and 16 GeV. The 16 GeV data peak at {radical}-t {approx} 0.30 GeV/c with an asymmetry of about -0.70, and the 5 GeV data pak at {radical}-t {approx} 0.80 GeV/c with an asymmetry of about -0.70. The direction of our normal to the scattering plane is along (photon in) x (pion out)

CP violation in strange baryon decays: A report from Fermilab experiment 871

Fermilab experiment 871, HyperCP, is a search for direct CP violation in Ξ and Λ hyperon decays. A non-zero value in the asymmetry parameter A, defined in terms of the decay parameter products αΞαΛαΞαΛ and ,αΞ̄αΛ̄, would be unambiguous evidence for direct CP violation. The first data-taking run finished at the end of 1997 and accumulated over one billion Ξ−Ξ− and +Ξ̄+ decays. A sensitivity in A of ≈ 10−4≈10−4 is expected. A review of CP violation in hyperon decays is given, the HyperCP detector is described, and the status of the data analysis is discussed. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87472/2/107_1.pd

PROTOTYPE RESULTS OF A HIGH RESOLUTION VERTEX DRIFT CHAMBER FOR THE MARK II SLC UPGRADE DETECTOR*

Test results from a full-length prototype of the drift chamber vertex detector for the Mark II SLC Upgrade detector are presented. The 22 cell jet chamber employs planes of grid wires above and below the sense wire plane to increase the electrostatic stability of the sense wires and to narrow the electron arrival time distribution. Two different grid designs have been investigated. The spatial resolution and pulse widths have been measured at a variety of operating points and for different timing schemes in a mixture of 92 % CO2 and 8 % isobutane. Typical results at 3 atmospheres pressure give an average resolution over a 2 cm drift distance of 30 pm for both designs. Efficient double track detection is achieved for tracks separated by 500 pm for one design and by 1000 pm for the other

Measurement of the polarization parameter for the reaction pipisup−sup - pYieldsYieldspipisup0sup 0n between 1.03 and 1.79 GeV/c

From 2nd international conference on elementary particles; Aixen- Provence, France (6 Sep 1973). Measurements of the polarization parameter for the reaction pi /sup -/p yields pi /sup o/n were made at the five momenta 1.03, 1.245, 1.44, 1.5 and 1.79 GeV/c. A polarized target was used, with polarizations achieved ranging from 48 to 57%. Salient features of the experiment were the use of neutron counters for time-of-flight measurements as well as angular information and the use of optical spark chambers, seven to eight radiation lengths thick, for the detection of the gamma rays from the decay of the pi /sup o/. The center-ofmass angular range covered by the 20 neutron counters was typically --.78 < cos THETA /sub c.m. <.87. For each momentum there are approximately 10,000 events which fit pi /sup -/p yields pi /sup o/ n with a confide nce level of at least 10%. (auth