117228255
Response of the D0 Muon Chamber to changes in voltage, incident angle, gas composition, and oxygen contamination
The measured space point resolution of a D0 Muon Chamber is /+-/0.31 mm perpendicular to the anode wire and 2.7 mm parallel to the wire. A voltage change of 1 kV, which changes the gas gain by a factor of 50, only causes a change of drift velocity of 12%. Tracks inclined of 45/degree/ have a resolution worse than those of 0/degree/ by a factor 3 /+-/ 2. A change in gas composition from CO/sub 2/(10%) to CO/sub 2/(11%) decreases the gas gain by 17 /+-/ 5%, and decreases drift velocity by 0.2 /+-/ 0.2%. The effect of an oxygen contamination of 3200 ppM is to change the mean pulse height by 45% over the 5 cm width of the cell. 4 refs., 15 figs.
119054052
Search for W pair production with dilepton decay modes at D0
We present the results of a search of 13.5 pb{sup {minus}1} of p{bar p} collisions at {radical}s = 1.8 TeV for WW {yields} dileptons + X using the DO detector. One WW {yields} e{mu}v{bar v} + X candidate was found with an expected background of about 0.96 {plus_minus} 0.44 events. One WW {yields} e{mu}v{bar v} + candidate was found with an expected background of about 1.23 {plus_minus} 0.87 events. The 95% C.L. upper limit for the W pair production cross section is 133 pb without background subtraction. Making the constraint {kappa} = 1 ({Delta}{kappa} = 0) implies {minus}2.6 {le} {gamma} {le} 2.7 (95% C.L.) and making the constraint {gamma} = 0 implies {minus} 3.3 {le} {Delta}{kappa} {le} 3.5 (95% C.L.) assuming {kappa}{sub {gamma}} = {kappa}{sub {Zeta}} and {lambda}{sub {gamma}} = {lambda}{sub {Zeta}}. We also present the contour of excluded couplings when {kappa} and {lambda} are allowed to simultaneously vary from their standard model values.
121059853
Space-charge effects in the catcher gas cell of a rf ion guide
Slow radioactive ion beams have been produced with an overall efficiency of 4% by thermalizing energetic ions produced by a projectile fragment separator in a He-gas cell and guiding them to a vacuum vessel by dc and rf fields. Space charge was observed to have a limiting effect. Since the ionization of He atoms by energetic ions creates a region of high space charge, many thermalized ions of interest are pushed toward the walls of the gas cell. Such losses have been investigated for different incoming ion intensities.
31219355
New scheme for positron accumulation in ultrahigh vacuum.
A new positron accumulation scheme compatible with ultrahigh vacuum conditions has been developed, which is realized by preparing a high density electron plasma as high as approximately 10(11) cm(-3) and an ion cloud as energy absorbers. The present accumulation rate normalized by the intensity of 22Na positron source is (3.6+/-0.3)x10(2)e(+)/s/mCi, which is more than one and a half orders of magnitude higher than other ultrahigh vacuum compatible schemes so far reported.