P.J. Carlson

Increased photoelectron collection efficiency of a photomultiplier in an aerogel Cherenkov counter

Abstract In a small aerogel Cherenkov counter with diffusing walls, an increase of the photoelectron yield by 40% was measured when the voltage across the cathode to first dynode was increased from 0.6 to 1.7 kV on the 11 cm RCA 8854 photomultiplier tube. A comparison is made with results from other experiments. A general formula for diffusion-type counters is given.

Elastic forward and backward scattering of π− and K-mesons at 5.2 and 7.0 GeV/c

Abstract We present results of measurements of the differential cross sections for the following elastic-scattering reactions: (i) π + p at 5.2 and 7.0 GeV/ c in the range −1 u c ) 2 , (ii) π − p at 7.0 GeV/ c in the range −0.7 u c ) 2 , (iii) K + p at 5.2 and 7.0 GeV/ c in the ranges −1 t c ) 2 and −1 u c ) 2 , and K − p at 7.0 GeV/ c in the range −1 u c ) 2 . Backward peaks were observed in K + p scattering with an energy dependence s −4 . No event was found in backward K − p scattering. The anglar distributions of forward K + p elastic scattering show no structure. Backward π + p elastic scattering shows the known dip at u ≈ −0.15 (GeV/ c ) 2 , which in this experiment was covered in one geometry.

Tests of large Čerenkov detectors with silica aerogel as radiator

Abstract Cerenkov detectors with silica aerogel as radiator, and a detector surface of about 18 × 52 cm 2 , have been tested in a particle beam at the CERN Proton Synchrotron. For 9 cm thickness of silica aerogel the number of photoelectrons for β = 1 particles was found to be 4.6 and 5.5 respectively, depending on the light collection system used.

Kp and πp backward elastic scattering at 5.2 and 6.9 GeV/c

Abstract The angular distributions of K + p and π + p backward elastic scattering have been measured at 5.2 and 6.9 GeV/ c . Backward π - p and K - p elastic scattering were studied at 6.9 GeV/ c . Backward peaks are observed in K + p scattering with an energy dependence of the form s −4 .

K±p elastic scattering at 3.55 GeV/c

Abstract We present results of measurements of K±p elastic scattering at 3.55 GeV/c in the c.m. angular ranges from 10° to 70° (0.16

Experimental evidence for the onset of Baryon exchange in πp backward scattering below 3 GeV/c

Abstract We present the results of measurements of π + p elastic scattering at 2.85, 3.30, and 3.55 GeV/ c , and of π − p at 2.85 and 3.55 GeV/ c in the c.m. angular range from 102° to 163°. These results complement previously published data [1,2] which covered the angular region from 164° to 176°. The data show that the differential cross sections as a function of u have the same shape as at higher energies, with the pronounced dip at u = −0.15 (GeV/ c ) 2 in the case of π + p.

Elastic backward scattering of pions and kaons

Abstract The elastic scattering of gp + mesons by protons near 180° has been measured at 2.85, 3.30, and 3.55 GeV/ c , that of π − mesons at 3.30 and 3..55 GeV/ c , and that of K + and K − mesons at 3.55 GeV/ c . Steeply rising backward peaks are observed at all energies for π + p scattering, whereas the π −1 p angular distributions are not as steep. K + p elastic scattering also shows a backward peak. No backward K − p elastic scattering event was found. The upper limit (90% confidence) for the K − p differential cross section is twelve times smaller than the corresponding K + p cross section. The behaviour of the differential cross section close to 180° can be explained using direct channel resonances. The large ratio of the K + p to K − p cross section can be understood in terms of baryon exchange.

BACKWARD Kp ELASTIC SCATTERING AT 3.55 GeV/c.

Backward elastic K+p and K−p scattering has been measured in the angular interval 168o < θc.m. < 177o. We find (dσ/dΩ) K+p → pK+ = 17 ± 4 μb/sr and (dσ/dΩ)K−p → pK− < 0.6 μb/sr. K+p elastic scattering exhibits a backward peak.

Improved yield of photomultipliers for Cherenkov light

The combined effects of using a wavelength shifter and higher voltage for better photoelectron collection is shown to give a gain of 70% in the photo-electron yield for the 11 cm diameter phototube RCA 8854 in a typical Cherenkov counter.

Large-angle K+p elastic scattering at 10 GeV/c

Abstract K+p elastic scattering has been measured over nearly the whole angular range at an incident momentum of 10 GeV/c. The differential cross-section is found to decrease smoothly in the forward direction to -t ≈ 2 (GeV/c)2, where there is a change in slope, followed by a further decrease to -t ≈ 6 (GeV/c)2. Around 90° c.m. the cross-section is approximately 1 nb/(GeV/c)2, which is more than two orders of magnitude lower than at 5 GeV/c. The backward peak has no structure.