U. Dosselli

The ZEUS barrel and rear muon detector

Abstract Design, construction and performance characteristics of the ZEUS barrel and rear muon detector are presented.

Measurement of the proton electromagnetic form factor near threshold in the time-like region

The rate of the reaction pp→e+e− has been measured in liquid hydrogen for antiprotons at momentum values between 150 and 300 MeV/c. New precise values of the proton electromagnetic form factor in the time-like region have been obtained assuming |Ge|=|Gm| in the investigated region. The q2 dependence of the form factor close to threshold is found to have a steeper slope than indicated by existing calculations based on vector dominance models.

Precise determination of the electromagnetic form factor of the proton in the time-like region up to s = 4.2 GeV2

Abstract The s dependence of the proton form factor in the time-like region has been determined up to s=4.2 GeV2, assuming the validity of the |Ge| = |Gm| = |G| hypothesis. Data were taken in a dedicated experiment performed at the LEAR antiproton ring at CERN, increasing by one order of magnitude the available statistics on the proton form factor near threshold in the time-like region. Our result consist of cross section measurements of the p p → e + e − reaction for different beam momenta in the kinematical r 3.6⩽s⩽4.2 GeV2. The observed s dependence of the form factor close to threshold differs appreciably from the one suggested by previous experiments.

Performance of the drift tubes for the barrel muon chambers of the CMS detector at LHC

Abstract The barrel muon chambers of the CMS detector consist of three sets of four layers of rectangular drift tubes. The performance of several prototypes was measured in a muon beam for various experimental conditions. Special emphasis was given to study performance aspects related to the trigger capability of the chambers.

A large solid angle magnetic detector for precision studies of e.m. processes in low-energy p interactions

The detector presented is designed to measure the proton e.m. form factors by measuring e+e− pairs produced in pp annihilations at low energy or at rest. In this paper the apparatus is described in detail, with emphasis on how to achieve a suppression factor of about 1010 of the hadronic background.

Test results of the ASIC front-end trigger prototypes for the muon barrel detector of CMS at LHC

Abstract A sample of ASIC prototypes of the first-level trigger front-end device for the muon barrel drift chambers of CMS was tested on a full size chamber prototype. Tests were performed at several incident angles on cosmic rays and at normal incidence using a muon beam. The chamber was irradiated using a 137 C s gamma source to simulate the LHC radiation environment. The performance of the tested prototypes with respect to efficiency, resolution and noise issues is reported.

Drift time measurements in limited streamer tubes

Abstract We have investigated the performances of drift time techniques applied to limited streamer tubes. A resolution of ∼ 150 μm in the coordinate across the wire is found and a way to solve the left-right ambiguity is presented.

A measurement of the pp→π+π− reaction for 158⩽p(p)⩽275 MeV/c

Abstract A measurement of the total cross section for the reaction p p → π+π− has been performed for seven values of the incident momentum between 158 and 275 MeV/c. The values obtained, if compared with previous results at higher momenta, agree with a 1/s dependence. The differential cross section sssumed over the whole incident momentum range has also been measured and the result of a fit by Legendre polynomials is given.

Efficiency studies of the front-end trigger device of the muon drift tubes for the CMS detector at LHC

Abstract Three simplified prototypes of the first-level trigger front-end device for the muon barrel drift chambers of CMS were tested on a chamber prototype. Tests were performed at several incidence angles of a muon beam and with different magnetic field configurations. The recorded drift times were also used to test a full software model reproducing the actual algorithm applied in the final ASIC being produced. The efficiency performance of this software model and of the tested prototype are presented in this paper.

A delay line on a VLSI gate array as a time digitizer

Abstract A delay line was developed on a VLSI gate array for drift time measurements on muon chambers of the ZEUS detector at HERA. It consists of 80 cells featuring a 3 ns/cell propagation time; at the start a short pulse is injected into the line and at the stop the status of the line is latched into a 10 byte register. An r.m.s. resolution better than 1 ns was obtained with this reasonably low-cost TDC.