[en] We report the results of a new Ξ_c⁺ lifetime measurement from hadroproduction data taken by the SELEX (E781) experiment. Fermilab charged hyperon beam (Σ^-, π^- and p) at 600 GeV is used to produce charm particles in Cu and diamond targets. This measurement was made using decays into the Ξ_c⁺→Ξ^-π⁺π⁺, Ξ_c⁺→p⁺K^-π⁺, and Ξ_c⁺→Σ⁺K^-π⁺ modes. We used binned maximum likelihood method and 301 ± 31 events yield a lifetime of 430 ± 22 ± 9 fs

[en] The unprecedented radiation levels in current Large Hadron Collider runs, and plans to even increase the luminosity creates a need for new detector technologies to be investigated. Quartz plates to replace the plastic scintillators in current LHC calorimeters have been proposed in recent reports. Quartz based Cherenkov calorimeters can solve the radiation damage problem, however light production and transfer have proven to be challenging. This report summarizes the results from a computational study on the performance of a high-density glass calorimeter. High-density, scintillating, fluoride glass, CHG3, was used as the active material. This glass has been developed specifically for hadron collider experiments, and is known for fast response time, in addition to high light yield. Here, the details of a Geant4 model for a sampling calorimeter prototype with 20 layers, and its hadronic as well as electromagnetic performances are reported

[en] The two most recent and precise measurements of the charged kaon mass use X-rays from kaonic atoms and report uncertainties of 14 ppm and 22 ppm yet differ from each other by 122 ppm. We describe the possibility of an independent mass measurement using the measurement of Cherenkov light from a narrow-band beam of kaons, pions, and protons. This technique was demonstrated using data taken opportunistically by the Main Injector Particle Production experiment at Fermi National Accelerator Laboratory which recorded beams of protons, kaons, and pions ranging in momentum from +37 GeV/c to +63 GeV/c. The measured value is 491.3 ± 1.7 MeV/c², which is within 1.4σ of the world average. An improvement of two orders of magnitude in precision would make this technique useful for resolving the ambiguity in the X-ray data and may be achievable in a dedicated experiment

[en] New generation hadron colliders are going to reach unprecedented energies and radiation levels. Quartz has been identified as a radiation-hard material that can be used for Cerenkov calorimeters of the future experiments. We report from the radiation hardness tests performed on quartz fibers, as well as the characteristics of the quartz fiber and plate Cerenkov calorimeters that have been built, designed, and proposed for the CMS experiment

[en] We have measured the polarization of Λ⁰ and (bar Λ⁰) inclusively produced by 610 GeV/c Σ^- and 525 GeV/c proton beams in the experiment SELEX during the 1996/7 fixed target run at Fermilab. The polarization was measured as a function of the Λ longitudinal momentum fraction x_F and transverse momentum p_t. For the Λ⁰ produced by Σ^- the polarization is increasing with x_F , from slightly negative at x_F ∼ 0 to about 15% at large x_F ; it shows a non-monotonic behavior as a function of p_t. For the proton beam, the Λ⁰ polarization is negative and decreasing as a function of x_F and p_t. The (bar Λ⁰) polarization is compatible with 0 for both beam particles over the full kinematic range. The target dependence was examined but no statistically significant difference was found

[en] The authors report the first observation of two Cabibbo-suppressed decay modes, Ξ_c⁺ → Σ⁺π^-π⁺ and Ξ_c⁺ → Σ^- π⁺π⁺. They observe 56 ± 13 over a background of 21, and 23 ± 7 over a background of 12 events, respectively, for the signals. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Σ^- beam. The branching ratios of the decays relative to the Cabibbo-favored Ξ_c⁺ → Ξ^-π⁺π⁺ are measured to be B(Ξ_c⁺ → Σ⁺π^-π⁺)/B(ξ_c⁺ → Ξ^- π⁺π⁺) = 0.50 ± 0.20, and B(Ξ_c⁺ → Σ^-π⁺π⁺)/B(Ξ_c⁺ → Ξ^-π⁺π⁺) = 0.23 ± 0.11, respectively. They also report branching ratios for the same decay modes of the Λ_c⁺ relative to Λ_c⁺ → pK^-π⁺

[en] We present the results of the tests performed on 90 photomultiplier tubes (PMT) to characterize their afterpulses. Three different types of Hamamatsu PMTs (R7525, R6427, and R1398) were studied for their afterpulse rates and timings at different incident light intensities and gain values, at the University of Iowa PMT test station. Afterpulse rates show slight increase with the PMT gain, but there is almost no dependence on incident light intensity. Three specific time delays are determined for the afterpulses, and their individual rate contributions are characterized. The results from manufacturer's independent tests on R7525 PMTs are reported, as well. The possible effects of these afterpulses on the future hadron collider experiments are also discussed

[en] The first pre-production-prototype (PPP-I) of the quartz fibre calorimeter of the CMS detector has been tested at CERN. The calorimeter consists of quartz fibres embedded in an iron matrix. Results are presented on the energy resolution and on the signal uniformity of the prototype for electrons and pions and the signal uniformity and linearity. (research note from collaboration)

[en] We investigated the darkening of nine high OH^- fibre types irradiated with 500 MeV electrons from the Linac Injector of LEP (LIL) at CERN. The transmission of Xe light was measured in situ in the 350-800 nm range. The induced attenuation at 450 nm is typically 1.52±0.15 dB/m for a 100 Mrad absorbed dose. Two-parameter fits for darkening and recovery are presented. After irradiation the tensile strength remains essentially unchanged. For Polymicro quartz core fibres the tensile strength is typically 4.6±0.4 GPa

[en] The borosilica, a very common PMT window and envelope material, contains 5% Boron (1% ¹⁰B). The high cross section for ¹⁰B capturing thermal neutrons (3980 barn), is a concern for LHC experiments using borosilica window PMTs. This study investigates the rate and the size of the signals generated by thermal neutron boron interaction in borosilica window PMTs; Hamamatsu R7525-HA and R7600U-200-M4. Although virtually all of the thermal neutrons incident on the borosilicate glass are absorbed, probability of generating a PMT signal was measured to be 3 x 10^-4 and 3 x 10^-6 for R7525-HA and R7600U-200-M4 PMTs, respectively. For these signals the average pulse size was found to be between 20-30 photoelectrons. We also discuss that four anode PMTs allow the elimination of these events with an offline algorithm.