Search

A photon beam test of the 4 m long prototype lead/scintillating-fibre module for the GlueX electromagnetic barrel calorimeter was carried out in Hall B at the Thomas Jefferson National Accelerator Facility with the objective of measuring the energy and timing resolutions of the module as well as the number of photoelectrons generated. Data were collected over an energy range of 150–650 MeV at multiple positions and angles along the module. Details of the analysis at the centre of and perpendicular to the module are shown herein; the results are σ E / E = 5.4 % / E ( GeV ) ⊕ 2.3 % , σ Δ T / 2 = 70 / E ps, and 660 photoelectrons for 1 GeV at each end of the module.

We describe the design and operation of a detector system for measuring all-photon decays of mesons photoproduced in a tagged photon beam with energies between 4.3 and 5.4 GeV and a flux of 5×107 tagged photons per second. Photons from meson decays were detected with a lead-glass calorimeter with an energy resolution of 11% at 1 GeV. Various veto and trigger components were also present. Final states with as many as six photons were successfully detected and reconstructed.

The time and amplitude characteristics of a scintillation counter were investigated on an accelerator beam with a momentum of 5 GeV/c at the Institute for High Energy Physics. The scintillator, with a length of 2 m and a cross section of 2.5 × 2.5 cm2, was viewed from its end faces by ΦЭУ-115M photomultiplier tubes (PMTs). The dependences of the signal amplitude and the time resolution of a PMT on the position of a particle track along the scintillator were described by quadratic exponentials. When a constant fraction discriminator was used to form the PMT signal, the time resolutions at the center and at the periphery of the counter were 150 and 80 ps, respectively. Better results were obtained with a standard leading-edge discriminator after correcting the dependence of its response time on the signal amplitude.

Phototubes associated with a Cherenkov counter, with a wall of scintillation counters for time-of-flight measurements and with a wall of lead glass blocks of an electro-magnetic calorimeter will operate in the fringe field of a superconducting solenoid in the GlueX experiment. The solenoid will be operated with a central magnetic field of ≈ 2.5 T . The maximum fringe field in the vicinity of the phototubes will be approximately 150 G . Various techniques for magnetic shielding of phototubes were studied using a 1-m diameter Helmholtz coil arrangement operated with a maximum central field of 200 G . Results are presented.

Timing properties of two types of scintillation counters have been studied in 5 GeV /c hadron beam of the IHEP (Protvino) accelerator. The counters are prototypes of hodoscope elements that will be used in experiments for particle identification and fast timing of events. Scintillator cross-sections are 1.25×6.0 and 2.5×2.5 cm 2 and their length is 2 m . The dependence of the time resolution on the particle coordinate along the counters and on the beam intensity is presented.

Timing characteristics of two time-of-flight scintillation counters were studied using particle beams at the IHEP (Protvino) accelerator. The bars were 2 m long and had a cross-section of 2.5×6.0 cm 2 . Each bar was viewed from both ends by XP2020 photomultipliers. A time resolution better than 40 ps was achieved.

The proposed Hall D detector at Jefferson Lab will have a time-of-flight detector composed of long and narrow scintillator bars. We have evaluated the time resolution of two bar prototypes in particle beams at the Institute for High Energy Physics in Protvino, Russia. The bars are 2.0 m long and have square cross-sections of size 2.5 and 5.0 cm 2 . In this paper, we present results on how the time resolution of each of these bars depends on the entry position of the beam into the scintillator, on the material used for scintillator wrapping and on the phototube used for the readout.

New measurements of peripheral meson production are presented. The data confirm the existence of exotic mesons at 1.4 and 1.6 GeV/c2. The latter state dominates the eta'pi- decay spectrum. The data on eta pi+pi-pi- decay show large strength in several exotic (Jpc = 1- +) waves as well.

Brookhaven Experiment E852 is an experiment in meson spectroscopy configured to detect final states interactions of π − p collisions in search for meson states incompatible with the constituent quark model. A description of the experimental apparatus and a general overview of the latest results is given.

The design and construction of a Cockcroft–Walton-type base for the Russian FEU84-3 photomultiplier are described. Several unique features are emphasized. Results from the tests of prototypes are presented.

A 3045 element lead glass calorimeter and an associated fast trigger processor have been constructed, tested and implemented in BNL experiment E852 in conjunction with the multi-particle spectrometer (MPS). Approximately, 10 9 all-neutral and neutral plus charged triggers were recorded with this apparatus during data runs in 1994 and 1995. This paper reports on the construction, testing and performance of this lead glass calorimeter and the associated trigger processor.

A cylindrical multiwire drift chamber with axial charge-division has been constructed and used in experiment E852 at Brookhaven National Laboratory. It serves as a trigger element and as a tracking device for recoil protons in π p interactions. We describe the chamber's design considerations, details of its construction, electronics, and performance characteristics.

The design, construction, and performance of a 198-element CsI detector built for Brookhaven experiment E852 is described. Design considerations for the array included such factors as rate, magnetic field, sensitivity and acceptance. Signals were obtained with a photodiode/preamplifier combination using PIN photodiodes. Data were taken over the course of two runs during the summers of 1993 and 1994. A calibration procedure using halo muons is described. The gain, energy resolution, and position resolution of the detector are discussed. Finally, the ability of the detector to be used as a low energy photon veto is illustrated using the data.

A scintillation detector meeting specific physics requirements and geometrical constraints is described. It operates with high efficiency inside a 1 T magnet in an intense charged particle beam of up to 3 × 106 particles/s. It uses a unique light collection system combining air space, wavelength shifter disc and conventional lucite light guides. The detector is used in a veto mode to identify interactions that produce an all-neutral final state. The details of the counter's design, construction and performance are described.

Two prototype lead glass calorimeters have been constructed and tested at the AGS at Brookhaven National Lab. The first is a 25-element prototype (P1)

A partial wave analysis ~PWA! of the hp 0 system ~where h!gg) produced in the charge exchange reaction p 2 p!hp 0 n at an incident momentum of 18 GeV/c is presented as a function of the hp 0 invariant mass mhp 0 and momentum transfer squared t p2!hp , from the incident p 2 to the outgoing hp 0 system. S, P, and D waves were included in the PWA. The a0(980) and a2(1320) states are clearly observed in the overall hp 0 effective mass distribution as well as in the amplitudes associated with S wave and D waves, respectively, after partial wave decomposition. The observed distributions in moments ~averages of spherical harmonics! were compared to the results from the PWA and the two are consistent. The distribution in t p2!hp for individual D waves associated with natural and unnatural parity exchange in the t channel are consistent with Regge phenomenology. Of particular interest in this study is the P wave since this leads to an exotic J PC 51 21 for the hp system. A P wave is present in the data; however, attempts to describe the mass dependence of the amplitude and phase motion with respect to the D wave as a Breit-Wigner resonance are problematic. This has implications regarding the existence of a reported exotic J PC 51 21 meson decaying into hp 0 with a mass near 1.4 GeV/c 2 .

A partial wave analysis of the ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ system produced in the charge exchange reaction ${\ensuremath{\pi}}^{\ensuremath{-}}\stackrel{\ensuremath{\rightarrow}}{p}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}n$ at an incident momentum of 18.3 $\mathrm{GeV}/c$ is presented as a function of the ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ invariant mass ${m}_{{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}}$ and momentum transfer squared $|t|$ from the incident ${\ensuremath{\pi}}^{\ensuremath{-}}$ to the outgoing ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ system. For small values of $|t|,$ the S-wave intensity shows a broad enhancement at low ${m}_{{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}}$ with a sharp dip in the vicinity of the ${f}_{0}(980).$ A dip is also observed in the vicinity of the ${f}_{0}(1500).$ There is a rapid variation of the S to ${D}_{0}$ relative phase difference in these mass regions. For large values of $|t|,$ the ${f}_{0}(980)$ appears as a bump. The ${f}_{2}(1270),$ observed in D waves, is produced dominantly by $\ensuremath{\pi}$ exchange at low values of $|t|$ and ${a}_{2}$ exchange at higher values of $|t|.$

A partial-wave analysis of 9082 {eta}{pi}{sup +}{pi}{sup -}n events produced in the reaction {pi}{sup -}p{yields}{eta}{pi}{sup +}{pi}{sup -}n at 18.3 GeV/c has been carried out using data from experiment 852 at Brookhaven National Laboratory. The data are dominated by J{sup PC}=0{sup -+} partial waves consistent with observation of the {eta}(1295) and the {eta}(1440). The mass and width of the {eta}(1295) were determined to be 1282{+-}5 MeV and 66{+-}13 MeV, respectively, while the {eta}(1440) was observed with a mass of 1404{+-}6 MeV and a width of 80{+-}21 MeV. Other partial waves of importance include the 1{sup ++} and the 1{sup +-} waves. Results of the partial wave analysis are combined with results of other experiments to estimate f{sub 1}(1285) branching fractions. These values are considerably different from current values determined without the aid of amplitude analyses. (c) 2000 The American Physical Society.

Events of the type {pi}{sup {minus}}p{r_arrow}n{eta}{pi}{sup +}{pi}{sup {minus}} and {pi}{sup {minus}}p{r_arrow}n{eta}{pi}{sup 0} at 18thinspGeV/c are analyzed. The mass and width of the neutral and charged a{sub 0}(980) were determined. The neutral a{sub 0} is found to have a mass of (0.991{plus_minus}0.0025)thinspGeV/c{sup 2} and a width of (0.069{plus_minus}0.011)thinspGeV/c{sup 2}. A partial wave analysis technique yields (0.9983{plus_minus}0.0040) and (0.072{plus_minus}0.010)thinspGeV/c{sup 2} for the mass and width of the charged a{sub 0}. {copyright} {ital 1998} {ital The American Physical Society}