Scintillation Counter Hodoscope Research Articles

The BALLOON-borne and PAMELA experiments for the study of the antimatter component in cosmic rays

The PAMELA experiment is based on a satellite-borne equipment actually in the final integration phase. It will be installed on board of the Russian satellite Resurs DK1 and launched in a quasi-polar orbit from the Baikonur cosmodrom at the beginning of next year. PAMELA will measure the antiproton and positron fluxes in cosmic rays with high statistics and in a large energy range (80 MeV–190 GeV for antiprotons and 50 MeV–270 GeV for positrons), extending to never investigated energies the measurements of several balloon borne experiments performed by the same PAMELA collaboration in last decade. This will make achievable sensitive tests of cosmic ray propagation models in the Galaxy and the search, in an energy range never investigated before, of possible structures in the fluxes. These structures, related to the presence of primary antiparticle sources, could be signals of “new physics”, connected with open problems like dark matter existence and matter/antimatter symmetry in the Universe. The detector consists of a very precise magnetic spectrometer, several scintillation counter hodoscopes to measure the energy losses and times of flight, and a high granularity and deep Si–W calorimeter, augmented by a very compact transition radiation detector and a He3 neutron detector hodoscope, and protected around and on the top by an anticoincidence system.

Progress in search for antihelium with BESS

We have searched for antihelium nuclei in cosmic rays using the data obtained from balloon flights of the BESS magnetic spectrometer. The search was mainly based on track-quality selection, followed by rigidity analysis, and on the time-of-flight and d E/d x measurements by the scintillation counter hodoscope. We analysed all the data collected during 1993–2000 with a common analysis procedure. No antihelium nuclei events were found in the energy range from 1 to 14 GV. In order to determine a new upper limit, we have simulated the loss in the air and in the instrument of He ( He ) using the GEANT/GHEISHA code. Combined with the data collected in 1993 through 2000, a new 95 % confidence upper limit for the ratio of H e/He at the top of the atmosphere of 6.8 × 10 −7 has been obtained to be after correcting for the interactions in the air and in the instruments.

A superconducting solenoidal spectrometer for a balloon-borne experiment

The BESS detector is a new type of balloon-borne spectrometer which utilizes various technologies recently developed for collider experiments. The principal scientific objectives include a measurement of cosmic-ray antiproton spectrum, search for anti-nuclei in cosmic radiation, and precise meaurements of cosmic-ray primaries. A thin superconducting solenoidal coil produces a uniform magnetic field of 1 T. Cylindrical drift chambers are located inside and outside the coil and perform continuous tracking. The momentum resolution is 0.5% at 1 GeV/c. i.e., the maximum detectable rigidity is 200 GV. Scintillation counter hodoscopes, placed above and below the solenoid, provide timing and d E/d x measurements and trigger generation. The timing resolution is 80 ps/counter. This cylindrical configuration achieves a large geometrical acceptance of 0.35 m 2 sr which is essential to detect rare cosmic-ray particles. In order to cope with high trigger rate and large data size, intelligent trigger circuits and a fast and parallel data acquision system are also developed. In 1993, the first scientific flight of the BESS apparatus was carried out and the first mass-measured antiprotons were detected at energies below 500 MeV

A compact beam stop for a rare kaon decay experiment

We describe the development and testing of a novel beam stop for use in a rare kaon decay experiment at the Brookhaven Alternating Gradient Synchrotron. The beam stop is located inside a dipole spectrometer magnet in close proximity to straw drift chambers and intercepts a high-intensity neutral hadron beam. The design process, involving both Monte Carlo simulations and beam tests of alternative beam-stop shielding arrangements, had the goal of minimizing the leakage of particles from the beam stop and the resulting hit rates in detectors, while preserving maximum acceptance for events of interest. The beam tests consisted of measurements of rates in drift chambers, scintillation counter hodoscopes, a gas threshold Cherenkov counter, and a lead glass array. Measurements were also made with a set of specialized detectors which were sensitive to low-energy neutrons, photons, and charged particles. Comparisons are made between these measurements and a detailed Monte Carlo simulation.

Time of flight measurements with hadronic showers

We have measured the time resolutions which can be obtained in hadronic showers from a scintillation counter hodoscope and a scintillating fibre counter at various shower depths. The hodoscope was made of 100×2×1 cm 3 BICRON 404 scintillators. The fiber counter consisted of four layers of fibers (SCSN-38, 1 mm diameter) embedded in lead with the dimensions 100×20×1 cm 3. The performance of these counters was compared for two different types of photomultipliers: Hamamatsu R2083 and Philips XP2020.

A neutron hodoscope for medium energy np scattering experiments

Abstract A 24-element plastic scintillation counter hodoscope for np elastic and total cross section measurements at LAMPF is described. Details of construction, electronics, calibration with cosmic ray muons, and a determination of absolute detection efficiency at 289 and 435 MeV are presented.

Differential cross sections for pi +p and pi -p elastic scattering from 378 to 687 MeV/c.

Differential cross sections have been measured for ${\ensuremath{\pi}}^{+}$p and ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$p elastic scattering at 378, 408, 427, 471, 509, 547, 586, 625, 657, and 687 MeV/c in the angular range -0.8${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.0.8}$. The scattered pion and recoil proton were detected in coincidence using scintillation-counter hodoscopes. A liquid-hydrogen target was used except for measurements at forward angles, in which a ${\mathrm{CH}}_{2}$ target was used. Statistical uncertainties in the data are typically less than 1%. Systematic uncertainties in acceptance and detection efficiency are estimated to be 1%. Absolute normalization uncertainties are 2--3 % for most of the data. The measurements are compared with previous data and with the results of recent partial-wave analyses. The data are fit with Legendre expansions from which total elastic cross sections are obtained.

(γ,p), (γ,pn), and (γ,pp) reactions on light nuclei in theΔ(1232) resonance region

The cross sections of the reactions (\ensuremath{\gamma},p), (\ensuremath{\gamma},pn), and (\ensuremath{\gamma},pp) are measured for $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, $^{9}\mathrm{Be}$, $^{12}\mathrm{C}$, and $^{16}\mathrm{O}$ in the \ensuremath{\Delta}(1232) resonance region by use of a tagged photon beam. Protons emitted at ${\ensuremath{\theta}}_{\mathrm{p}=30}$\ifmmode^\circ\else\textdegree\fi{} are measured by a magnetic spectrometer, and the other neutrons or protons are measured by an array of scintillation counter hodoscopes. From the present experiment, it is concluded that the reactions, \ensuremath{\gamma}+``N''\ensuremath{\rightarrow}p+\ensuremath{\pi} and \ensuremath{\gamma}+``pn''\ensuremath{\rightarrow}p+n, contribute dominantly to the (\ensuremath{\gamma},p) reaction in this energy region, where ``N'' denotes the nucleon and ``pn'' denotes the pn system in the nucleus.

Elastic π±p scattering from 378 to 687 MeV/ c

Differential cross sections for π ±p→ π ±p have been measured at P π between 378 and 687 MeV/ c at 9 angles in the range −0.8⩽cos θ c.m.⩽0.6. Scattered pions and recoil protons were detected in coincidence using scintillation counter hodoscopes. For almost all of the data the statistical and normalization uncertainties are each less than 2%. Our measurements are compared with existing data and the results of recent partial wave analyses.

Search for Slow Monopoles and Quarks

A search was made for heavy slow monopoles and quarks in the velocity range from 0.01 to 0.1 light velocity. The detector used is a scintillation counter hodoscope of \(S{\cdot}\varOmega{=}1.1\) m 2 sr and of depth 21 cm Pb plus 52 cm plastic scintillation total. The absence of candidates during the run time of 3800 hours sets an upper limit, 90% confidence level, of 1.5×10 -11 cm -2 sr -1 sec -1 for magnetic monopoles, 2e/3 quarks, and for e/3 quarks.

A scintillation counter hodoscope for 10 MHz beams

A scintillation counter hodoscope with greater than 10 MHz capability is described. Each hodoscope plane has complete (100%) coverage for 2 cm across the beam, contains elements as small as 1 mm, and interposes only 2 mm of scintillating material into the beam.

Measurement of polarized target asymmetry on γp→ π+n in the third resonance region

The polarized target asymmetry for the process γp→ π +n has been measured for incident photon energies from 0.96 to 1.10 GeV, and pion c.m. production angles between 70 and 160°. π + mesons from a polarized propanediole target were detected by a magnetic spectrometer with scintillation counter hodoscopes. The radiative decay widths of nucleon resonances were found by an amplitude analysis, and are compared with theoretical predictions.

Charged pion production on 12C to discrete final states

The 12C(e,e'π +) 12B and 12C(e,e'π −) 12N reactions to discrete final states of the residual nucleus have been measured with a magnetic spectrometer for a pion kinetic energy of 30 MeV at different angles between 30 and 90° in the lab. The pion detector consists of three scintillation counter hodoscopes, which give a dE dx measurement. Together with three plastic Cerenkovs as veto counters we have a suppression factor against electrons of 5 × 10 −5. Absolute values for d 2σ dΩ π dT π have been obtained through 4 MeV excitation energy of the final nucleus.

Polarimeter System for High-Energy Protons Using Carbon Plate and Liquid Hydrogen

In order to measure recoil proton polarization for the reaction γ+p→π°+p in a wide energy range, a polarimeter system has been constructed using carbon plate and liquid hydrogen as the scatterer. It consists of multi-wire proportional chambers, wire spark chambers, scintillation counter hodoscopes, and scatterers. Carbon plates for lower energy protons and liquid hydrogen for higher-energy protons were used as scatterers. The liquid-hydrogen polarimeter has worked reliably in continuous operation for a long time. The performance of the system in the experiment is described.

Measurement of the polarization of the Λ0 in the reaction γ + p → K + + Λ0 in the resonance region

At the Bonn 2.5 GeV synchrotron the polarization of the Λ 0 was measured at 40° and 90° for three energies. The kaon was detected with a strong focussing magnetic spectrometer and separated from other particles with the help of a differential liquid Čerenkov counter. The polarization was determined by means of the angular distribution of the decay proton which was measured with a combination of sonic spark chambers and a scintillation counter hodoscope. The typical statistical errors are about 13%. The systematic errors add up to 8%.

A LED system to test scintillation counter hodoscopes

A low cost system consisting of GaP green LEDs, pulsing circuitry, and pulse gating is described. This system was used for monitoring and testing in an experiment with 200 scintillation counters.

A Novel Design for a Hodoscope with 1 MM Granularity

A scintillation counter hodoscope with 1 mm granularity using fiber optic light guides was designed for use in a 200-GeV secondary hadron beam. Special care was taken to position the scintillators withhigh accuracy. The efficiency in a beam of 2.5? 106 particles/sec is 98%.

A measurement of the polarization parameter in large angle proton-proton elastic scattering at 7.9 GeV/ c

The polarization parameter in proton-proton elastic scattering has been measured at an incident momentum of 7.9 GeV/ c and four-momentum transfers in the range 0.9 < | t| < 6.5 (GeV/ c) 2 using a high intensity unpolarized proton beam incident on a polarized proton target. The angle and momentum of the forward scattered protons were measured with a magnet spectrometer and scintillation counter hodoscopes and the angle of the recoil proton was measured using similar hodoscopes. A clean separation between the elastic scattering from free hydrogen and that coming from inelastic interactions and from interactions with complex nuclei in the target was obtained. The polarization shows substantial structure rising from zero at | t| = 1.0 (GeV/ c) 2 to a maximum at | t| = 1.7 (GeV/ c) 2 and then falling to zero at | t| = 2.0 (GeV/ c) 2. There is evidence of a further peak at | t| = 2.8 (GeV/ c) 2. Above | t| = 3.25 (GeV/ c) 2 the polarization is small and consistent with zero. A comparison of these data with data obtained at other beam momenta shows that the polarization parameter has a strong momentum dependence.

A novel design for a hodoscope with 1 mm granularity

A scintillation counter hodoscope with 1 mm granularity using fiber optic light guides was designed for use in a 200 GeV secondary hadron beam. Special care was taken to position the scintillators with high accuracy. The efficiency in a beam of 2.5 × 10 6 particles/s is 98%.

Slope of forward elasticπ+pscattering from 4.4 to 6.0 GeV/c

Angular distributions for ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}p$ were measured for 13 incident-pion momenta from 4.4 to 6.0 GeV/c and for $\ensuremath{-}t$ less than \ensuremath{\sim}0.1 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. This experiment was performed at the Zero Gradient Synchrotron of Argonne National Laboratory, where a focusing magnetic spectrometer and a scintillation-counter hodoscope were used. In fitting the angular distributions the strong-interaction contribution was parameterized by an exponential form exp($\mathrm{bt}$); the Coulomb interference was also included. The resulting values of the slope parameter for $|t|&lt;\ensuremath{\sim}0.1$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ are presented for each incident beam momentum.