He Mao

Results from the E-705 electromagnetic shower position detector

A fine-grain hodoscope to measure the position of showers in the outer (>52 cm) region of the E-705 electromagnetic calorimeter is described. The hodoscope is constructed with two layers of vertical conducting plastic tubes for the X position measurement of showers. Y position measurement of showers was accomplished by cathode-induced horizontal strips. A 50/50-ethane mixture bubbled through isopropyl alcohol at 0 degrees C was circulated through the tubes in parallel. The tubes were operated at +1.925 kV on the wire (below the region of saturated avalanche) in the limited proportionality mode. The hodoscope is described, and results are presented for the position resolution, shower width, and charge detected as a function of calibration electron energy. >

Performance of a lead radiator, gas tube calorimeter

The design and performance of a 4.2-radiation-length, lead-sandwich, gas tube hodoscope are discussed. The device, measuring 1*2 m/sup 2/ in area and 12 cm in depth, was used in Fermi National Accelerator Laboratory experiment 705. Multiple samplings of anode wires situated within three-walled aluminum tubes were used to generate an X coordinate; similarly, capacitively coupled copper-clad strips were ganged together to yield a Y coordinate. The results reviewed of an analysis of electron calibration data taken during a recent six-month running period are reviewed. The position resolution (in millimeters) is seen to be 0.8+3.3/ square root E+31/E for the 9.92 mm-spaced wires and 0.6+3.2/ square root E+32 for the 12.5-mm strips, where E represents the electron beam energy in GeV. The correlation between energy as measured by the wires and energy as measured by the strips is fairly tight, with an asymmetry RMS (root mean square) for 30-GeV electrons of about 4%. >

An on-line trigger processor for large transverse energy events

A trigger processor for the selection of events in which photons of large transverse momentum are detected by a lead and scintillating glass calorimeter was designed, constructed, and operated at interaction rates ranging from 2 kHz to 2 MHz. The system achieved suppressions of the raw interaction rate of as much as 1*10/sup -5/. Raw distributions of transverse momenta and direct photon event sensitivities are presented for data taken with 300-GeV/c pion and proton beams on a lithium target. >

Precision charge amplification and digitization system for a scintillating and lead glass array

A 544-channel low-noise, high-rate precision charge-amplification and ADC (analog/digital converter) system was constructed for the Fermilab Experiment 705 electromagnetic calorimeter, which uses SCG1-C scintillating glass and SF5 lead glass instrumented with photomultiplier tubes. A general discussion of the system is given, and the charge amplification, fast-trigger-pulse generation, and analog/digital conversion aspects of the system are presented in more detail. Performance is evaluated using data from Experiment 705 and from offline tests. Short- and long-term pedestal stability, baseline recovery and rate capability, linearity of response, and crosstalk between channels are discussed. >

A large aperture spectrometer at Fermilab to study high mass dimuons

A large acceptance forward spectrometer located in a unique antiproton enriched beam has been used at Fermi National Accelerator Laboratory by Experiment 537 to study the production of high mass muon pairs. When the beam was operated at a momentum of 125 GeV/c, it had a flux of 1.5 × 107 particles per second of which 18% were antiprotons. The spectrometer was of closed geometry design and used drift chambers as the tracking elements. Operating over a relatively short period, the experiment accumulated the largest sample of antiproton-induced high mass dimuons of any experiment to date. The contamination of this data by pion-induced dimuons was less than 0.5%.

An updated search of steady TeV γ-ray point sources in northern hemisphere using the Tibet air shower array*

Using the data taken from Tibet II High Density (HD) Array (1997 February1999 September) and Tibet-III array (1999 November-2005 November), our previous northern sky survey for TeV γ−ray point sources has now been updated by a factor of 2.8 improved statistics. From 0.0 to 60.0 in declination (Dec) range, no new TeV γ−ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV γ−ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits. Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China. Department of Physics, Hebei Normal University, Shijiazhuang 050016, China. Department of Mathematics and Physics, Tibet University, Lhasa 850000, China. Department of Physics, Shandong University, Jinan 250100, China. Institute of Modern Physics, Southwest Jiaotong University, Chengdu 610031, China. Department of Physics, Yunnan University, Kunming 650091, China. National Center for Space Weather, China Meteorological Administration, Beijing 100081, China. Physics Department and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China. Center of Space Science and Application Research, Chinese Academy of Sciences, Beijing 100080, China.Using the data taken from Tibet II High Density (HD) Array (1997 February–1999 September) and Tibet-III array (1999 November–2005 November), our previous northern sky survey for TeV γ-ray point sources has now been updated by a factor of 2.8 improved statistics. From 0.0° to 60.0° in declination (Dec) range, no new TeV γ-ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV γ-ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits.

Phenomenon of Energy Concentration in High-Energy Family Events of Cosmic Rays

The phenomenon of energy concentration in high-energy family events of cosmic rays is studied by comparing the results of family events of total visible energies 100-400 TeV observed in the Kanbala emulsion chamber experiment with the Monte Carlo simulation data. The simulation is made by the program CORSIKA in which QGSJET is applied as the hadronic interaction model, and the chemical composition of primary cosmic rays is obtained from the rigidity-cut model and the extrapolation of new results of direct measurements. This shows that the whole distribution tendency of the rate of energy concentration of simulated family events is basically consistent with that of the experiment.

Expectations for Direct Photon Physics from Fermilab Experiment E705

The E705 scintillation glass/lead glass electromagnetic calorimeter is described. The trigger used for recording high transverse momentum direct photon signals from 300 GeV/c π−, π+, \(\bar{p} \), p interactions in a Li7 target is explained. Preliminary results on the response of this direct photon trigger and electromagnetic calorimeter and expected event sensitivities are presented.