Bates Large Acceptance Spectrometer Toroid Research Articles

Measurement of the Vector and Tensor Asymmetries at Large Missing Momentum in Quasielastic (e[over →],e^{'}p) Electron Scattering from Deuterium.

We report the measurement of the beam-vector and tensor asymmetries A_{ed}^{V} and A_{d}^{T} in quasielastic (e[over →],e^{'}p) electrodisintegration of the deuteron at the MIT-Bates Linear Accelerator Center up to missing momentum of 500 MeV/c. Data were collected simultaneously over a momentum transfer range 0.1<Q^{2}<0.5 (GeV/c)^{2} with the Bates Large Acceptance Spectrometer Toroid using an internal deuterium gas target polarized sequentially in both vector and tensor states. The data are compared with calculations. The beam-vector asymmetry A_{ed}^{V} is found to be directly sensitive to the D-wave component of the deuteron and has a zero crossing at a missing momentum of about 320 MeV/c, as predicted. The tensor asymmetry A_{d}^{T} at large missing momentum is found to be dominated by the influence of the tensor force in the neutron-proton final-state interaction. The new data provide a strong constraint on theoretical models.

Aerogel Efficiencies of Threshold Cherenkov Counters

We present the aerogel efficiencies of the Cherenkov counters used as a sub-component of Bates large acceptance spectrometer toroid. The events of the elastic channel of electron–proton scattering from hydrogen is utilized. The counters’ aerogel efficiencies change between (91.5 \({\pm}\) 0.3) and (98.6 \({\pm}\) 0.6) % based on a time-of-flight scintillation paddle. In addition, up to ~7 % variation in the local efficiencies per paddle is attributable to statistical fluctuations and no local inefficient aerogel pockets are encountered.

Precise Measurement of Deuteron Tensor Analyzing Powers with BLAST

We report a precision measurement of the deuteron tensor analyzing powers T(20) and T(21) at the MIT-Bates Linear Accelerator Center. Data were collected simultaneously over a momentum transfer range Q=2.15-4.50 fm(-1) with the Bates Large Acceptance Spectrometer Toroid using a highly polarized deuterium internal gas target. The data are in excellent agreement with calculations in a framework of effective field theory. The deuteron charge monopole and quadrupole form factors G(C) and G(Q) were separated with improved precision, and the location of the first node of G(C) was confirmed at Q=4.19±0.05 fm(-1). The new data provide a strong constraint on theoretical models in a momentum transfer range covering the minimum of T(20) and the first node of G(C).

Spin-Dependent Electron Scattering from Polarized Protons and Deuterons with the BLAST Experiment at MIT-Bates

The Bates Large Acceptance Spectrometer Toroid (BLAST) experiment was operated at the MIT-Bates Linear Accelerator Center from 2003 until 2005. The experiment was designed to exploit the power of a polarized electron beam incident on polarized targets of hydrogen and deuterium to measure, in a systematic manner, the neutron, proton, and deuteron form factors as well as other aspects of the electromagnetic interaction on few-nucleon systems. We briefly describe the experiment, and present and discuss the numerous results obtained.

THE BLAST EXPERIMENT: POLARIZED ELECTRON SCATTERING FROM HYDROGEN AND DEUTERIUM

At the MIT-Bates Linear Accelerator Center, the nucleon form factors have been measured by scattering polarized electrons from vector-polarized hydrogen and deuterium. The experiment used the longitudinally polarized electron beam stored in the MIT-Bates South Hall Ring along with an isotopically pure, highly vector-polarized internal atomic hydrogen and deuterium target provided by an atomic beam source. The measurements were carried out with the symmetric Bates Large Acceptance Spectrometer Toroid (BLAST). Results are presented for the proton form factor ratio, [Formula: see text], and for the charge form factor of the neutron, [Formula: see text]. Both results are more precise than previous data in the corresponding Q2 ranges.

The BLAST experiment

The Bates large acceptance spectrometer toroid (BLAST) experiment was operated at the MIT-Bates Linear Accelerator Center from 2003 until 2005. The detector and experimental program were designed to study, in a systematic manner, the spin-dependent electromagnetic interaction in few-nucleon systems. As such the data will provide improved measurements for neutron, proton, and deuteron form factors. The data will also allow details of the reaction mechanism, such as the role of final state interactions, pion production, and resonances to be studied. The experiment used: a longitudinally polarized electron beam stored in the South Hall Storage Ring; a highly polarized, isotopically pure, internal gas target of hydrogen or deuterium provided by an atomic beam source; and a symmetric, general purpose detector based on a toroidal spectrometer with tracking, time-of-flight, Cherenkov, and neutron detectors. Details of the experiment and operation are presented.

NEW RESULTS FROM THE BATES LARGE ACCEPTANCE SPECTROMETER TOROID (BLAST)

An experiment using the novel technique of scattering a longitudinally polarized electron beam from polarized internal hydrogen/deuterium gas targets was carried out in the South Hall Ring at the MIT-Bates Accelerator Center. The scattered particles were detected by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The proton electric to magnetic form factor ratio, [Formula: see text] at Q 2 = 0.1 - 0.65 ( GeV/c )2 has been determined from the experiment by measuring the spin-dependent ep elastic scattering asymmetry in the two symmetric sectors of the BLAST simultaneously for the first time. The neutron electric form factor [Formula: see text] in the same Q2 range has been extracted by measuring the spin-dependent asymmetry from the [Formula: see text] process with a vector polarized deuterium target. These results on the nucleon form factors from the BLAST experiment are presented.

Magnetic field measurements of the BLAST spectrometer

The Bates Large Acceptance Spectrometer Toroid has been built to study nuclear physics reactions using a stored, polarized electron beam and a variety of polarized targets internal to the storage ring. The spectrometer consists of eight coils surrounding the target cell. There is a requirement of nominally zero field along the centerline of the spectrometer for proper electron beam storage. In addition, the polarized internal targets require a low field gradient in the target region. Magnetic field measurements were made near the beam centerline to guide the alignment of the coils and satisfy the field magnitude and gradient requirements. After the coils were aligned, the magnetic field was measured in the detector regions to provide information for particle tracking.

Charge Form Factor of the Neutron at Low Momentum Transfer from theH→2(e→,e′n)H1Reaction

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio GEn/GMn was extracted from the beam-target vector asymmetry AedV at four-momentum transfers Q2=0.14, 0.20, 0.29, and 0.42 (GeV/c)2.Received 26 March 2008DOI:https://doi.org/10.1103/PhysRevLett.101.042501©2008 American Physical Society

Nucleon form factors and the BLAST experiment

Measurements of the charge and magnetic form factors of the nucleon present a sensitive test of nucleon models and QCD-inspired theories. A precise knowledge of the neutron form factors at low Q 2 is also essential to reduce the systematic errors of parity-violation experiments. At the MIT-Bates Linear Accelerator Center, the nucleon form factors have been measured by means of scattering of polarized electrons from vector-polarized hydrogen and deuterium. The experiment used the longitudinally polarized stored electron beam of the MIT-Bates South Hall Ring along with an isotopically pure, highly vector-polarized internal atomic hydrogen and deuterium target provided by an atomic beam source. The measurements have been carried out with the symmetric Bates Large-Acceptance Spectrometer Toroid (BLAST) with enhanced neutron detection capability.

The BLAST Cherenkov detectors

We report on the design, construction, and operation of a large array of diffusely reflective aerogel Cherenkov detectors. They are part of the detector instrumentation of the Bates Large Acceptance Spectrometer Toroid (BLAST) at the MIT-Bates Linear Accelerator Center. The Cherenkov detectors are used for particle identification. They are able to discriminate between pions and electrons with momenta up to 700 MeV/ c.

Recent Results from BLAST

The Bates Large Acceptance Spectrometer Toroid experiment, BLAST, at the MIT-Bates Linear Accelerator Laboratory is designed to study in a systematic manner the spindependent electromagnetic interaction in few-nucleon systems at momentum transfers below 1 GeV/c. Utilizing a polarized electron beam, highly polarized internal gas targets of H and D, and a symmetric detector configuration, BLAST is able to make simultaneous measurements of several reaction channels for different combinations of beam helicity and target polarization (vector for H, both vector and tensor for D). BLAST will provide new data on the nucleon and deuteron form factors as well as study few body physics and pion production. Preliminary results are presented.

The MIT-Bates large acceptance spectrometer toroid

The Bates Large Acceptance Spectrometer Toroid (BLAST) is a detector designed to study the spin-dependent electromagnetic response of few-body nuclei at momentum transfers up to 1 (GeV/c) 2 at the MIT-Bates Linear Accelerator Center's South Hall Ring (SHR). The BLAST detector consists of an eight-sector copper coil array producing a toroidal magnetic field, instrumented with two opposing wedge-shaped sectors of wire chambers, scintillation detectors, Cerenkov counters, neutron detectors, a lead-glass forward calorimeter, and recoil detectors. A status of the project is presented as well as highlights of the scientific program.

The BLAST project at MIT-Bates

The Bates Large Acceptance Spectrometer Toroid (BLAST) is a detector designed to study the spin-dependent electromagnetic response of few-body nuclei at momentum transfers up to 1 (GeV/c)2 at the MIT/Bates Linear Accelerator Center's South Hall Ring (SHR). The BLAST detector consists of an eight-sector copper coil array producing a toroidal magnetic field, instrumented with two opposing wedge-shaped sectors of wire chambers, scintillation detectors, Cerenkov counters, neutron detectors, a lead-glass forward calorimeter, and recoil detectors. A status of the project is presented as well as highlights of the scientific program.

Intermediate energy nuclear physics at MIT-Bates

The MIT-Bates Linear Accelerator Center is a university-based laboratory carrying out frontier research in nuclear physics. The research program is focussed on the flavor structure, charge distribution, shape, size and polarizability of the nucleon; the spin and electromagnetic structure of light nuclei; and the origin of the elements. The Bates research program has three central thrusts: the SAMPLE experiments to probe the flavor structure of the proton using parity-violating electron scattering at back angles; the OOPS (Out-Of-plane Spectrometer System) program which uses out-of-plane detection to probe nucleon and few-body nuclear structure; and the BLAST (Bates Large Acceptance Spectrometer Toroid) program which will use a new spectrometer under construction to measure electron scattering from internal gas targets in the South Hall Ring.

Status of the BLAST project

The Bates Large Acceptance Spectrometer Toroid (BLAST) is a detector designed to study the spin-dependent electromagnetic response of few-body nuclei at momentum transfers up to 1 (GeV/c)2 at the MIT/Bates Linear Accelerator Center's South Hall Ring (SHR). The BLAST detector consists of an eight-sector copper coil array producing a toroidal magnetic field, instrumented with two opposing wedge-shaped sectors of wire chambers, scintillation detectors, Cerenkov counters, neutron detectors, a lead-glass fo ward calorimeter, and recoil detectors. Presently, BLAST is under construction and it is on schedule to be done in summer 2001. A status of the project is presented as well as highlights of the scientific program.

The MIT-Bates out-of-plane and polarized internal target programs

The OOPS and BLAST projects are the main thrusts to the research program at MIT-Bates for the next few years. The OOPS system is a unique facility of multiple magnetic spectrometers specifically designed for accurate extraction of the five response functions accessible through the (e,e′p) reaction with polarized beam. Results from the initial round of experiments are presented as well as a brief out-look into the upcoming measurements. The Bates Large Acceptance Spectrometer Toroid (BLAST) is a detector designed to study in a comprehensive and precise way the spin dependent electromagnetic response of few-body nuclei. At present BLAST is under construction and a brief status is presented as well as projected results for some of the key experiments.