16226667
The search for color transparency at 12 GeV
We propose to measure the A(e,e’p) proton knockout and the A(e,e’π) pion electroproduction cross sections to extract the proton and the pion nuclear transparencies in the nuclear medium. We restrict the proton transparency measurements to the C nucleus with additional H measurements (to determine the elementary process), over the range Q = 8 16 (GeV/c). The pion (π) transparency measurements will be performed on H, H, C, and Cu, over the range Q = 5 9.5 (GeV/c). A rise in the pion and proton transparency as a function of Q is predicted to be a signature of the onset of Color Transparency. For the latter measurements, with a less known reaction mechanism, it is essential to map both the Qand A-dependence. Recent experiments have reported evidence for Color Transparency effects at Q ' 10 (GeV/c). This is further corroborated by hints of such effects seen at lower Q in pion photoand electro-production from nuclei. Unambiguous observation of Color Transparency would uniquely point to the role of color in exclusive high-Q processes. In addition, the occurrence of such effects is an effective signature of the approach to the factorization regime in meson electroproduction experiments, necessary for the access to Generalized Parton Distributions. The proposed experiment seeks to measure the pion and proton transparencies up to the highest Q that can easily be reached at a 12-GeV JLab, using the HMS and SHMS spectrometers. We request a total of 26 days of beamtime with a beam current of 80μA.
54739743
The aerogel threshold Cherenkov detector for the High Momentum Spectrometer in Hall C at Jefferson Lab
We describe a new aerogel threshold Cherenkov detector installed in the HMS spectrometer in Hall C at Jefferson Lab. The Hall C experimental program in 2003 required an improved particle identification system for better identification of p=K=p, which was achieved by installing an additional threshold Cherenkov counter. Two types of aerogel with n 1⁄4 1:030 and n 1⁄4 1:015 allow one to reach 10 3 proton and 10 2 kaon rejection in the 1–5GeV/c momentum range with pion detection efficiency better than 99% (97%). The detector response shows no significant position dependence due to a diffuse light collection technique. The diffusion box was equipped with 16 Photonis XP4572 photo multiplier tubes (PMTs). The mean number of photo-electrons in saturation was 16 and 8, respectively. This allows even for separation of slower particles slightly above threshold. r 2005 Elsevier B.V. All rights reserved. PACS: 29.40.Ka; 25.30.Rw
43065058
Pion absorption in light nuclei.
Cross sections have been measured for proton emission following ${\mathrm{\ensuremath{\pi}}}^{+}$ absorption on $^{6}\mathrm{Li}$, $^{7}\mathrm{Li}$, $^{9}\mathrm{Be}$, $^{10}\mathrm{B}$, $^{11}\mathrm{B}$, $^{12}\mathrm{C}$, and $^{13}\mathrm{C}$, for pion kinetic energies of 50, 100, 140, and 180 MeV using a large-solid-angle bismuth germanate detector array.
29593010
Pion absorption above the Delta (1232) resonance.
Two-proton and three-proton inclusive [pi][sup +] absorption cross sections were measured for incident pion energies from 250 to 500 MeV on targets of [sup 12]C, [sup 58]Ni, [sup 90]Zr, [sup 118]Sn, and [sup 208]Pb using a large solid angle bismuth germanate detector array. Pion absorption events leading to three or more protons in the final state were observed to become more significant with increasing incident pion energy and were dominant at 500 MeV. The total absorption cross sections were inferred from analyses of the data with uncertanties of approximately 25%.
119878792
Measurement of the ratio of the proton's electric to magnetic form factors by recoil polarization
The longitudinal and transverse polarizations of the outgoing proton were measured for the reaction {sup 1}H(e,e' p) at four-momentum transfer squared of 0.5 to 3.5 GeV{sup 2}. The ratio of the electric to magnetic form factors of the proton is proportional to the ratio of the transverse to longitudinal polarizations.
118914530
Measurement of Analyzing Powers for Polarized Proton Scattering on CH2 Target at Proton Momentum Range from 1.75 to 5.3 GeV/c
We report a new measurement of analyzing powers for the reaction p + CH2 → one charged particle +X, at proton momenta of 1.75, 3.8, 4.5 and 5.3 GeV/c. These results extend the existing data basis, necessary for proton polarimetry at intermediate energy, and confirm the feasibility of an extended polarimeter based on this process. The experiment is performed at the accelerator complex of the JINR‐LHE (Dubna).
204013563
KEKB beam collision stability at the picosecond timing and micron position resolution as observed with the Belle detector
Using the Belle detector we study the characteristics of beam collisions at the KEKB 3.5 GeV e+ on 8 GeV e− asymmetric energy collider. We investigate the collision timing tIP and its z-coordinate along the beam axis zIP as a function of the position of the colliding bunch in a beam train. The various tIP and zIP behaviors observed by Belle are attributed to beam loading effects in the radio frequency cavities that accelerate the beams with a beam abort gap. We report these results in detail and discuss the prospects for the SuperKEKB collider.
121659740
The CDF level 2 calorimetric trigger upgrade
Abstract CDF II upgraded the calorimeter trigger to cope with the higher detector occupancy due to the increased Tevatron instantaneous luminosity ( ∼ 2.8 × 10 32 cm - 2 s - 1 ) . While the original system was implemented in custom hardware and provided to the L2 trigger a limited-quality jet clustering performed using a reduced resolution measurement of the transverse energy in the calorimeter trigger towers, the upgraded system provides offline-quality jet reconstruction of the full resolution calorimeter data. This allows to keep better under control the dependence of the trigger rates on the instantaneous luminosity and to improve the efficiency and purity of the trigger selections. The upgraded calorimeter trigger uses the general purpose VME board Pulsar, developed at CDF II and already widely used to upgrade the L2 tracking and L2 decision systems. A battery of Pulsars is used to merge and send the calorimeter data to the L2 CPUs, where software-implemented algorithms perform offline-like clustering. In this paper we review the design and the performance of the upgraded system.
120460046
K0 Phenomena Associated with Neutrino Induced mu- e+ Events.
Using the Fermilab 15-ft neon-hydrogen bubble chamber we have identified seventeen events of the type ..nu../sub ..mu../N ..-->.. ..mu../sup -/e/sup +/X. The ratio of the production of these events to ordinary neutrino charged-current events is (7.7 +- 3.0) x 10/sup -3/ for positron energy greater than 800 MeV and neutrino energy greater than 10 GeV. Associated with these seventeen events are 11 V's, of which eight fit K/sub s//sup 0/ ..-->.. ..pi../sup +/..pi../sup -/ and three fit K/sub s//sup 0/ ..-->.. ..pi../sup +/..pi../sup -/ and ..lambda.. ..-->.. p..pi../sup -/ ambiguously. The average K/sup 0/ multiplicity per ..mu../sup -/e/sup +/ event is determined to be 1.84/sup +0.63//sub -0.53/.
117932304
Tevatron bunch length studies at CDF
A luminous interaction region can be described by the distribution in (x, y, z) over which p{bar p} interactions are observed in a detector. The spatial size of this distribution can be written in terms of expressions that involve only combinations of the proton and anti-proton bunch sizes. Hence, it is not possible to determine the sizes of the proton and anti-proton bunches independently by fitting the distribution of (x, y, z) from the recorded events. If, in addition to the coordinates (x, y, z) at which p{bar p} interactions occur, the times at which the interactions took place are also measured, then it becomes possible to measure the lengths of the proton and anti-proton bunches separately. This sensitivity is due to a correlation between z and t that arises from the fact that the proton and anti-proton bunches travel in opposite directions. The derivation presented in section 2 quantifies this correlation, resulting in an expression for the probability density as a function of z and t for p{bar p} interactions. By fitting the distributions observed at CDF using this model, we measure the lengths of the proton and anti-proton bunches at times throughout several Tevatron stores. From this analysismore » the evolution of the bunch lengths can be studied. We attempt to correlate these with other measures of the bunch length obtained using different experimental techniques.« less
54789766
CONTROL OF THE GEOMETRICAL CONFORMITY OF THE LHC INSTALLATION WITH A SINGLE LASER SOURCE
A large and complex accelerator like LHC machine needs to integrate several thousand different components in a relatively limited space. During the installation, those components are installed in successive phases, always aiming to leave the necessary space available for the equipment which will follow. To help ensure the correct conditions for the installation, the survey team uses a laser scanner to measure specific areas and provides this data, merged together in a known reference system, to the integration team who compare the results with the 3D CAD models. This paper describes the tools and software used to rebuild underground zones in the CATIA environment, to check interferences or geometrical non conformities, as well as the procedures defined to solve the identified problems.