118761805
Measurements of helicity sensitive quantities and Rb from SLD
16601897
Mechanisms affecting performance of the BaBar resistive plate chambers and searches for remediation
The BaBar experiment at PEPII relies on the instrumentation of the flux return (IFR) for both muon identification and KL detection. The active detector is composed of resistive plate chambers (RPCs) operated in streamer mode. Since the start of operation the RPCs have suffered persistent efficiency deterioration and dark current increase problems. The ‘‘autopsy’’ of bad BaBar RPCs revealed that in many cases uncured linseed oil droplets had formed on the inner surface of the Bakelite plates, leading to current paths from oil ‘‘stalagmites’’ bridging the 2mm gap. In this paper, a possible model of this ‘‘stalagmite’’ formation and its effect on the dark current and efficiency of RPC chambers is presented. Laboratory test results strongly support this model. ARTICLE IN PRESS *Corresponding author. Tel.: +1-609-258-4391; fax: +1-609-258-6360. E-mail address: changguo@princeton.edu (C. Lu). 0168-9002/03/$ see front matter r 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-9002(03)01292-0 Based upon this model we are searching for solutions to eliminate the unfavorable effect of the oil stalagmites. The lab tests show that the stalagmite resistivity increases dramatically if exposed to the air, an observation that points to a possible way to remedy the damage and increase the efficiency. We have seen that flowing an oxygen gas mixture into the chamber helps to polymerize the uncured linseed oil. Consequently, the resistivity of the bridged oil stalagmites increases, as does that of the oil coating on the frame edges and spacers, significantly reducing the RPC dark currents and low-efficiency regions. We have tested this idea on two chambers removed from BaBar because of their low efficiency and high dark current. These test results are reported in the paper, and two other remediation methods also mentioned. We continue to study this problem, and try to find new treatments with permanent improvement. r 2003 Elsevier Science B.V. All rights reserved.
124136703
Improved Constraints on the Neutralino Cold Dark Matter Candidate from the Search for Chargino and Neutralino Production Using the OPAL Detector at 170 ÷ 172 Gev at LEP
New limits on the cold dark matter candidate, the lightest neutralino \(\left( {\tilde x_1^0} \right)\), are obtained from a search for charginos and neutralinos using a data sample of 10.3 pb−1 at the center-of-mass energies of √s =170 and 172 GeV with the OPAL detector at LEP.
120601772
Validating Geant4 Versions 7.1 and 8.3 Against 6.1 for BaBar
Since 2005 and 2006, respectively, Geant4 versions 7.1 and 8.3 have been available, providing: improvements in modeling of multiple scattering; corrections to muon ionization and improved MIP signature; widening of the core of electromagnetic shower shape profiles; newer implementation of elastic scattering for hadronic processes; detailed implementation of Bertini cascade model for kaons and lambdas, and updated hadronic cross-sections from calorimeter beam tests. The effects of these changes in simulation are studied in terms of closer agreement of simulation using Geant4 versions 7.1 and 8.3 as compared to Geant4 version 6.1 with respect to data distributions of: the hit residuals of tracks in BABAR silicon vertex tracker; the photon and KOL shower shapes in the electromagnetic calorimeter; the ratio of energy deposited in the electromagnetic calorimeter and the flux return of the magnet instrumented with a muon detection system composed of resistive plate chambers and limited-streamer tubes; and the muon identification efficiency in the muon detector system of the BaBar detector.
120215204
Monolithic CMOS pixel detector for international linear collider vertex detection
A monolithic CMS pixel detector is under development for an ILC experiment. This chronopixel array provides a time stamp resolution of one bunch crossing, a critical feature for background suppression. The status of this effort is summarized.
118033184
Status of the Compact Muon Solenoid Detector at the Large Hadron Collider
The Compact Muon Solenoid (CMS) detector is being constructed at the Large Hadron Collider (LHC) at CERN for the purpose of exploring new physics in proton‐proton collisions at 14 TeV. The detector is to be designed, constructed and commissioned in time for the start of the LHC in April 2007. This article summarizes the current status of the detector and foreseen program for completion.
117806093
Preliminary Polarization Results at Fermilab Energies
This paper describes the jet target, the superconducting spectrometer and the polarimeter used to measure the recoil proton polarization in an Indiana University experiment at the Fermi National Accelerator Laboratory. Analysis procedures and data checks are explained and preliminary results are presented and compared with model predictions. The future plans of the experiment are also discussed.
117216202
A Study of Inclusive Proton Polarization
The authors propose to measure the polarization of the outgoing proton in the inclusive reaction p + p {yields} p {up_arrow} + X in the region .98 > x{sub R} > .6. The measurements would include beam momenta from p{sub LAB} = 50 GeV/c to p{sub LAB} = 400 GeV/c at t = -.3 (GeV/c){sup 2}, -.8 (GeV/c){sup 2}, -1.4 (GeV/c){sup 2}, and -3.0 (GeV/c){sup 2} over the range .6 < x{sub F} < .95. The experiment would use the existing E313 polarimeter and internal target spectrometer.
122604408
Measurement of the Depolarization Parameter in Elastic Proton Proton Scattering at 3 and 6-GeV/c
Results are presented from an experiment designed to make the first systematic study of the depolarization parameter in elastic proton--proton scattering at high energies. Measurements were made at 3.0 and 6.0 GeV/c at abs. value t values extending to 1.7 (GeV/c)2 at the higher momentum. A high- intensity unpolarized proton beam was incident on a polarized proton target and the polarization of the elastically scattered recoil protons was determined with a carbon analyzer. The results are discussed in the framework of optical and exchange models.
115209317
Advances in the Study of Spin Effects in Nucleon-Nucleon Scattering at Small and Intermediate Momentum Transfers
There has been remarkable progress made in the field of high energy physics in the past five years. We have recently witnessed the discovery of new quantum numbers, the spectra of particles associated with these quantum numbers, and a much improved understanding of the role that all quantum numbers play in high energy interactions. With the wide assortment of experiments and studies being conducted in high energy physics at any one time, it is very easy for one to get the impression that, the activity in the field is highly unfocused. On the one hand, it is precisely this apparent unfocused nature that has given rise to much of the excitement and richness of the field. On the other hand, as one examines the situation more closely, one finds that much of the effort in the field is indeed directed toward the solution of a few central problems. One of these problems which I will continually refer to today is that of understanding the details of the structure of the elementary particles. This problem—one of the most fascinating and most difficult problems ever tackled by man-can be approached from several different angles.
122492733
Proton polarization in inclusive processes at 100, 200, 300, and 400 GeV
We have measured the polarization of the out going proton in the following high energy interactions: p+C..-->..p/sup arrow-up/+x and p+p..-->..pup-arrow+x. Our measurements span the P/sub T/ range .5..-->..1.5 GeV/c energies of 100, 200, 300, 400 GeV at the internal target area at Fermi National Accelerator Laboratory.