53129380
Ground-water activation from the upcoming operation of MI40 beam absorber
During the course of normal operation, a particle accelerator can produce radionuclides in the adjacent soil and in the beam line elements through the interactions of accelerated particles and/or secondary particles produced in the beam absorbers, targets, and sometimes elsewhere through routine beam losses. The production and concentration of these radionuclides depends on the beam parameters such as energy, intensity, particle type, and target configuration. The radionuclides produced in the soil can potentially migrate to the ground water. Soil activation and migration to the ground water depends on the details of the local hydrogeology. Generally, very few places such as the beam stops, target stations, injection and extraction sectors can have high enough radiation fields to produce radionuclides in the soil outside the enclosures. During the design, construction, or an upgrade in the intensity of existing beams, measures are taken to minimize the production of activated soil. The only leachable radionuclides known to be produced in the Fermilab soil are {sup 3}H, {sup 7}Be , {sup 22}Na, {sup 45}Ca and {sup 54}Mn and it has been determined that only {sup 3}H, and {sup 22}Na, because of their longer half lives and greater leachabilities, may significantly impact ground water resources.In themore » past, Fermilab has developed and used the Single Resident Well Model (SRWM) to estimate the ground water activation. Recently, the Concentration Model (CM), a more realistic method which depends on the site hydrogeology has been developed to decide the shielding requirements of the high radiation sites, and to calculate the ground water activation and its subsequent migration to the aquifer. In this report, the concentration of radionuclide released to the surface waters and the aquifer around the MI40 beam absorber are calculated. Subsequently, the ultimate limit on the primary proton beam intensity to be aborted on the Main Injector beam absorber is determined.« less
123662576
Observation of a likely example of the decay of a charmed particle produced in a high energy neutrino interaction
Abstract In a study of neutrino interactions occurring in nuclear emulsion, an event has been found that is most readily interpreted as the decay of a charmed particle with lifetime a few times 10 −13 s.
126003037
The Meson Area at 1000-GeV
125702680
Some Highlights in Elementary Particle Physics in 1969
122023821
Measurement of the double-spin asymmetry ALL for inclusive multi-γ pair production with 200 GeV/c polarized proton beam and polarized proton target
The invariant double-differential cross section, E1E2d6 delta/dp(1)3dp(2)3, and the double-spin asymmetry, A(LL), for inclusive multi-gamma pair production in which gamma-rays came from neutral mesons were measured with a 200 GeV/c longitudinally-polarized proton beam and a longitudinally-polarized proton target. Most of the multi-gamma pairs comes from two-jet type events which are sensitive to partonic interaction. The A(LL) values were found to be consistent with zero. The invariant double-differential cross section for inclusive pi0pi0 production was also measured. These measured cross sections are consistent with LUND Monte Carlo simulations. Using the LUND Monte Carlo simulation package with the Carlitz-Kaur model of spin dependent distribution functions of valence quarks, the A(LL) values have been compared with theoretical predictions of gluon polarization, DELTAG/G. The results put restrictions on the size of DELTAG/G in the region of 0.05 less-than-or-similar-to x less-than-or-similar-to 0.35.
124083721
SOME ASPECTS OF TARGETING SYSTEMS FOR A SLOW EXTRACTED BEAM AT THE AGS.
123179979
The discovery and measurements of a Higgs boson
The discovery of a Higgs-like boson with a mass of approximately 125?GeV by the ATLAS and CMS experiments at the Large Hadron Collider was announced at CERN on 4 July 2012. The data-set of 5?fb?1 of proton?proton collisions with collected during 2011 and 6?fb?1 with collected in 2012 up to the July discovery was supplemented by an additional 15?fb?1 of data with collected during the rest of 2012. The measurements of the properties of the new boson with the combined data-set have substantially strengthened the evidence that this new particle is indeed the Higgs boson predicted to exist as a consequence of the Brout?Englert?Higgs-mechanism that takes responsibility for generating masses of fundamental particles and for the electroweak symmetry breaking.
35536172
In-orbit performance of the EPIC-MOS detectors on XMM-Newton
XMM-Newton was launched into space on a highly eccentric 48 hour orbit on December 10th 1999. XMM-Newton is now in its fifth year of operation and has been an outstanding success, observing the Cosmos with imaging, spectroscopy and timing capabilities in the X-ray and optical wavebands. The EPIC-MOS CCD X-ray detectors comprise two out of three of the focal plane instruments on XMM-Newton. In this paper we discuss key aspects of the current status and performance history of the charge transfer ineffiency (CTI), energy resolution and spectral redistribution function (rmf) of EPIC-MOS in its fifth year of operation.
123487894
The small angle tile calorimeter in the DELPHI experiment
Abstract The Small angle TIle Calorimeter (STIC) provides calorimetric coverage in the very forward region of the DELPHI experiment at the CERN LEP collider. The structure of the calorimeters, built with a so-called “shashlik” technique, gives a perfectly hermetic calorimeter and still allows for the insertion of tracking detectors within the sampling structure to measure the direction of the showering particle. A charged-particle veto system, composed of two scintillator layers, makes it possible to trigger on single photon events and provides e–γ separation. Results are presented from the extensive studies of these detectors in the CERN testbeams prior of installation and of the detector performance at LEP.
121947981
Modified frequentist analysis of search results (The CL(s) method)
The statistical analysis of direct Higgs searches at LEP is described. The likelihood ratio with respect to the background-only hypothesis (or a related teststatistic) is used to order experimental results. The ratio of the confidences in the signal+background to background hypotheses, so-called “CLs”, is used to set lower bounds on the Higgs boson mass. The excluded mass interval which results has an untraditional but useful interpretation which differs both from frequentist intervals which require coverage and from Bayesian credible intervals. Issues such as flip-flopping, experimental uncertainties, discovery significance and the transition to measurement are discussed. The interpretation of results of searches for new particles and phenomena near the sensitivity limit of an experiment is a common problem in particle physics. The loss of sensitivity may be due to a combination of small signal rates, the presence of background comparable to the expected signal, and the loss of discrimination between two models due to insufficient experimental resolution. The search for Higgs bosons at LEP is such an experiment. The LEP experiments have separately, and in collaboration through the LEP working group for Higgs boson searches, developed a nearly common strategy for carrying out and reporting the results of their direct searches. For the time being no significant evidence of Higgs production at LEP has been observed and lower bounds on Higgs masses have been reported. In this report I hope to explain how the lower bound is derived with the so-called CLs method, why this method is used, and how to interpret the result. Since the SM Higgs search has the lowest number of free parameters (1) it will be used to illustrate the features of the CLs method. The generalization to models with several parameters (e.g. the MSSM) is straightforward if more time-consuming in practice. The techniques described in this talk are in fact successfully used in general scans over the many-parameter space of the MSSM in searches for the h and A neutral bosons, in 2-parameter searches for charged Higgs bosons of a general 2-doublet Higgs model, and in combined searches for sparticles by the LEP working group for SUSY particle searches. The individual LEP experiments use either the likelihood ratio, a close approximation of the likelihood ratio, or the integral of the likelihood function as their test-statistics in Higgs searches. Exhaustive studies [1] have shown that they have similar performances for exclusion. To simplify my presentation I only described the likelihood ratio and I will do the same here. I will also show how the CLs method can be applied in other contexts with an example of a hypothetical search for new physics via deviations of a parameter which is measured with normal-distributed uncertainty.
12181544
PROTOTYPE TESTS FOR A VERTEX CHAMBER
We describe the design parameters for a pressurized drift chamber under construction for use with the MAC detector at PEP to operate within 3 cm of the beam line. The chamber is constructed of 7 mm diameter tubes of aluminized mylar with wall thickness of 0.10 mm. The tracking device incorporating these tubes is particularly simple to construct and can be configured so that any malfunctioning tube cau be remotely disconnected without affecting overall og erations. Resolution studies made in a SLAC test beam with a prototype over a wide range of gases and operating conditions are reported. The resolutions obtained were in the 10-40 micron range. It was found that the chamber could be operated satisfactorily, using heavily quenched gases, at high pressures (~4 atm) and operating voltages of ~4 kV in a mode for which saturated streamers were initiated with high efficiency by single electrons. Single electron gains for this mode were -108. The streamers were confined to a region of the wire with dimension of the order of a few hundred microns and count rates in excess of lo4 Hz/cm could be sustained with low dead-times. Further studies are in progress on chamber lifetimes with a variety of gas Elliogs. For our specific application this is of particular importance as the vertex chamber is expected to run in regions of high radiation backgrounds. As was expected for a chamber with extended cathodes, lifetimes were good. Actual lifetimes observed to date with our tube configurations have ranged from 0.05 coul/cm integrated current on the anode for 50:50 argon-isobutane to ~1 coul/cm for a mix of 49% A: 50% CO2: 1% C&. The results of these tests show our design goals to be achievable. Additionally they provide a basis on which to design high precision tracking devices particularly in applications where the device is to be operated in regions of difficult physical access or high ambient radiation levels.