121337614
Absolute in situ energy calibration of luminosity calorimeters in the DELPHI experiment at LEP
Abstract Methods to perform the absolute energy calibration of DELPHI's Small Angle Tagger luminosity calorimeters at LEP are presented and compared. The input was small angle Bhabha scattering events. A significant nonlinearity in the response of the calorimeters was observed. The conjugate gradient method was applied to solve the least squares problem. This method is particularly useful for least squares problems which are large, ill-behaved or even singular, and for cases with a sparse coefficient matrix.
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.
110508272
Performance of the DELPHI small angle tile calorimeter
The DELPHI STIC detector is a lead-scintillator sampling calorimeter with wavelength shifting optical fibers used for light collection. The main goal of the calorimeter at LEP100 is to measure the luminosity with an accuracy better than 0.1%. The detector has been in operation since the 1994 LEP run. Presented here is the performance measured during the 1994-1995 LEP runs, with the emphasis on the achieved energy and space resolution, the long-term stability and the efficiency of the detector. The new bunch-trains mode of LEP requires a rather sophisticated trigger and timing scheme which is also presented. To control the trigger efficiency and stability of the calorimeter channels, a LED-based monitoring system has been developed.
110699804
The small angle tile calorimeter project in DELPHI
The new Small Angle TIIe Calorimeter (STIC) covers the forward regions in DELPHI. The main motivation for its construction was to achieve a systematic error of 0.1% on the luminosity determination. This detector consists of a “shashlik” type calorimeter, equipped with two planes of silicon pad detectors placed respectively after 4 and 7.4 radiation lengths. A veto counter, composed of two scintillator planes, covers the front of the calorimeter to allow ϱ − γ separation and to provide a neutral energy trigger. The physics motivations for this project, results from extensive testbeam measurements and the performance during the 1994 LEP run are reported here.
64455357
Normalization in DELPHI
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.
118107314
Tunneling beyond the Fermilab site
An accelerator that crosses the Fermilab site boundary must have a minimum effect on the surrounding environment and the people residing in the area. Unobstructed public access should be allowed above the ring except in relatively few areas such as the injection, dump, and experimental regions. The accelerator should be a benign and unobtrusive neighbor not only when it is completed but also in the construction period. For these reasons underground tunneling for all or most of the ring seems attractive. In this note we look into some questions raised by tunneling beyond the Fermilab site. Most of our discussion is of general applicability. However, we will use as examples two specific ring configurations. The examples have not been optimized from the point of view of physics output or accelerator technology but are just specific examples which allow us to study questions of tunneling. One is a ring of 5 km radius (5 TeV) tangent to the Tevatron and entirely east of the Fox River and fed by a beam from the Tevatron which crosses under the river. We assume that each of these machines will have 100 beam fills per year and we scale the maximum intensities with themore » accelerator radii. Thus we assume that there will be 1.0 E14 protons in each beam of the 20 TeV machine and 2.5 E13 for the 5 TeV machine.« less
118676742
Polarized proton and antiproton beams and experiments at the tevatron
A 200 GeV polarized proton (and antiproton) beam and experimental facility will be built as part of the Tevatron II construction program at Fermilab. The beam is being developed by a joint Argonne-Fermilab team. The detector facility for the first experiments using the polarized beam is the responsibility of an Annecy-Argonne-Berkeley-Fermilab-Kyoto-Northwestern-Rice-Sarclay-Serpukhov-Triests collaboration. 1 figure.
123035937
The design and performance of the FNAL high-energy polarized beam facility
We describe a new polarized-proton and -antiproton beam with 185-GeV/c momentum in the Fermilab MP beam line which is currently operational. The design uses the parity-conserving decay of lambda and antilambda hyperons to produce polarized protons and antiprotons, respectively. A beam-transport system minimizes depolarization effects and uses a set of 12 dipole magnets that rotate the beam-particle spin direction. A beam-tagging system determines the momentum and polarization of individual beam particles, allowing a selection of particles in definite intervals at momentum and polarization. We measured polarization of the beam by using two types of polarimeters, which verified the determination of polarization by a beam-particle tagging system. Two of these processes are the inverse-Primakoff effect and the Coulomb-nuclear interference (CNI) in elastic proton-proton scattering. Another experiment measured the {pi}{sup 0} production asymmetry of large-x{sub F} values; this process may now be used as an on-line beam polarimeter. 9 refs., 9 figs.
123415460
Rationale for a Choice of Secondary Particle Beams at NAL
121024091
PROTON-PROTON ELASTIC SCATTERING INVOLVING LARGE MOMENTUM TRANSFERS