3,769 research outputs found
Enhancing the heavy Higgs signal with jet-jet profile cuts
The jet-jet profile, or detailed manner, in which transverse energy and mass
are distributed around the jet-jet system resulting from the hadronic decay of
a boson in the process Higgs at a proton-proton collider energy of
40\tev is carefully examined. Two observables are defined that can be used to
help distinguish the -jet-jet signal from Higgs decay from the
``ordinary'' QCD background arising from the large transverse momentum
production of single bosons plus the associated jets. By making cuts on
these observables, signal to background enhancement factors greater than
can be obtained.Comment: 16 pages, Univ. Florida IFT-93-
Using the hadronic multiplicity to distinguish real W’s from QCD jet backgrounds
In order to study WW scattering or the decay of a heavy standard-model Higgs boson in the TeV region, it is necessary to use the channel W(→lν)+W(→jets). However, techniques are required for suppressing the severe background from mixed electroweak-QCD production of W+jets. We demonstrate that the charged multiplicity of the events can provide an extremely useful tool for distinguishing a jet system originating via real W decay from a jet system produced by the mixed electroweak-QCD processes. Analogous techniques will be useful for any process involving W’s→jets, whenever the W decaying to jets has pt≫mW and the primary background produces jets predominantly in a color-nonsinglet state; however the precise procedure must be optimized separately for each such process
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New drift chamber for the Mark II detector at the SLAC Linear Collider
The design of the new cylindrical drift chamber for the Mark II detector at the SLAC Linear Collider is described. Prototype tests to determine the working parameters of the chamber and to study possible gas mixtures are discussed
A Prototype Front-End Readout Chip for Silicon Microstrip Detectors Using an Advanced SiGe Technology
The upgrade of the ATLAS detector for the high luminosity upgrade of the LHC will require a rebuild of the Inner Detector as well as replacement of the readout electronics of the Liquid Argon Calorimeter and other detector components. We proposed some time ago to study silicon germanium (SiGe) BiCMOS technologies as a possible choice for the required silicon microstrip and calorimeter front-end chips given that they showed promise to provide necessary low noise at low power. Evaluation of the radiation hardness of these technologies has been under study. To validate the expected performance of these technologies, we designed and fabricated an 8-channel front-end readout chip for a silicon microstrip detector using the IBM 8WL technology, a likely choice for the ATLAS upgrade. Preliminary electrical characteristics of this chip will be presented
Radiation Hardness of Thin Low Gain Avalanche Detectors
Low Gain Avalanche Detectors (LGAD) are based on a n++-p+-p-p++ structure
where an appropriate doping of the multiplication layer (p+) leads to high
enough electric fields for impact ionization. Gain factors of few tens in
charge significantly improve the resolution of timing measurements,
particularly for thin detectors, where the timing performance was shown to be
limited by Landau fluctuations. The main obstacle for their operation is the
decrease of gain with irradiation, attributed to effective acceptor removal in
the gain layer. Sets of thin sensors were produced by two different producers
on different substrates, with different gain layer doping profiles and
thicknesses (45, 50 and 80 um). Their performance in terms of gain/collected
charge and leakage current was compared before and after irradiation with
neutrons and pions up to the equivalent fluences of 5e15 cm-2. Transient
Current Technique and charge collection measurements with LHC speed electronics
were employed to characterize the detectors. The thin LGAD sensors were shown
to perform much better than sensors of standard thickness (~300 um) and offer
larger charge collection with respect to detectors without gain layer for
fluences <2e15 cm-2. Larger initial gain prolongs the beneficial performance of
LGADs. Pions were found to be more damaging than neutrons at the same
equivalent fluence, while no significant difference was found between different
producers. At very high fluences and bias voltages the gain appears due to deep
acceptors in the bulk, hence also in thin standard detectors
Results from a Prototype Proton-CT Head Scanner
We are exploring low-dose proton radiography and computed tomography (pCT) as
techniques to improve the accuracy of proton treatment planning and to provide
artifact-free images for verification and adaptive therapy at the time of
treatment. Here we report on comprehensive beam test results with our prototype
pCT head scanner. The detector system and data acquisition attain a sustained
rate of more than a million protons individually measured per second, allowing
a full CT scan to be completed in six minutes or less of beam time. In order to
assess the performance of the scanner for proton radiography as well as
computed tomography, we have performed numerous scans of phantoms at the
Northwestern Medicine Chicago Proton Center including a custom phantom designed
to assess the spatial resolution, a phantom to assess the measurement of
relative stopping power, and a dosimetry phantom. Some images, performance, and
dosimetry results from those phantom scans are presented together with a
description of the instrument, the data acquisition system, and the calibration
methods.Comment: Conference on the Application of Accelerators in Research and
Industry, CAARI 2016, 30 October to 4 November 2016, Ft. Worth, TX, US
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