753 research outputs found
Muon energy losses and straggling for high energy muons
The non-Gaussian nature of energy loss straggling is examined. At NAL large muon shields must be designed to reduce flux by about a factor of 1012. Fortunately it is shown here that on the long range end, the straggling falls off much faster than Gaussian and the amount of shielding needed is significantly reduced.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33684/1/0000196.pd
Spin Path Integrals and Generations
The spin of a free electron is stable but its position is not. Recent quantum
information research by G. Svetlichny, J. Tolar, and G. Chadzitaskos have shown
that the Feynman \emph{position} path integral can be mathematically defined as
a product of incompatible states; that is, as a product of mutually unbiased
bases (MUBs). Since the more common use of MUBs is in finite dimensional
Hilbert spaces, this raises the question "what happens when \emph{spin} path
integrals are computed over products of MUBs?" Such an assumption makes spin no
longer stable. We show that the usual spin-1/2 is obtained in the long-time
limit in three orthogonal solutions that we associate with the three elementary
particle generations. We give applications to the masses of the elementary
leptons.Comment: 20 pages, 2 figures, accepted at Foundations of Physic
Applying Rule Ensembles to the Search for Super-Symmetry at the Large Hadron Collider
In this note we give an example application of a recently presented
predictive learning method called Rule Ensembles. The application we present is
the search for super-symmetric particles at the Large Hadron Collider. In
particular, we consider the problem of separating the background coming from
top quark production from the signal of super-symmetric particles. The method
is based on an expansion of base learners, each learner being a rule, i.e. a
combination of cuts in the variable space describing signal and background.
These rules are generated from an ensemble of decision trees. One of the
results of the method is a set of rules (cuts) ordered according to their
importance, which gives useful tools for diagnosis of the model. We also
compare the method to a number of other multivariate methods, in particular
Artificial Neural Networks, the likelihood method and the recently presented
boosted decision tree method. We find better performance of Rule Ensembles in
all cases. For example for a given significance the amount of data needed to
claim SUSY discovery could be reduced by 15 % using Rule Ensembles as compared
to using a likelihood method.Comment: 24 pages, 7 figures, replaced to match version accepted for
publication in JHE
Radiation Testing of Electronics for the CMS Endcap Muon System
The electronics used in the data readout and triggering system for the
Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC)
particle accelerator at CERN are exposed to high radiation levels. This
radiation can cause permanent damage to the electronic circuitry, as well as
temporary effects such as data corruption induced by Single Event Upsets. Once
the High Luminosity LHC (HL-LHC) accelerator upgrades are completed it will
have five times higher instantaneous luminosity than LHC, allowing for
detection of rare physics processes, new particles and interactions. Tests have
been performed to determine the effects of radiation on the electronic
components to be used for the Endcap Muon electronics project currently being
designed for installation in the CMS experiment in 2013. During these tests the
digital components on the test boards were operating with active data readout
while being irradiated with 55 MeV protons. In reactor tests, components were
exposed to 30 years equivalent levels of neutron radiation expected at the
HL-LHC. The highest total ionizing dose (TID) for the muon system is expected
at the inner-most portion of the CMS detector, with 8900 rad over ten years.
Our results show that Commercial Off-The-Shelf (COTS) components selected for
the new electronics will operate reliably in the CMS radiation environment
Radiation testing of electronics for the CMS endcap muon system
The electronics used in the data readout and triggering system for the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) particle accelerator at CERN are exposed to high radiation levels. This radiation can cause permanent damage to the electronic circuitry, as well as temporary effects such as data corruption induced by Single Event Upsets. Once the High Luminosity LHC (HL-LHC) accelerator upgrades are completed it will have five times higher instantaneous luminosity than LHC, allowing for detection of rare physics processes, new particles and interactions. Tests have been performed to determine the effects of radiation on the electronic components to be used for the Endcap Muon electronics project currently being designed for installation in the CMS experiment in 2013. During these tests the digital components on the test boards were operating with active data readout while being irradiated with 55 MeV protons. In reactor tests, components were exposed to 30 years equivalent levels of neutron radiation expected at the HL-LHC. The highest total ionizing dose (TID) for the muon system is expected at the innermost portion of the CMS detector, with 8900 rad over 10 years. Our results show that Commercial Off-The-Shelf (COTS) components selected for the new electronics will operate reliably in the CMS radiation environment.Physic
Statistical Analysis of Different Muon-antineutrino->Electron-antineutrino Searches
A combined statistical analysis of the experimental results of the LSND and
KARMEN \numubnueb oscillation search is presented. LSND has evidence for
neutrino oscillations that is not confirmed by the KARMEN experiment. This
joint analysis is based on the final likelihood results for both data sets. A
frequentist approach is applied to deduce confidence regions. At a combined
confidence level of 36%, there is no area of oscillation parameters compatible
with both experiments. For the complementary confidence of 1-0.36=64%, there
are two well defined regions of oscillation parameters (sin^2(2th),Dm^2)
compatible with both experiments.Comment: 25 pages, including 10 figures, submitted to Phys. Rev.
Wedgebox analysis of four-lepton events from neutralino pair production at the LHC
`Wedgebox' plots constructed by plotting the di-electron invariant mass
versus the di-muon invariant mass from pp -> e^+e^- mu^+ mu^- + missing energy
signature LHC events. Data sets of such events are obtained across the MSSM
input parameter space in event-generator simulations, including cuts designed
to remove SM backgrounds. Their study reveals several general features:
(1)Regions in the MSSM input parameter space where a sufficient number of
events are expected so as to be able to construct a clear wedgebox plot are
delineated. (2)The presence of box shapes on a wedgebox plot either indicates
the presence of heavy Higgs bosons decays or restricts the location to a quite
small region of low \mu and M_2 values \lsim 200 GeV, a region denoted as the
`lower island'. In this region, wedgebox plots can be quite complicated and
change in pattern rather quickly as one moves around in the (\mu, M_2) plane.
(3)Direct neutralino pair production from an intermediate Z^{0*} may only
produce a wedge-shape since only \widetilde{\chi}_2^0\widetilde{\chi}_3^0
decays can contribute significantly. (4)A double-wedge or
wedge-protruding-from-a-box pattern on a wedgebox plot, which results from
combining a variety of MSSM production processes, yields three distinct
observed endpoints, almost always attributable to \widetilde{\chi}_{2,3,4}^0
\to \widetilde{\chi}_1^0 \ell^+\ell^- decays, which can be utilized to
determine a great deal of information about the neutralino and slepton mass
spectra and related MSSM input parameters. Wedge and double-wedge patterns are
seen in wedgebox plots in another region of higher \mu and M_2 values, denoted
as the`upper island.' Here the pattern is simpler and more stable as one moves
across the (\mu, M_2) input parameter space.Comment: 28 pages (LaTeX), 8 figures (encapsulated postscript
Statistical Pattern Recognition: Application to Oscillation Searches Based on Kinematic Criteria
Classic statistical techniques (like the multi-dimensional likelihood and the
Fisher discriminant method) together with Multi-layer Perceptron and Learning
Vector Quantization Neural Networks have been systematically used in order to
find the best sensitivity when searching for
oscillations. We discovered that for a general direct appearance
search based on kinematic criteria: a) An optimal discrimination power is
obtained using only three variables (, and
) and their correlations. Increasing the number of variables (or
combinations of variables) only increases the complexity of the problem, but
does not result in a sensible change of the expected sensitivity. b) The
multi-layer perceptron approach offers the best performance. As an example to
assert numerically those points, we have considered the problem of
appearance at the CNGS beam using a Liquid Argon TPC detector.Comment: 24 pages, 15 figure
First Observation of Coherent Production in Neutrino Nucleus Interactions with 2 GeV
The MiniBooNE experiment at Fermilab has amassed the largest sample to date
of s produced in neutral current (NC) neutrino-nucleus interactions at
low energy. This paper reports a measurement of the momentum distribution of
s produced in mineral oil (CH) and the first observation of coherent
production below 2 GeV. In the forward direction, the yield of events
observed above the expectation for resonant production is attributed primarily
to coherent production off carbon, but may also include a small contribution
from diffractive production on hydrogen. Integrated over the MiniBooNE neutrino
flux, the sum of the NC coherent and diffractive modes is found to be (19.5
1.1 (stat) 2.5 (sys))% of all exclusive NC production at
MiniBooNE. These measurements are of immediate utility because they quantify an
important background to MiniBooNE's search for
oscillations.Comment: Submitted to Phys. Lett.
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
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