4,007 research outputs found
tau Decays to Five Mesons in TAUOLA
The tau-decay library TAUOLA has gained popularity over the last decade.
However, with the continuously increasing precision of the data, some of its
functionality has become insufficient. One of the requirements is the
implementation of decays into five mesons plus a neutrino with a realistic
decay amplitude. This note describes a step into this direction. For the 2pi-
pi+ 2pi0 mode the three decay chains tau- --> a_1- nu --> rho- (--> pi- pi0)
omega (--> pi- pi+ pi0) nu, tau- --> a_1- nu --> a_1- (--> 2pi- pi+) f_0 (-->
2pi0) nu, and tau- --> a_1- nu --> a_1- (--> pi- 2pi0) f_0 (--> pi + pi-) nu
are introduced with simple assumptions about the couplings and propagators of
the various resonances. Similar amplitudes (without the rho omega
contributions) are adopted for the pi- 4pi0 and 3pi- 2pi+ modes.
The five-pion amplitude is thus based on a simple model, which, however, can
be considered as a first realistic example. Phase-space generation includes the
possibility of presampling the omega and a_1 resonances, in one channel only,
however. This is probably sufficient for the time being, both for physics
applications and for tests.
The technical test of the new part of the generator is performed by comparing
Monte Carlo and analytical results. To this end a non-realistic, but easy to
calculate, purely scalar amplitude for the decay into five massless pions was
used.Comment: 10 page
Invariant mass distributions in cascade decays
We derive analytical expressions for the shape of the invariant mass
distributions of massless Standard Model endproducts in cascade decays
involving massive New Physics (NP) particles, D -> Cc -> Bbc -> Aabc, where the
final NP particle A in the cascade is unobserved and where two of the particles
a, b, c may be indistinguishable. Knowledge of these expressions can improve
the determination of NP parameters at the LHC. The shape formulas are
composite, but contain nothing more complicated than logarithms of simple
expressions. We study the effects of cuts, final state radiation and detector
effects on the distributions through Monte Carlo simulations, using a
supersymmetric model as an example. We also consider how one can deal with the
width of NP particles and with combinatorics from the misidentification of
final state particles. The possible mismeasurements of NP masses through `feet'
in the distributions are discussed. Finally, we demonstrate how the effects of
different spin configurations can be included in the distributions.Comment: 39 pages, 14 figures (colour), JHEP clas
A high intensity radiation effects facility
The facility of the Michigan Ion Beam Laboratory at the University of Michigan has been upgraded to conduct high intensity radiation effects studies on materials. This upgrade is necessary to pursue higher radiation damage levels than the studies previously conducted. To achieve this capability a new volume ion source was installed which can produce several times more HâHâ current than the previous duoplasmatron. We will describe the objectives of the research and the facility as well as applications to a variety of radiation damage problems. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87674/2/687_1.pd
Remote Monitoring and Control of Irradiation Experiments
As computer technology plays an increasing important role in particle accelerator facilities, instrumentation systems can be expected to include web connections and other remote capability features. The Michigan Ion Beam Laboratory at the University of Michigan in Ann Arbor has developed remote monitor and control capability by using a combination of commercial software packages and inâhouse software development. Irradiation parameters such as ion current on the samples and apertures, sample temperature read from an optical pyrometer, and chamber pressure can all be accessed and monitored remotely through a web site, as can ion source parameters such as power supply currents and voltages or feed gas pressure. With administrator permission, the control parameters of the ion source or the readouts from the irradiation stage can be modified in real time during an experiment. A description will be given of the various ways in which this type of remote monitoring and control has been accomplished at the Michigan Ion Beam Laboratory. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87309/2/1046_1.pd
Looking for CP violation in B -> tau+tau- decays
In supersymmetry with large tan(beta) the decays B0(B0bar) -> l+l- are
dominated by the scalar and pseudoscalar Higgs penguin diagrams leading to
strong enhancement of leptonic decay rates with potentially large CP
asymmetries in the tau+tau- decay modes measurable in BELLE or BaBar
experiments. The TAUOLA tau-lepton decay library supplemented by its universal
interface can efficiently be used to search for B0(B0bar) -> tau+tau- decays,
and to investigate how the CP asymmetry is reflected in realistic experimental
observables.Comment: LaTeX, 12 pages, 3 figures, Talk given at the International
Conference "Matter to the Deepest'', Ustron, Poland, 8-14 September 200
Surface analysis for students in Nuclear Engineering and Radiological Sciences
Students in Nuclear Engineering and Radiological Sciences at the University of Michigan are required to learn about the various applications of radiation. Because of the broad applicability of accelerators to surface analysis, one of these courses includes a laboratory session on surface analysis techniques such as Rutherford Backscattering Analysis (RBS) and Nuclear Reaction Analysis (NRA). In this laboratory session, the students determine the concentration of nitrogen atoms in various targets using RBS and NRA by way of the 14N(d,α)12C reaction. The laboratory is conducted in a handsâon format in which the students conduct the experiment and take the data. This paper describes the approach to teaching the theory and experimental methods behind the techniques, the conduct of the experiment and the analysis of the data. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87310/2/856_1.pd
Optical properties of Ti and N implanted soda lime glass
Soda lime glass was implanted sequentially with Ti+ and N+ to doses ranging from 2 to 30Ă1016 cmâ2 in order to study the resulting optical properties. Analysis of the implant distributions was made by using Rutherford backscattering and xâray photoelectron spectroscopy and revealed profiles which closely followed each other as designed by the selection of implant energies. Analysis of optical properties showed that the highest dose resulted in an increase in the fraction of infrared reflected by more than a factor of 4 versus 1.7 for the visible regime. The percentage of the total solar radiation rejected exceeded 60% at the highest dose, indicating that the buried layer is highly effective in reducing solar load. © 1995 American Institute of Physics. âPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71178/2/APPLAB-66-2-142-1.pd
Mass Determination in SUSY-like Events with Missing Energy
We describe a kinematic method which is capable of determining the overall
mass scale in SUSY-like events at a hadron collider with two missing (dark
matter) particles. We focus on the kinematic topology in which a pair of
identical particles is produced with each decaying to two leptons and an
invisible particle (schematically, followed by each
decaying via where is invisible). This topology
arises in many SUSY processes such as squark and gluino production and decay,
not to mention t\anti t di-lepton decays. In the example where the final
state leptons are all muons, our errors on the masses of the particles ,
and in the decay chain range from 4 GeV for 2000 events after cuts to 13
GeV for 400 events after cuts. Errors for mass differences are much smaller.
Our ability to determine masses comes from considering all the kinematic
information in the event, including the missing momentum, in conjunction with
the quadratic constraints that arise from the , and mass-shell
conditions. Realistic missing momentum and lepton momenta uncertainties are
included in the analysis.Comment: 41 pages, 14 figures, various clarifications and expanded discussion
included in revised version that conforms to the version to be publishe
Formation of buried TiN in glass by ion implantation to reduce solar load
Ti and N were implanted into soda lime glass to doses up to 4.5Ă1017 cmâ2 to reduce solar load and infrared transmission. Analysis of the Ti+N implant distributions by Rutherford backscattering spectrometry and xâray photoelectron spectroscopy (XPS) revealed profiles which closely followed each other as designed by the selection of implant energies. XPS, xâray diffraction, and selected area electron diffraction in transmission electron microscopy also confirmed the existence of a crystalline B1âtype, cubic TiN layer, 140 nm wide, at doses greater than 9Ă1016 cmâ2. Optical measurements showed that the fraction of infrared radiation reflected was increased by almost a factor of 4 compared to an increase of 1.8 in the visible region. The percentage of the total solar energy rejected reached 80% at the highest dose, indicating that the buried TiN layer is highly effective in reducing solar energy transmission. © 1996 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69679/2/JAPIAU-80-5-2768-1.pd
Cost-benefit analysis for commissioning decisions in GEO600
Gravitational wave interferometers are complex instruments, requiring years
of commissioning to achieve the required sensitivities for the detection of
gravitational waves, of order 10^-21 in dimensionless detector strain, in the
tens of Hz to several kHz frequency band. Investigations carried out by the
GEO600 detector characterisation group have shown that detector
characterisation techniques are useful when planning for commissioning work. At
the time of writing, GEO600 is the only large scale laser interferometer
currently in operation running with a high duty factor, 70%, limited chiefly by
the time spent commissioning the detector. The number of observable
gravitational wave sources scales as the product of the volume of space to
which the detector is sensitive and the observation time, so the goal of
commissioning is to improve the detector sensitivity with the least possible
detector down time. We demonstrate a method for increasing the number of
sources observable by such a detector, by assessing the severity of
non-astrophysical noise contaminations to efficiently guide commissioning. This
method will be particularly useful in the early stages and during the initial
science runs of the aLIGO and adVirgo detectors, as they are brought up to
design performance.Comment: 17 pages, 17 figures, 2 table
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