3,542 research outputs found
Isolating CP-violating \gamma ZZ coupling in e+e- \to \gamma Z with transverse beam polarizations
We revisit the process at the ILC with transverse beam
polarization in the presence of anomalous CP-violating coupling
and coupling . We point out that if
the final-state spins are resolved, then it becomes possible to fingerprint the
anomalous coupling {\rm Re}.90% confidence level limit on {\rm
Re} achievable at ILC with center-of-mass energy of 500 GeV or 800
GeV with realistic initial beam polarization and integrated luminosity is of
the order of few times of when the helicity of is used and
when the helicity of is used. The resulting corrections at
quadratic order to the cross section and its influence on these limits are also
evaluated and are shown to be small. The benefits of such polarization
programmes at the ILC are compared and contrasted for the process at hand. We
also discuss possible methods by which one can isolate events with a definite
helicity for one of the final-state particles.Comment: 13 pages, 9 figures, using RevTex; v2 is a significantly revised
version of v1, and corresponds to the version that has been published in
Physical Review
Radiative processes in external gravitational fields
Kinematically forbidden processes may be allowed in the presence of external
gravitational fields. These ca be taken into account by introducing generalized
particle momenta. The corresponding transition probabilities can then be
calculated to all orders in the metric deviation from the field-free
expressions by simply replacing the particle momenta with their generalized
counterparts. The procedure applies to particles of any spin and to any
gravitational fields. transition probabilities, emission power, and spectra
are, to leading order, linear in the metric deviation. It is also shown how a
small dissipation term in the particle wave equations can trigger a strong
backreaction that introduces resonances in the radiative process and deeply
affects the resulting gravitational background.Comment: 5 pages, 1 figur
Needle stick injuries among dental students: risk factors and recommendations for prevention
Aim: To evaluate the risk factors of needle stick injuries (NSIs) sustained by undergraduate dental students and nurse students at the King’s College London (KCL) Dental Institute.Materials and methods: A retrospective study evaluated the incident reports relating to NSIs reported over a period of 2 years. Factors including the dental department, study year, and when the injury took place during administration of local anaesthesia (LA) and recapping conventional syringe or clearing work surface or during disposal.Results: This report showed that students are at the highest risk of NSIs at the fourth year of their 5-year BDS course. About one-third of injuries were reported among this group of students followed by year 5 students (25%). Oral surgery clinics were the major source of incident reporting when compared with other specialised dental clinics within the institute. The left hands of the students were the most frequently affected by such injuries and then the right hands of student dental nurses. The attempt of needle recapping of conventional syringes was the least reported mechanism of injuries and constituted only 15% of the total injuries and mainly occurred in third year students. The most frequent injuries among student nurses were during disposal of the needle.Conclusion: Less NSIs occur when using safety syringes. A non-recapping policy with immediate disposal of either the conventional or safety syringe systems after injection would prevent all clearance-related NSIs sustained by nurses. To avoid NSIs, education plays a vital role particularly with effective implementation of the change to safety syringes with appropriate training.Keywords: needle stick injuries; local anaesthetic syringes; safety syringes; dental students; occupational hazards; dental anaesthetic syringe
Fitting Precision Electroweak Data with Exotic Heavy Quarks
The 1999 precision electroweak data from LEP and SLC persist in showing some
slight discrepancies from the assumed standard model, mostly regarding and
quarks. We show how their mixing with exotic heavy quarks could result in a
more consistent fit of all the data, including two unconventional
interpretations of the top quark.Comment: 7 pages, no figure, 2 typos corrected, 1 reference update
Solutions to the R_b, R_c and alpha_s puzzles by Vector Fermions
We propose two minimal extensions of Standard Model, both of which can easily
accommodate the recent puzzling observations about the excess in , the
deficit in and the discrepancy in the low energy and high energy
determinations of . Each model requires three additional heavy
vectorial fermions in order to resolve the puzzles. The current
phenomenological constraints and the new potential phenomena are also
discussed.Comment: 12 pages, in LaTeX, postscript file also appear
http://www.uic.edu/~keung/pub/rbrc.p
Neutrino Masses and Leptogenesis with Heavy Higgs Triplets
A simple and economical extension of the minimal standard electroweak gauge
model (without right-handed neutrinos) by the addition of two heavy Higgs
scalar triplets would have two significant advantages. \underline {Naturally}
small Majorana neutrino masses would become possible, as well as leptogenesis
in the early universe which gets converted at the electroweak phase transition
into the present observed baryon asymmetry.Comment: 12 pages including one figur
Calibration of centre-of-mass energies at LEP 2 for a precise measurement of the W boson mass
The determination of the centre-of-mass energies for all LEP 2 running is
presented. Accurate knowledge of these energies is of primary importance to set
the absolute energy scale for the measurement of the W boson mass. The beam
energy between 80 and 104 GeV is derived from continuous measurements of the
magnetic bending field by 16 NMR probes situated in a number of the LEP
dipoles. The relationship between the fields measured by the probes and the
beam energy is defined in the NMR model, which is calibrated against precise
measurements of the average beam energy between 41 and 61 GeV made using the
resonant depolarisation technique. The validity of the NMR model is verified by
three independent methods: the flux-loop, which is sensitive to the bending
field of all the dipoles of LEP; the spectrometer, which determines the energy
through measurements of the deflection of the beam in a magnet of known
integrated field; and an analysis of the variation of the synchrotron tune with
the total RF voltage. To obtain the centre-of-mass energies, corrections are
then applied to account for sources of bending field external to the dipoles,
and variations in the local beam energy at each interaction point. The relative
error on the centre-of-mass energy determination for the majority of LEP 2
running is 1.2 x 10^{-4}, which is sufficiently precise so as not to introduce
a dominant uncertainty on the W mass measurement.Comment: 79 pages, 45 figures, submitted to EPJ
Shine 2014 Final Report: Social Prescribing: integrating GP and Community Assets for Health
Commissioned by City and Hackney Clinical Commissioning Group, in partnership with the University of East London and Queen Mary University of London
Precision Electroweak Tests of the Standard Model
The present status of precision electroweak data is reviewed. These data
include measurements of e+e- -> f+fbar, taken at the Z resonance at LEP, which
are used to determine the mass and width of the Z boson. In addition,
measurements have also been made of the forward-backward asymmetries for
leptons and heavy quarks, and also the final state polarisation of the
tau-lepton. At SLAC, where the electron beam was polarised, measurements were
made of the left-right polarised asymmetry, A_LR, and the left-right
forward-backward asymmetries for b and c quarks.
The mass, MW, and width, GW, of the W boson have been measured at the
Tevatron and at LEP, and the mass of the top quark, Mt, has been measured at
the Tevatron. These data, plus other electroweak data, are used in global
electroweak fits in which various Standard Model parameters are determined. A
comparison is made between the results of the direct measurements of MW and Mt
with the indirect results coming from electroweak radiative corrections. Using
all precision electroweak data fits are also made to determine limits on the
mass of the Higgs boson. The influence on these limits of specific
measurements, particularly those which are somewhat inconsistent with the
Standard Model, is explored. The data are also analysed in terms of the quasi
model-independent epsilon variables.
Finally, the impact on the electroweak fits of the improvements in the
determination of the W-boson and top-quark masses, expected from the Tevatron
Run 2, is examined.Comment: 80 pages, 36 Figures, Late
Stiffest Elastic Networks
The rigidity of a network of elastic beams crucially depends on the specific
details of its structure. We show both numerically and theoretically that there
is a class of isotropic networks which are stiffer than any other isotropic
network with same density. The elastic moduli of these \textit{stiffest elastic
networks} are explicitly given. They constitute upper-bounds which compete or
improve the well-known Hashin-Shtrikman bounds. We provide a convenient set of
criteria (necessary and sufficient conditions) to identify these networks, and
show that their displacement field under uniform loading conditions is affine
down to the microscopic scale. Finally, examples of such networks with periodic
arrangement are presented, in both two and three dimensions
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