7,166 research outputs found
Precision Measurements of the W-Boson Mass
The Standard Model of electroweak interactions has had great success in
describing the observed data over the last three decades. The precision of
experimental measurements affords tests of the Standard Model at the quantum
loop level beyond leading order. Despite this great success it is important to
continue confronting experimental measurements with the Standard Model
predictions as any deviation would signal new physics. As a fundamental
parameter of the Standard Model, the mass of the W-boson, M_W, is of particular
importance. Aside from being an important test of the SM itself, a precision
measurement of M_W can be used to constrain the mass of the Higgs boson, M_H.
In this article we review the principal experimental techniques for determining
M_W and discuss their combination into a single precision M_W measurement,
which is then used to yield constraints on M_H. We conclude by briefly
discussing future prospects for precision measurements of the W-boson mass.Comment: 37 pages, 13 figures, LaTex, to be published in volume 50 of Annual
Review of Nuclear and Particle Scienc
Higher-order QED corrections to single-W production in electron-positron collisions
Four-fermion processes with a particle lost in the beam pipe are studied at
LEP to perform precision tests of the electroweak theory. Leading higher-order
QED corrections to such processes are analyzed within the framework of the
Structure Functions (SF) approach. The energy scale entering the QED SF is
determined by inspection of the soft and collinear limit of the O(alpha)
radiative corrections to the four-fermion final states, paying particular
attention to the process of single-W production. Numerical predictions are
shown in realistic situations for LEP experiments and compared with existing
results. A Monte Carlo event generator, including exact tree-level matrix
elements, vacuum polarization, higher-order leading QED corrections and
anomalous trilinear gauge couplings, is presented.Comment: LaTeX (using elsart), 21 pages, 8 .ps figure
Light Pair Correction to Bhabha Scattering at Small Angle
This work deals with the computation of electron pair correction to small
angle Bhabha scattering, in order to contribute to the improvement of
luminometry precision at LEP/SLC below 0.1% theoretical accuracy. The exact QED
four-fermion matrix element for , including all
diagrams and mass terms, is computed and different Feynman graph topologies are
studied to quantify the error of approximate calculations present in the
literature. Several numerical results, obtained by a Monte Carlo program with
full matrix element, initial-state radiation via collinear structure functions,
and realistic event selections, are shown and critically compared with the
existing ones. The present calculation, together with recent progress in the
sector of purely photonic corrections, contributes to achieve a
total theoretical error in luminometry at the 0.05% level, close to the current
experimental precision and important in view of the final analysis of the
electroweak precision data.Comment: LaTeX2e, 28 pages, 8 figures include
Light-Pair Corrections to Small-Angle Bhabha Scattering in a Realistic Set-up at LEP
Light-pair corrections to small-angle Bhabha scattering have been computed in
a realistic set-up for luminosity measurements at LEP. The effect of
acollinearity and acoplanarity rejection criteria has been carefully analysed
for typical calorimetric event selections. The magnitude of the correction,
depending on the details of the considered set-up, is comparable with the
present experimental error.Comment: 6 pages, LaTeX (elsart.sty), 4 tables, 1 figur
Higgs decay into four charged leptons in the presence of dimension-six operators
We study the indirect effects of New Physics in the Higgs decay into four
charged leptons, using an Effective Field Theory (EFT) approach to Higgs
interactions. We evaluate the deviations induced by the EFT dimension-six
operators in observables like partial decay width and various kinematic
distributions, including angular observables, and compare them with the
contribution of the full SM electroweak corrections. The calculation is
implemented in an improved version of the event generator Hto4l, which can
provide predictions in terms of different EFT-bases and is available for data
analysis at the LHC. We also perform a phenomenological study in order to
assess the benefits coming from the inclusion of differential information in
the future analyses of very precise data which will be collected during the
high luminosity phase of the LHC.Comment: 31 pages, 8 figures, 1 table. Version to appear on JHEP, expanded
phenomenological section including an analysis for HL-LH
The Raman coupling function in amorphous silica and the nature of the long wavelength excitations in disordered systems
New Raman and incoherent neutron scattering data at various temperatures and
molecular dynamic simulations in amorphous silica, are compared to obtain the
Raman coupling coefficient and, in particular, its low frequency
limit. This study indicates that in the limit
extrapolates to a non vanishing value, giving important indications on the
characteristics of the vibrational modes in disordered materials; in particular
our results indicate that even in the limit of very long wavelength the local
disorder implies non-regular local atomic displacements.Comment: Revtex, 4 ps figure
Knowledge, attitudes, and behavior concerning dental trauma among parents of children attending primary school
BACKGROUND: Traumatic dental injuries occur frequently in children and adolescents. The purpose of the present study is to examine the levels of knowledge and behaviors regarding dental trauma among parents of children attending primary schools in the Apulia region of Italy.
METHODS: The study was carried out using an anonymous questionnaire with closed answers distributed to 2,775 parents who were enrolled based on the entire regional school population. Analyses were conducted using the PROC CORRESP (procedure to perform multiple correspondence analysis) and PROC FASTCLUS (procedure to perform cluster analysis). Statistical significance was set at p-value <0.05.
RESULTS: A total 15.5% of the sample reported that their children had experienced dental trauma. Overall, 53.8% of respondents stated that they knew what to do in cases of dental injury. Regarding the time limit within which it is possible to usefully intervene for dental trauma, 56.8% of respondents indicated "within 30 minutes". Of the total sample, 56.5% knew how to preserve a displaced tooth. A total 62.9% of parents felt it was appropriate for their children to use dental guards during sports activities. The multivariate analysis showed that wrong knowledge are distributed among all kinds of subject. Parents with previous experience of dental trauma referred right behaviours, instead weak knowledge and wrong behaviours are associated with parents that easily worried for dental events.
CONCLUSIONS: This study showed that most parents reported no experience of dental trauma in their children, and half of them did not know what to do in case of traumatic dental injury and they would intervene within 30 minutes, suggesting that dental trauma may trigger panic. However, they did not have the information needed to best assist the affected child. Motivating parents to assume a preventive approach towards dental trauma may produce positive changes that would result an increase of long-term health benefits among both parents and children
Discrimination of SUSY breaking models using single-photon processes at future e+e- linear colliders
We examine the single-photon processes in the frame work of supersymmetric
models at future e+e- linear colliders. According to the recent experimental
achievement, the optimistic polarization degrees for both electron and positron
beams are taken into account to enhance the signal-to-noise ratio revealing the
observable difference between supersymmetry breaking models. The minimal
supergravity model and the minimal SU(5) grand unified model in gaugino
mediation have been examined as examples. We see that after several years of
accummulating data, the difference of the number of single-photon events
between the two models received from the collider would be in excess of three
times the statistical error, providing us the possibility to probe which model
would be realized in nature. The result is well suitable for the future running
of the International Linear Collider.Comment: 14 pages, 4 figures, version to be published in Mod. Phys. Lett.
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