7,312 research outputs found
Physics Opportunities for Vector-Boson Scattering at a Future 100 TeV Hadron Collider
Vector-boson scattering (VBS) processes provide particularly promising means
for probing the mechanism of electroweak symmetry breaking and to search for
new physics in the weak sector. In the environment of a future proton-proton
collider operating at a center-of-mass energy of 100 TeV, unprecedented
opportunities arise for the investigation of this important class of reactions.
We highlight the prominent features of VBS processes in this energy regime and
discuss how the VBS signal can be isolated in the presence of a priori large
QCD backgrounds. We find excellent opportunities for the analysis of VBS
reactions in a kinematic range that is inaccessible to present colliders.Comment: 26 pages, 14 figures; matches version published by Phys. Rev.
Universal Unitarity Triangle and Physics Beyond the Standard Model
We make the simple observation that there exists a universal unitarity
triangle for all models, like the SM, the Two Higgs Doublet Models I and II and
the MSSM with minimal flavour violation, that do not have any new operators
beyond those present in the SM and in which all flavour changing transitions
are governed by the CKM matrix with no new phases beyond the CKM phase. This
universal triangle can be determined in the near future from the ratio (Delta
M)_d/(Delta M)_s and sin(2 beta) measured first through the CP asymmetry in
B_d^0 to psi K_S and later in K to pi nu nubar decays. Also suitable ratios of
the branching ratios for B to X_{d,s} nu nubar and B_{d,s} to mu^+ mu^- and the
angle gamma measured by means of CP asymmetries in B decays can be used for
this determination. Comparison of this universal triangle with the
non-universal triangles extracted in each model using epsilon, (Delta M)_d and
various branching ratios for rare decays will allow to find out in a
transparent manner which of these models, if any, is singled out by experiment.
A virtue of the universal triangle is that it allows to separate the
determination of the CKM parameters from the determination of new parameters
present in the extensions of the SM considered here.Comment: 12 pages, 1 figur
Periodic Modulations in an X-ray Flare from Sagittarius A*
We present the highly significant detection of a quasi-periodic flux
modulation with a period of 22.2 min seen in the X-ray data of the Sgr A* flare
of 2004 August 31. This flaring event, which lasted a total of about three
hours, was detected simultaneously by EPIC on XMM-Newton and the NICMOS
near-infrared camera on the HST. Given the inherent difficulty in, and the lack
of readily available methods for quantifying the probability of a periodic
signal detected over only several cycles in a data set where red noise can be
important, we developed a general method for quantifying the likelihood that
such a modulation is indeed intrinsic to the source and does not arise from
background fluctuations. We here describe this Monte Carlo based method, and
discuss the results obtained by its application to a other XMM-Newton data
sets. Under the simplest hypothesis that we witnessed a transient event that
evolved, peaked and decayed near the marginally stable orbit of the
supermassive black hole, this result implies that for a mass of 3.5 x 10^{6}
Msun, the central object must have an angular momentum corresponding to a spin
parameter of a=0.22.Comment: 4 pages, 6 figures, submitted to ApJ
Do Men and Women Perform Differently on Different Types of Test Questions?
Men, Women, Tests, Questions, Gender, Teaching/Communication/Extension/Profession,
The Inhomogeneous Wind of the LBV Candidate CygOB2-No.12
We present the results of high-resolution spectroscopy of the extremely
luminous star CygOB2-No.12. We identified about 200 spectral features in the
range 4552-7939 AA, including the interstellar NaI, KI lines and numerous very
strong DIBs, along with the HeI, CII, and SiII lines. An MK spectral type we
derived for the object is B4.5Ia+. Our analysis of the radial velocity data
shows the presence of a gradient in the stellar atmosphere, caused by both
atmospheric expansion and matter infall onto the star. The Halpha emission
displays broad Thompson wings, a slightly blue-shifted PCyg type absorption
component and a time-variable core absorption. We conclude that the wind is
variable in time.Comment: 3 pages, 2 figures, IAU Symposium No.272 "Active OB stars: structure,
evolution, mass loss and critical limits", 201
Event Weighted Tests for Detecting Periodicity in Photon Arrival Times
This paper treats the problem of detecting periodicity in a sequence of
photon arrival times, which occurs, for example, in attempting to detect
gamma-ray pulsars. A particular focus is on how auxiliary information,
typically source intensity, background intensity, and incidence angles and
energies associated with each photon arrival should be used to maximize the
detection power. We construct a class of likelihood-based tests, score tests,
which give rise to event weighting in a principled and natural way, and derive
expressions quantifying the power of the tests. These results can be used to
compare the efficacies of different weight functions, including cuts in energy
and incidence angle. The test is targeted toward a template for the periodic
lightcurve, and we quantify how deviation from that template affects the power
of detection
A Satellite Analysis of Twin Tropical Cyclones in the Western Pacific
Satellite cloud photographs are very important for a clearer understanding of meteorological features of almost every scale and their interrelationships. In this paper, satellite derived information, particularly cirrus-level wind estimates made from cloud photographs, are used to recount the story of twin tropical cyclones--ANNIE and GILDA-- which formed about the same time on opposite sides of the equator in the Western Pacific during November 1967. Throughout the life cycle of the twins, it is the change which takes place in the cirrus-level wind field that enables the meteorologist to discern the step by step development of the respective cyclones as well as the interaction between the high-level winds of the two hemispheres and the twins themselves
Does emergency medicine training improve ECG interpretation skills in South Africa?
Includes abstract.Includes bibliographical references (leaves 35-37).The aim of this study is to assess whether ECG interpretation improves with advancing years of Emergency Medicine training in South Africa, and to compare the results with similar international studies. A prospective cross-sectional study of Emergency Medicine registrars and recently qualified emergency physicians was conducted between August 2008 and February 2009 during training sessions at various universities through South Africa. Subjects completed a survey about level of training and experience, previous ECG training and their impression of the current training program and how it could be improved. They were then asked to interpret 10 clinically important ECGs. The trainees in their first and second years of emergency medicine training were compared to their more senior counterparts (third to fifth years)
Radio Monitoring of the January 11, 1997 Gamma-Ray Burst
We report on a comprehensive radio monitoring program of the bright gamma-ray
burster GRB970111. These VLA observations were made at a frequency of 1.4 GHz
and span a range of post-burst timescales between 28 hours and one month.
Despite extensive sampling at sub-milliJansky sensitivities, no radio source
was detected above 0.5 mJy in the current best error box (~14 arcmin^2) for
GRB970111. A highly unusual radio source, VLA J1528.7+1945, was seen to drop in
flux density by a factor of two in our monitoring period but it lies outside
the error box and thus it is unlikely to be related to GRB970111. Cosmological
fireball models of gamma-ray bursts make predictions of late-time emission
occurring at longer wavelengths. The absence of a flaring or fading radio
counterpart to GRB970111 provides strong constraints on these models.Comment: ApJ Let (accepted
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