213 research outputs found
Prospects for Heavy Scalar Searches at the LHeC
In this article we study the prospects of the proposed Large Hadron electron
Collider (LHeC) in the search for heavy neutral scalar particles. We consider a
minimal model with one additional complex scalar singlet that interacts with
the Standard Model (SM) via mixing with the Higgs doublet, giving rise to a
SM-like Higgs boson and a heavy scalar particle . Both scalar
particles are produced via vector boson fusion and can be tested via their
decays into pairs of SM particles, analogously to the SM Higgs boson. Using
multivariate techniques we show that the LHeC is sensitive to with masses
between 200 and 800 GeV down to scalar mixing of
Conformal Anomalies and the Gravitational Effective Action: The Correlator for a Dirac Fermion
We compute in linearized gravity all the contributions to the gravitational
effective action due to a virtual Dirac fermion, related to the conformal
anomaly. This requires, in perturbation theory, the identification of the
gauge-gauge-graviton vertex off mass shell, involving the correlator of the
energy-momentum tensor and two vector currents (), which is responsible
for the generation of the gauge contributions to the conformal anomaly in
gravity. We also present the anomalous effective action in the inverse mass of
the fermion as in the Euler-Heisenberg case.Comment: 47 pages, 1 figure. Revised final version, contains 1 additional
section. Accepted for pubblication on Phys. Rev.
The LHC di-photon excess and Gauge Coupling Unification in Extra Heterotic-String Derived Models
The di-photon excess observed at the LHC can be explained as a Standard Model
singlet that is produced and decays by heavy vector-like colour triplets and
electroweak doublets in one-loop diagrams. The characteristics of the required
spectrum are well motivated in heterotic-string constructions that allow for a
light . Anomaly cancellation of the symmetry
requires the existence of the Standard Model singlet and vector-like states in
the vicinity of the breaking scale. In this paper we show
that the agreement with the gauge coupling data at one-loop is identical to the
case of the Minimal Supersymmetric Standard Model, owing to cancellations
between the additional states. We further show that effects arising from heavy
thresholds may push the supersymmetric spectrum beyond the reach of the LHC,
while maintaining the agreement with the gauge coupling data. We show that the
string inspired model can indeed account for the observed signal and discuss
the feasibility of obtaining viable scalar mass spectrum.Comment: 26 pages. 11 figures. Published versio
Sinkhole genesis and evolution in Apulia, and their interrelations with the anthropogenic environment
Sinkhole development occurs in many areas of the world where soluble rocks crop out. Sinkholes are generally the surface expression of the presence of caves and other groundwater flow conduits in carbonate rocks, which are solutionally enlarged secondary permeability features. Their formation may be either natural or caused by man's activities. In both cases, heavy consequences have to be registered on the anthropogenic environment and related infrastructures. Knowledge of the mechanism of formation of this subtle geohazard is therefore necessary to planners and decision makers for performing the most appropriate and suitable programs of land use and development. <P style='line-height: 20px;'> The Apulia region of southern Italy is characterized for most of its extension by carbonate rocks, which makes it one of the most remarkable example of karst in the Mediterranean Basin. Based on analysis of literature and in situ surveys, including caving explorations, we have identified in Apulia three main types of possible mechanisms for sinkhole formation: 1) collapse of a chamber in a natural cave or in man-made cavities; 2) slow and gradual enlargement of doline through dissolution; 3) settlement and internal erosion of filling deposits of pre-existing dolines. Since sinkhole formation very often affects directly the human settlements in Apulia, and have recently produced severe damage, some considerations are eventually presented as regards the interrelationships between sinkholes and the anthropogenic environment
Comments on Anomaly Cancellations by Pole Subtractions and Ghost Instabilities with Gravity
We investigate some aspects of anomaly cancellation realized by the
subtraction of an anomaly pole, stressing on some of its properties in
superspace. In a local formulation these subtractions can be described in terms
of a physical scalar, an axion and related ghosts. They appear to be necessary
for the unitarization of the theory in the ultraviolet, but they may generate
an infrared instability of the corresponding effective action, signalled by
ghost condensation. In particular the subtraction of the superanomaly multiplet
by a pole in superspace is of dubious significance, due to the different nature
of the chiral and conformal anomalies. In turn, this may set more stringent
constraints on the coupling of supersymmetric theories to gravity.Comment: 18 pages. Revised version. To appear in "Classical and Quantum
Gravity
Do radiolucent lines and stress shielding of the humeral shaft really matter in shoulder arthroplasty?
The purpose of this study is to evaluate at a mid-term follow up, the radiological survival of an
uncemented humeral stem in shoulder arthroplasty. One hundred and twenty-six replacements
including hemi (HA), total (TSA) and reverse (RSA) implanted from 1999 to 2008 were reviewed at
a mean follow up of 7.2 years (48-144 months). The same uncemented triconical stem (SMR, Lima
Corporate) was implanted. There were: 23 HSA, 43 TSA, 60 RSA. An independent observer evaluated
all the patients with Constant Score. A radiologic analysis by an expert radiologist and an orthopaedic
surgeon was performed: humeral component-bone interface was divided in seven zones. They judged
a mobilisation if a migration or tilt of the humeral implant or if≥ 2 mm radiolucent line in at least
three zones was present. Chi-squared test, Fisher test and analysis of variance were performed and
a p<0.05 was considered statistically significant. No major radiological signs of loosening and no tilt
or migration of the humeral component were found. Only 23 (18.2%) patients had no RL around the
humeral implant. In the remaining 103 (81.7%) implants: 96 (76.1%) presented RL less than 2 mm,
particularly 75 (59.5%) in less than 3 zones and 21 (16.6%) in more than 3 zones. Of the remaining 7
(5.5%) implants the presence of RL of 2 mm or greater in only one zone was seen. Apart from sepsis
no revision was performed for humeral component loosening. Although a high rate of RL, uncemented
humeral stem has an excellent survivorship at a mid-term follow up. Relationship between presence,
position and depth of RL and internal stress shielding is commonly observed but does not appear t
Dilaton Interactions and the Anomalous Breaking of Scale Invariance of the Standard Model
We discuss the main features of dilaton interactions for fundamental and
effective dilaton fields. In particular, we elaborate on the various ways in
which dilatons can couple to the Standard Model and on the role played by the
conformal anomaly as a way to characterize their interactions. In the case of a
dilaton derived from a metric compactification (graviscalar), we present the
structure of the radiative corrections to its decay into two photons, a photon
and a , two gauge bosons and two gluons, together with their
renormalization properties. We prove that, in the electroweak sector, the
renormalization of the theory is guaranteed only if the Higgs is conformally
coupled. For such a dilaton, its coupling to the trace anomaly is quite
general, and determines, for instance, an enhancement of its decay rates into
two photons and two gluons. We then turn our attention to theories containing a
non-gravitational (effective) dilaton, which, in our perturbative analysis,
manifests as a pseudo-Nambu Goldstone mode of the dilatation current ().
The infrared coupling of such a state to the two-photons and to the two-gluons
sector, and the corresponding anomaly enhancements of its decay rates in these
channels, is critically analyzed.Comment: Revised version, 42 pages, 5 figure
Risk factors for recurrence in patients with Clostridium difficile infection due to 027 and non-027 ribotypes
Objectives: Our objective was to evaluate factors associated with recurrence in patients with 027+ and 027– Clostridium difficile infection (CDI). Methods: Patients with CDI observed between January and December 2014 in six hospitals were consecutively included in the study. The 027 ribotype was deduced by the presence of tcdB, tcdB, cdt genes and the deletion Δ117 in tcdC (Xpert® C. difficile/Epi). Recurrence was defined as a positive laboratory test result for C. difficile more than 14 days but within 8 weeks after the initial diagnosis date with reappearance of symptoms. To identify factors associated with recurrence in 027+ and 027– CDI, a multivariate analysis was performed in each patient group. Subdistributional hazard ratios (sHRs) and 95% confidence intervals (95%CIs) were calculated. Results: Overall, 238 patients with 027+ CDI and 267 with 027– CDI were analysed. On multivariate analysis metronidazole monotherapy (sHR 2.380, 95%CI 1.549–3.60, p <0.001) and immunosuppressive treatment (sHR 3.116, 95%CI 1.906–5.090, p <0.001) were factors associated with recurrence in patients with 027+ CDI. In this patient group, metronidazole monotherapy was independently associated with recurrence in both mild/moderate (sHR 1.894, 95%CI 1.051–3.410, p 0.033) and severe CDI (sHR 2.476, 95%CI 1.281–4.790, p 0.007). Conversely, non-severe disease (sHR 3.704, 95%CI 1.437–9.524, p 0.007) and absence of chronic renal failure (sHR 16.129, 95%CI 2.155–125.000, p 0.007) were associated with recurrence in 027– CDI. Conclusions: Compared to vancomycin, metronidazole monotherapy appears less effective in curing CDI without relapse in the 027+ patient group, independently of disease severity
The decline of the Nasca culture (Peru) as the result of an increasing environmental stress: overcoming the paradigm formulated at Cahuachi of catastrophic mega-floods due to El Niño-Southern Oscillation
- …