656 research outputs found
Discovering the composite Higgs through the decay of a heavy fermion
A possible composite nature of the Higgs could be revealed at the early stage
of the LHC, by analyzing the channels where the Higgs is produced from the
decay of a heavy fermion. The Higgs production from a singly-produced heavy
bottom, in particular, proves to be a promising channel. For a value \lambda=3
of the Higgs coupling to a heavy bottom, for example, we find that, considering
a 125 GeV Higgs which decays into a pair of b-quarks, a discovery is possible
at the 8 TeV LHC with 30 fb^{-1} if the heavy bottom is lighter than roughly
530 GeV (while an observation is possible for heavy bottom masses up to 650
GeV). Such a relatively light heavy bottom is realistic in composite Higgs
models of the type considered and, up to now, experimentally allowed. At
\sqrt{s}=14 TeV the LHC sensitivity on the channel increases significantly.
With \lambda=3 a discovery can occur, with 100 fb^{-1}, for heavy bottom masses
up to 1040 GeV. In the case the heavy bottom was as light as 500 GeV, the 14
TeV LHC would be sensitive to the measure of the \lambda\ coupling in basically
the full range \lambda>1 predicted by the theory.Comment: 25 pp. v2: Minor changes. v3: Version accepted for publication in
JHEP. v4: typos fixe
Physical Tuning and Naturalness
We present a radically new proposal for the solution of the
naturalness/hierarchy problem, where the fine-tuning of the Higgs mass finds
its physical explanation and the well-known multiplicative renormalization of
the usual perturbative approach emerges as an IR property of the
non-perturbative running of the mass.Comment: 7 pages, 4 figure
Associated production of a Kaluza-Klein excitation of a gluon with a t t(bar) pair at the LHC
In Randall-Sundrum models, the Kaluza-Klein (KK) excitations of the gluon,
g_{KK} have enhanced couplings to the right-handed quarks. In the absence of a
gg g_{KK} coupling in these models, the single production of a g_{KK} from an
initial gg state is not possible. The search for other production mechanisms at
the LHC, therefore, becomes important. We suggest that the associated
production of a g_{KK} with a t t(bar) pair is such a mechanism. Our study
shows that through this process the LHC can probe KK gluon masses in the range
of 2.8 -- 2.9 TeV.Comment: 11 pages, 3 figure
Technical and health governance aspects of the External Quality Assessment Scheme for the SARS-CoV-2 molecular tests: Institutional experience performed in all clinical laboratories of a Regional Health Service
Objectives: Since December 2019, the worldwide public health has been threatened by a severe acute respiratory syndrome caused by Coronavirus-2. From the beginning, a turning point has been the identification of new cases of infection, in order to minimize the virus spreading among the population. For this reason, it was necessary introducing a panel of tests able to identify positive cases, which became crucial for all countries. Methods: As a Regional Reference Centre, the CRQ Laboratory (Regional Laboratory for the Quality Control) developed and conducted an External Quality Assessment (EQA) panel of assay, so as to evaluate the quality of real-time reverse transcription polymerase chain reaction (PCR), which were used by 62 Sicilian laboratories, previously authorized to issue certificates for the COVID-19 diagnosis, on behalf of the Public Health Service. Results: The qualitative performance test was based on pooled samples with different viral loads of SARS-CoV-2 or human Coronavirus OC43. 75% of the participating laboratories tested all core samples correctly, while the remaining 25% interpreted incorrectly the EQA exercise samples matching negatively the standards required. Conclusions: Subsequent inspection visits confirmed the issue of incorrect positive and negative certifications for COVID-19 by private and public laboratories, despite the possession of the authorization requirements currently provided for by current regulations, with a significant impact on the SSR
EXPERIMENTAL STUDY ON NH3/H2/AIR COMBUSTION IN SPARK-IGNITION ENGINE CONDITIONS
International audienceThe mitigation of climate change implies the increasing use of variable renewable energy sources. Energy storage and transport solutions will contribute to ensure the stability, reliability and flexibility of the energy systems. Ammonia is a well-known chemical of formula NH3 and, amongst other electrofuels, a promising energy carrier and carbon-free combustible fuel. There-fore, it is of significant interest to study ammonia combustion systems. The present investiga-tion focusses on premixed ammonia/hydrogen/air combustion to assess stability ranges, perfor-mance and pollutant emissions by means of a systematic parametric study, in the purpose of optimization in the case of a current spark-ignition engine. Gaseous ammonia blends with a wide range of hydrogen fuel fractions and equivalence ratio were tested at two different loads. Results show a power output and indicated efficiency benefit of low H2 enrichment for slightly rich and slightly lean mixtures, respectively. Hydrogen is therefore mainly an ignition promoter, rather than a global combustion promoter assumedly due to high thermal losses. A small amount of H2, along with supercharged operation greatly improves the performances of the engine and its stability, thus rendering NH3 a very suitable fuel for SI-engines in case of in-situ H2 gener-ation. Hydrogen also mitigates unburned NH3 emissions, yet not sufficiently but those could be combined with the evenly elevated NOx emissions in dedicated selective catalytic reduction systems
On Composite Two Higgs Doublet Models
We investigate composite two Higgs doublet models realized as pseudo
Goldstone modes, generated through the spontaneous breaking of a global
symmetry due to strong dynamic at the TeV scale. A detailed comparative survey
of two possible symmetry breaking patterns, SU(5) -> SU(4) x U(1) and SU(5) x
SU(4), is made. We point out choices for the Standard Model fermion
representations that can alleviate some phenomenological constraints, with
emphasis towards a simultaneous solution of anomalous Zb\bar{b} coupling and
Higgs mediated Flavor Changing Neutral Currents. We also write down the kinetic
lagrangian for several models leading to Two Higgs Doublets and identify the
anomalous contributions to the T parameter. Moreover, we describe a model based
on the breaking in which there is no tree-level breaking of
custodial symmetry, discussing also the possible embeddings for the fermion
fields.Comment: 17 pages. Mistake corrected, added one section on a T- and flavor
safe model based on SO(9)/SO(8). Matches published versio
Multi‐target directed ligands (Mtdls) binding the σ1 receptor as promising therapeutics: State of the art and perspectives
The sigma‐1 (σ1) receptor is a ‘pluripotent chaperone’ protein mainly expressed at the mitochondria–endoplasmic reticulum membrane interfaces where it interacts with several client proteins. This feature renders the σ1 receptor an ideal target for the development of multifunctional ligands, whose benefits are now recognized because several pathologies are multifactorial. Indeed, the current therapeutic regimens are based on the administration of different classes of drugs in order to counteract the diverse unbalanced physiological pathways associated with the pathology. Thus, the multi‐targeted directed ligand (MTDL) approach, with one molecule that exerts polypharmacological actions, may be a winning strategy that overcomes the pharmacokinetic issues linked to the administration of diverse drugs. This review aims to point out the progress in the development of MTDLs directed toward σ1 receptors for the treatment of central nervous system (CNS) and cancer diseases, with a focus on the perspectives that are proper for this strategy. The evidence that some drugs in clinical use unintentionally bind the σ1 protein (as off‐target) provides a proof of concept of the potential of this strategy, and it strongly supports the promise that the σ1 receptor holds as a target to be hit in the context of MTDLs for the therapy of multifactorial pathologies
Heavy-light decay topologies as a new strategy to discover a heavy gluon
We study the collider phenomenology of the lightest Kaluza-Klein excitation
of the gluon, G*, in theories with a warped extra dimension. We do so by means
of a two-site effective lagrangian which includes only the lowest-lying spin-1
and spin-1/2 resonances. We point out the importance of the decays of G* to one
SM plus one heavy fermion, that were overlooked in the previous literature. It
turns out that, when kinematically allowed, such heavy-light decays are
powerful channels for discovering the G*. In particular, we present a
parton-level Montecarlo analysis of the final state Wtb that follows from the
decay of G* to one SM top or bottom quark plus its heavy partner. We find that
at \sqrt{s} = 7 TeV and with 10 fb^{-1} of integrated luminosity, the LHC can
discover a KK gluon with mass in the range M_{G*} = (1.8 - 2.2) TeV if its
coupling to a pair of light quarks is g_{G*qqbar} = (0.2-0.5) g_3. The same
process is also competitive for the discovery of the top and bottom partners as
well. We find, for example, that the LHC at \sqrt{s} = 7 TeV can discover a 1
TeV KK bottom quark with an integrated luminosity of (5.3 - 0.61) fb^{-1} for
g_{G*qqbar} = (0.2-0.5) g_3.Comment: 36 pages, 13 figures. v2: a few typos corrected, comments added,
version published in JHE
Model-Independent Bounds on a Light Higgs
We present up-to-date constraints on a generic Higgs parameter space. An
accurate assessment of these exclusions must take into account statistical, and
potentially signal, fluctuations in the data currently taken at the LHC. For
this, we have constructed a straightforward statistical method for making full
use of the data that is publicly available. We show that, using the expected
and observed exclusions which are quoted for each search channel, we can fully
reconstruct likelihood profiles under very reasonable and simple assumptions.
Even working with this somewhat limited information, we show that our method is
sufficiently accurate to warrant its study and advocate its use over more naive
prescriptions. Using this method, we can begin to narrow in on the remaining
viable parameter space for a Higgs-like scalar state, and to ascertain the
nature of any hints of new physics---Higgs or otherwise---appearing in the
data.Comment: 32 pages, 10 figures; v3: correction made to basis of four-derivative
operators in the effective Lagrangian, references adde
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