2,191 research outputs found
New Higgs Production Mechanism in Composite Higgs Models
Composite Higgs models are only now starting to be probed at the Large Hadron
Collider by Higgs searches. We point out that new resonances, abundant in these
models, can mediate new production mechanisms for the composite Higgs. The new
channels involve the exchange of a massive color octet and single production of
new fermion resonances with subsequent decays into the Higgs and a Standard
Model quark. The sizable cross section and very distinctive kinematics allow
for a very clean extraction of the signal over the background with high
statistical significance. Heavy gluon masses up to 2.8 TeV can be probed with
data collected during 2012 and up to 5 TeV after the energy upgrade to
TeV.Comment: 27 pages, 22 figures. V2: typos corrected, matches published versio
Bounds and Decays of New Heavy Vector-like Top Partners
We study the phenomenology of new heavy vector-like fermions that couple to
the third generation quarks via Yukawa interactions, covering all the allowed
representations under the standard model gauge groups. We first review tree and
loop level bounds on these states. We then discuss tree level decays and
loop-induced decays to photon or gluon plus top. The main decays at tree level
are to W b and/or Z and Higgs plus top via the new Yukawa couplings. The
radiative loop decays turn out to be quite close to the naive estimate: in all
cases, in the allowed perturbative parameter space, the branching ratios are
mildly sensitive on the new Yukawa couplings and small. We therefore conclude
that the new states can be observed at the LHC and that the tree level decays
can allow to distinguish the different representations. Moreover, the
observation of the radiative decays at the LHC would suggest a large Yukawa
coupling in the non-perturbative regime.Comment: 32 pages, 2 tables, 10 figure
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
Low-scale warped extra dimension and its predilection for multiple top quarks
Within warped extra dimension models that explain flavor through geometry,
flavor changing neutral current constraints generally force the Kaluza-Klein
scale to be above many TeV. This creates tension with a natural electroweak
scale. On the other hand, a much lower scale compatible with precision
electroweak and flavor changing neutral current constraints is allowed if we
decouple the Kaluza-Klein states of Standard Model gauge bosons from light
fermions bulk mass parameters). The main
signature for this approach is four top quark production via the Kaluza-Klein
excitations' strong coupling to top quarks. We study single lepton, like-sign
dilepton, and trilepton observables of four-top events at the Large Hadron
Collider. The like-sign dilepton signature typically has the largest discovery
potential for a strongly coupled right-handed top case (M_{KK} \sim 2-2.5
\TeV), while single lepton is the better when the left-handed top couples most
strongly (M_{KK} \sim 2 \TeV). We also describe challenging lepton-jet
collimation issues in the like-sign dilepton and trilepton channels. An
alternative single lepton observable is considered which takes advantage of the
many bottom quarks in the final state. Although searches of other particles may
compete, we find that four top production via Kaluza-Klein gluons is most
promising in a large region of this parameter space.Comment: 35 pages, 8 figures. discussions improved, references adde
Phage therapy efficacy: a review of the last 10 years of preclinical studies
Due to the rise of multidrug-resistant infections in humans, phage therapy is gaining renewed attention in Western medicine. Despite the increasing number of publications focussed on the isolation, characterization and in vitro performance of different phages, there is still a lack of concise pre-clinical information to guide the application of phage therapy in clinical practice. Nevertheless, over the last decade, efforts have been made to conduct more detailed studies of the in vivo efficacy of phages. Here, we review the most relevant in vivo studies performed in the last decade covering phage efficacy in both preclinical and clinical trials. We compare different routes of administration, dosage effect and different animal models of distinct types of infections. Moreover, insights into case studies and results from clinical trials are presented. Challenges and limitations of phage use as evidenced by the current state of research are also discussed in order to improve both the trustworthiness and success of the implementation of phage therapy.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 [POCI-01-0145-FEDER-006684] and Projects PTDC/SAU-PUB/29182/2017 [POCI-01-0145-FEDER-029182] and PTDC/CVTCVT/29628/2017 [POCI-01-0145-FEDER-029628]. This work was also supported by BioTecNorte operation [NORTE-01-
0145-FEDER-000004] funded by the European Regional Development Fund under the scope of Norte2020 -
Programa Operacional Regional do Norte. DPP was supported by a FCT grant [SFRH/BPD/116187/2016]. KD is the recipient of the National Science Centre in Poland grant [UMO-2018/29/B/NZ6/01659]. The funding bodies had no role in study design, data collection and analysis, preparation of the manuscript, or the decision to publish.info:eu-repo/semantics/publishedVersio
Hadronic production of bottom-squark pairs with electroweak contributions
We present the complete computation of the tree-level and the next-to-leading
order electroweak contributions to bottom-squark pair production at the LHC.
The computation is performed within the minimal supersymmetric extension of the
Standard Model. We discuss the numerical impact of these contributions in
several supersymmetric scenarios.Comment: 33 pages, v2: preprint numbers correcte
Warped Radion Dark Matter
Warped scenarios offer an appealing solution to the hierarchy problem. We
consider a non-trivial deformation of the basic Randall-Sundrum framework that
has a KK-parity symmetry. This leads to a stable particle beyond the Standard
Model, that is generically expected to be the first KK-parity odd excitation of
the radion field. We consider the viability of the KK-radion as a DM candidate
in the context of thermal and non-thermal production in the early universe. In
the thermal case, the KK-radion can account for the observed DM density when
the radion decay constant is in the natural multi-TeV range. We also explore
the effects of coannihilations with the first KK excitation of the RH top, as
well as the effects of radion-Higgs mixing, which imply mixing between the
KK-radion and a KK-Higgs (both being KK-parity odd). The non-thermal scenario,
with a high radion decay constant, can also lead to a viable scenario provided
the reheat temperature and the radion decay constant take appropriate values,
although the reheat temperature should not be much higher than the TeV scale.
Direct detection is found to be feasible if the DM has a small (KK-parity odd)
Higgs admixture. Indirect detection via a photon signal from the galactic
center is an interesting possibility, while the positron and neutrino fluxes
from KK-radion annihilations are expected to be rather small. Colliders can
probe characteristic aspects of the DM sector of warped scenarios with
KK-parity, such as the degeneracy between the radion and the KK-radion (DM)
modes.Comment: 43 pages, 16 figures; added reference
The Custodial Randall-Sundrum Model: From Precision Tests to Higgs Physics
We reexamine the Randall-Sundrum (RS) model with enlarged gauge symmetry
SU(2)_L x SU(2)_R x U(1)_X x P_LR in the presence of a brane-localized Higgs
sector. In contrast to the existing literature, we perform the Kaluza-Klein
(KK) decomposition within the mass basis, which avoids the truncation of the KK
towers. Expanding the low-energy spectrum as well as the gauge couplings in
powers of the Higgs vacuum expectation value, we obtain analytic formulas which
allow for a deep understanding of the model-specific protection mechanisms of
the T parameter and the left-handed Z-boson couplings. In particular, in the
latter case we explain which contributions escape protection and identify them
with the irreducible sources of P_LR symmetry breaking. We furthermore show
explicitly that no protection mechanism is present in the charged-current
sector confirming existing model-independent findings. The main focus of the
phenomenological part of our work is a detailed discussion of Higgs-boson
couplings and their impact on physics at the CERN Large Hadron Collider. For
the first time, a complete one-loop calculation of all relevant Higgs-boson
production and decay channels is presented, incorporating the effects stemming
from the extended electroweak gauge-boson and fermion sectors.Comment: 74 pages, 13 figures, 3 tables. v2: Matches version published in JHE
Staphylococcal Panton-Valentine Leukocidin Induces Pro-Inflammatory Cytokine Production and Nuclear Factor-Kappa B Activation in Neutrophils
Panton-Valentine leukocidin (PVL) is a cytotoxin secreted by Staphylococcus aureus and associated with severe necrotizing infections. PVL targets polymorphonuclear leukocytes, especially neutrophils, which are the first line of defense against infections. Although PVL can induce neutrophil death by necrosis or apoptosis, the specific inflammatory responses of neutrophils to this toxin are unclear. In this study, both in vivo and in vitro studies demonstrated that recombinant PVL has an important cytotoxic role in human neutrophils, leading to apoptosis at low concentrations and necrosis at high concentrations. Recombinant PVL also increased the levels of pro-inflammatory cytokine secretion from neutrophils. The up-regulation of pro-inflammatory cytokines was due to nuclear factor-kappa B (NF-κB) activation induced by PVL. Moreover, blocking NF-κB inhibited the production of inflammatory cytokines. To test the role of neutrophil immune responses during the pathogenesis of PVL-induced acute lung injury, we used immunocompetent or neutropenic rabbits to develop a model of necrotizing pneumonia. Immunocompetent rabbits challenged with PVL demonstrated increased inflammation containing neutrophilic infiltrates. In addition, there were elevated levels of inflammatory cytokines (IL-6, IL-8, TNF-α and IL-10) and NF-κB in the lung homogenate. In contrast, the lung tissues from neutropenic rabbits contained mild or moderate inflammation, and the levels of inflammatory cytokines and NF-κB increased only slightly. Data from the current study support growing evidence that neutrophils play an important role in the pathogenesis of PVL-induced tissue injury and inflammation. PVL can stimulate neutrophils to release pro-inflammatory mediators, thereby causing an acute inflammatory response. The ability of PVL to induce inflammatory cytokine release may be associated with the activation of NF-κB or its pore-forming properties
A fourth generation, anomalous like-sign dimuon charge asymmetry and the LHC
A fourth chiral generation, with in the range GeV and a moderate value of the CP-violating phase can explain the
anomalous like-sign dimuon charge asymmetry observed recently by the D0
collaboration. The required parameters are found to be consistent with
constraints from other and decays. The presence of such quarks, apart
from being detectable in the early stages of the LHC, would also have important
consequences in the electroweak symmetry breaking sector.Comment: 18 pages, 9 figures, Figure 1 is modified, more discussions are added
in section 2. new references adde
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