423 research outputs found
Flavor Physics in SO(10) GUTs with Suppressed Proton decay Due to Gauged Discrete Symmetry
Generic SO(10) GUT models suffer from the problem that Planck scale induced
non-renormalizable proton decay operators require extreme suppression of their
couplings to be compatible with present experimental upper limits. One way to
resolve this problem is to supplement SO(10) by simple gauged discrete
symmetries which can also simultaneously suppress the renormalizable R-parity
violating ones when they occur and make the theory "more natural". Here we
discuss the phenomenological viability of such models. We first show that for
both classes of models, e.g the ones that use or to
break B-L symmetry, the minimal Higgs content which is sufficient for proton
decay suppression is inadequate for explaining fermion masses despite the
presence of all apparently needed couplings. We then present an extended model, with three {\bf 10} and three {\bf 45}-Higgs, where is free of
this problem. We propose this as a realistic and "natural" model for fermion
unification and discuss the phenomenology of this model e.g. its predictions
for neutrino mixings and lepton flavor violation.Comment: 21 pages, 2 figure
Superconformal Technicolor
In supersymmetric theories with a strong conformal sector, soft supersymmetry
breaking at the TeV scale naturally gives rise to confinement and chiral
symmetry breaking at the same scale. We investigate models where such a sector
dynamically breaks electroweak symmetry. We consider two scenarios, one where
the strong dynamics induces vacuum expectation values for elementary Higgs
fields, and another where the strong dynamics is solely responsible for
electroweak symmetry breaking. In both cases there is no fine tuning required
to explain the absence of a Higgs boson below the LEP bound, solving the
supersymmetry naturalness problem. A good precision electroweak fit can be
obtained, and quark and lepton masses are generated without flavor-changing
neutral currents. Electroweak symmetry breaking may be dominated either by the
elementary Higgs bosons or by the strong dynamics. In addition to standard
superymmetry collider signals, these models predict production of multiple
heavy standard model particles (t, W, Z, and b) from decays of resonances in
the strong sector.Comment: 4 pages; v2: minor changes, references adde
Flavor Violation Tests of Warped/Composite SM in the Two-Site Approach
We study flavor violation in the quark sector in a purely 4D, two-site
effective field theory description of the Standard Model and just their first
Kaluza-Klein excitations from a warped extra dimension. The warped 5D framework
can provide solutions to both the Planck-weak and flavor hierarchies of the SM.
It is also related (via the AdS/CFT correspondence) to partial compositeness of
the SM. We focus on the dominant contributions in the two-site model to two
observables which we argue provide the strongest flavor constraints, namely,
epsilon_K and BR(b -> s gamma), where contributions in the two-site model occur
at tree and loop-level, respectively. In particular, we demonstrate that a
"tension" exists between these two observables in the sense that they have
opposite dependence on composite site Yukawa couplings, making it difficult to
decouple flavor-violating effects using this parameter. We choose the size of
the composite site QCD coupling based on the relation of the two-site model to
the 5D model (addressing the Planck-weak hierarchy), where we match the 5D QCD
coupling to the 4D coupling at the loop-level and assuming negligible
tree-level brane-localized kinetic terms. We estimate that a larger size of the
5D gauge coupling is constrained by the requirement of 5D perturbativity. We
find that \sim O(5) TeV mass scale for the new particles in the two-site model
can then be consistent with both observables. We also compare our analysis of
epsilon_K in the two-site model to that in 5D models, including both the cases
of a brane-localized and bulk Higgs.Comment: 46 pages with 10 figure
Precision diboson measurements at hadron colliders
We discuss the measurements of the anomalous triple gauge couplings at Large Hadron Collider focusing on the contribution of the O-3W and O-3 (W) over tilde operators. These deviations were known to be particularly hard to measure due to their suppressed interference with the SM amplitudes in the inclusive processes, leading to approximate flat directions in the space of these Wilson coefficients. We present the prospects for the measurements of these interactions at HL-LHC and HE-LHC using exclusive variables sensitive to the interference terms and taking carefully into account effects appearing due to NLO QCD corrections
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
Higgs Production from Gluon Fusion in Warped Extra Dimensions
We present an analysis of the loop-induced couplings of the Higgs boson to
the massless gauge fields (gluons and photons) in the warped extra dimension
models where all Standard Model fields propagate in the bulk. We show that in
such models corrections to the hgg and couplings are
potentially very large. These corrections can lead to generically sizable
deviations in the production and decay rates of the Higgs boson, even when the
new physics states lie beyond the direct reach of the LHC.Comment: 24 pages, 5 figures. Added Appendix C, minor changes in the text,
replaced figures 2-
Resolving gluon fusion loops at current and future hadron colliders
Inclusive Higgs measurements at the LHC have limited resolution on the gluon fusion loops, being unable to distinguish the long-distance contributions mediated by the top quark from possible short-distance new physics effects. Using an Effective Field Theory (EFT) approach we compare several proposed methods to lift this degeneracy, including tt\uaf h and boosted, off-shell and double Higgs production, and perform detailed projections to the High-Luminosity LHC and a future hadron collider. In addition, we revisit off-shell Higgs production. Firstly, we point out its sensitivity to modifications of the top-Z couplings, and by means of a general analysis we show that the reach is comparable to that of tree-level processes such as tt\uaf Z production. Implications for composite Higgs models are also discussed. Secondly, we assess the regime of validity of the EFT, performing an explicit comparison for a simple extension of the Standard Model containing one vector-like quark. \ua9 2016, The Author(s)
Higgs boson production via vector-like top-partner decays: diphoton or multilepton plus multijets channels at the LHC
We first build a minimal model of vector-like quarks where the dominant Higgs
boson production process at LHC -- the gluon fusion -- can be significantly
suppressed, being motivated by the recent stringent constraints from the search
for direct Higgs production over a wide Higgs mass range. Within this model,
compatible with the present experimental constraints on direct Higgs searches,
we demonstrate that the Higgs () production via a heavy vector-like
top-partner () decay, , , allows to
discover a Higgs boson at the LHC and measure its mass, through the decay
channels or . We also comment on the recent hint
in LHC data from a possible GeV Higgs scalar, in the presence of
heavy vector-like top quarks.Comment: 14 pages, 8 figure
The actin crosslinking protein palladin modulates force generation and mechanosensitivity of tumor associated fibroblasts
Cells organize actin filaments into higher-order structures by regulating the composition, distribution and concentration of actin crosslinkers. Palladin is an actin crosslinker found in the lamellar actin network and stress fibers, which are critical for mechanosensing of the environment. Palladin also serves as a molecular scaffold for α-actinin, another key actin crosslinker. By virtue of its close interactions with actomyosin structures in the cell, palladin may play an important role in cell mechanics. However, the role of palladin in cellular force generation and mechanosensing has not been studied. Here, we investigate the role of palladin in regulating the plasticity of the actin cytoskeleton and cellular force generation in response to alterations in substrate stiffness. Traction force microscopy revealed that tumor-associated fibroblasts generate larger forces on substrates of increased stiffness. Contrary to expectations, knocking down palladin increased the forces generated by cells and inhibited their ability to sense substrate stiffness for very stiff gels. This was accompanied by significant differences in actin organization, adhesion dynamics and altered myosin organization in palladin knock-down cells. Our results suggest that actin crosslinkers such as palladin and myosin motors coordinate for optimal cell function and to prevent aberrant behavior as in cancer metastasis
Nonlinear QED and Physical Lorentz Invariance
The spontaneous breakdown of 4-dimensional Lorentz invariance in the
framework of QED with the nonlinear vector potential constraint
A_{\mu}^{2}=M^{2}(where M is a proposed scale of the Lorentz violation) is
shown to manifest itself only as some noncovariant gauge choice in the
otherwise gauge invariant (and Lorentz invariant) electromagnetic theory. All
the contributions to the photon-photon, photon-fermion and fermion-fermion
interactions violating the physical Lorentz invariance happen to be exactly
cancelled with each other in the manner observed by Nambu a long ago for the
simplest tree-order diagrams - the fact which we extend now to the one-loop
approximation and for both the time-like (M^{2}>0) and space-like (M^{2}<0)
Lorentz violation. The way how to reach the physical breaking of the Lorentz
invariance in the pure QED case taken in the flat Minkowskian space-time is
also discussed in some detail.Comment: 16 pages, 2 Postscript figures to be published in Phys. Rev.
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