554 research outputs found
What if the Higgs couplings to W and Z bosons are larger than in the Standard Model?
We derive a general sum rule relating the Higgs coupling to W and Z bosons to
the total cross section of longitudinal gauge boson scattering in I=0,1,2
isospin channels. The Higgs coupling larger than in the Standard Model implies
enhancement of the I=2 cross section. Such an enhancement could arise if the
Higgs sector is extended by an isospin-2 scalar multiplet including a doubly
charged, singly charged, and another neutral Higgs.Comment: 11 pages, no figures. v2: comments and references added. v3: early
QCD references adde
The intestinal virome in children with cystic fibrosis differs from healthy controls.
Intestinal bacterial dysbiosis is evident in children with cystic fibrosis (CF) and intestinal viruses may be contributory, given their influence on bacterial species diversity and biochemical cycles. We performed a prospective, case-control study on children with CF and age and gender matched healthy controls (HC), to investigate the composition and function of intestinal viral communities. Stool samples were enriched for viral DNA and RNA by viral extraction, random amplification and purification before sequencing (Illumina MiSeq). Taxonomic assignment of viruses was performed using Vipie. Functional annotation was performed using Virsorter. Inflammation was measured by calprotectin and M2-pyruvate kinase (M2-PK). Eight CF and eight HC subjects were included (50% male, mean age 6.9 ± 3.0 and 6.4 ± 5.3 years, respectively, p = 0.8). All CF subjects were pancreatic insufficient. Regarding the intestinal virome, no difference in Shannon index between CF and HC was identified. Taxonomy-based beta-diversity (presence-absence Bray-Curtis dissimilarity) was significantly different between CF and HC (R2 = 0.12, p = 0.001). Myoviridae, Faecalibacterium phage FP Taranis and unclassified Gokushovirinae were significantly decreased in CF compared with HC (q<0.05). In children with CF (compared to HC), the relative abundance of genes annotated to (i) a peptidoglycan-binding domain of the peptidoglycan hydrolases (COG3409) was significantly increased (q<0.05) and (ii) capsid protein (F protein) (PF02305.16) was significantly decreased (q<0.05). Picornavirales, Picornaviridae, and Enterovirus were found to positively correlate with weight and BMI (r = 0.84, q = 0.01). Single-stranded DNA viruses negatively correlated with M2-PK (r = -0.86, q = 0.048). Children with CF have an altered intestinal virome compared to well-matched HC, with both taxonomic and predicted functional changes. Further exploration of Faecalibacterium phages, Gokushovirinae and phage lysins are warranted. Intestinal viruses and their functions may have important clinical implications for intestinal inflammation and growth in children with CF, potentially providing novel therapeutic targets
Revealing the electroweak properties of a new scalar resonance
One or more new heavy resonances may be discovered in experiments at the CERN
Large Hadron Collider. In order to determine if such a resonance is the
long-awaited Higgs boson, it is essential to pin down its spin, CP, and
electroweak quantum numbers. Here we describe how to determine what role a
newly-discovered neutral CP-even scalar plays in electroweak symmetry breaking,
by measuring its relative decay rates into pairs of electroweak vector bosons:
WW, ZZ, \gamma\gamma, and Z\gamma. With the data-driven assumption that
electroweak symmetry breaking respects a remnant custodial symmetry, we perform
a general analysis with operators up to dimension five. Remarkably, only three
pure cases and one nontrivial mixed case need to be disambiguated, which can
always be done if all four decay modes to electroweak vector bosons can be
observed or constrained. We exhibit interesting special cases of Higgs
look-alikes with nonstandard decay patterns, including a very suppressed
branching to WW or very enhanced branchings to \gamma\gamma and Z\gamma. Even
if two vector boson branching fractions conform to Standard Model expectations
for a Higgs doublet, measurements of the other two decay modes could unmask a
Higgs imposter.Comment: 23 pages, two figures; v2: minor revision and version to appear in
JHE
Higgs friends and counterfeits at hadron colliders
We consider the possibility of "Higgs counterfeits" - scalars that can be
produced with cross sections comparable to the SM Higgs, and which decay with
identical relative observable branching ratios, but which are nonetheless not
responsible for electroweak symmetry breaking. We also consider a related
scenario involving "Higgs friends," fields similarly produced through gg fusion
processes, which would be discovered through diboson channels WW, ZZ, gamma
gamma, or even gamma Z, potentially with larger cross sections times branching
ratios than for the Higgs. The discovery of either a Higgs friend or a Higgs
counterfeit, rather than directly pointing towards the origin of the weak
scale, would indicate the presence of new colored fields necessary for the
sizable production cross section (and possibly new colorless but electroweakly
charged states as well, in the case of the diboson decays of a Higgs friend).
These particles could easily be confused for an ordinary Higgs, perhaps with an
additional generation to explain the different cross section, and we emphasize
the importance of vector boson fusion as a channel to distinguish a Higgs
counterfeit from a true Higgs. Such fields would naturally be expected in
scenarios with "effective Z's," where heavy states charged under the SM produce
effective charges for SM fields under a new gauge force. We discuss the
prospects for discovery of Higgs counterfeits, Higgs friends, and associated
charged fields at the LHC.Comment: 27 pages, 5 figures. References added and typos fixe
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
Goldstones in Diphotons
We study the conditions for a new scalar resonance to be observed first in
diphotons at the LHC Run-2. We focus on scenarios where the scalar arises
either from an internal or spacetime symmetry broken spontaneously, for which
the mass is naturally below the cutoff and the low-energy interactions are
fixed by the couplings to the broken currents, UV anomalies, and selection
rules. We discuss the recent excess in diphoton resonance searches observed by
ATLAS and CMS at 750 GeV, and explore its compatibility with other searches at
Run-1 and its interpretation as Goldstone bosons in supersymmetry and composite
Higgs models. We show that two candidates naturally emerge: a Goldstone boson
from an internal symmetry with electromagnetic anomalies, and the scalar
partner of the Goldstone of supersymmetry breaking: the sgoldstino. The dilaton
from conformal symmetry breaking is instead disfavoured by present data, in its
minimal natural realization.Comment: 18 pages + refs, 2 figures. v2: typos corrected, references added,
discussions extended and three new plots. Conclusion unchanged. v3: published
versio
Higgs After the Discovery: A Status Report
Recently, the ATLAS and CMS collaborations have announced the discovery of a
125 GeV particle, commensurable with the Higgs boson. We analyze the 2011 and
2012 LHC and Tevatron Higgs data in the context of simplified new physics
models, paying close attention to models which can enhance the diphoton rate
and allow for a natural weak-scale theory. Combining the available LHC and
Tevatron data in the ZZ* 4-lepton, WW* 2-lepton, diphoton, and b-bbar channels,
we derive constraints on the effective low-energy theory of the Higgs boson. We
map several simplified scenarios to the effective theory, capturing numerous
new physics models such as supersymmetry, composite Higgs, dilaton. We further
study models with extended Higgs sectors which can naturally enhance the
diphoton rate. We find that the current Higgs data are consistent with the
Standard Model Higgs boson and, consequently, the parameter space in all models
which go beyond the Standard Model is highly constrained.Comment: 37 pages; v2: ATLAS dijet-tag diphoton channel added, dilaton and
doublet-singlet bugs corrected, references added; v3: ATLAS WW channel
included, comments and references adde
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
An A4 flavor model for quarks and leptons in warped geometry
We propose a spontaneous A4 flavor symmetry breaking scheme implemented in a
warped extra dimensional setup to explain the observed pattern of quark and
lepton masses and mixings. The main advantages of this choice are the
explanation of fermion mass hierarchies by wave function overlaps, the
emergence of tribimaximal neutrino mixing and zero quark mixing at the leading
order and the absence of tree-level gauge mediated flavor violations. Quark
mixing is induced by the presence of bulk flavons, which allow for cross-brane
interactions and a cross-talk between the quark and neutrino sectors, realizing
the spontaneous symmetry breaking pattern A4 --> nothing first proposed in
[X.G.\,He, Y.Y.\,Keum, R.R.\,Volkas, JHEP{0604}, 039 (2006)]. We show that the
observed quark mixing pattern can be explained in a rather economical way,
including the CP violating phase, with leading order cross-interactions, while
the observed difference between the smallest CKM entries V_{ub} and V_{td} must
arise from higher order corrections. We briefly discuss bounds on the
Kaluza-Klein scale implied by flavor changing neutral current processes in our
model and show that the residual little CP problem is milder than in flavor
anarchic models.Comment: 34 pages, 2 figures; version published in JHE
Middleborns disadvantaged? testing birth-order effects on fitness in pre-industrial finns
Parental investment is a limited resource for which offspring compete in order to increase their own survival and reproductive success. However, parents might be selected to influence the outcome of sibling competition through differential investment. While evidence for this is widespread in egg-laying species, whether or not this may also be the case in viviparous species is more difficult to determine. We use pre-industrial Finns as our model system and an equal investment model as our null hypothesis, which predicts that (all else being equal) middleborns should be disadvantaged through competition. We found no overall evidence to suggest that middleborns in a family are disadvantaged in terms of their survival, age at first reproduction or lifetime reproductive success. However, when considering birth-order only among same-sexed siblings, first-, middle-and lastborn sons significantly differed in the number of offspring they were able to rear to adulthood, although there was no similar effect among females. Middleborn sons appeared to produce significantly less offspring than first-or lastborn sons, but they did not significantly differ from lastborn sons in the number of offspring reared to adulthood. Our results thus show that taking sex differences into account is important when modelling birth-order effects. We found clear evidence of firstborn sons being advantaged over other sons in the family, and over firstborn daughters. Therefore, our results suggest that parents invest differentially in their offspring in order to both preferentially favour particular offspring or reduce offspring inequalities arising from sibling competition
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