120 research outputs found
LHC Predictions from a Tevatron Anomaly in the Top Quark Forward-Backward Asymmetry
We examine the implications of the recent CDF measurement of the top-quark
forward-backward asymmetry, focusing on a scenario with a new color octet
vector boson at 1-3 TeV. We study several models, as well as a general
effective field theory, and determine the parameter space which provides the
best simultaneous fit to the CDF asymmetry, the Tevatron top pair production
cross section, and the exclusion regions from LHC dijet resonance and contact
interaction searches. Flavor constraints on these models are more subtle and
less severe than the literature indicates. We find a large region of allowed
parameter space at high axigluon mass and a smaller region at low mass; we
match the latter to an SU(3)xSU(3)/SU(3) coset model with a heavy vector-like
fermion. Our scenario produces discoverable effects at the LHC with only 1-2
inverse femtobarns of luminosity at 7-8 TeV. Lastly, we point out that a
Tevatron measurement of the b-quark forward-backward asymmetry would be very
helpful in characterizing the physics underlying the top-quark asymmetry.Comment: 35 pages, 10 figures, 4 table
Color & Weak triplet scalars, the dimuon asymmetry in decay, the top forward-backward asymmetry, and the CDF dijet excess
The new physics required to explain the anomalies recently reported by the D0
and CDF collaborations, namely the top forward-backward asymmetry (FBA), the
like-sign dimuon charge asymmetry in semileptonic b decay, and the CDF dijet
excess, has to feature an amount of flavor symmetry in order to satisfy the
severe constrains arising from flavor violation. In this paper we show that,
once baryon number conservation is imposed, color & weak triplet scalars with
hypercharge can feature the required flavor structure as a consequence
of standard model gauge invariance. The color & weak triplet model can
simultaneously explain the top FBA and the dimuon charge asymmetry or the
dimuon charge asymmetry and the CDF dijet excess. However, the CDF dijet excess
appears to be incompatible with the top FBA in the minimal framework. Our model
for the dimuon asymmetry predicts the observed pattern in the
region of parameter space required to explain the top FBA, whereas our model
for the CDF dijet anomaly is characterized by the absence of beyond the SM
b-quark jets in the excess region. Compatibility of the color & weak triplet
with the electroweak constraints is also discussed. We show that a Higgs boson
mass exceeding the LEP bound is typically favored in this scenario, and that
both Higgs production and decay can be significantly altered by the triplet.
The most promising collider signature is found if the splitting among the
components of the triplet is of weak scale magnitude.Comment: references added, published versio
On CP Asymmetries in Two-, Three- and Four-Body D Decays
Indirect and direct CP violations have been established in K_L and B_d
decays. They have been found in two-body decay channels -- with the exception
of K_L to pi^+ pi^- e^+ e^- transitions. Evidence for direct CP asymmetry has
just appeared in LHCb data on A_{CP}(D^0 to K^+ K^-) - A_{CP}(D^0 to pi^+ pi^-)
with 3.5 sigma significance. Manifestations of New Dynamics (ND) can appear in
CP asymmetries just below experimental bounds. We discuss D^{\pm}_{(s)},
D^0/\bar D^0 and D_L/D_S transitions to 2-, 3- and 4-body final states with a
comment on predictions for inclusive vs. exclusive CP asymmetries. In
particular we discuss T asymmetries in D to h_1 h_2 l^+ l^- in analogy with K_L
to pi^+ pi^- e^+ e^- transitions due to interference between M1, internal
bremsstrahlung and possible E1 amplitudes. Such an effect depends on the
strength of CP violation originating from the ND -- as discussed here for
Little Higgs Models with T parity and non-minimal Higgs sectors -- but also in
the interferences between these amplitudes even in the Standard Model (SM).
More general lessons can be learnt for T asymmetries in non-leptonic D decays
like D to h_1h_2 h_3 h_4. Such manifestations of ND can be tested at LHCb and
other Super-Flavour Factories like the projects at KEK near Tokyo and at Tor
Vergata/Frascati near Rome.Comment: 27 pages, 6 figures. Revised with current results from LHCb and HFAG
and further interpretation
Long Lived Fourth Generation and the Higgs
A chiral fourth generation is a simple and well motivated extension of the
standard model, and has important consequences for Higgs phenomenology. Here we
consider a scenario where the fourth generation neutrinos are long lived and
have both a Dirac and Majorana mass term. Such neutrinos can be as light as 40
GeV and can be the dominant decay mode of the Higgs boson for Higgs masses
below the W-boson threshold. We study the effect of the Majorana mass term on
the Higgs branching fractions and reevaluate the Tevatron constraints on the
Higgs mass. We discuss the prospects for the LHC to detect the semi-invisible
Higgs decays into fourth generation neutrino pairs. Under the assumption that
the lightest fourth generation neutrino is stable, it's thermal relic density
can be up to 20% of the observed dark matter density in the universe. This is
in agreement with current constraints on the spin dependent neutrino-neutron
cross section, but can be probed by the next generation of dark matter direct
detection experiments.Comment: v1: 19 pages, 5 figures; v2: References added; v3: version to appear
in JHE
The Status of GMSB After 1/fb at the LHC
We thoroughly investigate the current status of supersymmetry in light of the
latest searches at the LHC, using General Gauge Mediation (GGM) as a
well-motivated signature generator that leads to many different simplified
models. We consider all possible promptly-decaying NLSPs in GGM, and by
carefully reinterpreting the existing LHC searches, we derive limits on both
colored and electroweak SUSY production. Overall, the coverage of GGM parameter
space is quite good, but much discovery potential still remains even at 7 TeV.
We identify several regions of parameter space where the current searches are
the weakest, typically in models with electroweak production, third generation
sfermions or squeezed spectra, and we suggest how ATLAS and CMS might modify
their search strategies given the understanding of GMSB at 1/fb. In particular,
we propose the use of leptonic to suppress backgrounds.
Because we express our results in terms of simplified models, they have broader
applicability beyond the GGM framework, and give a global view of the current
LHC reach. Our results on 3rd generation squark NLSPs in particular can be
viewed as setting direct limits on naturalness.Comment: 44 pages, refs added, typos fixed, improved MC statistics in fig 1
Sinonasal inverted papilloma - malignant transformation and non-sinonasal malignancies
Objectives: To assess malignant transformation rate, non-sinonasal malignancies, and factors contributing to recurrence in patients treated for sinonasal inverted papilloma (SNIP).Study design: Retrospective study.Methods: We retrospectively reviewed medical records of all patients treated for SNIP (n = 296) between the years 1984-2014 at Helsinki University Hospital. Data from the Finnish Cancer Registry confirmed the number of those patients with sinonasal and non-sinonasal malignancies.Results: Only 2 of 296 (0.7%) patients primarily diagnosed with benign SNIP developed sinonasal cancer in a mean follow-up of 5.8 years. The most common non-sinonasal cancer sites were similar to those reported for the whole Finnish population. None of the patients presented with an HPV-associated non-sinonasal malignancy. The recurrence rate among patients who underwent attachment-oriented surgery was significantly lower compared to those operated on with other approaches (40.2% vs. 56.6%, p = 0.006). Dysplasia in SNIP was associated with a higher recurrence rate (p Conclusions: Malignant transformation of SNIP was rare. Patients with SNIP were not prone to HPV-associated non-sinonasal malignancies. Endoscopic resection and attachment-oriented surgery have become predominant approaches in the treatment of SNIP; meanwhile, the total number of SNIP recurrences has decreased.</p
Chiral U(1) flavor models and flavored Higgs doublets: the top FB asymmetry and the Wjj
We present U(1) flavor models for leptophobic Z' with flavor dependent
couplings to the right-handed up-type quarks in the Standard Model, which can
accommodate the recent data on the top forward-backward (FB) asymmetry and the
dijet resonance associated with a W boson reported by CDF Collaboration. Such
flavor-dependent leptophobic charge assignments generally require extra chiral
fermions for anomaly cancellation. Also the chiral nature of U(1)' flavor
symmetry calls for new U(1)'-charged Higgs doublets in order for the SM
fermions to have realistic renormalizable Yukawa couplings. The stringent
constraints from the top FB asymmetry at the Tevatron and the same sign top
pair production at the LHC can be evaded due to contributions of the extra
Higgs doublets. We also show that the extension could realize cold dark matter
candidates.Comment: 40 pages, 10 figures, added 1 figure and extended discussion,
accepted for publication in JHE
Lopsided gauge mediation
It has been recently pointed out that the unavoidable tuning among supersymmetric parameters required to raise the Higgs boson mass beyond its experimental limit opens up new avenues for dealing with the so called mu-B(mu) problem of gauge mediation. In fact, it allows for accommodating, with no further parameter tuning, large values of B(mu) and of the other Higgs-sector soft masses, as predicted in models where both mu and B(mu) are generated at one-loop order. This class of models, called Lopsided Gauge Mediation, offers an interesting alternative to conventional gauge mediation and is characterized by a strikingly different phenomenology, with light higgsinos, very large Higgs pseudoscalar mass, and moderately light sleptons. We discuss general parametric relations involving the fine-tuning of the model and various observables such as the chargino mass and the value of tan beta. We build an explicit model and we study the constraints coming from LEP and Tevatron. We show that in spite of new interactions between the Higgs and the messenger super fields, the theory can remain perturbative up to very large scales, thus retaining gauge coupling unification
Neutrino masses from new generations
We reconsider the possibility that Majorana masses for the three known
neutrinos are generated radiatively by the presence of a fourth generation and
one right-handed neutrino with Yukawa couplings and a Majorana mass term. We
find that the observed light neutrino mass hierarchy is not compatible with low
energy universality bounds in this minimal scenario, but all present data can
be accommodated with five generations and two right-handed neutrinos. Within
this framework, we explore the parameter space regions which are currently
allowed and could lead to observable effects in neutrinoless double beta decay,
conversion in nuclei and experiments. We
also discuss the detection prospects at LHC.Comment: 28 pages, 4 figures. Version to be published. Some typos corrected.
Improved figures 3 and
Effective Dark Matter Model: Relic density, CDMS II, Fermi LAT and LHC
The Cryogenic Dark Matter Search recently announced the observation of two
signal events with a 77% confidence level. Although statistically inconclusive,
it is nevertheless suggestive. In this work we present a model-independent
analysis on the implication of a positive signal in dark matter scattering off
nuclei. Assuming the interaction between (scalar, fermion or vector) dark
matter and the standard model induced by unknown new physics at the scale
, we examine various dimension-6 tree-level induced operators and
constrain them using the current experimental data, e.g. the WMAP data of the
relic abundance, CDMS II direct detection of the spin-independent scattering,
and indirect detection data (Fermi LAT cosmic gamma-ray), etc. Finally, the LHC
reach is also explored
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