36 research outputs found
Violation of lepton flavour universality in composite Higgs models
We investigate whether the deviation from lepton flavour
universality in decays recently observed at the LHCb
experiment can be explained in minimal composite Higgs models. We show that a
visible departure from universality is indeed possible if left-handed muons
have a sizable degree of compositeness. Constraints from -pole observables
are avoided by a custodial protection of the muon coupling. The deficit in the
invisible width at LEP is explained in the same region of parameters.Comment: 5 pages, 2 figures. v4: discussion of invisible Z width adde
Direct and indirect signals of natural composite Higgs models
We present a comprehensive numerical analysis of a four-dimensional model
with the Higgs as a composite pseudo-Nambu-Goldstone boson that features a
calculable Higgs potential and protective custodial and flavour symmetries to
reduce electroweak fine-tuning. We employ a novel numerical technique that
allows us for the first time to study constraints from radiative electroweak
symmetry breaking, Higgs physics, electroweak precision tests, flavour physics,
and direct LHC bounds on fermion and vector boson resonances in a single
framework. We consider four different flavour symmetries in the composite
sector, one of which we show to not be viable anymore in view of strong
precision constraints. In the other cases, all constraints can be passed with a
sub-percent electroweak fine-tuning. The models can explain the excesses
recently observed in , , and resonance searches by
ATLAS and CMS and the anomalies in angular observables and branching ratios of
rare semi-leptonic decays observed by LHCb. Solving the physics
anomalies predicts the presence of a dijet or resonance around 1 TeV
just below the sensitivity of LHC run 1. We discuss the prospects to probe the
models at run 2 of the LHC. As a side product, we identify several gaps in the
searches for vector-like quarks at hadron colliders, that could be closed by
reanalyzing existing LHC data.Comment: 74 pages, 21 figures. v2: references added, discussion in 3.2.6
extende
Electroweak symmetry breaking and collider signatures in the next-to-minimal composite Higgs model
We conduct a detailed numerical analysis of the composite
pseudo-Nambu-Goldstone Higgs model based on the next-to-minimal coset
, featuring an
additional SM singlet scalar in the spectrum, which we allow to mix with the
Higgs boson. We identify regions in parameter space compatible with all current
experimental constraints, including radiative electroweak symmetry breaking,
flavour physics, and direct searches at colliders. We find the additional
scalar, with a mass predicted to be below a TeV, to be virtually unconstrained
by current LHC data, but potentially in reach of run 2 searches. Promising
indirect searches include rare semi-leptonic decays, CP violation in
mixing, and the electric dipole moment of the neutron.Comment: 32 pages + appendices, 9 figures. v2: minor clarifications, matches
the JHEP versio
as current and future probe of new physics
The rare flavour-changing neutral current decay is among
the most important indirect probes of new physics at the LHC, as it is strongly
suppressed in the Standard Model, very sensitive to new physics effects, and
theoretically exceptionally clean. We present a thorough state-of-the-art
analysis of the constraints on new physics from present and future measurements
of this decay, focusing on scalar operators. We show model-independently and in
concrete new physics models, namely the MSSM and two leptoquark scenarios, that
a future precise measurement of the mass-eigenstate rate asymmetry in
would allow to disentangle new physics scenarios that would
be indistinguishable based on measurements of the branching ratio alone. We
also highlight the complementarity between and direct
searches in both model classes. Our numerics is based on the open source code
flavio and is made publicly available.Comment: 25 pages, 8 figures. Plot scripts available at
https://github.com/DavidMStraub/paper-bsmumu-ans. v2: numerics updated using
published LHCb result, references added. Conclusions unchange
Status of the anomaly after Moriond 2017
Motivated by recent results by the ATLAS and CMS collaborations on the
angular distribution of the decay, we perform a
state-of-the-art analysis of rare meson decays based on the transition. Using standard estimates of hadronic uncertainties, we confirm
the presence of a sizable discrepancy between data and SM predictions. We do
not find evidence for a or helicity dependence of the discrepancy. The
data can be consistently described by new physics in the form of a four-fermion
contact interaction .
Assuming that the new physics affects decays with muons but not with electrons,
we make predictions for a variety of theoretically clean observables sensitive
to violation of lepton flavour universality.Comment: 20 pages, 8 figures, 3 tables. v3: numerics updated using v2 of
arXiv:1606.04731. Conclusions unchanged. Matches published version. Example
script available at https://github.com/DavidMStraub/paper-bkstarmumu-ans
In vitro effects of imatinib mesylate on radiosensitivity and chemosensitivity of breast cancer cells
COMP in the Infrapatellar Fat Pad-Results of a Prospective Histological, Immunohistological, and Biochemical Case-Control Study
Knee osteoarthritis (OA) involves several structures and molecules in the joint, which interact in a pathophysiological process. One of these molecules is the cartilage oligomeric matrix protein (COMP). Elevated COMP levels in the synovial fluid as well as in the serum have been described in OA patients. However, this has not been described in the infrapatellar fat pad (IPFP) tissue before. In this prospective trial, we collected 14 IPFPs from patients with high-grade OA (mean age 63.8 +/- 17.6 years) who underwent total knee replacement (OA group) and from 11 healthy patients (mean age 33.7 +/- 14.8 years) who underwent anterior cruciate ligament reconstruction (control group). The presence of macrophages (CD68 and CD206) and proinflammatory cytokines (interleukin 1 beta [IL-1 beta] and IL-6) was analyzed. Histological and immunohistological examinations as well as immunoblotting analysis for COMP, leptin, and matrix-metalloproteinase-3 were performed. The IPFPs of both the OA and control group consisted of adipose tissue and fibrous tissue, and the fibrous tissue showed higher score values than the adipose tissue for COMP staining (intensity as well as stained area) in both groups. Although COMP could be detected in most samples, leptin expression was found only in single specimens. COMP could be detected mostly in the fibrous tissue portion of the IPFP. We speculate that it is involved in a remodeling process taking place in the IPFP during OA. Presence of leptin was irregular in immunohistology, and the control group showed higher scores in case of presence. Interestingly, immunoblotting could detect leptin in all analyzed samples. (c) 2019 The Authors. Journal of Orthopaedic Research (R) published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Societ
Low-Dose High-Resolution Photon-Counting CT of the Lung: Radiation Dose and Image Quality in the Clinical Routine
This study aims to investigate the qualitative and quantitative image quality of low-dose high-resolution (LD-HR) lung CT scans acquired with the first clinical approved photon counting CT (PCCT) scanner. Furthermore, the radiation dose used by the PCCT is compared to a conventional CT scanner with an energy-integrating detector system (EID-CT). Twenty-nine patients who underwent a LD-HR chest CT scan with dual-source PCCT and had previously undergone a LD-HR chest CT with a standard EID-CT scanner were retrospectively included in this study. Images of the whole lung as well as enlarged image sections displaying a specific finding (lesion) were evaluated in terms of overall image quality, image sharpness and image noise by three senior radiologists using a 5-point Likert scale. The PCCT images were reconstructed with and without a quantum iterative reconstruction algorithm (PCCT QIR+/−). Noise and signal-to-noise (SNR) were measured and the effective radiation dose was calculated. Overall, image quality and image sharpness were rated best in PCCT (QIR+) images. A significant difference was seen particularly in image sections of PCCT (QIR+) images compared to EID-CT images (p < 0.005). Image noise of PCCT (QIR+) images was significantly lower compared to EID-CT images in image sections (p = 0.005). In contrast, noise was lowest on EID-CT images (p < 0.001). The PCCT used significantly less radiation dose compared to the EID-CT (p < 0.001). In conclusion, LD-HR PCCT scans of the lung provide better image quality while using significantly less radiation dose compared to EID-CT scans