A
bstract
We present a complete basis of dimension-8 operators in the Standard Model Effective Field Theory. Attention is paid to operators that vanish in the absence of flavor structure. The 44,807 ...operators are encoded in 1,031 Lagrangian terms. We also briefly discuss a few aspects of phenomenology involving dimension-8 operators, including light-by-light scattering and electroweak precision data.
A
bstract
We construct a complete basis of dimension-8 operators in the Low-Energy Effective Field Theory below the Electroweak Scale (LEFT). We find there are 35058 dimension-8 operators in the LEFT ...for two generations of up-type quarks and three generations of down-type quarks, charged leptons, and left-handed neutrinos. The existence of this operator basis is a necessary prerequisite for matching to the Standard Model Effective Field Theory at the dimension-8 level.
B-decay anomalies in a composite leptoquark model Barbieri, Riccardo; Murphy, Christopher W.; Senia, Fabrizio
The European physical journal. C, Particles and fields,
12/2016, Volume:
77, Issue:
1
Journal Article
Peer reviewed
Open access
The collection of a few anomalies in semileptonic
B
-decays, especially in
b
→
c
τ
ν
¯
, invites to speculate about the emergence of some striking new phenomena, perhaps interpretable in terms of a ...weakly broken
U
(
2
)
n
flavor symmetry and of leptoquark mediators. Here we aim at a partial UV completion of this interpretation by generalizing the minimal composite Higgs model to include a composite vector leptoquark as well.
A
bstract
The ATLAS and CMS collaborations have recently released significant new data on Higgs and diboson production in LHC Run 2. Measurements of Higgs properties have improved in many channels, ...while kinematic information for
h
→
γγ
and
h
→
ZZ
can now be more accurately incorporated in fits using the STXS method, and
W
+
W
−
diboson production at high
p
T
gives new sensitivity to deviations from the Standard Model. We have performed an updated global fit to precision electroweak data,
W
+
W
−
measurements at LEP, and Higgs and diboson data from Runs 1 and 2 of the LHC in the framework of the Standard Model Effective Field Theory (SMEFT), allowing all coefficients to vary the combined dataset, and present the results in both the Warsaw and SILH operator bases. We exhibit the improvement in the constraints on operator coefficients provided by the LHC Run 2 data, and discuss the correlations between them. We also explore the constraints our fit results impose on several models of physics beyond the Standard Model, including models that contribute to the operator coefficients at the tree level and stops in the MSSM that contribute via loops.
We perform a parameter fit in the standard model effective field theory (SMEFT) with an emphasis on using regularized linear regression to tackle the issue of the large number of parameters in the ...SMEFT. In regularized linear regression, a positive definite function of the parameters of interest is added to the usual cost function. A cross-validation is performed to try to determine the optimal value of the regularization parameter to use, but it selects the standard model (SM) as the best model to explain the measurements. Nevertheless as proof of principle of this technique we apply it to fitting Higgs boson signal strengths in SMEFT, including the latest Run-2 results. Results are presented in terms of the eigensystem of the covariance matrix of the least squares estimators as it has a degree model-independent to it. We find several results in this initial work: the SMEFT predicts the total width of the Higgs boson to be consistent with the SM prediction; the ATLAS and CMS experiments at the LHC are currently sensitive to non-resonant double Higgs boson production. Constraints are derived on the viable parameter space for electroweak baryogenesis in the SMEFT, reinforcing the notion that a first order phase transition requires fairly low-scale beyond the SM physics. Finally, we study which future experimental measurements would give the most improvement on the global constraints on the Higgs sector of the SMEFT.
One of the simplest extensions of the Standard Model is the inclusion of an additional scalar multiplet, and we consider scalars in the SU(2)L singlet, triplet, and quartet representations. We ...examine models with heavy neutral scalars, mH∼1–2 TeV, and the matching of the UV complete theories to the low energy effective field theory. We demonstrate the agreement of the kinematic distributions obtained in the singlet models for the gluon fusion of a Higgs pair with the predictions of the effective field theory. The restrictions on the extended scalar sectors due to unitarity and precision electroweak measurements are summarized and lead to highly restricted regions of viable parameter space for the triplet and quartet models.
The ATLAS and CMS Collaborations recently presented evidence of a resonance decaying to pairs of photons around 750 GeV. In addition, the BaBar, Belle, and LHCb Collaborations have evidence of lepton ...non-universality in the semileptonic decays of B mesons. In this work, we make a first step towards a unified explanation of these anomalies. Specifically, we extend the Standard Model by including vector leptoquarks and a scalar singlet that couples linearly to pairs of the leptoquarks. We find there is parameter space that gives the correct cross section for a putative 750 GeV resonance decaying to photons that is consistent with unitarity, measurements of the properties of the 125 GeV Higgs boson, and direct searches for resonances in other channels. In addition, we also show that constraints can be derived on any Beyond the Standard Model explanation of the 750 GeV resonance where the only new particles are scalars, which are strong enough to rule out certain types of models entirely.
Estimates from claims-based analyses suggest that the incidence of sepsis is increasing and mortality rates from sepsis are decreasing. However, estimates from claims data may lack clinical fidelity ...and can be affected by changing diagnosis and coding practices over time.
To estimate the US national incidence of sepsis and trends using detailed clinical data from the electronic health record (EHR) systems of diverse hospitals.
Retrospective cohort study of adult patients admitted to 409 academic, community, and federal hospitals from 2009-2014.
Sepsis was identified using clinical indicators of presumed infection and concurrent acute organ dysfunction, adapting Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) criteria for objective and consistent EHR-based surveillance.
Sepsis incidence, outcomes, and trends from 2009-2014 were calculated using regression models and compared with claims-based estimates using International Classification of Diseases, Ninth Revision, Clinical Modification codes for severe sepsis or septic shock. Case-finding criteria were validated against Sepsis-3 criteria using medical record reviews.
A total of 173 690 sepsis cases (mean age, 66.5 SD, 15.5 y; 77 660 42.4% women) were identified using clinical criteria among 2 901 019 adults admitted to study hospitals in 2014 (6.0% incidence). Of these, 26 061 (15.0%) died in the hospital and 10 731 (6.2%) were discharged to hospice. From 2009-2014, sepsis incidence using clinical criteria was stable (+0.6% relative change/y 95% CI, -2.3% to 3.5%, P = .67) whereas incidence per claims increased (+10.3%/y 95% CI, 7.2% to 13.3%, P < .001). In-hospital mortality using clinical criteria declined (-3.3%/y 95% CI, -5.6% to -1.0%, P = .004), but there was no significant change in the combined outcome of death or discharge to hospice (-1.3%/y 95% CI, -3.2% to 0.6%, P = .19). In contrast, mortality using claims declined significantly (-7.0%/y 95% CI, -8.8% to -5.2%, P < .001), as did death or discharge to hospice (-4.5%/y 95% CI, -6.1% to -2.8%, P < .001). Clinical criteria were more sensitive in identifying sepsis than claims (69.7% 95% CI, 52.9% to 92.0% vs 32.3% 95% CI, 24.4% to 43.0%, P < .001), with comparable positive predictive value (70.4% 95% CI, 64.0% to 76.8% vs 75.2% 95% CI, 69.8% to 80.6%, P = .23).
In clinical data from 409 hospitals, sepsis was present in 6% of adult hospitalizations, and in contrast to claims-based analyses, neither the incidence of sepsis nor the combined outcome of death or discharge to hospice changed significantly between 2009-2014. The findings also suggest that EHR-based clinical data provide more objective estimates than claims-based data for sepsis surveillance.
A very light boson of mass O(10^{-22}) eV may potentially be a viable dark matter (DM) candidate, which can avoid phenomenological problems associated with cold DM. Such "fuzzy DM (FDM)" may ...naturally be an axion with a decay constant f_{a}∼10^{16}-10^{18} GeV and a mass m_{a}∼μ^{2}/f_{a} with μ∼10^{2} eV. Here, we propose a concrete model, where μ arises as a dynamical scale from infrared confining dynamics, analogous to QCD. Our model is an alternative to the usual approach of generating μ through string theoretic instanton effects. We outline the features of this scenario that result from various cosmological constraints. We find that those constraints are suggestive of a period of mild of inflation, perhaps from a strong first order phase transition, that reheats the standard model (SM) sector only. A typical prediction of our scenario, broadly speaking, is a larger effective number of neutrinos compared to the SM value N_{eff}≈3, as inferred from precision measurements of the cosmic microwave background. Some of the new degrees of freedom may be identified as "sterile neutrinos," which may be required to explain certain neutrino oscillation anomalies. Hence, aspects of our scenario could be testable in terrestrial experiments, which is a novelty of our FDM model.
The apparent breakdown of unitarity in low order perturbation theory is often is used to place bounds on the parameters of a theory. In this work we give an algorithm for approximately computing the ...next-to-leading order (NLO) perturbativity bounds on the quartic couplings of a renormalizable theory whose scalar sector is ϕ4-like. By this we mean theories where either there are no cubic scalar interactions, or the cubic couplings are related to the quartic couplings through spontaneous symmetry breaking. The quantity that tests where perturbation theory breaks down itself can be written as a perturbative series, and having the NLO terms allows one to test how well the series converges. We also present a simple example to illustrate the effect of considering these bounds at different orders in perturbation theory. For example, there is a noticeable difference in the viable parameter when the square of the NLO piece is included versus when it is not.
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