Search results for "Electroweak"
showing 10 items of 744 documents
"Background only fit in all relevant region for Direct Stau" of "Search for direct stau production in events with two hadronic $\tau$-leptons in $\sq…
2020
Observed and expected numbers of events in the control and signal regions where all control and signal region bins are included as constraints in the likelihood. The expected event yields of SM processes are given after the background-only fit. The entries marked as "--" are negligible. The uncertainties correspond to the sum in quadrature of statistical and systematic uncertainties. The correlation of systematic uncertainties among control regions and among background processes is fully taken into account.
Testing for new physics with low-energy anti-neutrino sources: LAMA as a case study
1998
Some electroweak models with extended neutral currents, such as those based on the $E_6$ group, lead to an increase of the $\bar{\nu}-e$ scattering cross section at energies below 100 keV. We propose to search for the heavy Z' boson contribution in an experiment with a high-activity artificial neutrino source and with a large-mass detector. We present the case for the LAMA experiment with a large NaI(Tl) detector located at the Gran Sasso underground laboratory. The neutrino flux is known to within a one percent accuracy, in contrast to the reactor case and one can reach lower neutrino energies. Both features make our proposed experiment more sensitive to extended gauge models, such as the …
Spacetime curvature and Higgs stability after inflation
2015
We investigate the dynamics of the Higgs field at the end of inflation in the minimal scenario consisting of an inflaton field coupled to the Standard Model only through the non-minimal gravitational coupling $\xi$ of the Higgs field. Such a coupling is required by renormalisation of the Standard Model in curved space, and in the current scenario also by vacuum stability during high-scale inflation. We find that for $\xi\gtrsim 1$, rapidly changing spacetime curvature at the end of inflation leads to significant production of Higgs particles, potentially triggering a transition to a negative-energy Planck scale vacuum state and causing an immediate collapse of the Universe.
Gamow-Teller response in the configuration space of a density-functional-theory–rooted no-core configuration-interaction model
2018
Background: The atomic nucleus is a unique laboratory in which to study fundamental aspects of the electroweak interaction. This includes a question concerning in medium renormalization of the axial-vector current, which still lacks satisfactory explanation. Study of spin-isospin or Gamow-Teller (GT) response may provide valuable information on both the quenching of the axial-vector coupling constant as well as on nuclear structure and nuclear astrophysics.Purpose: We have performed a seminal calculation of the GT response by using the no-core configuration-interaction approach rooted in multireference density functional theory (DFT-NCCI). The model treats properly isospin and rotational sy…
REMARKS ON THE HIGGS-PARTICLE PREDICTION IN THE STANDARD MODEL
2003
Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider
2020
Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these longlived particles (LLPs) can decay far from the interaction vertex of the primary proton–proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP…
The 1-loop effective potential for the Standard Model in curved spacetime
2018
The renormalisation group improved Standard Model effective potential in an arbitrary curved spacetime is computed to one loop order in perturbation theory. The loop corrections are computed in the ultraviolet limit, which makes them independent of the choice of the vacuum state and allows the derivation of the complete set of $\beta$-functions. The potential depends on the spacetime curvature through the direct non-minimal Higgs-curvature coupling, curvature contributions to the loop diagrams, and through the curvature dependence of the renormalisation scale. Together, these lead to significant curvature dependence, which needs to be taken into account in cosmological applications, which i…
Quantum transport and the phase space structure of the Wightman functions
2019
We study the phase space structure of exact quantum Wightman functions in spatially homogeneous, temporally varying systems. In addition to the usual mass shells, the Wightman functions display additional coherence shells around zero frequency $k_0=0$, which carry the information of the local quantum coherence of particle-antiparticle pairs. We find also other structures, which encode non-local correlations in time, and discuss their role and decoherence. We give a simple derivation of the cQPA formalism, a set of quantum transport equations, that can be used to study interacting systems including the local quantum coherence. We compute quantum currents created by a temporal change in a par…
Derivation of spontaneously broken gauge symmetry from the consistency of effective field theory II: Scalar field self-interactions and the electroma…
2019
We extend our study of deriving the local gauge invariance with spontaneous symmetry breaking in the context of an effective field theory by considering self-interactions of the scalar field and inclusion of the electromagnetic interaction. By analyzing renormalizability and the scale separation conditions of three-, four- and five-point vertex functions of the scalar field, we fix the two couplings of the scalar field self-interactions of the leading order Lagrangian. Next we add the electromagnetic interaction and derive conditions relating the magnetic moment of the charged vector boson to its charge and the masses of the charged and neutral massive vector bosons to each other and the tw…
The see-saw portal at future Higgs Factories
2020
We consider an extension of the Standard Model with two right-handed singlet fermions with mass at the electroweak scale that induce neutrino masses, plus a generic new physics sector at a higher scale $\Lambda$. We focus on the effective operators of lowest dimension $d=5$, which induce new production and decay modes for the singlet fermions. We assess the sensitivity of future Higgs Factories, such as FCC-ee, CLIC-380, ILC and CEPC, to the coefficients of these operators for various center of mass energies. We show that future lepton colliders can test the cut-off of the theory up to $\Lambda \simeq 500 - 1000\;$TeV, surpassing the reach of future indirect measurements of the Higgs and $Z…