Search results for "Electroweak interaction"
showing 10 items of 358 documents
Automated NNLL+NLO Resummation for Jet-Veto Cross Sections
2014
In electroweak-boson production processes with a jet veto, higher-order corrections are enhanced by logarithms of the veto scale over the invariant mass of the boson system. In this paper, we resum these Sudakov logarithms at next-to-next-to-leading logarithmic (NNLL) accuracy and match our predictions to next-to-leading order (NLO) fixed-order results. We perform the calculation in an automated way, for arbitrary electroweak final states and in the presence of kinematic cuts on the leptons produced in the decays of the electroweak bosons. The resummation is based on a factorization theorem for the cross sections into hard functions, which encode the virtual corrections to the boson product…
Electroweak interaction in muonic atoms
1992
The parity non-conserving effective neutral current interaction between charged leptons and nucleons is studied in its implications for atomic physics. Present results on heavy electronic atoms are discussed within the standard electroweak theory and beyond. The new features provided by muonic atoms open the way to the nuclear-spin-dependent parity non-conserving effects. Different observables proposed to study these effects in muonic atoms are reviewed.
New Electroweak Formulation Fundamentally Accounting for the Effect Known as “Maximal Parity-Violation”
2006
The electroweak scheme is wholly recast, in the framework of a relativistic quantum field formalism being a covariant fermion–antifermion extension of the usual one for massive spin- $$\frac{1}{2}$$ point fermions. The new formalism is able to reread the “maximal P-violation” effect in a way restoring P and C symmetries themselves: it provides a natural “chiral field” approach, which gives evidence of the existence of a pseudoscalar (extra) charge variety anticommuting with the scalar (ordinary) one and just underlying the “maximally P-violating” phenomenology. Its zero-mass limit leads to a strict “chiral” particle theory, which remodels any massless spin- $$\frac{1}{2}$$ fermion and corre…
Strongly Coupled Models with a Higgs-like Boson
2013
Considering the one-loop calculation of the oblique S and T parameters, we have presented a study of the viability of strongly-coupled scenarios of electroweak symmetry breaking with a light Higgs-like boson. The calculation has been done by using an effective Lagrangian, being short-distance constraints and dispersive relations the main ingredients of the estimation. Contrary to a widely spread believe, we have demonstrated that strongly coupled electroweak models with massive resonances are not in conflict with experimental constraints on these parameters and the recently observed Higgs-like resonance. So there is room for these models, but they are stringently constrained. The vector and…
R-Parity Breaking in Minimal Supergravity
1999
We consider the Minimal Supergravity Model with universality of scalar and gaugino masses plus an extra bilinear term in the superpotential which breaks R-Parity and lepton number. We explicitly check the consistency of this model with the radiative breaking of the electroweak symmetry. A neutrino mass is radiatively induced, and large Higgs-Lepton mixings are compatible with its experimental bound. We also study briefly the lightest Higgs mass. This one-parameter extension of SUGRA-MSSM is the simplest way of introducing R-parity violation.
Perturbative Unitarity Constraints on Charged/Colored Portals
2015
Dark matter that was once in thermal equilibrium with the Standard Model is generally prohibited from obtaining all of its mass from the electroweak or QCD phase transitions. This implies a new scale of physics and mediator particles needed to facilitate dark matter annihilations. In this work, we consider scenarios where thermal dark matter annihilates via scalar mediators that are colored and/or electrically charged. We show how partial wave unitarity places upper bounds on the masses and couplings on both the dark matter and mediators. To do this, we employ effective field theories with dark matter as well as three flavors of sleptons or squarks with minimum flavor violation. For Dirac (…
Falsifying High-Scale Leptogenesis at the LHC
2013
Measuring a non-zero value for the cross section of any lepton number violating (LNV) process would put a strong lower limit on the washout factor for the effective lepton number density in the early universe at times close to the electroweak phase transition and thus would lead to important constraints on any high-scale model for the generation of the observed baryon asymmetry based on LNV. In particular, for leptogenesis models with masses of the right-handed neutrinos heavier than the mass scale observed at the LHC, the implied large washout factors would lead to a violation of the out-of-equilibrium condition and exponentially suppress the net lepton number produced in such leptogenesis…
Supersymmetric electroweak baryogenesis
1999
We calculate the baryon asymmetry generated at the electroweak phase transition in the minimal supersymmetric standard model, using a new method to compute the CP-violating asymmetry in the Higgsino flux reflected into the unbroken phase. The method is based on a Higgs insertion expansion. We find that the CP asymmetry at leading order is proportional to the change in $\tan \beta$ in the bubble wall, which is at most of order $10^{-2}$, while at next-to-leading order this suppression factor disappears. This result may enhance the final baryon asymmetry generated during the electroweak phase transition for small $\Delta \beta (< 10^{-3}$).
Lepton asymmetries and primordial hypermagnetic helicity evolution
2012
The hypermagnetic helicity density at the electroweak phase transition (EWPT) exceeds many orders of magnitude the galactic magnetic helicity density. Together with previous magnetic helicity evolution calculations after the EWPT and hypermagnetic helicity conversion to the magnetic one at the EWPT, the present calculation completes the description of the evolution of this important topological feature of cosmological magnetic fields. It suggests that if the magnetic field seeding the galactic dynamo has a primordial origin, it should be substantially helical. This should be taken into account in scenarios of galactic magnetic field evolution with a cosmological seed.
Electroweak baryogenesis at high bubble wall velocities
2020
It is widely believed that electroweak baryogenesis should be suppressed in strong phase transitions with fast-moving bubble walls, but this effect has never been quantitatively studied. We rederive fluid equations describing transport of particle asymmetries near the bubble wall without making the small-wall-velocity approximation. We show that the suppression of the baryon asymmetry is a smooth function of the wall speed and that there is no special behavior when crossing the sound speed barrier. Electroweak baryogenesis can thus be efficient also with strong detonations, generically associated with models with observably large gravitational waves. We also make a systematic and critical c…