We study the scalar leptoquark effects on the rare semileptonic decays of Λb baryon, governed by the quark level transition . We estimate the branching ratios, forward–backward asymmetries, lepton polarisation parameters and the lepton flavour non-universality effects in these decay channels. We find significant deviations from the corresponding standard model predictions in some of the observables due to leptoquark effects. We also investigate the lepton flavour violating decays , the branching ratios of which are found to be .

India

Effects of scalar leptoquark on semileptonic Λb decays

An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at Â =Â 13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fbâ1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. Compared with the results of earlier ATLAS searches, the sensitivity is increased for leptoquark masses above 860 GeV, and the observed exclusion limits confirm and extend the published results.

Romania

Portugal

China

Morocco

France

United States

Azerbaijan

Netherlands

United Kingdom

Israel

Sweden

Italy

Poland

Germany

Serbia

Spain

JINR

Russia

Canada

Argentina

CERN

Greece

Denmark

Japan

Brazil

Switzerland

Türkiye

Search for scalar leptoquarks in pp collisions at Â =Â 13 TeV with the ATLAS experiment

A new search signature for excited leptons is explored. Excited muons are sought in the channel , assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb−1 of pp collision data at a centre-of-mass energy of taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass . For between 1.3 and 3.0 TeV, the upper limit on ) is between 0.6 and 1 fb. Limits on are converted to lower bounds on the compositeness scale Λ. In the limiting case , excited muons with a mass below 2.8 TeV are excluded. With the same model assumptions, these limits at larger masses improve upon previous limits from traditional searches based on the gauge-mediated decay .

Taiwan

Slovakia

A search for an excited muon decaying to a muon and two jets in pp collisions at with the ATLAS detector

Assuming the form at fixed Q2 for the behavior of the virtual-photon proton scattering cross section, where l is the coherence length of the photon fluctuations, it is seen that the extrapolated values of for different Q2 cross for fm. It is argued that this behavior is not physical, and that the behavior of the cross sections must change before this coherence length l is reached. This could set the scale for the onset of saturation of the parton densities in the photon, and thereby saturation of parton densities in general.

The evolution of σγP with coherence length

Neutrino mass generation through the Higgs mechanism not only suggests the need to reconsider the physics of electroweak symmetry breaking from a new perspective, but also provides a new theoretically consistent and experimentally viable paradigm. We illustrate this by describing the main features of the electroweak symmetry breaking sector of the simplest type-II seesaw model with spontaneous breaking of lepton number. After reviewing the relevant ‘theoretical’ and astrophysical restrictions on the Higgs sector, we perform an analysis of the sensitivities of Higgs Boson searches at the ongoing ATLAS and CMS experiments at the LHC, including not only the new contributions to the decay channels present in the standard model (SM) but also genuinely non-SM Higgs Boson decays, such as ‘invisible’ Higgs Boson decays to majorons. We find sensitivities that are likely to be reached at the upcoming run of the experiments.

Electroweak breaking and neutrino mass: ‘invisible’ Higgs decays at the LHC (type II seesaw)

The Lefschetz-thimble approach to path integrals is applied to a one-site model of electrons, i.e., the one-site Hubbard model. Since the one-site Hubbard model shows a non-analytic behavior at the zero temperature and its path integral expression has the sign problem, this toy model is a good testing ground for an idea or a technique to attack the sign problem. Semiclassical analysis using complex saddle points unveils the significance of interference among multiple Lefschetz thimbles to reproduce the non-analytic behavior by using the path integral. If the number of Lefschetz thimbles is insufficient, we found not only large discrepancies from the exact result, but also thermodynamic instabilities. Analyzing such singular behaviors semiclassically, we propose a criterion to identify the necessary number of Lefschetz thimbles. We argue that this interference of multiple saddle points is a key issue to understand the sign problem of the finite-density quantum chromodynamics.

Lefschetz-thimble analysis of the sign problem in one-site fermion model

This paper discusses recent results and near-term prospects of the long-baseline neutrino experiments MINOS, MINOS+, T2K and NOvA. The non-zero value of the third neutrino mixing angle θ13 allows experimental analysis in a manner which explicitly exhibits appearance and disappearance dependencies on additional parameters associated with mass-hierarchy, CP violation, and any non-maximal θ23. These current and near-future experiments begin the era of precision accelerator long-baseline measurements and lay the framework within which future experimental results will be interpreted.

Neutrino oscillations with the MINOS, MINOS+, T2K, and NOvA experiments

We study the rare semileptonic decays of B mesons induced by as well as transitions in the scalar leptoquark (LQ) model, where the LQs have the representation (3, 2, 7/6) and (3, 2, 1/6) under the standard model gauge group. The LQ parameter space is constrained using the most recent experimental results on and processes. Considering only the baryon number conserving LQ interactions, we estimate the branching ratios for the exclusive and inclusive decay processes by using the constraint parameters. We also obtain the low recoil (large lepton invariant mass, i.e., ) predictions for the angular distribution of process and several other observables including the flat term and lepton flavour non-universality factor in this model.

Leptoquark effects on and decay processes

We compute direct current thermoelectric transport coefficients in strongly coupled quantum field theories without long lived quasiparticles, at finite temperature and charge density, and disordered on long wavelengths compared to the length scale of local thermalization. Many previous transport computations in strongly coupled systems are interpretable hydrodynamically, despite formally going beyond the hydrodynamic regime. This includes momentum relaxation times previously derived by the memory matrix formalism, and non-perturbative holographic results; in the latter case, this is subject to some important subtleties. Our formalism may extend some memory matrix computations to higher orders in the perturbative disorder strength, as well as give valuable insight into non-perturbative regimes. Strongly coupled metals with quantum critical contributions to transport generically transition between coherent and incoherent metals as disorder strength is increased at fixed temperature, analogous to mean field holographic treatments of disorder. From a condensed matter perspective, our theory generalizes the resistor network approximation, and associated variational techniques, to strongly interacting systems where momentum is long lived.

Hydrodynamic transport in strongly coupled disordered quantum field theories

Neutrino oscillations have become well-known phenomena; the measurements of neutrino mixing angles and mass squared differences are continuously improving. Future oscillation experiments will eventually determine the remaining unknown neutrino parameters, namely, the mass ordering, normal or inverted, and the CP-violating phase. On the other hand, the absolute mass scale of neutrinos could be probed by cosmological observations, single beta decay as well as by neutrinoless double beta decay experiments. Furthermore, the last one may shed light on the nature of neutrinos, Dirac or Majorana, by measuring the effective Majorana mass of neutrinos. However, the neutrino mass generation mechanism remains unknown. A well-motivated phenomenological approach to search for new physics, in the neutrino sector, is that of non-standard interactions. In this short review, the current constraints in this picture, as well as the perspectives from future experiments, are discussed.

Mexico

Non standard neutrino interactions: current status and future prospects