International Journal of Modern Physics A

The second period of datataking at the Large Hadron Collider (LHC) has provided a large dataset of proton–proton collisions that is unprecedented in terms of its centre-of-mass energy of 13 TeV and integrated luminosity of almost 140 fb${}^{-1}$. These data constitute a formidable laboratory for the search for new particles predicted by models of supersymmetry. The analysis activity is still ongoing, but a host of results on supersymmetry had already been released by the general purpose LHC experiments ATLAS and CMS. In this paper, we provide a map into this remarkable body of research, which spans a multitude of experimental signatures and phenomenological scenarios. In the absence of conclusive evidence for the production of supersymmetric particles we discuss the constraints obtained in the context of various models. We finish with a short outlook on the new opportunities for the next runs that will be provided by the upgrade of detectors and accelerator.

We know that criteria for thermodynamic stability of a most general black hole appears in the form of a series of inequalities connecting second-order derivatives of the black hole mass with respect to its parameters. Quasi-stable black holes satisfy some of these stability criteria in a certain regime of parameter space, but they never satisfy all the criteria simultaneously. We also know that specific heat, by virtue of our general stability criteria, is not necessarily negative for quasi-stable black holes. We show here that ($2+1$)-dimensional charged super entropic BTZ black hole is thermodynamically quasi-stable if fluctuation in cosmological constant is taken into account. We in fact study the fluctuations of all the thermodynamic parameters of this black hole in detail, namely, its charge, horizon area and cosmological constant. This detailed study concludes that this BTZ black hole transforms into some other kind of black hole during its Hawking decay and becomes stable. We also show differences in thermodynamic properties between this charged super entropic BTZ black hole and other AdS black holes.

We re-examine Hawking radiation for a nonrotating $(2+1)$-dimensional Bañados–Teitelboim–Zanelli (BTZ) black hole and evaluate the transmission probability of tunneling through the barrier of the event horizon employing the standard method of WKB approximation. Our results are presented for both uncharged and charged cases. We also explore the associated thermodynamics in terms of Hawking temperature and provide estimates of black hole parameters like the surface gravity and entropy.

In earlier work, we showed how to handle the Group Theoretical issue of the Little Group for spin 1/2 tachyons by introducing a special metric in the vector space of one-particle states. Here that technique is extended to tachyons of any spin. Examining the bi-linear algebra of the generating matrices for spin 5/2, we find a complete basis for the Gell-Mann matrices that form the Lie algebra for SU(3). A Dirac-like equation is developed for tachyons of any integer-plus-one-half spin; and it shows multiple distinct mass eigenvalues. The primary model shows a mass spectrum (in the case of $j=5/2$) that roughly mimics the known data on masses of the three neutrinos; the model can be tweaked to fit that experimental data precisely.

In this paper, artificial neural network (ANN) model is used to estimate the multiplicity per rapidity for charged pions and kaons observed in various high-energy experiments from central $\mathrm{\text{Au}}+\mathrm{\text{Au}}$ heavy-ion collisions with energies ranging from 2–200 GeV, and then compared to available experimental data, including RHIC-BRAHMS experiment, and covering the energy range of the future accelerator facilities at NICA and FAIR. We also used Landau hydrodynamical approach, which has a better description for the evolution of hot and dense matter produced in ultra-relativistic heavy-ion collisions. The approach is fitted to both results estimated from experiment and ANN simulation. We noted that the Landau model accurately reproduces the entire range of multiplicity per rapidity for all created particles at all energies. Also ANN model can reproduce the multiplicity per rapidity very well for all the considered particles. This encourages us to use ANN model to predict the multiplicity per rapidity for $k^{-}$ particles at energies $12.2$ and $17.3$ GeV.

The off-shell nilpotent and absolutely anticommuting (anti-)BRST symmetries are obtained by using the (anti-)chiral superfield approach (ACSA) to Becchi–Rouet–Stora–Tyutin (BRST) formalism for the four $(3+1)$-dimensional (4D) Stückelberg-modified massive Abelian 2-form gauge theory. We perform exactly similar kind of exercise for the derivation of the off-shell nilpotent (anti-)co-BRST symmetry transformations, too. In the above derivations, the symmetry invariant restrictions on the superfields play very important and decisive roles. To prove the sanctity of the above nilpotent symmetries, we generalize our 4D ordinary theory (defined on the 4D flat Minkowskian space–time manifold) to its counterparts $(4,1)$-dimensional (anti-)chiral super-submanifolds of the $(4,2)$-dimensional supermanifold which is parametrized by the superspace coordinates $Z^M=(x^{\mu },𝜃,\overline{𝜃})$ where $x^{\mu }$ $(\mu =0,1,2,3)$ are the bosonic coordinates and a pair of Grassmannian variables $(𝜃,\overline{𝜃})$ are fermionic: ${𝜃}^2=\overline{{𝜃}^2}=0$, $𝜃\overline{𝜃}+\overline{𝜃}𝜃=0$ in nature. One of the novel observations of our present endeavor is the derivation of the Curci–Ferrari (CF)-type restrictions from the requirement of the symmetry invariance of the coupled (but equivalent) Lagrangian densities of our theory within the framework of ACSA to BRST formalism. We also exploit the standard techniques of ACSA to capture the off-shell nilpotency and absolute anticommutativity of the conserved (anti-)BRST as well as the conserved (anti-)co-BRST charges. In a subtle manner, the proof of the absolute anticommutativity of the above conserved charges also implies the existence of the appropriate CF-type restrictions on our theory. This proof is also a novel result.

Lepton Flavor Universality Violation (LFUV) in $B$ decays in both neutral $b\to s{l}^{+}{l}^{-}$ and charged $b\to cl{\bar{\nu }}_l$ processes observed in the ratios $R_{K^{(\ast )}}$ and $R_{D^{(\ast )}}$ is investigated in the framework of a model based on the extended symmetry gauge $SU{(3)}_C\otimes SU{(3)}_L\otimes U{(1)}_X$ whose leptonic sector consists of five triplets. It is shown that in order to explain the experimentally observed deviations from the Standard Model in these flavor changing transitions, a nonminimal version of the model has to be considered. We investigate the ability of this model in accommodating the model-independent scenarios currently favored by global fits.