High Energy Physics Phenomenology

R-parity conserving supersymmetric models with right-handed (RH) neutrinos are very appealing since they could naturally explain neutrino physics and also provide a good dark matter (DM) candidate such as the lightest supersymmetric particle (LSP). In this work we consider the next-to-minimal supersymmetric standard model (NMSSM) plus RH neutrino superfields, with effective Majorana masses dynamically generated at the electroweak scale (EW). We perform a scan of the relevant parameter space and study both possible DM candidates: RH sneutrino and neutralino. Especially for the case of RH sneutrino DM we analyse the intimate relation between both candidates to obtain the correct amount of relic density. Besides the well-known resonances, annihilations through scalar quartic couplings and coannihilation mechanisms with all kind of neutralinos, are crucial. Finally, we present the impact of current and future direct and indirect detection experiments on both DM candidates.

We show that dark matter can be accounted for by an axion that solves the strong CP problem, but is much lighter than usual due to aZNsymmetry. The whole mass range from the canonical QCD axion down to the ultra-light regime is allowed, with3?�N??5. This includes the first proposal of a "fuzzy dark matter" QCD axion withma??10??2eV. A novel misalignment mechanism occurs --{\it trapped misalignment}-- due to the peculiar temperature dependence of theZNaxion potential. The dark matter relic density is enhanced because the axion field undergoes two stages of oscillations: it is first trapped in the wrong minimum, which effectively delays the onset of true oscillations. Trapped misalignment is more general than the setup discussed here, and may hold whenever an extra source of Peccei-Quinn breaking appears at high temperatures. Furthermore, it will be shown that trapped misalignment can dynamically source the recently proposed kinetic misalignment mechanism. All the parameter space is within tantalizing reach of the experimental projects for the next decades. For instance, even Phase I of CASPEr-Electric could discover this axion.

Combining theb?�sμ+μ??anomaly and dark matter observables, we study the capability of LHC to test dark matter,Z??, and vector-like quark. We focus on a localU(1)Lμ??L?model with a vector-likeSU(2)Ldoublet quarkQand a complex singlet scalar whose lightest componentXIis a candidate of dark matter. After imposing relevant constraints, we find that theb?�sμ+μ??anomaly and the relic abundance of dark matter favormXI<350GeV andmZ??<450GeV formQ<2 TeV andmXR<2 TeV (the heavy partner ofmXI). The current searches for jets and missing transverse momentum at the LHC sizably reduce the mass ranges of the vector-like quark, andmQis required to be larger than 1.7 TeV. Finally, we discuss the possibility of probing these new particles at the high luminosity LHC via the QCD processpp?�DD¯orpp?�UU¯followed by the decayD?�s(b)Z??XIorU?�u(c)Z??XIand thenZ????μ+μ??. Taking a benchmark point ofmQ=1.93 TeV,mZ??=170GeV, andmXI=145 GeV, we perform a detailed Monte Carlo simulation, and find that such benchmark point can be accessible at the 14 TeV LHC with an integrated luminosity 3000 fb??.

Baryon inhomogeneities can be generated very early in the universe. These inhomogeneities then decay by particle diffusion in an expanding universe. We study the decay of these baryon inhomogeneities in the early universe using the diffusion equation in the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric. We have studied the decay starting from the electroweak phase transition. We calculate the interaction cross section of the quarks with the neutrinos, the electrons and the muons and obtain the diffusion coefficients. The diffusion coefficients are temperature dependent. We find that the expansion of the universe causes the inhomogeneities to decay at a faster rate. We find that the baryon inhomogeneities generated at the electroweak epoch have very low amplitudes at the time of the quark hadron phase transition. So unless inhomogeneities are generated with a very high amplitude (greater than105times the background density), they will have no effect on the quark hadron phase transition. After the quark hadron phase transition, we include the interaction of the muons with the neutrons and the protons till 100 MeV. We also find that large density inhomogeneities generated during the quark hadron transition with sizes of the order of 1 km must have amplitudes greater than105times the background density to survive upto the nucleosynthesis epoch in an expanding universe.

As part of the search for new physics beyond the Standard Model, we chose the determination of the Higgs boson decay width as one of the least experimentally determined values. The decay widths into the four fermions of the lightest and heaviest CP-even Higgs bosons of the THDM model were calculated, taking into account QCD and electroweak corrections in the NLO approximation. To achieve this goal, the program Monte Carlo Prophecy 4f with special scenarios of parameters, 7B1 and 5B1 were used. It was found that the decay width of the heavier CP-even Higgs boson, H differs from HSMby 1227.93 times and changes to a negative value when deviating from the standard scenarios. Scale factors k2Zand k2Wshowed the predominance of the associated with Z boson production cross section of CP-even Higgs boson over the associated with W production cross section.

We make an updated review and a systematic and comprehensive analysis of the decays of Higgs bosons in the Standard Model (SM) and its three well-defined prototype extensions such as the complex singlet extension of the SM (cxSM), the four types of two Higgs-doublet models (2HDMs) without tree-level Higgs-mediated flavor-changing neutral current (FCNC) and the minimal supersymmetric extension of the SM (MSSM). We summarize the theoretical predictions for the decay widths of the SM Higgs boson and those of Higgs bosons appearing in its extensions taking account of all possible decay modes. We incorporate them to study and analyze decay patterns of CP-even, CP-odd, and CP-mixed neutral Higgs bosons and charged ones. We put special focus on the properties of a neutral Higgs boson with mass about 125 GeV discovered at the LHC and present constraints obtained from precision analysis of it. This review is intended to be self-contained and consolidated by coherently integrating relevant physics information for studying decays of Higgs bosons in the SM and beyond.

Confinement remains one the most interesting and challenging nonperturbative phenomenon in non-Abelian gauge theories. Recent semiclassical (for SU(2)) and lattice (for QCD) studies have suggested that confinement arises from interactions of statistical ensembles of instanton-dyons with the Polyakov loop. In this work, we extend studies of semiclassical ensemble of dyons to theSU(3)Yang-Mills theory. We find that such interactions do generate the expected first-order deconfinement phase transition. The properties of the ensemble, including correlations and topological susceptibility, are studied over a range of temperatures above and belowTc. Additionally, the dyon ensemble is studied in the Yang-Mills theory containing an extra trace-deformation term. It is shown that such a term can cause the theory to remain confined and even retain the same topological observables at high temperatures.

We discuss the effect of rapid rotation on the phase diagram of hadronic matter. The energy dispersion relation is shifted by an effective chemical potential induced by rotation. This suggests that rotation should lower the critical temperature of chiral restoration, but it is still controversial how the deconfinement temperature should change as a function of angular velocity. We adopt the hadron resonance gas model as an approach free from fitting parameters. We identify the deconfinement from the thermodynamic behavior and find that rotation decreases the deconfinement temperature. We also discuss the spatial inhomogeneity of the pressure and give a semi-quantitative estimate of the moment of inertia.

In models of Asymmetric Dark Matter (ADM) the relic density is set by a particle asymmetry in an analogous manner to the baryons. Here we explore the scenario in which ADM decouples from the Standard Model thermal bath during an early period of matter domination. We first present a model independent analysis for a generic ADM candidate with s-wave annihilation cross section with fairly general assumptions regarding the origin of the early matter dominated period. We contrast our results to those from conventional ADM models which assume radiation domination during decoupling. Subsequently, we examine an explicit example of this scenario in the context of an elegant SO(10) implementation of ADM in which the matter dominated era is due to a long lived heavy right-handed neutrino. In the concluding remarks we discuss the prospects for superheavy ADM in this setting.

Parton distributions can be defined in terms of the entropy of entanglement between the spatial region probed by deep inelastic scattering (DIS) and the rest of the proton. This approach leads to a simple relationS=ln[xG(x)]between the gluon structure functionxG(x)and the entropy of the produced hadronic stateS; it is valid at sufficiently small Bjorkenx, where gluons dominate and the proton becomes a maximally entangled state.Recently, the H1 Collaboration analyzed the entropy of the hadronic state in DIS, and studied its relation to the gluon structure function; poor agreement with the predicted relation was found.Here we show that the data from the H1 Collaboration in fact agree well with the prediction based on entanglement, once two important effects are taken into account: i) because the hadron multiplicityNin the H1 measurement is not large,??/Ncorrections to the predicted relation have to be included; and ii) since the measured hadrons are mostly inthe current fragmentation region, the relevant structure function is not the gluon but the sea quark one.