High Energy Physics Phenomenology

We examine a real electroweak triplet scalar field as dark matter, abandoning the requirement that its relic abundance is determined through freeze out in a standard cosmological history (a situation which we refer to as a 'miracle-less WIMP'). We extract the bounds on such a particle from collider searches, searches for direct scattering with terrestrial targets, and searches for the indirect products of annihilation. Each type of search provides complementary information, and each is most effective in a different region of parameter space. LHC searches tend to be highly dependent on the mass of the SU(2) charged partner state, and are effective for very large or very tiny mass splitting between it and the neutral dark matter component. Direct searches are very effective at bounding the Higgs portal coupling, but ineffective once it falls belowλeff??10??. Indirect searches suffer from large astrophysical uncertainties due to the backgrounds andJ-factors, but do provide key information for??100 GeV to TeV masses. Synthesizing the allowed parameter space, this example of WIMP dark matter remains viable, but only in miracle-less regimes.

We make a systematic study of the isospin symmetry of fragmentation functions by taking decay contributions into account. We assume the isospin symmetry in strong interactions and show that in the unpolarized case the isospin symmetry is held for fragmentation functions of?and only tiny violations are allowed for other hadrons such as nucleon and pions due to the contributions from weak decays. We present a rough estimate of the magnitudes of such violations. In the polarized case, we show that the isospin symmetry violation for?production should be tiny and the recent Belle data on the transverse polarization of?can be reproduced if the isospin symmetry is kept in the corresponding polarized fragmentation functions.

Comprehensive understanding of medium-induced radiative energy loss is of a paramount importance in describing observed jet quenching in heavy-ion collisions. In this work, we have calculated the medium-modified gluon splitting rates for different profiles of the expanding partonic medium, namely profiles for static, exponential, and Bjorken expanding medium. Here in this study, we have used the Baier-Dokshitzer-Mueller-Peigne-Schiff-Zakharov (BDMPSZ) formalism for multiple soft scatterings with a time-dependent transport coefficient for characterizing the expanding medium. Using the kinetic rate equation, we have numerically evaluated the distribution of the medium evolved gluon spectra for different medium profiles. We have presented a calculation of the jetQAAwhich quantifies a sensitivity of the inclusive jet suppression on the way how the medium expands. Comparisons of predicted jetQAAwith experimental data from the LHC are also presented.

In this paper, an approach for neutral Higgs bosons search is described based on 2HDM type-I at electron-positron linear colliders operating ats??=1TeV. The beam is assumed to be unpolarized and fast detector simulation is included. The signal process produces a fully hadronic final state throughe+e???�AH?�bb¯bb¯where both CP-even and CP-odd Higgs bosons (HandA) are assumed to decay to a pair ofb-jets. Several benchmark scenarios are introduced as the baseline for the analysis takingmH/Ain the range 150--300 GeV. In order to avoid Higgs boson conversionA?�ZH, Higgs boson masses are chosen withmA??mH<mZ. It is shown that with a proper kinematic correction applied on final stateb-jet four momenta, true combinations ofb-jets can be found for simultaneous reconstruction of both Higgs bosons throughbb¯invariant mass calculation. Results show that observable signals can be achieved with statistical significance exceeding5?well before the target integrated luminosity of 8ab??.

We derive Kubo formulae for first-order spin hydrodynamics based on non-equilibrium statistical operators method. In first-order spin hydrodynamics, there are two new transport coefficients besides the ordinary ones appearing in first-order viscous hydrodynamics. They emerge due to the incorporation of the spin degree of freedom into fluids and the spin-orbital coupling. Zubarev's non-equilibrium statistical operator method can be well applied to investigate these quantum effects in fluids. The Kubo formulae, based on the method of non-equilibrium statistical operators, are related to equilibrium (imaginary-time) infrared Green's functions, and all the transport coefficients can be determined when the microscopic theory is specified.

We show how current LIGO data is able to probe interesting theories beyond the Standard Model, particularly Dark Sectors where a Dark Higgs triggers symmetry breaking via a first-order phase transition. We use publicly available LIGO O2 data to illustrate how these sectors, even if disconnected from the Standard Model, can be probed by Gravitational Wave detectors. We link the LIGO measurements with the model content and mass scale of the Dark Sector, finding that current O2 data is testing a broad set of scenarios where the breaking ofSU(N)theories withNffermions is triggered by a Dark Higgs at scales???108??109GeV with reasonable parameters for the scalar potential.

The axion is much lighter than all other degrees of freedom introduced by the Peccei-Quinn mechanism to solve the strong CP problem. It is therefore natural to use an effective field theory (EFT) to describe its interactions. Loop processes calculated in the EFT may, however, explicitly depend on the ultraviolet cutoff. In general the UV cutoff is not uniquely defined, but the dimensionful couplings suggest to identify it with the Peccei-Quinn symmetry-breaking scale. An example areK?�π+adecays that will soon be tested to improved precision in NA62 and KOTO and whose amplitude is dominated by the term logarithmically dependent on the cutoff. In this paper, we critically examine the adequacy of using such a naive EFT approach to study loop processes by comparing EFT calculations with ones performed in complete QCD axion models. In DFSZ models, for example, the cutoff is found to be set by additional Higgs degrees of freedom and to therefore be much closer to the electroweak scale than to the Peccei-Quinn scale. In fact, there are non-trivial requirements on axion models where the cutoff scale of loop processes is close to the Peccei-Quinn scale, such that the naive EFT result is reproduced. This suggests that the existence of a suitable UV embedding may impose restrictions on axion EFTs. We provide an explicit construction of a model with suitable fermion couplings and find promising prospects for NA62 and IAXO.

We present the complete set of leading-color two-loop contributions required to obtain next-to-next-to-leading-order (NNLO) QCD corrections to three-jet production at hadron colliders. We obtain analytic expressions for a generating set of finite remainders, valid in the physical region for three-jet production. The analytic continuation of the known Euclidean-region results is determined from a small set of numerical evaluations of the amplitudes. We obtain analytic expressions that are suitable for phenomenological applications and we present a C++ library for their efficient and stable numerical evaluation.

We have explored an extended seesaw model accommodating a keV sterile neutrino adoptingU(1)B?�Lsymmetry. This model provides a natural platform for achieving resonant leptogenesis to account for the observed baryon asymmetry of the Universe. The required lepton asymmetry is sourced by the CP violating decay of the lightest heavy right handed neutrino to Standard Model leptons and Higgs. The presence of the light sterile neutrino in the model brings out an enhancement in the final lepton asymmetry through an additional self-energy contribution. Adopting a proper treatment for all the washout processes this framework strictly favours a strong washout regime thereby protecting the low energy neutrino mass parameters in agreement with the present neutrino and cosmology data. This framework of extended seesaw scheme offers the source of matter-antimatter asymmetry without any severe fine tuning of the Yukawa couplings governing the tiny neutrino mass. We also comment on the half-life period for the neutrino less double beta decay process in the background of having a keV sterile neutrino satisfying all the constraints which guide the explanation for the observed baryon asymmetry of the Universe.

We study the effect of non-universalZ??boson on the rare leptonic decay modes ofB??smesons, mediated bybarrowsllquark transition. Rare B decays are sensitive to various new physics operators. As B mesons are composite particles, such decay modes of the excited states are ideal for probing new physics beyond the standard model. We have constrained our model parameters fromB(s,d)??{B bar(s,d)}mixingdatatopredicttheleptonpolarizationasymmetryofB_(s,d)^*arrow{\mu}^+ {\mu}^-channel.ItisfoundthatthisasymmetrydeviatesfromitsSMpredictionalongwiththeZ'$effect