Dark Energy from graviton-mediated interactions in the QCD vacuum

Adopting the hypothesis about the exact cancellation of vacuum condensates contributions to the ground state energy in particle physics to the leading order in graviton-mediated interactions, we argue that the observable cosmological constant can be dynamically induced by an uncompensated quantum gravity correction to them after the QCD phase transition epoch. To start with, we demonstrate a possible cancellation of the quark-gluon condensate contribution to the total vacuum energy density of the Universe at temperatures $T<100$ MeV without taking into account the graviton-mediated effects. In order to incorporate the latter, we then calculate the leading-order quantum correction to the classical Einstein equations due to metric fluctuations induced by the non-perturbative vacuum fluctuations of the gluon and quark fields in the quasiclassical approximation. It has been demonstrated that such a correction to the vacuum energy density has a form $\varepsilon_{\Lambda}\sim G \Lambda_{\rm QCD}^6$, where $G$ is the gravitational constant, and $\Lambda_{\rm QCD}$ is the QCD scale parameter. We analyze capabilities of this approach based on the synthesis between quantum gravity in quasiclassical approximation and theory of non-perturbative QCD vacuum for quantitative explanation of the observed Dark Energy density.Comment: 21 pages, a discussion of cosmological evolution of the \Lambda-term has been added; published versio

On a possible compensation of the QCD vacuum contribution to the Dark Energy

We suggest one of the possible ways to compensate the large negative quantum-topological QCD contribution to the vacuum energy density of the Universe by means of a positive constant contribution from a cosmological Yang-Mills field. An important role of the exact particular solution for the Yang-Mills field corresponding to the finite-time instantons is discussed. An interesting connection of the compensation mechanism to the color confinement in the framework of instanton models has been pointed out. Besides the $\Lambda_{\rm QCD}$ scale, this proposal relies on one yet free dimensionless normalisation constant which cannot be fixed by the perturbative QCD theory, and thus should be fine-tuned for the exact compensation to hold.Comment: 10 pages, typos corrected, comments on fine-tuning and QCD confinement added; published versio

Vector-like technineutron Dark Matter: is a QCD-type Technicolor ruled out by XENON100?

We continue to explore a question about the existence of a new strongly coupled dynamics above the electroweak scale. The latter has been recently realized in the simplest consistent scenario, the vector-like (or chiral-symmetric) Technicolor model based upon the gauged linear sigma-model. One of the predictions of a new strong dynamics in this model, the existence of stable vector-like technibaryon states at a TeV scale, such that the lightest neutral one could serve as a Dark Matter candidate. Here, we consider the QCD-type Technicolor with SU(3)_TC confined group and one SU(2)_W doublet of vector-like techniquarks and test this model against existing Dark Matter astrophysics data. We show that the spin-independent Dirac technineutron-nucleon cross section is by far too large and ruled out by XENON100 data. We conclude that vector-like techniquark sectors with an odd group of confinement SU(2n+1)_TC, n=1,2,... and with ordinary vector-like weak SU(2)_W interactions are excluded if the technibaryon number is conserved. We discuss a possible generic TC scenario with a technibaryon sector interacting via an extra vector SU(2)_V other than the standard weak SU(2)_W and consider immediate implications for the cosmological evolution and freeze out of heavy relic technineutrons.Comment: 30 pages, 4 figures; extra clarification and motivation for the VLTC scenario has been made; minor correction

Composite scalar Dark Matter from vector-like SU(2)SU(2) confinement

A toy-model with $SU(2)_{\rm TC}$ dynamics confined at high scales $\Lambda_{\rm TC}\gg 100$ GeV enables to construct Dirac UV completion from the original chiral multiplets predicting a vector-like nature of their weak interactions consistent with electroweak precision tests. In this work, we investigate a potential of the lightest scalar baryon-like (T-baryon) state $B^0=UD$ with mass $m_B\gtrsim 1$ TeV predicted by the simplest two-flavor vector-like confinement model as a Dark Matter (DM) candidate. We show that two different scenarios with the T-baryon relic abundance formation before and after the electroweak (EW) phase transition epoch lead to symmetric (or mixed) and asymmetric DM, respectively. Such a DM candidate evades existing direct DM detection constraints since its vector coupling to $Z$ boson absents at tree level, while one-loop gauge boson mediated contribution is shown to be vanishingly small close to the threshold. The dominating spin-independent (SI) T-baryon--nucleon scattering goes via tree-level Higgs boson exchange in the $t$-channel. The corresponding bound on the effective T-baryon--Higgs coupling has been extracted from the recent LUX data and turns out to be consistent with naive expectations from the light technipion case $m_{\tilde \pi}\ll \Lambda_{\rm TC}$. The latter provides the most stringent phenomenological constraint on strongly-coupled $SU(2)_{\rm TC}$ dynamics so far. Future prospects for direct and indirect scalar T-baryon DM searches in astrophysics as well as in collider measurements have been discussed.Comment: 17 pages, 14 figures; an extra figure added, discussion of mass splitting improved, minor corrections, conclusions unchange

Chiral-Symmetric Technicolor with Standard Model Higgs boson

Most of the traditional Technicolor-based models are known to be in a strong tension with the electroweak precision tests. We show that this serious issue is naturally cured in strongly coupled sectors with chiral-symmetric vector-like gauge interactions in the framework of gauged linear \sigma-model. We discuss possible phenomenological implications of such non-standard chiral-symmetric Technicolor scenario in its simplest formulation preserving the Standard Model (SM) Higgs mechanism. For this purpose, we assume the existence of an extra technifermion sector confined under extra SU(3)_TC at the energy scales reachable at the LHC, \Lambda_TC ~ 0.1-1 TeV, and interacting with the SM gauge bosons in a chiral-symmetric (vector-like) way. In the framework of this scenario, the SM Higgs vev acquires natural interpretation in terms of the condensate of technifermions in confinement in the nearly conformal limit. We study the influence of the lowest lying composite physical states, namely, technipions, technisigma and constituent technifermions, on the Higgs sector properties in the SM and other observables at the LHC. We found out that the predicted Higgs boson signal strengths in \gamma\gamma, vector-boson VV* and fermion ffbar decay channels can be sensitive to the new strongly-coupled dynamics and are consistent with the current SM-like Higgs boson observations in the limit of relatively small Higgs-technisigma mixing. At the same time, the chiral-symmetric Technicolor provides us with rich technipion phenomenology at the LHC, and its major implications are discussed in detail.Comment: 47 pages, 28 figures; a discussion of naturalness and quartic Higgs-TC coupling in the suggested model has been added; the version accepted to Phys. Rev.

The Large High Altitude Air Shower Observatory (LHAASO) Science White Paper

The Large High Altitude Air Shower Observatory (LHAASO) project is a new generation multi-component instrument, to be built at 4410 meters of altitude in the Sichuan province of China, with the aim to study with unprecedented sensitivity the spec trum, the composition and the anisotropy of cosmic rays in the energy range between 10$^{12}$ and 10$^{18}$ eV, as well as to act simultaneously as a wide aperture (one stereoradiant), continuously-operated gamma ray telescope in the energy range between 10$^{11}$ and $10^{15}$ eV. The experiment will be able of continuously surveying the TeV sky for steady and transient sources from 100 GeV to 1 PeV, t hus opening for the first time the 100-1000 TeV range to the direct observations of the high energy cosmic ray sources. In addition, the different observables (electronic, muonic and Cherenkov/fluorescence components) that will be measured in LHAASO will allow to investigate origin, acceleration and propagation of the radiation through a measurement of energy spec trum, elemental composition and anisotropy with unprecedented resolution. The remarkable sensitivity of LHAASO in cosmic rays physics and gamma astronomy would play a key-role in the comprehensive general program to explore the High Energy Universe. LHAASO will allow important studies of fundamental physics (such as indirect dark matter search, Lorentz invariance violation, quantum gravity) and solar and heliospheric physics. In this document we introduce the concept of LHAASO and the main science goals, providing an overview of the project.Comment: This document is a collaborative effort, 185 pages, 110 figure

Charge Asymmetry of New Stable Families in Baryon Asymmetrical Universe

The new stable fermion family, with Standard Model electroweak (EW) charges, should take part in sphaleron transitions in the early Universe before breaking of the EW symmetry. The conditions of balance between the excess of new fermions (additional generation of new superheavy U, D quarks and new E, N leptons) and baryon asymmetry, were considered at temperatures above, and below, the phase transition, using a system of equations for chemical potentials

Heavy Quark Symmetry and Fine Structure of the Spectrum of Hadronic Dark Matter

We analyze the structure of excited states of new heavy hadrons in the scenario with hadronic dark matter. Fine mass-splitting in a doublet of new mesons stipulates the existence of charged metastable heavy mesons. We describe the structure of new meson excited states in the framework of the heavy quark effective theory. Phenomenological consequences of fine and hyperfine splitting are considered in the hadronic dark matter scenario and beyond

Dark Matter in the Standard Model Extension with Singlet Quark

We analyze the possibility of hadron Dark Matter carriers consisting of singlet quark and the light standard one. It is shown that stable singlet quarks generate effects of new physics which do not contradict restrictions from precision electroweak data. The neutral and charged pseudoscalar low-lying states are interpreted as the Dark Matter particle and its mass-degenerated partner. We evaluate their masses and lifetime of the charged component and describe the potential asymptotes of low-energy interactions of these particles with nucleons and with each other. Some peculiarities of Sommerfeld enhancement effect in the annihilation process are also discussed