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Register a new userConstraints on long-lived, higher-spin particles from galaxy bispectrum
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Added by
Azadeh Moradinezhad Dizgah
Publication date
2018
fields
Physics
and research's language is
English
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The presence of massive particles with spin during inflation induces distinct signatures on correlation functions of primordial curvature fluctuations. In particular, the bispectrum of primordial perturbations obtains an angular dependence determined by the spin of the particle, which can be used to set constraints on the presence of such particles. If these particles are long-lived on super-Hubble scales, as is the case for example for partially massless particles, their imprint on correlation functions of curvature perturbations would be unsuppressed. In this paper, we make a forecast for how well such angular dependence can be constrained by the upcoming EUCLID spectroscopic survey via the measurement of galaxy bispectrum.
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We investigate anomalous strong lens systems, particularly the effects of weak lensing by structures in the line of sight, in models with long-lived electrically charged massive particles (CHAMPs). In such models, matter density perturbations are suppressed through the acoustic damping and the flux ratio of lens systems are impacted, from which we can constrain the nature of CHAMPs. For this purpose, first we perform $N$-body simulations and develop a fitting formula to obtain non-linear matter power spectra in models where cold neutral dark matter and CHAMPs coexist in the early Universe. By using the observed anomalous quadruple lens samples, we obtained the constraints on the lifetime ($tau_{rm Ch}$) and the mass density fraction ($r_{rm Ch}$) of CHAMPs. We show that, for $r_{rm Ch}=1$, the lifetime is bounded as $tau_{rm Ch} < 0.96,$yr (95% confidence level), while a longer lifetime $tau_{rm Ch} = 10,$yr is allowed when $r_{rm Ch} < 0.5$ at the 95% confidence level. Implications of our result for particle physics models are also discussed.
Spectral distortions (SDs) of the cosmic microwave background (CMB) provide a powerful tool for studying particle physics. Here we compute the distortion signals from decaying particles that convert directly into photons at different epochs during cosmic history, focusing on injection energies $E_mathrm{inj}lesssim 20,mathrm{keV}$. We deliver a comprehensive library of SD solutions that can be used to study a wide range of particle physics scenarios. We use {tt CosmoTherm} to compute the SD signals, including effects on the ionization history and opacities of the Universe. We also consider the effect of blackbody-induced stimulated decay, which can modify the injection history significantly. Then, we use data from COBE/FIRAS and EDGES to constrain the properties of the decaying particles. We explore scenarios where these provide a dark matter (DM) candidate or constitute only a small fraction of DM. We complement the SD constraints with CMB anisotropy constraints, highlighting new effects from injections at very-low photon energies ($h ulesssim 10^{-4},mathrm{eV}$). Our model-independent constraints exhibit rich structures in the lifetime-energy domain, covering injection energies $E_mathrm{inj}simeq 10^{-10}mathrm{eV}-10mathrm{keV}$ and lifetimes $tau_Xsimeq 10^5,mathrm{s}-10^{33}mathrm{s}$. We discuss the constraints on axions and axion-like particles that convert directly into two photons, revising existing SD constraints in the literature. Our limits are competitive with other constraints for axion masses $m_a c^2gtrsim 27,mathrm{eV}$ and we find that simple estimates based on the overall energetics are generally inaccurate. Future CMB spectrometers could significantly improve the obtained constraints, thus providing an important complementary probe of early-universe particle physics.
Long-lived particles are predicted in extensions of the Standard Model that involve relatively light but very weakly interacting sectors. In this paper we consider the possibility that some of these particles are produced in atmospheric cosmic ray showers, and their decay intercepted by neutrino detectors such as IceCube or Super-Kamiokande. We present the methodology and evaluate the sensitivity of these searches in various scenarios, including extensions with heavy neutral leptons in models of massive neutrinos, models with an extra $U(1)$ gauge symmetry, and a combination of both in a $U(1)_{B-L}$ model. Our results are shown as a function of the production rate and the lifetime of the corresponding long-lived particles.
Using an effective field theory approach for higher-spin fields, we derive the interactions of colour singlet and electrically neutral particles with a spin higher than unity, concentrating on the spin-3/2, spin-2, spin-5/2 and spin-3 cases. We compute the decay rates and production cross sections in the main channels for spin-3/2 and spin-2 states at both electron-positron and hadron colliders, and identify the most promising novel experimental signatures for discovering such particles at the LHC. The discussion is qualitatively extended to the spin-5/2 and spin-3 cases. Higher-spin particles exhibit a rich phenomenology and have signatures that often resemble the ones of supersymmetric and extra-dimensional theories. To enable further studies of higher-spin particles at collider and beyond, we collect the relevant Feynman rules and other technical details.
We review important reactions in the big bang nucleosynthesis (BBN) model involving a long-lived negatively charged massive particle, $X^-$, which is much heavier than nucleons. This model can explain the observed $^7$Li abundances of metal-poor stars, and predicts a primordial $^9$Be abundance that is larger than the standard BBN prediction. In the BBN epoch, nuclei recombine with the $X^-$ particle. Because of the heavy $X^-$ mass, the atomic size of bound states $A_X$ is as small as the nuclear size. The nonresonant recombination rates are then dominated by the $d$-wave $rightarrow$ 2P transition for $^7$Li and $^{7,9}$Be. The $^7$Be destruction occurs via a recombination with the $X^-$ followed by a proton capture, and the primordial $^7$Li abundance is reduced. Also, the $^9$Be production occurs via the recombination of $^7$Li and $X^-$ followed by deuteron capture. The initial abundance and the lifetime of the $X^-$ particles are constrained from a BBN reaction network calculation. We estimate that the derived parameter region for the $^7$Li reduction is allowed in supersymmetric or Kaluza-Klein (KK) models. We find that either the selectron, smuon, KK electron or KK muon could be candidates for the $X^-$ with $m_Xsim {mathcal O}(1)$ TeV, while the stau and KK tau cannot.
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