Models of quantum gravity suggest that the vacuum should be regarded as a medium with quantum structure that may have nontrivial effects on photon propagation, including the violation of Lorentz ...invariance. Fermi Large Area Telescope (LAT) observations of gamma-ray bursts (GRBs) are sensitive probes of Lorentz invariance, via studies of energy-dependent timing shifts in their rapidly varying photon emissions. We analyze the Fermi-LAT measurements of high-energy gamma rays from GRBs with known redshifts, allowing for the possibility of energy-dependent variations in emission times at the sources as well as a possible nontrivial refractive index in vacuo for photons. We use statistical estimators based on the irregularity, kurtosis, and skewness of bursts that are relatively bright in the 100 MeV to multi-GeV energy band to constrain possible dispersion effects during propagation. We find that the energy scale characterizing a linear energy dependence of the refractive index should exceed a few×1017 GeV, and we estimate the sensitivity attainable with additional future sources to be detected by Fermi-LAT.
We conjecture that the Higgs potential can be significantly modified when it is in close proximity to the horizon of an astrophysical black hole, leading to the destabilization of the electroweak ...vacuum. In this situation, the black hole should be encompassed by a shell consisting of a “bowling substance” of the nucleating new-phase bubbles. In a binary black-hole merger, just before the coalescence, the nucleated bubbles can be prevented from falling under their seeding horizons, as they are simultaneously attracted by the gravitational potential of the companion. For a short time, the unstable vacuum will be “sandwiched” between two horizons of the binary black hole, and therefore the bubbles may collide and form micro-black holes, which are rapidly evaporated by thermal emission of Hawking radiation of all Standard Model species. This evaporation, being triggered by a gravitational wave signal from the binary black-hole merger, can manifest itself in observations of gamma rays and very-high-energy neutrinos, which makes it a perfect physics case for multi-messenger astronomical observations.
We conjecture that the Higgs potential can be significantly modified when it is in close proximity to the horizon of an astrophysical black hole, leading to the destabilization of the electroweak ...vacuum. In this situation, the black hole should be encompassed by a shell consisting of a "bowling substance" of the nucleating new phase bubbles. In a binary black hole merger, just before the coalescence, the nucleated bubbles can be prevented from falling under their seeding horizons, as they are simultaneously attracted by the gravitational potential of the companion. For a short time, the unstable vacuum will be "sandwiched" between two horizons of the binary black hole, and therefore the bubbles may collide and form micro-black holes, which will be rapidly evaporated by thermal emission of Hawking radiation of all Standard Model spices. This evaporation, being triggered by a gravitational wave signal from the binary black hole merger, can manifest itself in observations of gamma rays and very high energy neutrinos, which makes it a perfect physics case for multi-messenger astronomical observations.
Models of quantum gravity suggest that the vacuum should be regarded as a medium with quantum structure that may have non-trivial effects on photon propagation, including the violation of Lorentz ...invariance. Fermi Large Area Telescope (LAT) observations of gamma-ray bursts (GRBs) are sensitive probes of Lorentz invariance, via studies of energy-dependent timing shifts in their rapidly-varying photon emissions. In this paper we analyze the Fermi-LAT measurements of high-energy gamma rays from GRBs with known redshifts, allowing for the possibility of energy-dependent variations in emission times at the sources as well as a possible non-trivial refractive index in vacuo for photons. We use statistical estimators based on the irregularity, kurtosis and skewness of bursts that are relatively bright in the 100 MeV to multi-GeV energy band to constrain possible dispersion effects during propagation. We find that the energy scale characterizing a linear energy dependence of the refractive index should exceed a few \(\times 10^{17}\) GeV, and we estimate the sensitivity attainable with additional future sources to be detected by Fermi-LAT.
Cosmic Probes of Fundamental Physics take two primary forms: Very high energy particles (cosmic rays, neutrinos, and gamma rays) and gravitational waves. Already today, these probes give access to ...fundamental physics not available by any other means, helping elucidate the underlying theory that completes the Standard Model. The last decade has witnessed a revolution of exciting discoveries such as the detection of high-energy neutrinos and gravitational waves. The scope for major developments in the next decades is dramatic, as we detail in this report.
The cascade mass reconstruction approach was applied to simulated production of the lightest stop quark at the LHC in the cascade decay \(\tilde{g} \to \sTop \, \Top \to \tilde{\chi}_{2}^{0} \, \Top ...\, \Top \to \tilde{\ell}_{R} \, \ell \, \Top \, \Top \to \tilde{\chi}_{1}^{0} \, \ell \, \ell \, \Top \, \Top\) with top quarks decaying into hadrons. The stop quark mass was reconstructed assuming that the masses of gluino, slepton and of the two lightest neutralinos were reconstructed in advance. A data sample set for the SU3 model point containing 400k SUSY events was generated which corresponded to an integrated luminosity of about 20 \(\rm fb^{-1}\) at 14 TeV. These events were passed through the AcerDET detector simulator, which parametrized the response of a generic LHC detector. The mass of the \(\tilde{t}_{1}\) was reconstructed with a precision of about \(10\%\).
Phys.Atom.Nucl.74:90-97,2011 The cascade mass reconstruction approach was used for mass reconstruction of
the lightest stau produced at the LHC in the cascade decay $\tilde{g} \to
\tilde{b} b \to ...\tilde{\chi}_{2}^{0} b b \to \tilde{\tau}_{1} \tau b b \to
\tilde{\chi}_{1}^{0} \tau \tau b b $. The stau mass was reconstructed assuming
that masses of gluino, bottom squark and two lightest neutralinos were
reconstructed in advance.
SUSY data sample sets for the SU3 model point containing 160k events each
were generated which corresponded to an integrated luminosity of about $8 \rm
fb^{-1}$ at 14 TeV. These events were passed through the AcerDET detector
simulator, which parametrized the response of a generic LHC detector. The mass
of the $\tilde{\tau}_{1}$ was reconstructed with a precision of about 20% on
average.
A tracking detector is proposed for lepton flavor violation experiments (\(\mu \to e\) conversion, \(\mu \to e + \gamma\), \(\mu \to 3e \)) consisting of identical chambers which can be reconfigured ...to meet the requirements for all three experiments. A pattern recognition and track reconstruction procedure based on the Kalman filter technique is presented for this detector. The pattern recognition proceeds in two stages. At the first stage only hit straw tube center coordinates, without drift time information, are used to reduce the background to a manageable level. At the second stage the drift time information is incorporated and a deterministic annealing filter is applied to reach the final level of background suppression. The final track momentum reconstruction is provided by a combinatorial drop filter which is effective in hit-to-track assignment. The momentum resolution of the tracker in measuring monochromatic leptons is found to be \(\sigma_{p}\) = 0.17 and 0.26 MeV for the \(\mu \to e\) conversion and \(\mu^+ \to e^+ + \gamma\) processes, respectively. The tracker reconstruction resolution for the total scalar lepton momentum is \(\sigma_{p} = \) 0.33 MeV for the \(\mu \to 3e\) process. The obtained tracker resolutions allow an increase in sensitivity to the branching ratios for these processes by a few orders of magnitude over current experimental limits.
PDF
