The Experts below are selected from a list of 16941 Experts worldwide ranked by ideXlab platform
Amarjit Soni - One of the best experts on this subject based on the ideXlab platform.
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Towards establishing the spin of warped Gravitons
Journal of High Energy Physics, 2008Co-Authors: Oleg Antipin, Amarjit SoniAbstract:We study the possibility of experimental verification of the spin=2 nature of the Kaluza-Klein (KK) graviton which is predicted to exist in the extra-dimensional Randal-Sundrum (RS) warped models. The couplings of these Gravitons to the particles located on or near the TeV brane is the strongest as the overlap integral of their profiles in the extra-dimension is large. Among them are unphysical Higgses ($W^{\pm}_L$ and $Z_L$) and KK excitations of the Standard Model (SM) gauge bosons. We consider the possibility to confirm the spin-2 nature of the first KK mode of the warped graviton ($G_1$) based on the angular distribution of the Z bozon in the graviton rest frame in the gg$\to G_1 \to W^{KK} (Z^{KK}) W (Z)\to WWZ$, gg$\to G_1\to ZZ$ and gg$\to G_1 \to Z^{KK} Z\to ZZH$ decay channels. Using Wigner D-matrix properties, we derive the relationship between the graviton spin, signal angular distribution peak value, and other theoretically calculable quantities. We then study the LHC signals for these decay modes and find that with 1000 fb$^{-1}$ of data, spin of the RS graviton up to $\sim$ 2 TeV may be confirmed in the $pp \to W^{KK} (Z^{KK}) W (Z) \to WWZ \to$ 3 leptons + jet + $\slashed{E}_T$ and $pp \to ZZ \to$ 4 leptons decay modes.
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warped Gravitons at the cern lhc and beyond
Physical Review D, 2007Co-Authors: Kaustubh Agashe, Hooman Davoudiasl, Gilad Perez, Amarjit SoniAbstract:We study the production and decay of Kaluza-Klein (KK) Gravitons at the CERN Large Hadron Collider (LHC), in the framework of a warped extra dimension in which the standard model (SM) fields propagate. Such a scenario can provide solutions to both the Planck-weak hierarchy problem and the flavor puzzle of the SM. In this scenario, the production via $q\overline{q}$ annihilation and decays to the conventional photon and lepton channels are highly suppressed. However, we show that graviton production via gluon fusion followed by decay to longitudinal $Z/W$ can be significant; vector boson fusion is found to be a subdominant production mode. In particular, the golden $ZZ$ decay mode offers a distinctive 4-lepton signal that could lead to the observation at the LHC with $300\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ (SLHC with $3\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$) of a KK graviton with a mass up to $\ensuremath{\sim}2$ ($\ensuremath{\sim}3$) TeV for the ratio of the ${\mathrm{AdS}}_{5}$ curvature to the Planck scale modestly above unity. We argue that (contrary to the lore) such a size of the curvature scale can still be within the regime of validity of the framework. Upgrades beyond the SLHC luminosity are required to discover Gravitons heavier than $\ensuremath{\sim}4\text{ }\text{ }\mathrm{TeV}$, as favored by the electroweak and flavor precision tests in the simplest such models.
S. Ganjour - One of the best experts on this subject based on the ideXlab platform.
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Search for high-mass diphoton resonances in proton-proton collisions at 13 TeV and combination with 8 TeV search
Physics Letters B, 2017Co-Authors: V. Khachatryan, M. Besançon, F. Couderc, M. Dejardin, D. Denegri, B. Fabbro, J.l. Faure, C. Favaro, F. Ferri, S. GanjourAbstract:A search for the resonant production of high-mass photon pairs is presented. The search focuses on spin-0 and spin-2 resonances with masses between 0.5 and 4.5 TeV, and with a width, relative to the mass, between 1.4E-4 and 5.6E-2. The data sample corresponds to an integrated luminosity of 12.9 inverse femtobarns of proton-proton collisions collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV. No significant excess is observed relative to the standard model expectation. The results of the search are combined statistically with those previously obtained in 2012 and 2015 at sqrt(s) = 8 and 13TeV, respectively, corresponding to integrated luminosities of 19.7 and 3.3 inverse femtobarns, to derive exclusion limits on scalar resonances produced through gluon-gluon fusion, and on Randall-Sundrum Gravitons. The lower mass limits for Randall-Sundrum Gravitons range from 1.95 to 4.45 TeV for coupling parameters between 0.01 and 0.2. These are the most stringent limits on Randall-Sundrum graviton production to date.
G. Ambrosi - One of the best experts on this subject based on the ideXlab platform.
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Search for Low Scale Gravity Effects in $e^+ e^-$ Collisions at LEP
Physics Letters B, 1999Co-Authors: M. Acciarri, P. Achard, O. Adriani, M. Aguilar-benitez, J. Alcaraz, G. Alemanni, J. Allaby, A. Aloisio, M G. Alviggi, G. AmbrosiAbstract:Recent theories propose that quantum gravity effects may be observable at LEP energies via Gravitons that couple to Standard Model particles and propagate into extra spatial dimensions. The associated production of a graviton and a photon is searched for as well as the effects of virtual graviton exchange in the processes: $\rm e^+e^-\rightarrow \gamma\gamma$, ZZ, $\rm W^+ W^-$, $\mu^+\mu^-$, $\tau^+\tau^-$, $\rm q \bar{q}$ and $\rm e^+e^-$. No evidence for this new interaction is found in the data sample collected by the L3 detector at LEP at centre--of--mass energies up to 183\,GeV. Limits close to 1\,TeV on the scale of this new scenario of quantum gravity are set.
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Search for Extra Dimensions in Boson and Fermion Pair Production in $e^+ e^-$ Interactions at LEP
Physics Letters B, 1999Co-Authors: M. Acciarri, P. Achard, O. Adriani, M. Aguilar-benitez, J. Alcaraz, G. Alemanni, J. Allaby, A. Aloisio, M G. Alviggi, G. AmbrosiAbstract:Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to be of the same order as the electroweak scale. A sizeable interaction between Gravitons and Standard Model particles is then predicted. Effects of these new interactions in boson and fermion pair production are searched for in the data sample collected at centre--of--mass energies above the Z pole by the L3 detector at LEP. In addition, the direct production of a graviton associated with a Z boson is investigated. No statistically significant hints for the existence of these effects are found and lower limits in excess of 1\,TeV are derived on the scale of this new theory of gravity.
Michael A. Ivanov - One of the best experts on this subject based on the ideXlab platform.
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The Graviton Background Vs. Dark Energy
viXra, 2009Co-Authors: Michael A. IvanovAbstract:In the model of low-energy quantum gravity by the author, cosmological redshifts are caused by interactions of photons with Gravitons. Non-forehead collisions with Gravitons will lead to an additional relaxation of any photonic flux. It gives a possibility of another interpretation of supernovae 1a data. Every massive body would be decelerated due to collisions with Gravitons that may be connected with the Pioneer 10 anomaly. This mechanism needs graviton pairing and "an atomic structure" of matter for working it. Also an existence of black holes contradicts to the equivalence principle: any black hole should have a gravitational mass to be much bigger - about three orders - than an inertial one.
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Gravitons as super strong interacting particles and low energy quantum gravity
arXiv: High Energy Physics - Theory, 2005Co-Authors: Michael A. IvanovAbstract:It is shown by the author that if Gravitons are super-strong interacting particles and the low-temperature graviton background exists, the basic cosmological conjecture about the Dopplerian nature of redshifts may be false. In this case, a full magnitude of cosmological redshift would be caused by interactions of photons with Gravitons. A new dimensional constant which characterizes one act of interaction is introduced and estimated. Non-forehead collisions with Gravitons will lead to a very specific additional relaxation of any photonic flux. It gives a possibility of another interpretation of supernovae 1a data - without any kinematics. Of course, all of these facts may implicate a necessity to change the standard cosmological paradigm. Some features of a new paradigm are discussed here, too. A quantum mechanism of classical gravity based on an existence of this sea of Gravitons is described for the Newtonian limit. This mechanism needs graviton pairing and "an atomic structure" of matter for working it, and leads to the time asymmetry. If the considered quantum mechanism of classical gravity is realized in the nature, than an existence of black holes contradicts to Einstein's equivalence principle. It is shown that in this approach the two fundamental constants - Hubble's and Newton's ones - should be connected between themselves. The theoretical value of the Hubble constant is computed. In this approach, every massive body would be decelerated due to collisions with Gravitons that may be connected with the Pioneer 10 anomaly. It is shown that the predicted and observed values of deceleration are in good agreement. Some unsolved problems are discussed, so as possibilities to verify some conjectures in laser-based experiments.
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May Gravitons be super-strong interacting particles?
arXiv: General Relativity and Quantum Cosmology, 2004Co-Authors: Michael A. IvanovAbstract:A scheme, in which Gravitons are super-strong interacting, is described. The graviton background with the Planckian spectrum and a small effective temperature is considered as a reservoir of Gravitons. A cross-section of interaction of a graviton with any particle is assumed to be a bilinear function of its energies. Any pair of bodies are attracting not due to an exchange with its own Gravitons, but due to a pressure of external Gravitons of this background. A graviton pairing is necessary to obtain classical gravity. Any divergencies are not possible in such the model because of natural smooth cut-offs of the graviton spectrum from both sides. Some cosmological consequences of this scheme are discussed, too. Also it is shown here that the main conjecture of this approach may be verified at present on the Earth.
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Screening the graviton background, graviton pairing, and Newtonian gravity
arXiv: General Relativity and Quantum Cosmology, 2002Co-Authors: Michael A. IvanovAbstract:It is shown that screening the background of super-strong interacting Gravitons creates for any pair of bodies as an attraction force as well an repulsion force due to pressure of Gravitons. For single Gravitons, these forces are approximately balanced, but each of them is much bigger than a force of Newtonian attraction. If single Gravitons are pairing, a body attraction force due to pressure of such graviton pairs is twice exceeding a corresponding repulsion force under the condition that graviton pairs are destructed by collisions with a body. If the considered quantum mechanism of classical gravity is realized in the nature, then an existence of black holes contradicts to Einstein's equivalence principle. In such the model, Newton's constant is proportional to $H^{2}/T^{4},$ where $H$ is the Hubble constant, $T$ is an equivalent temperature of the graviton background. The estimate of the Hubble constant is obtained $H=2.14 \cdot 10^{-18} s^{-1}$ (or $66.875 km \cdot s^{-1} \cdot Mpc^{-1}$).
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Model of graviton-dusty universe
arXiv: General Relativity and Quantum Cosmology, 2001Co-Authors: Michael A. IvanovAbstract:Primary features of a new cosmological model, which is based on conjectures about an existence of the graviton background and superstrong gravitational quantum interaction, are considered. An expansion of the universe is impossible in such the model because of deceleration of massive objects by the graviton background, which is similar to the one for the NASA deep space probes Pioneer 10, 11. Redshifts of remote objects are caused in the model by interaction of photons with the graviton background, and the Hubble constant depends on an intensity of interaction and an equivalent temperature of the graviton background. Virtual massive Gravitons would be dark matter particles. They transfer energy, lost by luminous matter radiation, which in a final stage may be collected with black holes and other massive objects.
Michele Redi - One of the best experts on this subject based on the ideXlab platform.
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Non-Pauli-Fierz Massive Gravitons
Physical review letters, 2008Co-Authors: Gia Dvali, Oriol Pujolas, Michele RediAbstract:We study general Lorentz invariant theories of massive Gravitons. We show that, contrary to the standard lore, there exist consistent theories where the graviton mass term violates Pauli-Fierz structure. For theories where the graviton is a resonance, this does not imply the existence of a scalar ghost if the deviation from a Pauli-Fierz structure becomes sufficiently small at high energies. These types of mass terms are required by any consistent realization of the Dvali-Gabadadze-Porrati model in higher dimension.
