Mielczarek J.,National Center for Nuclear Research
Springer Proceedings in Physics | Year: 2014
TheWick rotation is commonly considered only as a useful computational trick. However, as suggested by Hartle and Hawking already in early eighties, Wick rotation may gain physical meaning at the Planck epoch. While such possibility is conceptually interesting, leading to no-boundary proposal, mechanism behind the signature change remains mysterious.We show that the signature change anticipated by Hartle and Hawking naturally appears in loop quantum cosmology. Theory of cosmological perturbations with the effects of quantum holonomies is discussed. It was shown by Cailleteau et al.  that this theory can be uniquely formulated in an anomaly-free manner. The obtained algebra of effective constraints turns out to be modified so that the metric signature is changing from Lorentzian in low curvature regime to Euclidean in high curvature regime. Implications of this phenomenon on propagation of cosmological perturbations are discussed and corrections to inflationary power spectra of scalar and tensor perturbations are derived. Possible relations with other approaches to quantum gravity are outlined. We also propose an intuitive explanation of the observed signature change using analogy with spontaneous symmetry breaking in “wired” metamaterials. © Springer International Publishing Switzerland 2014.
Wong C.-Y.,Oak Ridge National Laboratory |
Wilk G.,National Center for Nuclear Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013
Phenomenological Tsallis fits to the CMS, ATLAS, and ALICE transverse momentum spectra of hadrons for pp collisions at LHC were recently found to extend over a large range of the transverse momentum. We investigate whether the few degrees of freedom in the Tsallis parametrization may arise from the relativistic parton-parton hard-scattering and related processes. The effects of the multiple hard-scattering and parton showering processes on the power law are discussed. We find empirically that whereas the transverse spectra of both hadrons and jets exhibit power-law behavior of 1/pTn at high pT, the power indices n for hadrons are systematically greater than those for jets, for which n∼4-5. © 2013 American Physical Society.
Pire B.,Ecole Polytechnique - Palaiseau |
Szymanowski L.,National Center for Nuclear Research
Physical Review Letters | Year: 2015
We calculate the amplitude for exclusive neutrino production of a charmed meson on an unpolarized target in the collinear QCD approach, where generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions. We demonstrate that the transversity chiral odd GPDs contribute to the transverse cross section if the hard amplitude is calculated up to order mc/Q. We show how to access these GPDs through the azimuthal dependence of the νN→μ-D+N differential cross section. © 2015 American Physical Society. © 2015 American Physical Society.
Kowalska K.,National Center for Nuclear Research
Journal of High Energy Physics | Year: 2014
We discuss the consequences of relaxing the Minimal Flavour Violation assumption in the up-squark sector on the phenomenology of SUSY models. We study the impact of the off-diagonal entries in the soft SUSY-breaking matrices on the mass of the lightest Higgs scalar and we derive the approximate analytical formulae that quantify this effect. We show that m hcan be enhanced by up to 13 - 14 GeV in the case of the phenomenological MSSM with the inverted hierarchy of masses in the squark sector and zero stop mixing, and up to 4 - 5 GeV in GUT-constrained scenarios where the magnitude of the enhancement is mitigated by renormalization group effects. We also perform a global analysis of an inverted hierarchy GFV scenario, taking into account the experimental bounds from the measurements of relic density, EW precision observables and B-physics. We show that the allowed parameter space of the model is strongly constrained by m W, sin2θ effand BR(B s→ μ +μ -), requiring m 0(3) < 1500 GeV and m 1/2< 1800 GeV, as well as a large non-zero (2,3) entry in the up-squark trilinear matrix. © 2014 The Author(s).
Wilk G.,National Center for Nuclear Research |
Wlodarczyk Z.,Jan Kochanowski University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013
Using a Tsallis nonextensive approach, we simultaneously analyze recent data obtained by the LHC ATLAS experiment on distributions of transverse momenta of jets, pTjet, together with distributions of transverse momenta of particles produced within these jets (defined relative to the jet's axis), pTrel, and their multiplicity distributions, P(N). The respective nonextensivity parameters for distributions of jets, qjet, for distributions of particles in jets, qrel and the global nonextensivity parameter obtained from P(N), qN, were then compared with nonextensivity parameters q obtained from minimum bias pp collisions at energies corresponding to the energies of these jets. The values of the corresponding nonextensivity parameters were found to be similar, strongly indicating the existence of a common mechanism behind all these processes. We tentatively identify this as a self-similarity property known to be present there and resulting in Tsallis type distributions. If confirmed, this would considerably strengthen the nonextensive Tsallis approach. © 2013 Elsevier B.V.