Time filter

Source Type

Hrycyna O.,National Center for Nuclear Research
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

In dynamical system describing evolution of universe with the flat Friedmann–Robertson–Walker symmetry filled with barotropic dust matter and non-minimally coupled scalar field with a constant potential function an invariant manifold of the de Sitter state is used to obtain exact solutions of the reduced dynamics. Using observational data coming from distant supernovae type Ia, the Hubble function H(z) measurements and information coming from the Alcock–Paczyński test we find cosmological constraints on the non-minimal coupling constant ξ between the scalar curvature and the scalar field. For all investigated models we can exclude negative values of this parameter at the 68% confidence level. We obtain constraints on the non-minimal coupling constant consistent with condition for conformal coupling of the scalar field in higher dimensional theories of gravity. © 2017 The Author(s)

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. [3] 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.

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).

Kowalska K.,National Center for Nuclear Research | Sessolo E.M.,National Center for Nuclear Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We investigate the impact of direct LHC supersymmetry searches on the parameter space of three natural scenarios in the MSSM. In the first case the spectrum consists of light top squarks, sbottoms, and Higgsino-like neutralinos, while the other particles are assumed to be out of experimental reach. In the second case we consider an additional light gluino. Finally we study a more complex spectrum comprising also light sleptons, a winolike chargino, and a binolike neutralino. We simulate in detail three LHC searches: top squark production at ATLAS with 20.7/fb, CMS 11.7/fb inclusive search for squarks and gluinos with the variable αT, and CMS 9.2/fb electroweak production with three leptons in the final state. For each point in our scans we calculate the exclusion likelihood due to the individual searches and to their statistical combination. We calculate the fine-tuning measure of the points allowed by the LHC and the implications for the Higgs mass and other phenomenological observables: Higgs signal rates, the relic density, BR(B s→μ+μ-), BR(B̄→X sγ), and the spin-independent neutralino-proton scattering cross section. We find that points with acceptable levels of fine-tuning are for the most part already excluded by the LHC and including the other constraints further reduces the overall naturalness of our scenarios. © 2013 American Physical Society.

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.

Munir S.,National Center for Nuclear Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

In the next-to-minimal supersymmetric standard model (NMSSM) a variety of parameter configurations yields a Higgs boson consistent with the one observed at the LHC. Additionally, the Higgs sector of the model can contain explicit charge parity (CP)-violating phases even at the tree level, in contrast with the minimal supersymmetric standard model (MSSM). In this article we present the one-loop Higgs boson mass matrix of the complex NMSSM in the renormalization-group-improved effective potential approach. We also present the trilinear Higgs boson self couplings as well as various partial decay widths of a generic CP-mixed Higgs boson in the model. We then analyze a very interesting phenomenological scenario wherein the decay of a relatively light pseudoscalar-like Higgs boson into ∼125GeV standard model-like Higgs boson(s) is induced by nonzero CP-violating phases. We discuss in detail a few benchmark cases in which such a decay can contribute significantly to the production of SM-like Higgs bosons at the LHC on top of the gluon fusion process. It can thus be partially responsible for the γγ excess near 125 GeV due to the subsequent decay of the SM-like Higgs boson. Such a scenario is extremely difficult to realize in the complex MSSM and, if probed at the LHC, it could provide an indication of the nonminimal nature of supersymmetry. © 2014 American Physical Society.

Szabelski A.,National Center for Nuclear Research
EPJ Web of Conferences | Year: 2015

Sivers effect for gluons is connected to gluon orbital angular momentum which may be the missing part of the nucleon spin puzzle. We present a method of extraction of Sivers effect for gluons from COMPASS SIDIS data on transversely polarised target. In order to access the Sivers effect for gluons photon-gluon fusion (PGF) process is used. To enhance the fraction of PGF in the sample high-pT hadron pair events are selected. The method is based on a assumption that there are 3 processes contributing to the muon-nucleon scattering: PGF, leading process and QCD Compton process. Then one performs a weighting procedure which enables to extract the asymmetries for the 3 contributing processes simultaneously. In order to do that a neural network trained by a Monte Carlo to assign to each event 3 probabilities corresponding to the 3 processes is needed. Finaly we show results of Sivers effect for gluons extraction on COMPASS data with transversely polarised deuteron target. APGFsinΦ2h-ΦS = -0.14 ± 0.15 (stat.) at XG = 0.126. © 2015 Owned by the authors, published by EDP Sciences.

Bomark N.-E.,National Center for Nuclear Research | Roszkowski L.,National Center for Nuclear Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Extremely weakly interacting particles like the gravitino may be stable enough on cosmological time scales to constitute a good dark matter candidate even in the presence of R-parity violation. We consider the possibility that the recently identified 3.5 keV x-ray line can be generated in light gravitino decays to neutrinos and photons. We find that this is indeed possible in loop processes induced by trilinear lepton-number-violating couplings. We show that in order to avoid overproduction of gravitinos, the reheating temperature has to be at most around 100 GeV to 1 TeV. Finally we briefly discuss associated LHC phenomenology due to a relatively light gluino and multijet/multilepton events from R-parity-violating decays of neutralinos. © 2014 American Physical Society.

Baer H.,University of Oklahoma | Choi K.-Y.,Korea Astronomy and Space Science Institute | Kim J.E.,Kyung Hee University | Roszkowski L.,National Center for Nuclear Research
Physics Reports | Year: 2015

Increasingly stringent limits from LHC searches for new physics, coupled with lack of convincing signals of weakly interacting massive particle (WIMP) in dark matter searches, have tightly constrained many realizations of the standard paradigm of thermally produced WIMPs as cold dark matter. In this article, we review more generally both thermally and non-thermally produced dark matter (DM). One may classify DM models into two broad categories: one involving bosonic coherent motion (BCM) and the other involving WIMPs. BCM and WIMP candidates need, respectively, some approximate global symmetries and almost exact discrete symmetries. Supersymmetric axion models are highly motivated since they emerge from compelling and elegant solutions to the two fine-tuning problems of the Standard Model: the strong CP problem and the gauge hierarchy problem. We review here non-thermal relics in a general setup, but we also pay particular attention to the rich cosmological properties of various aspects of mixed SUSY/axion dark matter candidates which can involve both WIMPs and BCM in an interwoven manner. We also review briefly a panoply of alternative thermal and non-thermal DM candidates. © 2014 Elsevier B.V.

Loading National Center for Nuclear Research collaborators
Loading National Center for Nuclear Research collaborators