Warped brane worlds in critical gravityZhong, Yi;Chen, Feng-Wei;Xie, Qun-Ying;Liu, Yu-Xiao
doi: 10.1140/epjc/s10052-014-3185-8pmid: N/A
Abstract We investigate the brane models in arbitrary dimensional critical gravity presented in Lu and Pope (Phys Rev Lett 106:181302, 2011). For the models of the thin branes with codimension one, the Gibbons–Hawking surface term and the junction conditions are derived, with which the analytical solutions for the flat, AdS, and dS branes are obtained at the critical point of the critical gravity. It is found that all these branes are embedded in an AdS\(_{n}\) spacetime, but, in general, the effective cosmological constant \(\varLambda \) of the AdS\(_{n}\) spacetime is not equal to the naked one \(\varLambda _0\) in the critical gravity, which can be positive, zero, and negative. Another interesting result is that the brane tension can also be positive, zero, or negative, depending on the symmetry of the thin brane and the values of the parameters of the theory, which is very different from the case in general relativity. It is shown that the mass hierarchy problem can be solved in the braneworld model in the higher-derivative critical gravity. We also study the thick brane model and find analytical and numerical solutions of the flat, AdS, and dS branes. It is found that some branes will have inner structure when some parameters of the theory are larger than their critical values, which may result in resonant KK modes for some bulk matter fields. The flat branes with positive energy density and AdS branes with negative energy density are embedded in an \(n\)-dimensional AdS spacetime, while the dS branes with positive energy density are embedded in an \(n\)-dimensional Minkowski one. A preprint version of the article is available at ArXiv.
Cosmology and thermodynamics of FLRW universe with bulk viscous stiff fluidMathew, Titus K.;Aswathy, M. B.;Manoj, M.
doi: 10.1140/epjc/s10052-014-3188-5pmid: N/A
Abstract We consider a cosmological model dominated by a stiff fluid with a constant bulk viscosity. We classify all the possible cases of the universe predicted by the model and analyze the scale factor and the density as well as the curvature scalar. We find that when the dimensionless constant bulk viscous parameter is in the range \(0 < \bar{\zeta }<6\) the model begins with a big bang and makes a transition from the decelerating expansion epoch to an accelerating epoch and then tends to the de Sitter phase as \( t\rightarrow \infty \). The transition into the accelerating epoch would be in the recent past when \(4<\bar{\zeta }<6.\) For \(\bar{\zeta }>6\) the model does not have a big bang and shows an increase in the fluid density and scalar curvature as the universe expands which eventually saturates as the scale factor \(a \rightarrow \infty \) in the future. We have analyzed the model with statefinder diagnostics and find that the model is different from the \(\Lambda \)CDM model but approaches the \(\Lambda \)CDM point as \(a \rightarrow \infty \). We have also analyzed the status of the generalized second law of thermodynamics with an apparent horizon as the boundary of the universe and found that the law is generally satisfied when \(0 \le \bar{\zeta }<6\), and for \(\bar{\zeta }>6\) the law is satisfied when the scale factor is larger than a minimum value. A preprint version of the article is available at ArXiv.
Dynamics of a charged particle around a slowly rotating Kerr black hole immersed in magnetic fieldHussain, Saqib;Hussain, Ibrar;Jamil, Mubasher
doi: 10.1140/epjc/s10052-014-3210-ypmid: N/A
Abstract The dynamics of a charged particle moving around a slowly rotating Kerr black hole in the presence of an external magnetic field is investigated. We are interested in exploring the conditions under which the charged particle can escape from the gravitational field of the black hole after colliding with another particle. The escape velocity of the charged particle in the innermost stable circular orbit is calculated. The effective potential and escape velocity of the charged particle with angular momentum in the presence of the magnetic field is analyzed. This work serves as an extension of a preceding paper dealing with the Schwarzschild black hole (Zahrani et al., Phys Rev D 87:084043, 2013). A preprint version of the article is available at ArXiv.
The NUHM2 after LHC Run 1Buchmueller, O.;Cavanaugh, R.;Citron, M.;De Roeck, A.;Dolan, M. J.;Ellis, J. R.;Flächer, H.;Heinemeyer, S.;Malik, S.;Marrouche, J.;Santos, D. Martínez;Olive, K. A.;de Vries, K. J.;Weiglein, G.
doi: 10.1140/epjc/s10052-014-3212-9pmid: 25983642
Abstract We make a frequentist analysis of the parameter space of the NUHM2, in which the soft supersymmetry (SUSY)-breaking contributions to the masses of the two Higgs multiplets, \(m^2_{H_{u,d}}\), vary independently from the universal soft SUSY-breaking contributions \(m^2_0\) to the masses of squarks and sleptons. Our analysis uses the MultiNest sampling algorithm with over \(4 \times 10^8\) points to sample the NUHM2 parameter space. It includes the ATLAS and CMS Higgs mass measurements as well as the ATLAS search for supersymmetric jets + \({/\!\!E}_T\) signals using the full LHC Run 1 data, the measurements of \(\mathrm{BR}(B_s \rightarrow \mu ^+\mu ^-)\) by LHCb and CMS together with other B-physics observables, electroweak precision observables and the XENON100 and LUX searches for spin-independent dark-matter scattering. We find that the preferred regions of the NUHM2 parameter space have negative SUSY-breaking scalar masses squared at the GUT scale for squarks and sleptons, \(m_0^2 < 0\), as well as \(m^2_{H_u} < m^2_{H_d} < 0\). The tension present in the CMSSM and NUHM1 between the supersymmetric interpretation of \((g-2)_\mu \) and the absence to date of SUSY at the LHC is not significantly alleviated in the NUHM2. We find that the minimum \(\chi ^2 = 32.5\) with 21 degrees of freedom (dof) in the NUHM2, to be compared with \(\chi ^2/\mathrm{dof} = 35.0/23\) in the CMSSM, and \(\chi ^2/\mathrm{dof} = 32.7/22\) in the NUHM1. We find that the one-dimensional likelihood functions for sparticle masses and other observables are similar to those found previously in the CMSSM and NUHM1. A preprint version of the article is available at ArXiv.
Double parton interactions in $$\gamma p, \gamma A$$ γ p , γ A co ...Blok, B.;Strikman, M.
doi: 10.1140/epjc/s10052-014-3214-7pmid: N/A
Abstract We derive expressions for the differential distributions and the total cross section of the double-parton interaction in direct photon interaction with proton and nuclei. We demonstrate that in this case the cross section is more directly related to the nucleon generalized parton distribution than in the case of double-parton interactions in the proton–proton collisions. We focus on the production of two dijets each containing charm (anticharm) quarks and carrying \(x_1,x_2>0.2\) fractions of the photon momentum. Numerical results are presented for the \(e\)–\(p\) collisions at LHeC, HERA, and for the ultraperipheral \(AA\) and \(pA\) collisions at the LHC. We find that the events of this kind would be abundantly produced at the LHeC. For \(\sqrt{s}=1.3\) TeV the expected rate is \(2\times 10^9\) events for 1 year (\(10^7\) s) of running and the luminosity \(10^{34}\) cm\(^{-2}~\hbox {s}^{-1}\), for the transverse cutoff of \(p_t>5\) GeV. This would make it feasible to use these processes for the model independent determination of two parton GPDs in nucleon and in nuclei. We also find that a significant number of such double-parton interactions should be produced in \(p\)–\(Pb\) and \(Pb\)–\(Pb\) collisions at the LHC: \({\sim } 6\times 10^4\) for \(Pb\)–\(Pb\), and \({\sim } 7 \times 10^3\) for \(p\)–\(Pb\) collisions for the same transverse momentum cutoff and running time \(10^{6}~\mathrm{s}\), and in HERA where \(1.2\times 10^5\) events were produced for the integrated HERA luminosity of 1.2 fb\(^{-1}\). Further studies are necessary to identify the kinematics where these MPIs could be separated from conventional 2-to-4 multijet events. A preprint version of the article is available at ArXiv.
Squark and gluino production cross sections in $$pp$$ p p collisions at $$\sqrt{s} = 13, 14, 33$$ ...Borschensky, Christoph;Krämer, Michael;Kulesza, Anna;Mangano, Michelangelo;Padhi, Sanjay;Plehn, Tilman;Portell, Xavier
doi: 10.1140/epjc/s10052-014-3174-ypmid: 25983637
Abstract We present state-of-the-art cross section predictions for the production of supersymmetric squarks and gluinos at the upcoming LHC run with a centre-of-mass energy of \(\sqrt{s} = 13\) and \(14\) TeV, and at potential future \(pp\) colliders operating at \(\sqrt{s} = 33\) and \(100\) TeV. The results are based on calculations which include the resummation of soft-gluon emission at next-to-leading logarithmic accuracy, matched to next-to-leading order supersymmetric QCD corrections. Furthermore, we provide an estimate of the theoretical uncertainty due to the variation of the renormalisation and factorisation scales and the parton distribution functions. A preprint version of the article is available at ArXiv.
Hydrodynamics and jets in dialogueFloerchinger, Stefan;Zapp, Korinna C.
doi: 10.1140/epjc/s10052-014-3189-4pmid: N/A
Abstract Energy and momentum loss of jets in heavy ion collisions can affect the fluid dynamic evolution of the medium. We determine realistic event-by-event averages and correlation functions of the local energy-momentum transfer from hard particles to the soft sector using the jet-quenching Monte-Carlo code Jewel combined with a hydrodynamic model for the background. The expectation values for source terms due to jets in a typical (minimum-bias) event affect the fluid dynamic evolution mainly by their momentum transfer. This leads to a small increase in flow. The presence of hard jets in the event constitutes only a minor correction. A preprint version of the article is available at ArXiv.