The European Physical Journal C

http://link.springer.com/journal/10052

List of Papers (Total 3,248)

Resonances in positron scattering on a supercritical nucleus and spontaneous production of \(e^{+}e^{-}\) pairs

We re-examine the physics of supercritical nuclei, specially focusing on the scattering phase \(\delta _{\varkappa }\) and its dependence on the energy \(\varepsilon \) of the diving electronic level, for which we give both exact and approximate formulas. The Coulomb potential \(Z\alpha /r\) is rounded to the constant \(Z\alpha /R\) for \(r < R\). We confirm the resonant behavior ...

Weak decays of doubly heavy baryons: the \(1/2\rightarrow 1/2\) case

Very recently, the LHCb collaboration has observed in the final state \(\Lambda _c^+ K^-\pi ^+\pi ^+\) a resonant structure that is identified as the doubly charmed baryon \(\Xi _{cc}^{++}\). Inspired by this observation, we investigate the weak decays of doubly heavy baryons \(\Xi _{cc}^{++}\), \(\Xi _{cc}^{+}\), \(\Omega _{cc}^{+}\), \(\Xi _{bc}^{(\prime )+}\), \(\Xi ...

Gravitational lensing by a Horndeski black hole

In this article we study gravitational lensing by non-rotating and asymptotically flat black holes in Horndeski theory. By adopting the strong deflection limit, we calculate the deflection angle, from which we obtain the positions and the magnifications of the relativistic images. We compare our results with those corresponding to black holes in General Relativity. We analyze the ...

Unification of gauge and gravity Chern–Simons theories in 3-D space-time

Chamseddine and Mukhanov showed that gravity and gauge theories could be unified in one geometric construction provided that a metricity condition is imposed on the vielbein. In this paper we are going to show that by enlarging the gauge group we are able to unify Chern–Simons gauge theory and Chern–Simons gravity in 3-D space-time. Such a unification leads to the quantization of ...

A case study of quark-gluon discrimination at NNLL \('\) in comparison to parton showers

Predictions for our ability to distinguish quark and gluon jets vary by more than a factor of two between different parton showers. We study this problem using analytic resummed predictions for the thrust event shape up to NNLL\('\) using \(e^+e^- \rightarrow Z \rightarrow q \bar{q}\) and \(e^+e^- \rightarrow H \rightarrow gg\) as proxies for quark and gluon jets. We account for ...

Associated production of Z bosons and b-jets at the LHC in the combined \(k_T\) + collinear QCD factorization approach

We consider the production of Z bosons associated with beauty quarks at the LHC using a combined \(k_T\) + collinear QCD factorization approach, which interpolates between small x and large x physics. Our consideration is based on the off-shell gluon–gluon fusion subprocess \(g^* g^* \rightarrow Z Q\bar{Q}\) at the leading order \(\mathcal{O}(\alpha \alpha _s^2)\) (where the Z ...

Fermionic bound states in Minkowski space: light-cone singularities and structure

The Bethe–Salpeter equation for two-body bound system with spin 1/2 constituent is addressed directly in the Minkowski space. In order to accomplish this aim we use the Nakanishi integral representation of the Bethe–Salpeter amplitude and exploit the formal tool represented by the exact projection onto the null-plane. This formal step allows one (i) to deal with end-point ...

Cosmology and CPT violating neutrinos

The combination charge conjugation–parity–time reversal (CPT) is a fundamental symmetry in our current understanding of nature. As such, testing CPT violation is a strongly motivated path to explore new physics. In this paper we study CPT violation in the neutrino sector, giving for the first time a bound, for a fundamental particle, in the CPT violating particle-antiparticle ...

Scattering of decuplet baryons in chiral effective field theory

A formalism for treating the scattering of decuplet baryons in chiral effective field theory is developed. The minimal Lagrangian and potentials in leading-order SU(3) chiral effective field theory for the interactions of octet baryons (\(B\)) and decuplet baryons (\(D\)) for the transitions \(\mathrm{BB}\rightarrow \mathrm{BB}\), \(\mathrm{BB}\leftrightarrow \mathrm{DB}\), ...

New cosmological constraints with extended-Baryon Oscillation Spectroscopic Survey DR14 quasar sample

We update the constraints on the cosmological parameters by adopting the Planck data released in 2015 and baryon acoustic oscillation (BAO) measurements including the new DR14 quasar sample measurement at redshift \(z=1.52\), and we conclude that the six-parameter \(\Lambda \)CDM model is preferred. Exploring some extensions to the \(\Lambda \)CDM model, we find that the equation ...

Comparison of statistical sampling methods with ScannerBit, the GAMBIT scanning module

We introduce ScannerBit, the statistics and sampling module of the public, open-source global fitting framework GAMBIT. ScannerBit provides a standardised interface to different sampling algorithms, enabling the use and comparison of multiple computational methods for inferring profile likelihoods, Bayesian posteriors, and other statistical quantities. The current version offers ...

Supersymmetric and non-supersymmetric models without catastrophic Goldstone bosons

The calculation of the Higgs mass in general renormalisable field theories has been plagued by the so-called “Goldstone Boson Catastrophe,” where light (would-be) Goldstone bosons give infra-red divergent loop integrals. In supersymmetric models, previous approaches included a workaround that ameliorated the problem for most, but not all, parameter space regions; while giving ...

Total spectral distributions from Hawking radiation

Taking into account the time dependence of the Hawking temperature and finite evaporation time of the black hole, the total spectral distributions of the radiant energy and of the number of particles have been explicitly calculated and compared to their temporary (initial) blackbody counterparts (spectral exitances).

Generic calculation of two-body partial decay widths at the full one-loop level

We describe a fully generic implementation of two-body partial decay widths at the full one-loop level in the SARAH and SPheno framework compatible with most supported models. It incorporates fermionic decays to a fermion and a scalar or a gauge boson as well as scalar decays into two fermions, two gauge bosons, two scalars or a scalar and a gauge boson. We present the relevant ...

Holographic superconductor in a deformed four-dimensional STU model

In this paper, we consider a deformed STU model in four dimensions including both electric and magnetic charges. Using the AdS/CFT correspondence, we study holographic superconductors and obtain transport properties like electrical and thermal conductivities. We obtain transport properties in terms of the magnetic charge of the black hole and interpret it as the magnetic monopole ...

Energy–energy correlation in electron–positron annihilation at NNLL + NNLO accuracy

We present the computation of energy–energy correlation in \(e^+e^-\) collisions in the back-to-back region at next-to-next-to-leading logarithmic accuracy matched with the next-to-next-to-leading order perturbative prediction. We study the effect of the fixed higher-order corrections in a comparison of our results to LEP and SLC data. The next-to-next-to-leading order correction ...

Traversable Schwarzschild-like wormholes

In this paper we study relativistic static traversable wormhole solutions which are a slight generalization of Schwarzschild wormholes. In order to do this we assume a shape function with a linear dependence on the radial coordinate r. This linear shape function generates wormholes whose asymptotic spacetime is not flat: they are asymptotically locally flat, since in the asymptotic ...

On the generation of magnetostatic solutions from gravitational two-soliton solutions of a stationary mass

In the paper, magnetostatic solutions of the Einstein–Maxwell field equations are generated from the gravitational two-soliton solutions of a stationary mass. Using the soliton technique of Belinskii and Zakharov (Sov Phys JETP 48:985, 1978, Sov Phys JETP 50:1, 1979), we construct diagonal two-soliton solutions of Einstein’s gravitational field equations for an axially symmetric ...

Diphoton production in association with two bottom jets

We study the production of a photon pair in association with two bottom jets at the LHC. This process constitutes an important background to double Higgs production with the subsequent decay of the two Higgs bosons into a pair of photons and b-quarks respectively. We calculate this process at next-to-leading order accuracy in QCD and find that QCD corrections lead to a substantial ...

Measurements of the associated production of a Z boson and b jets in pp collisions at \({\sqrt{s}} = 8\,\text {TeV} \)

Measurements of the associated production of a \(\mathrm{Z}\) boson with at least one jet originating from a b quark in proton–proton collisions at \(\sqrt{s} = 8\,\text {TeV} \) are presented. Differential cross sections are measured with data collected by the CMS experiment corresponding to an integrated luminosity of 19.8\(\,\text {fb}^{-1}\). \(\mathrm{Z}\) bosons are ...

MOSCAB: a geyser-concept bubble chamber to be used in a dark matter search

The MOSCAB experiment (Materia OSCura A Bolle) uses the “geyser technique”, a variant of the superheated liquid technique of extreme simplicity. Operating principles of the new dark matter detector and technical solutions of the device are reported in detail. First results obtained in a series of test runs taken in laboratory demonstrate that we have successfully built and tested a ...

The MSSM without gluinos; an effective field theory for the stop sector

In this article we study the MSSM with stops and Higgs scalars much lighter than gluinos and squarks of the first two generations. In this setup, one should use an effective field theory with partial supersymmetry in which the gluino and heavy squarks are integrated out in order to connect SUSY parameters (given at a high scale) to observables in the stop sector. In the ...

The impact of two-loop effects on the scenario of MSSM Higgs alignment without decoupling

In multi-Higgs models, the properties of one neutral scalar state approximate those of the Standard Model (SM) Higgs boson in a limit where the corresponding scalar field is roughly aligned in field space with the scalar doublet vacuum expectation value. In a scenario of alignment without decoupling, a SM-like Higgs boson can be accompanied by additional scalar states whose masses ...

I in generalized supergravity

We showed in previous work that for homogeneous Yang–Baxter (YB) deformations of AdS\(_5\times \)S\(^5\) the open string metric and coupling and as a result the closed string density \(e^{-2 \Phi } \sqrt{g}\) remain undeformed. In this work, in addition to extending these results to the deformation associated with the modified CYBE or \(\eta \)-deformation, we identify the Page ...

Photohadronic scenario in interpreting the February–March 2014 flare of 1ES 1011+496

The extraordinary multi-TeV flare from 1ES 1011+496 during February–March 2014 was observed by the MAGIC telescopes for 17 nights and the average spectrum of the whole period has a non-trivial shape. We have used the photohadronic model and a template extragalactic background light model to explain the average spectrum which fits the flare data well. The spectral index \(\alpha \) ...