The European Physical Journal C

We present a next-to-leading order calculation of the cross section for the leptoproduction of large- $E_{\bot}$ hadrons and we compare our predictions with H1 data on the forward production of ${\rm\pi}^0$ . We find large higher order corrections and an important sensitivity to the renormalization and factorization scales. These large corrections are shown to arise in part from BFKL-like diagrams at the lowest order.

In supersymmetric grand unified theories, light higgsino multiplets generally exist in addition to the familiar chargino/neutralino multiplets of the minimal supersymmetric extension of the Standard Model. The new multiplets may include doubly charged states $\tilde\Delta^{\pm\pm}$ and $\tilde\delta^{\pm\pm}$ . We study the properties and the production channels of these novel higgsinos in $e^+e^-$ and $\gamma\gamma$ collisions, and investigate how their properties can be analyzed experimentally.

The $$\bar{B}\rightarrow X_s\gamma $$ branching ratio is currently measured with around $$5\%$$ accuracy. Further improvement is expected from Belle II. To match such a precision on the theoretical side, evaluation of $${\mathcal O}(\alpha _{\mathrm s}^2)$$ corrections to the partonic decay $$b \rightarrow X_s^\textrm{part}\gamma $$ are necessary, which includes the $$b \rightarrow s \gamma $$ , $$b \rightarrow s g\gamma $$ , $$b \rightarrow s gg\gamma $$ , $$b \rightarrow sq\bar{q}\gamma $$ decay channels. Here, we evaluate the unrenormalized contribution to $$b \rightarrow s \gamma $$ that stems from the interference of the photonic dipole operator $$Q_7$$ and the current–current operators $$Q_1$$ and $$Q_2$$ . Our results, obtained in the cut propagator approach at the 4-loop level, agree with those found in parallel by Fael et al. who have applied the amplitude approach at the 3-loop level. Partial results for the same quantities recently determined by Greub et al. agree with our findings, too.

We consider a generic description of interacting dynamical Dark Energy, characterized by an equation of state with a time dependent coefficient w(t), and which may interact with both radiation and matter. Without referring to any particular cosmological model, we find a differential equation which must be satisfied by w(t) and involving the function Q(t) which describes the interaction between Dark Energy and the other cosmological fluids. The relation we find represents a constraint for various models of interacting dynamical Dark Energy. In addition, an observable is proposed, depending on kinematic variables and on density parameters, which may serve as a new test for $$\Lambda $$ CDM.

In the present investigation an exact generalised model for anisotropic compact stars of embedding class 1 is sought with a general relativistic background. The generic solutions are verified by exploring different physical aspects, viz. energy conditions, mass–radius relation, stability of the models, in connection to their validity. It is observed that the model presented here for compact stars is compatible with all these physical tests and thus physically acceptable as far as the compact star candidates RXJ 1856-37, SAX J 1808.4-3658 (SS1) and SAX J 1808.4-3658 (SS2) are concerned.

We study classically splitting of two kinds of folded string solution in AdS 4×CP 3. Conserved charges of the produced fragments are computed for each case. We find interesting patterns among these conserved charges.

Markarian 421 is a high-peaked BL Lac object and it has undergone many strong outbursts since its discovery as a TeV source in 1992. Markarian 421 has been studied intensively and was observed by various Cherenkov telescope arrays ever since. The outbursts of April 2004 observed by the Whipple telescope and of February 2010 by the HESS telescopes are explained well in this work by using the photohadronic model. To account for the attenuation of these high-energy gamma-rays by the extragalactic background light (EBL), we use template EBL models. The intrinsic spectrum of each epoch is different even though the high-energy protons have almost the same spectral index. We observe that this difference in intrinsic spectra is due to the change in the spectral index of the low-energy tail of the synchrotron self Compton (SSC) photons during different epochs of flaring. Our results show that the contemporaneous multiwavelength observations, particularly in the low-energy tail region of the SSC emission of the source, are important in explaining the flaring phenomenon.